Stereocontrol in Radical Polymerization of Acrylamides with Combined Lewis Acids of AlCl3-FeCl2

The radical polymerizations of acrylamide (AM) and N,N'-dimethyl acrylamide(DMAA) were carried out in the presence of combined Lewis acids of AlCl3-FeCl2system. Comparing with the polymerization produced in a single Lewis acidsystem of AlCl3 or FeCl2, the AM polymerization catalyzed by a combined AlCl3-FeCl2composite in CHCl3 produced a polymer with higher isotacticity (m = 36%). The DMAApolymerization in the presence of AlCl3-FeCl2 composite produced a polymer of higherisotacticity (m = 83%) in CHCl3 and a much higher isotacticity (m = 91%) in toluene.The molecular weight and polydispersity of PAM and PDMAA show identical resultswhether polymerized in the presence or absence of Lewis acids. The combined Lewisacids showed great isotacticity in a lower polar solvent and the stereochemistry of thepolymerization was clearly affected by the molar ratio of combined Lewis acids (AlCl3-FeCl2). The polymerization of AM in the presence of 0.03-0.03 mol/L AlCl3-FeCl2composite system gave a polymer with dyad tacticity of 59/41 (m/r), the polymerizationof DMAA in the presence of 0.015-0.015 mol/L AlCl3-FeCl2 composite system gave apolymer with dyad tacticity of 95/5 (m/r). Furthermore, the isotactic specificity ofcombined Lewis acids on AM and DMAA were also influenced by aging temperatureand aging time. The optimum aging temperature of polymerization was 80°C, and theoptimum aging time was 1 h.