Poly silanes mesophase

In conclusion, the phase behavior of symmetrically di-n-alkyl-substituted poly(silane)s and poly(silylenemethylene)s is similar both classes of polymers form the same type of mesophase, although it cannot be obtained in pure form for the poly(silylenemethylene) studied. The mobility in the mesophase, characterized by the quadmpole splitting, appears to depend strongly on the chemical structure of the backbone. For different poly(silane)s, the mobility in the crystalline phase is obviously influenced by the conformation of the backbone zW-trans vs. 73-helical) and therefore depends on the length of the side-chains. Application of pressure to poly(silane)s with 73-helical backbones leads to the formation of high-pressure crystalline modifications with dA -trans backbone conformation. The pVT studies made it possible to define the precise conditions for the pressure-induced phase transitions. 

Fig. 6.8 Crystal to mesophase transition temperatures plotted as a function of the number of carbon atoms, p, in the alkyl group in poly(dialkyl silanes). (From Weber et al. (174))...

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