Rationalization of solvent effects in the solution polymerization of styrene

Abstract

Batch solution polymerization of styrene was investigated using seven solvents, namely acetone, chloroform, benzene, toluene, acetonitrile, ethyl acetate, and dimethyl sulphoxide (DMSO), to elicit solvent effects on the monomer conversion. Two separate initiators, benzoyl peroxide (BPO) and its blend with dicyclohexylphthalate (BPO blend), were used to unveil solvent – initiator interaction. The results indicate that monomer conversion was highly influenced by nature of solvent. Acetone gave the highest monomer conversion while toluene gave the least conversion of all seven solvents studied irrespective of the initiator. Correlation of solvent parameters with conversion using linear solvation energy relationship of Kamlet and Taft indicates varying behavior in the two initiators. For benzoyl peroxide, dipolarity/polarizability and Reichardt electrophilicity demonstrate the most positive effect on monomer conversion, while refractive index, dielectric constant and Lewis acid – base interactions between the solvent and initiator show negative effect. On the other hand, for the BPO blend, dipolarity/polarizability, electrophilicity, and Lewis acid – base interactions all show positive influence on conversion, while refractive index and dielectric constant have negative effect. Acetone is the ideal solvent for solution polymerization of styrene based on monomer conversion and ease of solvent separation.