Block polymerizations with trapped radicals

Abstract Polymers prepared in heterogeneous medium can be used for the synthesis of block polymers, if they contain trapped radicals. With polyacrylonitrile the molar content of second monomer (vinyl acetate, vinylidene chloride, styrene, acrylamide) is low and inferior to 5%, except with methyl methacrylate (9%), acrylic acid (16%), methyl acrylate (14,3%) and acrylonitrile itself (∼36%). In this last case, the addition of monomer causes an appreciable increase of the highest molecular fraction. With polyacrylamide the incorporation of second monomer is low and exceeds not 8 mole % with acrylonitrile and acrylic acid. Finally in the case of polyvinyl chloride no block polymerization could be detected. The block polymers described in this paper have been purified from the homopolymers by selective extraction or by fractionated precipitation.