DISPERSION COPOLYMERIZATION OF STYRENE AND DIVINYLBENZENE - SYNTHESISOF MONODISPERSE, UNIFORMLY CROSS-LINKED PARTICLES

Monodisperse, crosslinked polystyrene latexes were prepared by the dis persion technique. Some general observations regarding the effect of i nitial reagent concentrations on final particle size and size distribu tion are offered, in addition to a detailed discussion concerning the problems encountered with the use of the crosslinker divinylbenzene (D VB) in latex preparation. Particles synthesized in very polar media we re found to reach their growth plateau sooner than those made in less polar surroundings. This trend was proposed to be the result of more e ffective nucleation in polar environments, which increases available s urface area, thereby allowing the rapid replacement of monomer consume d within the particle phase during the polymerization. Attempts to fav orably influence the growth rate and size distribution of particles du ring the reaction were unsuccessful, underlining the importance of the nucleation period in defining particle size characteristics. Up to 1% DVB was successfully incorporated in the synthesis of coagulum-free, monodisperse, 5 mu m beads, by controlling the entry of the crosslinke r into the particle phase during the major particle growth period. Lat ex stability is proposed to be largely dependent on the mobility of th e adsorbed steric stabilizer. (C) 1995 John Wiley and Sons, Inc.