FORMULATION
The present invention relates to the use of AB diblock copolymer micelles dispersed in an
apolar liquid medium as hydrophobic surface treatments. More specifically, the present
invention relates to the novel use of AB diblock copolymer micelles dispersed in an apolar
liquid medium and the use of compositions thereof which self assemble into aggregate
structures in a suitable medium, and to a method suitable for preparing a surface treatment
using the same which provides functional benefits associated with hydrophobic surface
treatments such as oil and/or water repellence, anti-ice and dirt-repellence properties. The
invention is equally applicable to both large surfaces and discrete objects. In addition, the
treatment of surfaces with the AB diblock copolymers according to the present invention can
yield supplementary benefits such as oleophobic, anti-bacterial or anti-fungal properties. In
particular, the present invention relates to a process for coating a surface with micelles which
comprise an AB block copolymer comprising the step of treating the surface with an apolar
liquid containing the micelles; and to surfaces coated with such micelles.
Background to the Invention
The controlled wetting of surfaces has many potential applications such as the
waterproofing of surfaces, fabrics, concrete, paints, windows and windshields. In addition,
controlled solid-liquid interfacial properties can have benefits in producing low friction
surfaces for use in areas such as swimsuits, diving gear, boats and ships, as well as microfluidic
devices. Additionally, small objects such as seeds and organic crystals can benefit
from such waterproofing/protective surface treatments. Controlled wetting can also have
implications for controlling/preventing the build-up of ice, for example on aircrafts and
refrigeration equipment.
Further applications in the area of "easy-to-clean" surfaces/coatings are also possible
{Emma Dorey, Chemistry& industry, issue 18, 5 (September 2006); Ralf Blossey, Nature
Materials, vol. 2, 301-306, (2003)}. Such surfaces are usually designed to facilitate cleaning
by minimising the adhesion of dirt and promoting water repellence such that as water "rolls
off the surface it collects the poorly adhered dirt particles {Jon Evans, Chemistry& industry,
issue 18, 16-17 (September 2006)}. Often, "self-cleaning surfaces" such as those described
in WO 96/04123 are termed "Lotus-effect" surfaces or coatings, and the technology is
termed "Lotus-Effect" technology. Such "self-cleaning surfaces" can be produced in
different ways: by creating the surface structures directly from hydrophobic polymers during
manufacture or by creating the surface structures after manufacture (specifically by
imprinting or etching, or by the adhesion of a polymer made of hydrophobic polymers to the
surfaces).
A variety of methods for controlling the wetting of surfaces have been reported,
{Mathilde Callies, David Quere, Soft matter, vol 1, 55-61, (2005); Taolei Sun, Wenlong
Song, Lei Jiang, Chem.Comm., 1723-1725, (2005)} based on both the control of the surface
chemistry and the surface morphology {S. Herminghaus, Europhys. Lett., 52, 165, (2000); J .
Bico, U. Thiele, D. Quere, Colloids Surf, A, 206, 41, (2002); H. Li, X. Wang, Y. Song, Y.
Liu, Q. Li, L. Jiang, D. Zhu, Angew. Chem. Int. Ed., 40, 1743,(2001); L. Feng, S. Li, H. Li,
J . Zhai, Y. Song, L. Jiang, D. Zhu, Angew. Chem. Int. Ed., 41, 1221, (2002); L. Feng, Y.
Song, J . Zhai, B. Liu, J . Xu, L. Jiang, D. Zhu, Angew. Chem. Int. Ed., 42, 800, (2003); T.
Onda, S. Shibuichi, N. Satoh, K. Tsujii, Langmuir, 12, 2125, (1996)}. More recently,
combinations of these two approaches have been used {Jon Evans, Chemistry& industry,
issue 18, 16-17 (September 2006); Igor Luzinov, Sergiy Minky, Vladimir V.Tsukruk,
Prog.Polym.Sci., vol 29, 635-698, (2004)}. It is known for example from basic surface
wetting theory that a low energy surface (with a concomitant large contact angle, greater
than 100°) will tend to repel water. The result will be the formation of drops that roll off the
surface easily.
US2002/0048679 (and related EP 101853 1A1) describe surfaces from which water runs
off easily as having to be either very hydrophilic or hydrophobic. Hydrophilic surfaces have
low contact angles with water, and this brings about rapid distribution of the water on the
surface and finally rapid run-off of the resultant film of water from the surface. In contrast,
hydrophobic surfaces form droplets through large contact angles with water. These droplets
can roll off rapidly from inclined surfaces.
Many materials are known to be capable of producing water repellence. In general the
materials possess a very low dielectric constant and are uncharged organics. Amongst these
are materials such as halogenated organic polymers, for example polytetrafluoroethylene
(PTFE) and derivatives thereof {Anthony M.Granville, William J.Brittain, Macromol.
Rapid.Comm., vol 25, 1298-1302, (2004; Lei Thai, Fevzi C.Cebeci, Robert E.Cohen,
Michael F.Rubner, NanoLetters, vol 4, 7, 1349-1353, (2004; Motoshi Yamanaka, Kazuki
Sada, Mikiji Miyata, Knji Hanabusa, Kazunori Nakano, Chem Comm, 2248-2250, (2006)}.
One approach for manufacturing such surfaces is to apply a thin layer of a new material with
the appropriate characteristics (for example appearance, durability, adhesion and application
requirements) directly onto the surface of interest. Such surface coatings or surface
treatments should be easily and uniformly applied; established within a reasonable amount of
time and process constraints; have a minimal environmental impact with respect to their
synthesis and application; resist the effects of environmental assault; and provide good
economic value.
The main problems with such materials to date include;
(a) Determining the best method to deposit the materials onto a surface of interest since the
materials are often soluble in a limited number of organic/volatile solvents. One possibility
is for example a spin-casting method. However, this method usually requires the liberal use
of solvents with the associated cost and environmental concerns.
(b) The durability of the coatings when applied and used in 'real applications' is an issue.
Damage of the coatings through abrasion and the impact of harsh external conditions can
compromise their efficiency. For example, re-coating can not only be difficult but also
expensive and is still subject to the same environmental concerns.
(c) Photodegradation effects caused by sunlight can also compromise the surface integrity
and lead to re-application needs.
(d) Application of such treatments can be costly and requires complex and difficult to scale
procedures during the manufacturing process.
(e) The coating of small objects (nanometre to millimetre sized), especially effective coating
of small particles such as organic crystals with a polymer is difficult to achieve. Many
techniques have been applied to coat particles, such as those based on Wurster coating
technologies for spray dry coatings wherein a fluidised bed of dry particles has a coating
solution sprayed onto the fluidised bed and solidified on the particles by either evaporation
of a volatile solvent in the coating solution or cooling to set the coating polymer (if applied
in molten form). Such techniques are notoriously variable, in that it is difficult to avoid
agglomeration of the particles into larger masses and the coating can be extremely
ineffective in coating all surfaces and edges of a particle (especially a small crystalline
particle with variable edges and sides of crystal). This limitation can be partially overcome
by employing higher quantities of coating composition but this can significantly alter the
properties of the organic particle being coated as well as having an impact on the economics
of the process and product cost. Coating of particles in a liquid medium is highly attractive if
a technique could be identified. Work with dispersions of organic pesticides in water
(WO2006/015791) in the presence of reactive monomers produced "coated" particles as
dispersions in water but these are matrix particles where the particle is engulfed in a polymer
during the polymerisation process. Many similar techniques produce such matrix particles.
Random fluorinated copolymers prepared by radical copolymerisation of monomers in
solution in a water-miscible organic solvent using peroxides or azo compounds as initiators
have been described, together with their hydrophobic and oleophobic properties on various
substrates (see, for example, EP542598, US1106630 and US2004026053).
US5,324,566 describes the use of hydrophobic fluorinated siloxane polymers for
producing water repellent surfaces and it discloses that the water repelling properties of the
fluorinated siloxane material can be improved by forming surface irregularities on the
surface of such a material. It is for example mentioned that the surface is modified with
irregularities of a height from about 0.1 micrometer up to the wavelength of visible light.
Likewise, US5,599,489 and EP0933388A2 describe how the structured surface includes
fluorine containing polymers or has been treated using alkylfluorosilanes.
US2002/0048679 describes surfaces having a smooth, extremely hydrophobic polymer
film (for example, polytetrafluoroethylene) and surfaces having a smooth extremely
hydrophilic polymer film as examples where water and dirt run off without forming droplets.
US2002/0048679 further describes how a 'long-term' hydrophobic coating may be formed
by applying certain silane derivatives underneath a hydrophobic coating on a surface. Other
self-cleaning surfaces are described in US2002/0150723, US2002/0 150724,
US2002/0150725, US2002/0 150726, US2003/00 13795 and US2003/0147932.
US3,354,022 discloses water repellent surfaces having a rough micro structure with
elevations and depressions and a hydrophobic material based on a fluorine containing
polymer. According to one embodiment, a surface with a self-cleaning effect can be applied
to ceramic, brick or glass by coating the substrate with a suspension comprising of glass
beads (diameter of 3 to 12 micrometres) and a fluorocarbon wax which is a fluoroalkyl
ethoxymethacrylate polymer. Unfortunately, such coatings have a disadvantage in that they
possess a low abrasion resistance and only a moderate self-cleaning effect.
Further developments of surface coatings that are designed to produce strongly
hydrophobic surfaces include the use of copolymers, polymer blends and mixtures of
polymers and nanoparticles (such as titanium dioxide, as described in US6800354,
US71 12621B2, US7196043 and DE10016485.4). For example, coated surfaces have been
produced using fluorocarbon polymers that can give contact angles of up to 120°. Titanium
dioxide (Ti0 2) has also been used with such fluorinated surfaces. It is known that under UV
irradiation the Ti0 2 is photocatalytically active and can produce super-wetting properties as a
result of water hydrolysis effects {Akira Nakajima, Kazuhito Hashimoto, and Toshiya
Watanabe, Langmuir, 16 (17), 7044 -7047, (2000)}. However the addition of Ti0 2 present
with (fluoroalkyl)silane does not affect the hydrophobicity of the overall material; that is, the
modified (fluoroalkyl)silane remains hydrophobic.
The preparation of such surfaces using nanoparticles suffers from several drawbacks
including the use of organic solvents (US3354022) and the use of a subsequent heat
treatment (US6800354). Thus, there is a need for a simple for producing surfaces that are
"easy-to-clean" with water and are optically transparent.
It has also been demonstrated recently that the control over surface wetting can be
improved by producing surfaces with a well-controlled micron-sized roughness {Eiji
Hosono, Shinobu Fujihara, Itaru Honma, Haoshen Zhou; JACS, vol 127, 13458-13459,
(2005); Xi Yu, Zhiqiang Wang, Yugui Jiang, Feng Shi, Xi Zhang, Adv. Mater. Vol 17, 1289-
1293, (2005); A. A. Abramzon, Khimia i Zhizu (1982), no. 11, 38 40}. These rough surface
features assist in producing 'ultrahydrophobic' substrates by physical methods that include
trapping air and reducing contact areas between the water drops and the surface. The basic
underlying surface should itself be hydrophobic and when combined with the roughness
effects, it results in surfaces with contact angles greater than 150° which are extremely
hydrophobic. However, such surfaces tend to be difficult to manufacture, they are usually
very fragile and easily damaged and the micron-scale features can cause diffraction effects
with light, which can be therefore problematic for use in applications involving glass.
Whilst many commercial surface coatings based on solutions of polymers in organic
solvents are produced by drop-casting or spin coating, alternatives that are based on chemical
grafting of polymer films have recently been discussed. Using this approach, coatings that
comprise of dense brush-like films of polymers which are chemically attached to a surface
are produced. The polymers detailed herein can have controlled chemistry that produces the
desired wettability characteristics. Furthermore, the inherent chemical variety available to
the synthetic polymer chemist means that such layers can be produced with a wide variety of
physical properties, as well as the opportunity for including a stimulus responsive surface.
Stimuli-responsive polymers {J.Rodriguez-Hernandez, F.Checot, Y.Gnanou,
S.Lecommandoux, Prog.Polym.Sci., 30, 691-724, (2005)} are polymers that are able to
respond to small changes in their environment with a corresponding large change in a
specific physical property. Typical stimuli include: temperature, pH, ionic strength, light-,
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electric- and magnetic fields. Some polymers respond to a combination of two or more of
these stimuli. For coatings or surface treatments, stimulus responsive polymers have the
potential to be used in a wide variety of applications where controlled changes in properties
such as adhesion, lubrication and wetting are required.
WO08071957 and WO10038046 describe the novel composition and/or novel use of AB
block copolymers comprising both fluorinated and non-fluorinated portions that can form
micelle structures and can be employed to surface coat structures such as fabrics, concrete
structures, glass windscreens, glass structures to render then "stay-clean" by a combination
of dust repellence and water sheeting effects. However, these compounds were used solely
in a water based formulation or mainly organic polar solvents to produce hydrophilic surface
treatments, as they offer water sheeting properties.
It has been demonstrated that although these surface treatments give some easy clean
characteristics, they lack other important functions such as water repellence and anti-ice that
may be beneficial on a wide variety of substrates. Hence, there is a need for an alternative
surface treatment which is as convenient and demonstrates such easy clean properties.
Surfactants are recognised to adsorb uniquely to interfaces such as oil/water interfaces and
solid/liquid interfaces and are employed as stabilisers to produce dispersions of particles in a
liquid medium (such as water) that remain stable to agglomeration on storage. Because of
this property of adsorbing as a monomolecular layer at an interface, surfactants in the form
of polyelectrolytes have been employed to produce layers of surfactant on a substrate such as
a solid particle. Such processes (for example, as in WO2000/077281) are slow to build-up
oppositely charged single layers of polyelectrolyte (each layer being only the thickness of a
surfactant monolayer and many layers being required to build up a coating thickness of
utility). Surfactants can also aggregate into structures containing many surfactant molecules
in a single aggregate. These aggregates are called micelles. They are commonly spherical in
shape but can have a large range of shapes and structures. The number of molecules that
compose such an aggregate can be very many, often in the order of hundreds of molecules.
Micelles can be composed of relatively simple surfactant structures but can also be
composed of high molecular weight block-copolymer surfactants. Moreover, even large
complex block copolymers can form micelles. Such block copolymer micelles, when
comprised of oppositely charged micelles, have been induced to adsorb in a layer by layer
(LbL) manner onto spherical colloidal particles to produce coatings on particles such as a
latex or a spherical silica particle (NSTI-Nanotech 2007, www.nsti.org, ISBN 1420061836
Vol. 2, 2007 ppl3-16 and Adv. Mater. 2007, 19, 247-250).
We have now unexpectedly and surprisingly found that the use of complex copolymer
micelles dispersed in an apolar liquid medium as coating agents for flat surfaces of a wide
range of substrates (and small materials such as crystalline particles) produces surface
coatings with high loadings of copolymer in a single treatment (or very few treatments) and
such products find utility in a range of applications, particularly but not limited to the
agrochemical field.
In one aspect, the present invention provides an apolar liquid comprising micelles which
themselves comprise a copolymer and in which the micellar cores are more hydrophilic than
the micelle coronas.
In another aspect, the present invention provides a surface coated with micelles which
comprise a copolymer; where the micellar cores are more hydrophilic than the micellar
coronas.
In a further aspect, the present invention provides a process for coating a surface
comprising the step of treating the surface with an apolar liquid in which micelles are
dispersed.
Examples of such small materials are objects that need to be protected from their
environment, for example water soluble organic crystals that may be otherwise incompatible
in an aqueous formulation or particles which may react with the other ingredients of the
formulation causing an increase of viscosity and decrease in the shelf life of the formulation.
Other objects may be seeds, plant tissue such as foliage, leaves, flowers or seed heads,
organic and inorganic crystals, solid particles (Ti0 2, CaC0 , Si0 2, gold, latex particles etc).
Objects that are of irregular shape and size are especially well suited to be coated by this
technology as the micelles coat all edges and corners of objects uniformly although regular
shapes such as spherical particles (latex particles, spherical silica for example) are equally
well coated.
Products of utility may be an agrochemical, laundry chemicals, cosmetics, food additives,
paint and coating additives, biocides for paints, pharmaceutical or other particles that find
utility in various fields. The novel coating, produced by micelle-forming polymers, finds
utility in a variety of ways. The coated particle can now be more effectively targeted for
adhesion to a substrate by selection of the block copolymer, as in targeting a specific
substrate in agriculture such as an insect cuticle, leaf surface or fungal pathogen or in
pharma, for delivery to a specific target organ or protection of an agent for delivery through
the mammalian stomach for selective and protected delivery later in the digestion system or
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in laundry for release of an agent at the appropriate point in the wash cycle. Moreover, the
effectively coated particles confer greater colloidal stability on systems, allowing greater and
improved stability when mixed with other components.
Further suitable applications include, without limitation:
Sustained release or controlled release usages, for example: pharma, for example acid
resistant structures (oral delivery past low pH in the stomach), protection of labile actives,
pseudo-zero order release through the micelle layer and Ostwald-ripening resistant
formulations; cosmetics; perfumes, for example slowing down evaporation of top-notes or
sustained release and minimising overpowering odours; particles having affinity for cellulose
and trapped on textile surface during laundering; flavours, for example light-stabilised to
prevent oxidation; self-healing coatings, for example particle induced to burst to release a
resin that repairs damage; carbonless copy paper; novel, double taste and texture food, for
example a particle which dissolves in the mouth and releases a new taste; pressure sensitive
adhesives; sealants; nutrition (for example increased bioavailability of complex molecules
and protection of sensitive molecules such as vitamins, probiotics and other food additives);
toner inks with photosensitivity or thermal sensitivity; textile coatings, for example, for
altering permeability properties; antifouling coatings; surface protective coatings, for
example, for improving scratch or abrasion resistance; and construction materials, for
example wall-boards, plasterboards and cements.
It is well known that chemical incompatibility between different components in liquid
laundry formulations can cause instability in these formulations. In particular, laundry
chemicals including bleaching chemicals and bleach activation agents such as, but not
limited to, sodium percarbonate and tetraacetylethylenediamme (TAED) that are widely used
in powder laundry formulations are incompatible with liquid laundry detergents. Bleach
activation agents, precursors and catalysts tend to be unstable in many liquid formulations
and although the surfactants in the liquid formulation are stable they can react with bleach or
bleach activator chemicals or catalysts or derivatives of them. One solution is to add a solid
form bleach activator as a separate dose to the liquid laundry detergent, but this is
inconvenient for the consumer. The present invention provides a means of protecting the
solid bleach activator form interaction with water and other liquid detergent components to
enable a stable liquid detergent to be formulated.
It is desirable to be able to control pH during a laundry cycle and to this end it would be
advantageous to be able to release sodium carbonate into the laundry medium at a given
point in the cycle in response to increased dilution with water. Sodium carbonate coated
with reverse micelles as described in this invention is an efficient means of achieving this.
The sustained release of biocides and anti-fouling agents is of commercial interest to the
paints and coatings industry and in particular for marine applications. One example of a
biocide that has been employed as an antifouling agent for marine use is DCOIT
(4,5-dichloro-2-n-octyl-3(2H)-isothiazolone). This active has low solubility in sea water
which is extremely desirable, however in solvents used in paint formulations such as xylene,
it is extremely soluble. This means that it is likely to react with the paint binders within the
formulation and may increase the paint viscosity or induce plasticizing of the paint.
Marine paint manufacturers will benefit from a biocide that improves in-can stability of
the paint whilst incorporating sustained release of the active after application onto the marine
vessel. The present invention provides a means of protecting the biocide from the other
active ingredients in a paint formulation and provides a means of sustained release in sea
water.
Safe delivery of active pharmaceutical ingredients (APIs) to the intended target site within
a mammalian body is a major area of both commercial unmet need and scientific research.
In many cases the API needs to be protected from interaction with its environment in order to
prevent unwanted chemical reaction or biological use of the active at the wrong site within
the body or at the wrong rate. One solution to this problem is to formulate the API into a
tablet and to add a protective or enteric coating to the tablet. This can be sub-optimal for a
number of reasons including patient preference for non-tablet formulation and the potential
risk of over-dosing [if the enteric coating fails]. The present invention enables individual
crystals of API to be coated enabling formulation into a capsule rather than a tablet and
minimizing the risk of over-dosing [as the coating would need to fail multiple times on
individually coated API crystals rather than only once on the tablet].
Non Steroidal Anti Inflammatory Drugs (NSAIDs) such as ibuprofen and diclofenac are
limited in their administration because at higher doses, side effects (such as gastric erosion,
thrombasthenia or thrombocytopenia, and fluid retention) may become severe.
Taste masking of APIs is a current target for the pharmaceutical industry as numerous
actives in the preparations are bitter or undesirable in taste. Applying a polymer coating to
the API is one approach to achieving taste masking by providing an inert coating to prevent
its dissolution. Successful taste masking can be evaluated by determining the rate of release
of the active from the coated particles.
Vitamin C is also known as ascorbic acid, ascorbate and ascorbate monoanion. It is
the enolic form of an a-ketolactone. Vitamin C works physiologically as a water soluble
antioxidant by virtue of its high reducing power. It acts as singlet oxygen quenchers, and it
is capable of regenerating vitamin E. Vitamin C is called an antioxidant because of its ability
of quenching or stabilizing free radicals that lead over time to degenerative diseases,
including cancer, cardiovascular disease and cataracts.
Ascorbic acid properties are impaired by its high reactivity, and hence, poor stability in
solution, which can result in heavy losses during food processing. It can be degraded rapidly
in the presence of oxygen in free-radical mediated oxidative processes. The processes are
strongly catalysed by transition metal ions, especially iron and cooper, leading to rapid
destruction of the ascorbate. Oxidation is also accelerated at neutral pH and above.
Destruction can occur in the presence of enzymes such as ascorbate oxidase and ascorbate
peroxidase.
The food industry may employ microencapsulation to produce foods which are more
nutritionally complete. The properties of microencapsulated nutrients will allow the food
processor greater flexibility and control in developing foods with high nutritional value.
Ascorbic acid is added extensively to many types of food products for two quite different
purposes: as a vitamin supplement to reinforce dietary intake of vitamin C, and as an
antioxidant, to protect the sensory and nutritive quality of the food itself.
The present invention enables individual crystals of ascorbic acid or other food
supplements to be coated for application in the food industry as fortification. Coated
particles could be potentially incorporated in dry form into cake mixes, puddings, gelatine
desserts, chewing gum, milk powder, jellies, pet foods, breakfast cereals, in short, into
products with low water activity.
It is therefore an object of the present invention to provide compositions that can be
deposited easily onto a substrate surface without the need for expensive processing and has
versatility that it can be applied equally well on large flat surfaces as well as contiguously to
coat objects such as seeds, plant material, inorganic or organic particles (including polymer
particles) and crystalline material such as inorganic or organic crystals.
A polymer or polymeric composition prepared according to the present invention may be
coated onto a preferred substrate by any established coating process, for example, but not
limited to for example a spray process. Methods of exposing the substrate to the solution
include for example any known technique for forming a coating from a solution such as spin
coating, dip coating, roller coating, brush coating, curtain flow or spraying, roller coating,
wire-bar coating, extrusion coating, air knife coating, curtain coating and slide coating.
More preferably dipping and spraying ensures that every part of the surface has been wetted
by the treatment composition. The treatment can be applied to both interior and exterior
surfaces.
Various surfaces may be treated including for example metals, metal alloys, glasses,
plastics, textiles, rubber, porcelain, ceramics, tile, enamelled appliances, polymers (for
example polyurethanes, polyesters, polyacrylics and polycarbonates), resins (for example
melamine/phenolic resins), painted surfaces, natural surfaces (like wood) and cellulose
substrates.
1) The metal or metal alloy object or articles may comprise a metal or metal alloy
selected from the group comprising: aluminum, magnesium, beryllium, iron, zinc, stainless
steel, nickel, nickel-cobalt, chromium, titanium, tantalum, rare earth metal, silver, gold,
platinum, tungsten, vanadium, copper, brass and bronze; and combinations or derivatives
thereof; and plated articles thereof.
2) The plastic objects or articles may comprise a polymer selected from the group
comprising: transparent or non-transparent polyurethane, polycarbonate, polyethers,
polyesters such as polyethylene terephthalate, polyvinyl chloride, polystyrene, polyethylene,
polyvinyl acetate, silicone rubbers, rubber latex, polycarbonate, cellulose esters
polycarbonate, polyester-polyether copolymers, ethylene methacrylates, polyolefms,
silicone, natural and synthetic rubbers, nylon and polyamide; and combinations thereof.
3) The glass objects or articles may comprise, at least partially, a material selected
from the group comprising: glass, such as optical glasses, optical lenses, polarizing glasses,
mirrors, optical mirrors, prisms, quartz glass and ceramics; and combinations thereof.
The substrate may include an exterior surface or article member, such as for example: a
window sash, structural member or windowpane of a building; an exterior member or
coating of a vehicle such as automobile, railway vehicle, aircraft and watercraft; an exterior
member, dust cover or coating of a machine, apparatus or article; and an exterior member or
coating of a traffic sign, various display devices and advertisement towers, that are made, for
example, of metal, plastics or glass or a combination thereof.
Examples of substrates, include, but are not limited to: medical devices, protection
shields, window sheets, windowpane, greenhouse walls, freezer doors, food packaging foils
and printing paper.
1) The metal objects can include for example: freezer doors, mirrors, condenser
pipes, ship hulls, underwater vehicles, underwater projectiles, airplanes and wind turbine
blades.
2) The plastic objects can include for example: face shields, helmet shields, swim
goggles, surgeon face shields, food packaging, plastic foil, greenhouse walls, greenhouse
roofs, mirrors, wind shields, underwater moving objects, airplane windows and shields.
3) The glass objects can include for example: window glasses, greenhouse, glasses,
glass sheets, face shields, optical glasses, optical, lenses, polarizing glasses, mirrors, optical
mirrors, prisms, quartz glass, parabolic antennas, automobile head beam light glasses,
automobile windshields, airplane control light glasses, solar panels and solar concentrator
mirrors and runway lights.
The coating may also be applied to clear plastic or glass used for example as protective
shields, windows, windshields, greenhouse panels, food packaging foils, goggles, optical
glasses and contact lenses.
Likewise the coating may be applied for example: to an exterior surface of a telescope
lens, especially a riflescope, a spotting scope, or a binocular to reduce the likelihood of
fogging or distortion due to the collection of moisture on the lens without significantly
reducing light transmission through the lens in the visible range. That is, scopes used by
sportsmen, the military and the like.
Exterior or interior parts of a building may also benefit from the coating for example:
windowpanes, toilets, baths, wash basins, lighting fixtures, kitchenware, tableware, sinks,
cooking ranges, kitchen hoods and ventilation fans, which are made from metal, glass,
ceramics, plastics, a combination thereof, a laminate thereof or other materials.
It is a further aim of the present invention to provide a novel surface treatment that promotes
variable wetting properties on the surface, or in other words provides an "easy-to-clean"
surface, meaning that an identifiable cleaning benefit ("easier-to-clean", "cleaner-longer",
"stay-clean" etc.). Examples include micelles applied to surfaces of chemical reactors to
make them easy to clean; micelles applied to the inside surfaces of pipes and tubes to make
them easy to clean; micelles applied to the surfaces of road vehicles, trains and aeroplanes to
make them easy to clean; and micelles applied to the surfaces of food packaging materials to
prevent food build up on the packaging.
It is still a further aim of the present invention to provide novel compositions that are able
to demonstrate a hydrophobic effect which is desirable for different application areas, such
as water repellence, anti-ice and water barrier properties for small objects.
It is still a further aim of the present invention to provide novel compositions that are able
to vary or reverse the water repellent properties when the local environmental conditions are
changed (such as temperature, salt concentration or pH).
The surface treatment of the present invention is hydrophobic. In the present invention,
the properties and associated benefits are achieved using simple processing and application
techniques.
Indeed the present process, composition and use invention requires the use of an AB
block copolymer composition as a surface coating wherein the composition comprises:
(a) an AB block copolymer; and
(b) a liquid medium and,
wherein the AB block copolymer comprises:
(a) a (suitably substantially hydrophobic) block A, and
(b) a (suitably substantially hydrophobic or hydrophilic) block B which has a different
affinity or solubility parameter than the block A in the liquid media;
and wherein such difference of affinity between the two blocks will lead to the formation
of micelles,
wherein the liquid medium comprises either :
(i) an organic solvent or mixture of organic or
(ii) an organic solvent substantially free from water; or
(iii two or more organic solvents: and wherein
by organic solvent it is meant an apolar solvent including oil; and the liquid medium further
optionally comprises one or more additives, surfactants or wetting agents.
Therefore, the present invention relies upon an AB block copolymer comprising two
blocks (A and B) which have different affinities for a liquid medium such that micelles form
in the liquid medium.
Although the micelles are formed in a liquid medium, any eventual coated particles may
be present not only in a liquid composition but alternatively in a dry, solid composition [for
instance, due to an evaporation step or a drying step].
A preferred AB block copolymer comprises:
(i) a first hydrophobic block A, comprising a polymer selected from the group consisting
of a homopolymer of an acrylate or alkylacrylate (preferably an acrylate or Ci_4 alkylacrylate;
more preferably an acrylate or methacrylate) monomer; a copolymer comprising two or three
different monomers selected from acrylate or alkylacrylate (preferably an acrylate or
Ci_4 alkylacrylate; more preferably an acrylate or methacrylate) monomers; a homopolymer
of a styrenic derivative monomer; a copolymer comprising two different monomers selected
from styrenic derivative monomers; a homopolymer of an alkene or diene monomer; a
copolymer comprising two different monomers selected from alkene and diene monomers; a
homopolymer of a heterocyclic monomer; a copolymer comprising two different monomers
selected from heterocyclic monomers; and a random, alternating, gradient or block
copolymer comprising monomers selected from acrylate monomers, alkylacrylate
(preferably Ci_4 alkylacrylate; more preferably methacrylate) monomers, styrenic derivative
monomers, alkene monomers, diene monomers and heterocyclic monomers; and
(ii) either a second hydrophobic block B or a hydrophilic block B having a different
affinity than the block A for the liquid medium in which the AB copolymers are dispersed
such that micelles are formed.
Throughout the discussion of the present invention, references to alkyl and alkylene
groups and moieties, relate to both straight-chained and branched versions.
Preferably any acrylate or alkylacrylate monomer is, independently, of formula A'
Formula A'
wherein R is H or a Ci to C4 alkyl chain; Z is O, a phosphorous derivative [preferably
PH3] or a nitrogen derivative [preferably NH]; R' is selected from the group comprising:
Ci to Ci8 alkyl; alkylaminoalkylene containing from 1 to 18 carbon atoms (preferably
from 2 to 18 carbon atoms); alkoxyalkylene containing from 1 to 18 carbon atoms
(preferably from 2 to 18 carbon atoms); Ci to C18 dihydroxyalkyl; Ci to C18 silylalkyl; Ci
to Ci8 epoxy alkyl; phosphoryl; phosphoryl Ci to C18 alkyl; a vinyl phosphonate or
phosphoric acid monomer; and a methacrylate having at least one crosslinkable function
or one UV or thermal-responsive unit; where each alkyl or alkylene group is,
independently, fluorinated or non-fluorinated.
Preferably any styrenic derivative monomer is, independently, of formula B'
Formula B'
wherein R is H or a Ci to C4 alkyl group; and Ri, R2, R3, R4 and R are each
independently H or a Ci to C alkyl group or a halogen atom [preferably chlorine or
fluorine].
Preferably any alkene or diene monomer is, independently, of formula Ca or Cb
Formula Ca ,
Formula Cb
wherein Rl R2, R 3 and are each independently selected from H and Ci to C4 alkyl
(preferably Ri, R3 and are each H; and R2 is H or Ci to C4 alkyl).
Preferably any heterocyclic monomer is, independently, of formula Da, Db, Dc or Dd
Formula Da Formula Db Formula Dc
Formula Dd
wherein n is from 1 to 7, m is from 0 to 5 and p is from 1 to 7; R is H or a Ci to C8 alkyl
group; and X is O, N or S.
The ratio of the monomers in each block of block copolymer AB is such that the weight
fraction of the (hydrophobic) block A and the (hydrophobic or hydrophilic) block B agents
leads to the formation of organised aggregates, such as micelles. The number of the
monomers comprising the block copolymer AB is: preferably from 5 to 250 units of A; more
preferably from 10 to 200 units of A; and most preferably from 15 to 150 units of A; and,
- 16 -
likewise, preferably from 5 to 250 units of B; more preferably from 10 to 200 units of B; and
most preferably from 15 to 150 units of B.
A suitable alkylacrylic or acrylate monomer of Formula A' is when Z is O; and R' is a Ci
to Ci8 alkyl group (more preferably a Ci to C alkyl group); another suitable monomer of
Formula A' is provided by Formula 1:
Formula 1
where n is 1 to 17, more preferably 1 to 8.
A suitable fluorinated alkylacrylic or acrylate monomer of Formula A' is when Z is O;
and R' is a fluorinated alkyl group; another suitable monomer of Formula A' is provided by
Formula 2 :
Fy)m
H F
Formula 2
where n is 1 to 6 and the chain is linear or non-linear, more preferably 1 or 2; m is 0 to 7 and
the chain is linear or non-linear, x is 0 to 2 and y is 3-x.
A suitable alkylacrylic or acrylate monomer for Formula A' is when Z is O; and R' is
an alkylaminoalkyl group containing up to eighteen carbon atoms. Another suitable
monomer of Formula A' is provided by Formula 3 :
Formula 3
where Ri and R2 are each independently H, a Ci to C alkyl group; phenyl; benzyl or
cyclohexyl; and n is from 1 to 17; more preferably, Ri and R2 are each methyl and n is from
1to 5.
A suitable alkylacrylic or acrylate monomer for Formula A' is when Z is O; and R' is an
hydroxyalkyl containing up to 18 carbon atoms. Another suitable monomer of Formula A' is
provided by Formula 4a or 4b:
x = 0 to 16 , y = (0 to 16) - x
Formula 4a Formula 4b
where n is 1to 18 and the chain is linear or non-linear (more preferably n is from 1 to 4) and
x and y are each 0 to 16, more preferably 0 to 6. Suitably, for Formula 4b, x = 0 to 16; y = 0
to 16; and x + y < 16.
A suitable alkylacrylic or acrylate monomer for Formula A' is when Z is O; and R'
comprises a dihydroxyalkyl group. Another suitable monomer of Formula A' is provided
by Formula 5a or 5b:
x =0to 17, y =(0to 17) - x x =0to 16, y =(0to 16) - x
Formula 5a Formula 5b
where x and y are each 0 to 17 in Formula 5a or 0 to 16 in Formula 5b; more preferably x
and y are each 0 to 7 in Formula 5a or 0 to 6 in Formula 5b (and the chain can be linear or
non-linear). Suitably, for Formula 5a, x = 0 to 17; y = 0 to 17; and x + y < 17. Suitably, for
Formula 5b, x = 0 to 16; y = 0 to 16; and x + y < 16.
A suitable alkylacrylic or acrylate monomer for Formula A' is when Z is O; and R' is
a Ci to Ci7 silylalkyl group. Another suitable monomer of Formula A' is provided by
Formula 6a or 6b:
x = 0 to 16, y = (0 to 16) - x
Formula 6a Formula 6b
where Ri is H or Ci to C4 alkyl and x and y are each from 0 to 16, preferably from 1 to 6.
Suitably, for Formula 6b, x = 0 to 16; y = 0 to 16; and x + y < 16.
A suitable alkylacrylic or acrylate monomer for Formula A' is when Z is O; and R' is an
epoxy alkyl group. Another suitable monomer of Formula A' is provided by Formula 7a or
7b:
Formula 7a Formula 7b
where x and y are each from 0 to 16, preferably from 0 to 6. Suitably, for Formula 7b, x = 0
to 16; y = 0 to 16; and x + y < 16.
A suitable monomer of Formula A' is when Z is O; and R' is a phosphoryl or phosphoryl
alkyl group. Another suitable monomer of Formula A' is provided by Formula 8a or 8b:
Formula 8a Formula 8b
where each Ri is independently H or Ci to C alkyl, preferably H or methyl.
Suitable monomers of Formula B' are independently selected from styrene,
a-methylstyrene, 2-methylstyrene, 4-methylstyrene, 2,4-dimethylstyrene,
2,4,6-trimethylstyrene, 4-isopropylstyrene, 2-fluorostyrene, 3-fluorostyrene, 4-fluorostyrene,
2,6-difluorostyrene, 2,3,4,5,6-pentafluorostyrene, 2-chlorostyrene, 3-chlorostyrene,
4-chlorostyrene and 2,6-dichlorostyrene and other vinyl substituted aromatics.
Suitable monomers of Formula Ca or Cb are independently selected from ethylene,
propylene, butylene, butadiene and isoprene.
Suitable monomers of Formula Da or D or Dc or D are independently selected from
ethylene oxide, propylene oxide, butylene oxide and caprolactone type monomers (such as
e-caprolactone or g -butyrolactone, lactide, oxiran-2-one, 1,3-dioxolane and caprolactam).
When the Block B is hydrophobic, it may comprise one or more monomers,
independently selected from the monomers defined above. Block B is chosen to have a
different affinity to the liquid medium to Block A. The structures outlined for Block A can
be applied for Block B provided Block A and B are different to each other.
When the block B is hydrophilic, a number of chemicals may be employed for the
hydrophilic component B, all of which need to be water-soluble; examples may be selected
from the group comprising:
hydrophilic organic monomers, oligomers, prepolymers or copolymers derived from vinyl
alcohol, N-vinylpyrrolidone, N-vinyl lactam, acrylamide, amide, styrenesulfonic acid,
combinations of vinylbutyral and N-vinylpyrrolidone, methacrylic acid, acrylic acid,
vinylmethyl ether, vinylpyridylium halide, melamine, maleic anhydride/methyl vinyl ether,
vinylpyridine, ethyleneoxide, ethyleneoxide ethylene imine, glycol, vinyl acetate, vinyl
acetate/crotonic acid, methyl cellulose, ethyl cellulose, carboxymethyl cellulose,
hydroxyethyl cellulose, hydroxypropyl cellulose, hydroxymethyl ethyl cellulose,
hydroxypropylmethyl cellulose, cellulose acetate, cellulose nitrate, hydroxyalkyl
(alkyl)acrylate such as hydroxyethyl (meth)acrylate, hydroxypropyl (meth)acrylate,
alkylaminoalkyl (alkyl)acrylate, 2-(dimethyl amino) ethyl methacrylate, 2-(diethyl amino)
ethyl methacrylate, 2-(diisopropyl amino) ethyl methacrylate, 2-(N-morpholino)ethyl
methacrylate, or a derivative thereof, ethylene glycol (meth)acrylates (for example
triethylene glycol (meth)acrylate) and (meth)acrylamide), N-alkyl (meth) acrylamides (for
example N-methyl (meth)acrylamide and N-hexyl (meth)acrylamide), N,N-dialkyl
(meth)acrylamides (for example N,N-dimethyl (meth)acrylamide and poly-N,N-dipropyl
(meth)acrylamide), N-hydroxyalkyl (meth)acrylamide polymers, such as poly-N-methylol
(meth)acrylamide and poly-N-hydroxy ethyl (meth)acrylamide, and N,N-dihydroxyalkyl
(meth)acrylamide polymers, such as poly-N,N-dihydroxyethyl (meth)acrylamide, ether
polyols, polyethylene oxide, polypropylene oxide, and poly(vinyl ether), alkylvinyl sulfones,
alkylvinylsulfone-acrylates, (alkyl)acrylate with a pendent phosphorus group such as
vinylphosphonate, vinylphosphonic acid, vinylphosphine oxide and any (alkyl)acrylate with
a ester function -COOR such as R is CxH2xP0 3R2 wherein x is 2 to 10, most preferably x is
2, and R is a hydrogen or an alkyl group having 1 to 4 carbon atoms, preferably methyl; and
related compounds or a combination thereof.
In accordance with the present invention the polymers comprising the AB block
copolymer comprise monomers, and the ratio of the monomers comprising each polymer of
the block copolymer AB is such that the weight ratio of the (hydrophobic) block A to the
(hydrophobic or hydrophilic) block B leads to the formation of organised aggregates. In
addition, the weight fraction of the (hydrophobic) block A and the (hydrophobic or
hydrophilic) block B leads to the formation of micelles. Certain copolymers used in the
present invention have been found to form complex and large micelles in solution.
As stated above AB Block copolymers can comprise a hydrophobic ("water hating") block A
and a second hydrophilic ("water loving") or two hydrophobic blocks A and B differentiated
as having different solubility parameters for a same liquid medium. Variation in the
copolymer properties can be obtained by varying the monomer types (different available
chemistries), the molecular weights of the copolymer (at a fixed ratio of the two component
block sizes) and the ratio of the molecular weights of the constituent blocks (at a fixed
overall molecular weight for the copolymer).
Importantly, to form micelles (that is, aggregates formed by molecules of block
coplymer) in an apolar liquid medium, the insoluble (or poorly soluble in the liquid medium)
blocks drive the formation of aggregates of the molecules. The structures of the aggregates
are dependent on the copolymer concentration and the exact nature of the copolymer
molecules. Schematically, micelles may be seen, for example, as a spherical aggregate
having two parts; one core composed of the copolymer block insoluble or less soluble in the
liquid medium and one corona composed of a copolymer block having affinity for the liquid
medium. Other micellar structures are possible and known to those skilled in the art.
In accordance with the present invention the polymers comprising the AB block
copolymer are comprised of monomers, and the ratio of the monomers comprising each
polymer of the block copolymer AB is such that the weight ratio of the hydrophobic block A
and the more hydrophilic block B leads to the formation of organised aggregates. In
addition, the weight fraction of the hydrophobic block A and the more hydrophilic block B
leads to the formation of micelles. The copolymers according to the present invention have
been found to form complex and large micelles in organic solution.
In the present invention, once the AB block copolymer comprises two hydrophobic
blocks A and B differentiated as having different solubility parameters for a same liquid
medium, such structures will form micelles with a corona composed of block A in a liquid
medium where the blocks B are less soluble than the blocks A in the chosen liquid medium
or micelles with a corona composed of block B in a liquid medium where the blocks A are
less soluble than the blocks B in the chosen liquid medium.
The chemistry for the micellar aggregates should be such that the micelles will
adsorb freely onto a wide variety of particle surfaces. Also, the composition may form
micelles and the aggregate structures of the composition preferably have a maximum
dimension [diameter in the case of spherical micelles] of from to 3 to 500nm, preferably
from 3 to 300nm. The block-copolymer micelle structures most preferably have a maximum
dimension [diameter in the case of spherical micelles] of from 10 to lOOnm.
In one aspect of the present invention, the micelles each comprise from 10 to 1000
copolymer molecules.
The AB block copolymer may take the form of: linear block copolymer (diblock,
triblock or multiblock), miktoarm copolymer (star copolymer), ladder (H-shaped)
copolymer, graft and comb (co)polymer; preferably a linear block copolymer.
Also, the distribution of component monomers within each copolymer block is in the
form of homo, random, gradient, alternative, block, graft and comb (co)polymers, any type
of copolymer structures which will lead to a segregation of copolymers in the liquid media as
organised aggregates.
It is also preferred that the block copolymer is preferably selected from the group
comprising: AB blocks, ABA blocks, ABC blocks copolymers.
In a preferred example, the polymers used in the composition are prepared by controlled
living radical polymerisation reactions. Preferably, the block copolymers according to the
first aspect of the present invention are prepared by means of controlled living radical
polymerisation to obtain narrow molecular weight distribution copolymers. Suitable
synthetic routes include but are not limited to: Reversible Addition - fragmentation chain
transfer (RAFT), Group transfer polymerisation (GTP) and Atomic transfer radical
polymerisation (ATRP), Activated regenerated by electron transfer (ARGET), nitroxidemediated
polymerization (NMP), ring-opening polymerization and ionic type of
polymerization and combinations of techniques where appropriate.
In a further aspect, the micelles may be crosslinkable and are optionally crosslinked
(before, during or after treating the surface with the apolar liquid containing the micelles)
resulting in a more durable coating on the substrate. In the current invention, crosslinking
can be described as the physical and/or chemical interaction between chains of the AB
diblock copolymer. The crosslinking can take place either in the core of the micelles, in the
corona of the micelles and/or between the coronas of two contiguous micelles and the
crosslinking may or may not be reversible.
Chemical crosslinking requires the use of a molecule called a crosslinker or crosslinking
reagent. Three preferred chemical crosslinking strategies are: (1) crosslinking with a
multifunctional organic compound, for example via condensation or addition reactions such
as carboxylic acids with amines, carboxylic acids with hydroxyls, hydroxyls with
isocyanates etc; (2) ring-opening reactions such as epoxy groups with amines and (3) radical
initiated crosslinking of vinyl or similar chemical functions such as those in divinyl benzene
and/or di-methacrylates, which can be introduced to the AB di-block copolymers.
A multifunctional organic compound is defined as an organic compound containing two
or more functional groups that may react with functional groups described for the AB
di-block copolymers used in this invention to form crosslinks. The functional groups in the
organic compound may be any that will react with functions described herein for the AB
di-block copolymer including but not limited to: amine, hydroxyl, carbonyls such as ketones
or aldehydes, carboxyls such as carboxylic acid, isocyanates and sulfhydryl.
Vinyl groups may be introduced to the AB di-block copolymer by using vinyl compounds
that also contain a function that will react with functional groups described in this invention
for the AB di-block copolymer. Examples of such chemistry include, but are not limited to,
amine functionalised vinyl compounds such as amino alkyl methacrylates. Following the
introduction of the vinyl chemistry, crosslinking is carried out by radical initiation via
thermal or UV curing.
Chemical covalent crosslinks are stable mechanically and thermally, so once formed
are difficult to break, whereas physical crosslinks are reversible and the physical crosslinking
process may or may not require the use of crosslinking agents. Physical crosslinking occurs
when there is the formation of a physical interaction between functional groups located
either in the AB diblock copolymer alone or between functional groups located in the AB
diblock copolymer and in the multifunctional crosslinker. Techniques include, but are not
limited to, dehydrothermal treatment, plasma treatment, hydrogen bonding, ionic interactions
and freeze thawing.
Crosslinking (physical and/or chemical) can bring many benefits including making
the hydrophilic corona of micelles more hydrophobic and controlling the release rate of an
active coated with crosslinked micelles.
In accordance with the present invention the block copolymer comprises at least one
block that adsorbs to a target surface. The composition may further comprise an adhesion
promoter. An adhesion promoter will generally consist of a polyelectrolyte of opposite
potential (charge) to the potential (charge) of the crystal; in the case the block copolymer
micelles coat which is targeted is of similar relative potential to that of the crystal to be
coated.
Also in a composition used in accordance with the present invention the apolar liquid
medium may comprise an organic solvent or mixtures of solvent, or an organic solvent free
from water, and wherein the block copolymer is preferably completely dissolved in the liquid
medium. To especially but not exclusively encourage reverse micellisation the liquid
medium employed will consist of two solvents, one a good solvent for the block-copolymer
and a second, less effective, solvent which will cause separation of the block co-polymer
from solution and the formation of micelles.
Preferred apolar solvents, can be selected from but are not limited to: alkanes, preferably
pentane and hexane; halogenated solvents, preferably dichloromethane, chloroform,
chlorobenzene and fluoroalkanes; and aromatic solvents and combinations thereof. Any
solvent used conventionally in agrochemical formulations may be suitable for use in the
present invention. Preferred apolar solvents can be also selected from what are generally
classified as oils, such as high molecular weight alkanes, for example paraffmic oil; such as
Isopar V and Exxsol D140; alimentary oil such as olive oil, soy bean oil and castor oil and
the like and combinations thereof. Conventional ester solvents are also suitable.
Preferably the ratio of the number of Block A units to the number of Block B units is
from 1:0.1 to 1:10; more preferably from 1:0.2 to 1:5; even more preferably from 1:0.25 to
1:4; yet more preferably from 1:0.5 to 1:2.
When the composition of the present invention comprises a liquid, the ratio by weight
of block copolymer to the liquid medium is preferably from 1 : 100,000 to 1 : 1 ; more
preferably from 1 : 10,000 to 1 : 2; especially from 1 : 5,000 to 1 : 5; and most preferably
from 1 : 5,000 to : 1 : 10.
It will also be appreciated by one skilled in the art that the composition according to
present invention may preferably further comprise additional components or auxiliary agents
selected from for example but not limited to dispersants, perfumes, biocides, and stabilisers,
surfactants or wetting agents, emulsifiers, colouring agents, dyes, pigments, UV absorbers,
radical scavenger, antioxidant, anti-corrosion agent, optical brightener, fluorescers, bleaches,
bleach activators, bleach catalysts, non-activated enzymes, enzyme stabilizing systems,
chelants, coating aid, metal catalyst, metal oxide catalyst, organometallic catalyst,
filmforming promoter, hardener, linking accelerator, flow agent, leveling agent, defoaming
agent, lubricant, matte particle, rheological modifier, thickener, conductive or nonconductive
metal oxide particle, magnetic particle, anti-static agent, pH control agents,
perfumes, preservative, biocide, pesticide, anti-fouling agent, algicide, bactericide,
germicides, disinfectant, fungicide, bio-effecting agent, vitamin, drug, therapeutic agent or a
combination thereof.
We have now found that these micelle structures can be conveniently employed to
coat small particulate materials such as organic crystals. The chemistry of these applications
is thereby incorporated herein. Moreover, the technique is easy to employ and permits high
coating weights to be applied over all a surface (including corners and edges of crystals if
present). The micelle structures of this invention can produce a coating thickness typically up
to 50nm in a single pass treatment-very much higher than any other known technique-while
maintaining complete stability and non-agglomeration of the coated particle. Multi-coats
produce even higher coating weights and thicknesses.
The block copolymers of the invention form micellar aggregates typically 3-300nm
in size. Aggregation number is controlled by the chemistry of the block copolymer in terms
of absolute chemistry, charge, molecular weight and the solution conditions under which the
micelle is formed. Typical aggregation numbers for such a block copolymer micelle can be
of the order of 100 molecules. Typical molecular weights of a block-copolymer of the
invention are 3 000 to 100 000 Daltons but are specified within the chemistry.
Block copolymer micelles can be simply employed by adding to a dispersion of a
particle in a carrier liquid and allowing to equilibrate. Confirmation of coating can be
obtained by SEM observation and quantitative data by analysis of a sample for total active
material content (where an active material is coated). Other techniques to induce micelle
formation (such as pH shift, temperature, solvent exchange or dilution) can all be suitably
employed. As an alternative process, a drying technique to remove either a solvent or to
induce a chemical change-such as loss of ammonia in a drying process- can be employed.
In the present invention, the block copolymer comprises at least one block that
adsorbs to a target surface. The composition may further comprise an adhesion promoter
(AP). An AP will generally consist of a polyelectrolyte of opposite potential (charge) to the
potential (charge) of the surface (crystal); in this case the block copolymer micelles coat the
AP modified surface (crystal). This allows copolymer micelles of similar potential (charge)
to the surface (crystal) to be deposited on the surface (through a surface -AP-block
copolymer arrangement).
The products of the invention comprise a surface (for example a particulate material)
covered with a coating of block copolymer micelles (including, uniquely, edges and corners
as well as faces). A key aspect of the present invention is the ability to provide good
coverage [and protection] for sharp features such as edges and, particularly, corners of
crystals.
As further embodiments, micelles comprise a core and a corona that are chemically
different. This difference can be exploited for further benefits. The micelle core can be
selectively loaded with a component that dissolves or can be dissolved by a suitable solvent
in the core chemistry. For example, the application of a photostabiliser by such a technique
(by incorporating the photostabiliser into the micelle core which is then coated onto the
crystal surface), will improve the ability to stabilise sensitive chemistry against photolytic
degradation. Soil mobility of particles of a pesticide can be similarly enhanced by coating a
stable polymer micelle onto the crystal surface (in combination with added specific
surfactants that can promoted improve soil mobility). In some situations, pesticides can
induce a phytotoxic response (in cotton for example) due to too rapid a photolytic
degradation. Coating crystals in this manner with a polymer micelle containing a
photostabiliser could reduce the rate of degradation.
In a further aspect, the ability to coat such block copolymer micelle systems onto a
substrate provides an elegant procedure to prepare mixed products by coating a polymer
micelle containing a first active onto a crystal surface of a second active (with the option of
further actives being in a dissolved or other dispersed state). Further, such coated polymer
systems could then be applied to relevant surfaces, these to include seeds or surfaces outwith
of Crop Protection uses that could require protection against attack such as wood or on
surfaces where a long lasting barrier might be required (such as to prevent ingress of
termites, ants or spiders or to prevent fungal growth in sensitive situations-eg fungicides
in/on wallboards).
Furthermore, the coated crystalline particle may be a biologically active compound
[for example, an agrochemical] whilst the micelle core may be loaded with a second
biologically active compound [for example, an agrochemical]. Alternatively two or more
different biologically active compounds [for example, agrochemicals] may be mixed
together as coated particles according to the present invention in such a manner that the
micellar coatings overcome any potential incompatibility problems [for example, physical or
chemical incompatibility].
A composition according to the present invention may suitably be an agrochemical
formulation; the agrochemical formulation may comprise an agrochemical active ingredient
(such as a fungicide, herbicide, insecticide or plant growth regulator) or it may comprise an
adjuvant which is used to enhance the bioperformance of an agrochemical [either in the same
formulation as the adjuvant or to be applied from a separate formulation]. The composition
can be in the form of a concentrate which is diluted or dispersed in a spray tank prior to use,
although ready-to-use compositions can also be made. The final dilution is usually made
with water, but can be made instead of, or in addition to, water, with, for example, liquid
fertilisers, micronutrients, biological organisms, oil or solvents. The compositions may be
chosen from a number of formulation types, many of which are known from the Manual on
Development and Use of FAO Specifications for Plant Protection Products, 5th Edition,
1999. These include dustable powders (DP), soluble powders (SP), water soluble granules
(SG), water dispersible granules (WG), wettable powders (WP), granules (GR) (slow or fast
release), dispersible concentrates (DC), suspension concentrates (SC), capsule suspensions
(CS; in which case, the particle is a microcapsule) and seed treatment formulations. The
agrochemical formulation may be used to control or combat a pest [examples of agricultural
pests include unwanted plants (weeds), insects and fungi].
In one aspect of the present invention the cores of the micelles contain a chemical [which
preferably may be a photoprotectant, a biologically active compound or an adjuvant].
In a further aspect, the ability to coat such block copolymer micelle systems onto a
substrate provides an elegant procedure to prepare mixed products by coating a polymer
micelle containing a first active onto a crystal surface of a second active (with the option of
further actives being in a dissolved or other dispersed state). Further, such coated polymer
systems could then be applied to relevant surfaces that could require protection against attack
such as wood or on surfaces where a long lasting barrier might be required (such as to
prevent ingress of termites, ants or spiders or to prevent fungal growth in sensitive situationse.
g. fungicides in/on wallboards).
Further, non-limiting crop protection applications include particle coating leading to:
reduced antagonism by altering availability between two or more actives, triggered release
potential- triggers can be pH, light, water, enzymes and alteration of release profile. These
release rate alterations may be possible not only in the products of the invention but also
when subsequently applied (for example to seeds- triggered release from seeds by coating
technology-triggers can be pH, light, water, enzymes. The size range of particles to be coated
can vary enormously. Where the particle is an organic crystal, the size range [largest
dimension] can usefully be from lOnm to 500microns, preferably 500nm to 100 microns
(although technical material greater than 500 microns could be also coated and employed in
some utilities (such as pharma) in a pre-granulation stage to protect a material). When the
crystal size is small, the micelle size chosen to coat the particle has to be even smaller.
Where the particle is a granule (or a spray-agglomerated granule), the size can vary from
about 50 microns to a few millimetres.
The present invention is illustrated by the following examples.
Example 1: Preparation of Polymers and Block Copolymers
The surface treatment of the present invention is hydrophobic. The copolymers described in
this example are AB block copolymers comprising a substantially hydrophobic block A, and
a substantially hydrophobic or hydrophilic block B which has a different affinity for or
solubility parameter within the liquid medium where the copolymers are dispersed compared
to block A, such that micelles form in the liquid medium.
Block A can comprise one or more monomers, for example; styrene (S) and styrene
derivatives, methacrylate and derivatives such as 2-ethyl hexyl methacrylate (EHMA), lauryl
methacrylate (LMA), octadecyl methacrylate (ODMA), glycidyl methacrylate (GMA) and
propylene oxide (PO). Those skilled in the art will appreciate the synthesis described in this
example is not limited to the monomers listed here.
In the current example, the hydrophobic or hydrophilic block B is composed of methacrylic
acid (MAA), 2-hydroxyethyl methacrylate (HEMA) or 2-ethyl hexyl methacrylate but those
skilled in the art will understand that other monomers leading to a hydrophilic block can also
be used.
The copolymers used herein were produced by Reversible Addition-Fragmentation Chain
Transfer (RAFT) according to the protocol described in the patent applications
WO08071957 and WO1003 8046 or by nitroxide mediated polymerisation (NMP) according
to the protocol described in the Arkema patent application WO2007/057620A1. Therefore
the block copolymers may be prepared by means of controlled living polymerisation
techniques, such as group transfer polymerisation (GTP), atomic transfer radical
polymerisation (ATRP), and activated regenerated by electron transfer (ARGET) or
activated generated by electron transfer (AGET) that can synthesize well-defined
homopolymers and block copolymers.
In addition to controlled radical polymerization, in the case of an heterocyclic monomer such
as propylene oxide, ring-opening polymerisation techniques can be used. Examples of the
composition of new prepared copolymers are given in Table 1.2.
A) Use of RAFT to synthesise copolymers
In this example, in addition to structures described in WO08071957 and WO1003 8046, new
copolymers structures were produced by RAFT polymerization using the RAFT agent,
2-cyanoisopropyl dithiobenzoate (CPDB). Whilst the current example prepares the block
copolymer CPDB, those skilled in the art will appreciate that other RAFT agents may be
used.
RAFT synthesis of Pol EHMA- / -MAA copolymer : R EHMA- -MAA
A series of poly[EHMAx-¾-MAAy] copolymers were prepared by RAFT polymerization
using CPDB as chain transfer agent, azobisisobutyronitrile (AIBN) as initiator and
propan-2-ol (IPA) as a solvent. The synthesis was a two step process: First, the
hydrophobic block (EHMA) was synthesised, then the synthesis of the hydrophilic block
(MAA) was initiated from the PEHMA homopolymer.
a) Synthesis of the block A: PEHMA.
EHMA (15g, 75.7mmol, 60eq), CPDB (0.31g, 1.26mmol, eq), AIBN (0.10g, 0.63mmol,
0.5eq) and IPA (solvent, 6.82g, 114mmol) were added in a two necked flask containing a
magnetic stirrer equipped with a cooling column. The mixture was degassed by nitrogen
bubbling and heated at 90°C in a thermostatically controlled oil bath under a nitrogen
atmosphere. The reaction was left under stirring for a minimum of 2hour30minutes (in
this example 3hl5min). A sample of the crude mixture was withdrawn and analysed by
size exclusion chromatography (SEC - See Figure 1.3), and by Proton Nuclear Magentic
Resonance (1H NMR). A conversion of 98% was determined by 1H NMR in CDC13,hence
the resultant product was P(EHMA)Xhomopolymer where x = 59.
b) Synthesis of blockBfrom blockA
30 minutes before the end of the first synthesis, MAA (6.54g, 76.0mmol, 60eq), AIBN
(0.10g, 0.64mmol, 0.5eq) and IPA (solvent, 45.39g, 757mmol) were added in another
flask containing a magnetic stirrer. The mixture was degassed by nitrogen bubbling.
At the end of the first synthesis (in the current example 3hl5min), the thermostatically
controlled oil bath was removed to stop polymerisation. The mixture containing the
second monomer was then transferred into the initial two necked flask via a cannula. This
flask was heated again at 85°C in the thermostatically controlled oil bath (equipped with a
cooling column) under nitrogen atmosphere to achieve the preparation of the second block
of copolymer. After a minimum of 2h30min (in this example 2h35min), a sample of the
crude mixture was withdrawn and analysed by 1H NMR and SEC (Figure 1.3).
A conversion of 88% was measured by 1H NMR in DMSO. The resultant product was
determined as P(EHMA -¾-MAAy) copolymer where x = 59 and y = 53.
Other P(EHMA -¾-MAAy) polymers were prepared with x=68 and y=25 and with x=33
and y=21. The generic structure of the corresponding P(EHMAx-¾-MAAy) copolymers is
given below.
Formula 1.1: Generic structure of the P(EHMA -¾-MAAy) synthesised by RAFT
Q
The P(EHMAx-6-MAAy) copolymers can also be prepared by NMP, ATRP, GTP and
indirect anionic polymerization.
Preparation of other copolymers by RAFT synthesis.
Various block copolymers were synthesised. Block B was obtained from various
methacrylated based monomers such as EHMA, LMA, ODMA and TFEMA. Block B was
composed of hydrophilic units such as MAA and HEMA, or hydrophobic monomers such as
EHMA. In this case, toluene was the solvent used for the synthesis instead of isopropanol.
The method described above for the synthesis of P(EHMAx-b-MAAy) was used, which led
for example to the successful synthesis of P(LMAx-b-EHMA ) and P(ODMA x-b-MAA ) .
The conversion rates, block sizes and reaction time are given in Table 1.2.
For the synthesis of (PEHMA5 i-r-PGMA22)-b-PMAA47the following protocol was used:
a) Synthesis of the blockA: PGMA and EHMA
GMA (3.29g, 23.2mmol, 25.6eq), EHMA ( l l.Olg, 55.6mmol, 61eq), CPDB (0.22g,
0.9mmol, leq), AIBN (0.0784g, 0.5mmol, 0.5eq) and IPA (solvent, 24.32g, 406.5mmol)
were added in a two necked flask containing a magnetic stirrer equipped with a cooling
column. The mixture was degassed by nitrogen bubbling and heated at 82°C for 5 hrs in a
thermostatically controlled oil bath under a nitrogen atmosphere and then reduced to 70°C
for another 16 hrs. A sample was removed for NMR analysis. A conversion of 93% GMA
and 89% EHMA was measured by 1H NMR in CDC13.
b) Synthesis of block Bfrom blockA
30 minutes before the end of the first synthesis, MAA (4.788g, 55.6mmol, 56.4eq), AIBN
(0.077g, 0.5mmol, 0.5eq) and IPA (solvent, 24.503g, 408.7mmol) were added in another
flask containing a magnetic stirrer. The mixture was degassed by nitrogen bubbling.
At the end of the first synthesis, the thermostatically controlled oil bath was removed to
stop polymerisation. The mixture containing the second monomer was then transferred
into the initial two necked flask via a cannula. This flask was heated again at 82°C for
4hrs in the thermostatically controlled oil bath (equipped with a cooling column) under
nitrogen atmosphere and then reduced to 70°C for 16 hrs to achieve the preparation of the
second block of copolymer. Polymers were precipitated out in diethyl ether and dried in a
vacuum oven at 40°C.
A conversion of 82% for the MAA was measured by 1H NMR in DMSO. The resultant
product was determined as (PEHMAx-r-PGMA )-b-PMAA copolymer where x = 51, y = 22
and z = 47.
Formula 1.2: Generic structure of the (PEHMAx-r-PGMA )-b-PMAA synthesised by RAFT
B) Use of NMP to synthesise copolymers
In this example, according to the protocol described in WO2007/057620-A1, new
copolymers structures were produced by NMP polymerization using the NMP agent
Blocbuilder®. Whilst the current example prepares the block copolymer using Blocbuilder®,
those skilled in the art will appreciate that other NMP agents may be used.
NMP synthesis of PS b- HEMA -r-PS
In the first step, the following conditions were used for the synthesis of PS with a targeted
polymerisation degree of 55. Styrene (15.00g, 0.14mol) and Blocbuilder® (l.OOg, 2.62mmol)
were added to a 100ml round bottom flask equipped with a magnetic stirrer. The reaction
flask was degassed by nitrogen bubbling for 20 minutes and then heated at 90°C in a
thermostatically controlled oil bath under a nitrogen atmosphere. After 78 hrs 40 min of
polymerization, a sample was withdrawn and analysed by 1H NMR (CDC13) . A conversion
of 76.9% was determined by 1H NMR in CDCI 3, hence the resultant product was
PSXhomopolymer where x = 42.
At the end of this step 15g chloroform was added to solubilise PS. The reactive mixture was
precipitated drop by drop in 300ml cold methanol and then filtered on paper. The product
was dried down in a vacuum oven.
In a second step, newly synthesised PS (l.OOg, 0.23mmol), styrene (0.24g, 2.32mmol),
HEMA (2.95g, 22.7mmol) and dimethylformamide (DMF, 4.02g, 0.55mmol) were added to
a 50ml round bottom flask equipped with a magnetic stirrer. PS was solubilised in DMF by
using a sonic bath (20min). The reaction flask was degassed by nitrogen bubbling for 20
minutes and then heated at 90°C in a thermostatically controlled oil bath under a nitrogen
atmosphere. After 18 hrs of polymerization, a sample was withdrawn and analysed by
1H NMR (DMSO). A conversion of 90.0% for HEMA and 8.0% for styrene was determined
by 1H NMR in DMSO, hence the resultant product was PSx-b-(HEMA -r-PS ) diblock
copolymer, where x = 42, y = 90 and z = 8.
At the end of this step, 7ml DMF was added to solubilise the copolymer. The reactive
mixture was precipitated drop by drop in 300ml cold ether and then filtered on paper. The
product was dried down in a vacuum oven.
Other PSx-b-(HEMAy-r-PS ) were prepared with x = 86, y = 57and z = 0 and with x = 74, y =
30 and z = 10. The generic structure of the corresponding PSx-b-(HEMAy-r-PS ) copolymers
is given below.
Formula 1.3: Generic structure of the PSx-b-(HEMAy-r-PS ) synthesised
C) Characterisation
SEC was used to determine the number-average molar mass (M ) and thus demonstrate the
increase of molar mass due to the addition of the second block during the polymerisation.
SEC was also used to determine the polydispersity index (PDI= Mw/M , where Mw is the
weight-average molar mass) of the polymers and copolymers, a low PDI being necessary to
achieve regular micelles.
The samples were injected in the SEC equipment (2 PL gel 5 Micron Mixed-c columns) and
analysis was performed as described below
The eluent was composed of tetrahydrofuran (THF) for P(EHMAx-¾-MAAy)
copolymers and DMF for PSx-b-(HEMAy-r-PS ) copolymers (elution flow rate: 1
ml/min, run time: 30 min)
The calculation (for data analysis) was made with a calibration curve based on
poly(methyl methacrylate).
Before injecting the polymer samples containing methacrylic acid units, a
methylation reaction was performed to convert the acid groups into methyl esters,
using trimethylsilyldiazomethane as the methylating agent, in order to solubilise the
polymers in THF to perform the analysis.
- The samples (20mg) were dissolved in the eluent and then filtered with a 0.2 mih
PTFE filter into the SEC vials.
An example of SEC chromatogram is given in Figure 1.4. The SEC chromatogram of the
first block of P(EHMA) and the chromatogram of the copolymer R(EHMA- -MAA) are
represented. The observed shift of the chromatogram is consistent with an extension of
chains between both steps.
Table 1.1
Copolymer PDI - block 1 PDI - block 2
P(EHMA5 -b-MAA53) 1.68 1.85
P(S42-b-[HEMA9o-r-S ]) 1.31 2.03
P(S 6-b-HEMA5 ) 1.65 1.58
P(S 4-b-[HEMA30-r-Sio]) 1.43 1.84
P(LMA33-b-EHMAi 06) 1.23 1.62
Table 1.1: Indication of PDI obtained by SEC for some copolymers described in Table 1.2
-1H NMR was used to determine the conversion of each polymerisation and the degree of
polymerisation (in number: DP ) calculated accordingly for each block.
1H NMR was performed with a 500 MHz apparatus (Bruker), in CDCI 3 for the
homopolymer, and in DMSO for the copolymer.
Table 1.2
Table 1.2: Synthesis and composition data according to 1H NMR; EHMA: 2-ethyl
hexyl methacrylate; HEMA: 2-hydroxyethyl methacrylate ; MAA: methacrylic acid;
S: styrene; LMA: lauryl methacrylate; ODMA: octadecyl methacrylate; Conv.:
conversion given in %; DPn th: degree of polymerisation targeted; DPn exp: degree
of polymerisation calculated;
i) Synthesis performed using RAFT in IPA
ii) Synthesis performed using NMP in DMF
iii) Synthesis performed using RAFT in toluene
Example 2 : Demonstration of micelle formation
Micellar aggregates can be formed from the copolymers of Example 1. Size
distribution measurements using a Malvern Nano Zetasizer were performed on solutions of
in apolar solvents such as dodecane, hexane, Exxsol D140, Solvesso 200ND and Isopar V.
1. To demonstrate the formation of micelles in apolar solvent, a solution (10 to 20ml) of
copolymer was prepared by dissolving the copolymer powder in THF (Sigma-
Aldrich) ( 1 wt%).
2. When the polymer had dissolved, a second solvent as indicated in Table 2.1 was
added drop-by-drop until it reached a large enough quantity that it became the
continuous phase. For size distribution measurements, this was when the
concentration of copolymer reached -0.01 wt%.
3. To ensure that equilibrium was reached the mixture was gently agitated for over 1
hour (mixing with a magnetic stirrer set on low).
To ensure an accurate measurement by the Malvern Nano Zetasizer, concentrations of the
copolymer solution were varied so the sample was in the optimum detection range of the
instrument for the polymer being examined. The size distribution measurements shown in
Table 2.1 shows that the copolymers form micelles, since the minimum diameter measured is
20 nm and if copolymers were present as unimers, the diameter would be less than 5nm. In
all cases a clear solution was formed following stage 1. The results in Table 2.1 demonstrate
that in each case micelles were formed following stage 3.
Examples of hydrophobic copolymer micelles solutions which were prepared according to
the general procedure are described in Table 2.1.
size distribution following stage 3
(nm)
Exxsol Solvesso
Dodecane Hexane Isopar V
D140 200ND
230 - 240 100 - 110 95 - 105 20 - 80 25 - 70
Table 2.1: Micelle size measurements of copolymer P(Ethyl Hexyl MA(29)-b-MAA(48)) in
apolar liquid media. Measurements collected using a Malvern Nano Zetasizer.
Example 3 - The preparation and application of a surface treatment according to the
present invention.
3.a Coating a large surface
A polymer or polymeric composition prepared according to the present invention may be
coated onto a preferred substrate, as described hereafter, by any established coating process,
for example, but not limited to a spray process. Generally, the treatment process involves the
following steps:
Step (1): Dissolution of the copolymer molecules in a suitable organic solvent under gentle
agitation.
The copolymers chosen are usually not of a high molecular weight (the copolymers typically
have a range of between 3000 to 100000 g/mol) and such molecules equilibrate rapidly when
dissolved in a good solvent.
Solvents suitable for use in the composition of the present invention are preferably as
previously described.
Step (2): Slow drop-by-drop addition of a second solvent, which is a poor solvent for one of
the blocks and a good solvent for the other block, under gentle agitation.
Agitation of the copolymer systems was used during the process of dissolution and
mixing, but it was not found to be critical and simply slowly stirring the copolymer system
was found to be sufficient. The length of time for agitation depended on the solvent system.
Examples of hydrophobic copolymer micelle solutions which were prepared according to the
precedent protocol are described in Table 3.1.
Table 3.1
Table 3.1: Description of hydrophobic copolymer micelle solutions prepared according to the
present invention
Step (3): Applying the solution of the copolymer to a desired substrate.
Whilst not wishing to be bound by any particular theory, evidence from the present invention
implies that adsorption of the copolymer onto the substrate is complete after a few minutes.
Methods of exposing the substrate to the solution include any known technique for forming a
coating from a solution such as spin coating, dip coating, roller coating, brush coating,
curtain flow or spraying, roller coating, wire-bar coating, extrusion coating, air knife coating,
curtain coating or slide coating. More preferably, dipping and spraying ensures that every
part of the surface has been wetted by the treatment composition.
The treatment can be applied to both interior and exterior surfaces.
Step (4): Drying the treated surface.
Preferably the treated surfaces need to be dried after applying the treatment composition.
This can be achieved at room temperature or at higher temperatures, and/or at lower
pressure. It should be noted that the drying temperature does not enhance the performance of
the coating; rather it shortens the drying time of the treatment. Drying in ambient conditions
will only lengthen the drying time.
3.b Coating of a discrete object
A copolymer solution was prepared by dissolving the copolymer in a good solvent (toluene /
THF) under gentle agitation. Once a homogeneous solution was obtained a second solvent
(for example hexane / Isopar V) was added to the mixture using drop-by-drop addition. The
final concentration of the copolymer in solution was 0.4 wt%. The second solvent was
selected to be a poor solvent or non-solvent for one of the blocks and a good solvent for the
other block. The mixture was gently stirred and left for more than 2 hours in order to allow
the copolymers to equilibrate into micelles. When the micelle system had reached
equilibrium, l g of TMX (thiamethoxam) air milled crystals were added to the mixture. The
sample was then allowed to tumble for at least 2 hours in order to ensure complete mixing
and thus allow time for the micelles to coat the individual TMX crystals. Table 3.2 shows
possible but not limiting combinations of copolymers and organic solvents which form
micelles and can be used to coat crystals.
Mixtures Copolymer actives Step 1: Addition of the Step 2 : Addition of the
good solvent second solvent
Name Volume (g) Name Volume (g)
1 PEHMA(59)-b- Toluene 0.96 Hexane 9
PMAA(53)
2 PEHMA(59)-b- Toluene 0.96 Isopar V 9
PMAA(53)
3 PEHMA(59)-b- THF 0.96 Hexane 9
PMAA(53)
4 PEHMA(59)-b- THF 0.96 Isopar V 9
PMAA(53)
5 PEHMA(29)-b- Toluene 0.96 Hexane 9
PMAA(48)
6 PEHMA(29)-b- Toluene 0.96 Isopar V 9
PMAA(48)
7 PEHMA(29)-b- THF 0.96 Hexane 9
PMAA(48)
8 PEHMA(29)-b- THF 0.96 Isopar V 9
PMAA(48)
PMAA: polymethacrylic acid; PEE MA polyethylhexylmethacrylate
Table 3.2: Composition of copolymers solutions in apolar hexane and in Isopar V
The copolymer solutions in Table 3.2 were used to coat TMX particles using the
methodology outlined previously. Figures 3.1 and 3.2 demonstrate that micelles have been
deposited from the organic solutions.
Figures 3.1 and 3.2 clearly illustrate the deposition of micelles from a range of organic
solvents on all crystal faces, including corners and edges of TMX.
Example 4 : Crosslinking of copolymer micelles
Crosslinking is described as the physical and/or chemical interaction between chains of the
AB diblock copolymer. The crosslinking can take place either in the core of the micelles, in
the corona of the micelles and/or between the coronas of two contiguous micelles.
In this example, crosslinking of copolymer micelles was used to decrease the solubility of a
coated crystalline material in water. Micelles comprising AB di-block copolymers were
deposited on the surface of crystals of a crystalline material (for example a pharmaceutical or
an agrochemical) in oil based liquid media. Addition of either linear or cyclic diamine
molecules to this system led to the modification of the topology of the micellar coating. This
also resulted in a decrease in the release rate of the crystalline material in water compared to
crystalline material coated with un-crosslinked copolymer micelles.
Example of crosslinking in oil based system
TMX was coated by using the same protocol as example 3b.
A copolymer solution (lOg) was prepared by dissolving (PEHMA i-r-PGMA22)-b-PMAA47
copolymer in a good solvent (THF) under gentle agitation. Once a homogeneous solution
was obtained a second solvent (hexane) was added to the mixture using drop-by-drop
addition. The final concentration of the copolymer in solution was 0.4 wt%. The second
solvent was selected to be a poor solvent or non-solvent for one of the blocks and a good
solvent for the other block. The mixture was gently stirred and left for 24 hours in order to
allow the copolymers to equilibrate into micelles. When the micelle system had reached
equilibrium, l g of TMX air milled crystals were added to the mixture. The sample was then
allowed to tumble for 24 hours in order to ensure complete mixing and thus allow time for
the micelles to coat the individual TMX crystals.
Crosslinking was then performed.
1. A diamine compound (see Table 4.1 for mass and molar ratio compared to MAA
functions in the copolymer) was added to the solution and tumbled for 24 hours.
2. The mixture was then centrifuged for 2 minutes at 2000 rpm and approximately 9ml
of the supernatant liquid was removed. The same quantity of water based TMX
saturated stock solution was added, and the mixture tumbled again for 30 minutes.
3. The mixture was then centrifuged for 2 minutes at 2000rpm and 9ml the supernatant
liquid was removed.
4. The sample was then dried under vacuum at 50°C for 8 hours thus removing all
remaining solvents.
Table 4.1
Molar ratio of
(carboxylic acid + Mass of crosslinker
Cross-linker
epoxy) functions used (g)
compared to amine
Control (coated but not crosslinked)
Hexamethylene diamine (0.4 wt%) 1 : 3.8 0.0348
Hexamethylene diamine (5 wt%) 1 : 1.1 0.1566
Table 4.1: Percentages weight loss of the coated TMX particles
To perform release rate analysis 45-55mg of each sample was accurately weighted into a
60ml powder jar and 50ml of dispersant solution (0.1%w/w Aerosol OTB, 0.5%w/w Morwet
D425 in DI water) added at time zero. The samples were then placed on a roller moving at
20rpm. A time point measurement of TMX in solution was made by extracting 3ml of
solution and passing it through a 0.45 mih filter. The filtrate was then analysed by HPLC to
determine the concentration of TMX. The analysis was carried out by High-performance
liquid chromatography (HPLC) using an Agilent 1100 (equipped with an auto-injector), a
50 X 3.0 MM ACE 3mM CI 8 COLUMN FROM ACE, PART NUMBER ACE-1 11-0503
and mobile phases of (A) Acetonitrile + 0.1% Formic acid and (B) ASTM II Water + 0.1%
Formic acid. Analysis was carried out with an injection load of 5 mΐ and column temperature
of40°C. Data were collected at a range of time points
Total TMX content of the samples was determined by weighing 30-50mg of each dry
powder accurately weighted into an aluminium weighting boat. The weighing boat was then
placed in a volumetric flask and 50 ml acetonitrile added. The flask was gentle swirled until
a colourless solution was formed. This solution was analysed using the HPLC conditions
described previously.
Table 4.2 shows the quantity of TMX released after 1 and 4 hours as a percentage of the total
TMX concentration as measured by the method described previously.
Table 4.2
Example 5: Surface characterisation after the application of hydrophobic copolymer
micelle solution
The mixture containing the micelles formed from the copolymers PEHMA-b-PMAA in
hexane (Table 5.1 - row 1) was used to treat glass microscope slides and painted Q-panels
by dip coating, as well as Poly(methyl methacrylate) (PMMA), Polyethylene terephthalate
(PET) and Polyvinyl chloride (PVC) sheets by flow coating. The treatment led to an increase
of the overall hydrophobicity of the surface as indicated by the contact angle increase of the
surface after treatment (Table 5.1)
Table 5.1
Before treatment After treatment
Glass panel (i) 25 ± 1 60 ±2
Painted Q-Panel (i) 69 ±2 94.6 ±0.6
PET (ii) 80.9 ±0.2 95.3±0.1
PMMA (ii) 102.9±0.2 106.2±0.1
PVC (ii) 85.3±0.1 93.7±0.2
Table 5.1: Contact angle before and after treatment with hydrophobic micelles formed using
the block copolymers PEHMA-b-PMAA at 0.4 wt% in hexane
(i) Coating with PEHMA59-b-PMAA53
(ii) Coating with PEHMA59-b-PMAA52
Example 6: Use of oil-based micelles to coat -actives used in the field of laundry
The protocol described in example 3 was used to coat sodium percarbonate with a copolymer
micellar solution of Poly(PS42-b-HEMA6 ) at 0.4 and 5 wt% in DMF/Solvesso 200 - see
Figure 6.1.
The protocol described in example 3 was used to coat sodium carbonate with a micellar
solution of Poly(PS 42-b-HEMA4 5) at 0.4 and 5 wt% in DMF/Solvesso 200 - see Figure 6.2.
Example 7: Use of oil-based micelles to coat - actives used in the field of taste masking
Bitrex was chosen as it is the bitterest chemical known to man, and has similar physical and
chemical characteristics to many pharmaceuticals.
Denatonium benzoate (Bitrex) crystals were coated by adding a copolymer micellar solution
of Poly(EHMA o-b-MAA 55) at 0.4 and 5 wt% in DMF/Solvesso.
The protocol described in Example 3 was used to coat Bitrex - see Figure 7.1.
Visual release rate test
Release rate was monitored visually in order to compare the uncoated Bitrex with the 5 wt%
coated Bitrex particles. 0.4mg of sample was agitated in 10ml of water and observed over
8 hours. After 15 minutes the uncoated Bitrex was fully dissolved but after 8 hours the
coated particles were still present - see Figure 7.2.
UV Vis release rate measurement
lOOmg in 40ml water of uncoated bitrex and 5 wt% coated Bitrex were shaken for a period
of 10 minutes and sampled at various time intervals. 2ml of the mixture was removed at each
time interval for analysis.
Total content of the samples was determined by accurately weighing 17.5mg of 5 wt%
coated Bitrex particles, sonicated until the coated particles had fully dissolved in 25ml of
water and analysed by UV/Vis. A total content measurement of 57.75% was obtained. See
Figure 7.3.
Table 7.1 % release of micelle coated and uncoated Bitrex relative to the total content
determined by UV/vis measurements.
CLAIMS
1. A process for coating a surface with micelles which comprise an AB block
copolymer comprising the step of treating the surface with an apolar liquid containing
the micelles.
2. A process as claimed in claim 1 where the copolymer has a molecular weight of from
3000 to lOOOOODalton.
3. A process as claimed in claim 1 or 2 where the micelles have a maximum dimension
of from 3 to 500nm.
4. A process as claimed in any one of the preceding claims where the micelles each
comprise from 10 to 1000 copolymer molecules.
5. A process as claimed in any one of the preceding claims where in the copolymer the
ratio of the number of Block A units to the number of Block B units is from 1:0. 1 to
1:10.
6. A process as claimed in any one of the preceding claims where the micelles are
crosslinkable and are optionally crosslinked before, during or after treating the
surface with the apolar liquid containing the micelles.
7. A process as claimed in any one of the preceding claims where the cores of the
micelles contain a chemical.
8. A process as claimed in claim 7 where the chemical contained in the cores of the
micelles is a photoprotectant.
9. A process as claimed in claim 7 where the chemical contained in the cores of the
micelles is a biologically active compound.
10. A process as claimed in claim 7 where the chemical contained in the cores of the
micelles is an adjuvant.
11.A process as claimed in any one of the preceding claims where the surface is selected
from metals, metal alloys, glasses, plastics, textiles, rubber, porcelain, ceramics, tile,
enamelled appliances, polymers, resins, painted surfaces, natural surfaces and
cellulose.
12. A process as claimed in any one of the preceding claims where the apolar liquid is
selected from alkanes, halogenated solvents, aromatic solvents and combinations
thereof.
13. A process as claimed in any one of the preceding claims where the ratio by weight of
block copolymer to the apolar liquid is from 1 : 100,000 to 1 : 1.
14. A surface coated with micelles as defined in any of the preceding claims.
15. A surface as claimed in claim 14 where the surface is selected from metals, metal
alloys, glasses, plastics, textiles, rubber, porcelain, ceramics, tile, enamelled
appliances, polymers, resins, painted surfaces, natural surfaces and cellulose.
16. A surface as claimed in claim 14 which is self cleaning or easy to clean.