Tunable polymorphic crystal modification, phase transition and biodegradability of poly(1,4-butylene adipate) by a bio-derived metabolite with low molecular weight

Abstract

Via the H-bond interaction, the 3,4-dihydroxy hydrocinnamic acid (HCA, a low molecular weight compound with biocompatibility) decreased the melt-crystallization temperature (Tc), crystallization rate and relative degree of the crystallinity of the poly(1,4-butylene adipte) (PBA) polyester. In the case of the lower weight fraction of the HCA (fHCA = 1-5%), the H-bond exists between the -CH2 segment of the HCA and -C=O group of the PBA. When fHCA = 10-30%, there is a larger H-bond strength between the HCA and PBA, and the -C=O segment of the HCA interacts with the -CH2 segment of the PBA. The HCA facilitated the generation of the PBA alpha-modification at a lower Tc and accelerated the transition from the beta- to alpha-phase. The polymorphism and phase transition of the PBA could be tuned by the HCA. Lower fHCA enhanced slightly the thermal degradation temperature (Td), but higher fHCA decreased the Td of the PBA. The HCA increased the biodegradability of the PBA. Mechanisms on reduced critical Tc of the PBA alpha-modification (Tc,α), speeded up phase transition, enhanced biodegradability and dual effects of the HCA on the thermal stability of the PBA, were also proposed and discussed systematically and in depth.