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Phase Structure and Phase Transition Mechanism for Light-Induced Ia3d Cubic Phase in 4′‑n‑Docosyloxy-3′-nitrobiphenyl-4-carboxlic acid/Ethyl 4‑(4′‑n‑docosyloxyphenylazo)benzoate Binary Mixture
journal contribution
posted on 2014-04-03, 00:00 authored by Ryo Hori, Yohei Miwa, Katsuhiro Yamamoto, Shoichi KutsumizuThe
light-induced smectic C (SmC) to bicontinuous cubic (Cubbi) phase transition was investigated using grazing-incidence
X-ray diffraction (GI-XRD) and Fourier transform infrared (FT-IR)
spectroscopy to elucidate the mechanism at the molecular level. The
sample was a binary mixture of 4′-n-docosyloxy-3′-nitrobiphenyl-4-carboxylic
acid with an azobenzene derivative having a similar structure. The
GI-XRD analysis revealed that the lattice size of the light-induced
Cubbi phase almost coincides with the extrapolated value
of the thermally induced one to the irradiation temperature. The FT-IR
analysis also showed that the UV irradiation shifts the peak positions
toward their extrapolated wavenumbers that would be displayed by the
thermally induced Cubbi phase at the temperature. These
results indicate that both the molecular state and periodic structure
realized by the irradiation may be regarded as the “postulated”
state and periodic structure of thermally induced Cubbi phase at the temperature. This leads to a conclusion that the trans–cis photoisomerization of
the azobenzene derivatives in the mixture gives rise to destabilization
of the SmC phase with layered structure, alternatively favoring the
formation of the Cubbi phase with a twisted molecular arrangement.