Stereocomplex crystallization of high-molecular-weight poly(l-lactide)/poly(d-lactide) blends facilitated by strengthening intermolecular interactions

Stereocomplex-type polylactide (SC-PLA) composed of alternatingly packed enantiomeric chains has recently been regarded as a promising engineering bioplastic with favorable physical properties. However, it is challenging to realize its commercial applications since homocrystallization is fiercely competed with the SC crystallization in the melt-processing of enantiomeric poly( l -lactide) (PLLA) and poly( d -lactide) (PDLA) blends holding relatively high molecular weights (>100 kg/mol). Herein, a facile yet efficient strategy is proposed to facilitate the SC crystallization by using zinc acetate (Zn(OAc) 2 ) to strengthen intermolecular interactions. It is impressive to find that the addition of only 0.01 wt% Zn(OAc) 2 induces the selective formation of SC crystals (SCs) without any homocrystals (HCs), under various melt-crystallization conditions, exhibiting an extremely high efficiency in enhancing SC crystallizability. Moreover, the crystallization kinetic is significantly enhanced. Such enhancement could be ascribed to the metal-oxygen coordination between Zn 2+ ions from Zn(OAc) 2 and carbonyl group of PLAs, which favors the interactive collaboration between enantiomeric chains and thus lowers the barrier to the formation of SCs. This work provides valuable guidance for developing advanced SC-PLA materials with desirable crystallizability.