Alkaline hydrolysis of polyacrylonitrile. On the reaction mechanism

Some new data were obtained about alkaline hydrolysis of a polyacrylonitrile (PAN) suspension at 75°C in a water/ethanol mixture. At >95% conversion of nitrile groups, the hydrolyzed polymer contains ≈20% of amidines situated in the nearest neighborhood of carboxylate groups. After complete hydrolysis of the amidines, poly[(sodium acrylate)-co-acrylamide] is formed having a Bernoulli distribution of units. During the initial stage of PAN cyclization at 25–97°C, very short sequences of conjugated C=N bonds are formed which are much more reactive in hydrolysis than nitrile groups. These data enable us to reconsider the mechanism of alkaline PAN hydrolysis. A corresponding reaction scheme is suggested.