Nanocellulose-assisted construction of hydrophilic 3D hierarchical stereocomplex meshworks in enantiomeric polylactides: towards thermotolerant biocomposites with enhanced environmental degradation

Abstract

The trade-off between high stereocomplexation and controllable environmental degradation still remains a great challenge in extending the use of stereocomplex (sc) biopolymers. In this work, we report for the first time the in situ construction of a hydrophilic and hierarchical 3D stereocomplexed crystalline meshwork in fully bio-derived enantiomeric polylactide/cellulose nanocrystal (PLA/CNC) nanocomposites, with a CNC induced growth process of sc crystallites and their subsequent self-organization at high pressure. The effective control of the mesh geometry/size/nature, with the variation of the crystallization temperature, pressure, time and CNC ratio, led to the formation of interconnected 3D sc meshworks with hierarchically micro/nanosized mesh holes and high stereocomplexation. The construction of the hierarchical 3D meshwork significantly increased the hydrophilicity of PLAs/CNCs with a water contact angle of 41.4°, which further facilitated water diffusion through the amorphous holes of the geometrically complex 3D meshwork, enabling the significantly enhanced hydrolytic degradation of sc PLA/CNC composites without sacrificing their heat resistance. The study presented here may propose a new interface engineering approach towards the design/fabrication of thermotolerant bionanocomposites with controllable environmental degradation.