Cyanoxyl-mediated free-radical polymerization of acrylic acid: Its scope and limitations

This work examines the scope and limitations of the cyanoxyl (OC≡N)-mediated free-radical polymerization of acrylic acid (AA) with respect to the criteria of livingness. Cyanoxyl persistent radicals were generated in situ through the reaction between arenediazonium salts (X - C ₆H₄N≡N^⊕BF₄ ^Θ, where X is H, OCH₃, Cl, or NO₂) and sodium cyanate (NaOCN). This article thoroughly discusses the role played by such oxygen-centered radicals in the polymerization process; it particularly focuses on the influence of the concentration and nature of the diazonium salt, the solvent, and the temperature on features such as the variations of ln([M]_o/[M]) versus time (where [M]₀ is the initial monomer concentration and [M] is the monomer concentration), the number-average molar mass versus conversion, and the polydispersity versus conversion in cyanoxyl-mediated free-radical polymerizations of AA. Cyanoxyl-terminated samples were used as macroinitiators for the polymerization of methyl methacrylate to generate poly(acrylic acid)-b-poly(methyl methacrylate) block copolymers.