Ultra-high glass transition temperature FDCA-based copolyesters with BNEF: Synthesis and performance

High glass transition temperature polymers are extensively used in many fields such as packaging, electronic products, and automobiles. However, most of them are expensive as synthesized in polar aprotic solvent with low solid percent. The task of effectively synthesizing high glass transition temperature polymers faces at least three important challenges: the need for a solvent-free process to reduce cost and pollution, the requirement for a thermoplastic process with a high glass transition temperature above 150 °C, and the use of monomers derived from renewable resources. Traditional polyesters can be prepared via melt polycondensation, but achieving a glass transition temperature above 130 °C while maintaining good mechanical properties remains challenging. In this work, we developed a strategy to synthesize a new high glass transition temperature polyesters by employing rigid bulky diol of 9,9-bis [6-(2-hydroxyethoxy)naphthyl]fluorene (BNEF) and bio-based 2,5-furandicarboxylic acid (FDCA) which derived from fructose or furfural, as the main monomers. The new copolyesters exhibit a glass transition temperature of up to 164.2 °C, a number-average molecular weight of 24,600 g/mol, along with tensile modulus and strength values of 3030 MPa and 134 MPa, respectively. Furthermore, the copolyesters exhibit excellent transparency properties of 88.4 % by cutoff at 700 nm and well solvent resistance, which could serve as new low-cost, high-performance engineering plastics with ultra-high glass transition temperature and transparency.