Nucleation in binary polymer blends: A self-consistent field study

We study the structure and thermodynamics of the critical nuclei in metastable binary polymer blends using the self-consistent field method. At the mean-field level, our results are valid throughout the entire metastable region and provide a smooth crossover from the classical capillary-theory predictions near the coexistence curve to the density functional predictions of Cahn and Hilliard ~properly transcribed into expressions involving the parameters of the binary polymer blends! near the spinodal. An estimate of the free energy barrier provides a quantitative criterion ~the Ginzburg criterion! for the validity of the ~mean-field! self-consistent approach. The region where mean-field theory is valid and where there can be a measurable nucleation rate is shown to be poorly described by the existing limiting theories; our predictions are therefore most relevant in this region. We discuss our results in connection with recent experimental observations by Balsara and co-workers. © 2002 American Institute of Physics. @DOI: 10.1063/1.1429956#