Modification of nanocrystalline cellulose for application as a reinforcing nanofiller in PMMA composites

Nanocrystalline cellulose (NCC) with particle length of 100-500 nm was prepared from microcrystalline cellulose and modified with a reversible addition-fragmentation chain transfer (RAFT) agent, i.e., 4-cyano-4-(phenylcarbonothioylthio)pentanoic acid (CPADB). From the surface of CPADB-modified NCC, methyl methacrylate (MMA) was grafted to produce poly(methyl methacrylate) (PMMA)-modified NCC. Unmodified NCC, CPADB-modified NCC, and PMMA-modified NCC were further used as reinforcing nanofillers in PMMA composite plates prepared by bulk polymerization of MMA. Regardless of NCC type, the PMMA plates were transparent to visible light at low NCC concentrations but became translucent with increasing NCC concentration. At given NCC concentration, the visible-light transparency of the PMMA/NCC composites decreased in the order PMMA-modified NCC, CPADB-modified NCC, unmodified NCC. PMMA-modified NCC and CPADB-modified NCC showed moderate potential for reinforcing the PMMA matrix, while unmodified NCC detrimentally affected the mechanical properties of the PMMA composites due to more pronounced particle aggregation.