Bio-based poly(1,3-trimethyleneglycol-co-lactide) triblock copolymers: a promising platform for biomedical applications

Abstract

A series of bio-based poly(lactide)-b-poly(1,3-trimethylene glycol)-b-poly(lactide) copolymers covering the whole range of compositions was synthesized by ring-opening polymerization (ROP) of L- or D,L-lactide initiated by bio-based poly(1,3-trimethylene glycol). The copolymers were obtiained by bulk polymerizations carried out at 180 °C, using stannous octoate as the catalyst. The triblock structure was confirmed by both 1H NMR and SEC analyses. It was observed that molecular weights increased while dispersities decreased with the increasing content of lactide units in the copolymer. Copolymers prepared with L-lactide exhibited crystallinity with melting points and enthalpies increasing with the length of lactide blocks in the copolymers. In contrast, copolymers based on rac-lactide were fully amorphous, regardless of composition. All copolymers displayed a single glass transition temperature (Tg), which increased quasi-linearly with increased lactide content, indicating good miscibility betwen polyether and polyester blocks. Furthermore, they demostrated thermal stability up to aproximatelly 250 °C, and exhibited a two-step decomposition process, corresponding to the degradation of polyester and polyether segments. Finaly, the amphiphilic nature of these copolymers was confirmed, as all of them were capable to self-assemble in water, forming spherical nanoparticles with ζ-average diameters ranging from 95 to 158 nm.