AbstractStyrene/1‐hexene copolymers of different chemical composition were prepared with a classical isospecific Ziegler‐Natta catalyst, TiCl3(H)‐AlEt3. Their structure and the distribution of the monomeric unites was analyzed by GPC double detection and1H and13C NMR. The chemical arrangement of isolated and blocked styrene monomeric units between sequences of hexene monomeric units was also investigated.13C chemical shifts of carbon atoms in the copolymers and in addition in model molecules of the two modes of styrene addition indicate that styrene insertion into carbon‐metal bonds of the catalyst proceeds according to a primary mode. Mechanistic implications of these results are di