Aliphatic/aromatic copolyesters containing biobased omega-hydroxyfatty acids: Synthesis and structure-property relationships

A family of unique aliphatic-aromatic copolyesters was prepared by bulk condensation copolymerizations of bio-derived omega-hydroxytetradecanoic acid (H) with 1,4-butanediol (B) and dimethyl terephthalate (DMT). 1H NMR analysis showed the copolyesters have random repeat-unit sequence distributions. Thermal properties strongly depend on molar composition. Melting temperatures are lower than 70 °C for compositions rich in H-units; Tm varies from about 140 to 180°C for copolymers with high butylene terephthalate (BT) content. Crystal lattice structures shift from the crystal phase of poly(omega-hydroxytetradecanoate) (PH) to that of PBT with increasing BT copolymer content, while the minor component is trapped in the crystallizable domains as defects. The amorphous phase is homogeneous for all compositions and Tg increases from -21 °C (PH homopolymer) to 61 °C (PBT). Also, mechanical properties vary in a continuous way, according to copolymer composition. Therefore, the combination of aliphatic and aromatic units enables molecular design of partially biobased materials with adjustable thermal and physical-mechanical properties. Thus, by judicious selection of copolymer composition, material properties can be fine-tuned to attain the desired balance of material rigidity, ductility, melting point and biobased content.