CYCLIZATION KINETICS OF POLY(ACRYLONITRILE)

Experimental studies of poly(acrylonitrile) (PAN) homopolymer and itac onic acid co-polymer stabilization examine the impact of polymer compo sition, temperature and reaction environment on the rate of cyclizatio n. Stabilization of homopolymer PAN in nitrogen, 10.5 and 21% oxygen p roduces sigmoidally shaped curves when extent of cyclization is plotte d as a function of reaction time. The length of the initial induction period in the sigmoidally shaped homopolymer curves decreases with inc reasing temperature and when oxygen is present in the reaction environ ment. Go-polymer cyclization curves also exhibit an induction period w hen reacted in nitrogen, but the period is less distinct than in the h omopolymer case. The length of the induction period in the co-polymer data decreases with increasing temperature and increasing acid concent ration. In the presence of oxygen, no induction period is present in a ny of the acidic co-polymer data. Reactions in 10.5 or 21% oxygen resu lt in retardation of PAN homopolpmer and co-polymer cyclization relati ve to reaction in a nitrogen environment. The retarding effect of oxyg en is minimized as the acid concentration in the polymer is increased. Copyright (C) 1996 Elsevier Science Ltd