Melt polymerization facilitated the synthesis of a series of novel polyesters composed of dimethyl terephthalate (DMT) and various ratios of two bicyclohexyldimethanol (BCD) regioisomers, 3,4′-BCD and 4,4′-BCD. Proton nuclear magnetic resonance spectroscopy (1H NMR) confirmed successful incorporation of all monomers into the polymer backbone. The materials exhibited high thermal stabilities as evidenced by a consistent Td,5% around 390 °C. Further thermal studies using differential scanning calorimetry (DSC) revealed a close correlation between regioisomer content and polymer morphology. Polymers comprising 80% or higher 4,4′-BCD content were semi-crystalline with melting temperatures ranging from 142 to 216 °C, while materials with less 4,4-BCD were amorphous. Density studies showed a direct correlation between amorphous density and 3,4-BCD content, which also corresponded to young’s moduli. Dynamic mechanical analysis (DMA) revealed sub-Tg β-relaxations with similar intensities for all polymer compositions, suggesting that energy absorption at low temperatures is influenced by the unsaturated rings in the BCD diol. Tensile mechanical testing indicated the longest elongation at break (34%) for the 50% composition of both regioisomers, while considerably less elasticity was observed for the homopolymers of either regioisomers with elongations at break &lt;5%.

Effect of regioisomer ratios on physical properties of poly(bicyclohexyldimethylene) terephthalate

ACS Spring Meeting 2021

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