Stereocontrol during the radical polymerization of methyl methacrylates with combined Lewis acids: Aluminium trichloride (AlCl3) and iron dichloride tetrahydrate

Abstract

The radical polymerization of methyl methacrylate (MMA) was carried out in the presence of combined Lewis acids of the AlCl3-FeCl2 system. Compared with the polymerization produced in the presence of single Lewis acids, AlCl3 or FeCl2, the MMA polymerization in the presence of AlCl3-FeCl2 composite in CHCl3 or 1-butanol produced a polymer with a higher isotacticity and in toluene produced a polymer with a much higher isotacticity (mm = 50%). The molecular weight and polydispersity of PMMA in the presence of Lewis acids were similar with those in the absence of Lewis acids, although Lewis acids decelerate the polymerization of MMA. The effects of the Lewis acids were greater in a solvent with a lower polarity. A possible stereocontrol mechanism of the polymerization was proposed. The Lewis acid composite of AlCl3-FeCl2 readily formed a complex with growing species. These complexes possessed apparent bulkiness that changes the direction of monomer addition to the growing radical center.