Cellulose Nanocrystals and Methyl Cellulose as Costabilizers for Nanocomposite Latexes with Double Morphology

Cellulose nanocrystals (CNCs) are sustainable rigid rod-shaped nanoparticles that have potential as reinforcing agents in polymer nanocomposites. CNCs can also act as Pickering stabilizers in emulsions and foams due to their amphiphilic nature. In this work, CNCs were rendered surface active through adsorption with the biopolymer methyl cellulose (MC) to produce MC-coated CNCs. MC-coated CNCs were used to stabilize the microsuspension polymerization of methyl methacrylate. Monomer conversion, latex size, and gel content were studied. The microsuspension polymerization resulted in a double morphology where poly(methyl methacrylate) (PMMA) microparticles and nanoparticles were produced simultaneously. The ratio of micro- to nanoparticles could be tuned based on the CNC:MC ratio. Most nanoparticles were attached to the microparticles offering hierarchically structured latexes, although approximately 2 wt % were free in suspension. Drying conditions could be used to control the surface roughness of the dry latex particles. This work provides a new strategy for the incorporation of CNCs into polymer latexes and the ability to control their morphology. This method could be used to produce CNC-based adhesives, toners, cosmetics, and coatings, providing a greener route compared to solvent-based polymerization while replacing synthetic surfactants with CNCs and MC which are derived from renewable resources.