Synthesis of narrow or monodisperse poly(divinylbenzene) microspheres by distillation-precipitation polymerization

Highly cross-linked narrow or monodisperse poly(divinylbenzene) (PDVB) microspheres were prepared by distillation-precipitation polymerization as a novel polymerization technique in acetonitrile with 2,2'-azobis(2-methylpropionitrile) (AIBN) as initiator. The polymeric microspheres were formed simultaneously through a precipitation polymerization manner during the distillation of acetonitrile off the reaction system. Narrow or monodisperse particles with spherical shape and smooth surface were prepared with diameters between 1.10 and 3.41,mum without any stabilizers. The particle size and size distribution depended on the reaction conditions. The maximum particle size of 2.14 mum with size distribution index of 1.058 was attained at cross-linking degree of 64%, and the size distribution became narrower with increasing cross-linking degree. The particle sizes increased with increasing monomer and initiator concentration. A series of polymer particles with diameter between 1.99 and 3.41 mum were obtained by multi-semibatch mode with successive introduction of a mixture of the designed amount of AIBN and divinylbenzene containing 80% divinylbenzene (DVB80) in acetonitrile into the distillation-precipitation polymerization, and the size distribution index was kept around 1.02. Furthermore, the conversion increased from 31% for the first aliquot to 76% for the sixth aliquot. All of the resulting microspheres were characterized with SEM.