Preparation of Polystyrene Latex with Ultrasonic Initiation

Abstract

The polymerization of a styrene in water (o/w) emulsion was performed at 30 °C (±5 °C) under ultrasonic irradiation in the absence of any added chemical initiator. The radicals formed as a consequence of the cavitation process were sufficient to cause polymerization. The latices formed in this way were stable bluish-white dispersions. The polymerization rate increased through a maximum at about 30% conversion before decreasing; no region with a steady rate was seen. The final latex diameters were around 50 nm and the polystyrene molecular weights were high (>106), suggesting at most a few polymer chains per particle. Calculations of the particle numbers as a function of monomer conversion su..