Untersuchungen über die verfärbung von polyacrylnitril. IV. Polymeranaloge umsetzungen an durch erhitzung verfärbtem polyacrylnitril

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Abstract
Ultraviolet and infrared spectroscopy indicated that the primary discoloration of polyacrylonitrile during heating was due to the formation of conjugated carbon double bonds. This conclusion was supported by hydrolysis experiments. In the polyacrylic acid obtained from polyacrylonitrile after heat treatment the C°C stretching band could not be observed in the infrared spectrum because of the wide carbonyl band; therefore poly(allyl alcohol) was prepared from the acrylic acid via poly(methyl acrylate). In the infrared spectrum of this deeply colored polymer a carbon‐carbon double bond frequency was found. Oxidative cleavage of the poly(acrylic acid) obtained from heat‐treated and discolored poly(acrylic acid) by KMnO4 yielded an amount of CO2 increasing with increasing discoloration of the polymer. This supports the presence of conjugated carbon double bonds in the poly(acrylic acid). On the basis of the reactions carried out on the polymers in this work the assumption seems justified that the primary discoloration of polyacrylonitrile is due to formation of a system of conjugated double bonds in the carbon chain rather than to hydrogenated naphthyridine rings.

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