Synthesis and properties of l-lactide/1,3-dioxolane copolymers: preparation of polyesters with enhanced acid sensitivity

Abstract

Herein, we report the first example of cationic ring-opening copolymerization of 5-membered cyclic acetal (1,3-dioxolane (DXL)) with L-lactide (LA) to afford polylactide containing acetal units. Copolymers with different compositions (containing up to 27 mol% DXL) were obtained in the presence of 1,2-ethanediol as an initiator and triflic acid as a catalyst. The incorporation of DXL into the polyester chain was examined by ¹H and ¹³C NMR. Additionally, two-dimensional nuclear magnetic resonance spectroscopy (heteronuclear single-quantum correlation spectroscopy (HSQC)) was used for the identification of DXL units in the polyester chain. The obtained copolyesters were amorphous and exhibited glass transition temperatures (T_g) that were strongly dependent on the copolymer composition and ranged from 8 °C to 32 °C. When subjected to hydrolysis in an acidic environment, PLA/PDXL copolymers showed accelerated degradation in comparison with the PLA homopolymer. The new polyesters containing acid-sensitive sequences may extend the field of degradable materials.