Macromolecules, Vol.46, No.16, 6475-6484, 2013
Thermoresponsive (Co)polymers through Postpolymerization Modification of Poly(2-vinyl-4,4-dimethylaziactone)
Poly(2-vinyl-4,4-dimethylazlactone), pVDMA, is emerging as a versatile reactive platform in polymer chemistry. Herein, postpolymerization modification of pVDMA leading to thermoresponsive homo- and copolymers. is investigated. VDMA was polymerized by reversible addition fragmentation chain transfer (RAFT) polymerization. The resulting reactive scaffolds with molecular weights ranging from 3.0 to 12.5 kg/mol were converted with a selection of alcohols and amines of varying polarity into functional poly(2-acrylamido isobtityrate)s and poly(2-acrylamido isobutyramide)s with molecular weights ranging from M-n = 4.2-65.1 kg/mol and low polydispersity indices M-w/M-n < 1.37. Spectra obtained by H-1. NMR and infrared spectroscopic measurements conformed to the expected structures While alcohols and amines producing water-soluble or water insoluble VDMA-derived homopolymers were identified seven homopolymers were found to show a lower critical solution temperature in aqueous solution; those formed by reacting pVDMA with N-ethylamine N-isopropylamine, N,N-dimethylamine, N,N-diediylamine, N,N-diethylaminoediylamine, Jeffamine M-600, and tetrahydrofurfurylamine (THF amine). Cloud points increased with decreasing molecular weight With a cloud point of 31 degrees C, the phase separation of poly(tetrahydrofurfuryl 2-acrylamido isobutyramide) (pTAI) occurred close to body temperature, was highly reproducible, and, above a concentration of 0.5 wt % was largely concentration independent. The transition temperature of pTAI-based copolymers could easily be tuned by reacting pVDMA, with a mixture of THF amine and varying amounts of pentylamine or di(ethylene glycol) methyl ether amine.