Crystallization behavior of poly(ethylene bride) and its blends using time-resolved wide- and small-angle X-ray scattering

Time-resolved synchrotron wide- and small-angle X-ray scattering experiment s were used to investigate the crystallization behavior and microstructure development of poly(ethylene oxide) and several melt-miscible PEO blends. M odel blends Were prepared with both weakly interacting poly(methyl methacry late) and two strongly interacting random copolymers. Average SAXS long per iods and lamellar thicknesses decreased at early crystallization times: by 2-3 nm for PEO and blends containing the low T-g diluent and by similar to 5-9 nm for blends containing higher T-g diluents. The latter appears to ari se in part from additional restrictions placed on the growing lamellae by t he stiff, high T-g amorphous polymeric diluents. The increase in final long period over that of neat PEO was similar to 2-4 nm for the weakly interact ing blends, as opposed to as large as 10 nm for the strongly interacting mi xtures. In the former case, the changes are associated with interlamellar d iluent placement, while in the latter they result primarily from an increas e in lamellar thickness due to reduction in degrees of supercooling. In lin e with previous observations, there was a significant decrease in crystalli zation rates for blends containing strongly interacting diluents. Two Avram i expressions were generally required to fit the WAXD crystallinity-time da ta for PEO and as many as three for the blends. For neat PEG, the behavior is reminiscent of crystallization in mixtures of high and low molecular wei ght PEO fractions.