Organization of an Amphiphilic Azobenzene Derivative in Monolayers at the Air−Water Interface

Pedrosa, José M.; Martín‐Romero, María T.; Camacho, Luis; Möbius, Dietmar

doi:10.1021/jp012584c

Cited by 97 publications

(155 citation statements)

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“…These values are consistent with estimations found in the literature [14] and values extrapolated for thin suspended liquid crystal films [25]. We can qualitatively relate these results to the known tendency of azobenzene derivatives to form supramolecular aggregates (H-aggregates), whose presence can be revealed here by spectroscopy methods [26]. In short, aggregates form in such a way that the azobenzene planes of neighboring molecules are parallel, stacking perpendicularly to the molecular tilting direction.…”

Section: Prl 100 037801 (2008) P H Y S I C a L R E V I E W L E T T Esupporting

confidence: 91%

Probing Elastic Anisotropy from Defect Dynamics in Langmuir Monolayers

et al. 2008

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We study the dynamics of annihilation of point defects in Langmuir monolayers. The absence of hydrodynamic effects allows us to quantitatively relate the asymmetry in defect mobility to the elastic anisotropy of the material, which in turn can be varied through the control of the surface pressure applied to the monolayer. Using the proposed theoretical analysis, we are able to obtain rather elusive equilibrium properties out of relatively simple dynamical measurements. In particular, we measure the elastic constants and their pressure dependence.

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Section: Prl 100 037801 (2008) P H Y S I C a L R E V I E W L E T T Esupporting

confidence: 91%

Probing Elastic Anisotropy from Defect Dynamics in Langmuir Monolayers

et al. 2008

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“…1 Nowadays, studies on macroscopic thermal motion of soft matters received attentions from the viewpoint of biomimetics. 2,3 Next key step for soft matters is to create a material whose macroscopic motion is controlled by external 15 stimuli. 4 One of the strategies is to create soft materials consisting of subunits sensitive to external inputs, for instance, the photoinduced bending of polymer films consisted of azobenzene derivatives.…”

mentioning

confidence: 99%

“…1) display reversible 45 photochromic behaviour under exposure to 366 nm UV light (E-Z isomerization) and 435 nm blue light (Z-E isomerization). 13 Preparation of the assemblies generally involved hydration of a mixture of 4.5 mg sodium oleate (1Na) and 0.45 mg (10wt%) of long axis of the azobenzene chromophore, 15 this photoinduced deformation indicates that the azobenzene is oriented vertically against the membrane surface, and that azobenzene molecules on the upper and lower vesicular membrane surfaces absorbed light 45 more efficiently than those on lateral surfaces (Fig. 4).…”

mentioning

confidence: 99%

“…The extended induction period after irradiation suggests that the morphological changes occur only after substantial amounts of 2 have been isomerized. In other words, some kinds of cooperation work among photoisomerized 15 azobenzenes dispersed in oleate assembly and induce the macroscopic motion. 19 The forceful motion exhibited by the helical assemblies and the presence of an induction period strongly suggest there are cooperatively propagating mechanisms such as domino effects 20 occurring inside or at the surface of the supramolecular assemblies.…”

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confidence: 99%

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Macroscopic motion of supramolecular assemblies actuated by photoisomerization of azobenzene derivatives

et al. 2013

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Submillimetre size self-assemblies composed of oleate and azobenzene derivatives show forceful motions such as screwtype coiling-recoiling motion by photoirradiation.In the past half century, many molecular-level machines which 10 change their molecular structure upon exposure to stimuli have been reported. 1 Nowadays, studies on macroscopic thermal motion of soft matters received attentions from the viewpoint of biomimetics. 2,3 Next key step for soft matters is to create a material whose macroscopic motion is controlled by external 15 stimuli. 4 One of the strategies is to create soft materials consisting of subunits sensitive to external inputs, for instance, the photoinduced bending of polymer films consisted of azobenzene derivatives. 5,6 Another strategy is to create soft materials in which macroscopic motions of molecular assemblies 20 are actuated by small amount of molecular machines. 7 To date, there are few reports describing macroscopic mechanical behaviour based on the latter strategy. 8 Here, we report reversible and spatially controlled macroscopic motion of oleate assembles which have submillimetre length. 25Mixtures of oleic acid (1H) and oleate (1 -) ( Fig. 1) are capable of self-assembly in aqueous solution. The morphology of the mixture depends on pH and ionic strength (I). [9][10][11] In I = 0.1 pH 8-10 aqueous media, oleates form vesicles (Fig. 2a). Between pH 7 and 8, they form several complex aggregates called "blocks" that 30 exhibit an inverted hexagonal phase 12 (Fig. 2b). In the transition region, helical and straight multilayer assemblies are coexisted with vesicles and blocks. 11 It is considered that the shape of assembly depends on the ratio of 1H and 1 -in each assembly. According to the microscopic observations of shape and 35 dynamics described in Ref. 11, the helical assemblies are sufficiently flexible to change their macroscopic helical pitch and curvature, but are also elastic because of the highly-ordered stacking structure of oleate molecules in the assembly. As demonstrated in Fig. 3, the helical assemblies exhibit a highly 40 elastic response to mechanical stress. We assumed that this softness and elasticity of the self-assembly is suitable to the spatially moving material in which motion of molecular machine should be propagated.Azobenzene derivatives 2-5 ( Fig. 1) display reversible 2-5 by addition of 70 mM KH 2 PO 4 -K 2 HPO 4 buffer solution (1.0 mL) and sonication for 20 min. A 125 µL aliquot of each suspension containing one of 2-5 was placed in a sealed microscope slide and incubated for 1 day at 25°C. All 60 azobenzene derivatives dissolved into oleate assemblies. The pH range required for formation of helical assemblies was slightly lowered by the addition of 2-5. 14 Helical assemblies were formed when pH 7.3 buffer solution was used as the dispersing medium (the pH of the dispersion was approximately 7.5); pH 65 values of buffer solution higher than 7.3 resulted in vesicle formation, and pH values lower than 7.3 led to the formation of

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“…Thereupon, we hypothesize the probable model for adsorption of the TPyP derivatives on the WO 3 colloid surface, as shown in Scheme 2. [51][52][53] Taking into account that the curvature radius R of WO 3 colloid particles nearly equals to 7.9 nm (from TEM image), we predicted the molecular area (per TPyP derivative) as follows: It is well-known that molecular aggregation drastically modifies the absorption characteristics (spectral shifts, band broadening, and sharpening) of the dyes.…”

Section: Surface Aggregate Structure Deduced From Kasha's Exciton Coumentioning

confidence: 99%

Mechanism of Peripheral Substituent Effects on Adsorption–Aggregation Behaviors of Cationic Porphyrin Dyes on Tungsten(VI) Oxide Nanocolloid Particles

Kanetada

Matsumura

Yamazaki

et al. 2013

ACS Appl. Mater. Interfaces

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The adsorption and aggregation behaviors of the cationic porphyrin derivatives such as 5,10,15,20-tetrakis(4-pyridyl)porphyrin [TPyP],5,10,15, Judging from the exciton coupling theory and adsorption measurements, we concluded that the J-dimer geometry of the TPyP derivatives adsorbed on the WO 3 colloid particle surface is strongly dependent on the presence and difference of peripheral substituents. The results described here indicate a new and promising way of designing surface supramolecular structures combination of two principles, the selfassociation of organic dyes and the steric repulsive interaction between the peripheral substituents and the inorganic semiconductor surfaces.

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Organization of an Amphiphilic Azobenzene Derivative in Monolayers at the Air−Water Interface

Cited by 97 publications

References 43 publications

Probing Elastic Anisotropy from Defect Dynamics in Langmuir Monolayers

Probing Elastic Anisotropy from Defect Dynamics in Langmuir Monolayers

Macroscopic motion of supramolecular assemblies actuated by photoisomerization of azobenzene derivatives

Mechanism of Peripheral Substituent Effects on Adsorption–Aggregation Behaviors of Cationic Porphyrin Dyes on Tungsten(VI) Oxide Nanocolloid Particles

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