Narrow disperse or monodisperse poly(DVB-co-EGDMA-co-MAA) microspheres with carboxyl groups were prepared by free-radical precipitation polymerization in neat acetonitrile

using 2

2'-azobisisobutyronitrile (AIBN) as initiator

methylacrylic acid as functional monomer

and highly hydrophobic divinylbenzene-55 (DVB-55) and polarity ethylene glycol dimethacrylate (EGDMA) as mixed crosslinker.The results showed that the feed radio of DVB-55 to EGDMA determined the particle size

size distribution

yield

thermal stability and loading capacity of the functional groups.The particle size of microspheres was in the range of 0.6~3.8 m

and monodisperse microspheres could be obtained when the ratio of DVB-55 to EGDMA was no less than 1∶1. Thermogravimetric analysis showed good thermal stability

enhancing with the percentage of DVB-55 in the mixed crosslinker.Moreover

with increasing the amount of DVB-55 in the mixed crosslinker

the measured values of the loading capacity of the accessible carboxylicacid group on the surface of the microspheres decreased

as well as the yield of microspheres.It was confirmed that the composition of the cross-linking monomers affected the particle size

size distribution and yield of microspheres.The studies on the compatibility between the two cross-linkers showed that the core of the polymer beads would contain more DVB units slightly

while the outer layer would contain preferentially the more abundant cross-linker added in the pre-polymerization mixture.