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

A series of bio-based poly(lactide)-b-poly(1,3-trimethylene glycol)-b-poly(lactide) copolymers covering a wide range of compositions were synthesized by ring-opening polymerization (ROP) of L- or D,L-lactide initiated by bio-based poly(1,3-trimethylene glycol). The copolymers were obtained 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 exhibited a single glass transition temperature (T_g), which increased quasi-linearly with increasing lactide content, indicating good miscibility between polyether and polyester blocks. Furthermore, they demonstrated thermal stability up to approximately 250 °C and exhibited a two-step decomposition process, corresponding to the degradation of polyester and polyether segments. Finally, the amphiphilic nature of these copolymers was confirmed, as all of them were able to self-assemble in water, forming spherical nanoparticles with ζ-average diameters ranging from 95 to 158 nm.