ANIONIC DISPERSION POLYMERIZATION OF STYRENE .2. MECHANISM OF PARTICLE FORMATION

The mechanism for the formation of uniform micron-size polystyrene par ticles by anionic dispersion polymerization of styrene in hexane mediu m was investigated. Uniform particles in the range of 2.28-7.14 mu m w ere obtained by varying the polymerization parameters such as the stab ilizer, initiator, monomer multi-addition, and temperature. Particles of larger size and narrow molecular weight distribution were formed by increasing the initiator concentration. The particle size also increa sed with decreasing stabilizer concentration and polymerization temper ature. The formation of larger size particles at lower temperature, lo wer stabilizer, and higher initiator concentrations provides supportin g evidence that particle nucleation in anionic dispersion polymerizati on is due to a polymer chain aggregation mechanism. (C) 1996 John Wile y & Sons, Inc.