Preparation of new membranes by complex formation of itaconic acid acrylamide copolymer with polyvinylpyrrolidone: studies on gelation mechanism by light scattering

Mechanism of membrane formation by dipping a 10 wt% aqueous homogeneous pol ymer solution of poly(itaconic acid-co-acrylamide) (75:25 molar ratio)/poly vinylpyrrolidone (50/50) into acid solution was investigated by time-resolv ed light scattering and the pH effect of the acid solution to gelation mech anism during membrane formation was discussed. In the pH range 1.58-1.25, t he gelation was governed by phase separation mechanism via the spinodal dec omposition and then a membrane with regular pore size was obtained. The pha se separation was caused by polymer-polymer complex formation between polym ers. From an analysis based on Cahn's linearized theory of the spinodal dec omposition, the apparent diffusion coefficient D-app Of phase separation wa s smaller for lower pH. Because, at low pH there exists a lot of complex wh ich dramatically reduces the chain mobility. The average pore size of membr ane also depends on pH. When the pH was lower than 1.25, the liquid-liquid phase separation did not occur but the solution gelled homogeneously and a wrinkle-like morphology without pore was observed. FTIR analysis of the dri ed membranes showed that the complex formation had occurred by hydrogen bon ding between the component polymers and its extent increased linearly with decreasing pH. (C) 1999 Elsevier Science B.V. All rights reserved.