Radical (Co)polymerization of Vinyl Chloroacetate andN-Vinylpyrrolidone Mediated by Bis(acetylacetonate)cobalt Derivatives

The effect of the electron-withdrawing groups on the ligand in a series of bis(acetylacetonate)cobalt(II) derivatives, Co(R 1 COCH COR 2 ) 2 (R 1 = R 2 = CH 3 ( 1 ), R 1 = CF 3, R 2 = CH 3 ( 2 ), R 1 = R 2 = CF 3 ( 3 )), was examined by conducting a controlled radical polymerization of vinyl chloroacetate (VClOAc) and N -vinyl-2-pyrrolidone (NVP) under the same reaction conditions. Complex 2 provided better control over the polymerization of VClOAc than complex 1, resulting in the preparation of a poly(VClOAc) with M n closer to the theoretical M n and lower polydispersity at the same monomer conversion. On the other hand, complex 3 was not able to control the radical polymerization of VClOAc. In the case of NVP, only complex 1 produced poly(NVP) with relatively low polydispersity (1.7−2.0). Better control over M n and polydispersity in the polymerization of VClOAc and NVP was achieved by addition of vinyl acetate (VOAc) to the reaction. The M n / M n,th and polydispersity of the copolymers became lower as the initial proportion of VOAc in both copolymerization systems was increased. The VOAc content of the poly(VClOAc- co -VOAc) and poly(NVP- co -VOAc) copolymers calculated from 1 H NMR spectra were in good agreement with the values calculated from monomer reactivity ratios.