Crossover Flory model for phase separation in polymer solutions

The Flory theory for phase separation in polymer solutions has been modifie d to incorporate critical fluctuations. The fluctuations change the shape o f the coexistence curve near the critical demixing point and shift the crit ical temperature. Asymptotically close to the critical point Ising-like cri tical behavior is revealed, whereas classical (mean-field) Flory behavior i s recovered far away from the critical region. The effects of fluctuations strongly depend on the degree of polymerization and disappear at the theta point in the infinite chain-length limit. The dependence of the effective c ritical exponents and critical amplitudes on the degree of polymerization i n the crossover Flory model has been analyzed. (C) 1999 Elsevier Science B. V. All rights reserved.