Silicone Macroinitiator in the Atom Transfer Radical Polymerization of Methyl Methacrylate and Vinyl Acetate: Synthesis and Characterization of Pentablock Copolymers

Poly(dimethylsiloxane) (PDMS) based pentablock copolymers have been synthesized via atom transfer radical polymerization (ATRP) of methyl methacrylate (MMA) and vinyl acetate (VAc) telomer at 60 degrees C in the presence of CuCl/PMDETA as the catalyst system. The vinyl acetate telomer was prepared from controlled radical telomerization using Co(acac)(2)/DMF and had a PDI approximate to 1.3. Poly(vinyl acetate-b-methyl methacrylate-b-dimethylsiloxane-b-methyl methacrylate-b-vinyl acetate) (PMMA-b-PVAc-b-PDMS-b-PVAc-b-PMMA) pentabloblock copolymers provided a method to design the block copolymer with PDMS segments and thus allowing for the adjustments to the flexibility by the PDMS content and a large effect of the softening point (T-g), or rigidity from the methyl methacrylate monomer from the higher melting temperature (T-m). The penta-block copolymers were characterized by H-1-NMR, DSC and GPC. Meanwhile, the number-average molecular weights as determined from the H-1-NMR spectra were in very good agreement with the theoretically calculated values. It can be concluded from the H-1-NMR and DSC data that the pentablock copolymers of PMMA-b-PVAc-b-PDMS-b-PVAc-b-PMMA consisting of a PDMS center block and PMMA and PVAc terminal blocks were synthesized. The reactivity ratio for VAc and MMA monomer pairs was calculated from Mayo-Lewis (r(MMA) = 0.733, r(VAc) = 0.196), Kelen-Todous (r(MMA) = 0.760, r(VAc) = 0.211) and Finemann-Rose (r(MMA) = 0.736, r(VAc) = 0.180).