Enthalpy and Volume Relaxation of Core-Crosslinked Star Polystyrene/Poly(methyl methacrylate) Blends

摘要

Blends of linear and core-crosslinked star (CCS) polymers are prepared. The relaxation and thermal properties of the blends are determined using conventional and modulated-temperature DSC and modulated-temperature thermomechanometry. Addition of CCS polymers increase the glass transition temperature while decreasing the enthalpy and the linear coefficient of thermal expansion, suggesting that the hyperbranched polymers restrict matrix chain motions. Isothermal annealing increased the T_g and ΔH and decreased sub-T_g due to the reduced free volume and mobility within the polymer films. Volume relaxation during annealing is observed using mT-TM, while a stretched-exponential function is utilised to interpret the data.