Crystallization of Poly(ethylene oxide) and Melt-Miscible PEO Blends

Abstract

Spherulitic growth rates for poly(ethylene oxide) and four model, melt-miscible blends were measured over a range of crystallization temperatures. The miscible diluents fall into two classes: those exhibiting relatively weak intermolecular interactions with PEO and those exhibiting strong interactions. Generally, at a given crystallization temperature, growth rates for blends with the strongly interacting polymers are considerably lower than those with weakly interacting polymers with comparable Tgs. To a first approximation, growth rates for PEO and the blends can be “superposed” when normalized by the degree of supercooling and T − Tg. In addition, at higher Tc and diluent concentrations, particularly for blends with strongly interacting diluents, the growth rate slows from G ∝ t0 to G ∝ t-1/2, consistent with a crossover to diffusion-controlled growth. Analysis of PEO growth rates using the LHM model yields σe ∼ 40 ergs/cm2 for crystallization in regime II. For the blends, the mobility as a function of Tc and diluent content was estimated from experimental growth rates and the nucleation constant for neat PEO. These mobilities were found to correlate well with diluent (or blend) Tg.