| Lanthanide (II, III) metallocene initiators produce highly syndiotactic PMMA. Bis(pentamethylcyclopentadienyl)calcium (Cp2*Ca) and Yb(C6Me5)2 have similar bent sandwich structures and centroid angles. In the present study, Cp2*Ca was synthesized and used for MMA polymerization. Unlike lanthanide compounds, Cp2*Ca did not produce highly syndiotactic PMMA at 0°C. The syndiotacticity was 60% at 0°C. The less bulky auxiliary ligand (Cp) produced 80% syndiotactic PMMA at −10°C. Matrix assistant laser desorption/ionination (MALDI) techniques revealed the polymerization mechanism of MMA catalyzed by Cp2Ca. Termination involved cyclization. The titanium compound CpTiMe3 promoted fast polymerization of MMA in the presence of B(C6F5)3 at 0°C. However, there was no tacticity control.; Atom transfer radical polymerization (ATRP) was used to synthesize branched polymers and graft copolymers by the “grafting from” method. A novel branched PMMA with controlled backbone and side chain composition was successfully synthesized and characterized in this study. The repeat units between branches could be controlled by the MMA to 2-trimethylsilyloxyethyl methacrylate ratio. The grafting efficiency was 100% as determined by 13C NMR. Special interest was devoted to the graft copolymers in which the backbones and side chains differ in hydrophobicity. In this study, well-defined PMMA-g-poly(methacrylic acid) and poly(methacrylic acid)- g-poly(heptadecafluorodecyl acrylate) copolymers with controlled backbone and side chain architecture were successfully synthesized. The molecular weight of the grafted chains was controlled by the amount of monomer and macroinitiator added. Narrow molecular weight distribution was maintained throughout the reaction. NMR, FTIR, XPS, and contact angles were used to characterize the poly(methacrylic acid)-g-poly(heptadecafluorodecyl acrylate) graft copolymers. |
