Carboxylic acids as latent initiators of radical polymerization carried out in the presence of hypervalent iodine compounds: synthesis of branched and transiently crosslinked polymers

Abstract

The acetoxy groups in (diacetoxyiodo)benzene, PhI(OAc)₂, can exchange with methacrylic acid in various solvents yielding [(acetoxy methacryloyloxy)iodo]benzene or (dimethacryloyloxyiodo)benzene. The last two hypervalent iodine compounds can serve as inimers due to the presence of polymerizable moiety and the easy generation of radicals upon thermal or light-induced homolysis of the I–O bonds. PhI(OAc)₂ was added to mixtures of methacrylic acid and methyl methacrylate, and upon heating to 80 °C, branched or transiently crosslinked polymers were formed. In homopolymerizations of methyl methacrylate initiated by PhI(OAc)₂, i.e., in the absence of the monomer with carboxylic acid group, no branching or gelation was observed.