Crystalline morphology in polymer blends via competition with spinodal decomposition

Abstract

Miscible polymer blends containing one crystallizable component and exhibiting liquid-liquid phase separation at elevated temperatures [lower critical solution temperature (LCST) behavior] offer an excellent possibility of controlling morphology and thus mechanical properties. For instance, if a homogeneous mixture of dissimilar polymers is allowed to undergo a rapid temperature jump from below LCST to above LCST, spinodal decomposition takes place and a highly interconnected two-phase morphology with uniform domain size (so-called modulated structure) develops. By quenching the phase-separated system below the glass transition temperature after an appropriate time of phase separation, one is able to fix this characteristic morphology [1]. By quenching the phase-separated blend below the melting point of the crystallizable component to different supercooling depths, it is possible to control the number of nuclei and thus the spherulite's size, creating more or less ordered structures.