Amphiphilic Cross-Linked Liquid Crystalline Fluoropolymer-Poly(ethylene glycol) Coatings for Application in Challenging Conditions: Comparative Study between Different Liquid Crystalline Comonomers and Polymer Architectures

Linear and hyperbranched poly(ethylene glycol)-cross-linked amphiphilic fluoropolymer networks comprised of different liquid crystalline comonomers were developed and evaluated as functional coatings in extreme weather-challenging conditions. Through variation of the liquid-crystalline comonomer and hydrophilic:hydrophobic component ratios, several series of coatings were synthesized and underwent a variety of analyses including differential scanning calorimetry, water contact angle measurements and solution stability studies in aqueous media. These materials maintained an unprecedented reduction in the free water melting transition (T_m) temperature across the hyperbranched and linear versions. The coatings synthesized from hyperbranched fluoropolymers preserved the liquid crystalline character of the mesogenic components, as seen by polarized optical microscopy, and demonstrated stability in saltwater aqueous environments and in cold weather conditions.

Covalent layer-by-layer assembled superhydrophobic organic-inorganic hybrid films

Using the concept of covalent layer-by-layer assembly (covalent LbL), used until now for the elaboration of films from polymers or dendrimers, we have constructed hybrid organic/inorganic surfaces by alternating different layers of amino-functionalized silica nanoparticles (295 nm diameter) and epoxy-functionalized smaller silica nanoparticles (20 nm diameter). The so-realized macromolecular edifice leads to a hierarchical integration of nanoscale textures. Then hydrophobization of the last layer of amino-functionalized silica particles was carried out by grafting a new designed highly fluorinated aldehyde, creating a monomolecular layer via the formation of an imine function. Five highly fluorinated surfaces were built, and their water-repellent abilities were directly correlated to the surface topologies (i.e., the number of layers of silica nanoparticles and their organization on the glass support). The hydrophobicity increased with the number of layers and stable highly water-repellent surfaces (static contact angle with water of 150+/-3 degrees and a contact angle hysteresis of 12 degrees) were obtained with the alternation of nine layers. This result demonstrates the possibility to construct covalent LbL edifices with functionalized silica nanoparticles of different sizes and open this field for the elaboration of responsive, sensing, and therapeutic surfaces with improved film stability.