Physical modifications of cellulose nanocrystals by poly(d-lactic acid) and poly(ethylene glycol) (PDLA-PEG-PDLA) block copolymer to improve the mechanical properties of polylactide

As a green and renewable resource, cellulose nanocrystals (CNC) possess excellent mechanical properties, rendering them a favorable option for modifying polymer materials. However, improving their dispersibility in the matrix and enhancing the interface are the crucial to exploit their advantages. The physically modified CNC (mCNC) are prepared by exploiting hydrogen bonding between CNC and the block copolymer of poly(d-lactic acid) and poly(ethylene glycol) (PDLA-PEG-PDLA) through a solvent exchange method. The incorporation of the copolymer not only enhances the dispersity of CNC, but also facilitates the formation of the stereocomplex crystal (SC) structure in PLA, thereby concurrently enhancing the interface. Consequently, the PLA/mCNC nanocomposites demonstrate a notable increase in crystallization ability and the mechanical properties. In comparison to neat PLA, the yield strength, elongation at break, and tensile toughness experienced significant enhancements of 11.2 %, 265.9 %, and 280.2 %, respectively. This facile method provides a good basis for the large-scale application of cellulose nanocrystals.