On nucleation in miscible polymer blends

Abstract The effects of diffusion of crystallizable polymer to a developing spherulite embryo are treated. Using the classical nucleation theory result for the size of a critical-size embryo and an existing model for the growth of a small pure component sphere in a bicomponent matrix, the time τ d for a critical-size embryo to develop under diffusion control is given. The nucleation rate is lowered inversely proportionally to τ d . The dependence of τ d on crystallization temperature exhibits a minimum. At temperatures above that minimum, τ d for a blend becomes increasingly larger with temperature than the time to form a nucleus in a pure system with similar diffusivity. Below the minimum, τ d decreases with increasing crystallization temperature. Decreasing the activation energy for diffusion causes the minimum to move to higher temperatures.