An X-Ray Study of Some Synthetic Elastomers. Polychloroprenes

Abstract Synthetic rubbers prepared from isoprene and other unsaturated hydrocarbons have been studied by means of x-rays by various investigators, including Carothers, Katz, Meyer, and Sebrell and Dinsmore. In general, these synthetic products differ markedly from natural rubber in that when they are stretched, they do not give any fibre diagrams. On the contrary, μ-polychloroprene (Neoprene), H 2 C:CC·CH:CH 2 , when stretched to about 500 per cent, gives a somewhat diffused fibre diagram with an identity period of 4.8 A˚.U., corresponding to the length of a chloroprene unit in the trans form. We have verified this fact, and have found, in addition, that preliminary heating of the polychloroprene facilitates this orientation process which takes place upon stretching. The investigation was continued by a study of a product which had not previously been studied, viz. , chloroisoprene: