Redox-Mediated Incorporation of Sulfated Cellulose Nanocrystals into PVAc Latex: A Comprehensive Structure–Property-Durability Investigations

Abstract The role of a redox initiator, in combination with a nonionic surfactant and poly(ethylene glycol) methacrylate (MPEG), was investigated in the synthesis of nanocomposites of sulfated cellulose nanocrystals and vinyl acetate (VAc) via semibatch emulsion polymerization. This study also explored the effects of heat treatment, including prolonged exposure and annealing. An increase in the CNCs concentration led to aggregation and the formation of larger, irregularly shaped polymer particles. Microscopy analysis indicated increased surface roughness at higher CNCs loadings. The reduction in the optical transparency of the nanocomposites was mitigated by annealing. The contact angle of the untreated samples increased after thermal treatment, particularly at higher CNCs concentrations, by approximately 160%. Water uptake was minimized at 0.6 wt %, and the lowest permeability was observed at 1.9 wt % of CNCs/VAc. The glass transition temperature of the nanocomposites was significantly reduced by 8 °C only under the combined effect of higher CNCs loading and annealing. Annealing resulted in an increase in the storage modulus, particularly for nanocomposites with 1.9 wt % of CNCs/VAc. Creep decreased significantly at high CNCs concentrations after annealing. The elastic modulus and ultimate strength increased with the CNCs content, achieving enhancements of 356% and 80% postannealing for 1.9 and 2.5 wt % of CNCs/VAc, respectively. Finally, the thermal stability of the nanocomposites improved, although variations in the CNCs concentration had minimal additional impact. These results provide insights into how CNC incorporation into poly(vinyl acetate) latex affects the mechanical, barrier, and surface properties of water-based coatings in applications such as paper coating.