Transparent CNF/PMMA composite plate prepared through pickering emulsion–assisted aqueous polymerization

Abstract Cellulose nanofibers (CNFs) are biomass-derived nanoscale reinforcements that combine high optical transparency, excellent mechanical properties, and low thermal expansion, rendering them ideal candidates for reinforcing transparent polymers. However, achieving a uniform dispersion of CNFs in common transparent polymers, such as polymethyl methacrylate (PMMA), remains challenging owing to interfacial incompatibility and the requirement of complex multistep processes. In this study, we developed a straightforward aqueous polymerization strategy for preparing transparent CNF/PMMA composites on the basis of CNF-stabilized Pickering emulsions. The CNF/PMMA composite powders containing 2 or 5 wt% CNFs were obtained through the filtration-based recovery of the polymerized product, followed by drying. By heat molding these powders, transparent CNF/PMMA plates with mm-scale thicknesses were prepared. Compared with those of neat PMMA, the thermomechanical properties of the resulting composites significantly improved because of the uniform dispersion of the CNFs and the efficient formation of a percolating network. Compared with that of neat PMMA, the storage modulus of the 5 wt% CNF/PMMA composite increased by approximately 4500%, suggesting the formation of a stiff CNF network structure. This study highlights the effectiveness of Pickering emulsion templating for constructing nanostructured polymer composites with improved thermal and mechanical performance and their potential for transparent structural applications in the automotive, architectural, and optical fields.