Switchable and Reversible Superhydrophobic Surfaces: Part Two

In this book chapter, most of the methods used in the literature to prepare switchable and reversible superhydrophobic surfaces are described. Inspired by Nature, it is possible to induce the Cassie-Baxter-Wenzel transition using different external stimuli such as light, temperature, pH, ion exchange, voltage, magnetic field, mechanic stress, plasma, ultrasonication, solvent, gas or guest. Such properties are extremely important for various applications but especially for controllable oil/water separation membranes, oil-absorbing materials, and water harvesting systems

Superhydrophobic surfaces with low and high adhesion made from mixed (hydrocarbon and fluorocarbon) 3,4-propylenedioxythiophene monomers

International audienceThis work concerns new superhydrophobic surfaces, generated by replacing long fluorocarbon chains, which bioaccumulate, with short chains whilst at the same time retaining oleophobic properties. Here, is described the synthesis of novel original 3,4-propylenedioxythiophene derivatives containing both a short fluorocarbon chain (perfluorobutyl) and a hydrocarbon chain of various lengths (ethyl, butyl and hexyl). Superhydrophobic (contact angle water > 150° ) surfaces with good oleophobic properties (60° > contact angle hexadecane > 80° ) have been obtained by electrodeposition using cyclic voltammetry. Surprisingly, the lowest hystereses and sliding angles (Lotus effect) are obtained with the shortest alkyl chains due to the presence of microstructures made of nanofibers on the surfaces, whereas, the longest alkyl chains leads to nanosheets with high adhesion (Petal effect). Such materials are potential candidates for biomedical applications

Structured Biotinylated Poly(3,4-Ethylenedioxypyrrole) Electrodes for Biochemical Applications

The immobilization of biotin on transducer surfaces is a very important step for the fabrication of biosensors for many applications (immunoassay, DNA-hybridization assays, targeted imaging). Biotinylated polypyrroles have been studied and tested but gave rise to problems of polymerization and stability due to the intrinsic properties of pyrrole. As an alternative, biotinylated pyrroles were often used in a copolymerization with pyrrole or with an amphiphilic pyrrole derivative in a copolymerization to reduce the problems due to the pyrrole substitution. To find a new strategy, this paper presents the homopolymerization, instead of the use of a copolymerization, by replacing pyrrole by 3,4-ethylenedioxypyrrole bearing biotinylated substituent. We report the synthesis, characterization and electrochemical properties of two biotinylated 3,4-ethylenedioxypyrroles differing by the length of the alkyl spacer (ethyl or dodecyl) as well as the characterization of the corresponding polymer films. We successfully show, by cyclic voltammetry, that these monomers polymerize perfectly and give relatively stable polymer films. The increase of the alkyl spacer improves the polymerization and increases the polymer stability. For the first time, we also studied the surface morphology of an electrodeposited biotinylated polymer. The electrodeposition of these biotinylated derivatives gave rise to the ability to modulate the surface microstructuration, which consists of microspheres or cauliflower-like microstructures according to the length of the alkyl spacer.JRC.I.4-Nanobioscience

Structuration de surface par voie électrochimique: préparation et applications

The control of the surface wettability of materials is very important for many applications. Since the discovery of the superhydrophobic surfaces in nature, their interest is increasing in the scientific community. On the basis of Wenzel and Cassie-Baxter models, who demonstrated the influence of the roughness and the chemistry of surface on the wettability, many methods were developed to create superhydrophobic surfaces. Among these methods, the electrochemical polymerization has many advantages: obtaining of structured and superhydrophobic films in one-step (no post-treatment), fast and easy method, the surface properties can be tuned by modifying the chemical structure of the monomers or the electrochemical parameters. Thus, the aim of this work was to determine the influence of these parameters on the surface properties and more precisely on the surface wettability and the morphology.We synthesized series of monomers containing various polymerizable heterocycles and hydrophobic groups. The corresponding polymers were deposited by electrochemical polymerization and the surface properties were determined.The study of the monomers showed many monomers containing fluorinated chains give superhydrophobic films. Superhydrophobic and superoleophobic films were obtained from 3,4-ethylenedioxypyrrole (EDOP). These exceptional properties are the result of a surface nanoporosity.Le contrôle de la mouillabilité de surface de matériaux est très important pour de nombreuses applications. Depuis la découverte de la superhydrophobie dans la nature, l’intérêt de ces surfaces superhydrophobes dans la communauté scientifique est grandissant. Sur la base des modèles de Wenzel et Cassie-Baxter, qui ont démontré l’influence de la rugosité et de la chimie de la surface sur la mouillabilité, beaucoup de méthodes ont été mises au point pour élaborer des surfaces superhydrophobes. Parmi ces méthodes, la polymérisation électrochimique présente de nombreux avantages : obtention de films structurés et superhydrophobes en une étape (pas de post-traitement), méthode très rapide et simple à mettre en œuvre, modification des propriétés de surfaces en jouant sur de nombreux paramètres liés à la nature du monomère ou aux conditions électrochimiques. Ainsi, le but de ce travail de thèse a été de déterminer l’impact de ces paramètres sur les propriétés de surface et plus précisément sur la mouillabilité et la morphologie de surface.Nous avons ainsi synthétisé un ensemble de monomères contenant des noyaux polymérisables et segments hydrophobes très variés. Les polymères correspondants ont ensuite été déposés par électropolymérisation et les propriétés de surface des films ont été déterminées.L’étude de ces monomères a montré que beaucoup de monomères contenant des chaînes fluorées peuvent être utilisés pour l’obtention de surfaces superhydrophobes. Des films superhydrophobes et superoléophobes ont été obtenus avec le monomère 3,4-éthylènedioxypyrrole (EDOP). Ces propriétés exceptionnelles sont la conséquence d’une nanoporosité de surface

Highly polar linkers (urea, carbamate, thiocarbamate) for superoleophobic/superhydrophobic or oleophobic/hydrophilic properties

International audienceDue to the much lower surface tension of oils in comparison to water, it is extremely difficult to obtain superoleophobic properties and also both oleophobic and hydrophilic properties. While the obtaining of superoleophobic properties needs extremely complex surface structures such as re-entrant structures to impede the oil wetting, the obtaining of both oleophobic and hydrophilic properties needs the use of both oleophobic materials (fluorinated materials) and hydrophilic materials (charged or polar species). Here, by electropolymerization of original 3,4-ethylenedioxythiophene derivatives containing both fluorinated chains (C8F17, C6F13 or C4F9) and highly polar linkers (thiocarbamate SCONH, carbamate OCONH and urea NHCONH), we report for the first time the possibility to obtain superoleophobic properties and also both oleophobic and hydrophilic properties. More precisely superoleophobic properties are obtained with different fluorinated chain lengths and linkers while the obtaining of both oleophobic and hydrophilic properties is possible only with the most polar urea NHCONH linkers

Superhydrophobic surface properties with various nanofibrous structures by electrodeposition of PEDOT polymers with short fluorinated chains and rigid spacers

International audienceIn the aim to produce superhydrophobic surface properties, the nanofibers are excellent candidates due to the possible control in the water adhesion by the nanofiber characteristics, for example. Here, we report the growth of nanofibers with various assemblies directly on surfaces by electropolymerization. For this purpose, an original 3,4-ethylenediothiophene monomer was synthesized. The monomer contains a short fluorinated chain (C4F9) in order to preserve the nanofiber morphology and a highly rigid methoxybenzothioate spacer for the reduction of the rigidity. In this work, we show that various nanofibrous structures and superhydrophobic properties can be obtained by modifying the electrolyte while the surface roughness can also be controlled by the number of deposition scans. The nanofibrous polymers could be used to control the attachment and growth of cells or bacteria