New polyurethanes with specific dielectric behavior through included of 1,3,4-thiadiazole derivative in their structure

Abstract

New polyurethanes, derived from heteroaromatic compound (5-amino-1,3,4-thiadiazole-2-thiol) and conventional urethane prepolymers with the same soft segment amount, were synthesized. A range of crosslinkers with flexible or rigid structures (bis(3-aminopropyl)amine, glycerin, castor oil and, 2,4,6, triaminopyrimidine) were used in order to obtain chemically crosslinked structures. The inclusion of the 5-amino-1,3,4-thiadiazole-2-thiol on the main polyurethane chain were studied by Fourier transform infrared spectroscopy. The synthesized polyurethanes were investigated of the thermal, mechanical and dielectric properties and we found that the heteroaromatic compound gives these polyurethanes improved properties, compared to conventional polyurethanes, such as thermal resistance up to 285 °C, high degree of elastic elongations, good mechanical strength and high modulus values. The relaxation behavior of polyurethanes based on 5-amino-1,3,4-thiadiazole-2-thiol is studied by broadband dielectric spectroscopy in the frequency 1 - 106 Hz and temperature ranges 120 °C to + 100 °C. In the studied temperature field the dielectric loss in the frequency domain exhibits α absorption, followed in increasing order of frequencies by two secondary absorptions β and γ. Heteroaromatic structure exerts constraints on the local movements (relaxation processes) within the resulting polymer matrices. These properties and possible antibacterial activity brought by 5-amino-1,3,4-thiadiazole-2-thiol make these polyurethane materials suitable for biomedical applications and beyond.