It is commonly stated that polyacrylonitrile (PAN) and polymethacrylonitrile (PMAN) undergo a cyclization reaction, which may be thermally induced or caused by addition of base to a polymer solution. However, in our previous work with PAN, no evidence for cyclization was found; instead, it was shown that base could abstract the methine proton leading to azomethine crosslinking and gelation. PMAN has no methine proton and hence this crosslinking mechanism should not operate. However, when strong base was added to a PMAN solution, gelation still occurred. It is proposed that base also induces intermolecular nitrile crosslinking reactions. No evidence for cyclization was found in base-treated or thermally treated PMAN. The results of dynamic mechanical testing of thermally discoloured PMAN films were also more consistent with a slight degree of crosslinking rather than extensive cyclization.
Посилання на статтю:
Base-induced gelation of polymethacrylonitrile / Z. Bashir*, E. J. Packer, I. R. Herbert and D. M. Price // Polymer. – 1992. – Vol 33. – P. 373-378.