Molecular dynamics and crystallization kinetics in PSMA14/PCL blends

The effect of blending poly(styrene-co-maleic anhydride) with 14 mol% MA (PSMA14) with poly(epsilon-caprolactone) (PCL) is studied by calorimetry, X-ray diffraction, dielectric techniques, and microscopy. Variations in PCL crystallization, melting temperatures and crystallinity degree were observed. Additionally, the presence of a wide and asymmetric enthalpic step, whose position follows Fox predictions, demonstrates miscibility between the blend components. This is in agreement with the interlamellar location of PSMA14. Thermally stimulated depolarization techniques evidenced two segmental dynamics, with distinct compositional variations due to the local differences in composition perceived by each component as a consequence of chain connectivity. The two effective glass transition temperatures vary with composition, in agreement with the self-concentration model predictions when using the Kuhn's segment length for each component. From isothermal crystallizations a marked depression of the PCL equilibrium melting point (T-m(o)) is observed in the blends together with an increase in the half-crystallization times, tau(1/2), as the content of PSMA14 grows. PCL-rich blends exhibited ring-banded spherulites, with a ring periodicity that increased with crystallization temperature and with PSMA14 content. Preliminary results of the phase separation process are given from samples that were thermally treated under different conditions. (c) 2006 Elsevier Ltd. All rights reserved.