Synthesis, life cycle assessment, and polymerization of a vanillin-based spirocyclic diol toward polyesters with increased glass transition temperature

Bio-based rigid diols are key building blocks in the development and preparation of high performance bioplastics with improved thermal and dimensional stability. Here, we report on the straightforward two-step synthesis of a diol with a spirocyclic acetal structure, starting from bio-based vanillin and pentaerythritol. According to a preliminary life cycle assessment (LCA), the greenhouse gas emissions of this bio-based diol are significantly lower than that of bio-based 1,3-propanediol. Copolymerization of the rigid spiro-diol with 1,6-hexanediol and dimethyl terephthalate by melt polymerization yielded a series of copolyesters, which showed improved glass transition temperature and thermal stability upon the incorporation of the spiro-acetal units. The crystallinity and melting point of copolyesters decreased with increasing content of the spirocyclic backbone structures. The copolyesters containing 10% of the new diol was semicrystalline while those with 20 and 30% spiro-diol incorporated were completely amorphous. Moreover, dynamic mechanical analysis indicated that the copolyesters showed comparable storage moduli as AkestraTM, a commercial fossil-based high-performance polyester.