NOVEL PROCESS FOR OBTAINING SUPERHYDROPHOBIC OR SUPERHYDROPHILIC SURFACES

Abstract

The present invention relates to a process for texturing surfaces providing the latter with superhydrophobic, superoleophobic, superhydrophilic or even superoleophilic properties. This process comprises i) a step of texturing the surface (via the deposition of nanoparticles of different sizes); ii) a step of curing the surface thus textured (with a curing agent); and, optionally, a step of modifying the properties of the surface with perfluorinated (and therefore hydrophobic) molecules. This process is suitable, inter alia, for treating transparent and/or heat-sensitive materials and surfaces. Specifically, none of the steps of the process use a temperature higher than 100 C. Thus, the process of the invention is particularly suitable for treating transparent surfaces composed of non-mineral materials, such as polycarbonate for example, as it wilt affect neither their transparency nor their optical properties.

Claims

1. Process for coating surfaces comprising at least the steps: a) Depositing at least two nanoparticle populations, of different sizes, on a surface to be treated, and b) Cross-linking the nanoparticle-coated surface using a transition metal alkoxide, in acidic solution, said process not involving heating said surface above 180 C.

2. Process according to claim 1, characterized in that said nanoparticle populations are mixed with said cross-linking agent before being deposited on said surface.

3. Process according to claim 1, characterized in that said nanoparticle populations are deposited successively on said surface.

4. Process according to claim 3, characterized in that said surface is treated with the cross-linking agent after each deposition of nanoparticles.

5. Process according to any one of claim 1 or 2, characterized in that step a) contains the following sub-steps: a1) Treating a first nanoparticle population with an adhesion agent, a2) Contacting this first nanoparticle population with one or more other nanoparticle populations, a3) Optionally, purifying the particles thus formed, a4) Depositing the particles formed in steps a2) or a3) on said surface.

6. Process according to claim 5, characterized in that said adhesion agent is an isocyanate or epoxide compound, preferably a silane isocyanate compound or a silane epoxide compound.

7. Process according to claim 3 or 5-6, characterized in that said surface is treated with the cross-linking agent after all of said nanoparticles have been deposited.

8. Process according to one of claims 5 or 6, characterized in that the nanoparticles formed in steps a2) or a3) are mixed with said cross-linking agent before step a4).

9. Process according to any one of claims 1 to 8, characterized in that said alkoxide is tetraethyl orthosilicate (TEOS).

10. Process according to any one of claims 1 to 9, characterized in that said surface consists of silicon, aluminum, germanium, oxides thereof or alloys thereof, or of polycarbonate, polymethyl methacrylate (PMMA), polypropylene, polyvinyl acetate (PVA), polyamides (PA), polyethylene terephthalate (PET), polyvinyl alcohols (PVAl), polystyrenes (PS), polyvinyl chlorides (PVC) or polyacrylonitriles (PAN).

11. Process according to any one of claims 1 to 10, characterized in that one of the two nanoparticle populations has a diameter comprised between 50 and 200 nm, and the other a diameter comprised between 5 and 50 nm.

12. Process according to any one of claims 1 to 11, characterized in that said nanoparticles consist of silicon, germanium, alumina, titanium, oxides thereof or alloys thereof, or polycarbonate.

13. Process according to any one of claims 1 to 12, characterized in that said surface is activated by a treatment with ozone, UV or plasma before the deposition of said nanoparticles.

14. Process according to claim 13, characterized in that, when said surface consists of a polymer, said surface is coated with an adhesion primer layer, after being activated and before the deposition of said nanoparticles, said adhesion primer layer preferably consisting of a transition metal alkoxide such as tetra ethoxy silicate (TEOS).

15. Process according to any one of claims 1 to 14, characterized in that the deposition of said nanoparticles is carried out by dip-coating, spin-coating, spray, flow-coating or wiping, preferably by dip-coating or by spray.

16. Process according to any one of claims 1-15, characterized in that said nanoparticles are not coated with an agent creating weak bonds before being deposited on the surface, or before being mixed with said cross-linking agent, said agent being for example an amine compound.

17. Process according to any one of claims 1-16, characterized in that said nanoparticles are coated with an agent creating strong or covalent bonds, before being deposited on the surface or before being mixed with said cross-linking agent, said agent being for example 3-(trimethoxysilyl)propyl isocyanate (TMS-NC0), 3 -(triethoxysilyl)propyl isocyanate, 3 -glycidoxypropyltriethoxysilane or 3 -glycidoxypropyltrimethoxysilane (GPTMS).

18. Process according to any one of claims 1-17, characterized in that the deposition of said nanoparticles on said surface is carried out by dip-coating, spin-coating, spray, flow-coating or wiping, preferably by dip-coating or by spray.

19. Process according to any one of claims 1 to 18, characterized in that the successive or simultaneous deposition by dip-coating of said nanoparticles is carried out at least twice, preferably at least five times.

20. Process according to any one of claims 1 and 3-19, characterized in that the deposition of said cross-linking agent is carried out by dip-coating, spin-coating, spray, flow-coating or wiping, preferably by dip-coating or by spray.

21. Process according to any one of claims 5-15 and 16-20, characterized in that the deposition of said adhesion agent is carried out by dip-coating, spin-coating, spray, flow-coating or wiping, preferably by dip-coating or by spray.

22. Process according to any one of claims 1-21, characterized in that it contains the following steps: i) depositing said nanoparticles successively according to claim 3, or mixed with the cross-linking agent according to claim 2, or adhered according to claim 5, ii) depositing nanoparticles having a diameter comprised between 5 and 80 nm and then said cross-linking agent, or depositing nanoparticles having a diameter comprised between 5 and 80 nm mixed with said cross-linking agent.

23. Process according to any one of claims 1 to 22, characterized in that said surface is coated finally with a layer of hydrophobic organic molecules, preferably perfluorinated.

24. Process according to claim 23, characterized in that said organic molecules are of formula: ##STR00007## wherein R represents a linear or branched C.sub.1-C.sub.4 alkyl group.

25. Process according to any one of claims 23 to 24, characterized in that said hydrophobic organic molecules are deposited on said surface by dip-coating, spin-coating, spray, flow-coating or wiping, preferably by dip-coating, by evaporation or by spray.

26. Compound of formula: ##STR00008## wherein R represents a linear or branched C.sub.1-C.sub.4 alkyl group.

Description

FIGURE LEGENDS

[0227] FIG. 1 presents images obtained by a scanning electron microscope (FEGSEM) of deposits made according to the protocol of Example 1 (dip-coating the glass slide in an aqueous solution of 60 nm diameter silica nanoparticles then grafting of fluorinated silane molecules).

[0228] FIG. 2 presents FEGSEM images of deposits prepared with ethanol as solvent in the bath used for deposition by the dip-coating technique (dip-coating the glass slide in a solution of 60 nm diameter silica nanoparticles then grafting of fluorinated silane molecules).

[0229] FIG. 3 presents FEGSEM images of deposits prepared by the dip-coating technique from a mixture containing 50% by volume of 0=100 nm silica nanoparticles (0.5% by weight in water) and 50% by volume of 0=15 nm silica nanoparticles (0.5% by weight in water).

[0230] FIG. 4 presents FEGSEM images of deposits prepared by the sequential dip-coating technique of 100 nm silica nanoparticles and 15 nm nanoparticles.

[0231] FIG. 5 presents FEGSEM images of deposits prepared by the sequential dip-coating technique of 100 nm silica nanoparticles and 15 nm nanoparticles with an intermediate step of APTES functionalization.

[0232] FIG. 6 presents FEGSEM images of deposits prepared by the sequential dip-coating technique from solutions of 100 nm silica nanoparticles and 15 nm nanoparticles with an intermediate step of APTES functionalization, for various nanoparticle concentrations: (A) 100 nm: 0.5% by weight in water; 15 nm: 0.5% by weight in water, (B) 100 nm: 0.5% by weight in water; 15 nm: 0.25% by weight in water, (C) 100 nm: 1% by weight in water; 15 nm: 0.25% by weight in water and (D) 100 nm: 1% by weight in water; 15 nm: 0.5% by weight in water.

[0233] FIG. 7 presents FEGSEM images of deposits prepared by the sequential dip-coating technique of suspensions of 100 nm and 15 nm silica nanoparticles in ethanol. An intermediate step of APTES functionalization was carried out.

[0234] FIG. 8 shows the transmittance as a function of wavelength of the superhydrophobic glass substrates and coatings prepared.

[0235] FIG. 9 presents images obtained by a CCD camera, showing (A) on a superhydrophobic and transparent coating without TEOS treatment: scratching by a stylus, (B) on a coating after TEOS treatment: absence of scratching by the stylus.

[0236] FIG. 10 shows the FEGSEM characterization of a nanoparticle coating not set by the cross-linking agent (TEOS) having undergone an adhesive tape test: the region delimited by a square indicates the region where the adhesive tape was pulled off.

[0237] FIG. 11 shows the FEGSEM characterization of a nanoparticle coating after the TEOS consolidation step after the adhesive tape test: the region delimited by a square indicates the region where the adhesive tape was pulled off.

[0238] FIG. 12 shows the FEGSEM characterization of a nanoparticle coating after the TEOS consolidation and thermal annealing steps, after the adhesive tape test: the region delimited by a square indicates the region where the adhesive tape was pulled off

[0239] FIG. 13 shows the FEGSEM characterization of the cotton-swab rubbing test carried out on a nanoparticle coating not having undergone the TEOS consolidation step: the region delimited by a square indicates the region evaluated.

[0240] FIG. 14 shows the FEGSEM characterization of the cotton-swab rubbing test carried out on a nanoparticle coating having undergone a TEOS consolidation step: the region delimited by a square indicates the region evaluated.

[0241] FIG. 15 shows the FEGSEM characterization of the cotton-swab rubbing test carried out on a nanoparticle coating having undergone the TEOS consolidation and thermal annealing steps: the region delimited by a square indicates the region evaluated.

[0242] FIG. 16 presents the image of a glass sample having received a superhydrophilic treatment on the left portion and no treatment on the right portion. This glass was cooled to 20 C. then returned to the ambient environment to evaluate the effects of condensation on transparency.

EXAMPLES

1. Protocol for Depositing Particles of One Size

[0243] After cleaning a glass surface with detergent, 3-aminopropyl triethoxysilane (APTES) molecules were adsorbed by evaporation for 10 minutes in a vacuum desiccator (pressure=8 mbar). The equilibrium contact angle observed for these surfaces after functionalization and particle deposition is of about 40.

[0244] The particles are then deposited on the surface by the immersion-withdrawal technique (dip-coating) following the order of the following steps: [0245] Preparation of a particle suspension (60 nm diameter, 6 mg/mL) in water, [0246] Dip-coating (DC) the glass slide in the silica nanoparticle suspension (withdrawal speed: 10 mm/min to 100 mm/min), [0247] Grafting of fluorinated silane molecules (Diagram 1) for 18 hours in a vacuum desiccator at a pressure of 8 mbar, [0248] Annealing for 1 hour at 90 C.

##STR00006##

[0249] Diagram 1: Representation of the structural formula of the fluorinated silane molecule used in this example.

[0250] The FEGSEM characterization of the deposits obtained when the silica nanoparticles are suspended in water is presented in FIG. 1.

[0251] The results of this characterization show that the silica nanoparticles are distributed randomly on the glass surface with the formation of small agglomerations of particles in areas with no apparent order. It may also be noted that the particle density on the glass surface varies very little with the withdrawal speed.

[0252] In order to remedy the nanoparticle agglomeration problem, the particle-solvent interaction was modulated by replacing water with ethanol in the bath used for deposition by the dip-coating technique.

[0253] The results of the FEGSEM characterization of these deposits are presented in FIG. 2.

[0254] The analysis of the results shows that the use of ethanol as solvent for the nanoparticles makes it possible to obtain on the glass surface particles which are randomly distributed but better dispersed, and with very few aggregates.

[0255] After functionalizing these substrates with fluorinated silane molecules for 18 hours, the equilibrium contact angles observed after 1 hour of annealing at 90 C. are 140 .

[0256] This shows that by adopting a single nanoparticle size, it is not possible to obtain surfaces the angle of which is greater than 150 under the test conditions.

[0257] In this case, no mechanical resistance was obtained (damage to the coating as of the first rubbing due to the absence of cross-linking because the nanoparticles deposited were treated directly after deposition with the hydrophobic agent).

[0258] In addition, an identical experiment was carried out with 100 nm particles and the addition of TEOS before evaporation of the silane-PFPE. The results obtained for this surface are presented in the table below.

TABLE-US-00001 Test 9-1 Material CA () (loss of contact angle in )* Glass 137 40 *See experimental conditions of Example 9

[0259] The result of this example shows the poor behavior of the coating with a formulation containing only one particle population.

2. Protocol for Depositing Nanoparticles of Two Different Sizes

[0260] In this example, the surfaces were washed and treated with APTES according to the protocol presented for substrate preparation when only one size of nanoparticles is deposited (see Example 1).

[0261] The deposition by the dip-coating technique was carried out with silica nanoparticle populations of two different average diameters: 100 nm nanoparticles (NP100) having a diameter size distribution comprised between 70 and 100 nm, and 15 nm nanoparticles (NP15) having a diameter size distribution comprised between 10 and 15 nm. The withdrawal speed is 40 mm/min. The grafting of the surfaces with the superhydrophobic molecules was carried out for 18 hours in a vacuum desiccator.

[0262] Annealing was carried out for 1 hour at 90 C.

2.1. Simultaneous Deposition with an Equal Volume of 100 nm and 15 nm Diameter Silica Nanoparticles

[0263] After the deposition of an APTES layer (see Example 1), the glass substrates were plunged into a silica nanoparticle solution containing a mixture with an equal volume of 100 nm nanoparticles (0.5% weight concentration) and 15 nm nanoparticles (0.5% weight concentration) in water. The FEGSEM characterization of the deposits obtained is presented in FIG. 3.

[0264] FIG. 3 shows the presence of the two sizes of silica nanoparticles on the glass surface: those of 15 nm are much more numerous than those of 100 nm. These images also show a low degree of surface coating. We note that the preparation of a nanoparticle coating in a single step by dip-coating by mixing the two nanoparticle sizes in equal volume and weight concentration does not lead to superhydrophobic surfaces. The equilibrium contact angle observed after 18 hours of exposure to the fluorinated silane molecule is 128 and the transmittance is 100% relative to the reference glass.

2.2. Sequential Deposition of 100 nm and 15 nm Diameter Silica Nanoparticles

[0265] After the deposition of an APTES layer (see Example 1), a first deposition by the dip-coating technique (withdrawal speed=40 mm/min) in a solution containing 100 nm nanoparticles (0.5% weight concentration) in water was carried out. After drying the substrates, a second deposition by the dip-coating technique (withdrawal speed=40 mm/min) was carried out with 15 nm silica nanoparticles (0.5% weight concentration) in water. The FEGSEM characterization of the deposits prepared is presented in FIG. 4.

[0266] Following the sequential deposition, note may be made of the coexistence of the two sizes of silica nanoparticles on the surface of the glass substrate with more large nanoparticles coating the surface. In parallel, note may be made of the absence of small particles on the surface of the large ones. Furthermore, FIG. 4 shows the existence of a dual scale of roughness. For these structures, the equilibrium contact angle observed after 18 hours of exposure to the fluorinated silane molecule is about 150 and the transmittance is 100%.

2.3. Sequential Deposition of 100 nm and 15 nm Diameter Silica Nanoparticles with an Intermediate Step of Functionalization of the Surface with APTES Molecules.

[0267] In the same manner as in the protocol used for the two preceding depositions, the glass substrates were first washed and then functionalized with APTES molecules. A first deposition by the dip-coating technique (withdrawal speed=40 mm/min) was carried out using a solution containing 100 nm nanoparticles (0.5% weight concentration) in water.

[0268] After drying the substrate, an additional step of functionalization of the substrates was carried out with APTES molecules under vacuum in a desiccator for 10 minutes.

[0269] After this step, a second deposition cycle was carried out by the dip-coating technique (withdrawal speed=40 mm/min) using an aqueous solution of 15 nm silica nanoparticles (0.5% weight concentration).

[0270] The FEGSEM characterization of the deposits obtained is presented in FIG. 5.

[0271] The FEGSEM images of FIG. 5 show that a better roughness is obtained for this third process. Indeed, by introducing an intermediate step of APTES functionalization, the adhesion between the large and the small particles was increased. This made it possible to obtain raspberry-shaped particles with the small particles coating the surface of the large particles. The equilibrium contact angle observed for these deposits after 18 hours of exposure to the fluorinated silane molecule is greater than 150 and the transmittance is 100% (in the visible wavelength range).

3. Protocol for Depositing Nanoparticles of Two Different SizesEffect of Particle Concentration

[0272] While retaining the experimental protocol of Example 2.3, we varied the concentration of the 15 nm silica nanoparticles while keeping the weight concentration of the 100 nm nanoparticles equal to 0.5%.

[0273] To ensure better adhesion between nanoparticles and between the nanoparticles and the substrate, and thus to improve the mechanical properties of the deposits, a sol-gel deposition of silica was carried out before the deposition of the hydrophobic layer. This deposition also was carried out by the dip-coating technique (withdrawal speed =40 mm/min, soaking =2 hours).

[0274] The FEGSEM images of the deposits prepared are presented in FIG. 6.

[0275] FIG. 6 shows that when the concentration of one nanoparticle size increases, the coating of the surface increases. Two situations may be distinguished: [0276] a) when the concentration of the 100 nm nanoparticles increases, the coating of the substrate increases. [0277] b) when the concentration of 15 nm nanoparticles increases, the coating of the larger nanoparticles increases.

[0278] From these experiments, it emerges that the best surface roughness is obtained with a weight concentration of 0.5% and 0.25% for the suspensions of 100 nm and 15 nm nanoparticles, respectively.

4. Protocol for Depositing Nanoparticles of Two Different SizesEffect of Solvent and Cross-Linking Agent

[0279] The nanoparticles agglomerate when water is used as solvent. While retaining the experimental protocol of Example 2.3, we varied the nature of the solvent (water and ethanol). We also optionally added a TEOS cross-linking phase before the deposition of the hydrophobic final layer.

[0280] The TEOS deposition is carried out by dip-coating (speed=20 mm/min), with a soaking time of 2 hours. The solution used is a mixture of TEOS (1 volume) and ammonia (8 volumes) in ethanol.

[0281] FIG. 7 shows the FEGSEM images of the deposits produced.

[0282] These results, compared with those of Example 2.3, show that the particles have a less aggregated appearance, once deposited on the surface, when the deposition is carried out in ethanol as solvent.

[0283] The contact angle measurement was carried out at each step of the process mentioned in this example. An untreated glass surface gives water contact angles of about 20. The maximum contact angle that may be reached by the functionalization of planar glass surfaces with the fluorinated silane molecule of Diagram 1 is of about 110. After the step of texturing the glass surface with the various nanoparticle deposits, without TEOS deposition, and after deposition of the same fluorinated molecules, this angle is of about 150. After the deposition of TEOS and the fluorinated molecules, the equilibrium contact angle reaches 155 and the coating is superhydrophobic.

[0284] It arises from the results obtained in this example that the surface roughness is improved when the deposition is carried out with a 0.5% weight concentration of 100 nm nanoparticles and 0.25% of 15 nm nanoparticles in ethanol as solvent.

[0285] Furthermore, the contact angles are slightly greater when the deposition of the cross-linking agent (TEOS) is carried out.

5. Transparency

[0286] Transparency is expressed as a high transmittance near 100%. For the coating of Example 2.3, a transmission spectrum in the visible wavelength range was carried out. A transmittance of 100% was measured relative to the reference glass (FIG. 8). This result is expected, since the roughness of the coatings is less than 100 nm.

6. Methods for Cross-Linking TEOS:

[0287] 6.1 Comparison Between Surfaces Cross-Linked with TEOS in Acidic Medium and Basic Medium-Adhesive Tape Behavior Test.

[0288] The coating tested is similar to that is described in Example 2.3 It is set with either: [0289] a deposition of TEOS in basic solution by dip-coating (speed=40 mm/min), with a soaking time of 2 hours. The solution used in this case is a mixture of TEOS and ammonia in water, [0290] a deposition of TEOS in acidic solution by dip-coating (speed=20 mm/min), with a soaking time of 2 hours. The solution used in this case is a mixture of TEOS and HCl in a water/ethanol mixture at pH 2.

[0291] In basic conditions, the results show that, with or without thermal annealing, the superhydrophobic coating obtained does not resist the adhesive tape test. At the end of the test, no particles are visible on the surface.

[0292] In contrast, after treatment in acidic medium, the surface shows no degradation related to the adhesive force of the tape and, after the test, the nanoparticle film remains fully applied to the surface.

6.2 Optimization of the TEOS Concentration used in Acidic Medium

[0293] Brief protocol: [0294] 1) Pre-washing [0295] 2) 5 DC of NP100 [0296] 3) 3 DC of TEOS [0297] 4) 1 DC of NP15 [0298] 5) 1 DC of TEOS [0299] 6) Silane

TABLE-US-00002 TEOS concentration Test 9-3 (mM) CA () (loss of contact angle in )* 8 149 28 10 145 10 12 147 13 24 146 10 80 128 9 *See experimental conditions of Example 9

[0300] Conclusion: In these given experimental conditions, the optimal TEOS concentration value is between 10 and 24 mM.

7. Scratch Resistance

[0301] In order to characterize the mechanical properties of the coatings produced and, more precisely, the scratch resistance thereof, we used an optical profilometer provided with a diamond stylus (12.5 m radius). With this stylus, we applied to the substrate a maximum load of 15 mg. This load corresponds to a force of 147.1 N, or a pressure of 3061 g/cm.sup.2.

[0302] In this case, the samples were prepared according to the protocol of Example 6. TEOS was deposited in acidic conditions.

[0303] Without the TEOS deposition, the coatings produced scratched easily. But with this deposition, and thanks to the Si-O-Si bonds, these coatings remain intact after having applied a maximum pressure with the diamond stylus (FIG. 9).

8. Behavior of the Coating in the Adhesive Tape Test

[0304] In this test, double-sided adhesive tape was affixed on the coating and then pulled off in a single motion. This adhesive tape test is used to test the adhesion of nanoparticle films on the glass surface. In this example, none of the surfaces were treated with a hydrophobic compound to minimize the anti-adhesive effect of the superhydrophobic coating and to model the adhesion of the particles to the material.

[0305] Once the adhesive tape test is carried out, the surfaces are observed by FEGSEM and a comparison is made between the regions from which the tape was pulled off and the untested regions. The surfaces evaluated are the following: [0306] a) Deposition according to Example 2.3 without addition of a cross-linking agent [0307] b) Deposition according to Example 2.3 with addition of a cross-linking agent (TEOS in acidic medium) [0308] c) Deposition according to Example 2.3 with addition of a cross-linking agent (TEOS in acidic medium) and annealing at 80 C. for 6 hours.
a) Deposition According to Example 2.3 without Addition of a Cross-Linking Agent

[0309] In the case of a coating prepared according to the protocol of Example 2.3 and not having undergone the TEOS consolidation step, the nanoparticle film sticks easily to the adhesive tape (FIG. 10). The magnified region of FIG. 10b shows a region free of particles (in the square), whereas the unevaluated region has an arrangement of particles identical to the preceding examples.

b) Deposition According to Example 2.3 with Addition of a Cross-Linking Agent (TEOS in Acidic Medium)

[0310] In another test, the protocol of Example 2.3 was implemented and the surfaces were then cross-linked by adding TEOS. The results of the adhesive tape test on this sample (FIGS. 11a and 11b) show a very good resistance of the nanoparticle film to the force of the adhesive tape because the nanoparticle film remains applied to the surface after the test.

c) Deposition According to Example 2.3 with Addition of a Cross-Linking Agent (TEOS in Acidic Medium) and Annealing at 80 C. for 6 hours.

[0311] In a third test, an additional annealing of 6 hours at 80 C. was applied to a surface having undergone the same coating as in FIG. 11. The results presented in FIG. 12 show that the annealing step provides no major improvement to the resistance of the nanoparticle films with respect to FIG. 11.

9. Behavior of the Coating in the Rubbing Test Using a Cotton Swab Soaked with Isopropanol

[0312] This rubbing test makes it possible to evaluate the mechanical resistance of the surfaces having received a superhydrophobic coating. It consists in applying several types of rubbing to the surface and evaluating the changes in the contact angle on these surfaces after the rubbing phase. The tests carried out are: [0313] Test 9-1: Application of 100 dry rubs with a soft cloth attached to a 500 g mass distributed over 1 cm.sup.2 [0314] Test 9-2: Application of 100 dry rubs with a soft cloth attached to a 1000 g mass distributed over 1 cm.sup.2 [0315] Test 9-3: Application of 100 rubs with isopropanol-soaked cotton attached to a 100 g mass distributed over 1 cm.sup.2 [0316] Test 9-4: Application of 100 rubs with isopropanol-soaked cotton attached to a 500 g mass distributed over 1 cm.sup.2

[0317] Test 9-3 was applied to the surfaces of Example 8, namely: [0318] a) Deposition according to Example 2.3 without addition of a cross-linking agent, [0319] b) Deposition according to Example 2.3 with addition of a cross-linking agent (TEOS in acidic medium), [0320] c) Deposition according to Example 2.3 with addition of a cross-linking agent (TEOS in acidic medium) and annealing at 80 C. for 6 hours.

[0321] Once the rubbing is carried out, the surfaces are observed by FEGSEM and a comparison is made between the regions having undergone rubbing and the unrubbed regions.

a) Deposition According to Example 2.3 without Addition of a Cross-Linking Agent

[0322] When a coating is made only of silica nanoparticles without TEOS consolidation, the nanoparticles come off easily when rubbed with a cotton swab (FIG. 13).

b) Deposition According to Example 2.3 with Addition of a Cross-Linking Agent (TEOS in Acidic Medium)

[0323] In another test, the protocol of Example 2.3 was implemented and the surfaces were then cross-linked by adding TEOS. The FEGSEM characterization of the coatings prepared is presented in FIG. 14. It may be noted that the TEOS consolidation step provides a clear improvement of the nanoparticle films to resistance to the rubbing test using an isopropanol-soaked cotton swab.

c) Deposition According to Example 2.3 with Addition of a Cross-Linking Agent (TEOS in Acidic Medium) and Annealing at 80 C. for 6 hours.

[0324] In a third test, an additional annealing of 6 hours at 80 C. was applied to a surface having undergone the same coating as in FIG. 14. The results presented in FIG. 15 show that the annealing step provides no major improvement to the resistance of the nanoparticle films with respect to FIG. 14.

[0325] Consequently, this annealing step may be eliminated from our process for preparing nanoparticle films.

10. Protocol for Depositing Nanoparticles of Two Different Sizes with no Amino Silane-Type Adhesion Primer [0326] a. After cleaning a glass surface with a detergent, a first deposition by the dip-coating technique (withdrawal speed=100 mm/min) is carried out using a solution containing 100 nm nanoparticles (0.5% weight concentration) in alcohol. This step is repeated 5 times. The pieces are dried at 80 C. for 1 hour. [0327] b. A deposition of TEOS in acidic solution by dip-coating (speed=100 mm/min), with a soaking time of 2 hours, is carried out. The solution used is a mixture of TEOS and HCl (1 equivalent/5 equivalents) in a water/alcohol mixture at pH 2. The TEOS concentration in this bath is 10 mM. The pieces are dried at 80 C. for 1 hour. [0328] c. A second deposition cycle is carried out by the dip-coating technique (withdrawal speed=100 mm/min) using a solution in alcohol of 15 nm silica nanoparticles (0.5% weight concentration). The pieces are dried at 80 C. for 1 hour. [0329] d. A deposition of TEOS in acidic solution by dip-coating (speed=100 mm/min), with a soaking time of 2 hours, is carried out. The solution used is a mixture of TEOS and HCl (1 equivalent/5 equivalents) in a water/alcohol mixture at pH 2. The TEOS concentration in this bath is 10 mM. The pieces are dried at 80 C. for 1 hour. [0330] e. Grafting of fluorinated silane molecules for 18 hours in a vacuum desiccator, annealing for 1 hour at 80 C.

TABLE-US-00003 Sliding angle Test 9-1 Test 9-2 Test 9-3 Test 9-4 Material CA () () (loss in ) (loss in ) (loss in ) (loss in ) Glass 1 147 8 9 12 11 Glass 2 150 7 14

[0331] These results show that the superhydrophobic effect is achieved by this protocol and that the mechanical and chemical resistance is high.

11. Preparation of Raspberry Particles

[0332] For the needs for our tests, several families of raspberry particles were synthesized based on large silica particles onto which a chemical group was grafted. These particles are then contacted with smaller silica particles. The reactive groups presented are amines (Langmuir 2011, 27, 4594), epoxides (Nano Lett. 2005, 5, 2298) and isocyanates. [0333] 1) RNP(amine)

[0334] Into an anhydrous 100 mL round-bottom flask equipped with a condenser are introduced under argon NP100 (1 g) and 50 mL of ethanol (EtOH). The mixture is plunged into an ultrasonic bath for 30 minutes. APTMS (450 L) is then introduced with a syringe and the reaction medium is heated at reflux overnight. The reaction medium is cooled to room temperature (RT). After concentration under vacuum, the particles are suspended in 50 mL of toluene. The mixture is centrifuged at 3000 rpm for 10 minutes. The supernatant is discarded. This operation is repeated three times. The particles are then dried under vacuum at 50 C. for several hours. These particles are called NP100-NH.sub.2 particles.

[0335] Into an anhydrous 100 mL round-bottom flask equipped with a condenser are introduced under argon NP100-NH.sub.2 (500 mg), NP15 (315 mg) and 40 mL of EtOH. The mixture is plunged into an ultrasonic bath for 30 minutes, then the reaction medium is stirred overnight at 50 C. The mixture is cooled to RT. Ethanol is introduced in order to prepare a 0.5% weight solution.

2) RNP(epoxide)

[0336] Into an anhydrous 100 mL round-bottom flask equipped with a condenser are introduced under argon NP100 (1 g) and 50 mL of toluene. The mixture is plunged into an ultrasonic bath for 30 minutes. Silane epoxide (530 L) is then introduced with a syringe and the reaction medium is heated at 50 C. overnight. The reaction medium is cooled to RT. The mixture is centrifuged at 3000 rpm for 10 minutes. The supernatant is discarded. This operation is repeated three times. The particles are then dried under vacuum at 50 C. for several hours. These particles are called NP100-epoxide particles.

[0337] Into an anhydrous 100 mL round-bottom flask equipped with a condenser are introduced under argon NP100-epoxide (970 mg), NP15 (620 mg) and 20 mL of dimethylformamide (DMF). The mixture is plunged into an ultrasonic bath for 30 minutes, then the reaction medium is heated at reflux overnight. The mixture is cooled to RT. The mixture is centrifuged at 3000 rpm for 10 minutes. The supernatant is discarded. The particles are then dried under vacuum at 50 C. for several hours.

3) RNP(isocyanate)

[0338] Into an anhydrous 100 mL round-bottom flask equipped with a condenser are introduced under argon NP100 (1 g) and 30 mL of toluene. The mixture is plunged into an ultrasonic bath for 30 minutes. Silane isocyanate (490 mg) is then introduced with a syringe and the reaction medium is stirred overnight at RT. The mixture is centrifuged at 3000 rpm for 10 minutes. The supernatant is discarded. This operation is repeated three times. The particles are then dried under vacuum at 50 C. for several hours. These particles are called NP100-NCO particles.

[0339] Into an anhydrous 100 mL round-bottom flask equipped with a condenser are introduced under argon NP100-NCO (760 mg), NP15 (480 mg) and 15 mL of toluene. The mixture is plunged into an ultrasonic bath for 30 minutes, then the reaction medium is stirred overnight at reflux. The mixture is cooled to RT. The solvent is evaporated and the particles are then dried under vacuum at 50 C. for several hours.

12: Deposition of the Raspberry Particles on Glass Slides

[0340] Several different protocols were employed to deposit the particles on glass surfaces. Several variations were introduced into the protocol of Example 9 to prepare these surfaces. They particularly relate to the number of soakings in TEOS (3 soakings) and to the deposition of 15 nm nanoparticles followed by the deposition of TEOS (not carried out in Protocol 1, carried out in Protocol 2) carried out after deposition of the RNP.

[0341] The RNP used in this example are those prepared in Example 11.

[0342] Briefly, the experimental conditions are summarized below:

TABLE-US-00004 Protocol 1: Protocol 2: Pre-washing Pre-washing 5 DC of RNP 5 DC of RNP 3 DC of TEOS (10 mM) 3 DC of TEOS (10 mM) Silane 1 DC of NP15 1 DC of TEOS Silane

[0343] The pieces are dried at 80 C. for 1 hour after each dip-coating step and for 2 hours after deposition of the silane.

TABLE-US-00005 Test 9-3 RNP Protocol CA () (loss in ) Amino 1 145 Unstable 2 143 Unstable Epoxide 1 143 26 2 143 23 Isocyanate 1 134 16 2 134 17

[0344] The surfaces coated with raspberry particles all have contact angles of about 134 to 145. After abrasion, only the amino particles are unstable. They are degraded as of the first abrasion cycle. All the other particles exhibit intermediate behaviors. This shows that the electrostatic bonds created between the different particle populations by the amine groups are not sufficient to ensure that the material formed is resistant.

13: Activation of Polymer Materials by UV-Ozone

[0345] Polymeric pieces like PMMA are poorly wettable when they do not undergo activation treatment. This does not allow nanoparticle or TEOS solutions to spread satisfactorily and thus to coat the surfaces uniformly. Some of the surfaces were thus made wettable by UV-ozone activation. The apparatus used for UV/ozone activation is the ProCleaner Plus from BioForce Nanosciences. The rated output is 14.76 mW/cm.sup.2 at 1 cm from the source. The light intensity is distributed at 2% at 185 nm and at 45% at 254 nm. Before use, the apparatus preheated for 10 minutes. The PMMA sample, first washed with an aqueous detergent and dried, is exposed at 2.5 cm from the UV source for 10 minutes.

[0346] The contact angle of a 1 L water drop on the PMMA passes from about 80 before activation to 20 after activation.

14: Activation of Polymer Materials by Atmospheric Plasma

[0347] Polymeric pieces like PMMA are poorly wettable when they do not undergo activation treatment. This does not allow nanoparticle or TEOS solutions to spread satisfactorily and thus to coat the surfaces uniformly. Some of the surfaces were thus made wettable by atmospheric plasma activation. The apparatus used for plasma activation is the ULS spot (Acxys Technologies). Plasma is supplied by compressed air at a pressure of 4 bar. The plasma is activated at a power of 800 W. The substrates (PMMA or PC) to be treated are swept at a speed of 200 mm/s with a 4 mm step. Two applications were dispensed. The contact angle of a 1 L water drop passes from about 80 to 20.

15: Particle Deposition by Spray

15-1 On Glass

[0348] The surface preparation conditions are similar to Example 10. The same solutions were prepared and used. The nanoparticle solutions (NP100 and NP15) were then sprayed using a 50 mL atomizer placed 15 cm from the surface in a vertical position.

[0349] The protocol used is the following: [0350] Pre-washing [0351] 5 sprays of NP100 [0352] 1 spray of TEOS (10 mM) [0353] 1 spray of NP15 [0354] 1 spray of TEOS [0355] Silane

[0356] An annealing at 80 C. is carried out for 1 hour after each spray step and for 2 hours after deposition of the hydrophobic agent.

[0357] The results obtained are presented in the table below:

TABLE-US-00006 Test 9-3 Material CA () Sliding angle () (loss in ) Glass 151 16 16

[0358] This result shows that it is possible to obtain a textured surface on glass using this process by carrying out the successive deposition of different particle populations. This result also shows that this superhydrophobic treatment has good mechanical resistance properties.

15-2 On PMMA

[0359] The surface preparation conditions are similar to Example 10. The same solutions were prepared and used.

[0360] PMMA is first activated by UV-ozone and coated with a TEOS primer layer as defined in Example 20.

[0361] The nanoparticle solutions (NP100 and NP15) were then sprayed using a 50 mL atomizer placed 15 cm from the surface in a vertical position.

[0362] The protocol used is the following: [0363] Pre-washing [0364] UV-ozone activation [0365] 1 DC of TEOS [0366] 5 sprays of NP100 [0367] 1 spray of TEOS [0368] 1 spray of NP15 [0369] 1 spray of TEOS [0370] Silane

[0371] The pieces are dried at 80 C. for 2 hours after the dip-coating of TEOS, for 1 hour after each spray step and for 2 hours after deposition of the silane.

TABLE-US-00007 Test 9-3 Material CA () (loss in ) PMMA 146 20

16: Simultaneous Deposition of a Mixture of Different Sizes of Particles and of TEOS by Dip-Coating

[0372] Example 10 describes a sequential deposition of NP100, TEOS, then NP15 and TEOS. In this example, the process was shortened by mixing the particles with the TEOS solution.

[0373] Several variants were carried out. The variants relate to the number of soakings in TEOS (samples A: 3 soakings; samples B: 5 soakings) and to the deposition of 15 nm nanoparticles followed by the deposition of TEOS (not carried out in Protocol 1, carried out in Protocol 2) carried out after deposition of the nanoparticles in solution in TEOS.

[0374] Briefly, the experimental conditions are summarized below:

Protocol 1

[0375] 1) Pre-washing [0376] 2) Mixture of {NP100+NP15+TEOS solution (10 mM)}=Solution 1 [0377] 3) Dip-coating in Solution 1: 3 DC (A) and 5 DC (B) [0378] 4) Silane

Protocol 2:

[0379] 1) Pre-washing [0380] 2) Mixture of {NP100+NP15+TEOS solution (10 mM)}=Solution 1 [0381] 3) Dip-coating in Solution 1:3 DC (A) and 5 DC (B) [0382] 4) 1 DC of NP15 [0383] 5) 1 DC of TEOS [0384] 6) Silane

[0385] The pieces are dried at 80 C. for 1 hour after each dip-coating step and for 2 hours after deposition of the silane.

TABLE-US-00008 Experimental Test 9-3 conditions CA () (loss in ) A1 154 20 A2 154 14 B1 157 16 B2 157 13

[0386] These results show a superhydrophobic effect and a good mechanical and chemical resistance of the surfaces obtained by this process.

17: Simultaneous Deposition of a Mixture of Different Particle Sizes and of TEOS by Spray

[0387] The surface preparation conditions are similar to Example 16. The same solutions were prepared and used.

[0388] PMMA is first activated by UV-ozone and coated with a TEOS primer layer as defined in Example 20.

[0389] Briefly, the experimental conditions are summarized below:

Protocol

[0390] 1) Pre-washing/activation and deposition of the TEOS primer layer [0391] 2) Mixture of {NP100+NP15+TEOS solution (10 mM)}=Solution 1 [0392] 3) Spray-coating of Solution 1:3 sprays (A) and 5 sprays (B) [0393] 4) Silane

[0394] Solution 1 was sprayed using a 50 mL atomizer placed 15 cm from the surface in a vertical position.

[0395] The pieces are dried at 80 C. for 1 hour after each spray step and for 2 hours after deposition of the silane.

TABLE-US-00009 Test 9-3 Material Protocol CA () (loss in ) Glass A 139 7 Glass B 146 13 PMMA A 152 25 PMMA B 148 20

[0396] These results show the feasibility of spray deposition of different nanoparticle populations on various supports. The coating obtained has the same resistance properties, irrespective of the number of sprays used.

18: Simultaneous Deposition of a Mixture of Raspberry Particles and TEOS by Dip-Coating

[0397] For this example, the isocyanate RNP and the amino RNP prepared in Example 11 were used. They were mixed with a TEOS solution and then deposited on glass surfaces by the protocol described below.

Protocol 1:

[0398] 1) Pre-washing [0399] 2) Mixture of {RNP (0.5% by weight) in TEOS solution (10 mM)}=Solution 1 [0400] 3) 5 dip-coatings of Solution 1

[0401] 4) Silanization

Protocol 2:

[0402] 1) Pre-washing [0403] 2) Mixture of {RNP (0.5% by weight) in TEOS solution (10 mM)}=Solution 1 [0404] 3) 5 dip-coatings of Solution 1 [0405] 4) 1 dip-coating of NP15 [0406] 5) 1 dip-coating of TEOS [0407] 6) Silanization

[0408] The pieces are dried at 80 C. for 1 hour after each dip-coating step and for 2 hours after deposition of the silane.

TABLE-US-00010 Experimental Test 9-3 RNP conditions CA () (loss in ) Amino 1 143 36 2 143 18 Isocyanate 1 151 10 2 153 12

[0409] These results show that the process using isocyanate RNP performs much better than that using amino RNP because the contact angles are greater by 8 to 10 and their resistance to rubbing is greater. In the case of isocyanate RNP, adding an additional population of NP15 does not significantly improve the stability of the coating whereas it is necessary for the amino RNP. In the latter case, the stability is due to the accumulation of particle layers and not to the stability of the amino RNP themselves.

19: Simultaneous Deposition of a Mixture of Raspberry Particles and of TEOS by Spray

[0410] The surface preparation conditions are similar to those of Example 16. The same solutions were prepared and used. PMMA is first activated by UV-ozone and coated with a TEOS primer layer as defined in Example 20. The raspberry nanoparticles used are isocyanate nanoparticles as prepared in Example 11.

[0411] Briefly, the experimental conditions are summarized below:

Protocol:

[0412] 1) Pre-washing/activation and deposition of the TEOS primer layer [0413] 2) Mixture of {RNP (0.5% by weight) in TEOS solution (10 mM)}=Solution 1 [0414] 3) Spray-coating of Solution 1:3 sprays (A) and 5 sprays (B) [0415] 4) Silane

[0416] Solution 1 was sprayed using a 50 mL atomizer placed 15 cm from the surface in a vertical position.

[0417] The pieces are dried at 80 C. for 1 hour after each spray step and for 2 hours after deposition of the silane.

TABLE-US-00011 Test 9-3 Material Protocol CA () (loss in ) Glass A 154 24 Glass B 153 25 PMMA A 154 31 PMMA B 153 24

[0418] These results show the feasibility of spray deposition of raspberry nanoparticles on various supports. The coating obtained has the same resistance properties, irrespective of the number of sprays used and irrespective of the material.

20: Deposition of a TEOS Adhesion Primer on Polymers

[0419] After UV-ozone activation as described in Example 13, PMMA plates (55 cm.sup.2) are immersed in TEOS solutions at concentrations of (A) 10 mM, (B) 80 mM, (C) 250 mM in a water-alcohol mixture.

[0420] Next, the plates are used to deposit thereon a hydrophobic (protocol 1) or superhydrophobic (protocol 2) coating according to the following procedures:

Protocol 1:

[0421] 1) Pre-washing and UV-ozone activation [0422] 2) Deposition of TEOS primer by dip-coating at concentrations of (A) 10 mM, (B) 80 mM, (C) 250 mM [0423] 3) Silane

Protocol 2:

[0424] 1) Pre-washing and UV-ozone activation [0425] 2) Deposition of TEOS primer by dip-coating at a concentration of (B) 80 mM [0426] 3) Deposition of particles by dip-coating according to the procedure of Example 10 [0427] 4) Silane

[0428] The pieces are dried at 80 C. for 1 hour after each dip-coating step and for 2 hours after deposition of the silane.

TABLE-US-00012 Test 9-3 Protocol CA () (loss in ) A1 117 31 B1 116 5 C1 117 5 B2 144 13

[0429] These results show that, without particles on the surface (Protocol 1), it is possible to deposit a hydrophobic layer on PMMA first treated with a TEOS primer layer. This TEOS must have a sufficient concentration to allow the coating to behave satisfactorily on the surface. In this example, the behavior for a 10 mM concentration of TEOS is poorer than at higher concentrations. However, simply depositing an adhesion primer layer followed by functionalization by a hydrophobic layer is not sufficient to obtain the superhydrophobic property (contact angle less than 130).

[0430] The results of Protocol 2, in turn, show that it is possible to obtain superhydrophobic surfaces on PMMA first treated with a TEOS primer layer. In this example, Protocol 2 gives results similar to those obtained for glass (see Example 10).

21: Deposition of a Superhydrophilic Coating on Glass

[0431] In this example, isocyanate RNP prepared in Example 11 were used according to a process similar to that of Example 18, with the exception that the deposition of the final hydrophobic layer was not carried out.

[0432] They were mixed with a TEOS solution and then deposited on glass surfaces by the protocol described below.

Protocol:

[0433] 1) Pre-washing [0434] 2) Mixture of {RNP (0.5% by weight) in 10 mM TEOS solution}=Solution 1 [0435] 3) 5 dip-coatings of Solution 1

[0436] 4) Drying for 1 hour at room temperature (condition A) or at 80 C. (condition B)

TABLE-US-00013 Experimental Material conditions CA () Glass A <5 B <5

[0437] The superhydrophilic and anti-fogging effect is illustrated in FIG. 16, where the image shows glass cooled to 20 C. which remains transparent on the treated portion whereas it is clouded by condensation on the untreated portion.

[0438] The superhydrophilic property is also clearly shown by contact angles close to 0.