Microstructure of melt-miscible, semicrystalline polymer blends

A combination of small-angle X-ray scattering and optical microscopy was used to investigate the influence of diluent mobility and polymer-polymer interactions on diluent segregation in a series of "model" melt-miscible poly(ethylene oxide) (PEO) blends. The amorphous polymeric diluents were selected with regard to their glass transition temperatures relative to the crystallization temperature and the strength of their interactions with PEO. Segregation of the weakly interacting amorphous polymers was found to be largely dependent on their glass transition temperatures: the high-T _g diluent was found to reside exclusively in interlamellar regions whereas the low-T _g diluent was excluded at least partially into interfibrillar regions. The introduction of strong intermolecular interactions between the crystallizable and amorphous components resulted in significantly reduced crystal growth rates and promoted diluent segregation over greater length scales, regardless of diluent mobility at the crystallization temperature. Thus, for the systems under consideration here, the study shows that although diluent mobility contributes to diluent segregation, the growth of the PEO crystals, and the factors that influence the growth rate, dominate the length scale of diluent segregation.