Dynamics of Photochemical Phase Transition of Guest/Host Liquid Crystals with an Azobenzene Derivative as a Photoresponsive Chromophore

Abstract

The dynamics of the photochemical phase transition process of guest/host liquid crystals (LCs) containing an azobenzene derivative as a photosensitive chromophore was studied. We proposed a model for the photochemical phase transition of the guest/host LCs and simulated the change in transmittance through LCs due to the phase transition on the basis of this model. Upon irradiation at 366 nm, the cis isomer was generated randomly in the irradiated site, and then the transmittance of the probe light was slightly decreased because of the disturbance of the alignment of the nematic (N) phase by the cis isomers. Upon further irradiation, the N-to-isotropic (I) phase transition took place in local domains, and the transmittance of the probe light decreased with the growth of these local I domains. In the simulations, three factors were found to affect significantly the dynamics of the photochemical phase transition and the change in transmittance of light: the number of I domains formed by irradiation, the growth rate of the I domains, and the threshold size of the I domains detected with the probe light.

Multiresponsive self-assembled liquid crystals with azobenzene groups

“…The change of the texture under irradiation indicates a trans-cis-isomerization of A in the liquidcrystalline phase, resulting in the mesophase transformation from a column phase to a more disordered nematic phase. However, the isotropic phase was not observed in our temperature range by photoisomerization as reported by Ikeda and co-workers [26]. When the UV light was removed from the sample at 95 • C for 10 min in the dark, the texture was still maintained.…”

“…Self-assembly materials containing azo linkages have attracted tremendous attention because of their light-induced photo-switchable and elastic properties [23][24][25][26][27][28][29][30][31][32]. However, in most cases, the liquid-crystalline phase of azobenzene compound transferred to the isotropic phase on irradiation because of the unstabilization of the liquid-crystalline phase by cis-azobenzene [11][12][13][14][15][16][17]26]. It is still a great challenge to control the liquid-crystalline phase from one stable texture to the other by irradiation, which has been reported in liquid-crystalline diarylethene compounds [33,34].…”

Photoisomerization-induced morphology and transparency transition in an azobenzene based two-component organogel system

“…4f). The photo-induced texture change in GA-PAP was possibly due to the difference in the molecular aggregation state before and after UV irradiation [33].…”

Liquid Crystals into Planar Photonic Crystals

“…In particular, we observe that, in spite of a large amount of research on LC infiltrated PhCs, little has been done on their optical tuning (Maune et al, 2005), even though all-optical switching plays a very important role in the optical communication field (Asakawa et al, 2006) and, as we have briefly discussed above, several other approaches have already been explored to optically tune planar PhCs (Ndi et al, 2005;Raineri et al, 2005;Teo et al, 2006;Tanabe et al, 2007). Here, we will illustrate how it is possible to optically tune the response of planar PhC devices by infiltration with a photo-responsive LC blend doped with azobenzene photochromic molecules (Legge & Mitchell, 1992;Sung et al, 2002;Ikeda, 2003).…”