Oligo-and polysiloxanes with pendant oxadiazole groups

3 Oligo and polysiloxanes with pendant oxadiazole groups 

The next step was the synthesis of liquid crystalline polysiloxanes with oxadiazole groups in the mesogenic unit. The polymers were prepared by a polymeranalogous reaction of the monomers 10 and 11 with poly(hydrogenmethylsiloxane) 15. 

Both polymers are liquid crystalline. The transition into the isotropic phase takes place at about 200 °C and therefore at a much higher temperature than in the monomers. The high clearing temperature makes the orientation of the polymers difficult which is preferably carried out near the clearing point. Up to now it was not possible to prepare well-defined polymers with the monomers 12-14. A possible reason is the inactivation of the Pt catalyst by the amino groups. 

If the cyclic tetrasiloxane 18, which is commercially available in high purity, is used instead of 15, well-defined monodisperse model compounds are obtained [9]. These com- 

So the monomeric compounds 10 and 12-14 have been reacted with 18 to yield the following tetrameric derivatives  

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