Optical Switching and Image Storage by Means of Azobenzene Liquid-Crystal Films

Ikeda, Tomiki; Tsutsumi, Osamu

doi:10.1126/science.268.5219.1873

Cited by 1,506 publications

(926 citation statements)

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“…[19][20][21] The ability of azobenzene photoisomerization to generate anisotropic dimension change and motion in LC networks typically results from increased molecular disorder caused by bent cis-azobenzene relative to networks with rod-like transazobenzene. Such photocontrol of order/disorder has been used to induce rapid nematic-to-isotropic phase transitions in LC films for applications in optical image storage [22] and holography. [23] The reversibility of azobenzene photoisomerization is beneficial for such applications, and the ability of azobenzene materials to undergo many trans-cis photoisomerization cycles without noticeable degradation in performance has been demonstrated.…”

mentioning

confidence: 99%

Photoswitchable Nanomaterials Based on Hierarchically Organized Siloxane Oligomers

Zha

Vantomme

Berrocal

et al. 2017

Adv Funct Materials

102

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Materials with highly ordered molecular arrangements have the capacity to display unique properties derived from their nanoscale structure. Here, the synthesis and characterization of azobenzene (AZO)-functionalized siloxane oligomers of discrete length that form photoswitchable supramolecular materials are described. Specifically, synergy between phase segregation and azobenzene crystallization leads to the self-assembly of an exfoliated 2D crystal that becomes isotropic upon photoisomerization with UV light. Consequently, the material undergoes a rapid athermal solid-to-liquid transition which can be reversed using blue light due to the unexpectedly fast 2D crystallization that is facilitated by phase segregation. In contrast, enabling telechelic supramolecular polymerization through hydrogen bonding inhibits azobenzene crystallization, and nanostructured pastes with well-ordered morphologies are obtained based on phase segregation alone, thus demonstrating block copolymer-like behavior. Therefore, by tailoring the balance of self-assembly forces in the azobenzene-functionalized siloxane oligomers, fast and reversible phase-changing materials can be engineered with various mechanical properties for applications in photolithography or switchable adhesion to lubricant properties. In these materials, contraction along the LC director occurs with isomerization of the planar trans-azobenzenes to the bent cis-azobenzenes. By limiting the depth of photoactivity, generally through utilizing the inherently high absorption coefficient of the azobenzenes, this contraction can give rise to anisotropic bending in poly mer films, [7,8] gels, [9] fibers, [10][11][12] and even crystals. [13] Different modes of motion arise with more complex molecular arrangements. For example, expansion of chiral nematic LCs along the helical axis has been utilized to create polymer coatings with photoswitchable topologies [14][15][16][17] and polymer films with macroscopic helical motion. [18] Additionally, polymer films with splay-bend configuration, in which LC-mesogens gradually change orientation throughout the film cross-section, have shown to exhibit inherently anisotropic bending as well as achieve significantly faster and larger bending when compared to uniaxially aligned films. [19][20][21] The ability of azobenzene photoisomerization to generate anisotropic dimension change and motion in LC networks typically results from increased molecular disorder caused by bent cis-azobenzene relative to networks with rod-like transazobenzene. Such photocontrol of order/disorder has been used to induce rapid nematic-to-isotropic phase transitions in LC films for applications in optical image storage [22] and holography. [23] The reversibility of azobenzene photoisomerization is beneficial for such applications, and the ability of azobenzene materials to undergo many trans-cis photoisomerization cycles without noticeable degradation in performance has been demonstrated. [24,25] Furthermore, few examples have demonstrated the photocontrolled swit...

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mentioning

confidence: 99%

Photoswitchable Nanomaterials Based on Hierarchically Organized Siloxane Oligomers

Zha

Vantomme

Berrocal

et al. 2017

Adv Funct Materials

102

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“…Photoinduced molecular isomerization in azobenzene derivatives has been extensively utilized to modulate the magnitude of order parameter in liquid‐crystalline system, resulting in the perturbation of molecular alignment and even phase transition, thus opening the door for optical‐pattern devices,22, 23, 24, 25, 26 microstructure photolithography,27, 28, 29 surface‐active topographies,30, 31, 32 and shape‐deformation actuators 33, 34, 35, 36, 37. Although the kinetic evolution of azo‐based LCs can be expedited by the anchoring memory effect in polymer‐stabilized mixture38, 39 or the push–pull effect in glassy elastomer,37, 40, 41 the inherently accelerative isomerization motion is still desirable, causing a variety of attractions to improve the essential action of isomerization compound with particular structures 42, 43, 44…”

Section: Introductionmentioning

confidence: 99%

Stimuli‐Directed Dynamic Reconfiguration in Self‐Organized Helical Superstructures Enabled by Chemical Kinetics of Chiral Molecular Motors

et al. 2017

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Dynamic controllability of self‐organized helical superstructures in spatial dimensions is a key step to promote bottom‐up artificial nanoarchitectures and functional devices for diverse applications in a variety of areas. Here, a light‐driven chiral overcrowded alkene molecular motor with rod‐like substituent is designed and synthesized, and its thermal isomerization reaction exhibits an increasing structural entropy effect on chemical kinetic analysis in anisotropic achiral liquid crystal host than that in isotropic organic liquid. Interestingly, the stimuli‐directed angular orientation motion of helical axes in the self‐organized helical superstructures doped with the chiral motors enables the dynamic reconfiguration between the planar (thermostationary) and focal conic (photostationary) states. The reversible micromorphology deformation processes are compatible with the free energy fluctuation of self‐organized helical superstructures and the chemical kinetics of chiral motors under different conditions. Furthermore, stimuli‐directed reversible nonmechanical beam steering is achieved in dynamic hidden periodic photopatterns with reconfigurable attributes prerecorded with a corresponding photomask and photoinduced polymerization.

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“…If even a small number of azomolecules are distributed in an LC phase, trans-cis isomerization can destabilize the phase by lowering the nematic-to-isotropic phase transition temperature (Eich and Wendorff, 1990). This enables fast isothermal photocontrol of phase transitions (Kato et al, 1996;Hayashi et al, 1995;Ikeda and Tsutsumi, 1995;Ikeda et al, 1990). Since these modulations are photoinitiated, it is straightforward to create patterns (Shannon et al, 1994).…”

Section: Classes Of Azobenzene Systemsmentioning

confidence: 99%

“…Thus, both mechanisms may be competing, with a different one dominating depending on the particular chromophore and environment. The emerging consensus nevertheless appears to be that inversion is the dominant pathway for most azobenzenes (Ikeda and Tsutsumi, 1995). The availability of the inversion mechanism explains how azos are able to isomerize easily even in rigid matrices, such as glassy polymers, since the inversion mechanism has a much smaller free volume requirement than rotation.…”

Section: Introduction To Azobenzenementioning

confidence: 99%