STUDIES OF POLYMERS AND POLYMERIZATION: II. THE PYROLYSIS OF POLYINDENES AND THE POLYMERIZATION OF DIINDENE

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Abstract
On heating samples of polyindene to temperatures below those necessary to effect pyrolytic distillation, they suffer cracking, as evidenced by a fall in molecular weight. Such cracking takes place the more readily, the higher the molecular weight of the sample taken. On subjecting polyindene to slow pyrolytic distillation at 2 mm. up to bath temperatures of 400 °C., there is obtained a distillate containing indene, diindene and triindene. The residue consists of low polymers. Under these conditions cracking is more profound, i.e., the amount of distillate is larger, in the case of a polyindene of high molecular weight than in the case of one of relatively low molecular weight. On pyrolytic distillation at ordinary pressure, diindene yielded 74% of indene. Diindene can be polymerized by sulphuric acid, by antimony pentachloride and by heat. A mixture of mono- and di-indene yields triindene, when heated. It is concluded that the results accord better with the authors' formula for the polyindenes rather than with Staudinger's ring formula. In the author's view the polyindenes are open-chain compounds which owe their formation to a series of addition reactions involving the wandering of hydrogen, and, conversely, that their pyrolysis is a cracking reaction also involving wandering of hydrogen.

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