Structure–property relationships of ‘diluted’ ferroelectric polysiloxanes
作者:
Holger Poths,
Rudolf Zentel,
期刊:
Liquid Crystals
(Taylor Available online 1994)
卷期:
Volume 16,
issue 5
页码: 749-767
ISSN:0267-8292
年代: 1994
DOI:10.1080/02678299408027848
出版商: Taylor & Francis Group
数据来源: Taylor
摘要:
A series of new ferroelectric copolysiloxanes with systematically varied comonomer content (‘dilution’) has been synthesized. Good planar alignment could be achieved for all copolysiloxanes and they were studied with respect to their mesomorphic and ferroelectric properties. Broad enantiotropic S*Cphases and spontaneous polarizations up to 286 nC cm−2are found. X-ray diffraction experiments show a linear increase of the smectic layer spacing by ‘dilution’. This points to a microphase separated structure of mesogenic groups and siloxane chains. It is found that the fixation of a mesogen to homopolysiloxane leads to an increase ofPs, whereas the ‘dilution’ of the mesogens with dimethylsiloxane units decreasesPsagain. Based on the microphase separated model, it can be shown that the decrease ofPsis not only due to the decrease of the vol % of mesogenic groups. The coupling between different mesogens mediated by the polymer chain, has additionally to be taken into consideration. A remarkable drop in the response times τ with decreasing mesogen content is confirmed and switching times less than 1 ms were measured.
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