RESUMEN

In nature, wetting phenomena are present nearly everywhere and are a source of inspiration for liquid transportation. A good understanding of the underlying dynamic phenomena that governs wettability is therefore extremely important for researchers involved in bio-inspired surfaces. Herein, we study the adhesive behavior with water of mesh substrates modified with structured copolymers in order to tune the surfaces from parahydrophobic states (high water adhesion) to superhydrophobic states (low water adhesion). Using the ejection test method (ETM), a new technique that consists of the ejection of water droplets deposited onto a substrate with the aid of a catapult system, we experimentally demonstrate that the elasticity of the mesh substrate can be exploited for efficient vertical actuation of droplets.

RESUMEN

We study the wetting and the adhesive behavior of substrates made by electropolymerization of copolymers of pyrene substituted with fluoroalkyl and adamantyl groups. The hydrophobicity and water adhesion properties can be tuned by the molar percentage (mol %) of each pyrene monomer so that the substrate properties can vary from superhydrophobic to parahydrophobic, with respectively low and high water adhesion. The ejection test method (ETM) is proposed as an original tool to discriminate and characterize such substrates. Using a catapult-like apparatus, a droplet initially at rest on the surface is subject to a large acceleration and is subsequently ejected. Depending on the surface properties and initial catapult acceleration, the ejection is more or less efficient and occurs with or without fragmentation of the droplet. The ETM is shown to be a complementary test to the lateral adhesion and hysteresis classical measurements. This work is of importance for the understanding of adhesion phenomena on various surfaces and for a better quantitative characterization of their adhesive properties.

RESUMEN

A smart stimuli-responsive surface was fabricated by the electro-copolymerization of pyrene monomers followed by base and acid treatment. Copolymers of pyrenes bearing fluorinated chains (Py-nF6 ) and acid functions (Py-COOH) were produced with different molar concentrations of each monomer (0, 25, 50, 75, and 100 % of Py-nF6 vs. Py-COOH) by an electrochemical process. Two different perfluorinated pyrenes containing ester and amide groups were used to reach superhydrophobic properties. The relation of those bonds with the final properties of the surface was explored. The pH-sensitive group of Py-COOH allowed the surfaces to be reversibly switched from superhydrophobic (water contact angle>θw >150° and very low hysteresis) to hydrophilic (θw <90°). The amide and ester bonds influenced the recovery of the original wettability after both base and acid treatment. Although the fluorinated homopolymer with ester bonds was insensitive to base and acid treatment due to its superhydrophobic properties with ultralow water adhesion, the recovery of the original wettability for the copolymers was much more important with amide bonds due to the amide functional groups be more resistant to the hydrolysis reaction. This strategy offered the opportunity to access superhydrophobic films with switchable wettability by simple pH treatment. The films proved to be a good tool for use in biological applications, for example, as a bacterial-resistant film if superhydrophobic and as a bacterial-adherent film if hydrophilic.

Asunto(s)

Polímeros/química , Pirenos/química , Halogenación , Concentración de Iones de Hidrógeno , Interacciones Hidrofóbicas e Hidrofílicas , Propiedades de Superficie , Humectabilidad

RESUMEN

The formation of porous nanostructures by using a templateless electropolymerization process with thieno[3,2-b]thiophene as a monomer and two different deposition methods (galvanostatic and pulse potentiostatic deposition) has been studied. The wettability, roughness, and morphology of the surfaces are reported. The surfaces prepared by galvanostatic deposition show hydrophilic behavior (θw ≈80°) that is highly dependent on the roughness. Nanoseeds were formed in the first instances followed by the formation of large microcapsules and hollow spheres. Indeed, as the deposition time and current density increase, the size and amount of structures also increase. By pulse deposition, the surfaces are hydrophobic (θw ≈100°) and only show a roughness dependence if the mean surface roughness is >1.5 µm. The surfaces are formed from nanodomes and nanospheres, but they are less structured than that of surfaces produced by the galvanostatic method. The formation of these structures is directly related to the amount of gas released from trace water in situ during electropolymerization, which is highly dependent on the electrochemical method chosen. The formation of new seeds is highly favored by the galvanostatic method, whereas their growth is favored by the pulse deposition method. This is the first study on the use of galvanostatic and pulse deposition methods, with potential applications in surface chemistry. Thieno[3,2-b]thiophene proved to be very versatile to form different structures with potential applications as water harvesting and separation membranes.

RESUMEN

Here, we report for the first time the possibility to obtain not only arrays of nanotubes but also tree-like structures with high water adhesion using a one-step and templateless electropolymerization process. Using thienothiophene derivatives, particularly thieno[2,3-b]thiophene (Thienothiophene-1) and thieno[3,2-b]thiophene (Thienothiophene-2), we demonstrate this surface fabrication in organic solvent (dichloromethane) and without any surfactants. The formation of nanotubes is due to the stabilization by the polymer of gas bubbles produced in situ during electropolymerization process, and we show that the water content plays an important role in the formation of gas bubbles even if it is not the unique parameter. Using cyclic voltammetry as an electropolymerization method, the amount of released gas is more significant, but at constant potential it is much easier to control the nanotube formation. It is also possible to obtain arrays of tree-like structures when electropolymerizing with high deposition charges, and the resulting surfaces have high θw with extremely high water adhesion even if the polymers are intrinsically hydrophilic (θ(Y)w ≈ 70°). This work is extremely important for potential applications in water transportation and harvesting, oil/water separation membranes, energy systems, and biosensing.

RESUMEN

Materials with bioinspired superhydrophobic properties are highly desirable for many potential applications. Here, nine novel monomers derived from indole are synthesized to obtain these properties by electropolymerization. These monomers differ by the length (C4F9, C6F13 and C8F17) and the position (4-, 5- and 6-position of indole) of the perfluorinated substituent. Polymeric films were obtained with C4F9 and C6F13 chains and differences in the surface morphology depend especially on the substituent position. The polyindoles exhibited hydrophobic and superhydrophobic properties even with a very low roughness. The best results are obtained with PIndole-6-F 6 for which superhydrophobic and highly oleophobic properties are obtained due to the presence of spherical nanoparticles and low surface energy compounds.