Cellulose nanocrystals as initiator of ring-opening polymerization of ε-caprolactone: Mathematical modeling and experimental verification

Abstract

Cellulose nanocrystals (CNC) occupy a privileged position among the fillers for in situ synthesis of polymer nanocomposites because such nanoparticles can be used as mechanical reinforcement, while acting as an initiator for ring-opening polymerization (ROP). Although the use of CNC as reinforcement material is well established, their use as initiator during the preparation of polymer nanocomposites – particularly as a source of superficial hydroxyl groups (OH) – has only received limited attention to date. Herein, CNC were used as the initiator for ring-opening polymerization of ε-caprolactone (CL), and the effect of their superficial OH groups on such synthesis was studied experimentally and computationally. The results demonstrated that part of hydroxyl groups from CNC participates in the polymerization reaction as initiators, promoting the growth of the polycaprolactone (PCL) chains onto the CNC surface, and therefore allowing the successful in situ preparation of PCL-grafted CNC (PCL-g-CNC). Moreover, good agreement between experimental results and computer simulation was found, allowing predicting the characteristics of PCL-g-CNC. The presented study provides further understanding of surface modification of CNC and in situ synthesis of polymers and nanocomposites, which is useful to researchers and facilitates progress in the synthesis and applications of such materials.