Poly(hexyl methacrylate) nanoparticles templating in nanoemulsions-made by phase inversion temperature

Nanoemulsions of water, Brij 56 and hexyl methacrylate (with a small amount of squalene as hydrophobe or costabilizer) were made by the phase inversion temperature (PIT) method and then polymerized. In the absence of squalene, the nanoemulsions destabilized within minutes; however with squalene, the nanoemulsions were kinetically stable for at least several hours, which is long enough to carry out the reactions, with diameters of narrow size distribution in the range from 32 to 44 nm, depending on the surfactant concentration. Polymerizations, carried out a 20°C using a par redox, were extremely fast (ca. 100% conversion in less than 5 min) yielding polymer particles of ca. 40 nm, which were similar to the original nanoemulsion droplets (ca. 35 nm), indicating that the nanoemulsion droplets act as templates, and that squalene diminishes substantially monomer diffusion between reacting and nonreacting monomer droplets. Molar masses were high and alike to those produced by microemulsion polymerization of this monomer, suggesting that chain transfer to monomer is the main termination mechanism.