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

Monodisperse, crosslinked polystyrene latexes were prepared by the dispersion technique. Some general observations regarding the effect of initial reagent concentrations on final particle size and size distribution are offered, in addition to a detailed discussion concerning the problems encountered with the use of the crosslinker divinylbenzene (DVB) in latex preparation. Particles synthesized in very polar media were found to reach their growth plateau sooner than those made in less polar surroundings. This trend was proposed to be the result of more effective nucleation in polar environments, which increases available surface area, thereby allowing the rapid replacement of monomer consumed within the particle phase during the polymerization. Attempts to favorably influence the growth rate and size distribution of particles during 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 crosslinker into the particle phase during the major particle growth period. Latex stability is proposed to be largely dependent on the mobility of the adsorbed steric stabilizer. (C) 1995 John Wiley and Sons, Inc.