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

Abstract

The effect of the electron-withdrawing groups on the ligand in a series of bis(acetylacetonate)-cobalt(II) derivatives, Co(R 1 COCHdCOR 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.

Living Radical Polymerization by the RAFT Process - A Second Update

“…[74][75][76] A reversible coupling mechanism is generally proposed for polymerizations in the presence of bis(acetylacetonate)cobalt(ii) complexes. The process has been applied to VAc miniemulsion polymerization [77] and in the synthesis of poly(vinyl acetate)-block-poly(vinyl pyrrolidone) (PVAc-b-PNVP) [78,79] and PVAc-b-PSt. [80] Cobalt-mediated St polymerization is not believed to involve a reversible deactivation mechanism but rather is believed to be a conventional polymerization initiated by the PVAc organocobalt species.…”

Radical Polymerization of Vinyl Acetate with Bis(tetramethylheptadionato)cobalt(II): Coexistence of Three Different Mechanisms

“…The fluorinated analogues [Co-A C H T U N G T R E N N U N G (acac-F 3 )] (2; acac-F 3 = 1,1,1-trifluoropenta-2,4-dionato) and [CoA C H T U N G T R E N N U N G (acac-F 6 ) 2 ] (3; acac-F 6 = 1,1,1,5,5,5-hexafluoropenta-2,4-dionato) were investigated by Matyjaszewski et al for VAc and related monomers. [23,24] Whereas compound 2 exerts a level of control comparable to that of 1, compound 3 yields higher molecular weights and higher polydispersities.…”

Mechanistic Insights into the Cobalt‐Mediated Radical Polymerization (CMRP) of Vinyl Acetate with Cobalt(III) Adducts as Initiators

“…[28] This technique, known as cobalt-mediated radical polymerization (CMRP), allows poly(vinyl acetate) (PVAc) and poly(vinyl alcohol) (PVOH, merely upon hydrolysis) to be synthesized with a predetermined molecular weight, and to be constitutive components of block copolymers, which are very difficult to obtain by other techniques. [29][30][31][32] Well-defined statistical copolymers [33,34] could also be prepared and fullerene was successfully grafted by PVAc and PVOH. [35] Until recently, CMRP was explained by a reversible termination mechanism based on the homolytic cleavage of the terminal CoÀC bond.…”