New fluorine-free low surface energy surfactants and surfaces

Modification and control of surface properties, such as surface tension γ at air-liquid (AL) interfaces and surface energy at solid-liquid (SL) surfaces, are at the heart of colloid and interface science. Certain applications require low or very low surface tensions γAL and surface energies γSL, for example and not limited to: microemulsification, aqueous foams for fire-fighting, hydrophobic, superhydrophobic and oleophobic surfaces to control spreading and wetting of aqueous and oily liquids on solids. In many cases low surface tensions/energies can only be obtained by employing perfluoroalkyl substances (PFAS) as surfactant or polymer additives or surface treatments. Although fluorocarbons and polymers have been employed for over 80 years, with many industrial and commercial benefits, it is now recognized that PFAS are very hazardous to the environment and health. Hence, in the coming years it will be necessary to phase out PFAS entirely, however, at present, there are very few viable alternatives available. This article outlines the chemical principles for designing F-free low surface energy (LSE) additives, and also covers the most recent advances in the quest for non-fluorinated surfactants and polymeric surface coatings.

A bioinspired strategy for poly(3,4-ethylenedioxypyrrole) films with strong water adhesion

Using a bioinspired approach, we prepare poly(3,4-ethylenedioxypyrrole) (PEDOP) films with parahydrophobic properties, characterized by high apparent water contact angle and strong water adhesion. The films are made by electropolymerization and the influence of substitution by an alkyl chain of various length (from C4H9 to C14H29) on the 3,4-ethylenedioxy-bridge is reported. More precisely, the best properties are obtained from a length of C12H25 due to the formation of spherical nanoparticles.

Dynamic Wetting Properties of Mesh Substrates with Tunable Water Adhesion

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.