pH- and thermo-responsive properties of poly(N-vinylcaprolactam-co-acrylic acid) copolymers

Copolymers with both pH- and thermo-responsiveness were synthesized by free radical copolymerization of N-vinylcaprolactam with small amounts of acrylic acid. The copolymers have been prepared in various solvents and characterized by gel permeation chromatography, Fourier-transform infrared (FTIR) spectroscopy and titration. The phase separation behaviour of these copolymers was studied in water and buffered solutions at a variety of pH values and temperatures by means of attenuated total reflectance FTIR and cloud-point measurements. The aqueous solutions of the copolymers showed a temperature, pH and molecular weight dependent phase-separation behaviour. (C) 2003 Society of Chemical Industry.