Superoleophobic Meshes with High Adhesion by Electrodeposition of

Article pubs.acs.org/JPCC

Superoleophobic Meshes with High Adhesion by Electrodeposition of Conducting Polymer Containing Short Perfluorobutyl Chains Thierry Darmanin, Jeanne Tarrade, Elena Celia, and Frédéric Guittard* Univ. Nice Sophia Antipolis, CNRS, LPMC, UMR 7336, Parc valrose, 06100 Nice, France ABSTRACT: Here, we report the possibility to obtain superoleophobic properties (θsunflower oil = 150° and θhexadecane = 136°) with high adhesion, by electrodeposition of conducting polymer containing short perfluorobutyl (C4F9) chains on stainless steel meshes. To obtain such properties, it is necessary to render stainless steel meshes sufficiently rough by applying a high deposition charge (Qs = 225 mC·cm−2) to deposit polymer micro- and nanostructures around the holes of the mesh. We also show that the mesh opening is extremely important and that the best mesh opening is 100 μm (we tested from 25 to 800 μm). These results are exceptional with polymer containing C4F9 chains and open new strategies to design fluorinated materials with low bioaccumulative potential.

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“re-entrant” structures such as mushroom and serif T structures. Indeed, examples of artificial superoleophobic surfaces were reported in the literature.16−26 The first example of superoleophobic surfaces was first reported by the group of Tsujii.16 They showed that the combination of fractal surface structures with fluorinated materials can lead to such properties. Afterward, many models and mathematic theories were established to understand this possibility.17−26 Now, it is admitted that the combination of fluorinated materials with particular structures, called re-entrant structures such as overhang, T-like, or mushroom-like structures, is a possible way to obtain superoleophobic properties.24−31 Indeed, using the Wenzel12 and Cassie−Baxter13 equations (equations using for the prediction of superhydrophobic properties), the presence of re-entrant structures can induce a change in the liquid−vapor interface, for example, from concave to convex.32−39 As a consequence, a supplementary energy barrier between the Wenzel and the Cassie−Baxter is induced making possible stabilization of the Cassie−Baxter state even with low surface tension liquids. In order to find strategies other than lithographic processes to produce superoleophobic surfaces, meshes can be used as textured surfaces. The presence of the wires of the meshes can be considered as textured surfaces while the presence of the holes can increase the air fraction, which is an important parameter of the Cassie−Baxter equation. However, the liquids should not penetrate inside the holes, except for applications in the separation of different liquids. To obtain superoleophobic meshes, it is necessary to roughen the wires.40−48 Several groups reported the elaboration of “underwater” super-

INTRODUCTION Due to their extremely high liquid repellency even for extremely low surface tension liquids, superoleophobic surfaces or super-oil-repellent surfaces are studied due to the extremely high expectation for their potential applications in oil transportation,1,2 microfluidic devices,3,4 cargo carriers on water and oil,5 antifouling coatings,6 antifingerprint glasses and windows,7,8 printing technologies,9 or antisoil fabric.10,11 However, such surfaces are very difficult to design due to the ability of low surface tension liquids to spread on most of the surfaces. Indeed, two equations are very often used to predict the possibility to obtain super-liquid-repellent properties on rough or porous surfaces: the Wenzel12 and the Cassie− Baxter13 equations. When a liquid is in the Wenzel state,12 it fully wets the surface leading to full contact between the surface and the liquid. The surface roughness can increase or decrease the contact angle (θ) of the corresponding smooth surfaces (Young’s angle, θY). In the case of oils, because θY is usually below 90°, the surface roughness induces a decrease in θ. However, the Cassie−Baxter equation13 can predict the possibility to obtain superoleophobic properties. Indeed, in the Cassie−Baxter state, the presence of an air fraction trapped between the surface and the liquid can induce a high increase in θ. If the surface roughness is important in the Wenzel equation; this is not the case of the Cassie−Baxter one for which the capacity of surface to trap air is very important. Very recently, an example of a superoleophobic surface in Nature has been reported .14,15 It has been demonstrated that soil-dwelling wingless arthropods and more precisely pringtails of the genus Orthonychiurus stachianus and Tetrodontophora bilanensis), are able to remain clean in their dirty environment as well as to form robust superoleophobic plastron that protects them from suffocation on immersion in oils. These capacities are due to the presence on their surfaces of very well-defined © 2014 American Chemical Society

Received: October 28, 2013 Revised: December 24, 2013 Published: January 8, 2014 2052

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oleophobic and superhydrophilic meshes, especially for oil/ water separation, by coating with TiO2 nanoparticles, ZnO nanorods, zeolite, polyacrylamide hydrogel, or poly(diallyldimethylammonium perfluorooctanoate).42−48 However, the wettability of these meshes changed from superoleophobic to oleophilic or superoleophilic when the media is air. Tuteja et al. obtained superoleophobic surfaces with ultralow hysteresis and sliding angles by coating with fluorinated polyhedral oligomeric silsequioxane (POSS).40 These exceptional properties showed the interest to use meshes for superoleophobic properties. However, because the meshes have a complex geometry, it is preferable to find other strategies to induce the growth of a coating from the substrate. The electrodeposition of conducting polymers is one of these methods. It can be used to induce the growth of structured polymers from the substrate. Conducting polymers can be substituted with fluorinated or hydrocarbon chains to produce in one step superoleophobic or superhydrophobic properties.41−60 This very versatile process allows the tuning of the surface morphology by adjusting the structure of the monomer and electrochemical parameters. The surface roughness can also be controlled with the deposition charge. To produce superoleophobic properties on smooth surfaces, the best way was found to be the use of fluorinated 3,4-ethylenedioxypyrrole as monomer because they often lead to microstructured/ nanoporous or microstructured/nanostructured surfaces.59,60 Because long fluorinated tails are known to have environmental consequences,61,62 the elaboration of superoleophobic surfaces using short fluorinated tails, especially perfluorobutyl (C4F9), is a difficult but a very interesting challenge. Indeed, the replacing of long fluorinated tails into short ones very often leads to much lower surface properties, especially oleophobicity. Indeed, the intrinsic hydro- and oleophobicity of the perfluorobutyl chains are much lower, for example, than that of perfluorooctyl chains, due to low interactions between them, as shown by Honda et al.63,64 Recently, it was demonstrated that the presence of a long alkyl spacer and amide connector can reduce the mobility of perfluorobutyl chains and lead to superoleophobic properties.65−67 Here, we report the possibility to reach superoleophobic properties but with an important adhesion by electropolymerization of the monomer represented in Scheme 1 and

Article

EXPERIMENTAL SECTION

Electrodeposition. Stainless steel meshes of different openings were purchased from Fisher Scientific: 800, 400, 200, 100, 50, and 25 μm. Stainless steel “smooth” substrates were also used as a reference substrate (0 μm). The monomer (EDOP-C11-NH-F4) used for the deposition was synthesized in nine steps using a procedure given in the literature.68,69 The stainless steel meshes were ultrasonically cleaned with ethanol and dried. Because the nature of the substrate can affect the polymer growth,70 a thin polypyrrole film was first electrodeposited on the meshes. For that, an aqueous solution of 0.25 M of pyrrole and 0.08 M of oxalic acid was introduced in an electrochemical cell. The cell was connected to an Autolab potentiostat of Metrohm using a three-electrode system. The stainless steel mesh was used as working electrode, a platinum plate as counter electrode, and a saturated calomel electrode (SCE) as reference electrode. After degassing under argon, polypyrrole films were electrodeposited at constant potential (E = 0.77 V vs SCE) and with use of a deposition charge (Qs) of 5 mC·cm−2. This process allows the deposition of a smooth and adherent layer of polypyrrole around the mesh wires. After washing and drying, the solution was replaced by an anhydrous acetonitrile solution containing 0.10 M of tetrabutylammonium bis(trifluoromethane)sulfonimide (Bu4TMSF) and 0.01 M of EDOP-C11-NH-F4. Polymer films were electrodeposited at constant potential (E = 0.80 V vs SCE) and with use of Qs between 12.5 and 225 mC·cm−2. The monomer oxidation potential was the same than that on gold plates, which confirms one of the interests of the deposition of the polypyrrole film. Surface Characterization. The contact angle measurements were performed using probe liquids of various surface tensions: water (72.8 mN/m), ethylene glycol (47.3 mN/m), sunflower oil (31 mN/m), hexadecane (27.6 mN/m), dodecane (25.3 mN/m), decane (23.8 mN/m), octane (21.6 mN/m), and hexane (18.4 mN/m). The static contact angles were determined with the sessile-drop method using 2 μL droplets. The dynamic contact angles were obtained by the tilted-drop method, by surface inclination after deposition of a 6 μL droplet. The SEM images were recorded using a 6700F microscope of JEOL after surface metallization to obtain high quality images at very high magnification.

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Scheme 1. Monomer Used for the Electrodeposition on Stainless Steel Meshes

RESULTS AND DISCUSSION Surface Wettability. The best results were obtained for Qs = 225 mC·cm−2. At this deposition charge, Figure 1 shows the influence of the mesh opening and the surface tension of the probe liquid on the static contact angles. The highest oleophobic properties were obtained with an opening of 100 μm. With this opening, θsunflower oil of 150° and θhexadecane of 136° were obtained. Otherwise, we observed an increase of the surface oleophobicity as the opening decreases of the opening from 800 to 100 μm and a decrease after from 100 to 25 μm. As a consequence, the opening mesh is highly important in the control of the oil-repellent properties. The dynamic contact angle measurements revealed that the oils remained stuck on the surface. Otherwise, we observed an increase of the surface oleophobicity as the opening decreases. Hence, the intrinsic oleophobicity of the polymer and the presence of both the texture of the mesh and the polymer structures allowed exceptional apparent contact angles to be reached but were not sufficient for low sliding angles to be

containing a short perfluorobutyl tail, an undecyl spacer, and an amide connector, on stainless steel meshes. The surfaces have been characterized by static and dynamic contact angle measurements and scanning electron microscopy (SEM). The influence of the mesh opening, the surface tension of the liquid probe, and the deposition charge on the surface oleophobicity is also discussed. 2053

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Figure 1. Influence of the mesh opening and the surface tension of the liquid probe (γLV) on the contact angles. Qs = 225 mC·cm−2.

Figure 2. Influence of the deposition charge (Qs) and the surface tension of the liquid probe (γLV) on the contact angles. Mesh opening = 100 μm.

obtained, which means there was a sufficient penetration of the oils inside the roughness or the holes, impeding self-cleaning properties. Nevertheless, these results are exceptional for coatings with polymer containing C4F9 chains. The influence of the deposition charge, which is related to the amount of polymer, on the contact angles obtained with an opening of 100 μm is represented in Figure 2. The influence is not linear, and a deposition charge of 225 mC·cm−2 was necessary to reach the best oleophobic properties. To understand these results, it was necessary to examine the surfaces by SEM. Surface Morphology. At a nanoscale, the SEM analyses revealed that, at 225 mC·cm−2, the polymer was micro- and nanostructured (Figure 3), as observed on smooth surfaces, which is very important for reaching exceptional oleophobic properties.68,69 At a microscale, the polymer growth was very

important and the polymer can form bridges inside the holes of the meshes if the opening is not very important (≤100 μm), as shown in Figure 4. For example, in the case of the opening at 25 μm, most of the holes were covered by the polymer, which induced a decrease of the surface oleophobicity. Hence, it is important to keep the polymer around the holes to avoid covering the holes. SEM images were also recorded as a function of the deposition charge, for an opening of 100 μm (Figure 5). These images show that the mesh becomes extremely rough for a deposition charge of 225 mC·cm−2 showing the importance of structuring the mesh to obtain the highest oleophobic properties. As a consequence, to obtain the best oleophobic properties, it is necessary to render the mesh highly rough while having relatively large holes in order to have the highest amount of air trapped below the droplet and favor the Cassie− Baxter state. However, the holes should not be too large to disrupt the interface.

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DISCUSSION These results can be explained with the Wenzel and Cassie− Baxter equations.12,13 When the oil droplet is in the Wenzel state,12 the oil fully wets the surface. The equation is cos θ = r cos θY with r representing the roughness factor and θY the contact angle of the corresponding smooth surface (Young’s angle). Because the θY of the oils is lower than 90° for the polymer, in the Wenzel state the oil fully penetrates the mesh as shown in Figure 6a. Indeed, only the Cassie−Baxter equation can predict the possibility to attain superoleophobic meshes. In the Cassie−Baxter state,13 the oil is similar to being in

Figure 3. SEM image of PEDOP-C11-NH-F4 on stainless steel mesh at two high magnifications: (a) ×2500 and (b) ×25000. The inset represents a sunflower oil droplet; Qs = 225 mC·cm−2. 2054

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Figure 4. SEM image of PEDOP-C11-NH-F4 on stainless steel mesh at two high magnifications: (a) ×2500 and (b) ×25000. The inset represents a sunflower oil droplet; Qs = 225 mC·cm−2.

Figure 5. SEM image of PEDOP-C11-NH-F4 on stainless steel mesh (opening, 100 μm) at different deposition charges: (a) 12.5, (b) 25, (c) 50, (d) 100, and (e) 225 mC·cm−2.

Cassie−Baxter state is stable only if its Gibbs energy is lower than that of the Wenzel state, which is not the case here because the contact angle of the oils in the Cassie−Baxter state is higher than that in the Wenzel state. Moreover, the presence on an oil droplet induces on the mesh a pressure, which is highly dependent on the oil surface tension. As described in the literature,24−26,40,71,72 this pressure can be calculated with this equation: P = 2γLV/lcap. For this equation, lcap = (γLV/ρg)1/2 with ρ being the density and g the acceleration due to gravity. The maximum pressure that the mesh can support is called the breakthrough pressure (Pbreakthrough).24−26,40,45,46 This pressure is highly dependent on the mesh characteristics (for example the mesh opening and the diameter of the mesh wires), and the following equation can be used: P = −pγLV(cos θadv)/A with θadv being the advancing contact angle, p the perimeter of the pores, and A the area of the pores.73 Pbreakthrough can also increase with the presence of micro- and/or nanostructures around the meshes but can decrease if the polymer covers the holes of the mesh. The oil is suspended on the mesh (Cassie−

Figure 6. Model used to highlight the possibility to attain superoleophobic on micro-/nanostructured meshes: (a) in the Wenzel state, oil-penetrated mesh; (b) superoleophobic properties obtained with Cassie−Baxter equation.

suspension on the surface thanks to the presence of air between the droplet and the surface (Figure 6b). Marmur showed that, in the case of a multiscale roughness, the Cassie−Baxter equation can be written cos θ = rf f cos θY − (1 − f) with f and (1 − f) being the solid and air fractions, respectively, and rf the roughness ratio of the wet area.17−19 An oil droplet on a superoleophobic mesh is more precisely in a metastable Cassie−Baxter state, as described by Marmur.19 Indeed, the 2055

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(9) Law, K.-Y.; Zhao, H. Enhancing Superoleophobicity and Reducing Adhesion through Multi-Scale Roughness by Means of ALD/CVD Techniques in Inkjet Printing Applications. Ger. Offen. DE 102012208190 A1, Nov. 22, 2012. (10) Wang, H.; Xue, Y.; Ding, J.; Feng, L.; Wang, X.; Lin, T. Durable, Self-Healing Superhydrophobic and Superoleophobic Surfaces from Fluorinated-Decyl Polyhedral Oligomeric Silsesquioxane and Hydrolyzed Fluorinated Alkyl Silane. Angew. Chem., Int. Ed. 2011, 50, 11433−11436. (11) Artus, G. R. J.; Zimmermann, J.; Reifler, F. A.; Brewer, S. A.; Seeger, S. A Superoleophobic Textile Repellent Towards Impacting Drops of Alkanes. Appl. Surf. Sci. 2012, 258, 3835−3840. (12) Wenzel, R. N. Resistance of Solid Surfaces to Wetting by Water. Ind. Eng. Chem. 1936, 28, 988−994. (13) Cassie, A. B. D.; Baxter, S. Wettability of Porous Surfaces. Trans. Faraday Soc. 1944, 40, 546−551. (14) Hensel, R.; Helbig, R.; Aland, S.; Braun, H.-G.; Voigt, A.; Neinhuis, C.; Werner, C. Wetting Resistance at Its Topographical Limit: The Benefit of Mushroom and Serif T Structures. Langmuir 2013, 29, 1100−1112. (15) Helbig, R.; Nickerl, J.; Neinhuis, C.; Werner, C. Smart Skin Patterns Protect Springtails. PLoS One 2011, 6, e25105. (16) Tsujii, K.; Yamamoto, T.; Onda, T.; Shibuichi, S. Super OilRepellent Surfaces. Angew. Chem., Int. Ed. 1997, 36, 1011−1012. (17) Marmur, A. From Hygrophilic to Superhygrophobic: Theoretical Conditions for Making High-Contact-Angle Surfaces from LowContact-Angle Materials. Langmuir 2008, 24, 7573−7579. (18) Marmur, A. Wetting on Hydrophobic Rough Surfaces: To be Heterogeneous or not to be? Langmuir 2003, 19, 8343−8348. (19) Marmur, A. Superhydrophobic and Superhygrophobic Surfaces: from Understanding Non-Wettability to Design Considerations. Soft Matter 2013, 9, 7900−7904. (20) Extrand, C. W. Model for Contact Angles and Hysteresis on Rough and Ultraphobic Surfaces. Langmuir 2002, 18, 7991−7999. (21) Extrand, C. W. Designing for Optimum Liquid Repellency. Langmuir 2006, 22, 1711−1714. (22) Joly, L.; Biben, T. Wetting and Friction on Superoleophobic Surfaces. Soft Matter 2009, 5, 2549−2557. (23) Biben, T.; Joly, L. Wetting on Nanorough Surfaces. Phys. Rev. Lett. 2008, 100, 186103/1−186103/4. (24) Tuteja, A.; Choi, W.; Ma, M.; Mabry, J. M.; Mazzella, S. A.; Rutledge, G. C.; McKinley, G. H.; Cohen, R. E. Designing Superoleophobic Surfaces. Science 2007, 318, 1618−1622. (25) Choi, W.; Tuteja, A.; Mabry, J. M.; Cohen, R. E.; McKinley, G. H. A Modified Cassie−Baxter Relationship to Explain Contact Angle Hysteresis and Anisotropy on Non-Wetting Textured Surfaces. J. Colloid Interface Sci. 2009, 339, 208−216. (26) Choi, W.; Tuteja, A.; Chhatre, S.; Mabry, J. M.; Cohen, R. E.; McKinley, G. H. Fabrics with Tunable Oleophobicity. Adv. Mater. 2009, 21, 2190−2195. (27) Im, M.; Im, H.; Lee, J.-H.; Yoon, J.−B.; Choi, Y.-K. A Robust Superhydrophobic and Superoleophobic Surface with InverseTrapezoidal Microstructures on a Large Transparent Flexible Substrate. Soft Matter 2010, 6, 1401−1404. (28) Zhao, H.; Law, K.-Y.; Sambhy, V. Fabrication, Surface Properties, and Origin of Superoleophobicity for a Model Textured Surface. Langmuir 2011, 27, 5927−5935. (29) Ahuja, A.; Taylor, J. A.; Lifton, V.; Sidorenko, A. A.; Salamon, T. R.; Lobaton, E. J.; Kolodner, P.; Krupenkin, T. N. Nanonails: A Simple Geometrical Approach to Electrically Tunable Superlyophobic Surfaces. Langmuir 2008, 24, 9−14. (30) Wu, T.; Suzuki, Y. Design, Microfabrication and Evaluation of Robust High-Performance Superlyophobic Surfaces. Sens. Actuators, B 2011, 156, 401−409. (31) Dufour, R.; Harnois, M.; Coffinier, Y.; Thomy, V.; Boukherroub, R.; Senez, V. Engineering Sticky Superomniphobic Surfaces on Transparent and Flexible PDMS Substrate. Langmuir 2010, 26, 17242−17247.

Baxter state) if the pressure induced by the droplet is below the maximum pressure that the mesh can support. In our case a mesh opening of 100 μm induced the highest increase in oleophobicity, and to obtain the best oleophobic properties, it is necessary to render the mesh highly rough while having relatively large holes in order to have the highest amount of air trapped below the droplet and favor the Cassie−Baxter state.

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CONCLUSION Superoleophobic surfaces (θsunflower oil = 150° and θhexadecane = 136°) with high adhesion were elaborated by electrodeposition of conducting polymer containing short perfluorobutyl (C4F9) chains on stainless steel meshes. Such properties were obtained by highly roughening the mesh by applying a high deposition charge (Qs = 225 mC·cm−2) in order to electrodeposit polymer micro- and nanostructures. The influence of the mesh opening was extremely important, and the best results were obtained with a mesh opening of 100 μm. These results are exceptional for polymers containing C4F9 chains and allow one to envisage new strategies to design fluorinated materials with low bioaccumulative potential.

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AUTHOR INFORMATION

Corresponding Author

*E-mail: [email protected]. Notes

The authors declare no competing financial interest.

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ACKNOWLEDGMENTS We thank Jean-Pierre Laugier of the Centre Commun de Microscopie Appliquée (CCMA, Université Nice Sophia Antipolis) for the realization of the SEM images.

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REFERENCES

(1) Yao, X.; Gao, J.; Song, Y.; Jiang, L. Superoleophobic Surfaces with Controllable Oil Adhesion and Their Application in Oil Transportation. Adv. Funct. Mater. 2011, 21, 4270−4276. (2) Ding, C.; Zhu, Y.; Liu, M.; Feng, L.; Wan, M.; Jiang, L. PANI Nanowire Film with Underwater Superoleophobicity and PotentialModulated Tunable Adhesion for no Loss Oil Droplet Transport. Soft Matter 2012, 8, 9064−9068. (3) Wu, D.; Wu, S.-z.; Chen, Q.-D.; Zhao, S.; Zhang, H.; Jiao, J.; Piersol, J. A.; Wang, J.-N.; Sun, H.-B.; Jiang, L. Facile Creation of Hierarchical PDMS Microstructures with Extreme Underwater Superoleophobicity for Anti-Oil Application in Microfluidic Channels. Lab Chip 2011, 11, 3873−3879. (4) Almeida, R.; Kwon, J. W. Virtual Walls Based on Oil-Repellent Surfaces for Low-Surface-Tension Liquids. Langmuir 2013, 29, 994− 998. (5) Jin, H.; Kettunen, M.; Laiho, A.; Pynnoenen, H.; Paltakari, J.; Marmur, A.; Ikkala, O.; Ras, R. H. A. Superhydrophobic and Superoleophobic Nanocellulose Aerogel Membranes as Bioinspired Cargo Carriers on Water and Oil. Langmuir 2011, 27, 1930−1934. (6) Zhang, J.; Pu, G.; Severtson, S. J. Fabrication of Zinc Oxide/ Polydimethylsiloxane Composite Surfaces Demonstrating Oil-FoulingResistant Superhydrophobicity. ACS Appl. Mater. Interfaces 2010, 2, 2880−2883. (7) Jin, S.; Choi, C. Superhydrophobic and Superoleophobic Nanosurfaces used as Antifingerprint Touch Sensitive Screen. PCT Int. Appl. WO 2012088209 A2, Jun. 28, 2012. (8) Huang, C.-D.; Weng, W.-H.; Hwang, W.-J. Anti-Fingerprint Coating Construction Containing Hydrophobic Nanocomposite, Oleophobic Nanocomposite or Superamphiphobic Nanocomposite. U.S. Pat. Appl. Publ. US 20060110537 A1, May 25, 2006. 2056

dx.doi.org/10.1021/jp410639j | J. Phys. Chem. C 2014, 118, 2052−2057

The Journal of Physical Chemistry C

Article

(32) Bormashenko, E. Why does the Cassie−Baxter Equation Apply? Colloids Surf., A 2008, 324, 47−50. (33) Whyman, G.; Bormashenko, E. How to Make the Cassie Wetting State Stable? Langmuir 2011, 27, 8171−8176. (34) Nosonovsky, M. Multiscale Roughness and Stability of Superhydrophobic Biomimetic Interfaces. Langmuir 2007, 23, 3157− 3161. (35) Bico, J.; Thiele, U.; Quere, D. Wetting of Textured Surfaces. Colloids Surf., A 2002, 206, 41−46. (36) Liu, J.-L.; Feng, X.-Q.; Wang, G.; Yu, S.-W. Mechanisms of Superhydrophobicity on Hydrophilic Substrates. J. Phys.: Condens. Matter 2007, 19, 356002/1−356002/12. (37) He, Y.; Jiang, C.; Yin, H.; Yuan, W. Tailoring the Wettability of Patterned Silicon Surfaces with Dual-Scale Pillars: From Hydrophilicity to Superhydrophobicity. Appl. Surf. Sci. 2011, 257, 7689− 7692. (38) Cao, L.; Hu, H.-H.; Gao, D. Design and Fabrication of Microtextures for Inducing a Super-Hydrophobic Behavior on Hydrophilic Materials. Langmuir 2007, 23, 4310−4314. (39) Cao, L.; Price, T. P.; Weiss, M.; Gao, D. Super Water- and OilRepellent Surfaces on Intrinsically Hydrophilic and Oleophilic Porous Silicon Films. Langmuir 2008, 24, 1640−1643. (40) Kota, A. K.; Li, Y.; Mabry, J. M.; Tuteja, A. Hierarchically Structured Superoleophobic Surfaces with Ultralow Contact Angle Hysteresis. Adv. Mater. 2012, 24, 5838−5843. (41) Pan, S.; Kota, A. K.; Mabry, J. M.; Tuteja, A. Superomniphobic Surfaces for Effective Chemical Shielding. J. Am. Chem. Soc. 2013, 135, 578−581. (42) Zhang, F.; Zhang, W. B.; Shi, Z.; Wang, D.; Jin, J.; Jiang, L. Nanowire-Haired Inorganic Membranes with Superhydrophilicity and Underwater Ultralow Adhesive Superoleophobicity for High-Efficiency Oil/Water Separation. Adv. Mater. 2013, 25, 4192−4198. (43) Xue, Z.; Wang, S.; Lin, L.; Chen, L.; Liu, M.; Feng, L.; Jiang, L. A Novel Superhydrophilic and Underwater Superoleophobic Hydrogel-Coated Mesh for Oil/Water Separation. Adv. Mater. 2011, 23, 4270−4273. (44) Wen, Q.; Di, J.; Jiang, L.; Yu, J.; Xu, R. Zeolite-Coated Mesh Film for Efficient Oil−Water Separation. Chem. Sci. 2013, 4, 591−595. (45) Sawai, Y.; Nishimoto, S.; Kameshima, Y.; Fujii, E.; Miyake, M. Photoinduced Underwater Superoleophobicity of TiO2 Thin Films. Langmuir 2013, 29, 6784−6789. (46) Tian, D.; Zhang, X.; Tian, Y.; Wu, Y.; Wang, X.; Zhai, J.; Jiang, L. Photo-induced Water−Oil Separation based on Switchable Superhydrophobicity−Superhydrophilicity and Underwater Superoleophobicity of the Aligned ZnO Nanorod Array-coated Mesh Films. J. Mater. Chem. 2012, 22, 19652−16657. (47) Yang, J.; Zhang, Z.; Xu, X.; Zhu, X.; Men, X.; Zhou, X. Superhydrophilic−superoleophobic coatings. J. Mater. Chem. 2012, 22, 2834−2837. (48) Zhang, L.; Zhong, Y.; Cha, D.; Wang, P. A Self-Cleaning Underwater Superoleophobic Mesh for Oil-Water Separation. Sci. Rep. 2013, 3, 2326. (49) Darmanin, T.; Guittard, F. Wettability of Conducting Polymers: From Superhydrophilicity to Superoleophobicity. Prog. Polym. Sci., http://dx.doi.org/doi:10.1016/j.progpolymsci.2013.10.003. (50) Darmanin, T.; Taffin de Givenchy, E.; Amigoni, S.; Guittard, F. Superhydrophobic Surfaces by Electrochemical Processes. Adv. Mater. 2013, 25, 1378−1394. (51) Darmanin, T.; Guittard, F. Superhydrophobic Fiber Mats by Electrodeposition of Fluorinated Poly(3,4-ethyleneoxythiathiophene). J. Am. Chem. Soc. 2011, 133, 15627−15634. (52) Yan, H.; Kurogi, K.; Mayama, H.; Tsujii, K. Environmentally Stable Super Water-Repellent Poly(alkylpyrrole) Films. Angew. Chem., Int. Ed. 2005, 44, 3453−3456. (53) Kurogi, K.; Yan, H.; Mayama, H.; Tsujii, K. Super WaterRepellent Poly(alkylpyrrole) Films having Environmental Stability. J. Colloid Interface Sci. 2007, 312, 156−163.

(54) Darmanin, T.; Guittard, F. Highly Hydrophobic Films with Various Adhesion by Electrodeposition of Poly(3,4-bis(alkoxy)thiophene)s. Soft Matter 2013, 9, 1500−1505. (55) Taleb, S.; Darmanin, T.; Guittard, F. Superhydrophobic Conducting Polymers with Switchable Water and Oil Repellency by Voltage and Ion Exchange. RSC Adv. 2014, 4, 3550−3555. (56) Conte, P.; Darmanin, T.; Guittard, F. Spider-Web-like Fiber toward Highly Oleophobic Fluorinated Materials with Low Bioaccumulative Potential. React. Funct. Polym. 2014, 74, 46−51. (57) Luo, S.-C.; Sekine, J.; Zhu, B.; Zhao, H.; Nakao, A.; Yu, H.-h Polydioxythiophene Nanodots, Nonowires, Nano-Networks, and Tubular Structures: The Effect of Functional Groups and Temperature in Template-Free Electropolymerization. ACS Nano 2012, 6, 3018− 3026. (58) Luo, S.-C.; Liour, S. S.; Yu, H.-h. Perfluoro-Functionalized PEDOT Films with Controlled Morphology as Superhydrophobic Coatings and Biointerfaces with Enhanced Cell Adhesion. Chem. Commun. 2010, 46, 4731−4733. (59) Darmanin, T.; Guittard, F. Molecular Design of Conductive Polymers to Modulate Superoleophobic Properties. J. Am. Chem. Soc. 2009, 131, 7928−7933. (60) Bellanger, H.; Darmanin, T.; Taffin de Givenchy, E.; Guittard, F. Influence of the Intrinsic Oleophobicity and the Surface Structuration on the Superoleophobic Properties of PEDOP Films bearing Two Fluorinated Tails. J. Mater. Chem. A 2013, 1, 2896−2903. (61) Conder, J. M.; Hoke, R. A.; de Wolf, W.; Russell, M. H.; Buck, R. C. Are PFCAs Bioaccumulative? A Critical Review and Comparison with Regulatory Criteria and Persistent Lipophilic Compounds. Environ. Sci. Technol. 2008, 42, 995−1003. (62) Giesy, J. P.; Kannan, K. Global Distribution of Perfluorooctane Sulfonate in Wildlife. Environ. Sci. Technol. 2011, 35, 1339−1342. (63) Honda, K.; Morita, M.; Otsuka, H.; Takahara, A. Molecular Aggregation Structure and Surface Properties of Poly(fluoroalkyl acrylate) Thin Films. Macromolecules 2005, 38, 5699−5705. (64) Honda, K.; Morita, M.; Sakata, O.; Sasaki, S.; Takahara, A. Effect of Surface Molecular Aggregation State and Surface Molecular Motion on Wetting Behavior of Water on Poly(fluoroalkyl methacrylate) Thin Films. Macromolecules 2010, 43, 454−460. (65) Bellanger, H.; Darmanin, T.; Taffin de Givenchy, E.; Guittard, F. Influence of Long Alkyl Spacers in the Elaboration of Superoleophobic Surfaces with Short Fluorinated Chains. RSC Adv. 2013, 3, 5556− 5562. (66) Darmanin, T.; Guittard, F. Superoleophobic Surfaces with Short Fluorinated Chains? Soft Matter 2013, 9, 5982−5990. (67) Darmanin, T.; Guittard, F. Tunable Surface Nanoporosity by Electropolymerization of N-alkyl-3,4-ethylenedioxypyrroles with Different Alkyl Chain Lengths. Macromol. Chem. Phys. 2012, 213, 2492− 2497. (68) Darmanin, T.; Guittard, F. Highly Oleophobic Properties of PEDOP Polymers with Short Perfluorobutyl Chains Separated by Long Alkyl Spacers and Amido Connectors. Macromol. Chem. Phys. 2013, 214, 2036−2042. (69) Darmanin, T.; Guittard, F. Superoleophobic Polymers with Metal Ion Affinity toward Materials with both Oleophobic and Hydrophilic Properties. J. Colloid Interface Sci. 2013, 408, 101−106. (70) Darmanin, T.; Guittard, F. Super Oil-Repellent Surfaces from Conductive Polymers. J. Mater. Chem. 2009, 19, 7130−7136. (71) Lafuma, A.; Quéré, D. Superhydrophobic States. Nat. Mater. 2003, 2, 457−460. (72) Journet, C.; Moulinet, S.; Ybert, C.; Purcell, S. T.; Bocquet, L. Contact Angle Measurements on Superhydrophobic Carbon Nanotube Forests: Effect of Fluid Pressure. Europhys. Lett. 2005, 71, 104− 109. (73) Youngblood, J. P.; McCarthy, T. J. Ultrahydrophobic Polymer Surfaces Prepared by Simultaneous Ablation of Polypropylene and Sputtering of Poly(tetrafluoroethylene) Using Radio Frequency Plasma. Macromolecules 1999, 32, 6800−6806.

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dx.doi.org/10.1021/jp410639j | J. Phys. Chem. C 2014, 118, 2052−2057