Lower critical solution temperature of linear PNIPA obtained from a Yukawapotential of polymer chains

The lower critical solution temperature (LCST) behavior of a linear poly(N- isopropylacrylamide) (PNIPA) in water is thought to result from the polymer -polymer attractive interaction. This polymer-polymer attraction is modeled by a temperature-dependent Yukawa attractive potential, with Yukawa parame ters determined by fitting the theoretical phase diagram for a pure Yukawa fluid to the experimental lower consolute boundary for a PNIPA-water soluti on. The predicted coexistence curve for the PNIPA-water mixtures in the tem perature-polymer volume fraction plane is reasonably close to the experimen tal cloud point data for the PNIPA-water system. (C) 2000 John Wiley & Sons , Inc.