Local free volume and structural relaxation studied with photoisomerization of azobenzene and persistent spectral hole burning in poly(alkyl methacrylate)s at low temperatures

Yoshii, Koji; Machida, Shinjiro; Horie, Kazuyuki

doi:10.1002/1099-0488(20001201)38:23<3098::aid-polb110>3.0.co;2-c

Cited by 27 publications

(18 citation statements)

References 20 publications

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“…[1] When azobenzene is incorporated in a polymeric film, a higher intensity for the n-p Ã transition was observed because of partial disruption of the molecular symmetry caused by the solid environment. [21] There have been a few quantitative experimental reports concerning the intensity of the n-p Ã transition and l max for the donoracceptor-type azobenzene polymer in the film state. An attempt was made to mathematically decompose the spectrum of Figure 3(a) into two bands using a combinatorial equation that contained two Gaussian functions.…”

Section: Resultsmentioning

confidence: 99%

Control of Photodynamic Motions of Azobenzene‐Derivative Polymers by Laser Excitation Wavelength

Kim

Lee

Chun

et al. 2007

Macro Chemistry & Physics

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The dynamic properties of photoinduced alignment and surface relief grating (SRG) formation as a function of excitation wavelength (λex = 454, 488, 514, 532, 568, and 647 nm) are examined using five azobenzene‐derivative polymers, whose absorption spectra are tuned by substituting different electron‐withdrawing groups (CF3, CN, CNCl, NO2, (CN)2). The dynamics sensitively depend on λex. The fastest rate of photoinduced alignment is observed when λex is between λmax of the trans π–π* transition and that of the cis n–π* transition. A model of trans–cis photoisomerization has been developed based on competition between photoexcitation and relaxation, in which the n–π* transition has a faster relaxation pathway than the π–π* transition. Under conditions of adequate absorbance of the trans form at λex, i.e., greater than ${1 \over 2}$Amax, the rate of SRG formation increases at longer λex.

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Section: Resultsmentioning

confidence: 99%

Control of Photodynamic Motions of Azobenzene‐Derivative Polymers by Laser Excitation Wavelength

Kim

Lee

Chun

et al. 2007

Macro Chemistry & Physics

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“…AB photoisomerizes 4 K, which indicates the process cannot be frozen out completely. 139 Thermal isomerization of c-AB. The thermal cistrans isomerization has an activation barrier of B95 kJ mol À1 in solution and B105 kJ mol À1 in a melt.…”

Section: Factors Affecting Quantum Yield Of Isomerizationmentioning

confidence: 99%

Photoisomerization in different classes of azobenzene

2012

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Azobenzene undergoes trans→cis isomerization when irradiated with light tuned to an appropriate wavelength. The reverse cis→trans isomerization can be driven by light or occurs thermally in the dark. Azobenzene's photochromatic properties make it an ideal component of numerous molecular devices and functional materials. Despite the abundance of application-driven research, azobenzene photochemistry and the isomerization mechanism remain topics of investigation. Additional substituents on the azobenzene ring system change the spectroscopic properties and isomerization mechanism. This critical review details the studies completed to date on the 3 main classes of azobenzene derivatives. Understanding the differences in photochemistry, which originate from substitution, is imperative in exploiting azobenzene in the desired applications.

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“…In such systems, isomerization of azobenzene is often affected by steric distortion or the environment to which the azobenzene chromophore is exposed. In glassy polymer matrices, photo and thermal isomerizations of azobenzene do not follow the first-order kinetics due to the free volume in the matrices . Bulky substituents 5 or cyclic structures 1,6 cause steric hindrance and alter the isomerization behavior.…”

Section: Introductionmentioning

confidence: 99%

Novel Crystal Structure, Cis−Trans Isomerization, and Host Property of Meta-Substituted Macrocyclic Azobenzenes with the Shortest Linkers

2003

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Azobenzenophanes, in which two (2), three (3), and four (4) azobenzene units are connected cyclically by methylene linkers at the meta positions, were synthesized. The effect of ring strain on the structure and the photochemical and the thermal isomerization of azobenzene were investigated. Complex formation with guest species such as alkali metal cations and solvent molecules was observed. X-ray crystal analyses revealed the crystal structure of all three isomers of 2. Compound 2(t,c) was distorted due to the ring strain and 2(c,c) was not deformed. Both 3 and 4 formed supramolecular channel structures in which an azobenzenophane molecule holds a solvent molecule in the molecular cavity. Upon exposure to light, 2, 3, and 4 exhibited stepwise trans-cis photoisomerization in solutions. The quantum yields for all isomerization steps of 2 were determined, and these values suggested that interactions between chromophores such as energy transfer and/or steric distortion affect the isomerization process. The lifetime of 2(c,c) (19.7 days) was longer than that of 2(t,c) (6.1 days) at room temperature. The relative stability of these isomers was explained by the isokinetic (or compensation) relationship between deltaH++ and deltaS++ values and by the effect of the ring strain. The relative energies of three isomers of 2 were estimated by HF/6-31G** calculations, and these values indicated that 2(t,c) has the largest ring strain. Complexes (1:1 and 2:1) between macrocycles and alkali metal cations (Li+, Na+, K+, Rb+, Cs+) were observed by ESIMS. The cation selectivity was shifted upon photoirradiation especially in 4.

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Local free volume and structural relaxation studied with photoisomerization of azobenzene and persistent spectral hole burning in poly(alkyl methacrylate)s at low temperatures

Cited by 27 publications

References 20 publications

Control of Photodynamic Motions of Azobenzene‐Derivative Polymers by Laser Excitation Wavelength

Control of Photodynamic Motions of Azobenzene‐Derivative Polymers by Laser Excitation Wavelength

Photoisomerization in different classes of azobenzene

Novel Crystal Structure, Cis−Trans Isomerization, and Host Property of Meta-Substituted Macrocyclic Azobenzenes with the Shortest Linkers

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