Synthesis and characterization of PSt-b-PVAc diblock copolymers via combination of atom transfer radical polymerization and cobalt-mediated radical polymerization

摘要

Atom transfer radical polymerization (ATRP) of styrene (St) initiated with trichloromethyl-terminated poly(vinyl acetate) was performed in the presence of CuCl/PMDETA as a catalyst system at 60 C. PVAc-CCl_3 telomers prepared from radical telomerization (without catalyst) and controlled radical telomerization (in the presence of Co(acac)2/DMF), were used in atom transfer radical polymerization (ATRP) to synthesize polystyrene-b-poly(vinyl acetate) (PSt-b-PVAc) diblock copolymers. The PVAc based block copolymers revealed a significant effect of Co(acac)_2/DMF on PVAc macroinitiator which was used in the synthesis of highly ordered diblock copolymer on a well-defined microstructure. Diblock copolymers were characterized by ~1H-NMR, DSC and GPC techniques. Reactivity ratios of St and VAc were calculated by the Mayo-Lewis (r_(St) = 0.563, r_(VAc) = 0.081), Kelen-Todous (r_(St) = 0.583, r_(VAc) = 0.074) and Finemann-Rose(r_(St) = 0.569, r_(VAc) = 0.090) methods, which are in a good agreement with those reported for the conventional free-radical copolymerization of St and VAc. The number average molecular weights calculated from ~1HNMR spectra were in good agreement with theoretically calculated values for block copolymers.