Radical polymerization of itaconic acid in dipolar aprotic solvents − The effect of high monomer concentration

In this study, the dipolar aprotic solvents were used as reaction systems for homopolymerization of itaconic acid (IA). The influence of the dipolar aprotic solvent properties, as represented by the Kamlet-Taft parameters, on the solubility of IA was elucidated using the Linear Solvation Energy Relationships (LSER). Hydrogen bonding in IA solutions was investigated through FT-IR spectroscopy and viscosity measurements. It was found that high IA solubility caused by strong hydrogen bond basicity of the solvents, is a key factor affecting its radical polymerization process, as evidenced by the exponential increase in the molecular weight of the resulting poly(itaconic acid) (PIA) with increasing initial IA concentration. This phenomenon can be explained by diffusion controlled termination of polymerization caused by viscosity of the reaction system. Among the solvents tested, DMSO was identified as the most suitable solvent for IA polymerization due to its high solubility. By using this solvent, average molecular weight of the resulting PIA could be tuned over a wide range from 1 000 to 100 000 g/mol.