Synthesis and Characterization of PSt-b-PDMS-b-PVAc-b-PDMS-b-PSt pentablock copolymers by ATRP initiated by PVAc telomers from bulk telomerization in the presence of Co(acac)2

Atom transfer radical copolymerization of St and PDMS starting with trichloromethyl-terminated PVAc macroinitiator was performed at 60°C in the presence of CuCl/PMDETA as a catalyst system. Well-defined PSt-b-PVAc-b-PSt and PSt-b-PDMS-b-PVAc-b-PDMS-b-PSt block copolymers were successfully synthesized through ATRP initiated with PVAc telomers (from bulk telomerization with and without Co(acac)2 as the catalyst). Triblock and penta-block copolymers were characterized by FTIR, 1H-NMR, DSC and GPC techniques. GPC results demonstrated that tri-block and penta-block copolymers, which were initiated by PVAc telomers from bulk telomerization with Co(acac)2, show smaller polydispersity indices than those initiated without Co(acac)2. GPC results have also revealed a linear dependence of the number-average molecular weight on the PDMS concentration as well as small polydispersity indices for the synthesized block copolymers. Meanwhile, the number average molecular weights calculated from 1HNMR spectra were in very good agreement with the theoretically calculated value.

Keywords:

ATRP , PVAc , PDMS , Polystyrene , block copolymers