PREPARATION OF NANOPARTICLES BY DISSOLUTION OF SUBMICRON-SIZED IONIZED STYRENE-METHACRYLIC ACID COPOLYMER PARTICLES IN NONIONIC EMULSIFIER SOLUTION

Styrene-methacrylic acid copolymer (P(S-MAA)) nanoparticles having hig h Tg were produced by a dissolution of submicron-sized P(S-MAA) partic les as follows. Submicron-sized P(S-MAA) particles having various MAA contents were produced by emulsion copolymerization. Secondly, they we re treated in a polyoxyethylene nonylphenylether nonionic emulsifier a queous solution at pH 13.0 and above 90 degrees C. The nanoparticles h aving about 30 nm in diameter were only produced from the particles ha ving MAA contents around 7 mol%, and above the contents, they were not produced. It seems to be based on that emulsifier molecules are not a dsorbed onto the polymer molecules enough to dissolve them. The effect of MAA content on such a dissolution behavior was examined using seve n kinds of different nonionic emulsifiers having hydrophile-lipophile- balance values between 12.2 and 18.2 at various temperatures and initi al pH.