Encapsulation of cellulose nanocrystals into acrylic latex particles via miniemulsion polymerization

Abstract

Cellulose nanocrystals (CNCs) show promise for enhancing properties of waterborne latexes and coatings. Miniemulsion polymerization is a promising route to obtaining well-controlled latex distributions sufficient to encapsulate CNCs in the monomer phase. Here, we demonstrate the first miniemulsion polymerization resulting in encapsulation of CNCs that incorporates costabilizer, water soluble initiator, and comonomer mixtures, aspects that are important for practical implementation. CNCs were added to the monomer phase as either unmodified (umCNC) or one of two functionalized forms: modified with isocyanatoethyl methacrylate (mCNC, containing a polymerizable vinyl group) or grafted with butyl acrylate/methyl methacrylate copolymer (gmCNC). The gmCNCs were incorporated successfully into acrylic particles. In contrast, the umCNCs were located outside the formed latex particles. Interestingly, the mCNCs coagulated during the polymerization, highlighting the challenge of utilizing polar and reactive acryloyl CNC surface modifiers that lead to migration from the droplet phase.