Carboxyl carrying-large uniform latex particles

Abstract

Uniform polystyrene particles in the size range of 1.9–6.2 μm were used as the seeds in a multistep polymerization, to produce compact or macroporous particles in the size range of 3–13 μm with reasonably narrow size distributions (i.e. CV<5%). The seed particles with different sizes and molecular weights could be achieved by the dispersion polymerization of styrene. In the synthesis of carboxyl carrying-particles, the seed latices were first swollen by a low molecular weight-organic agent (i.e., dibutylphthalate, DBP), then by styrene (S)–methacrylic acid (MAA)–divinylbenzene (DVB) mixture including an oil-soluble initiator (i.e. benzoyl peroxide, BPO). The final particles were obtained by the polymerization of monomer mixture in the swollen seed particles by keeping the particle uniformity. The average size, size distribution, surface morphology and internal structure of the final beads were evaluated both by scanning and transmission electron microscopy. The average particle size slightly increased with the increasing DBP/seed latex and monomer/seed latex ratios. By keeping the particle uniformity, the size of carboxyl carrying-particles could be adjusted in a relatively wider range (i.e. 3–13 μm) by the selection of seed latex size. Titratable MAA contents between 69 and 181 mg g −1 were found for the particles produced under different conditions. Highly porous and carboxyl functionalized-uniform particles were obtained by starting from the polystyrene seed particles having number-average size and number-average molecular weight of 6.2 μm and 0.58×10 4, respectively. The smaller seed latices with higher molecular weights led to the synthesis of carboxyl carrying-particles with a non-porous surface and an internal part with crater-like porosity. In the case of porous particles, the surface porosity decreased significantly with the decreasing monomer/seed latex ratio and DVB feed concentration. Low monomer/seed latex ratios also resulted in a particle interior with crater-like pore structure.