Solvent effects on the formation of cross-linking microspheres in γ-irridiated solutions

Solvent effects on the formation of cross-linking microspheres by the radiation-induced polymerization are described. Polymerization of some bi- and tri-vinyl monomers in several organic solvents was tested. Diethylene glycol dimethacrylate (2G) is the unique monomer that gives microspheres. The distance between two vinyl groups of monomer molecules is one of the important factors for the formation of microspheres. The comparison of the solvent properties for the preparation of microspheres suggests that the forms of the monomer molecules in the solutions are also important, that is, the stretched form is favorable. Alcohols, except t-butanol, are not favorable as the solvents for the preparation of microspheres because of not only solubility but also an occurrence of the chain transfer reaction. The chain transfer reactions to the solvents and additives interfere with the formation of microspheres.