Crystallization of poly(ethylene oxide) in binary blends containing poly(p-vinyl phenol)

Abstract Blends of poly(ethylene oxide) (PEO) with an amorphous polymer, poly( p -vinyl phenol) (PVPh), showed a single, composition-dependent, glass transition temperature as a consequence of the miscibility between components. X-ray diffraction and differential scanning calorimetry (d.s.c.) results indicated a strong reduction of blend crystallinity with increasing PVPh content. Observation of melting point depression allowed the determination of the interaction energy density, B , between the two polymers in the melt. To obtain equilibrium melting point data, the Hoffman—Weeks procedure was employed to take into account the influence of crystal morphology. The values of B obtained by d.s.c. and by thermal optical microscopy were −7.1 and −8.8 cal cm −3 , respectively. Analysis of the isothermal crystallization by means of the Avrami equation led to average values of the Avrami index of 2.5 for both pure PEO and a PEO/PVPh 90/10 blend, and 3.1 for the remaining compositions analysed. The temperature and composition dependence of the growth rates were analysed using an expression incorporating both the diffusion mechanism and the nucleation tendency. A discontinuity in the temperature coefficient of the growth rate curve was found for PEO/PVPh blends with 90 and 80 wt% PEO. The experimental results indicate that the rate of crystallization, the degree of crystallinity and the equilibrium melting temperature are strongly dependent on the composition of the blends.