Polymerisation via macrozwitterions, 2. Ethyl and butyl cyanoacrylates polymerised by pyridine and polyvinylpyridine

Anionic polymerisations of ethyl and butyl cyanoacrylates in THF initiated by pyridine and polyvinylpyridine were studied between 42 and −95°C. The polymers showed the UV absorption of quaternised pyridine, indicating that they had grown as macrozwitterions. Pyridine consumption was very low (few %) and the polymer molecular weights high (3 · 105 – 106) irrespective of reaction conditions. Overall rates increased as reaction temperature was reduced, approaching those found in phosphine‐initiated polymerisations by −78°C. At 20°C the kinetics were complex, e.g. sigmoid conversion curves which reached an internal first order, yet showing apparent 2nd order external order. A qualitative kinetic interpretation is given, postulating absence of intrinsic termination processes, and a complex initiation process involving (exothermic) equilibrium formation of a precursor betaine. Polyvinylpyridine initiates graft copolymers; but only in presence of chain‐terminating agents, e.g. acids, lactones or sultones, can the grafted side chains be kept short, and their number raised towards the potentially complete grafting of all pyridine groups.