Polyacrylonitrile turned biodegradable by incorporation of N-benzyl-4-vinylpyridinium chloride (BVP), a highly biodegradable chemical structure, into the main chain. Oligomers of acrylonitrile are biodegradable dissimilar to polyacrylonitrile, and connection of them by BVP produced biodegradable polymers. The half-life of a copolymer of acrylonitrile with BVP (PAN-co-BVP) in a molar ratio of 97 : 3 was 21 days when treated with activated sludge in soil. The average number of acrylonitrile units in the oligo-acrylonitrile portion was 32. Degradation at the BVP portion appeared predominant, but the oligo-acrylonitrile portion also underwent exhaustive degradation when the portion was sufficiently short. Even though biodegradable, oligo-acrylonitriles are not useful as polymeric materials, but connection of them by BVP produces useful polymeric materials possessed of sufficient biodegradability. Such bridged polymer is different from conventional polyacrylonitrile, and its utility may be different to some extent, but it possesses sufficient biodegradability. (c) 2005 Wiley Periodicals, Inc.