Influence of Alkyl Chain Length and Branching on the Plasticizing Properties of 2,5-Thiophenedicarboxylate Plasticizers in PVC

A series of bio-based 2,5-thiophenedicarboxylates were successfully synthesized, and their chemical structures were characterized using Fourier transform infrared spectroscopy (FTIR) and nuclear magnetic resonance (NMR). The influence of alkyl chain length and branching on the plasticizing properties of 2,5-thiophenedicarboxylates in poly(vinyl chloride) (PVC) was evaluated through dynamic mechanical analysis (DMA), hardness measurements, and tensile testing. It was found that the plasticizing efficiency of 2,5-thiophenedicarboxylates decreased as the alkyl chain length increased, as reflected by the gradual increase in glass transition temperature ( T g ), hardness, and elastic modulus. Additionally, among 2,5-thiophenedicarboxylate isomers with the same molecular weight, those with branched alkyl chains exhibited superior plasticizing efficiency compared to those with linear alkyl chains. The above results suggested that optimizing alkyl chain length and branching could further improve the plasticizing efficiency of 2,5-thiophenedicarboxylate plasticizers in PVC. Notably, 2,5-thiophenedicarboxylates showed greater polarity and improved migration resistance in non-polar solvents than commercial dioctyl phthalate (DOP), suggesting their potential application in PVC products exposed to non-polar environments.