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Phase Biaxility in Smectic-A Side-Chain Liquid Crystalline Elastomers

✍ Scribed by Rebekka Storz; Ansgar Komp; Anke Hoffmann; Heino Finkelmann

Publisher
John Wiley and Sons
Year
2009
Tongue
English
Weight
377 KB
Volume
30
Category
Article
ISSN
1022-1336

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✦ Synopsis

Abstract

^2^H NMR investigations on the biaxial phase behavior of smectic‐A liquid crystalline side‐chain elastomers are presented. Biaxiality parameters were determined by measuring the quadrupolar splitting of two spin probes, namely benzene‐d~6~ and hexamethylbenzene‐d~18~, at various angles between the principal director and the external magnetic field: while for a uniaxial sample the angular dependence can be described by the second Legendre polynomial, an additional asymmetric term needs to be included to fit the data of the two investigated biaxial systems. Two elastomers synthesized from mesogens that differ in the molecular geometry in order to study the molecular origin of biaxiality were compared. Biaxiality is observed for both elastomers when approaching the glass transition, suggesting that the network dynamics dominate the formation of the biaxial phase.

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