Purification impact on structural relaxation phenomena in biopolyesters from tomato peel agro-wastes

Abstract

This study investigates the effects of cross-linking on the microstructure and relaxation dynamics of biopolyesters synthesized from monomers presenting different degrees of purification. These biopolyesters, derived from hydroxy fatty acids extracted from plant cuticles, are gaining interest as sustainable alternatives to synthetic polymers. Their structural organization and molecular mobility, which are influenced by the cross-linking density, play a crucial role in determining their physical properties. A combination of differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA) and broadband dielectric spectroscopy (BDS) analysis is used for evaluating their thermal, mechanical and dielectric properties. Special attention is paid to the relationship between cross-linking, segmental relaxation and charge transport mechanisms. The results show that purification influences the degree of cross-linking, leading to significant differences in crystallinity, molecular mobility, and mechanical properties. The more purified the monomers, the lower the cross-link density, resulting in a transition from thermoplastic polymer to elastomeric behavior. DSC and DMA confirm that higher purification promotes crystallization. In addition, conductivity measurements indicate charge carrier blocking and interfacial polarization effects in the crystalline samples. Relaxation processes provide information about thermal events from melting and beyond. This study contributes to a deeper understanding of relaxation phenomena and the structure–property relationships of these biopolyesters. The results offer new perspectives for tuning the functionalities of biopolyesters through controlled purification and cross-linking.