X-Ray Investigations on Poly(Methylsiloxanes) with Mesogenic Side Groups at the Isotropic-Nematic-Smectic-Crystalline Phase Transitions

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Abstract
X-ray investigations have been carried out on Poly (methylsiloxanes) with mesogenic side groups which are attached to the main chain by a flexible spacer of 5 or 6 methylene groups, respectively. The diffraction patterns have been taken on samples placed in a magnetic field between two permanent magnets in the isotropic, nematic, smectic and crystalline state at respective temperatures. In particular, the smectic-crystalline phase transition was studied very carefully. The X-ray diagrams reveal an almost continuous transition from the smectic to the crystalline state. The present investigations support the schematical structural models of the smectic and crystalline state for the same polymers.