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Study of unsymmetrical dimesogens containing 4‐heptylazobenzene
Author(s) -
Mallia V. Ajay,
Funahashi Masahiro,
Tamaoki Nobuyuki
Publication year - 2007
Publication title -
journal of physical organic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.325
H-Index - 66
eISSN - 1099-1395
pISSN - 0894-3230
DOI - 10.1002/poc.1231
Subject(s) - moiety , chemistry , methylene , stereochemistry , phase (matter) , crystallography , medicinal chemistry , organic chemistry
4‐Heptylazobenzene (HAB) has been covalently attached to cholesterol (Ch) by varying the methylene spacers and to cyanobiphenyl (CB) moiety with an octyl methylene linkage. Enhancement of short‐range translational correlations in the chiral nematic (N*) phase has been observed by the introduction of HAB moiety. HAB–Ch dimesogens exhibit chiral smectic C (SmC*), chiral smectic A (SmA*) and N* phases depending on the methylene spacer length. The dimesogen containing HAB–CB shows a SmA and an N phase. The HAB–Ch dimesogen with octyl methylene spacer shows co‐existence of multiple periodicities in its SmA* as well as in SmC* phases. A dramatic increase of >150 nm in the N* reflected wavelength shift (Δ λ ) with change in temperature has been observed for the HAB‐Ch dimesogen containing an octyl spacer compared to the similar dimesogen that does not have a heptyl side chain. Ferroelectric switching has been studied for a representative dimesogen containing HAB‐Ch having hexyl spacer in its SmC* phase, the spontaneous polarization value was determined to be 150 nC cm −2 (at 125 °C) by applying a triangular wave field. A reversible photochemical switching between SmA and N phases also has been reported for the dimesogen containing HAB–CB. Copyright © 2007 John Wiley & Sons, Ltd.