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

Abstract

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 blends͒ near the spinodal. An estimate of the free energy barrier provides a quantitative criterion ͑the Ginzburg criterion͒ for the validity of the ͑mean-field͒ 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.

Bubble nucleation in polymer–CO2 mixtures

“…The density proles of the terminal state are determined by a constrained method proposed in ref. 22. In this method, a particular value of the density of one of the component, say the polymer, is assigned to a particular radial distance R. The value of the density is intermediate between those for the two coexisting phases; a convenient choice is r 2 (R) ¼ (r center …”

Origins of the failure of classical nucleation theory for nanocellular polymer foams

“…Previous authors have worked in grand canonical formalisms and measured the critical radius by determining where computations become unstable [11,19] or by introducing constraints on the morphology [25,26]. Oxtoby pointed out that bubbles are stable in canonical for-malisms where the free energies can be correctly evaluated [7].…”

Псевдоспинодаль При Моделировании Распада Сплава Методом Монте-Карло

“…В [14] подобная линия получена для од-нокомпонентного газа вблизи критической точки; было отмечено, что она лежит ближе к бинодали, чем к теоре-тической спинодали. В [3,15] предсказано существование " псевдоспинодали" в бинарных полимерных смесях, что нашло экспериментальное подтверждение [16] (отметим, однако, что речь идет об одиночных экспериментах). Псевдоспинодаль совпадает со спинодалью среднего поля (mean-field спинодалью) в пределе бесконечной молекулярной массы, что математически эквивалентно переходу к дальнодействующему потенциалу.…”