Melt polycondensation of 2,5-tetrahydrofurandimethanol with various dicarboxylic acids towards a variety of biobased polyesters

Abstract

This study investigated the effects of the molecular structure of 2,5-tetrahydrofurandimethanol (THFDM) on its reactivity and polyester properties. 2,5-Furandicarboxylic acid (FDCA) was employed as a representative diacid; by investigating the esterification process and the Gibbs free energy of the polyester molecular chain, the effects of THFDM's molecular structure on its reactivity and molecular chain energy were clarified. The order of reactivity of different diols was as follows:1,4-butanediol > diethylene glycol > 1,8-octanediol > 1,4-cyclohexanedimethanol > 2,5-tetrahydrofurandimethanol > ethylene glycol. The Gibbs free energy of the polyester chain with different structures was calculated, and it proved that the energy was generally lower when THFDM was in the trans configuration. DEG-based polyesters and THFDM-based polyesters were prepared by reacting diethylene glycol (DEG) and THFDM with different types of dibasic acids (1,4-succinic acid, 1,6-hexanedioic acid, and terephthalic acid and FDCA, respectively). The influence of the molecular structure of the diols on polyester properties was investigated. Two series of homopolyesters exhibited an amorphous state at room temperature. The existence of a cyclic structure significantly improved the glass transition temperature (T_g), thermal decomposition temperature, and strength of polyesters. In terms of THFDM-based polyesters, both poly(tetrahydrofurandimethylene terephthalate) (PTT) and poly(tetrahydrofuran dimethylene furandicarboxylate) (PTF) exhibited high values of T_g (69.6 °C and 76.8 °C, respectively), which provides a prospect for application as novel biobased plastics.