Modeling the Interface Region of Command Surface 2. Spectroscopic Evaluations of Azobenzene/Liquid Crystal Hybrid Langmuir−Blodgett Films under Illumination

Ubukata, Takashi; Seki, Takahiro; Morino, Shin’ya; Ichimura, Kunihiro

doi:10.1021/jp9936042

Cited by 30 publications

(32 citation statements)

References 30 publications

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“…4 A strong molecular cooperativity and essential factors of orientation switching behavior resulted by the photoisomerization of Az have been revealed by this approach. [50][51][52] The surface pressure-area (-A) isotherms obtained at various mixing ratios (r = [5CB]/[Az units]) indicate that one Az side chain can accommodate two 5CB molecules. Above this critical ratio, thinner parts consisting of pure 5CB monolayer start to grow to show a two-dimensional phase separation.…”

Section: Photocontrol Of Two Dimensional Phase Separationmentioning

confidence: 99%

“…[110][111][112] This work was initiated as a serendipitous extension during evaluations of the command surface model using 6Az10-PVA/ 5CB hybrid LB films. [51][52][53]113 The hybrid films are irradiated with non-polarized UV (365 nm) light in advance to attain a cis-rich photoequilibrated state (UV light treatment). Starting from this state, the irradiation that induces the film migration is performed by argon ion laser beam (488 nm) which also induces back reaction to the trans form.…”

Section: Binary Component Systemsmentioning

confidence: 99%

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Dynamic Photoresponsive Functions in Organized Layer Systems Comprised of Azobenzene-containing Polymers

Seki

2004

Polym J

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ABSTRACT:Azobenzene (Az)-containing polymers provide fascinating photoresponsive actuation systems. When they are organized at interfaces, the motion of Az unit occurring at a molecular (sub-nano) scale can be transferred and amplified to larger scales of materials. This review article focuses to selected research topics on organized layer systems of Az-containing polymers proceeding in our laboratory. They involve i) photomechanical response of monolayers at nanometer levels in thickness and centimeters in area, ii) monolayer-mediated photoorientation of polymer (polysilane) and mesoporous silica at nano-to sub-micrometer levels in thickness, and iii) instant mass migration triggered by patterned photoirradiation occurring at distances over micrometer levels. In every system, strong cooperative interplays between the Az unit and organized molecular or macromolecular assemblies play the essential roles. Promotions of these research areas are anticipated to provide wide and new opportunities for material processing and creation of new classes of photofuncitional soft materials.

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Section: Photocontrol Of Two Dimensional Phase Separationmentioning

confidence: 99%

Section: Binary Component Systemsmentioning

confidence: 99%

Dynamic Photoresponsive Functions in Organized Layer Systems Comprised of Azobenzene-containing Polymers

Seki

2004

Polym J

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“…As already illustrated in Figure b, the photoinduced anisotropy of azopolymers can be put to good use as command layers, in which the orientation of a thick layer of liquid crystals (“soldiers”) is controlled by the photoresponse of a thin azopolymer layer (“commander”), typically located next to the substrate below the LC layer but more recently shown to be applicable as well at the free surface . Mixed multilayers of an amphiphilic azopolymer and a well‐studied liquid crystal, 5CB, depicted in Figure , were prepared using the Langmuir–Blodgett technique in order to mimic the interfacial region between the command surface and the LC phase . IR spectroscopy in the transmission and the reflection–absorption (IRRAS) modes were combined to provide information on both in‐plane and out‐of‐plane molecular anisotropy.…”

Section: Photo‐orientation Of Azobenzenes and Photocontrol Of Passivementioning

confidence: 99%

“…The reverse process, from tilted to homeotropic alignment, was conducted using 436 nm visible light (bottom right panel of Figure ) and revealed that a threshold of azobenzene cis–trans conversion, reached after 150 s at this irradiance, is needed to induce a change in 5CB orientation. Both the homeotropic‐tilted and the tilted‐homeotropic transitions could be accelerated by increasing the irradiance of the illuminating light . Later, Ohe et al demonstrated the power of vibrational sum frequency generation (SFG) spectroscopy in resolving the molecular orientation of the same azopolymer at the air–water interface.…”

Section: Photo‐orientation Of Azobenzenes and Photocontrol Of Passivementioning

confidence: 99%

“…IR absorbance of selected bands as a function of time upon trans‐to‐cis isomerization (366 nm light, bottom left panel) and cis‐to‐trans isomerization (436 nm light, bottom right panel) of a stack of 49 Langmuir–Blodgett layers of the polymer and 5CB in equimolar proportion relative to the azo‐containing repeat unit. Reproduced with permission . Copyright 2001, American Chemical Society.…”

Section: Photo‐orientation Of Azobenzenes and Photocontrol Of Passivementioning

confidence: 99%

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Taming Macromolecules with Light: Lessons Learned from Vibrational Spectroscopy

Vapaavuori

Bazuin

Pellerin

2017

Macromol. Rapid Commun.

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application of vibrational spectroscopy to rotaxane-based molecular machines, [11] molecular motors, [12] and molecule-based electronics, such as molecular electronic switches, [13] are highly recommended.In this feature article, we will focus on one of the most commonly used photoswitches, both for materials engineering and biological applications, namely, azobenzene. [14] This motif is known to change its geometry upon illumination with ultraviolet or visible light, in a socalled photoisomerization reaction from the thermodynamically stable trans conformation to the bent cis conformation (Figure 1a). [15,16] This reaction can be used to both decrease and destroy existing order in materials, as in the cases of photoinduced unfolding of azobenzenecrosslinked alpha-helical peptides, [17] photo induced nematic-isotropic phase transitions [18] and isothermal solid-toliquid transitions, [19] or, on the contrary, to induce order and anisotropy in initially isotropic or less ordered materials, such as in photoinduced birefringence, photoinduced chirality, alloptical poling, and surface relief grating (SRG) formation. [2,20,21] The photoisomerization of individual azobenzene moieties is known to occur in the picosecond timescale and results in changes in its molecular dimensions and properties, such as its dipole moment, solubility and UV-vis absorption. [15] Apolar azobenzene molecules typically have well isolated cis and trans absorption bands along with long thermal cis lifetimes. They are therefore suitable for optical switching applications where two "stable" long-lived states are required. By contrast, functionalizing azobenzene molecules with electron donating and electron withdrawing substituents (or push-pull substitution) alters their photochemistry, typically leading to an overlap of cis and trans absorption bands and thus to quasi-continuous photoswitching between the trans and the cis geometrical isomers. [15,16] Examples of drastic changes in material systems resulting from bistable photoswitching between trans and long-lived cis isomers are illustrated in Figure 1b-d and include photoswitching of the tilt of liquid crystals by an azopolymer command layer, [22] the light-powered contraction of a helical ribbon of a liquid crystalline azopolymer, mimicking plant tendrils, [23] and the photoinduced decrease in helix content of a peptide cross-linked by an azobenzene. [17] Demonstrations of the use of continuous azobenzene photoswitching between the two geometrical isomers, shown in Figure 1e

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Photoinduced Motion Associated with Monolayers

Ichimura¹,

Seki²

2011

Molecular Switches

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Modeling the Interface Region of Command Surface 2. Spectroscopic Evaluations of Azobenzene/Liquid Crystal Hybrid Langmuir−Blodgett Films under Illumination

Cited by 30 publications

References 30 publications

Dynamic Photoresponsive Functions in Organized Layer Systems Comprised of Azobenzene-containing Polymers

Dynamic Photoresponsive Functions in Organized Layer Systems Comprised of Azobenzene-containing Polymers

Taming Macromolecules with Light: Lessons Learned from Vibrational Spectroscopy

Photoinduced Motion Associated with Monolayers

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