A. Tuncel et al., Electron microscopic observation of uniform macroporous particles. I. Effect of seed latex type and diluent, J APPL POLY, 71(14), 1999, pp. 2271-2290
Uniform and macroporous polymer particles in the size range of 5-21 mu m we
re prepared by a multistep seeded polymerization method. The uniform polyst
yrene particles in the size range of 1.9-7.5 mu m were used as the seed par
ticles in the preparation of macroporous beads. The seed particles with dif
ferent sizes and molecular weights were produced by dispersion polymerizati
on, by changing the type of dispersion medium and the initiator concentrati
on. In the synthesis of macroporous particles, a two-step swelling procedur
e was employed. The seed latexes were first swollen by a low molecular-weig
ht organic agent (i.e., dibutyl phthalate, DBP), then by a divinylbenzene-e
thylvinylbenzene isomer mixture including an oil phase soluble initiator (i
.e., benzoyl peroxide). The porous structure in the final beads was achieve
d by the polymerization of the monomer phase within the swollen seed partic
les including a mixture of linear polystyrene and DBP. The initiator concen
tration in the repolymerization step, the seed latex type (i.e., the diamet
er and the molecular weight of seed latex), DBP/seed latex, and the monomer
/seed latex ratios were changed to achieve uniform polymer beads with diffe
rent average sizes and pore structures. The average size, the size distribu
tion, and the surface morphology of final beads were analyzed by Scanning E
lectron Microscopy. The internal structure of the beads were analyzed by Tr
ansmission Electron Microscopy. The results indicated that the average size
of the final particles increased with increasing the seed latex diameter,
DBP/seed latex, and monomer/seed latex ratios. The average pore size decrea
sed with decreasing the molecular weight of the seed latex and increasing t
he DBP/seed latex and monomer/seed latex ratios. These tendencies were expl
ained by the viscosity change of the porogen solution used in the repolymer
ization step. (C) 1999 John Wiley & Sons, Inc.