Tailoring Cellulose Nanocrystal and Surfactant Behavior in Miniemulsion Polymerization

Cellulose nanocrystals (CNCs) combined with surfactants were used to stabilize miniemulsion polymerization reactions. Anionic CNCs with H+ and Na+ counterions and cationic-modified CNCs were investigated with anionic and cationic surfactants. When oppositely charged CNCs and surfactants were mixed, CNC size increased and absolute zeta-potential decreased, indicating surfactant adsorption and the ability to costabilize the monomer/water interface. Colloid-probe atomic force microscopy showed that surfactant adsorption to CNCs is strongly dependent on the CNC surface charge and counterion. Miniemulsion polymerization of poly(methyl methacrylate) (PMMA) was performed in the presence of CNC–surfactant mixtures; latexes were produced giving PMMA nanoparticles when there was no interaction between CNCs and surfactant and PMMA microparticles when CNCs and surfactant acted as costabilizers. This shows that CNCs can be used with surfactants to stabilize miniemulsion polymerization, reducing the need for a hydrophobe and leading to latexes with tunable properties (size, size distribution, surface charge, and polymer molecular weight) for coatings, adhesives, and household/personal care products.