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

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 T _g s. To a first approximation, growth rates for PEO and the blends can be "superposed" when normalized by the degree of supercooling and T - T _g . In addition, at higher T _c and diluent concentrations, particularly for blends with strongly interacting diluents, the growth rate slows from G ∝ t ⁰ to G ∝ t ^-1/2 , consistent with a crossover to diffusion-controlled growth. Analysis of PEO growth rates using the LHM model yields σ _e ∼ 40 ergs/cm ² for crystallization in regime II. For the blends, the mobility as a function of T _c 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) T _g .