Dispersion copolymerization of styrene and divinylbenzene: Synthesis of monodisperse, uniformly crosslinked particles

Abstract

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 μm 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. © 1995 John Wiley & Sons, Inc.

Kinetics of polymerization and particle stabilization mechanism on dispersion copolymerization of styrene and divinylbenzene

“…3 Suspension polymerization is an ineffective method for achieving monodisperse particles because of the inherent nonuniform in the mechanic disperse systems. 4 Monodisperse microspheres in the size range of 20 -30 m was obtained by microgravity suspension in the space, but the product is very expensive. Professor He Bing-Lin proposed an improved microsuspension technique to prepare microsize microspheres of polystyrene (PS), but the size distribution was not monodisperse.…”

Dispersion copolymerization of styrene and divinylbenzene. II. Effect of crosslinker on particle morphology

“…To this end, the relatively little used technique of dispersion polymerization was selected, primarily because it allows the production, in a single reaction, of monodisperse latexes with diameters in the desired [5][6][7][8][9][10] pm range. The mechanism of the dispersion polymerization of styrene in ethanol with poly(viny1 pyrrolidone) (PVP) as steric stabilizer was detailed el~ewhere,'~~ but the factors relevant to this discussion are that particle growth is radial and that stabilization occurs via adsorption of graft PVP-PS copolymer.…”

Hypercrosslinked polystyrene microspheres by suspension and dispersion polymerization

“…Before polymerization, the system was homogeneous, i.e., the monomers, stabilizer and initiator were dissolved in ethanol, but the polymer particles precipitated during the polymerization. As it is known that crosslinking agents interfered with the particle nucleation stage and immobilized the stabilizer, thus inducing flocculation [33], the addition of DVB was postponed to the end of the nucleation stage, an hour after the beginning of the reaction. Both the concentrations of styrene and BPO in ethanol were maintained constant during the experiments, only the HPC concentration was varied and its effect on properties of the resulting microspheres was investigated.…”