Modification of cellulose nanocrystal via SI-ATRP of styrene and the mechanism of its reinforcement of polymethylmethacrylate

•Cellulose nanocrystals were grafted with polystyrene via SI-ATRP.•The functionalization of the CNC surface favored its dispersion in the PMMA matrix.•The thermal and mechanical properties of PMMA were improved with reinforcement of CNC.•The transparency of nanocomposites was particularly presented.