AbstractCopolymerizations of 2‐vinyl‐l,3‐dioxane (1a), 5,5‐bis(hydroxymethyl)‐2‐vinyl‐1,3‐dioxane (1b), and 5,5‐dimethyl‐2‐vinyl‐1,3‐dioxane (1c) with maleic anhydride (MA) andN‐vinyl‐2‐pyrrolidone (NVP) were investigated. Copolymerization of the cyclic acetals 1 with MA yielded copolymers with perfectly alternating sequences independent of the initial monomer feed composition. Terpolymerization of1a, MA, and styrene, also despite of monomer composition, yielded terpolymers with a molar composition of 50% in MA which confirms the participation of transfer complexes in these copolymerizations. The composition of the1/NVP copolymers (mole fraction)F1(NVP) ≈ 0,6–0,8 also varied little with the feed. The copolymerization rates passed through a maximum when the monomer mixture containe