PREPARATION OF MICROSPHERES BY RADIATION-INDUCED POLYMERIZATION .2. MECHANISM OF MICROSPHERE GROWTH

The effects of the monomer concentration were investigated on the preparation of diethylene glycol dimethacrylate (2G) microspheres by radiation-induced polymerization. The monomer concentration strongly affected the conversion and the shape of the microspheres. The particles were obtained in the range from 2 to 24 vol % of 2G monomer. The effective concentration for the preparation of monodisperse microspheres is around 10 vol %. Higher monomer concentrations up to 24 vol % gave rough surface particles. Considering the effects on the number of microspheres in the solution, the authors introduced the inhibiting region, where one microsphere disturbs the existence of another microsphere, and tried to explain the mechanism of the microsphere growth. The competition between the propagation and the crosslinking reactions is balanced to give the microspheres.