Polymerization of alkyl methacrylate nanoemulsions made by the phase inversion temperature method

Abstract

The polymerization of several alkyl methacrylates in nanoemulsions made by the phase inversion temperature method is presented here. The temperature versus surfactant concentration fish-like phase diagrams for a fixed mixture of alkyl methacrylate/squalane (SQ) of 95/5 w/w, Brij 56 and water were elaborated. Reaction rates were extremely fast (ca. 100% conversion in less than 3 min), and only two reaction rate intervals were observed, which is typical of nanoemulsion polymerization. It suggests that chain transfer to monomer is the main termination mechanism. The addition of squalane inhibits monomer diffusion from small droplets to larger ones and prevents the diffusion of monomer from non-reacting droplets to reacting ones, which guarantees that each monomer droplet acted as a nanoreactor. Polymer particles have similar size than the original nanoemulsion droplets indicating that the nanodroplets act as templates for the formation of the polymer nanoparticles. Reaction rates, as well as kinetics and nanoparticle characterizations by quasielastic light scattering (QLS), transmission electron microscopy (TEM), differential scanning calorimetry (DSC), and gel permeation chromatography (GPC), are reported. Spheroidal nanoparticles with similar sizes and narrow distribution were observed by TEM for poly(ethyl methacrylate), poly(butyl methacrylate), and poly(hexyl methacrylate). The large molar masses and the narrow molar mass distributions were obtained by gel permeation chromatography.