Polymer and Materials Science
Wiley InterScience Backfile Collection 1832-2000
Chemistry and Pharmacology
The structure of the ionically chlorinated polystyrenes has been investigated by both chemical and infrared spectrometric analyses. The chlorination reaction, performed in the total darkness and in the presence of iodine as catalyst, proceeds only by a substitution mechanism, both in the aromatic nucleus and in the main polymeric chain. The catalyst concentration exercises a determining effect on the over-all rate of the reaction. The aliphatic chlorine content has been determined by reaction with aniline; indeed preliminary experiments have shown that the aromatic chlorinated isomer has been determined by infrared quantitative spectrometry, by comparison with reference polymers: polystyrene, poly-para- and poly-ortho-chlorostyrenes, poly-3,4-, -2,4-, -2,5-, and -2,6- dichlorostyrenes. The chlorine is preferentially oriented in the para, secondarily in the ortho position. From about 37% total chlorine content, nearly all the phenyl groups have reacted and the amount of para- and ortho-chloro units decreases rapidly in favor of dichlorophenyl units. Some evidence is found of a trichloro substitution in samples of about 41% Cl or more. To elucidate the problem of the dichlorophenyl units, some samples of poly-para- and poly-ortho-chlorostyrenes were also chlorinated: the second chlorine atom is directed into the phenyl ring mainly in the 3 position for poly-para-chlorostyrene, and in the 5 position for poly-ortho-chlorostyrene. However, a certain amount of the 2,4-isomer is also obtained in both cases. By adding the amount of halogen (calculated from infrared analysis) to the aliphatic chlorine content (obtained from aniline analysis), a value has been found which agrees with the total chlorine content determined by the method of Wurzschmitt. The decrease of the degree of polymerization, due to the chlorination, has been followed by osmotic measurements and found to be favored by both a high degree of substitution and a polar character of the catalyst.
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