Polylactide stereocomplexation facilitated by the self-assembly of complementary ion pairs at the terminal group

Herein, we demonstrate that self-assembly promoted by complementary ion pair interactions can facilitate the stereocomplexation of polylactides. Poly-l-lactide (PLLA)-COOH and poly-d-lactide (PDLA)-COOH, and PDLA-Py and PDLA-NH2 functioned as PLAs with acidic and basic terminal groups, respectively. While two melting temperatures corresponding to the homocomplex and stereocomplex crystalline phases were observed in sc-PLA composed of PLLA-COOH and PDLA-COOH, only one melting temperature corresponding to the stereocomplex crystalline phase was observed in the case of the stereo-ion-complex composed of PLLA-COOH and PLLA-Py or PDLA-NH2. The self-assembly of PLAs through ion pair interactions was observed in diffusion-ordered NMR spectroscopy (DOSY) analysis. In summary, interactions of complementary ion pairs in PLAs containing an acidic and a basic terminal group facilitated the formation of a stereocomplex composed of PLLA and PDLA, dominated by the stereocomplex crystalline phase.