Amphiphilic Poly(vinyl acetate)-<i>b</i>-poly(<i>N</i>-vinylpyrrolidone) and Novel\nDouble Hydrophilic Poly(vinyl alcohol)-<i>b</i>-poly(<i>N</i>-vinylpyrrolidone)\nBlock Copolymers Prepared by Cobalt-Mediated Radical\nPolymerization

Abstract

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