Tacticity Control in the Bulk Free Radical Polymerization of Methyl Methacrylate Utilizing Ionic Liquids

The stereochemistry of polymethyl methacrylate (PMMA) has a profound influence over its material properties; however, the pursuit of high tacticity in bulk free radical polymerization presents a formidable challenge. Consequently, the procurement of a methodology that facilitates the synthesis of highly tactic polymers during bulk free radical polymerization is both desirable and challenging. In this investigation, the propagation of methyl methacrylate (MMA) within an ionic liquids (ILs) medium was employed via bulk free radical polymerization to harness tacticity. The reactivity of polymerization and the propensity for isotactic polymer formation were potentiated by the incorporation of ILs, specifically 1-octyl-3-methylimidazolium hexafluorophosphate as an additive. The resultant polymer exhibited a triad isotacticity (mm) of 33%, achieved in the presence of a 5 wt% concentration of 1-octyl-3-methylimidazolium hexafluorophosphate. The isotactic selectivity of the ILs appeared to arise from their dynamic interplay with the monomeric or polymer chains, an interaction elucidated by 1 H NMR and DFT analyses. The research imparts critical understanding into the manipulation of PMMA tacticity and presents an enaging prospect for the production of highly tactic polymers via bulk free radical polymerization.