Enhanced biodegradable copolymers: Synthesis and characterization of high molecular weight poly(L‐lactide‐ <i>r</i> ‐ε‐caprolactone)

Abstract Semi‐crystalline poly(L‐lactide‐ r ‐ε‐caprolactone) (P(LLA‐ r ‐ε‐CL)) as an important biodegradable material applied in biomedical devices has attracted much attention from researchers. A series of high molecular weight P(LLA‐ r ‐ε‐CL) semi‐crystalline copolymers attached with various monomer molar ratio of L‐lactide (LLA) and ε‐caprolactone (ε‐CL) with up to 2.9 × 10 5 g/mol were synthesized first time by ring‐opening copolymerization under high vacuum condition. The chemical composition, chain sequence microstructure and their relationship of P(LLA‐ r ‐ε‐CL) were characterized by 1 H NMR and 13 C NMR. Spectra results shown that as the ε‐CL content increased from 3 mol% to 15 mol%, the average LLA sequence length decreased from 80.4 to 19.6 units. With decrease of LLA sequence length, the glass transition temperature ( T g ), melting temperature( T m ) and the crystallinity ( χ c ) of copolymers had a reduction. Meantime, it resulted in a high degradation rate of samples in enzyme‐catalyzed condition. With loss of rigid crystal and plasticization from soft ε‐CL segment, P(LLA‐ r ‐ε‐CL) had an improved toughness as the elongation at break reaching 195.5%, while still had a considerable tensile strength of 49.2 MPa. Further data analysis exhibited an exponential relationship between LLA sequence length and mechanical performance. Additionally, biocompatibility assessments through CCK‐8 and Live/Dead cell assays confirmed the good cytocompatibility of the enhanced biomedical materials.