Synthesis and characterization of cellulose nanocrystal-graft-poly(d-lactide) and its nanocomposite with poly(l-lactide)

As a popular bioplastic, poly (l-lactic acid) (PLLA) still faces some drawbacks mainly related to its low crystallization rate and heat distortion resistance. Herein, we demonstrate a facile and promising route to solve these problems by compositing PLLA with poly(d-lactide) grafted cellulose nanocrystal (CNC-g-PDLA) which can be synthesized via ring-opening polymerization of d-lactide on the CNC surface. The grafting density of PDLA on the CNC surface has been quantified by newly developed spectral method using FTIR technique. Moreover, the non-isothermal and isothermal crystallization behavior of PLLA/CNC-PDLA composites has been investigated by DSC, POM and WXRD. Our results show that the addition of small amount of CNC-g-PDLA could enhance the crystallization rate of PLLA significantly due to the heterogeneous nucleation effect of CNC and the presence of stereocomplex crystals. In addition, the specific stereocomplex interaction in the interphase of PLLA matrix and modified CNC particles results in great improvement of both storage modulus and the heat distortion resistance of the PLLA/CNC-g-PDLA nanocomposites. This study provides a way to design advanced PLLA-based nanocomposites with fast matrix crystallization ability and excellent heat distortion resistance.