Amphiphilic Poly(vinyl acetate)-b-poly(N-vinylpyrrolidone) and Novel Double Hydrophilic Poly(vinyl alcohol)-b-poly(N-vinylpyrrolidone) Block Copolymers Prepared by Cobalt-Mediated Radical Polymerization

Well-defined amphiphilic block copolymers of poly(vinyl acetate) (PVAc) and poly( N -vinylpyrrolidone) (P N VP) were synthesized by cobalt-mediated radical polymerization (CMRP). The N VP polymerization initiated by poly(vinyl acetate) end-capped by the cobalt(II)acetylacetonate complex met the criteria of controlled polymerization, i.e., first-order kinetic in N VP, increase of the molar mass with the N VP conversion, and narrow molar mass distribution. Therefore, the length of the two blocks can be tuned by the [VAc]/[Co(acac) 2 ] and the [ N VP]/[PVAc] ratios for the synthesis of the macroinitiator and the polymerization of the second monomer, respectively. These amphiphilic PVAc- b -P N VP block copolymers were easily converted into the double hydrophilic PVOH- b -P N VP counterparts by selective methanolysis of the PVAc block. These two types of copolymers were prone to self-association into micelles in appropriate solvents.