DESC:FIELD
The present disclosure relates to an anti-smudge coating and a process for preparation thereof.
DEFINITIONS
As used in the present disclosure, the following terms are generally intended to have the meaning as set forth below, except to the extent that the context in which they are used to indicate otherwise.
Slippery liquid-infused porous surfaces (SLIPS) refer to a class of surfaces/coatings that have excellent liquid repellent properties. In such slippery surfaces, a liquid lubricant is stabilized by capillary forces within a porous or nanostructured solid, resulting in a chemical homogeneous and atomically smooth liquid-liquid interface between the surface and the foreign liquid.
Solid/Dry slippery interface: refers to a class of surfaces/coatings that have excellent liquid (water and oil) repellent properties. Such solid/dry slippery surfaces are lubricant-free, dry and relatively smooth (less than 10 nanometer) interface.
BACKGROUND
The background information herein below relates to the present disclosure but is not necessarily prior art.
Synthesis of durable and scalable anti-smudge coatings are important avenue for various potential applications related to health and environments, where both the aqueous phase and organic phase/ liquids are readily slipped on the tilted non-adhesive interfaces.
Conventionally, slippery liquid infused porous surfaces (SLIPS) are mostly synthesized by associating fluorinated molecules which are known to have severe health and environmental hazards. Moreover, some weak chemical bonding and interactions are engaged in developing appropriate base layer to host liquid lubricants. More importantly, the reported polymeric SLIPS are inappropriate to sustain harsh settings, and physically abraded interfaces are likely to fail in displaying antifouling property at practically relevant scenarios.
Recently, liquid lubrication free, dry and solid slippery surfaces have gained widespread attention due to its enhanced stability over SLIPS. However, the reported solid slippery surfaces till date suffer from limitations such as tedious fabrication procedure and use of expensive chemicals such as use of fluorinated molecules which have adverse health and environmental affects, extremely thin polymeric coating that is susceptible under practical settings; and coatings fabricated out of materials that lack long term durability.
Therefore, there is felt a need to provide an anti-smudge coating and a process for preparation thereof, which mitigates the drawbacks mentioned herein above.
OBJECTS
Some of the objects of the present disclosure, which at least one embodiment herein satisfies, are as follows:
An object of the present disclosure is to ameliorate one or more problems of the prior art or to at least provide a useful alternative.
Another object of the present disclosure is to provide an anti-smudge coating.
Yet another object of the present disclosure is to provide an anti-smudge coating that is fluorine free.
Still another object of the present disclosure is to provide a process for the preparation of an anti-smudge coating that is simple, economic and environment friendly.
Other objects and advantages of the present disclosure will be more apparent from the following description, which is not intended to limit the scope of the present disclosure.
SUMMARY
The present disclosure relates to an anti-smudge coating comprising at least one acrylate, at least one hydrophobic polymer, at least one amine and optionally at least one lubricating agent. The coating when applied on a substrate obtains one of a liquid-infused-slippery interface and a dry-slippery interface.
In an embodiment, the anti-smudge coating for obtaining the liquid-infused-slippery interface on the substrate comprises at least one acrylate, at least one hydrophobic polymer, at least one amine and at least one lubricating agent.
The present disclosure further relates to a process for the preparation of an anti-smudge coating for obtaining the liquid-infused-slippery interface on the substrate. The process comprises the step of mixing predetermined amounts of at least one acrylate and at least one hydrophobic polymer in a fluid medium under stirring for a time period in the range of 5 minutes to 25 minutes to obtain a solution. The solution is spray deposited on a substrate followed by air drying to obtain a coated substrate. The coated substrate is modified with at least one amine to obtain a modified coated substrate. The modified coated substrate is infused with at least one lubricating agent to obtain the anti-smudge coating, wherein the anti-smudge coating has the liquid-infused-slippery interface.
In another embodiment, the anti-smudge coating for obtaining the dry-slippery interface on the substrate comprises at least one acrylate, at least one hydrophobic polymer and at least one amine.
The present disclosure further relates to a process for the preparation of an anti-smudge coating for obtaining the dry-slippery interface on the substrate The process comprises the step of mixing predetermined amounts of at least one acrylate and at least one hydrophobic polymer and at least one amine in a fluid medium under stirring for a time period in the range of 5 minutes to 25 minutes to obtain a solution. The solution is applied on a substrate to obtain a coated substrate. The coated substrate is dried at a predetermined temperature for a predetermined time period to obtain the anti-smudge coating, wherein the anti-smudge coating has the solid slippery interface on the substrate.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWING
The present disclosure will now be described with the help of the accompanying drawing, in which:
Figure 1A-C illustrates the chemical structures of (A) branched polyethylenimine (BPEI); (B) dipentaerythritol penta-acrylate (5Acl); (C) octadecylamine (ODA);
Figure 1D-G illustrates Field Emission Scanning Electron Microscopy (FESEM) images of the coated substrate (unmodified) at (D) low and (E) high magnification; (F-G) Contact angle images of the water droplet on the (F) coated substrate (unmodified) after infusion with silicone oil and on the (G) ODA modified porous polymeric coating;
Figure 1H-M illustrates the digital images (H-J) and contact angle images (K-M) of the stagnant water droplet on the coated substrate (unmodified) tilted at 5° after infusion with silicone oil;
Figure 1N-S illustrates digital images (N-P) and contact angle images (Q-S) of the sliding water droplet on the ODA modified SLIPS (tilted at 5°);
Figure 1T illustrates ATR-FTIR spectra (black) of the coated substrate (unmodified) and ATR-FTIR spectra (red) of the ODA modified porous polymeric coating;
Figure 2A-R illustrates the digital images of the chemically contaminated aqueous droplet sliding from the surface of the SLIPS, including acidic water droplet (A-C), alkaline water droplet (D-F), sea water droplet (G-I), hot coffee droplet (J-L), cold cola droplet (M-O), and milk droplet (P-R);
Figure 3A-C illustrate the digital images of the various physical abrasions including knife scratch test (A-C), sand paper abrasion test (D-F), and adhesive tape test (G-I);
Figure 3J illustrates a plot depicting the water sliding angle on the synthesized SLIPS after exposure to various chemically contaminated aqueous phases and UV radiation for 7 days;
Figure 4A illustrates the chemical structures of dipentaerythritol penta-acrylate, Poly{dimethylsiloxane-co-(3-aminopropyl)methylsiloxane} and [3-(2-Aminoethylamino)propyl] trimethoxylsilane;
Figure 4B-E illustrate the contact angle images of water droplet (B) and oil droplet (C) on a bare glass slide; (D-E) contact angle images of water droplet (D) and oil droplet (E) on an omniphobic anti-smudge coating;
Figure 4F-M illustrate the digital images (F-G, J-K) and contact angle images (H-I, L-M) of the spreading of water droplets (F-I) and crude oil droplets (J-M) on a bare glass slide titled at an angle of 15°;
Figure 4N-Y illustrate the digital images (N-P, T-V) and contact angle images (Q-S, W-Y) of the sliding of water droplets (N-S) and crude oil droplets (T-Y) from the surface of the omniphobic anti-smudge coating tilted at an angle of 15°;
Figure 5A illustrates ATR-FTIR spectra of dipentaerythritol penta-acrylate (red), the FTIR-ATR spectra of the omniphobic coating solution at t=0 min (blue) and after 6h of heat treatment (80°C) (black);
Figure 5B illustrates AFM analysis of the synthesized omniphobic anti-smudge coating;
Figure 5C illustrates UV-Vis spectral analysis comparing the transparency of a bare glass slide (red) with the omniphobic slippery glass slide (black);
Figures 5D-H illustrate the EDX spectra (D) and mapping analysis depicting the uniform presence of Si (E), O (F), C (G), N (H) throughout the omniphobic anti-smudge coating;
Figure 6A-O illustrate the digital images of the various liquid droplets sliding from the surface of the omniphobic anti-smudge coating including petrol (A-C), kerosene (D-F), toluene (G-I), tetrahydrofuran (J-L) and ethanol (M-O);
Figure 7A-L illustrate the digital images of the various physical abrasions including finger wiping and tissue paper wiping test (A-F) and adhesive tape test (G-L);
Figure 8A illustrate a plot of the crude oil (red) and water (black) sliding angle from the surface of the omniphobic anti-smudge coating after exposure to distilled water, various chemically contaminated aqueous phases including acidic water (pH 1), basic water (pH 13), artificial sea water, river water and UV radiation for 7 days; and
Figure 9A-F illustrate the digital images illustrating the sliding of water droplets (A-C) and oil droplets (D-F) respectively from the surface of stainless steel that is coated with the omniphobic anti-smudge coating.
DETAILED DESCRIPTION
Embodiments, of the present disclosure, will now be described with reference to the accompanying drawing.
Embodiments are provided so as to thoroughly and fully convey the scope of the present disclosure to the person skilled in the art. Numerous details are set forth, relating to specific components, and methods, to provide a complete understanding of embodiments of the present disclosure. It will be apparent to the person skilled in the art that the details provided in the embodiments should not be construed to limit the scope of the present disclosure. In some embodiments, well-known processes, well-known apparatus structures, and well-known techniques are not described in detail.
The terminology used, in the present disclosure, is only for the purpose of explaining a particular embodiment and such terminology shall not be considered to limit the scope of the present disclosure. As used in the present disclosure, the forms "a,” "an," and "the" may be intended to include the plural forms as well, unless the context clearly suggests otherwise. The terms "comprises," "comprising," “including,” and “having,” are open ended transitional phrases and therefore specify the presence of stated features, integers, steps, operations, elements, modules, units and/or components, but do not forbid the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. The particular order of steps disclosed in the method and process of the present disclosure is not to be construed as necessarily requiring their performance as described or illustrated. It is also to be understood that additional or alternative steps may be employed.
The anti-smudge coating is of following types:
1) slippery liquid infused porous substrate (SLIPS); and
2) solid/dry slippery interface.
SLIPS: The SLIPS are fabricated mostly by associating hazardous fluorinated molecules. Often, the physical and chemical durability of the conventional SLIPS does not qualify for application at real life settings. Mostly, the soft polymeric interfaces that are used as base layers for reported SLIPS are highly susceptible for physical abrasions and became inappropriate for long run use.
Solid/Dry Slippery Interface: The solid and dry slippery surfaces are fabricated by exploiting polymeric brushes to yield extremely thin monolayer coatings ranging from 2-10 nm that are highly susceptible to physical damage. Fluorinated moieties are further used to yield superior water and oil repellent coatings but the severe impact of fluorinated molecules on health and environment remain a major concern. Moreover, the fluorinated molecules are also expensive. In most of the commercially known substrates, the coatings are made of complex and composite materials.
Solid slippery surfaces till date suffer from limitations such as tedious fabrication procedure and use of expensive chemicals; use of fluorinated molecules which have adverse health conditions and environmental issues; extremely thin polymeric coatings that is susceptible under practical settings; coatings fabricated out of hybrid materials that lack long term durability.
The present disclosure provides an anti-smudge coating and a process for preparation thereof. Particularly, the present disclosure provides an anti-smudge coating that is fluorine free.
In an aspect, the present disclosure provides an anti-smudge coating comprising at least one acrylate, at least one hydrophobic polymer, at least one amine and optionally at least one lubricating agent. The coating when applied on a substrate, obtains one of a liquid-infused-slippery interface and a dry-slippery interface.
In one embodiment of the present disclosure, the anti-smudge coating for obtaining the liquid-infused-slippery interface on the substrate comprises at least one acrylate, at least one hydrophobic polymer, at least one amine and at least one lubricating agent.
In accordance with the present disclosure, the acrylate is dipentaerythritol penta-acrylate, the hydrophobic polymer is branched polyethylenimine, the amine is octadecylamine and the lubricating agent is silicon oil.
In another embodiment of the present disclosure, the anti-smudge coating for obtaining the dry-slippery interface on the substrate comprises at least one acrylate, at least one hydrophobic polymer and at least one amine.
In accordance with the present disclosure, the acrylate is dipentaerythritol penta-acrylate, the hydrophobic polymer is poly[dimethylsiloxane-co-(3-aminopropyl)methylsiloxane] and the amine is [3-(2-Aminoethylamino) propyl] trimethoxysilane.
In the present disclosure, a fluorine free, facile and scalable approach has been adopted to design a polymer based but hard slippery interface with high physical and chemical durability. A highly stable and fluorine free covalently cross-linked network is built on the substrate adopting a scalable process to obtain a transparent omniphobic solid slippery interface that can extremely repel both water and oil phase. This omniphobic surface can sustain prolonged physical and chemical damage thus, extending its applications to real life scenarios.
In another aspect, the present disclosure provides a process for the preparation of the anti-smudge coating for obtaining a slippery liquid infused interface on a substrate. The process comprises the following steps:
In a first step, predetermined amounts of at least one acrylate and at least one hydrophobic polymer are mixed in a fluid medium under stirring for a time period in the range of 5 minutes to 25 minutes to obtain a solution.
The fluid medium is at least one selected from the group consisting of methanol, ethanol and toluene. In an exemplary embodiment, the fluid medium is methanol.
In the next step, the solution is spray deposited on a substrate followed by air drying to obtain a coated substrate.
The substrate is selected from glass, aluminium foil, stainless steel, wood, plastic and paper. In an exemplary embodiment, the substrate is glass.
Further, the coated substrate is modified with at least one amine to obtain a modified coated substrate. In an embodiment of the present disclosure, the modified coated substrate is dried and thoroughly washed with ethanol and kept for drying.
In accordance with the present disclosure, a weight ratio of the acrylate to the hydrophobic polymer to the amine is in the range of 1:0.1:0.01 to 1:0.2:0.05. In an exemplary embodiment, the weight ratio of the acrylate to the hydrophobic polymer to the amine is 1:0.16:0.038.
Finally, the modified coated substrate is infused with at least one lubricating agent for obtaining the slippery liquid infused interface on the substrate.
In accordance with the present disclosure, the porous polymeric coating has a thickness in the range of 1.5 µm to 1.6 µm.
In yet another aspect, the present disclosure provides a process for the preparation of the anti-smudge coating for obtaining a solid slippery interface on a substrate. The process comprises the following steps:
In a first step, predetermined amounts of at least one acrylate, at least one hydrophobic polymer and at least one amine are mixed in a fluid medium under stirring for a time period in the range of 5 minutes to 25 minutes to obtain a solution.
The fluid medium is at least one selected from the group consisting of methanol, ethanol and toluene. In an exemplary embodiment, the fluid medium is toluene.
In accordance with the present disclosure, a weight ratio of the acrylate to the hydrophobic polymer to the amino silane is in the range of 1:1.1:0.5 to 1:1.2:1. In an exemplary embodiment, the weight ratio of the acrylate to the hydrophobic polymer to the amine is 1:1.16:0.72.
In the next step, the solution is applied on a substrate to obtain a coated substrate.
The substrate is selected from glass, aluminium foil, stainless steel, wood, plastic and paper. In an exemplary embodiment, the substrate is glass.
Finally, the coated substrate is dried in an oven at a predetermined temperature for a predetermined time period to obtain the anti-smudge coating for obtaining the solid slippery interface on the substrate.
In accordance with the present disclosure, the predetermined temperature is in the range of 70 °C to 100 °C. In an exemplary embodiment, the predetermined temperature is 80 °C.
In accordance with the present disclosure, the predetermined time period is in the range of 4 hours to 8 hours. In an exemplary embodiment, the predetermined time period is 6 hours.
In accordance with the present disclosure, the anti-smudge coating has a thickness in the range of 90 µm to 125 µm.
In an embodiment of the present disclosure, the anti-smudge coating having slippery liquid-infused porous surfaces (SLIPS), first forms a porous polymeric coating and after lubrication, the wet interface becomes slippery to beaded water droplet. In case of SLIPS, without lubrication the porous polymeric coating is not slippery.
In another embodiment of the present disclosure, the anti-smudge coating having solid/dry slippery interface is smooth and dry, which is slippery to both the beaded water and oils droplets.
The present disclosure provides a new synthetic process of fluorine free and scalable lubricant infused slippery interface following a facile spray coating process, where the beaded water droplets easily slide off at a tilting angle of 5°. Further, the present disclosure provides another facile, economical and scalable fabrication procedure to obtain a stable omniphobic solid/dry slippery surface that is antifouling for both aqueous solutions and different organic liquid phases. The fabricated transparent omniphobic surface is characterized by a smooth and defect free morphology. The slippery interfaces are capable of withstanding severe physical and chemical harsh environments which makes it a highly potential candidate for applications at practically relevant settings.
The present disclosure provides an anti-smudge coating that is appropriate for various important applications including anti-biofouling coatings, anti-smudge coatings for glasses in buildings or automobiles and touch screen displays, anti-icing coatings, anti-corrosion, easy transport of viscous liquid and water harvesting.
The foregoing description of the embodiments has been provided for purposes of illustration and not intended to limit the scope of the present disclosure. Individual components of a particular embodiment are generally not limited to that particular embodiment, but, are interchangeable. Such variations are not to be regarded as a departure from the present disclosure, and all such modifications are considered to be within the scope of the present disclosure.
The present disclosure is further described in light of the following experiments which are set forth for illustration purpose only and not to be construed for limiting the scope of the disclosure. The following experiments can be scaled up to industrial/commercial scale and the results obtained can be extrapolated to industrial scale.
EXPERIMENTAL DETAILS
Martials Required: Branched, polyethelenimine (BPEI, MW~800), dipentaerythritol penta-acrylate (5-Acl, MW~ 524.51g/mol), Poly[dimethylsiloxane-co-(3-aminopropyl)methylsiloxane], [3-(2-Aminoethylamino)propyl]trimethoxysilane, silicon oil (AR 20), octadecylamine (97%), rhodamine 6G were obtained from Sigma Aldrich (Bangalore India).
Sodium Chloride, magnesium chloride, calcium chloride, magnesium sulphate, sodium hydroxide were purchased from Emparta (Merck Specialties Private Limited). Hydrochloric acid (HCl) was purchased from Fisher Scientific (Hyderabad India).
Methanol and tetrahydrofuran was procured from FINAR. Toluene was procured from RANKEM. Ethanol was procured from Changshu Hongsheng Fine Chemical Co. Ltd. Microscope slides acquired from Zeinth India. Spray Bottle (Capacity~100ml, nozzle Diameter ~400 µm) was purchased from Amazon India.
Adhesive tape, paper, Sandpaper (300 grit), tissue paper were procured from local stationary shop. Kerosene and petrol was procured from an Indian Oil Petrol Pump, Guwahati. Crude oil was procured from Oil India Refinery, Assam. Glass slides were thoroughly washed using ethanol prior to experiments.
Glass vials that were used for preparing the polymer solutions were washed with acetone and ethanol prior to use. The contact angle measurements were taken using KRUSS Drop Shape Analyser-DSA25 instrument with an automatic liquid dispenser at ambient conditions. Advancing and receding water contact angles were measured at three to four different locations for each sample. Field Emission Scanning electron microscope (FESEM) images were acquired using Sigma Carl Zeiss scanning electron microscope (samples were coated with a thin layer of gold prior to imaging). FTIR-ATR spectra were recorded using PerkinElmer instrument at ambient condition and the sample was grinded with KBr to prepare the pellet before analysis. Digital pictures were acquired using a canon power shot SX420 IS digital camera. Surface profilometer (Veeco , Dektak 150) was used for measuring the thickness of the coating.
Experiment 1:
A. Process for the preparation of the anti-smudge coating, wherein the coating has slippery liquid infused interface in accordance with the present disclosure
Dipentaerythritol penta-acrylate (1.325 g in 10 ml methanol) and branched polyethylenimine (low molecular weight (Mn)= 600 Da) (0.21g in 3 ml methanol) were mixed under stirring for 15 minutes to obtain a solution. The solution (13 ml) was manually spray deposited on a glass substrate (area of 18.75 cm2) from a distance of 20 cm, followed by air drying to obtain a coated substrate. The coated substrate was post-modified with octadecylamine (ODA) (5 mg/ml) in ethanol (10 ml required for dipping one glass slide of area 18.75 cm2) and was kept for hydrophobic modification for 6 hours to obtain a modified coated substrate, wherein a 1,4-conjugate addition reaction takes place between the primary amino group of octadecyamine and acrylate groups of dipentaerythritol penta-acrylate. The modified coated substrate was thoroughly washed with ethanol and air dried to obtain a porous, hydrophobized polymeric coated substrate (7.5 cm x 2.5 cm). The porous, hydrophobized polymeric coated substrate was infused with silicon oil (150 µl) and was kept vertically for 10 minutes to remove the excess oil to obtain an anti-smudge coating having the slippery liquid infused interface on the substrate. The slippery property of the anti-smudge coating was examined by a visual inspection and sliding angle measurement.
B. Tests and Characterization:
Figure 1 represents the chemical structure of branched polyethylenimine, BPEI (A), dipentaerythritol penta-acrylate, (5Acl) (B), octadecylamine, ODA (C) that were exploited to obtain the anti-smudge coating having slippery liquid infused interface on the substrate.
The facile and catalyst-free 1,4-conjugate addition reaction between the amine and acrylate groups leads to the formation of porous, hydrophobized polymeric coated substrate. Field Emission Scanning Electron Microscopy (FESEM) images of the spray deposited coated substrate (unmodified) revealed the random and covalent aggregation of the polymeric nanocomplexes resulting in a porous, granular topography as shown in Fig. 1 (D-E) where the water droplet beaded with contact angle ~78° after infusion of lubricant (Fig. 1F). The beaded aqueous droplet on the coated substrate (unmodified) remained stagnant on tilting at 5° and thus, was incapable of displaying slippery property even after infusion with silicone oil (lubricant) since the water droplet can easily replace the infused lubricant (Fig. 1H-M).
Therefore, to obtain slippery liquid infused interface, hydrophobization of the coated substrate was carried out by exploiting the residual acrylate groups to react with an amine containing hydrophobic molecule. The ‘reactive’ polymeric coating was hydrophobized through post-covalent functionalization with octadecylamine through 1,4-conjugate addition reaction (denoted as ODA treated) where the water droplet beaded with contact angle ~82° after lubricant infusion (Fig. 1G). The beaded aqueous phase (colored red for visual inspection) readily slipped away on tilting (at 5°) the lubricant infused ODA treated polymeric coating as shown in Fig. 1N-S. The presence of a porous network aided in the stabilization of the infused lubricant.
The ATR-FTIR analysis confirmed the presence of ‘reactive’ residual acrylate groups in the spray deposited polymeric coating, where the peaks (black) at 1730 cm-1 and 1410 cm-1 corresponds to the vibrational stretching of carbonyl and symmetric stretching of C-H bond of ß-carbon of the vinylic group. The intense peak at 1410 cm-1 depleted significantly on post functionalization with the hydrophobic alkylamine i.e. octadecylamine with respect to the carbonyl stretching (1730 cm-1) as shown in Fig. 1T (red), thus confirming the successful conjugate addition reaction between the residual acrylates and amine containing small molecule.
The anti-smudge coating having slippery liquid infused interface prepared by the process of the present disclosure is referred as SLIPS (slippery liquid infused porous substrate). The synthesized SLIPS was found to be anti-fouling towards various complex aqueous phases including acid water (pH 1), alkaline water (pH 13), milk, hot coffee (80°C) and cold cola (5°C) (Fig. 2A-R).
C. Physical and Chemical Durability Tests of the SLIPS:
The synthesized SLIPS was found to be highly physically and chemically durable. Some standard and severe abrasive tests were performed on the hydrophobized polymeric coating for investigating the impact of physical abrasions on the embedded slippery property as briefly explained below.
(i) Knife Scratch Test: Random scratches were made on one half of the hydrophobized polymeric coated substrate using a sharp-edged knife multiple times and thereafter, the water sliding behavior on the randomly scratched interface was examined after infusion with silicon oil. It was found that the slippery property remained intact even after incurring the severe scratches as shown in Fig. 3A-C.
(ii) Sand Paper Abrasion: In this test, an abrasive sand paper (grit no-400, 3.5 cm x 2.5 cm) fixed onto a glass slide was placed on one half portion of the hydrophobized polymeric coated substrate (3.5 cm x 2.5 cm) with a 500 g load at top and rubbed in back and forth motion for 50 times as shown in Fig. 3D. Thereafter, this hydrophobized polymeric coated substrate with its one half portion abraded was infused with silicon oil to investigate the water sliding property. It was found that the embedded slippery property remained unperturbed as the water droplet easily slid down the sand paper abraded slippery interface at 5° tilting angle (Fig. 3E-F).
(iii) Adhesive Tape Test: In this test, an adhesive tape was fixed on one half of the ODA-treated polymeric coating (3.5 cm x 2.5 cm) with 500 g load on top to ensure uniform contact between the adhesive tape and the hydrophobized polymeric coated substrate (Fig. 3G). Subsequently, after 5 minutes the adhesive tape was peeled from the coating and thereafter, the slippery property on the freshly exposed interface was examined thoroughly after infusion with silicon oil. During the process of adhesive tape peeling, the top portion of the porous polymeric coating was fractured randomly, but the slippery property after infusion of lubricant remained unaltered even after 50 times of abrasion as shown in Fig. 3H-I.
(iv) Chemical Durability Tests: For chemical durability tests, silicone oil infused hydrophobized polymeric coated substrate were submerged in different aqueous environments i.e. acidic water (pH=1), alkaline water (pH=13), river water, artificial sea-water and water exposed to UV radiation (at ?max = 254 and 365 nm) for 7 days. Digital images and sliding angle measurements were acquired after 7 days to examine the sustainability of the SLIPS. The water sliding characteristic behavior on the hydrophobized polymeric coated substrate after infusion with silicone oil remained unperturbed even after prolonged exposure to various harsh aqueous chemical environments including extremes of pH (1 and 13), river (Brahmaputra, Assam India) water, artificial sea water and continuous UV radiation as shown in Fig. 3J.
(v) Heat treatment test: Further, the hydrophobized polymeric coated substrate after infusion with silicone oil was exposed to different temperatures i.e. 50°C, 75°C and 120°C for 24 hours and it was observed that the water sliding angles showed slight variation with the increase in temperature as tabulated in Table 1.
Table 1: Water sliding angle before and after heat treatment of SLIPS
Coating Liquid Sliding angle (°)
(Before experiment) Sliding angle (°)
(After 24 h of heat treatment)
50 °C 75 °C 120 °C
SLIPS H2O 5 5 6 15
At very elevated temperature (i.e. 120°C), the chemical compatibility between the infused lubricant (i.e. silicon oil) and the matrix is perturbed and the SLIPS became more adhesive, eventually the sliding angle of the beaded water droplet was increased from 5° to 15°.
Advantages of the SLIPS of the present disclosure over the conventional coatings: The synthesis approach of SLIPS of the present disclosure is catalyst-free, facile and scalable without requiring any expensive fluorinated chemicals that has adverse effect on the environment. Further, the physical and chemical durability of the SLIPS of the present disclosure are superior than most of the conventional materials and thus, making it capable of performing under various challenging settings.
Experiment 2:
A. Process for the preparation of the anti-smudge coating, wherein the anti-smudge coating has a solid/dry slippery interface in accordance with the present disclosure:
Dipentaerythritol penta-acrylate (0.1325g), [3-(2-aminoethylamino)propyl]trimethoxysilane (150 µl) and poly[dimethylsiloxane-co-(3-aminopropyl)methylsiloxane] (100 µl) were mixed in toluene (5 ml) under stirring for 10 minutes to obtain a solution. The solution was applied on a glass slide by the doctor blade method to obtain a coated substrate. The coated substrate was dried in an oven for 6 h at 80°C to obtain an anti-smudge coating having the solid/dry slippery interface. The slippery property of the anti-smudge coating was examined by visual inspection and sliding angle measurement.
B. Tests and Characterization:
Figure 2 A represents the chemical structure of dipentaerythritol penta-acrylate (5Acl), Poly{dimethylsiloxane-co-(3-aminopropyl)methylsiloxane} (PDMS) and [3-(2-Aminoethylamino)propyl] trimethoxylsilane (AEAPTMS) that were exploited to obtain the anti-smudge coating having omniphobic solid slippery interface.
The static contact angles of water and oil droplets on the bare glass slide (Fig. 4B-C) and after coating the glass slide with the omniphobic anti-smudge coating (Fig. 4D-E) is shown in Fig. 4B-E. As shown in Fig. 4F-M, the water droplets (Fig. 4F-I) and crude oil droplets (Fig. 4J-M) tend to spread on a bare glass slide on tilting the substrate at an angle of 15°. However, the glass slide that was coated with the omniphobic anti-smudge coating could successfully allow the water droplets (Fig. 4N-S) and crude oil droplets (Fig. 4T-Y) to slide down its surface at 15° tilting angle. The presence of low surface energy molecule, NH2-PDMS imparted the excellent liquid repellent property to the coating.
ATR-FTIR analysis confirmed the successful 1,4-conjugate addition reaction between the primary amine groups of PDMS and AEAPTMS with the multiple acrylate groups containing 5Acl molecule which provided the physical and chemical durability to the coating. The IR peaks at 1600 cm-1 for N-H bending of primary amines, 1410 cm-1 for C-H stretching of ß carbon of vinyl group and 1736 cm-1 for carbonyl stretching was observed in the reaction mixture initially as shown in Fig. 5A (blue line). However, significant reduction in the peak at 1410 cm-1 with respect to the carbonyl stretching (1735 cm-1) was observed after drying the coating in the oven which confirmed the successful 1,4-conjugate addition reaction between the primary amines and acrylates as shown in Fig. 5A (black). Moreover, significant reduction in the peak intensity at 1610 cm-1 corresponding to the primary amines suggested the consumption of primary amines in the conjugate addition reaction.
The atomic force microscope (AFM) image revealed that the omniphobic coating has low roughness with Rrms of ~8 nm as shown in Fig. 5B. The synthesized omniphobic coating exhibits 99% optical transparency, identical to a bare glass slide as shown in Fig. 5C. Moreover, energy-dispersive X-ray spectroscopy (EDX) images revealed that all the elements including C, N, O, Si was uniformly distributed throughout the synthesized omniphobic coating as shown in Fig. 5D-H.
Fig.6 (A-O) shows that various oils and organic solvents of varying viscosities and densities including petrol (Fig.6A-C), kerosene (Fig.6D-F), toluene (Fig.6G-I), tetrahydrofuran (Fig.6J-L) and ethanol (Fig.6M-O) slid off from the surface of the omniphobic coating on tilting at an angle of 15°.
Slippery tests on stainless steel surface coated with omniphobic anti-smudge coating: The omniphobic slippery coating can be extended for coating on stainless steel as shown in Fig. 9A-F where the water droplet (Fig. 9A-C) and crude oil droplet (Fig. 9D-F) easily slid off from the steel surface.
C. Physical and Chemical Durability Tests of the Omniphobic Solid Slippery Interface:
The synthesized omniphobic solid slippery coating was capable of sustaining various severe physical abrasions.
(i) Abrasion Tests (finger and tissue paper wiping): Even on rubbing the omniphobic glass slide with the finger and tissue paper for multiple times, the liquid repellent property remained unperturbed and the water/oil droplet slid down the omniphobic surface at 15° tilting angle as shown in Fig. 7A-F.
(ii) Adhesive Tape Test: Further, the omniphobic coating was subjected to the severe adhesive tape peeling process (Fig. 7G and 7H). However, the liquid repellent property remained intact and the water/oil droplet could successfully slid down the omniphobic surface at 15° tilting angle as shown in Fig. 7I-J and Fig. 7K-L.
(iii) Chemical Durability Tests: The omniphobic coating was exposed to distilled water, UV radiation and various chemically complex aqueous phases including highly acidic (pH 1) and alkaline (pH 13) water, surfactants contaminated water, artificial sea water, river water (Brahmaputra, Guwahati, Assam) for 7 days. Even after such prolonged harsh exposures, the omniphobic coating continued to repel the water and oil phases as shown in Fig. 8.
(iv) Heat treatment test: Further, the solid slippery coating was exposed to different temperatures i.e. 50°C, 75°C and 120°C for 24 hours and it was observed that the water and crude oil sliding angles showed slight variation with increase in temperature as tabulated in Table 2.
Table 2: Water sliding angle before and after heat treatment of omniphobic solid slippery coating
Coating Liquid Sliding angle (°)
(Before experiment) Sliding angle (°)
(After 24 h of heat treatment)
50 °C 75 °C 120 °C
Omniphobic Solid Slippery Interface H2O 15 15 15 18
Crude oil 15 15 17 25
INFERENCE The increase in sliding angle with increase in the exposure temperature can be attributed to alternation of chemical compatibility.
TECHNICAL ADVANCEMENTS
The present disclosure described herein above has several technical advantages including, but not limited to, the realization of, an anti-smudge coating that is
• fluorine free,
• sustains harsh setting - high physical and chemical durability,
• has long term durability,
• less expensive as compared to fluorinated molecules,
• omniphobic surface can sustain prolonged physical and chemical damage thus, extending its applications to real life scenarios, and
• the synthesis approach is catalyst-free, facile and scalable without requiring any expensive fluorinated chemicals.
Throughout this specification the word “comprise”, or variations such as “comprises” or “comprising, will be understood to imply the inclusion of a stated element, integer or step,” or group of elements, integers or steps, but not the exclusion of any other element, integer or step, or group of elements, integers or steps.
The use of the expression “at least” or “at least one” suggests the use of one or more elements or ingredients or quantities, as the use may be in the embodiment of the invention to achieve one or more of the desired objects or results. While certain embodiments of the inventions have been described, these embodiments have been presented by way of example only, and are not intended to limit the scope of the inventions. Variations or modifications to the formulation of this invention, within the scope of the invention, may occur to those skilled in the art upon reviewing the disclosure herein. Such variations or modifications are well within the spirit of this invention.
The numerical values given for various physical parameters, dimensions and quantities are only approximate values and it is envisaged that the values higher than the numerical value assigned to the physical parameters, dimensions and quantities fall within the scope of the invention unless there is a statement in the specification to the contrary.
While considerable emphasis has been placed herein on the specific features of the preferred embodiment, it will be appreciated that many additional features can be added and that many changes can be made in the preferred embodiment without departing from the principles of the disclosure. These and other changes in the preferred embodiment of the disclosure will be apparent to those skilled in the art from the disclosure herein, whereby it is to be distinctly understood that the foregoing descriptive matter is to be interpreted merely as illustrative of the disclosure and not as a limitation.
,CLAIMS:WE CLAIM:
1. An anti-smudge coating comprising:
a. at least one acrylate;
b. at least one hydrophobic polymer;
c. at least one amine; and
d. optionally at least one lubricating agent;
wherein said coating when applied on a substrate obtains one of a liquid-infused-slippery interface and a dry-slippery interface.
2. The anti-smudge coating for obtaining said liquid-infused-slippery interface on said substrate as claimed in claim 1, said coating comprising:
a. at least one acrylate;
b. at least one hydrophobic polymer;
c. at least one amine; and
d. at least one lubricating agent.
3. The coating as claimed in claim 2, wherein said acrylate is dipentaerythritol penta-acrylate.
4. The coating as claimed in claim 2, wherein said hydrophobic polymer is branched polyethylenimine.
5. The coating as claimed in claim 2, wherein said amine is octadecylamine.
6. The coating as claimed in claim 2, wherein said lubricating agent is silicon oil.
7. A process for the preparation of the anti-smudge coating as claimed in claim 2, said process comprising the following steps:
a. mixing predetermined amounts of at least one acrylate and at least one hydrophobic polymer in a fluid medium under stirring for a time period in the range of 5 minutes to 25 minutes to obtain a solution;
b. spray depositing said solution on a substrate followed by drying to obtain a coated substrate;
c. modifying said coated substrate with at least one amine to obtain a modified coated substrate;
d. infusing said modified coated substrate with at least one lubricating agent to obtain said anti-smudge coating, wherein said coating has the slippery liquid infused interface.
8. The process as claimed in claim 7, wherein said fluid medium is at least one selected from the group consisting of methanol, ethanol and toluene.
9. The process as claimed in claim 7, wherein said substrate is selected from glass, aluminium foil, stainless steel, wood, plastic and paper.
10. The process as claimed in claim 7, wherein said coating has a thickness in the range of 1.5 µm to 1.6 µm.
11. The process as claimed in claim 7, wherein a weight ratio of said acrylate to said amino silane to said hydrophobic polymer is in the range of 1:0.1:0.01 to 1:0.2:0.05.
12. The anti-smudge coating for obtaining said dry-slippery interface on said glass substrate as claimed in claim 1, said coating comprising:
a. at least one acrylate;
b. at least one hydrophobic polymer; and
c. at least one amine.
13. The coating as claimed in claim 12, wherein said acrylate is dipentaerythritol penta-acrylate.
14. The coating as claimed in claim 12, wherein said hydrophobic polymer is poly[dimethylsiloxane-co-(3-aminopropyl)methylsiloxane].
15. The coating as claimed in claim 12, wherein said amine agent is [3-(2-aminoethylamino)propyl] trimethoxysilane.
16. A process for the preparation of the anti-smudge coating as claimed in claim 12, said process comprising the following steps:
a. mixing predetermined amounts of at least one acrylate, at least one hydrophobic polymer and at least one amine in a fluid medium under stirring for a time period in the range of 5 minutes to 25 minutes to obtain a solution;
b. applying said solution on a substrate to obtain a coated substrate; and
c. drying said coated substrate at a predetermined temperature for a predetermined time period to obtain said anti-smudge coating, wherein said coating has the solid slippery interface.
17. The process as claimed in claim 16, wherein said predetermined temperature is in the range of 70 °C to 100 °C.
18. The process as claimed in claim 16, wherein said predetermined time period is in the range of 4 hours to 8 hours.
19. The process as claimed in claim 16, wherein said fluid medium is at least one selected from the group consisting of methanol, ethanol and toluene.
20. The process as claimed in claim 16, wherein said substrate is selected from glass, aluminium foil, stainless steel, wood, plastic and paper.
21. The process as claimed in claim 16 , wherein said coating has a thickness in the range of 90 µm to 125 µm.
22. The process as claimed in claim 16, wherein a weight ratio of said acrylate to said hydrophobic polymer to said amine is in the range of 1:1.1:0.5 to 1:1.2:1.
Dated this 15th day of May, 2021

_______________________________
MOHAN RAJKUMAR DEWAN, IN/PA – 25
of R.K.DEWAN & CO.
Authorized Agent of Applicant

TO,
THE CONTROLLER OF PATENTS
THE PATENT OFFICE, AT CHENNAI