Nanofold‐decorated surfaces from the electrodeposition of di‐alkyl‐cyclopentadithiophenes

This work describes the synthesis and subsequent electrodeposition of 4H‐cyclopenta[2,1‐b:3,4‐b′]dithiophene (cyclopentadithiophene) monomers di‐substituted with alkyl chains. Each monomer was electropolymerized in solution to observe their capacity at creating well‐structured, rough surfaces. The length of the alkyl chain substituent has a significant influence on the overall surface morphology and wetting behavior after electropolymerization. In the case of nonsubstituted cyclopentadithiophene monomers or those with short alkyl (methyl and ethyl) substituents, the polymerization proceeds readily, forming rough surfaces that follow the Wenzel regime of wetting. In these cases, the surfaces were decorated with globular agglomerates and woven mat features. The measured surface roughness decreases with alkyl chain length as steric hindrance caused by the alkyl substituents limits electropolymerization. As the alkyl chain substituent increases to propyl chain length and beyond, the increase in steric hindrance is so significant that the surface morphology formed during electrodeposition is primarily due to π‐stacking interactions between very short oligomers formed in solution. With propyl and butyl substituents, nanofold morphology is observed, leading to surfaces with much higher contact angles with water (~132°) that follow the Cassie‐Baxter regime of wetting. This type of surface morphology has only been demonstrated one other time and with the use of fluorinated constituents. This work exposes a mild, fluorine‐free synthetic route to creating nanofold‐decorated surfaces.     

Biomimetic Superhydrophobic/Superoleophilic Highly Fluorinated Graphene Oxide and ZIF‐8 Composites for Oil–Water Separation

Superhydrophobic/superoleophilic composites HFGO@ZIF‐8 have been prepared from highly fluorinated graphene oxide (HFGO) and the nanocrystalline zeolite imidazole framework ZIF‐8. The structure‐directing and coordination‐modulating properties of HFGO allow for the selective nucleation of ZIF‐8 nanoparticles at the graphene surface oxygen functionalities. This results in localized nucleation and size‐controlled ZIF‐8 nanocrystals intercalated in between HFGO layers. The composite microstructure features fluoride groups bonded at the graphene. Self‐assembly of a unique micro‐mesoporous architecture is achieved, where the micropores originate from ZIF‐8 nanocrystals, while the functionalized mesopores arise from randomly organized HFGO layers separated by ZIF‐8 nanopillars. The hybrid material displays an exceptional high water contact angle of 162° and low oil contact angle of 0° and thus reveals very high sorption selectivity, fast kinetics, and good absorbencies for nonpolar/polar organic solvents and oils from water. Accordingly, Sponge@HFGO@ZIF‐8 composites are successfully utilized for oil–water separation.     

Superhydrophilic/superhydrophobic surfaces fabricated by spark‐coating

In this study, the authors researched the preparations of superhydrophilic/superhydrophobic surfaces on commercial cup stock polyethylene coated papers by using sparked aluminum nanoparticles deposited on substrates through a sparking process. In this stage, the surface was porous and showed superhydrophilic properties. The samples were then annealed in air at various temperatures and some transformed to superhydrophobicity. It is well known that a suitable roughness in combination with low surface energy has been required to obtain superhydrophobic surfaces. Therefore, it is believed that during annealing process, when polyethylene is diffused from the substrate through the nanoparticle films and the superhydrophobic characteristics were created. The scanning electron microscope images showed that the film surfaces had a fluffy structure for both the as‐deposited and the annealed samples. However, the atomic force microscopy phase images showed completely different surface properties. Moreover, the X‐ray photoelectron spectroscopy spectra showed different surface chemical compositions. The experimental results revealed that the working temperature to produce superhydrophobic surfaces depended on the sparked film thickness. Furthermore, in order to prove the assumption explained above, glass and poly (methyl methacrylate) were also used as substrates.     

Facile Spray-Coating for Fabrication of Superhydrophobic SiO2/PVDF Nanocomposite Coating on Paper Surface

A facile and low-cost superhydrophobic nanocomposite coating on paper surface was fabricated through one-step simply spraying dispersion, using hydrophobic silica nanoparticles as a filter (SiNPs) and polyvinylidene fluoride (PVDF) as a film-forming material. Hydrophobic SiNPs were fabricated via co-hydropholysis and condensation of TEOS and long-chain alkyl silane based on a simple sol-gel process, and the surface chemical structure of SiNPs was characterized by Fourier transform infrared (FTIR) spectra. The wettability and morphology of the coating surface were measured by contact angle (CA) measurement and scanning electron microscope, respectively. The influence of the mass ratio of hydrophobic SiNPs to PVDF (M(SiNPs:PVDF)) on the superhydrophobicity of paper surface was studied. The results showed that when M(SiNPs:PVDF) was 3:1, the water CA was 156.0 ± 1.0° for the nanocomposite coating with micro/nano-hierarchical structure on paper surface. Further, such superhydrophobic nanocomposite coatings on paper surface showed little adhesive property with water. In addition, the prepared superhydrophobic nanocomposite coating could be applied in other substrates, such as wood, aluminum sheet, stainless steel, polytetrafluoroethylene (PTFE), etc.     

喷涂法制备功能性超疏水复合涂层及其性能研究

以常用工程材料硅树脂BP与St(o)ber法合成的二氧化硅(SiO2)分散液为原料,运用喷涂法(spray-coating)制备出了功能性微/纳粗糙(MNR)结构的超疏水涂层,其接触角可以达到146.5°,滚动角小于1°(测试液滴量为15μL).通过分析喷涂法制备复合涂层所需的条件,得出喷涂液pH＝7.7-8.0时,在...     

Facile one‐step fabrication of highly transparent and flexible superhydrophobic substrate by room‐temperature ion irradiation method

Highly transparent (transparency 96.5%), flexible and antireflective superhydrophobic (water contact angle >150°) surfaces have been fabricated at room temperature by the ion irradiation method. This one‐step fabrication route was fairly easy to carry out without any heat or chemical treatment and can be completed within few seconds. This novel chemical free fabricating strategy could be extended to numerous polymeric substrates to achieve transparent and flexible superhydrophobic structures for their potential applications in diverse fields. (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Bioinspired,Cysteamine‐Catalyzed Co‐Silicification of (1 H, 1 H, 2 H, 2 H‐Perfluorooctyl)triethoxysilane and Tetraethyl Orthosilicate: Formation of Superhydrophobic Surfaces

Bioinspired silicification attracts a great deal of interest because of its physiologically relevant, mild conditions for hydrolysis and condensation of silica precursors, which makes the bioinspired approach superior to the conventional sol–gel process, particularly when dealing with biological entities. However, the morphological control of silica structures with incorporation of functional groups in the bioinspired silicilication has been unexplored. In this work, we co‐silicificated (1 H, 1 H, 2 H, 2 H‐perfluorooctyl)triethoxysilane and tetraethyl orthosilicate to investigate the morphological evolution of fluorinated silica structures in the cetyltrimethylammonium bromide‐mediated, cysteamine‐catalyzed silicification. The generated micrometer‐long worm‐like and spherical silica structures display superhydrophobicity after film formation. Interestingly, the measurement of dynamic water contact angles shows that the morphological difference leads to a different wetting state, either the self‐cleaning or the pinning state of the superhydrophobic surface.     

Electrochemically Tunable Cell Adsorption on a Transparent and Adhesion‐Switchable Superhydrophobic Polythiophene Film

A superhydrophobic polythiophene film (SSPTH) is prepared by double‐layer electrodeposition on an indium tin oxide (ITO) glass electrode. This film shows not only electroresponsive superhydrophobic features, but also high transparency compared with the usual polythiophene film. The water‐droplet adhesion on the SSPTH film can be switched between sliding and pinned states under the applied potential. More intresetingly, the change in water‐droplet adhesion results in a change in cell adsorption on the SSPTH film. The low‐adhesion (dedoped) SSPTH films can prevent Hela cell adhesion, whereas high‐adhesion (doped) SSPTH films can promote Hela cell adsorption. This controllable cell adhesion on a SSPTH film may be developed as a smart biointerface material.

     

Synthesis and properties of new fluorinated ester,thioester, and amide substituted polythiophenes. Towards superhydrophobic surfaces

A series of new fluorinated polythiophenes has been synthesized by oxidative chemical and electrochemical polymerization and by Ullmann coupling. The substitution with the perfluoroalkyl alkyl chain CH₂CH₂C₆F₁₃ on the 3 position of the thiophene ring is performed via an ester, thioester, or amide connector, (CH₂)_m‐C(O)X, m = 0–2, with a view to investigating the role of the linker on the polymerization and on the properties of the corresponding polymers. The bromination of the monomers at the 2 and 5 positions allows the use of Ullmann coupling to form soluble fluorinated oligomers. The electron affinity was determined from cyclic voltammetry and a value of 3.1 eV was found for the ester derivative; such materials represent interesting candidates for use in light‐emitting devices or as an electron accepting material in photodiodes/solar cells. The oxidative polymerizations need the connector to be spaced out from the heterocycle to reduce its withdrawal effect. The ester, thioester, and amide spacer determined to a large extent the efficiency of the oxidative polymerization, and particularly the electropolymerization, as well as the solubility of the polymers formed. All the polymers were analyzed by GPC and by UV–visible and fluorescence spectroscopies. The electrochemical oxidation of the thioester and amide group prevents the formation of electroactive films by electropolymerization. But in the case of the ester group, the electroformed polymer exhibits exceptional stable superhydrophobic and lipophobic properties because of a porous surface and the presence of a fluorinated chain that confers low surface energy. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 4707–4719, 2007     

Smart Wetting Control on Shape Memory Polymer Surfaces

Control of surface wettability is very important, and can be realized by controlling surface chemistry or microstructures. Compared with surface chemistry, smart control of surface microstructure is more difficult. Recently, shape memory polymers (SMPs) have advanced to allow control of the surface microstructure and wettability, and thus, demonstrate excellent controllability and many novel functions. In this Minireview, recent achievements in wetting control on SMP surfaces with general hydrophobic, superhydrophobic, superomniphobic and superslippery properties are presented. Particular attention is paid to superhydrophobic surfaces, which display many novel functions, such as switchable isotropic/anisotropic wetting and reprogrammable gradient wetting. Furthermore, a new strategy that combines responsive molecules with the SMP microstructure is also described; this can be used to realize precise wetting control based on coordinated regulation of both surface microstructure and chemistry.