The preparation of fluorinated and water-soluble materials via heterogeneous polymerizations in carbon dioxide.

摘要

The use of carbon dioxide (CO₂) as a polymerization medium offers numerous advantages over processes where organic solvents are employed. However, most hydrocarbon polymers have low solubility in CO₂ which necessitates the need for novel CO₂ amphiphiles. Atom transfer radical polymerization (ATRP) has been used in the synthesis of such materials. This process was performed using CO₂ as the reaction medium. The best results were achieved when a fluorinated ligand was applied to the system. Diblock and triblock copolymers were made incorporating fluorocarbon segments with either poly(dimethylaminoethyl methacrylate) (PDMAEMA) or poly(methyl methacrylate) (PMMA). The MMA ATRP dispersion process was also examined and resulted in the formation of spherical colloidal particles with controlled molecular weights and narrow polydispersities.; Hydrophilic colloidal particles have also been made by several heterogeneous polymerizations in CO₂. The dispersion polymerization of 1-vinyl-2-pyrrolidone (VP) in the presence of poly(1,1-dihydroperfluorooctyl acrylate) stabilizer resulted in the formation of nearly monodisperse spherical particles. This system was investigated as the stabilizer and VP concentration was varied and as the CO₂ pressure and reaction time changed. Temperature-sensitive colloidal particles based on poly(N-isopropyl acrylamide) (PNIPAAM) and poly(N-ethyl acrylamide) (PNEAM) were also prepared. These particles were produced by three different methods that include precipitation, dispersion, and suspension polymerizations in CO₂. The particles range in size from 0.17 μm to slightly under 1 mm. Fluorocarbon polymers containing segments of PDMAEMA or a monomeric sugar moiety were used as stabilizers in these systems.