The incorporation of aroyloxy radicals in polymer molecules

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Abstract
Initiation of the bulk polymerization of samples of 2‐vinylpyridine with N‐nitroso‐N‐phenyl‐m‐bromobenzamide and N‐nitroso‐p‐bromoacetanilide gave polymers containing 0.06% and 0.52% bromine, respectively. Therefore, the aroyloxy radical is only about one‐eight as reactive as the aryl radical for incorporation in a polymer molecule. This is a rough comparison, for there is no data upon which to base an estimate of the influence of the halogen substituent upon the reactivity of the parent free radicals. The purification of the polymers included an ether extraction of an acid solution of the substances to insure removal of all initiator fragments not attached to the polymer molecules. The presence of aroyloxy radicals in the polymers does not give assurance, however, that they were introduced in the step of chain initiation or even in the original polymerization process. For example, treatment of polystyrene with p‐chlorobenzoyl peroxide was found to introduce 0.60% chlorine which through saponification proved to be a minimum of 96% chlorobenzoyloxy groups. Therefore, it seems highly probable that, when nitrosoamides are used as catalysts, aryl radicals may serve exclusively as chain initiators while a much smaller quantity of aroyloxy groups are incorporated by other mechanisms.

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