WO2017111702A1

WO2017111702A1 - Durable superhydrophobic coating

Info

Publication number: WO2017111702A1
Application number: PCT/SG2016/050615
Authority: WO
Inventors: Hong Yan; Jianwei Xu; Qun YE; Hui Zhou
Original assignee: Agency for Science Technology and Research Singapore
Current assignee: Agency for Science Technology and Research Singapore
Priority date: 2015-12-23
Filing date: 2016-12-23
Publication date: 2017-06-29
Anticipated expiration: 2018-06-23
Also published as: WO2017111702A9; CN108699246A; SG11201805366VA

Abstract

The invention relates to a polymeric coating material comprising a surface-functionalized such as vinyl functionalized nanoadditive covalently bound to an organopolysiloxane, such as poly(methylhydrosiloxane) (PMHS), wherein the nanoadditive comprises (a) a nanoadditive substrate and (b) a linker covalently bound by a silyloxy moiety to the nanoadditive substrate at one end and said organopolysiloxane at the other end. The invention also relates to a method of making such a coating material, the use of such a coating material, a method for coating a substrate with such a coating material, and a coated substrate obtainable by such a method.

Description

Title of Invention: Durable Superhydrophobic Coating

Technical Field

The present invention relates to a coating material for superhydrophobic coatings. The present invention also relates to a method of fabricating such a coating material.

Background Art Superhydrophobic textiles are attractive because of their wide range of applications in surgical tools, medical devices, textiles (such as swimwear and military clothing), maritime industry and in environmental applications. Currently, the main problem for commercialization of superhydrophobic textile is the high overall manufacturing cost, low mechanical strength and poor durability of coating materials on textile substrates. Therefore, current approaches are focused on how to use cost-effective materials to achieve superhydrophobicity with enhanced long-term durability. In addition, in recent years, mimicking hierarchical morphology of lotus leaf has been a main strategy to create superhydrophobic textiles, which involves either incorporating a coating layer with low surface energy or creating a special morphology or patterning on fibers, or both. Currently, perfluorinated materials have been widely applied for superhydrophobic coatings. Perfluorinated materials have the characteristics of low cohesive energy, low surface free energy and low water uptake, which results in chemical resistance, corrosion resistance, low friction performance and weather resistance. For these reasons, they have been selected to be applied in superhydrophobic textile coating in modern industry. However, they are expensive and are hard to process in some cases. In addition, their potential impact on health is uncertain, as perfluorinated materials have no known metabolic roles in mammals which may result in bioaccumulation, persist in the environment, and some may be reactive and toxic. Therefore applications of perfluorinated materials are limited. Efforts have therefore been directed to develop non-fluorine containing materials for superhydrophobic textile coating, such as using metal oxide nanocomposite, precipitated calcium carbonate and carbon nanotube. For instance, a cotton fabric coated with zinc oxide nanorods or zinc oxide crystallites can result in a superhydrophobic surface.

Another alternative is to use siloxane polymers such as polydimethylsiloxane (PDMS), poly(methylhydrosiloxane) (PMHS), or its copolymer which are non-toxic, low cost, easily fabricated, flexible and optically transparent. Coating a fibre with millions of tiny silicone filaments can result in a water-repellent clothing material. In addition, a superamphiphobic textile, which is achieved through a two-step wet-chemistry coating technique, has been shown to exhibit remarkable multi-self healing ability against physical and chemical damages and exceptional liquid-repellency to low surface-tension liquids including ethanol. However, most conventional methodologies require perfluoromaterials, poisonous chemicals, and delicate preparation procedures.

It has been shown that reduced graphene -oxide (RGO) can be applied to the surface of cotton fibres to tune the wettability of the fibres, so they become superhydrophobic to water while superoleophilic to organic materials or oils. PDMS can be further applied to the cotton fibres coated with RGO to improve its surface wettability. However, in such a process, the RGO and PDMS are not chemically bonded to each other, which means that the coating can only be used on limited types of materials under limited treatment methods. Such a coating may also have limited durability and resistance to abrasion, especially under repeated washing. Further, a high concentration of RGO is required when the textile requires to be first coated with RGO.

Another alternative that has been studied is the reduced graphene -oxide (RGO) modified organopolysiloxanes for superhydrophobic textile coating, which shows long-term acid, alkaline and hot-water resistance as well as abrasion resistance. Such RGO modified organopolysiloxanes coating materials were synthesized via aryl radical assisted addition reaction, followed by hydrosilyation to covalently bond a very small amount of RGO with organopolysiloxanes. Although the RGO-modified organopolysiloxanes showed excellent properties, there were limitations in it, including the tedious preparation process of vinyl functionalized RGO and limited Si-H groups being available for reaction with the polymer matrix.

In this regard, despite the extensive efforts that have been made to achieve superhydrophobic textile coatings, challenging issues such as the high cost of materials, mechanical properties of the coating, chemical and environmental resistance of the coating, safety and comfort of the coatings remain. There is therefore a need to provide a coating material that overcomes or at least ameliorates, one or more of the disadvantages described above.

Summary

In an aspect of the present disclosure, there is provided a polymeric coating material comprising a nanoadditive covalently bound to an organopolysiloxane, wherein the nanoadditive comprises a) a nanoadditive substrate and b) a linker covalently bound by a silyloxy moiety to the nanoadditive substrate at one end and said organopolysiloxane at the other end.

Advantageously the coating material may be superhydrophobic and repel water.

More advantageously the coating material may not comprise fluorine. That is, the coating material may be fluorine-free. This means that any adverse effect associated with the use of perfluorinated materials may be circumvented by the disclosed polymeric coating material. For example, the disclosed coating material may be biocompatible, as it does not contain perfluorinated materials which may be toxic. Further, by not comprising perfluorinated materials, the disclosed coating material may be provided in a more cost-effective manner. Further advantageously, the disclosed coating material may comprise zero- to two-dimensional nanoadditives, which may only be required in trace amounts (< 0.5% wt%). This may avoid having to use large amounts of expensive nanoadditives, resulting in the coating material being more cost-effective.

More advantageously, the disclosed coating material may have high durability in harsh conditions. The disclosed coating may have excellent long-term resistance to strong mineral acid, strong corrosive alkaline and hot water, whilst maintaining its superhydrophobic properties. Further advantageously, the disclosed coating material may retain its superhydrophobic properties even after greater than 500 (or 7 days of) washings or after strong etching. Further advantageously, only a small amount of the disclosed coating material may be necessary to confer the superhydrophobic properties to the textile substrate, to confer resistance to strong corrosive acid, strong corrosive alkaline, hot water or chemical abrasion.

Advantageously, the nanoadditive substrate and the organopolysiloxane of the disclosed coating material may by covalently bonded. Without being bound to theory, the advantageous properties of the disclosed coating material may be due to the strong covalent linkage present between the nanoadditive substrate and the organopolysiloxane.

In another aspect, there is provided a method for making a coating material, comprising the steps of a) reacting a silane reagent, preferably a vinyl trialkoxy silane, with a nanoadditive substrate, which is optionally surface functionalized with hydroxyl groups, b) covalently bonding the reaction product to an organopolysiloxane or its precursors optionally in the presence of a catalyst.

Advantageously, the disclosed method provides a facile method for the synthesis of hybrid composites of nanoadditives and polysiloxanes. Further advantageously, the method facilitates mass production of the coating material as it is suitable for scaling up compared to conventional methods.

In another aspect, there is provided the use of the coating material as defined above for coating a substrate, preferably natural or man-made fibers. In another aspect, there is provided a method of coating a substrate, preferably a fiber, comprising the steps of: a) dissolving a coating material as defined above in a solvent to form a coating solution; b) immersing said substrate in the coating solution; and c) removing said substrate from the coating solution.

Advantageously, the disclosed method facilitates easy coating of a substrate with the coating material as defined above. Further advantageously, the method allows the coating material to be applied to various natural or man-made fibers to achieve similar superhydrophobicity. Further advantageously, no further processing is required of the substrate after the coating process, making the application of the coating material straight forward and efficient.

In another aspect, there is provided a coated substrate obtainable by any of the methods as defined above having superhydrophobic properties.

Advantageously, the physicochemical properties, the colour or the hand feel of the substrate coated with the disclosed coating material may not change. More advantageously, the coating material may be stain resistant which means that any substrate coated with the disclosed coating material may be easily washed. Further advantageously, the coating material may be applied across a wide range of substrates, including cotton, polyester, nylon and nomex, while maintaining the superhydrophobic properties. Even further advantageously, similar superhydrophobic properties may be conferred to the substrate, even if the properties of the substrates themselves are different. More advantageously, the permeability of the original substrate may be maintained even after coating the substrate with the disclosed coating material.

In another aspect, there is provided a polymer nanoadditive composite comprising a nanoadditive covalently bound to an organopolysiloxane, wherein the nanoadditive comprises a) a nanoadditive substrate and b) a linker covalently bound by a silyloxy moiety to the nanoadditive substrate at one end and said organopolysiloxane at the other end; and wherein the organopolysiloxane comprises one or more non-terminal units of formula (III) in the polymer chains

wherein

R¹, is independently selected from hydrogen, Ci to Ci₀-alkyl, Ci to Ci₀-alkenyl, Ci to Cio-alkyl- C₆ to Ci₀-aryl or C₆ to Ci₀-aryl; and R¹ is preferably methyl; and X is the bond to the linker.

Brief Description of Drawings The accompanying drawings illustrate a disclosed embodiment and serves to explain the principles of the disclosed embodiment. It is to be understood, however, that the drawings are designed for purposes of illustration only, and not as a definition of the limits of the invention.

Fig.l [Fig. 1] is a schematic representation of silane hydrolysis followed by condensation on a hydrated surface.

Fig.2

[Fig. 2] is a schematic representation of the silylation-polymerization procedure of PMHS with various vinyl-functionalized nanoadditives. Fig. 3

[Fig. 3] refers to a photograph of (a) original clay and (b) vinylsilane-functionalized clay in (A) water and (B) THF.

Fig. 4

[Fig. 4] refers to FTIR spectra of (a) octavinyl POSS and (b) PMHS @POSS. Fig. 5

[Fig. 5] refers to FTIR spectra of (a) SiNPs, (b) vinylsilane-functionalized SiNPs and (c) PMHS @ SiNPs.

Fig. 6 [Fig. 6] refers to FTIR spectra of (a) rough carbon nanotubes (CNT), (b) vinylsilane- functionalized CNT and (c) PMHS @CNT.

Fig. 7

[Fig. 7] refers to FTIR spectra of (a) rough clay, (b) vinylsilane-functionalized clay and (c) PMHS @Clay. Fig. 8

[Fig. 8] refers to FTIR spectra of (a) GO, (b) vinylsilane-functionalized GO and (c) PMHS @GO.

Fig. 9

[Fig. 9] refers to FTIR spectra of (a) RGO, (b) vinylsilane-functionalized RGO and (c) PMHS @RGO.

Fig. 10

[Fig. 10] is a TEM micrograph of vinylsilane-functionalized SiNPs.

Fig. 11

[Fig. 11] refers to TEM micrographs of (a) GO and (b) vinylsilane-functionalized GO. Fig. 12

[Fig. 12] is a TEM micrograph of vinylsilane-functionalized RGO.

Fig. 13

[Fig. 13] refers to TEM micrographs of samples of (A) rough clay and (B) vinylsilane- functionalized clay. Fig. 14

[Fig. 14] refers to images showing wetting behavior of a water drop on cotton fabric coated with the coating materials that are embodiments of the present application. The images show 5 uL drops of water on (A) PMHS @POSS, (B) PMHS @SiNPs, (C) PMHS @CNT, (D) PMHS @ Clay, (E) PMHS @ GO and (F) PMHS @RGO.

Fig. 15

[Fig. 15] refers to SEM images of cotton textile (A) uncoated, (B) coated with PMHS @SiNPs, (C) coated with PMHS @POSS, and (D) coated with PMHS @Clay.

Fig. 16

[Fig. 16] refers to images showing the wetting behaviour of a water drop on various comcemtial textile substrates (1) knit, (2) nonwoven and (3) woven. The images show drops on textiles (A) uncoated, (B) coated with PMHS @POSS, (C) coated with PMHS @Silica, (D) coated with PMHS @CNT, (E) coated with PMHS @GO, (F) coated with PMHS @RGO, and (G) coated with PMHS @Clay.

Fig. 17

[Fig. 17] is a graphical representation of a superhydrophobic textile-coating of PMHS @nanoadditive on the textile substrate. Fig. 18

[Fig. 18] refers to (A) an image showing the stain-resistant behavior of a cotton glove (a) uncoated and (b) coated with PMHS @Clay, (B) an image showing the colour of the substrate (a) before coating and (b) after coating with PMHS @ Clay, (C) an image showing the antibacterial behavior of a textile substrate (a) uncoated and (b) coated with PMHS @ Clay and (D) the self-cleaning ability of a textile substrate (a) uncoated and (b) coated with PMHS @ Clay.

Fig. 19

[Fig. 19] refers to images showing the wetting behaviour of a water drop on a cotton textile substrate coated with PMHS @Clay after being immersed in acid solution for (A) 1 week, (B) 2 weeks, (C) 3 weeks and (D) 4 weeks.

Fig. 20

[Fig. 20] refers to images showing the wetting behaviour of a water drop on a cotton textile substrate coated with PMHS @ Clay after being immersed in alkaline solution for (A) 1 week and (B) 2 weeks. Fig. 21

[Fig. 21] refers to images showing the wetting behaviour of a water drop on a cotton textile substrate coated with PMHS @Clay after washing for (A) 1 day, (B) 2 days, (C) 5 days and (D) 7 days. Fig. 22

[Fig. 22] refers to SEM images showing the morphology of cotton textile substrate coated with PMHS @Clay after washing for (A) 1 day, (B) 2 days, (C) 5 days and (D) 7 days.

Definitions The following words and terms used herein shall have the meaning indicated:

"Alkyl" as a group or part of a group refers to a straight or branched aliphatic hydrocarbon group, preferably a C_\-C_\2 alkyl, more preferably a Ci-Cio alkyl, most preferably Q-Ce unless otherwise noted. Examples of suitable straight and branched Q-Ce alkyl substituents include methyl, ethyl, n-propyl, 2-propyl, n-butyl, sec-butyl, t-butyl, hexyl, and the like. The group may be a terminal group or a bridging group.

"Alkenyl" as a group or part of a group denotes an aliphatic hydrocarbon group containing at least one carbon-carbon double bond and which may be straight or branched preferably having 2-12 carbon atoms, more preferably 2-10 carbon atoms, most preferably 2-6 carbon atoms, in the normal chain. The group may contain a plurality of double bonds in the normal chain and the orientation about each is independently E or Z. Exemplary alkenyl groups include, but are not limited to, ethenyl, propenyl, butenyl, pentenyl, hexenyl, heptenyl, octenyl and nonenyl. The group may be a terminal group or a bridging group.

"Aryl" as a group or part of a group denotes (i) an optionally substituted monocyclic, or fused polycyclic, aromatic carbocycle (ring structure having ring atoms that are all carbon) preferably having from 5 to 12 atoms per ring. Examples of aryl groups include phenyl, naphthyl, and the like; (ii) an optionally substituted partially saturated bicyclic aromatic carbocyclic moiety in which a phenyl and a C5 7 cycloalkyl or C5 7 cycloalkenyl group are fused together to form a cyclic structure, such as tetrahydronaphthyl, indenyl or indanyl. The group may be a terminal group or a bridging group. Typically an aryl group is a C₆-C₁₈ aryl group. "Alkylaryl" means an alkyl-aryl— group in which the aryl and alkyl moieties are as defined herein. Preferred alkylaryl groups contain a C_{1 10} alkyl moiety. The group may be a terminal group or a bridging group. If the group is a terminal group it is bonded to the remainder of the molecule through the aryl group. For the purposes of this disclosure, the term "PHMS@POSS" means "vinylsilane functionalized POSS cross-linked with PHMS" The terms PMHS @SiNP, PMHS @CNT, PMHS @Clay, PMHS @RO, PMHS @RGO should be construed accordingly.

For the purposes of this disclosure, PDMS/PMHS means a copolymer of PDMS and PHMS. The term "PDMS PMHS @POSS" therefore means "vinylsilane functionalized POSS cross- linked with a copolymer of PDMS and PMHS". The terms PDMS/PMHS @SiNP, PDMS/PMHS @CNT, PDMS/PMHS @Clay, PDMS/PMHS @RO and

PDMS/PMHS @RGO should be construed accordingly.

For the purposes of this disclosure, zero-dimensional (0D) nanostructures (such as nanoparticles) have three dimensions on the nanoscale, typically below 100 nm. One- dimensional (ID) nanomaterials (such as nanorods, nano wires, nanobelts and nanotubes) have two dimensions on the nanoscale, typically below 100 nm. Two-dimensional (2D) nanomaterials (such as nanosheet and nanoplate) have one dimension on the nanoscale, typically below 100 nm. The word "substantially" does not exclude "completely" e.g. a composition which is "substantially free" from Y may be completely free from Y. Where necessary, the word "substantially" may be omitted from the definition of the invention.

Unless specified otherwise, the terms "comprising" and "comprise", and grammatical variants thereof, are intended to represent "open" or "inclusive" language such that they include recited elements but also permit inclusion of additional, unrecited elements.

As used herein, the term "about", in the context of concentrations of components of the formulations, typically means +/- 5% of the stated value, more typically +/- 4% of the stated value, more typically +/- 3% of the stated value, more typically, +/- 2% of the stated value, even more typically +/- 1% of the stated value, and even more typically +/- 0.5% of the stated value.

Throughout this disclosure, certain embodiments may be disclosed in a range format. It should be understood that the description in range format is merely for convenience and brevity and should not be construed as an inflexible limitation on the scope of the disclosed ranges. Accordingly, the description of a range should be considered to have specifically disclosed all the possible sub-ranges as well as individual numerical values within that range. For example, description of a range such as from 1 to 6 should be considered to have specifically disclosed sub-ranges such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6 etc., as well as individual numbers within that range, for example, 1, 2, 3, 4, 5, and 6. This applies regardless of the breadth of the range. Certain embodiments may also be described broadly and generically herein. Each of the narrower species and subgeneric groupings falling within the generic disclosure also form part of the disclosure. This includes the generic description of the embodiments with a proviso or negative limitation removing any subject matter from the genus, regardless of whether or not the excised material is specifically recited herein.

Detailed Disclosure of Optional Embodiments Exemplary, non-limiting embodiments of a polymer matrix will now be disclosed.

Hybridization of nanoadditive and polymer matrices represent a class of emerging materials that are promising for superhydrophobic textile coating as they integrate both inherent characteristics of organic polymer matrix and nanoadditives. However, many studies have suggested that the performance of hybrid superhydrophobic materials may be limited by two factors:

1) Compatibility of nanoadditives and polymer matrix.

Incompatibility of the two species remains a fundamental obstacle in the preparation of hybrid nanocomposites due to the tendency of nanoadditives to aggregate or precipitate during the hybridization reaction. 2) Efficiency of chemical bonding between nanoadditives and polymer matrix.

Reactivity between functionalized nanoadditives and polymer matrices plays a key role in contributing to the stability of the resulting coating. In general, creating strong chemical bonding between nanoadditives and polymer matrices can significantly increase the mechanical and physical properties of the coating film. Organopolysiloxanes-reduced graphene oxide (RGO) hybrid polymeric materials have been prepared for superhydrophobic textile coating. Such materials are prepared by crosslinking RGO with poly(methylhydrosiloxane) (PMHS) through hydrosilylation via aryl radical assisted addition reactions. These organopolysiloxanes modified by two-dimensional nanomaterials such as RGO have been shown to have extraordinary chemical and physical resistance. However, the preparation process of vinyl functionalized RGO and limited Si-H groups being available for reaction with the polymer matrix made the process tedious and inefficient.

In contrast to the preparation method of alternative materials such as vinyl-functionalized RGO through aryl radical assisted addition reactions, in the present disclosure, a series of nanoadditives from zero-dimensional polyhedral oligomeric silsesquioxanes (POSS) and nanoparticles silica nanoparticles (SiNPs), one dimensional carbon nanotube (CNT) and two dimensional graphene oxide (GO), reduced graphene oxide (RGO) and clay have been treated with a silane reagent, for example, tetraethoxysilane (TEOS) first, followed by reacting with PMHS to give rise to zero- to two- dimensional nanoadditive modified PMHS polymers. The nanoadditives such as POSS, SiNPs, GO, RGO, and clay have tunable dimensions and diverse morphologies provide many opportunities for different applications. The nanoadditives are easily synthesized at scale, thus avoiding multistep procedures of polymerization onto textile surfaces. In addition, the nanoadditive modified polymeric materials may be able to form a thin film on the textile substrate, which may be stable over a long period even at harsh conditions. In the present disclosure, these nanoadditives were designed for use as crosslinking agents for the formation of polymeric coating materials. The overall process for immobilization of the vinyl group on nanoadditives via silanization is illustrated in Fig. 1. Group R is a nonhydrolyzable organic radical (a substituted vinyl group) that facilitates bonding with organic resins and polymers. The silanol group usually is a hydrolyzable group, typically trimethoxysilyl or triethoxysilyl, which is involved in the reaction with the nanoadditive substrate. Therefore, in the present disclosure, hydrolysis of trimethoxysilyl groups followed by condensation with silanol groups resulted in covalent attachment of vinyl groups onto nanoadditives surface.

PDMH reacted with vinyl functionalized nanoadditives comprising SiNP, POSS, CNT GO, RGO, and clay to offer polymer composites as shown in Figure 2. The nanoadditive modified PDMH was directly used for textile coating without any further treatment. The variety of the crosslinking nano-agents may provide opportunities to form dense crosslinking polymeric materials, and thus to create high performance superhydrophobic textile coatings. In addition, the ability to allocate active components grafted into the polymeric network may offer an opportunity to improve material stability and subsequently optimize performance. The disclosed polymeric coating material may comprise a nanoadditive covalently bound to an organopolysiloxane, wherein the nanoadditive comprises a) a nanoadditive substrate and b) a linker covalently bound by a silyloxy moiety to the nanoadditive substrate at one end and said organopolysiloxane at the other end. The organopolysiloxane may comprise hydrophobic groups, which are preferably selected from alkyl, alkenyl, alkylaryl or aryl, most preferably Ci to Ci₀-alkyl, Ci to Ci₀-alkenyl, Ci to Ci₀- alkyl-C₆ to Ci₀-aryl or C₆ to Ci₀-aryl.

The alkyl may be linear or branched methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl, nonyl or decyl. The alkenyl may be linear or branched ethenyl, propenyl, butenyl, pentenyl, hexenyl, heptenyl, octenyl, nonenyl, or decenyl. The aryl may be phenyl, naphthyl, tetraphenylnaphthyl, indenyl or indanyl. The alkylaryl may be 2-methylbenzene, 3- methylbenzene, 4-methylbenzene, 2-ethylbenzene, 3-ethylbenzene, 4-ethylbenzene, 2- propylbenzene, 3-propylbenzene, 4-propylbenzene, 2-butylbenzene, 3-butylbenzene, 4- butylbenzene, 2-pentylbenzene, 3-pentylbenzene, 4-pentylbenzene, 2-hexylbenzene, 3- hexylbenzene, 4-hezylbenzene, 2-heptylbenzene, 3-heptylbenzene, 4-heptylbenzene, 2- octylbenzene, 3-octylbenzene, 4-octylbenzene, 2-nonylbenzene, 3-nonylbenzene, 4- nonylbenzene, 2-decylbenzene, 3-decylbenzene, 4-decylbenzene, 2-ethenylbenzene, 3- ethenylbenzene, 4-ethenylbenzene, 2-propenylbenzene, 3-propenylbenzene, 4-propenylbenzene, 2-butenylbenzene, 3-butenylbenzene, 4-butenylbenzene, 2-pentenylbenzene, 3- pentenylbenzene, 3-pentenylbenzene, 2-hexenylbenzene, 3-hexenylbenzene, 4-hexenylbenzene, 2-heptenylbenzene, 3-heptenylbenzene, 4-heptenylbenzene, 2-octenylbenzene, 3- octenylbenzene, 4-octenylbenzene, 2-nonenylbenzene, 3-nonenylbenzene, 4-nonenylbenzene, 2- decenylbenzene, 3-decenylbenzene or 4-decenylbenzene.

The content of nanoadditive substrate may be less than about 3 % by weight, preferably less than about 0.5 % by weight and most preferably between about 0.005 and 0.5 % by weight, of the organopolysiloxane.

The content of the nanoadditive substrate may be in the range of about 0.001% by weigh to about 5% by weight, about 0.001% by weight to about 0.005% by weight, about 0.001% by weight to about 0.01% by weight, about 0.001% by weight to about 0.05% by weight, about 0.001% by weight to about 0.1% by weight, about 0.001% by weight to about 0.5% by weight, about 0.001% by weight to about 1% by weight, about 0.001% by weight to about 3% by weight, about 0.005% by weight to about 0.01% by weight, about 0.005% by weight to about 0.05% by weight, about 0.005% by weight to about 0.1% by weight, about 0.005% by weight to about 0.5% by weight, about 0.005% by weight to about 1% by weight, about 0.005% by weight to about 3% by weight, about 0.005% by weight to about 5% by weigh, about 0.01% by weight to about 0.05% by weight, about 0.01% by weight to about 0.1% by weight, about 0.01% by weight to about 0.5% by weight, about 0.01% by weight to about 1% by weight, about 0.01% by weight to about 3% by weight, about 0.01% by weight to about 5% by weigh, about 0.05% by weight to about 0.1% by weight, about 0.05% by weight to about 0.5% by weight, about 0.05% by weight to about 1% by weight, about 0.05% by weight to about 3% by weight, about 0.05% by weight to about 5% by weigh, about 0.1% by weight to about 0.5% by weight, about 0.1% by weight to about 1% by weight, about 0.1% by weight to about 3% by weight, about 0.1% by weight to about 5% by weigh, about 0.5% by weight to about 1% by weight, about 0.5% by weight to about 3% by weight, about 0.5% by weight to about 5% by weigh, about 2% by weight to about 3% by weight, about 1% by weight to about 5% by weigh, or about 3% by weight to about 5% by weight, of the organopolysiloxane.

Advantageously, only trace amounts of the nanoadditives are required, avoiding the need to use large amounts of expensive nanoadditives.

The polymeric organopolysiloxane, prior to covalent bonding to the linker, may comprise repetitive silicon-hydrogen moieties.

The polymeric organopolysiloxane, prior to covalent bonding to the linker, may comprise one or more, preferably from 3 to 200, units of formula (I) or (la) in the polymer chains

/† R¹

H

(la)

wherein R¹, at each occurrence, is independently selected from Ci to Ci₀-alkyl, Ci to Ci₀- alkenyl, Ci to Cio-alkyl- C₆ to Ci₀-aryl or C₆ to Cio-aryl; and R¹ is preferably methyl.

The polymeric organopolysiloxane, prior to covalent bonding to the linker, may comprise one or more units of formula (I) or (la) in the polymer chains. The polymeric organopolysiloxane, prior to covalent bonding to the linker, may comprise from 1 to 300 units, from 1 to 3 units, from 1 to 10 units, from 1 to 20 units, from 1 to 50 units, from 1 to 100 units, from 1 to 200 units, from 3 to 10 units, from 3 to 20 units, from 3 to 50 units, from 3 to 100 units, from 3 to 200 units, from 3 to 300 units, from 10 to 20 units, from 10 to 50 units, from 10 to 100 units, from 10 to 200 units, from 10 to 300 units, from 20 to 50 units, from 20 to 100 units, from 20 to 200 units, from 20 to 30 units, from 50 to 100 units, from 50 to 200 units, from 50 to 300 units, from 100 to 200 units, from 100 to 300 units or from 200 to 300 units of formula (I) or (la) in the polymer chains.

R¹ may be preferably selected from alkyl, alkenyl, alkylaryl or aryl, most preferably Ci to Ci₀- alkyl, Ci to Cio-alkenyl, Ci to Ci₀-alkyl-C₆ to Cio-aryl or C₆ to Cio-aryl.

When R¹ is alkyl, the alkyl may be linear or branched methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl, nonyl or decyl. When R¹ is alkenyl, the alkenyl may be linear or branched ethenyl, propenyl, butenyl, pentenyl, hexenyl, heptenyl, octenyl, nonenyl, or decenyl. When R¹ is aryl, the aryl may be phenyl, naphthyl, tetraphenylnaphthyl, indenyl or indanyl. When R¹ is alkylaryl, the alkylaryl may be 2-methylbenzene, 3-methylbenzene, 4-methylbenzene, 2-ethylbenzene, 3- ethylbenzene, 4-ethylbenzene, 2-propylbenzene, 3-propylbenzene, 4-propylbenzene, 2- butylbenzene, 3-butylbenzene, 4-butylbenzene, 2-pentylbenzene, 3-pentylbenzene, 4- pentylbenzene, 2-hexylbenzene, 3-hexylbenzene, 4-hezylbenzene, 2-heptylbenzene, 3- heptylbenzene, 4-heptylbenzene, 2-octylbenzene, 3-octylbenzene, 4-octylbenzene, 2- nonylbenzene, 3-nonylbenzene, 4-nonylbenzene, 2-decylbenzene, 3-decylbenzene, 4- decylbenzene, 2-ethenylbenzene, 3-ethenylbenzene, 4-ethenylbenzene, 2-propenylbenzene, 3- propenylbenzene, 4-propenylbenzene, 2-butenylbenzene, 3-butenylbenzene, 4-butenylbenzene, 2-pentenylbenzene, 3-pentenylbenzene, 3-pentenylbenzene, 2-hexenylbenzene, 3- hexenylbenzene, 4-hexenylbenzene, 2-heptenylbenzene, 3-heptenylbenzene, 4-heptenylbenzene, 2-octenylbenzene, 3-octenylbenzene, 4-octenylbenzene, 2-nonenylbenzene, 3-nonenylbenzene, 4-nonenylbenzene, 2-decenylbenzene, 3-decenylbenzene or 4-decenylbenzene. Advantageously, the multiple reaction sites of the organopolysiloxane offers strong covalent bonding between the nanoadditives and polymer matrix, preventing phase separation in the final hybrid materials.

The polymeric organopolysiloxane may be poly(methylhydrosiloxane) (PMHS).

Advantageously, PMHS may have more reactive sites (Si-H groups) which facilitates more durable coating materials as it is able to form stronger linkages between the polymer matrix and the nanoadditives.

The poly(methylhydrosiloxane) may be of representative formula (II)

wherein R¹ represents methyl, and n is an integer selected so that the poly(methylhydrosiloxane) has a molecular weight range of about 390 to about 10,000. n may be an integer selected so that the poly(methylhydrosiloxane) has a molecular weight range of about 350 to about 15,000, about 350 to about 390, about 350 to about 500, about 350 to about 1000, about 350 to about 5000, about 350 to about 10,000, about 390 to about 500, about 390 to about 1000, about 390 to about 5000, about 390 to about 10,000, about 390 to about 15,000, about 500 to about 1000, about 500 to about 5000, about 500 to about 10,000, about 500 to about 15,000, about 1000 to about 5000, about 1000 to about 10,000, about 1000 to about 15,000, about 5000 to about 10,000, about 5000 to about 15,000 or about 10,000 to about 15,000. The nanoadditive substrate, prior to being linked to the organopolysiloxane, may be surface- functionalized with vinyl groups, preferably by using trimethoxy(vinyl)silane as a silane reagent.

Advantageously, the surface functionalization using vinyl groups facilitates strong covalent bond in between the nanoadditive with the polymer. The nanoadditive substrate may be a particle of 10 nm to 10 μιη size. The nanoadditive substrate may be a particle of about 5 nm to about 15 μιη, about 5 nm to about 10 nm, about 5 nm to about 50 nm, about 5 nm to about 100 nm, about 5 nm to about 500 nm, about 5 nm to about 1 μιη, about 5 nm to about 5 μιη, about 5 nm to about 10 μιη, about 10 nm to about 50 nm, about 10 nm to about 100 nm, about 10 nm to about 500 nm, about 10 nm to about 1 μιη, about 10 nm to about 5 μιη, about 10 nm to about 10 μιη, about 10 nm to about 15 μιη, about 50 nm to about 100 nm, about 50 nm to about 500 nm, about 50 nm to about 1 μιη, about 50 nm to about 5 μιη, about 50 nm to about 10 μιη, about 50 nm to about 15 μιη, about 100 nm to about 500 nm, about 100 nm to about 1 μιη, about 100 nm to about 5 μιη, about 100 nm to about 10 μηι, about 100 nm to about 15 μηι, about 500 nm to about 1 μηι, about 500 nm to about 5 μηι, about 500 nm to about 10 μιη, about 500 nm to about 15 μιη, about 1 μιη to about 5 μιη, about 1 μιη to about 10 μιη, about 1 μιη to about 15 μιη, about 5 μιη to about 10 μιη, about 5 μιη to about 15 μm or about 10 μιη to about 15 μιη. The nanoadditive substrate may be selected from the group consisting of carbon nanotubes, graphene oxides and reduced graphene oxides, clay, silica-dioxide nanoparticles or a polyhedral oligomeric silsesquioxane.

Advantageously, different kinds of nanoadditives may be used in the coating material. The nanoadditive may be zero-dimensional, one -dimensional or two-dimensional. The silyloxy linker, before forming the covalent bonds, may comprise a nonhydrolyzable moiety, preferably a vinyl group, and a silyloxy moiety.

Advantageously, this may ensure selective bonding of the nanoadditive to organopolysiloxane. Further advantageously, this may ensure that the resultant coating has long-term resistance to strong acid, base and hot water, as less chemical reactions would take place in the absence of hydrolysable groups.

The silyloxy moiety may be covalently bound to the nanoadditive substrate via a silyl-ether bridge.

Advantageously, the silyl-ether bridge may provide a strong chemical bond between the nanoadditive and the polymer matrices which in turn significantly increases the mechanical and physical properties of the coating material.

The nonhydrolyzable moiety, preferably a vinyl group, may be covalently bound to the polymeric organopolysiloxane.

A method for making a coating material may comprise the steps of a) reacting a silane reagent, preferably a vinyl trialkoxy silane, with a nanoadditive substrate, which is optionally surface functionalized with hydroxyl groups, b) covalently bonding the reaction product to an organopolysiloxane or its precursors optionally in the presence of a catalyst.

The silane reagent may be any reagent comprising a silane.

The vinyl trialkoxy silane may be vinyl trimethoxysilane, vinyl triethoxysilane, vinyl tripropyloxysilane or vinyl tributyloxysilane.

The catalyst may be selected from group 10 elements. The group 10 element may be nickel, palladium or platinum. The catalyst may comprise platinum. The catalyst may be platinum(0)-l,3- divinyl-1, 1,3,3- tetramethyl-disiloxane, catalysts used in classical Pt-catalysis such as Speier's or Karstedt's catalysts, catalysts used in Rh-based catalysis such as [Rh(cod)₂]BF₄ or [RhCl(nbd)]₂, or catalysts used in Ru-based catalysts such as Wilkinson's catalyst, Grubbs' 1^st generation cacatalyst, [Ru(benzene)Cl₂] 2 or [Ru(p-cymene)Cl₂] 2), [Cp*Ru(MeCN)₃]PF₆.

Advantageously, the organopolysiloxane may be PMHS, and the nanoadditive substrate may be vinylsilane functionalized. By the disclosed method, the reaction between the organopolysiloxane and the nanoadditive substrate may be easily controlled without the need to introduce complicated intermediates. The use of the coating material as defined above may be for coating a substrate, preferably natural or man-made fibers.

The substrate may be a textile. The textile may be a flexible material consisting of a network of natural or man-made (artificial) fibers. The natural or man-made fibers may comprise hair, fur, skin, silk, wool, flax, cotton, grass, rush, hemp, sisal, coir, straw, bamboo, pulpwood, rice, nettle, jute, modal, lacebark, acetate, seaweed, lyocells, asbestos, basalt, glass, metal, polyester, aramid, acrylic, nylon, spandex, olefin, ingeo, lucrex, milk or carbon.

Advantageously, the coating material may be used on a variety of different substrates, yet confer the same superhydrophobic properties to the substrate when the substrate is coated with the coating material. A method of coating a substrate, preferably a fiber, may comprise the steps of: a) dissolving a coating material as defined above in a solvent to form a coating solution; b) immersing said substrate in the coating solution; and c) removing said substrate from the coating solution. The method may further comprise the step of (d) drying the substrate from step (c) to remove the solvent.

The solvent used may be any solvent that is capable of dissolving the coating material as defined above. The solvent used may preferably be selected from the group consisting of toluene, dichloromethane and chloroform. A coated substrate may be obtainable by any of the methods as defined above having superhydrophobic properties.

The coated substrate may have a water contact angle (WCA) in the range of about 150° to about The coated substrate may be for use in textile processing, packaging materials, paper industry, antifouling clothing, sportswear and boat sails.

A polymer nanoadditive composite may comprise a nanoadditive covalently bound to an organopolysiloxane, wherein the nanoadditive comprises a) a nanoadditive substrate and b) a linker covalently bound by a silyloxy moiety to the nanoadditive substrate at one end and said organopolysiloxane at the other end; and wherein the organopolysiloxane comprises one or more non-terminal units of formula (III) in the polymer chains

wherein

The organopolysiloxane, prior to covalent bonding to the linker, may be a poly(methylhydrosiloxane) of representative formula (II)

wherein R¹ represents methyl, and n is an integer selected to represent an integer so that the poly(methylhydrosiloxane) has a molecular weight range of about 390 to about 10,000.

The nanoadditive substrate may be selected from the group consisting of carbon nanotubes, graphene oxides and reduced graphene oxides, clay, silica-dioxide nanoparticles or a polyhedral oligomeric silsesquioxane. Examples

Non-limiting examples of the invention and a comparative example will be further described in greater detail by reference to specific Examples, which should not be construed as in any way limiting the scope of the invention.

Example 1: Materials and Methods

Materials

Poly(mefhylhydrosiloxane) (average Mn 1,700-3,200, PMHS), Poly(dimefhylsiloxane-co- methylhydrosiloxane), (trimethylsilyl terminated, (PDMS/PMHS), (Mn -13,000, mefhylhydrosiloxane 3-4 mol %) was purchased from Sigma-Aldrich. The clay used is the alkyl quaternary ammonium salt bentonite "CLOISITE 30B". Other chemicals were purchased from Sigma-Aldrich and used as received. Water was purified with a Millipore Milli-Q water system.

Methods

Scanning electron microscopy (SEM) images were taken using a JEOL JSM 6700F operated at an acceleration voltage of 5.0 kV. Contact angle (CA) measurements were carried out on a rame-hart Contact Angle Goniometers using liquid droplets of 5 in volume. Fourier transform infrared (FTIR) spectra were recorded on a Bruker VERTEX 70 instrument in ATR mode at a resolution of 4 cm-1 accumulating 32 scans.

Example 2: Synthesis

Example 2 A: Preparation of vinylsilane-functionatized silica nanoparticles (SiNPs)

Briefly, tetraethoxysilane (TEOS, 10 mL) and ammonium hydroxide (10 mL) were dissolved into a solution of ethanol/water (428 mL/60 mL, v/v) with gentle stirring at 30 °C for 2 hours. The white product was rinsed 4 times with ethanol and distilled water, respectively. The resulting surfactant -free SiNPs was dried overnight in a vacuum oven at 40 °C to remove the remaining solvent. The SiNPs (1.00 g) was then refluxed for 20 hours in 80.00 mL of anhydrous toluene with 0.25 mL (1.00 mmol) of trimethoxy(vinyl)silane to yield the vinylsilane- functionalized SiNPs.

Example 2B: Preparation of vinylsilane-functionatized multi-walled carbon nanotubes (MWCNT)

MWCNT (0.5 g) was added to 150 mL of H₂S0₄ (98%) and then sonicated at room temperature for 30 min. 50 mL of concentrated HN0₃ was added to the solution slowly and stirred vigorously at room temperature for 30 minutes. The mixture was heated to 80 °C for 1 hour. After that, the mixture was cooled to room temperature and slowly diluted with Milli-Q water. The mixture was filtered and washed with methanol and distilled water through 0.2 μιη filter paper 4 times. After vacuum drying of the filtrate, MWCNTs functionalized (MWCNT-OH) with hydroxyl groups were obtained.

Hydroxy functionalized MWCNTs (0.05 g) as prepared above was dispersed in 40 mL toluene by ultrasonication for 10 min. After adding an excess of trimethoxy(vinyl)silane, the suspension was refluxed under N₂ at 100 °C for 6 h. After reaction, the resultant filtrate was washed repeatedly with methanol to remove residual trimethoxy(vinyl)silane. The solid product obtained was dried under vacuum overnight.

Example 2C: Preparation of vinylsilane-functionalized clay Clay (5.0 g) was mixed with 1, 2.5, or 3.5 M H₂S0₄ solutions (100 mL). The resulting suspensions were heated at 80 ± 2 °C for 2 hours under continuous stirring. After acid activation, the precipitate was filtered and washed thoroughly with distilled water until the filtrate was free from sulphate ions (tested by BaCl₂ solution). Acid activated clay was then suspended in toluene at the concentration of 10 g/L and a required amount of trimethoxy(vinyl)silane was introduced into the reaction flask and the mixture was refluxed for 6 hrs. The grafted clay was filtered, extensively washed with toluene in order to remove the silane in excess, and dried overnight in a vacuum oven at 40 °C before using. Fig. 3 refers to images of (a) original clay and (b) vinylsilane-functionalized clay in (A) water and (B) THF, and shows the solubility changes of clay in water and THF before and after vinylsilane treatment.

Example 2D: Preparation of vinylsilane-functionalized graphene oxide (GO) and reduced graphene oxide (RGO)

GO and RGO were prepared according to the literature reported procedures. GO or RGO (0.5 mg mL ¹) and NaOH (0.25 mL, 2 M) were added into a round bottom flask, which was then topped up with ultrapure water to get the final volume of 100 mL. The solution was stirred vigorously under 80 °C for 30 min. Hot CTAB (10 mL, 0.56 M) was added into the solution, and the mixture was stirred for another half hour. When the temperature was stabilized at 80 °C, TEOS (2 mL) was added dropwise into the solution followed by the addition of trimethoxy( vinyl) silane (0.5 mL) after 15 min. The solution was allowed to incubate at 80 °C for another 4 hours. The final product was collected by centrifugation and washed with HC1 (1 M) and MeOH with equal volumes for 3 times each, and then with pure MeOH for 3 times. The obtained solid product was dried under vacuum overnight.

Example 2E: Preparation of polymeric coating materials of various nanoadditives crosslinked PMHS PMHS or PDMS/PMHS (6 g) was dissolved in toluene, and the as-prepared vinyloxy- containing nanoadditives 30 mg (POSS, SiNPs, CNT, GO, RGO or clay, respectively) was then added. Platinum(0)-l,3-divinyl-l,l,3,3-tetramethyl-disiloxane complex solution (100 μί) was dissolved in minimum toluene and added to the above solution slowly under N₂. Once the addition was complete, the mixture solution was stirred at 80 °C for four hours. The solution was then diluted for further uses. The products obtained were PMHS @POSS, PMHS @SiNP, PMHS @CNT, PMHS @Clay, PMHS@RO, PMHS @RGO, PDMS PMHS @POSS, PDMS PMHS @SiNP, PDMS PMHS @CNT, PDMS PMHS @Clay, PDMS PMHS @RO or PDMS PMHS @RGO, respectably.

Example 3: Characterization of Coating Material

Example 3 A: FTIR

Fig. 4 to 9 show a set of representative FTIR spectra of pristine nanoadditives, vinylsilane- functionalized nanoadditives, and nanoadditive-modified PMHS. Fig. 4 shows the FTIR spectra of (a) octavinyl POSS and PMHS@POS, Fig. 5 shows FTIR spectra of (a) SiNPs, (b) vinylsilane-functionalized SiNPs and (c) PMHS @ SiNPs, Fig. 6 shows FTIR spectra of (a) SiNPs, (b) vinylsilane-functionalized SiNPs and (c) PMHS @ SiNPs, Fig. 7 shows FTIR spectra of (a) rough clay, (b) vinylsilane-functionalized clay and (c) PMHS @clay, Fig. 8 shows FTIR spectra of (a) GO, (b) vinylsilane-functionalized GO and (c) PMHS @ GO and Fig, 9 shows FTIR spectra of (a) RGO, (b) vinylsilane-functionalized RGO and (c) PMHS @RGO.

All FTIR spectra show the bands at -2950 cm ¹, which were assigned to C-H stretching vibrations of -CH₃ and -CH₂. The characteristic features of vinyl-functionalization of nanoadditives showed the bands at approximately 1629 cm ¹ which were associated with the characteristic absorption peaks of C=C stretching vibrations. The bands at approximately 1168 and 1089 cm ¹ were assigned to the Si-O-C asymmetric and Si-O-C symmetric stretching vibration absorption, respectively. The band at approximately 941 cm ¹ was related to the symmetrical stretching of the Si-C bond. And the bands at approximately 1072 and approximately 806, cm ¹ were assigned to the Si-O-Si symmetric stretching vibration. Example 3B: TEM

Figures 10 to 13 show a set of the representative TEM images of vinylsilane functionalized nanoadditives prepared by silylation. Fig. 10 shows a TEM micrograph of vinylsilane- functionalized SiNP, Fig. 11 shows TEM micrographs of (a) GO and (b) vinylsilane- functionalized GO, Fig. 12 shows a TEM micrograph of vinylsilane-functionalized RGO, and Fig. 13 shows TEM micrographs of samples of (A) rough clay and (B) vinylsilane- functionalized clay. The characteristic silica shell was found on the surface of nanoadditives, such as CNT, GO, RGO and clay, respectively. Example 4: Superhydrophobic Coating of A Substrate

The straightforward "one -pot" synthesis of nanoadditive modified polymeric materials is schematically depicted in Fig. 2. The vinyl-functionalized nanoadditives (202) reacted with polymethylhydrosiloxane (PMHS) (204) in the presence of a catalytic amount of Pt catalyst in toluene to form the nanocomposite material (206). The nanoadditives include POSS (212), SiNP (214), CNT (216), GO or RGO (218) and clay (220). PMHS was used as polymer matrix, which has 25 to 50 methylhydrosiloxane units in its polymer structure. The multiple reaction sites offer strong covalent bonding between nanoadditives and polymer matrix, preventing phase separation in the final hybrid materials. The nanoadditive modified PMHS materials were dispersed into toluene to form a coating solution. The coating solution can be directly applied onto the textile substrate using dip- coating. The coated textile substrates were dried for a few hours in a fume hood and subsequently placed in an oven for drying at 60 °C overnight.

The water contact angle measurement revealed that cotton fabrics coated with nanoadditive - PMHS hybrids showed a nearly sphere -like water droplet, as shown in Fig. 14. The images show 5 uL drops of water on (A) PMHS @POSS, (B) PMHS @SiNPs, (C) PMHS @CNT, (D) PMHS @Clay, (E) PMHS @ GO and (F) PMHS @RGO. The nanoadditives were found to significantly affect the superhydrophobicity of coated textiles. The average contact angles on the cotton surfaces coated with PMHS@SiNP, PMHS@POSS, PMHS@CNT, PMHS@RGO, PMHS@Clay, and PMHS@GO were about 130°, about 150°, about 160°, about 160°, about 170° and about 170°, respectively. Notably, the contact angle increased as the nanoadditives were changed from zero-dimensional to two-dimensional structure.

This trend can be explained by the crosslinking density of linear polymer matrix with the two- dimensional nanoadditives with more surface area than zero-dimensional nanoadditives. Spherical water droplets (5 μί) were stable and were able to maintain their spherical morphology on the coated substrates until they evaporated. However, no contact angle could be observed when pure water was dropped onto uncoated substrates, where the water spread and was absorbed into the substrate. In contrast, a low contact angle could be observed for textile substrates coated with pure PMHS at the same concentration. The sizes and surface area of the nanoadditives correlated strongly with their crosslinking efficiencies and physical properties. It was observed that an oily feeling is detected when the textile substrate is coated with zero- dimensional nanoadditives POSS and SiNPs hybrid materials, indicating incomplete crosslinking between the nanoadditives and the polymers.

Example 5: Characterization of Superhydrophobic Coating

The morphology and surface properties of textiles coated with PMHS modified with nanoadditive were examined. Fig. 15 shows a set of representative SEM images showing the morphology change in cotton fibre before and after coating with various coating materials of the present disclosure, where (A) uncoated, (B) coated with PMHS @SiNPs, (C) coated with PMHS @POSS, and (D) coated with PMHS @Clay. Pristine un-coated textile substrates possess a rather rough surface as shown in Fig. 15(A). Consistent with contact angle analysis, a set of distinct smooth silica shells contour of the original shape of the textile weave as observed by SEM images, which correspond to the coating layer of polymeric hybrid materials.

The coating solutions were applied to various natural or man-made fibers, e.g. polyester, cotton, asbestos cloth et al, using the same dip-coating method. As shown in Fig. 16, the superhydrophobicity was also observed on three different knitting type of textiles, (1) knit, (2) nonwoven and (3) woven. The images show drops on textiles (A) uncoated, (B) coated with PMHS @POSS, (C) coated with PMHS @ Silica, (D) coated with PMHS @CNT, (E) coated with PMHS @GO, (F) coated with PMHS@RGO, and (G) coated with PMHS @Clay. The knitting pattern of a textile has significant impact on the water contact angles. Polymers modified with one -dimensional and two-dimensional nanoadditives demonstrated consistent water contact angles on various type of textiles. In contrast, the water contact angles of polymers modified with zero-dimensional nanoadditives (POSS and SiNPs) were significantly correlated to the morphology of the textile. In particular, the water contact angle decreased to 90-130° for textile substrates that were sparsely knitted.

The results above correlate with the reported mechanism of how the lotus leaf has its hydrophobic properties. In comparison with coatings applied to flat surfaces, the coating materials of the present disclosure take advantage of the inherent morphological anisotropy of textile substrates which have a hierarchical roughness in the micro scale, to further enhance the surface hydrophobicity. Based on such superhydrophobic features, a mechanism of how the coatings of the present disclosure works is proposed, as depicted in Fig. 17. Without being bound to theory, it is proposed that the coatings of the present disclosure enhances the surface roughness and surface chemistry of the textile substrate to mimic lotus leaves.

Superhydrophobic textile coatings that confer properties such as stain resistance and self- cleaning capabilities to the substrate to be coated have led to various applications in the textile industry. The coating solutions were applied to fibers, e.g. polyester, cotton, asbestos cloth et al, using the same dip-coating method. In a control experiment, the coated textile substrates were also stained with pigmented water to test stain resistance. As shown in Fig. 18(A), the cotton glove coated with PMHS@Clay was easily cleaned after immersion into a stained solution by rinsing with water.

Further, Fig. 18(B) shows that unlike conventional coatings of this kind, the coating material PMHS@Clay as disclosed in the present application does not change the white colour of the textile substrate.

The adsorption of contaminating matter can alter the performance of biomedical implants and devices which can lead to patient infection, shortened durability, and increased healthcare cost in the replacement of devices. Currently organopolysiloxanes elastomers are most widely used in non-biocidal fouling-coating without releasing toxic chemicals into the organism or the marine environment. Results showed that PMHS@Clay coated cotton have powerful antibacterial activity against S. aureus. The bacterial inhibition of PMHS@Clay coated cotton against bacteria S .aureus was tested via disk-diffusion method. The results were shown in Fig. 18(C). PMHS@Clay coated cotton without coating was used as control. According to Fig. 18(C), little inhibition was observed on bacterial plates treated with coated cotton textile. The excellent antibacterial ability of the coating here suggests that it has significant potential for fabrics in anti-fouling of organic contamination applications.

The self-cleaning test of the PMHS@Clay coated cotton is shown in Fig. 18(D) that the water dropped on the uncoated cotton surface were difficult to carry away the dust when tilting 10°. However, when the PMHS@Clay coated cotton titling 10°, the water droplets could easily roll off, leaving an clean surface as shown in Fig. 18(D). Due to the contact area of dirty particles to the PMHS@Clay coated cotton decreasing, the adherence strength between dirty particles and PMHS@Clay coated cotton surface decreases, too, so the dirt on nanostructure materials is easier taken away by water. This self-cleaning test validates that the developed method has successfully mimicked the self-cleaning mechanism of lotus leaf.

Example 6: Stability of Superhydrophobic Coating

The long-term stability of PMHS@Clay hybrid materials as a superhydrophobic coating in harsh environments and laundry conditions was examined. Spherical water droplets with an average contact angle of about 170° was still observed after immersing the coated textile substrate in aqueous H₂S0₄ (pH = 1) for 1 month (Fig. 19). Further, the superhydrophobic property was maintained for one week upon treatment with aqueous KOH (pH = 14) (Fig. 20).

Furthermore, the superhydrophobic coating also showed good resistance to boiling water. Experimental results showed that the coated textile substrate had no change in superamphiphobicity after boiling the coated textile substrate in water for 2 hours. Therefore, the coating not only granted the textile substrate super water-repellent properties, but also showed excellent chemical resistance.

In addition, the superhydrophobic stability of the coating in laundry conditions was examined. As shown in Fig. 21, the contact angles of fibres coated with PMHS@clay decreased slightly but still remained to be greater than 160° even after being stirred in 500 mL water using an egg shaped stirring bar (TEFLON®, 3/4 x 1 5/8 in) at 900 rpm for one week. This showed that the coating not only granted the textile substrate a super water-repellent feature, but also showed excellent durability against both washing and abrasion.

Fig. 22 shows representative set of SEM images of the morphology changes of cotton fibre coated with PMHS @Clay after washing for different lengths of times. Although the silica shell became cracked, especially at the fibre connections, the silica shell on individual fibres was maintained. The surface morphology was qualitatively consistent with the water contact angles as measured in Fig. 21. Industrial Applicability

The coating material of the present disclosure and the substrate coated with the coating material have a wide range of applications in surgical tools, medical devices, textiles (such as swimwear and military clothing), maritime industry and in environmental applications. In particular, applications in agriculture may include seed/crop covers, bags, shade materials, irrigation systems, pond liners and hoses, applications in clothing may include shoe upper and linings, artificial leather/bags/belts, rainwear, garment linings, backing/stiffeners, gloves and hats, applications in geotextiles may include settling pond liners, irrigation liners, landfill liners and covers, soil stabilizers and erosion barriers, applications in construction may include safety fencing, wind covers, safety vests, conveyer belting and truck covers, applications in home furnishings may include upholstery, trim, carpet backing, drapery backing, bedding and artificial leather, applications in industry may include conveyer belts, filtration, barrier materials, field covers, abrasive backing and mechanical rubber goods, as well as applications in medical equipment, tents, transportation, sport, leisure, packaging and protective equipment. The coating material of the present disclosure and the substrate coated with the coating material may have applications in materials that require antifouling, anti-contamination, antibacterial, anti-ice and self-cleaning properties.

It will be apparent that various other modifications and adaptations of the invention will be apparent to the person skilled in the art after reading the foregoing disclosure without departing from the spirit and scope of the invention and it is intended that all such modifications and adaptations come within the scope of the appended claims.

Claims

1. A polymeric coating material comprising a nanoadditive covalently bound to an organopolysiloxane, wherein the nanoadditive comprises a) a nanoadditive substrate and b) a linker covalently bound by a silyloxy moiety to the nanoadditive substrate at one end and said organopolysiloxane at the other end.

2. The coating material of claim 1, wherein the organopolysiloxane comprises hydrophobic groups, which are preferably selected from alkyl, alkenyl, alkylaryl or aryl, most preferably Ci to Ci₀-alkyl, Ci to Ci₀-alkenyl, Ci to Cio-alkyl- C₆ to Ci₀-aryl or C₆ to Cio-aryl.

3. The coating material of any of the preceding claims, wherein the content of nanoadditive substrate is less than about 3 % by weight, preferably less than about 0.5 % by weight and most preferably between about 0.005 and 0.5 % by weight, of the organopolysiloxane .

4. The coating material of any of the preceding claims, wherein the polymeric organopolysiloxane, prior to covalent bonding to the linker, comprises repetitive silicon- hydrogen moieties.

5. The coating material of any of the preceding claims, wherein the polymeric organopolysiloxane, prior to covalent bonding to the linker, comprises one or more, preferably from 3 to 200, units of formula (I) or (la) in the polymer chains

R¹

I

/† R¹

H

(la)

6. The coating material of the preceding claims 4 or 5, wherein the polymeric organopolysiloxane is poly(methylhydrosiloxane) (PMHS).

7. The coating material of any of claims 4 to 6, wherein the poly(methylhydrosiloxane) is of representative formula (II)

wherein R¹ represents methyl, and n is an integer selected so that the poly(methylhydrosiloxane) has a molecular weight range of about 390 to about 10,000.

8. The coating material of claim 1, wherein the nanoadditive substrate, prior to being linked to the organopolysiloxane, is surface-functionalized with vinyl groups, preferably by using trimethoxy(vinyl)silane as a silane reagent.

9. The coating material of claim 1, wherein the nanoadditive substrate is a particle of 10 nm to 10 μιη size.

10. The coating material of claim 8 or 9, wherein the nanoadditive substrate is selected from the group consisting of carbon nanotubes, graphene oxides and reduced graphene oxides, clay , silica-dioxide nanoparticles or a polyhedral oligomeric silsesquioxane.

11. The coating material of claim 1, wherein the silyloxy linker, before forming the covalent bonds, comprises a nonhydrolyzable moiety, preferably a vinyl group, and a silyloxy moiety.

12. The coating material of claim 11, wherein the silyloxy moiety is covalently bound to the nanoadditive substrate via a silyl-ether bridge.

13. The coating material of claim 12, wherein the nonhydrolyzable moiety, preferably a vinyl group, is covalently bound to the polymeric organopolysiloxane.

14. A method for making a coating material, comprising the steps of a) reacting a silane reagent, preferably a vinyl trialkoxy silane, with a nanoadditive substrate, which is optionally surface functionalized with hydroxyl groups, b) covalently bonding the reaction product to an organopolysiloxane or its precursors optionally in the presence of a catalyst.

15. The method of claim 14, wherein the catalyst is selected from group 10 elements.

16. The method of claim 15, wherein the catalyst comprises platinum.

17. Use of the coating material of any of the preceding claims for coating a substrate, preferably natural or man-made fibers.

18. A method of coating a substrate, preferably a fiber, comprising the steps of: a) dissolving a coating material according to any of the preceding claims in a solvent to form a coating solution; b) immersing said substrate in the coating solution; and c) removing said substrate from the coating solution.

19. The method of claim 18, further comprising the step of (d) drying the substrate from step (c) to remove the solvent.

20. The method of claim 19, wherein the solvent used is selected from the group consisting of toluene, dichloromethane and chloroform.

21. A coated substrate obtainable by any of the methods of claims 18 to 20 having superhydrophobic properties.

22. The coated substrate of claim 21 for use in textile processing, packaging materials, paper industry, antifouling clothing, sportswear and boat sails.

23. A polymer nanoadditive composite comprising a nanoadditive covalently bound to an organopolysiloxane, wherein the nanoadditive comprises a) a nanoadditive substrate and b) a linker covalently bound by a silyloxy moiety to the nanoadditive substrate at one end and said organopolysiloxane at the other end; and wherein the organopolysiloxane comprises one or more non-terminal units of formula (III) in the polymer chains

wherein R¹, is independently selected from hydrogen, Ci to Ci₀-alkyl, Ci to Ci₀-alkenyl, Ci to Cio-alkyl- C₆ to Ci₀-aryl or C₆ to Cio-aryl; and R¹ is preferably methyl; and X is the bond to the linker.

24. The polymer nanoadditive composite according to claim 23, wherein the organopolysiloxane, prior to covalent bonding to the linker, is a poly(methylhydrosiloxane) of representative formula (II)

25. The polymer nanoadditive composite according to claim 23, wherein the nanoadditive is selected from the group consisting of carbon nanotubes, graphene oxides and reduced graphene oxides, clay, silica-dioxide nanoparticles or a polyhedral oligomeric silsesquioxane.