Homogeneous crystallization and local dynamics of poly(ethylene oxide) (PEO) confined to nanoporous alumina

Abstract

The crystallization of poly(ethylene oxide) (PEO) confined in self-ordered nanoporous alumina (AAO) containing aligned and straight cylindrical nanopores was studied as a function of molecular weight, pore size and cooling/heating rate by differential scanning calorimetry and X-ray scattering. Bulk PEO crystallizes via heterogeneous nucleation at defects and impurities whereas PEO confined to AAO crystallizes mainly via homogeneous nucleation. Molecular weight and cooling rate have a pronounced effect on the nucleation process. Dielectric spectroscopy revealed that confining PEO to AAO results in broadening of the distribution of relaxation times associated with the segmental α relaxation process and the secondary β process. Dielectric loss peaks become broader with decreasing pore diameter.