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Novel statistic copolymers of dialkyl vinylphosphonates have been synthesizedvia rare earth metal-mediated group transfer polymerization using easily accessible tris(cyclopentadienyl) ytterbium. The copolymerization parameters have been determined by activity measurements showing the formation of almost perfectly random copolymers (r₁, r₂ ~ 1). Thus, the polymerization rate of vinylphosphonate GTP is mainly limited by the steric demand of growing polymer chain end. The obtained copolymers of diethyl vinylphosphonate and dimethyl- or di-n-propyl vinylphosphonate show thermoresponsive properties, i.e. exhibit atuneable lower critical solution temperature following a coil-globule transition mechanism, with cloud points between5 and 92 °C. Hereby, the LCST can be precisely adjusted by varying the comonomer composition and correlates linearly with the content of hydrophilic/hydrophobic comonomer. These thermoresponsive poly(vinylphosphonate)s, exhibiting a sharp and reversible phase transition, and minor environmental effects such as concentration and additives on their cloud point, are promising candidates in biomedical applications.

http://pubs.acs.org/doi/abs/10.1021/ma3019014