Temperature dependent impedance spectroscopy and Thermally Stimulated Depolarization Current (TSDC) analysis of disperse red 1-co-poly(methyl methacrylate) copolymers

Abstract

The dielectric relaxation processes of polymethyl methacrylates that have been functionalized with Disperse Red 1 (DR1) in the side chain (DR1-co-MMA) were studied with temperature dependent impedance spectroscopy and thermally stimulated depolarization current (TSDC) techniques. Copolymers with dipole contents which varied between 10 mol% and 70 mol% were prepared. All samples showed dipole relaxations above the structural-glass transition temperature (T g ). The β-relaxation of the methyl methacrylate (MMA) repeating unit was most visible in DR1(10%)-co-MMA and rapidly vanishes with higher dipole contents. DSC data reveal an increase of the T g by 20 °C to 125°C with the inclusion of the dipole into the polymethyl methacrylate (PMMA) as side chain. The impedance data of samples with several DR1 concentrations, taken at several temperatures above T g , have been fitted with the Havriliak-Negami (HN) function. In all cases, the fits reveal a dielectric response that corresponds to power-law dipolar relaxations. TSDC measurements show that the copolymer can be poled, and that the induced polarization can be frozen by lowering the temperature well below the glass transition. Relaxation strengths Δε estimated by integrating the depolarization current are similar to those obtained from the impedance data, confirming the efficient freezing of the dipoles in the structuralglass state.

Thermal Sampling and Compensation Phenomena of PVVH/ZnO Nanocomposite Polymer Using TSDC Technique

“…One of the most useful and very high sensitive techniques which used to study the dielectric relaxation of materials is thermal stimulated depolarization current TSDC technique. TSDC was used to study and quantify the defects (trap charges, dipoles or oxygen vacancies) which exist in the dielectric materials [2], the accumulations of charges in polycrystalline [3], also to evaluate the influence of dipole content on the relaxation strength and the thermal stability of the system [4]. Generally, TSDC technique is a dielectric technique in which the dynamic of the system is observed through the trend of the previously aligned structural dipoles to orientate at random as the mobility of the system increase during the continuous heating from temperatures far below T g [5].…”