Crossover Flory model for phase separation in polymer solutions

The Flory theory for phase separation in polymer solutions has been modified to incorporate critical fluctuations. The fluctuations change the shape of the coexistence curve near the critical demixing point and shift the critical temperature. Asymptotically close to the critical point Ising-like critical behavior is revealed, whereas classical (mean-field) Flory behavior is 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 critical exponents and critical amplitudes on the degree of polymerization in the crossover Flory model has been analyzed.