Thermoresponsive behavior of sodium alginate grafted with poly(N-isopropylacrylamide) in aqueous media

Thermoresponsive graft copolymers were synthesized. Thermally induced properties were introduced by grafting poly (N-isopropylacrylamide) (PNIPAM) side chains onto a sodium alginate backbone. The resulting graft copolymers cover a broad range in PNIPAM composition and molecular weight. Remarkable thermothickening behavior in water and 0.1 M NaCl is observed by viscometry when the temperature, concentration, weight ratio of PNIPAM side chains to backbone, and PNIPAM molecular weight are higher than certain critical values. This behavior is reversible and could have applications in oil rigs and drug delivery systems.