Phase behaviour of poly(N-vinyl caprolactam) in water

Abstract

The solution behaviour of the system poly(N-vinyl caprolactam)/water has been studied. Experiments and theoretical calculations indicate a typical Flory–Huggins (Type I) demixing behaviour with a lower critical solution temperature (LCST). The critical concentration and LCST shift to lower values with increasing molar mass of the polymer. The phenomenological description of such a system predicts a continuous temperature controlled swelling behaviour of the corresponding network. A comparison with literature data confirms this prediction.A calorimetric study of the crystallisation and melting behaviour of water and the concentration dependence of the glass transition temperature, gives no evidence for the formation of a polymer/solvent complex.