Ultrathin Cross-Linked Perfluoropolyether Film Coatings from Liquid CO₂ and Subsequent UV Curing

Solvent-Free Synthesis of a Superamphiphobic Surface by Green Chemistry

“…Poly­(perfluorooctyl acrylate) polymers were synthesized in sc-CO 2 by a free radical polymerization method in 1992 as an alternative to the conventional polymerizations which were performed in organic solvents . In the past decade, many other polymerization studies were reported where sc-CO 2 was used as the solvent medium. − It is known that the fluorinated polymers having long side chains containing −CF 2 – and −CF 3 groups are almost insoluble in many organic solvents. , Thus, the use of sc-CO 2 or liquid-CO 2 is a good alternative to coat highly fluorinated polymers on various substrates. ,,,− …”

“…Consequently, three different methods were developed to obtain uniform films on substrates: the first one is the “rapid expansion supercritical solution” (RESS) method, ,− the second one is the polymer deposition from a sc-CO 2 solution, ,,, and the last one is the “free meniscus coating” (FMC) method. ,,− ,− In the RESS method, a mixture of the soluble polymer and a supercritical fluid is expanded through a nozzle to form a coating with a spray process on a surface, and it is possible to prepare rough coatings by spraying some nano- or microparticles that were already dispersed in the same solution. ,, Mawson et al investigated the coating properties of submicrometer fibers and particles by using poly­(1,1,2,2-tetrahydro­perfluorodecyl acrylate, poly-TA-N) homopolymer as a function of the RESS process parameter such as the L / D ratio (length to diameter of expansion nozzle), nozzle type, solution concentration, and pre-expansion temperature . Many other researchers prepared superhydrophobic or highly hydrophobic surfaces by using the RESS method. − For example, a hydrophobic surface was prepared with a water contact angle of 113° by rapid expansion of the poly­(trifluoroethyl methacrylate) dissolved in sc-CO 2 mixture onto a thermoplastic starch/poly­(butylene adipate- co -terephthalate) substrate .…”

“…On the other hand, Carbonell and co-workers obtained ultrathin, flat, and uniform coatings by applying a novel method entitled FMC. ,− ,− This method is a special dip-coating process which is performed by using a suitable polymer which is dissolved in the liquid-CO 2 . The coating on the substrate can be formed by draining the polymer solution in a closed system under pressure or alternatively by pulling the substrate by a mechanical system from the polymer solution at a determined speed. ,, Kim et al reported that perfluoropolymers such as poly­[2-(perfluoro­octyl)­ethyl acrylate] − and perfluoro­polyether and also sucrose octaacetate (SOA) films were successfully coated on silicon wafer substrates by applying the FMC method, and the thickness and morphology of the coatings can be controlled by adjusting the withdrawal velocity, the solution concentration, and the evaporation rate. ,− It was found that increasing the polymer concentration and evaporation-driving force (Δ P ) resulted in the increase of the film thickness with a decrease in the surface uniformity.…”

Nanoheterogeneous networks by photopolymerization of perfluoropolyethers and acrylic co-monomers

“…They have high thermal and chemical resistance, low refractive index, low friction and very low surface tension. Applications are described in several previous works …”

Perfluoropolyether polymers by UV curing: design, synthesis and characterization

“…By changing the chemical structures of the polymers, in particular the ratio between the hydrogen and fluorine contents as will be shown in this work, it is possible to match a target refractive index. The introduction of different UV‐curable end‐groups and the tuning of the functionality make possible the control of the crosslinking density of the cured material, enabling for example the manufacturing of Bragg gratings with a high thermo‐optic coefficient (d n /d T ) 18. Also, in micro‐ and nano‐patterning, PFPE acrylates are successfully employed as an alternative to epoxy and silicone matrices 19.…”