Macromolecular surfactants for supercritical carbon dioxide applications: Synthesis and characterization of fluorinated block copolymers prepared by nitroxide mediated radical polymerization

Poly(perfluorooctyl-ethylenoxymethylstyrene) (PFDS) and poly(1,1,2,2-tetrahydroperfluorodecyl acrylate) (PFDA) homopolymers as well as poly(styrene)-b-poly(perfluorooctyl-ethylenoxymethylstyrene) (PS-b-PFDS) and poly(styrene)-b-poly(1,1,2,2-tetrahydroperfluorodecyl acrylate) acrylate) (PS-b-PFDA) block copolymers of various chain lengths were synthesized by nitroxide-mediated radical polymerization in the presence of either 2,2,6,6-tetramethyl-1-piperidinyloxy free radical (TEMPO) in the case of FDS monomer or N-tert-butyl-N-(1-diethylphosphono-2,2-dimethylpropyl)-N-oxyl (DEPN) in the case of the FDA monomer. The molar composition of the block copolymers was determined by elemental analysis and proton NMR while the blocky structure was checked by SEC analysis in trifluorotoluene. Block copolymers PS-b-PFDS (3.6K/60K) and PS-b-PFDA (3.7K/43K) were soluble in neat CO2 at moderate pressure and temperature, indicating the formation of micelles. Similar block copolymers with a longer PS block such as PS-b-PFDA (9.5K/49K), corresponding to a lower CO2-philic/CO2-phobic balance, were insoluble in neat CO2 but could be solubilized in the presence of styrene as a cosolvent. Additionally, surface and bulk properties of PS-b-PFDA were investigated, indicating the same surface tension as for the PFDA homopolymer (gamma(LV) = 10.3 mN/m) and a bulk nanostructured morphology. (C) 2004 Wiley Periodicals, Inc.