Description
Non-aqueous dispersions of a conductive polymer
Field of the Invention
[001] The present invention relates to a dispersion of a conductive polymer, in
particular a polymer or copolymer of a substituted or unsubstituted thiophene,
and a polyanion in a non-aqueous dispersion medium. The present invention
also relates to a method of preparing such a dispersion from a freeze dried
composition comprising a conductive polymer, in particular a polymer or
copolymer of a substituted or unsubstituted thiophene, and a polyanion.
Background of the Invention
[002] The preparation of polythiophenes and dispersions thereof for use in
antistatic coatings has been described in the literature e.g. ' Handbook of
Organic Conductive Molecules and Polymers' , ed. H.S. Nalwa, J . Wiley &
Sons, 1997. Polythiophenes have conductive properties.
[003] In large scale methods for preparing aqueous dispersions of a latex
comprising a polyanion and a polymer or copolymer of a substituted or
unsubstituted thiophene, the solid content of the aqueous dispersions is
limited to only a few percent, due to production reasons such as the need for
ultrafiltration, the viscosity of the dispersion etc. It should be noted that such
dispersions are often erroneously referred to as solutions due to the very
small particle size, i.e. 20 to 50 nm, of the polythiophene/polyanion latex.
Shipment of such dilute dispersions is expensive and cumbersome in view of
the high volume and weight associated therewith.
[004] For instance, PEDOT, i.e. poly(3,4-ethylenedioxythiophene) in combination
with PSS (PSS as used in the present disclosure stands for poly(styrene
sulfonic acid) or poly(styrene sulfonate)), is produced industrially as an
aqueous dispersion of approximately 1 wt% of PEDOT/PSS. However many
potential applications for PEDOT/PSS require a non-aqueous dispersion in
which the concentration of water is as low as possible, while retaining or
increasing the concentration of thiophene polymers or co-polymers. Various
methods such as e.g. simple evaporation of the water (W099/34371),
dehydratation by dialysis (WO02/42352), azeotropic distillation (WO
02/072660), flash evaporation (WO 03/087222) and solvent addition followed
by evaporation of the water (WO 03/48228, WO 03/048229) have been
investigated to obtain these concentrated dispersions.
[005] EP-A 1801 143 discloses a coating solution or dispersion comprising a
redispersible or soluble product obtainable as a dry product or as a paste by
freeze drying an aqueous dispersion of a latex comprising a polyanion and a
polymer or copolymer of a substituted or unsubstituted thiophene. The water
content of the coating solution or dispersion may be less than 12 wt %,
preferably less than 6 wt % relative to the total weight of the dispersion.
[006] The presence of water in a non-aqueous dispersion of a polymer or
copolymer of a substituted or unsubstituted thiophene and a polyanion may
have a negative influence on the conductivity of coatings obtained from such
dispersions. Also, in some applications wherein conductive polymers may be
used, for example OLED, OPV, Dye Sensitized Solar Cells (DSSC) and also
solar cells based on Perovskites, the presence of a minor amount of water
may have a detrimental effect on the performance and lifetime of the devices.
Summary of the Invention
[007] It is an object of the present invention to provide a substantially water free
dispersion of a conductive polymer, in particular a polymer or copolymer of a
substituted or unsubstituted thiophene, and a polyanion in a non-aqueous
dispersion medium of which the optical and conductive properties of coatings
or patterns obtained thereof remain at a sufficient level.
[008] It is another object of the present invention to provide a method of preparing
such a substantially water free dispersion from a freeze dried composition
comprising a conductive polymer, in particular a polymer or copolymer of a
substituted or unsubstituted thiophene, and a polyanion.
Detailed description of the invention
[009] The term " alkyl" means all variants possible for each number of carbon
atoms in the alkyl group such as but not limited to methyl; ethyl; for three
carbon atoms: n-propyl and isopropyl; for four carbon atoms: n-butyl, isobutyl
and tertiary-butyl; for five carbon atoms: n-pentyl, 1,1-dimethyl-propyl, 2,2-
dimethylpropyl and 2-methyl-butyl; etc.
[010] The term " alkoxy" means all variants possible for each number of carbon
atoms in the alkoxy group such as but not limited to methoxy; ethoxy; for
three carbon atoms: n-propoxy and isopropoxy; for four carbon atoms: nbutoxy,
isobutoxy and tertiary-butoxy; etc.
[01 1] Unless otherwise specified a substituted or unsubstituted alkyl group is
preferably a Ci to C 6-alkyl group.
[012] Unless otherwise specified a substituted or unsubstituted alkenyl group is
preferably a Ci to C 6-alkenyl group.
[013] Unless otherwise specified a substituted or unsubstituted alkynyl group is
preferably a Ci to C 6-alkynyl group.
[014] Unless otherwise specified a substituted or unsubstituted aralkyl group is
preferably a phenyl or naphthyl group including one, two, three or more Ci to
C 6-alkyl groups.
[015] Unless otherwise specified a substituted or unsubstituted aryl group is
preferably a phenyl group or naphthyl group
[016] Unless otherwise specified a substituted or unsubstituted heteroaryl group is
preferably a five- or six-membered ring substituted by one, two or three
oxygen atoms, nitrogen atoms, sulphur atoms, selenium atoms or
combinations thereof.
[017] The term " substituted" , in e.g. substituted alkyl group means that the alkyl
group may be substituted by other atoms than the atoms normally present in
such a group, i.e. carbon and hydrogen. For example, a substituted alkyl
group may include a halogen atom or a thiol group. An unsubstituted alkyl
group contains only carbon and hydrogen atoms.
[018] Unless otherwise specified a substituted alkyl group, a substituted alkenyl
group, a substituted alkynyl group, a substituted aralkyl group, a substituted
aryl, a substituted heteroaryl and a substituted heterocyclic group are
preferably substituted by one or more substituents selected from the group
consisting of methyl, ethyl, n-propyl, isopropyl, n-butyl, 1-isobutyl, 2-isobutyl
and tertiary-butyl, acid, ester, amide, ether, thioether, ketone, aldehyde,
sulfoxide, sulfone, sulfonate ester, sulphonamide, -CI, -Br, -I, -OH, -SH, -CN,
COOH and -NO2.
[019] The term " Freeze-drying" as used herein means a lyophilization process in
which a substance is first frozen and then the quantity of solvent (generally
water) is reduced, first by sublimation (= primary drying process) and then by
desorption (= secondary drying process) until the temperature of the shelves
becomes equal to the atmospheric temperature in the freeze dryer. The
freeze-drying process is enabled by the ability of solid materials such as ice
to sublime (change directly into a gas without passing through a liquid phase)
under the right conditions.
[020] The term " acid sensitive functional group" as used herein means a
functional group that reacts in an acid medium with for example water.
Non-aqueous dispersions of a conductive polymer and a polyanion
[021] The dispersion of a conductive polymer and a polyanion in a non-aquoues
medium according to the present invention further comprises a compound
having an acid sensitive functional group selected from the group consisting
of a ketal, an acetal, an aminal, a hemi-ketal, a hemi-acetal, a hemi-aminal, a
thioacetal, an amide acetal, an orthoester, an orthoether, an enolester, an
enolether, and an enolamine.
[022] The dispersion may comprise further ingredients to optimize the dispersion
stability, for example surfactants and/or dispersants, or to optimize its
properties in function of the application for which the dispersion is used.
[023] The dispersion contains less than 2.0 wt %, preferably less than 1.0 wt%,
more preferably less than 0.1 wt%, most preferably less than 0.01 wt% of
water, relative to the total weight of the dispersion. Such a dispersion is also
referred to as a substantially water free dispersion.
Compounds having an acid sensitive functional group
[024] The compound having an acid sensitive functional group is selected from the
group consisting of a ketal, an acetal, an aminal, a hemi-ketal, a hemi-acetal,
a hemi-aminal, a thioacetal, an amide acetal, an orthoester, an orthoether, an
enolester, an enolether, and an enolamine.
[025] The compound having an acid sensitive functional group is preferably
selected from the group consisting of a ketal, an acetal, and an orthoester.
[026] A particularly preferred compound having an acid sensitive functional group
is an orthoester.
[027] Preferred orthoesters are those according to Formula I,
Formula I
wherein
Ra, Rb, Rc independently represent a substituted or unsubstituted alkyl
group, a substituted or unsubstituted alkenyl group, a substituted or
unsubstituted alkynyl group, a substituted or unsubstituted aralkyl
group, a substituted or unsubstituted aryl group, a substituted or
unsubstituted heteroaryl group or a substituted or unsubstituted
heterocyclic group;
Rd represents a hydrogen, a substituted or unsubstituted alkyl group, a
substituted or unsubstituted alkenyl group, a substituted or
unsubstituted alkynyl group, a substituted or unsubstituted aralkyl
group, a substituted or unsubstituted aryl group, a substituted or
unsubstituted heteroaryl group or a substituted or unsubstituted
heterocyclic group; or
Ra together with Rb or Rc may represent the necessary atoms to form
a substituted or unsubstituted ring; or
Rb together with Rc may represent the necessary atoms to form a
substituted or unsubstituted ring; or
Rd together with Ra, Rb or Rc may represent the necessary atoms to
form a substituted or unsubstituted ring.
[028] Preferably Ra, Rb, Rc and Rd are substituted or unsubstituted C1-C6 alkyl
groups.
[029] Highly preferred orthoesters according to Formula I are trimethyl
orthoacetate, triethyl orthoacetate, trimethyl orthopropionate, and triethyl
orthopropionate.
[030] Another example of an orthoester that may be used in the present invention
are those according to Formula II,
Formula I I
wherein Rd has the same meaning as in Formula I .
[031] Compounds according to Formula I I are referred to as compounds
comprising an " OBO protecting group" (4-methyl-2,6,7-trioxabicyclo[
2.2.2]octan-1-yl) which is formed by the action of (3-methyloxetan-3-
yl)methanol on activated carboxylic acids in the presence of Lewis acids and
was developed by Elias James Corey.
[032] The amount of the compound having an acid sensitive functional group is
preferably sufficient to remove substantially all the water present in the
dispersion. More preferably an excess of the compound having an acid
sensitive functional group relative to the water present in the dispersion is
used. The amount of the compound having an acid sensitive functional group
is preferably from 0.5 to 5 wt %, more preferably from 1.0 to 2.5 wt % relative
to the total weight of the dispersion.
[033] Preferably compounds having an acid sensitive functional group are used,
which form upon reaction with water volatile compounds, such as for
example alchols, esters or ketones, which may be removed at moderate
temperatures. Preferably both the compounds having an acid sensitive
functional group and their reaction products may be substantially removed at
moderate temperatures during the preparation of the devices in which the
dispersions are used to avoid any contamination resulting in inferior
properties of such devices.
[034] The compounds having an acid sensitive functional group and their reaction
products preferably have a boiling point at atmospheric pressure below
200°C, more preferably below 150°C, most preferably below 100°C.
Preferred reaction products are for example methanol, ethanol, ethylacetate,
or acetone. For example triethyl orthoacetate forms ethanol and ethylacetate
upon reaction with water; 2,2-dimethoxypropane forms acetone and
methanol upon reaction with water.
[035] Preferably the compound having an acid sensitive functional group and its
reaction products do not substantially influence the performance of coatings
obtained from the conductive dispersions. The compounds preferably do not
adversible influence the conductivity, the optical properties such as Haze or
visual transmittance, or the physical and chemical properties of such
coatings.
Polyanion
[036] Examples of polyanions suitable for use in the freeze-dried composition of
the present invention are those disclosed in EP-A 440957. These polyanions
are for instance formed from polyacids or can be added as a salt of the
corresponding polyacids, e.g. an alkali salt.
[037] In a preferred embodiment of the present invention, the polyanion is the
anion of a polymeric carboxylic acid, such as poly(acrylic acid),
poly(methacrylic acid) and poly(maleic acid), or of a polymeric sulphonic acid,
such as poly(styrene sulphonic acid) or polyvinyl sulphonic acid). These
polycarboxylic acids and polysulphonic acids can also be copolymers of
vinylcarboxylic acids and/or vinylsulphonic acids with other polymerizable
monomers, e.g. acrylic acid esters, methacrylic acid esters and styrene.
[038] In a more preferred embodiment of the present invention, the polyanion is the
anion of poly(styrene sulphonic acid) or of copolymers thereof with styrene.
In a most preferred embodiment of the present invention, the polyanion is
poly(styrenesulfonate).
[039] The molecu lar weig ht of these polyanion forming polyacids is preferably
between 1000 and 2x1 06 g/mol or more, more preferably between 2000 and
5x1 05 g/mol.
[040] These polyacids or their alkali salts are commercially available and can be
prepared according to the known methods, e.g . as described in Houben-
Weyl, Methoden der Organ ische Chemie, Bd. E20 Makromolekulare Stoffe,
Teil 2, (1987), pp. 1141.
Polymer or copolymer of a substituted or unsubstituted thiophene
[04 1] Conductive polymers that may be used are disclosed in for example
Conducting Polymers, Fundamentals and Applications: A Practical Approach
(Prasan na Chandrasekhar), Conducting Polymers: A New Era in
Electrochem istry (Gyorgy Inzelt), Handbook of Organ ic Conductive
Molecu les and Polymers: Conductive polymers : synthesis and electrical
properties (Hari Sing h Nalwa), Conjugated Polymers: Theory, Synthesis,
Properties, and Characterization (Terje A. Skotheim, Joh n Reynolds),
PEDOT: Principles and Applications of an Intrinsically Conductive Polymer
(Andreas Elsch ner et al.).
[042] Examples of such conductive polymers are polyth iophenes, polyan ilines,
polypyrroles, and polyacetylene.
[043] The conductive polymer is preferably a polymer or copolymer of a substituted
or unsubstituted thiophene.
[044] Accord ing to an embod iment of the present invention , the thiophene is
substituted in at least one of the 3- or 4-positions with a substituent selected
from the group consisting of an optionally substituted C Oalkoxy grou p, an
optionally substituted Ci-i o alkyl grou p, and an optionally substituted aryl
grou p, or the 3- and 4- positions are linked with an optionally substituted oxy-
C -4 alkylene-oxy group.
[045] The aforementioned alkyl, oxy-alkylene-oxy, cylcloalkylene and alkylene
grou ps may be unsubstituted or may optionally be substituted with 1, 2, 3, 4
or 5 substituent(s) independently selected from the grou p consisting of
phenyl, fluoro, chloro, bromo, iodo, methoxy, ethoxy, propoxy, isopropoxy,
butoxy, sec-butoxy, tert-butoxy, nitro, cyano and hydroxy.
[046] The aforementioned alkoxy groups may be unsubstituted or may optionally
be substituted with 1, 2, 3, 4 or 5 substituent(s) independently selected from
the group consisting of phenyl, fluoro, chloro, bromo, iodo, nitro, cyano and
hydroxy.
[047] In a preferred embodiment of the present invention the polymer of a
substituted thiophene is represented by Formula III
Formula III
wherein
1 < n < 10 000;
R and R independently represents hydrogen, a substituted or
unsubstituted C1-C4 alkyl group, or together form a substituted or
unsubstituted C1-C4 alkylene group or a substituted or unsubstituted C3-C10
cycloalkylene group.
[048] In a preferred embodiment 2 < n < 5 000.
[049] In another preferred embodiment R 1 and R2 independently represent an
unsubstituted ethylene group, an unsubstituted methylene group, an
optionally alkyl-substituted methylene group, an optionally Ci-12 alkyl- or
phenyl-substituted ethylene group, an unsubstituted 1,3-propylene group or
an unsubstituted 1,2-cyclohexylene group.
[050] In another embodiment of the present invention, the polymer or copolymer of
a substituted thiophene is a polymer or copolymer of a 3,4-dialkoxythiophene
in which the two alkoxy groups together form an optionally
substituted oxy-alkylene-oxy bridge selected from the group consisting of:
3,4-methylenedioxy-thiophene, 3,4-methylenedioxythiophene derivatives,
3,4-ethylenedioxythiophene, 3,4-ethylene-dioxythiophene derivatives,
3,4-propylenedioxythiophene, 3,4-propylenedioxy-thiophene derivatives,
3,4-butylene-dioxythiophene and 3,4-butylenedioxy-thiophene derivatives
and copolymers therewith.
[051] In yet another embodiment of the present invention, the polymer or
copolymer of a substituted thiophene is a polymer or copolymer of a
3,4-dialkoxy-thiophene in which the two alkoxy groups together form an oxyalkylene-
oxy bridge substituted with a substituent selected from the group
consisting of alkyl, alkoxy, alkyloxyalkyl, carboxy, alkylsulfonato and carboxy
ester groups.
[052] In yet another embodiment of the present invention, the polymer of a
substituted thiophene is a poly(3,4-dialkoxy-thiophene) in which the two
alkoxy groups together form an optionally substituted oxy-alkylene-oxy bridge
which is an unsubstituted 1,2-ethylene group, an unsubstituted methylene
group, an optionally alkyl-substituted methylene group, an optionally C1-12
alkyl- or phenyl-substituted 1,2-ethylene group, an unsubstituted
1,3-propylene group or an unsubstituted 1,2-cyclohexylene group.
[053] Such polymers are disclosed in Handbook of Oligo- and Polythiophenes
Edited by D. Fichou, Wiley-VCH, Weinheim (1999); by L . Groenendaal et al.
in Advanced Materials, volume 12, pages 481-494 (2000); L. J . Kloeppner et
al. in Polymer Preprints, volume 40(2), page 792 (1999); P. Schottland et al.
in Synthetic Metals, volume 101 , pages 7-8 (1999); and D. M. Welsh et al. in
Polymer Preprints, volume 38(2), page 320 (1997).
Surfactants and/or dispersants
[054] The surfactants are preferably anionic or non-ionic.
[055] Preferred surfactants are for example those disclosed in WO2002/00759 in
particular MARLON™ A365, AKYPO™ , ARKOPAL™ N060 , ZONYL™FSO
HOSTAPAL™ B, ARKOPON™, MERSOLAT™ or CAPSTONE®.
[056] Other preferred surfactants are those available under the tradename
TRITON® X from Dow Chemicals, those under the tradename DYNOL™
from Air Products, and the fluorsurfactants from Chemguard and
Synperonic®.
[057] Preferred dispersants are polyoxyethylene alkylamines such as disclosed in
for example JP201 2-1 32026. Particularly preferred are the ethoxylated
amines, commercially available under the Trade name Ethomeen™ from
Akzo Nobel, such as for example Ethomeen C/12, Ethomeen C/25,
Ethomeen T/12, Ethomeen S/12, etc.
[058] Other preferred dispersants are hydrophilic glycol ethers, commercially
available under the tradename Dowanol™ from Dow Chemicals such as for
example Dowanol EPh. Other preferred dispersants are the Dysperbyk®,
Ethylan™ , Solsperse™, Tilosperse™, Servoxyl™, Surfynol™, Hypermer™,
Sokolan™, or Lupasol™ dispersants.
Non-aqueous medium
[059] The non-aqueous medium is preferably selected from alcohols, esters,
ketones, aldehydes, ethers, or mixtures thereof.
[060] The non-aqueous medium is preferably selected from the group consisting of
ethanol, acetone, methyl ethyl ketone (MEK), ethylacetate, isopropylalcohol
(IPA), toluene, butylacetate, propylacetate, and mixtures thereof.
Other ingredients
[061] The dispersion may further comprise other ingredients, depending on the
application for which the dispersion will be used.
[062] For example the viscosity of the dispersion may be adapted to the method
used to apply the dispersion on a substrate, i.e. the coating and/or printing
method.
[063] When used as a screen printing ink, the viscosity is preferably between 3000
and 400000 mPa.s, more preferably between 5000 and 100000 mPa.s, most
preferably between 10000 and 50000 mPa.s.
[064] When used as a flexographic or gravure ink, the viscosity is preferably
between 50 and 3000 mPa.s, more preferably between 200 and 1000 mPa.s,
most preferably between 300 and 500 mPas.s.
[065] When used as an inkjet ink, the viscosity is preferably between 1 and 50
mPa.s, more preferably between 5 and 30 mPa.s, most preferably between 7
and 15 mPa.s.
[066] The viscosities referred to above are measured at a shear rate of 1/s at
temperature between 20 and 25°C (for example with an AR2000 Rheometer
from Texas Instruments).
[067] The viscosity may be optimized by adding a binder and/or a thickener.
Binders that may be used are polyvinylacetate, polycarbamate, polyvinyl
butyral, polyacrylic acid ester, polyacrylic acid amide, polymethacrylic acid
ester, polymethacrylic acid amide, polystyrene, polyacrylonitrile,
polyvinylchloride, polyvinylpyrrolidine, polybutadiene, polyisoprene,
polyethers, polyurethanes, polyamides, polyimides, polysulphones, silicones,
epoxy resins, styrene/acrylate copolymers, vinylacetate/acrylate copolymers,
ethylene/vinyl acetate copolymers, polyvinyl alcohols, and cellulose.
[068] Particularly preferred binders are Carbopol® Aqua 30, a latex of a copolymer
of acrylic acid and ethyl acrylate from Lubrizol; Klucel® L,
hydroxypropylcellluclose from Hercules, or Dispercoll™ U VP KA 8481 , a
polyester urethane copolymer dispersion from Bayer.
[069] The dispersion may also comprise a conductivity enhancing agent.
[070] Suitable conductivity enhancing agents are a linear, branched or cyclic
aliphatic C2-20 hydrocarbon or an unsubstituted or substituted aromatic C6-14
hydrocarbon, preferably an unsubstituted or substituted aromatic C-6, 10 or 4
hydrocarbon, or a pyran or a furan, said conductivity enhancing agent
comprising at least two hydroxy groups or at least one - C(=O)-X or -
C(=O)-NYZ group, wherein X denotes -OH and Y and Z independently of one
another each represent H or alkyl; or a heterocyclic compound containing at
least one lactam group.
[071] Preferred conductivity enhancing agents are e.g. N-methyl-2-pyrrolidone,
2-pyrrolidone, 1,3-dimethyl-2-imidazolidone, N,N,N,N' -tetramethylurea,
formamide, dimethylformamide and N,N-dimethylacetamide. Preferred
examples are sugar or sugar derivatives such as arabinose, saccharose,
glucose, fructose and lactose, or di- or polyalcohols such as sorbitol, xylitol,
mannitol, mannose, galactose, sorbose, gluconic acid, ethylene glycol, di- or
tri(ethylene glycol), 1, 1 ,1-trimethylol-propane, 1,3-propanediol, 1-,2-propanediol,
,5-pentanediol, 1,2,3-propanetriol, 1,2,4-butanetriol, ,2,6-hexanetriol,
or aromatic di- or polyalcohols such as resorcinol.
[072] Particularly preferred conductivity enhancing agents for use in the freezedried
composition, ink or aqueous or organic solvent solution or dispersion,
according to the present invention are: N-methyl-pyrrolidinone and diethylene
glycol.
[073] The dispersion may also comprise adhesion promoting compounds to
optimize the adhesion of coatings or patterns obtained with the dispersion on
various substrates. Preferred adhesion promoting compounds are
organosilane compounds, in particular alkoxysilane compounds such as
methyltrimethoxysilane, methyltriethoxysilane, dimethyldimethoxysilane,
propyltrimethoxysilane, isobutyltrimethoxysilane, phenyltrimethoxysilane,
n-octyltriethoxysilane, or glycidoxypropyl trimethyloxysilane all available from
Dow Corning.
Preparation of the Polymer or copolymer of a substituted or unsubstituted thiophene
[074] The above desribed polythiophene is preferably prepared in the presence of
a polyanion as described above. Such a preferred preparation method is
described in EP-A-440 957 and corresponding US5300575.
[075] Basically the preparation of polythiophene may proceed in the presence of
polymeric polyanion compounds, such as polystyrenesulfonic acid by
oxidative polymerisation of 3,4-dialkoxythiophenes or 3,4-alkylenedioxythiophenes
according to Formula IV:
Formula IV
wherein R 1 and R2 have the same meaning as R 1 and R2 in Formula III.
Preparation of a freeze dried composition of a conductive polymer and a polyanion
[076] The dispersion is preferably prepared starting from a freeze-dried
composition comprising a polymer or copolymer of a substituted or
unsubstituted thiophene and a polyanion.
[077] A preferred freeze-drying method is disclosed in EP-A 1309646.
[078] The first step in freeze-drying a product is to convert it into a frozen state.
During the freezing process the solvent (e.g. water) is preferably crystallized.
In the case of water, the formation of ice crystals results in a separation of
the solutes and the solvent. Then the ice crystals are removed by sublimation
under vacuum conditions. While the sublimation or primary drying process
removes most of the water from the frozen matrix, there can still be a
substantial amount, for example more than 5 wt %, of water present in the
freeze-dried composition. That remaining water may be removed by
desorption. Products freeze-dried at room temperature typically have a water
content of 15 to 20% by weight. Further drying of the freeze-dried product in
a vacuum drying cupboard at 110°C and a drying cupboard at 110°C may
results in products which are more difficult to disperse.
[079] The freeze-dried composition may be present in the form of a dry, spongy,
woolly powder, a concentrated dispersion or a paste. In a particulcar
preferred embodiment the freeze-dried composition is present as pellets.
[080] The freeze-dried compositon may contain, in addition to the conductive
polymer and the polyanion a surfactant and/or dispersant.
Method to prepare the dispersions of a conductive polymer and a polyanion
[081] The method according to the present invention of preparing a substantially
water free dispersion of a conductive polymer and a polyanion comprises the
steps of:
- redispersing a freeze dried composition comprising a conductive polymer
and a polyanion in a non-aqueous medium;
- adding a compound having an acid sensitive functional group selected from
the group consisting of a ketal, an acetal, an aminal, a hemi-ketal, a hemiacetal,
a hemi-aminal, a thioacetal, an amide acetal, an orthoester, an
orthoether, an enolester, an enolether, and an enolamine.
[082] Preferably a surfactant and/or a dispersant as described above are also
added to prepare the dispersion. The amount of the surfactant and/or the
dispersant is preferably between 0.05 and 10 wt %, more preferably between
0.1 and 5.0 wt %, most preferably between 0.5 and 2.5 wt % relative to the
total weight of the dispersion.
[083] The amount of the freeze dried composition comprising a conductive polymer
and a polyanion is preferably between 0.05 and 10 wt %, more preferably
between 0.1 and 5.0 wt %, most preferably between 0.5 and 2.5 wt % relative
to the total weight of the dispersion.
[084] To prepare the non-aqueous dispersion, well known dispersion technologies
and devices may be used. Good results, i.e. homogeneous dispersions, were
obtained with dissolvers from Disperlux, with Ultra-Turrax® systems from
IKA.
[085] Also ball-milling and bead-milling devices may be used to obtain
homogeneous non-aqeous dispersions. Good results were also obtained with
a microfluidizer® from Microfluidics.
[086] The amount of water present in the freeze dried composition, or in the
redispersed freeze dried composition, may be determined to optimize the
amount of the compound having an acid sensitive funcitonal group.
Preferably an excess of the compound having an acid sensitive functional
group relative to the water present in the dispersion is used.
[087] The amount of the compound having an acid sensitive functional group is
preferably from 0.5 to 5 wt %, more preferably from 1.0 to 2.5 wt % relative to
the total weight of the dispersion.
Conductive layers or patterns
[088] Conductive layers or patterns may be obtained by applying the dispersion
according to the present invention on a substrate.
[089] The conductive layers or patterns are prepared by a method comprising the
steps of applying the dispersion as defined above on a substrate followed by
a drying step.
[090] The conductive layers or patterns may be applied by inkjet printing or by any
conventional printing technique such as flexography, offset, gravure or
screen printing or by any conventional coating technique such as spray
coating, blade coating, or slot die coating.
[091] The conductive layers or patterns may be used in various electronic devices
or parts of such electronic devices as for example OLED, OPV, Dye
Sensitized Solar Cell (DSSC) or a solar cell based on Perovskites.
Examples
Materials
[092] All materials used in the following examples were readily available from
standard sources such as ALDRICH CHEMICAL Co. (Belgium) and ACROS
(Belgium) unless otherwise specified. The water used was deionized water.
[093] Ethomeen C25: commercially available from AKZO NOBEL.
[094] Orgacon Dry Pellets: commercially available from Agfa Gevaert NV.
[095] Hydranal® Composite 5: commercially available fropm Sigma-Aldrich.
[096] DMP: 2,2-dimethoxypropane commercially available from Sigma-Aldrich.
[097] TEOA: triethyl orthoacetate commercially available from Sigma-Aldrich.
[098] TMOA: trimethyl orthoacetate commercially available from Sigma-Aldrich.
Measurement Methods
Determination of the water content
[099] A volumetric Karl Fischer titration was used to determine the water content of
the dispersion. Hydranal® Composite 5 was used as Karl Fischer reagent.
Determination of the SER
[0100] The surface resistance SER was measured using a two point probe method.
Determination of the Haze
[0101] The haziness of the samples was measured by means of a Haze-Gard plus
from Byk-Gardner.
Determination of the Visual Light Transmission (VLT)
[0102] The transmittance of the samples was measured by means of a Haze-Gard
plus Byk-Gardner.
Preparation PEDT/PSS dispersions DISP-01 and DISP-02
[0103] 392g of isopropanol (Acros, 99+ extra pure), was disposed in a stainless
steel vessel. Subsequently 4g of a polymeric dispersing agent (ethomeen
C25) was added and stirred until complete dissolution. Finally, 4g of Orgacon
Dry pellets were added while stirring the mixture. The obtained mixture was
then submitted to a Disperlux high shear treatment during 30 minutes.
Finally, a finishing step was performed via a Netzsch milling process during
54 minutes resulting in the dispersion DISP-01 .
[01 04] DISP-02 was prepared by adding at room temperature 1.34 g of TEOA to
1.3 g of DISP-01 under stirring for a few minutes.
[0105] The water content of DISP-01 and DISP-02, measured as described above,
is shown in Table 1.
Table 1
* below the detection limit of the method used
[0106] It is clear from Table 1 that the addition of a compound having an acid
sensitive functional group according to the present invention, such as triethyl
orthoacetate, results in a substantially water free dispersion of PEDOT/PSS
in a non-aqueous medium.
Preparation PEDT/PSS dispersions DISP-03 and DISP-1 1
[0107] DISP-03 to DISP-1 1 were prepared by first bubbling N2 through 100 g of
DISP-01 in a vessel for 30 minutes. Then, after adding the compounds of
Table 2 the vessels were sealed and the resulting dispersions stirred for
another 60 minutes.
[0108] The dispersions were then coated on a (subbed) PET support (thickness =
125 m h ) with a bar coater at a wet coating thickness of 40 mhh and dried at
130 °C for 6 minutes.
[0109] The VLT, HAZE and SER, measured as described above are given in
Table 2.
Table 2
* compound having acid sensitive functional group.
** % relative to the total weight of the dispersion
[01 10] It is clear from the results shown in Table 2 that adding a compound having
an acid sensitive functional group according to the present invention to a
non-aqueous dispersion of PEDOT/PSS does not have a significantly
negative influence on the electrical and optical properties of coatings
obtained with the dispersions.

Claims
1. A dispersion of a conductive polymer and a polyanion in a non-aqueous medium
further comprising a compound having an acid sensitive functional group selected
from the group consisting of a ketal, an acetal, an aminal, a hemi-ketal, a hemiacetal,
a hemi-aminal, a thioacetal, an amide acetal, an orthoester, an orthoether,
an enolester, an enolether, and an enolamine.
2. The dispersion according to claim 1 wherein the compound having an acid
sensitive functional group is selected from the group consisting of a ketal, an
acetal and an orthoester.
3. The dispersion according to claims 1 or 2 wherein the compound having an acid
sensitive functional group is an orthoester according to Formula I ,
Formula I
wherein
Ra, Rb, Rc independently represent a substituted or unsubstituted alkyl
group, a substituted or unsubstituted alkenyl group, a substituted or
unsubstituted alkynyl group, a substituted or unsubstituted aralkyl group, a
substituted or unsubstituted aryl group, a substituted or unsubstituted
heteroaryl group or a substituted or unsubstituted heterocyclic group;
Rd represents a hydrogen, a substituted or unsubstituted alkyl group, a
substituted or unsubstituted alkenyl group, a substituted or unsubstituted
alkynyl group, a substituted or unsubstituted aralkyl group, a substituted or
unsubstituted aryl group, a substituted or unsubstituted heteroaryl group or a
substituted or unsubstituted heterocyclic group; or
Ra together with Rb or Rc may represent the necessary atoms to form a
substituted or unsubstituted ring; or
Rb together with Rc may represent the necessary atoms to form a
substituted or unsubstituted ring; or
Rd together with Ra, Rb or Rc may represent the necessary atoms to form a
substituted or unsubstituted ring.
The dispersion according to claim 3 wherein Ra, Rb, Rb and Rd are substituted
or unsubstituted C1-C6 alkyl groups.
The dispersion according to any of the preceding claims wherein the compound
having an acid sensitive functional group forms upon reaction with water reaction
products having a boiling point Bp at atmospheric pressure below 200 °C.
The dispersion according to any of the preceding claims wherein the conductive
polymer is a polymer or copolymer of a substituted or unsubstituted thiophene.
The dispersion according to claim 6 wherein the polymer of a substituted or
unsubstituted thiophene is represented by Formula III,
Formula III
wherein
1 < n < 10 000;
and R independently represents hydrogen, a substituted or
unsubstituted C1-C4 alkyl group, or together form a substituted or
unsubstituted C1-C4 alkylene group or a substituted or unsubstituted C3-C10
cycloalkylene group.
8. The dispersion according to any of the preceding claims wherein the polyanion is
poly(styrenesulfonate).
9. The dispersion according to any of the preceding claims wherein the non
aqueous medium is selected from the group consisting of ethanol, acetone,
methyl ethyl ketone (MEK), ethylacetate, isopropylalcohol ( IPA), toluene,
butylacetate, propylacetate, and mixtures thereof.
10. The dispersion according to any of the preceding claims further comprising a
polyoxyethylene alkylamine dispersant.
11. A method for preparing a substantially water free dispersion of a conductive
polymer and a polyanion comprising the steps of:
- redispersing a freeze dried composition comprising a conductive polymer and
polyanion in an non-aqueous medium;
- adding a compound having an acid sensitive functional group selected from th
group consisting of a ketal, an acetal, an aminal, a hemi-ketal, a hemi-acetal, a
hemi-aminal, a thioacetal, an amide acetal, an orthoester, an orthoether, an
enolester, an enolether, and an enolamine.
12. The method according to claim 1 wherein the amount of the compound having
an acid sensitive functional group is from 0.5 to 5.0 wt % relative to the total
weight of the dispersion.
13. A coating or pattern obtained by applying a dispersion as defined in any of the
claims 1 to 10 on a substrate.
14. An electronic device comprising the coating or pattern as defined in claim 13.
15. The electronic device according to claim 14 being an OLED, OPV, Dye
Sensitized Solar Cell (DSSC) or a solar cell based on Perovskites.