Ultrasonic initiation of polystyrene latex synthesis

Abstract

Polystyrene latex samples have been synthesised from an oil-in-water (o/w) emulsion of the monomer using ultrasonic irradiation as the initiation source. No added chemical initiators were used in any of the reactions. The free radicals formed from the cavitation process under the action of the ultrasound are sufficient to initiate the polymerisation. In the current study, the effects of varying the input intensity of the ultrasound were investigated. A marked increase in the monomer conversion rate as a function of time was seen as the power was increased. Despite this increase in conversion rate, the increasing intensity did not affect the resultant latex particle sizes. In all cases, the particle diameters at the conclusion of a polymerisation were seen to be in the range of 40 to 50 nm. The effects of changing the concentration of surfactant in the polymerisation medium and of changing the temperature were also probed. Increases in both were seen to lead to an increased rate of conversion at a fixed input intensity. Again, the particle diameters were invariant as a function of changing conditions. The small particle sizes and high conversion rates are thought to be due to a continuous nucleation process that is caused by the scavenging of free radicals throughout the polymerisation by freshly formed small oil droplets.

Emulsion Polymerization Synthesis of Cationic Polymer Latex in an Ultrasonic Field

“…The advantages include the ability to conduct polymerizations at room temperature and the elimination of problems usually associated with a chemical initiator. Research to date in the field of sonochemically induced emulsion polymerization has resulted in the preparation of many types of anionic latex (2,(12)(13)(14). Small particle size and high molecular weight are common features of these particles but little is known about the mode of polymerization.…”

Two-stage mathematical model of ultrasonically initiated emulsion polymerization part one, stage I

“…So for an alone particle, if it has 0.5 monomeric radical all the time, its radius will increase within 1 h from zero to about 38 nm for St and 59 nm for MMA, respectively. However, the actual radii are only about 10 nm for St [18] and 25 nm for MMA calculated from Chou's [15] experimental data. So the average radical number must be far-forth less than 0.5.…”

“…Thus, different from the conventional emulsion polymerization, there only exist the acceleration and deceleration stage in the ultrasonically initiated emulsion polymerization. Many researchers [16,18] have observed this phenomenon. In this paper, we proposed a two-stage mathematical model of the ultrasonically initiated emulsion polymerization.…”

“…However, due to the introduction of the ultrasound, the polymerization mechanisms become more complex. Different from the conventional emulsion polymerization, where the course could be divided into three intervals, many researchers [16,18] found there only existed two stages, the acceleration stage and deceleration stage. However, no theory explained why the stage of the constant velocity was disappeared.…”

Suspension Polymerization of Styrene Monomer without Emulsifier and Initiator.

“…Suspension polymerization gives spherical polymer particles since it proceeds while the dispersed monomer droplets keep their spherical shape (1,2). Addition of surfactant is usually essential for suspension polymerization to ensure a high dispersion stability of monomer droplets (3,4). But the surfactant remaining in the polymer particles formed is difficult to remove.…”