Effects of blending on the molecular dynamics of highly interacting binary polymer blends of poly(methyl methacrylate) and poly[styrene-co-(maleic anhydride)]

The molecular dynamics and miscibility of highly interacting binary polymer blends of poly(methyl methacrylate) (PMMA) and poly[styrene-co-(maleic anhydride)] random copolymer with 8 wt% maleic anhydride content (SMA) were investigated as a function of composition over a wide range of frequency (10^-2-10⁶ Hz) at different constant temperatures (30-160 °C). Only one common glass relaxation process (α-process) was detected for all measured blends, and its dynamics and broadness were found to be composition dependent. The existence of only one common α-relaxation process located at a temperature range between those of the pure polymer components indicated the miscibility of the two polymer components over the entire range of composition. The miscibility was also confirmed by measuring the glass transition temperatures of the blends, T_g, using differential scanning calorimetry. The composition dependence of T_g of the blends showed a positive deviation from the linear mixing rule and well described by the Gordon-Taylor-Kwei equation. The relaxation spectrum of the blends was resolved into α- and β-relaxation processes using the Havriliake-Negami (HN) equation and ionic conductivity. The dielectric relaxation parameters obtained from HN analysis, such as broadness of relaxation processes, maximum frequency, f_max, and dielectric strength, Δε{lunate} (for the α- and β-relaxation processes), were found to be blend composition dependent. The kinetics of the α-relaxation process of the blends were well described by the Meander model, while an Arrhenius-type equation was used to evaluate the molecular dynamics of the β-relaxation process. Blending of PMMA and SMA was found to have a considerable effect on the kinetics and broadness of the β-relaxation process of PMMA, indicating that the strong interaction and miscibility between the two polymer components could effectively change the local environment of each component in the blend.