Behavior of nonionic emulsifier molecules on the preparation of nanoparticles from submicron-sized ionized styrene-methacrylic acid copolymer particles by the particle dissolution method

Submicron-sized styrene-methacrylic acid copolymer (92/8 molar ratio) particles dissolved in the presence of polyoxyethylene nonyl-phenylether nonionic emulsifier under alkaline conditions at 90 degrees C, resulting in nanoparticles with diameters of about 30 nm. In order to clarify the role of the emulsifier molecules in the dissolution process, H-1 NMR measurements were carried out. As the particles swelled, the NMR integrals due to the emulsifier decreased markedly. This indicates that the emulsifier molecules permeated into the inside of the alkali-swelling particles and were adsorbed on the polymer molecules, which supports the formation mechanism of nanoparticles by the particle dissolution mettled proposed in a previous article.