Crosslinkable dextrin-coated latex via surfactant-free emulsion polymerization

Abstract

Emulsion polymerization remains the most attractive method to produce waterborne dispersions for coatings and adhesives, thanks to the use of water as dispersion medium. The possibility to replace the surfactants necessary for the stabilization by biopolymers would make this polymerization route even more attractive to alleviate the shortcomings of surfactants. Herein, dextrins were used as sole stabilizer to produce stable latex dispersions by emulsion polymerization with solid contents up to 55 wt% and narrow size distributions. The H2O2/ascorbic acid redox initiator was found to be the most effective, ensuring a complete polymerization at 50 °C within 3–4 h, giving rise to dextrin-functionalized polymer latexes with a particle size between 150 and 600 nm. The stabilization was explained by the coating of the polymer particles with a chemically bound layer of dextrins, forming a steric barrier. The functionalization of the latex particles by dextrins was exploited to induce a post-crosslinking of the polymer by the inclusion of additives capable of reacting with dextrins. As application, a crosslinkable pressure-sensitive adhesive was prepared and used without any additive. Given the biobased origin of the dextrins and their availability, their use as sole stabilizer in emulsion polymerization is promising to produce waterborne latex dispersions for coatings, adhesives, inks, drug delivery, and textiles.