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. Copyright © 2003 Society of Chemical Industry