Nitroxide-Mediated Copolymerization of Itaconate Esters with Styrene

Replacing petro-based materials with renewably sourced ones has clearly been applied to polymers, such as those derived from itaconic acid (IA) and its derivatives. Di-n-butyl itaconate (DBI) was (co)polymerized via nitroxide mediated polymerization (NMP) to impart elastomeric (rubber) properties. Homopolymerization of DBI by NMP was not possible, due to a stable adduct being formed. However, DBI/styrene (S) copolymerization by NMP at various initial molar feed compositions f(DBI,0) was polymerizable at different reaction temperatures (70-110 degrees C) in 1,4 dioxane solution. DBI/S copolymerizations largely obeyed first order kinetics for initial DBI compositions of 10% to 80%. Number-average molecular weight (M-n) versus conversion for various DBI/S copolymerizations however showed significant deviations from the theoretical M-n as a result of chain transfer reactions (that are more likely to occur at high temperatures) and/or the poor reactivity of DBI via an NMP mechanism. In order to suppress possible intramolecular chain transfer reactions, the copolymerization was performed at 70 degrees C and for a longer time (72 h) with f(DBI,0) = 50%-80%, and some slight improvements regarding the dispersity (D = 1.3-1.5), chain activity and conversion (similar to 50%) were observed for the less DBI-rich compositions. The statistical copolymers produced showed a depression in T-g relative to poly(styrene) homopolymer, indicating the effect of DBI incorporation.