Mesophase Behavior and Structure of Mesophases in Cyclolinear Polyorganosiloxanes

摘要

The phase behavior and structure of the mesophases in cyclolinear polyorganosiloxanes (POCS) with siloxane cycles of various dimensions bonded either by only oxygen atoms or by flexible spacers is considered. It is shown that the 2D-columnar ordering in the mesophase is not typical for all POCS. Formation of a novel mesophase with ID-order has been discovered for a series of POCS containing cyclohexasiloxane chain fragments substituted with methyl groups (PMCS-6). The most probable arrangement of the PMCS-6 molecules in the mesophase is a layer packing formed by monomolecular layers stacked with good long-range order. Within a layer the cyclohexasiloxane fragments are arranged with a strong tendency to lie on their flat sides along the planes of the layer. The inertlayer periodicity being connected with the cyclohexasiloxane thickness only is completly non-sensitive to the chemical structure of PMCS-6. The temperature region of 1D-mesophase existence, however, can be directly regulated by the chemical structure of PMCS-6.