Binary and ternary copolymerization in the system vinylchloride — maleic anhydride — butadiene

With free radical initiation, the addition of small quantities of butadiene to vinylchloride considerably reduces the rate of polymerization in the initial stages. If maleic anhydride is added as third monomer equimolar to or in molar excess over butadiene, the polymerization rate increases again. The accelerating effect is not due to a DIELS‐ALDER‐reaction between butadiene and maleic anhydride. It results instead from modification of the copolymerization process, most probably in such a way that the retarding growth step is suppressed. Vinylchloride and butadiene, within the range investigated, react in accordance with the rules of conventional free radical copolymerization kinetics. The system butadiene‐maleic anhydride exhibits a strong “tendency toward alternation”. Vinyl chloride and maleic anhydride, on the other hand, except at unsuitable monomer compositions, form copolymers in which vinyl chloride is present in a molar excess. The ternary system behaves accordingly. At suitable monomer compositions, vinyl chloride is incorporated in the polymer chains in molar excess and at a higher partial rate than in the absence of maleic anhydride. Reaction mechanisms are discussed in the light of recent results on Donor‐Acceptor‐complex controlled polymerization as published in the literature.