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

Poly(dimethylsiloxane) (PDMS) based pentablock copolymers has been synthesized via atom transfer radical polymerization (ATRP) of styrene (St) and vinyl acetate (VAc) telomer at 60 °C in the presence of CuCl/PMDETA as a catalyst system. Vinyl acetate telomer was prepared from controlled radical telomerization with Co(acac)₂/DMF with PDI ≈ 1.3. Poly(vinyl acetate-b-styrene-b- dimethylsiloxane- b- styrene-b-vinyl acetate) (PVAc-b-PSt-b-PDMS-b-PSt-b-PVAc) pentablock copolymers provided a method to design block copolymer with PDMS segment, allowing us for the adjustments in the flexibility by PDMS with a large effect from its softening point (T_g), or rigidity of styrene monomer and a higher melting temperature (T_m). Penta-block copolymers were characterized by FTIR, ¹HNMR, DSC, and GPC techniques. Meanwhile, the number-average molecular weights calculated from ¹HNMR spectra were in very good agreement with the theoretically calculated value. It could be concluded from the ¹HNMR and DSC spectrum that the pentablock copolymers of PVAc-b-PSt-b-PDMS-b-PSt-b-PVAc consisting of a PDMS center block and PSt and PVAc terminal blocks were synthesized.