Dielectric relaxation dynamics in (methyl methacrylate)/(4-tert-butylstyrene) random co-polymers

Random co-polymer systems based on (methyl methacrylate) and (4-tert-butylstyrene) at various monomer-to-monomer ratios (MMA-to-TBS) were developed by means of thermal initiated random co-polymerization. To elucidate the characteristics and dynamics of the observed relaxations, we employed Broadband Dielectric Spectroscopy (BDS), a powerful tool to investigate dipolar relaxation and charge transport processes. PMMA exhibits three dielectric relaxation processes, namely the α-, β-, and γ-relaxation, from high to low temperatures respectively, whilst PTBS only exhibits an α-relaxation. In both cases, the α-relaxation refers to the segmental process, also known as the dynamic glass transition process and relates to the T_g of the system, which is the major thermal event of amorphous polymers. The secondary relaxations originating from the MMA monomer are also of great interest in order to discern how the local environment affects the physical behavior of polymers.

Broadband Dielectric Spectroscopy measurements were conducted employing a Phecos temperature system with an integrated dielectric cell, and an Alpha-A frequency analyzer, all provided by Novocontrol Technologies, Germany. The dielectric experiments were performed in a parallel ‘sandwich’ plate configuration employing gold electrodes, in the temperature and frequency ranges of -48 – 198 ^oC and 10^-1 – 10⁶ Hz, respectively.