Block copolymers by radical polymerization 3. Block copolymers of styrene, methyl acrylate, n-methyl-n-vinylacetamide, 1-vinyl-2-pyrrolidone

A polyazoinitiator obtained from 2,2′‐azoisobutyronitrile (AIBN) and a diol is used to prepare block copolymers according to the Smets procedure. Partial decomposition of the polyazoinitiator in presence of a monomer results in an azogroup‐containing prepolymer. Block copolymers are obtained decomposing the remaining azo groups in presence of a second monomer. Examples investigated are styrene/methyl acrylate, styrene/N‐methyl‐N‐vinylacetamide, methyl acrylate/N‐methyl‐N‐vinylacetamide, 1‐vinyl‐2‐pyrrolidone/acrylonitrile. Homopolymers are produced simultaneously. Up to 70% of block copolymers are formed in these reactions. Block copolymers of styrene/methyl acrylate have hard/soft segmented molecules. It is an elastic material with spherical, cylindrical and lamellar, resp. domain structures, depending on the composition.