Novel Fluorinated Block Copolymer Stabilizers for Dispersion Polymerization of Cross-Linked Poly(2-ethylhexyl methacrylate-stat-chloromethylstyrene) in Fluorinated Solvents

Block, random and palm-tree amphiphilic fluorinated copolymers: controlled synthesis, surface activity and use as dispersion polymerization stabilizers

The architecture of novel fluorinated copolymers drastically influences their stabilizing properties and their ability to template particle formation.

Hydrolysis of p-nitrophenyl esters promoted by semifluorinated quaternary ammonium polymer latexes and films

Semifluorinated polymer latexes were prepared by emulsion polymerization of 2.5-25% of a fluoroalkyl methacrylate, 25% chloromethylstyrene, 1% styrylmethyl(trimethyl)ammonium chloride, and the remainder 2-ethylhexyl methacrylate under surfactant-free conditions. The chloromethylstyrene units were converted to quaternary ammonium ions with trimethylamine. In aqueous dispersions at particle concentrations of less than 1 mg mL(-1) the quaternary ammonium ion latexes promoted hydrolyses of p-nitrophenyl hexanoate (PNPH) in pH 9.4 borate buffer and of diethyl p-nitrophenyl phosphate (Paraoxon) in 0.1 M NaOH at 30 °C with half-lives of less than 10 min. Thin 0.7-2 μm films of the latexes on glass promoted fast hydrolysis of Paraoxon but not of PNPH under the same conditions. Even after annealing the quaternary ammonium ion polymer films at temperatures well above their glass transition temperatures, AFM images of the film surfaces had textures of particles. Contact angle measurements of the annealed films against water and against hexadecane showed that the surfaces were not highly fluorinated.

Fluorinated colloidal emulsion of photochangeable rheological behavior as a sacrificial agent to fabricate organic, three-dimensional microstructures

Three-dimensional organic microfabrication, an emerging technology, faces the challenge of lacking a sacrificial agent (SA) to temporarily support the formation of microscale geometries, which can be removed after a microstructure is constructed. In this study, an ultradense oil-in-organofluorine colloidal emulsion with photopolymerizable submicrometer droplets (diameter approximately 500 nm) was prepared and used as the required SA. Upon exposure to light, the colloidal emulsion undergoes a significant rheological change, which hardens the emulsion and presents the molding/protecting function that an SA must have. Importantly, the emulsion includes a synthesized fluorophilic/fluorophobic block copolymer surfactant to stabilize the droplet compartments, facilitating the dissolution of the postexposure SA. Two successfully built, complex, organic 3D microstructures show the effectiveness of using this novel SA material.

Hydrolysis of p-nitrophenyl esters in mixtures of water and a fluorous solvent

Hydrolyses of p-nitrophenyl hexanoate (PNPH) and diethyl p-nitrophenyl phosphate (Paraoxon) were carried out in mixtures of basic aqueous solutions and HFE-7200 (an isomeric mixture of perfluorobutyl and perfluoroisobutyl ethyl ether). Hexadecyltrimethylammonium bromide (CTAB), a perfluoroalklpylpyridinium chloride surfactant, tetrabutylammonium salts, and colloidal particles of cross-linked copolymers of 2-ethylhexyl methacrylate and styrylmethyl(trimethyl)ammonium chloride dispersed in either the aqueous phase or the HFE phase were used to promote the reactions. In a pH 9.4 borate buffer, the surfactants and the aqueous colloidal particles were the most active for PNPH hydrolysis, the PNPH preferred the HFE phase, and the rates depended both on mass transfer of the PNPH from HFE to water and on the intrinsic rate of hydrolysis in the aqueous phase. In 0.10 M NaOH, CTAB and the aqueous colloidal particles were the most active for Paraoxon hydrolysis, Paraoxon preferred the aqueous phase, and the rates followed pseudo-first-order kinetics.