Strain-induced changes of the X-ray diffraction patterns of cross-linked Poly (dimethylsiloxane): The texture hypothesis

Poly(dimethylsiloxane) is a widely used silicone polymer that undergoes partial crystallization both as free oil and rubber when sufficiently cooled. However, a description of its crystalline structure surprisingly remains a totally open question. In particular X-ray diffraction fiber patterns of stretched silicone rubbers display impressive changes with strain and a recently proposed explanation involves a rich polymorphism. The present study develops the different idea that the X-ray pattern evolution merely reflects changes in the crystalline texture: a single crystalline phase is present with a structure virtually unaffected by strain while the axis of preferential orientation for the crystallites progressively changes. This enables a quantitative description of the X-ray fiber patterns, but the remaining fundamental structural issues are underlined.