Phase transition induced by two-photon absorption in azobenzene liquid crystals

Light-Driven Liquid Crystalline Materials: From Photo-Induced Phase Transitions and Property Modulations to Applications

“…To circumvent the use of high energy light, recently the possibility of two-photon excitation has been demonstrated to drive the photoinduced phase transition phenomenon in azobenzene derivative containing LC mixtures. 265 This process is particularly appealing since it involves the use of red or infrared light, and localized phase transition can be effected in the system with a high degree of spatial resolution through the two-photon absorption by dispersed azobenzene derivatives. Norikane et al designed and synthesized liquid crystalline macrocyclic compounds 47 and 48 tethered by multiple azobenzenes bearing alkoxy chains (Scheme 19).…”

“…This process undoubtedly involves the use of high energy light radiations to drive the process of phase transition. To circumvent the use of high energy light, recently the possibility of two-photon excitation has been demonstrated to drive the photoinduced phase transition phenomenon in azobenzene derivative containing LC mixtures . This process is particularly appealing since it involves the use of red or infrared light, and localized phase transition can be effected in the system with a high degree of spatial resolution through the two-photon absorption by dispersed azobenzene derivatives.…”

Two-photon absorption and two-photon-induced isomerization of azobenzene compounds

“…In the last few years, there has been a growing interest in using azo compounds in materials science owing to their potential device applications (data storage, optical lters, diffraction elements, ordering layers) based on properties such as photoinduced anisotropy, mass transport and phase transitions. [131][132][133] The light-induced modications of macroscopic properties of AB based materials result mostly from the isomerization process of its molecule. However, the majority of the studies based on the photoinduced geometry change of photochromic motif have been carried out with one-photon excitation, although it has been realized that localized material modulation can be driven in the system with a high degree of spatial resolution through the two-photon induced isomerization.…”

“…24 Thus, while the photoinduced phase transition studies in azo derivative/doped liquid crystals have been carried out mostly with OPE, 134,135 the advantages of TPE for better control of the phase transitions, especially with respect to three-dimensional spatial resolution have been noted. 131 It has been shown that 4-n-heptyl-4-n-propylazobenzene (DAAB-307) can undergo two-photon induced trans-to-cis isomerization and cause nematic-to-isotropic phase transition of an AB LC. 131 A disadvantage of using TPE is, however, that, due to the need for high light intensities which require focused beams, only a very limited volume of a material can be addressed at one time.…”

“…131 It has been shown that 4-n-heptyl-4-n-propylazobenzene (DAAB-307) can undergo two-photon induced trans-to-cis isomerization and cause nematic-to-isotropic phase transition of an AB LC. 131 A disadvantage of using TPE is, however, that, due to the need for high light intensities which require focused beams, only a very limited volume of a material can be addressed at one time. A much studied phenomenon has been light-induced birefringence, sometimes also called orientational hole burning, which is directly associated with photo-orientation of AB motif.…”