A new class of block polymers

The reaction of industrially available “prepolymers,” containing one or several isocyanate groups per chain, with tert ‐butyl hydroperoxide yielded long‐chain peroxycarbamates. These were found able to initiate the polymerization of a wide variety of vinyl monomers as well as dienes leading to a new class of block polymers of very interesting physical properties. Polyether and polyester “prepolymers” with one, two, or three isocyanate functionalities were linked chemically to polystyrene, polymethyl methacrylate, poly‐ n ‐butyl acrylate, polyarylonitrile, and polyisoprene. The formation of block polymers was proved by both physical and chemical methods. Their mechanical properties were illustrated by means of torsional modulus–temperature curves. The effect of varying composition and of a crosslinking agent on the elastic modulus was examined. Tentative reaction mechanisms were also presented.