Fully Reversible Isomerization of Azobenzene Chromophores in Polyelectrolyte Layered Assemblies

Suzuki, I.; Ishizaki, Takeo; Hoshi, Tomonori; Anzai, Jun Ichi

doi:10.1021/ma010388y

Cited by 24 publications

(29 citation statements)

References 26 publications

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“…Some azobenzene residues have been reported to form small aggregates which can affect their packing in multilayer assemblies. [24] It should be noted that the amount of fluorescence of a filled capsule depends on the final size of the capsules because the concentration of material within a closed sphere increases relative to a decreasing volume, thus some capsules often appear more fluorescent than others (data not shown).…”

Section: Encapsulation Of Dye Labeled Dextranmentioning

confidence: 91%

Optically Driven Encapsulation Using Novel Polymeric Hollow Shells Containing an Azobenzene Polymer

Bédard

Skirtach

Sukhorukov

2007

Macromol. Rapid Commun.

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A novel method of macromolecule encapsulation using micron‐sized polymeric shells constructed with a photoactive azobenzene containing polyelectrolyte is discussed. Fluorescently labeled dextran molecules were encapsulated using light to remotely shrink and change the wall permeability of new polymeric hollow shells. We observed that the proportion of shells with dye encapsulated increased along with the duration of irradiation. Electron microscopy imaging illustrated significant changes in the surface roughness of shells after being exposed to light. Finally, this new system was shown to possess a high thermal stability.magnified image

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Section: Encapsulation Of Dye Labeled Dextranmentioning

confidence: 91%

Optically Driven Encapsulation Using Novel Polymeric Hollow Shells Containing an Azobenzene Polymer

Bédard

Skirtach

Sukhorukov

2007

Macromol. Rapid Commun.

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“…The order of magnitude of these rates is comparable to that obtained for other high molecular weight azo-polymers. [8,25] However, we did not observe a two-phase process as reported in some cases [8,25] for which a fast initial stage has been attributed to the relaxation of strained conformations of cis-azobenzene chromophores trapped in the glassy matrix. [4,26] Concerning our polysiloxanes the intrinsic flexibility of the polymer backbone may favor the motion of the thermodynamically unstable cis azo-chromophores and may partly explain the relatively fast return to the stable trans-state, even below T g .…”

Section: Kinetics Of Trans-cis Photoisomerization and Of Cis-trans Thmentioning

confidence: 47%

Photoresponsive New Polysiloxanes with 4‐Substituted Azobenzene Side‐Groups. Synthesis, Characterization and Kinetics of the Reversible Trans‐Cis‐Trans Isomerization

Hurduc

Adès²,

Belleney

et al. 2007

Macro Chemistry & Physics

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New polydimethylsiloxanes with p‐substituted azobenzene side‐groups were synthesized. Thin films and solutions exhibit a photochemical trans‐cis isomerization of the azobenzene groups, followed by their cis‐trans thermal relaxation in the dark. In films, relaxation rates were found to be 100–1 000 times slower than the rates of photoisomerization, the former being very sensitive to the electron‐acceptor character of the substituents. in solution, the rates of cis‐trans relaxation are lower than those obtained for the solid state. This is ascribed to the dipolar intramolecular interactions between cis chromophores, which are favored in solution.magnified image

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“…Calculated rate constants are an order of magnitude greater than typical azobenzenes in solution[15]. Eutectic 1: k 1 = 0.72 × 10 -2 min -1 , k 2 = 0.20 × 10 -2 min -1 .…”

mentioning

confidence: 80%

“…Because of the alignment effect of the confining surface [8] we hypothesize that azobenzene mesogens close to the pore wall isomerizes faster than those in the bulk. We found that the thermal relaxation of confined azobenzene mesogens resembled that of azobenzenes in the solid state [15] and could be modeled using the biexponential expression …”

Section: Photoswitching and Kineticsmentioning

confidence: 99%

Photoswitchable gas permeation membranes based on azobenzene-doped liquid crystals

2009

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We have fabricated switchable gas permeation membranes in which a photoswitchable low-molecular-weight liquid crystalline (LC) material acts as the active element. Two different LC eutectic mixtures based on cyanobiphenyls and phenyl benzoates, respectively, were doped with mesogenic azo dyes and infused into commercially available tracketched porous polycarbonate membranes with regular cylindrical pores (0.40 to 10.0 μm). Photo-induced isothermal phase changes in the imbibed mesogenic material afforded large, reversible changes in the permeability of the photoswitchable membrane to nitrogen. The membrane imbibed with the photoswitchable cyanobiphenyl LC material demonstrated low permeability in the nematic state, while the photogenerated isotropic state demonstrated a 16×-greater sorption coefficient. Both states obey a high linear sorption behavior in accordance with Henry's Law. The membrane imbibed with the photoswitchable phenyl benzoate LC showed the opposite permeability behavior to the biphenylimbibed membrane, along with nonlinear sorption behavior. Permeability switching response times for the membranes on the order of 5 s were demonstrated using alternating UV and >420-nm radiation at an intensity of 2 mW/cm 2 . The effect of thermomolecular motion on gas sorption and diffusion over the LC-isotropic phase transitions are, for the first time, evaluated under isothermal conditions. These photoswitchable membranes are the first examples of systems that are capable of rapid and reversible gas permeation switching. Such switchable and/or tunable membranes are in high demand for applications in analytics, screening, and membrane reactors.

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Fully Reversible Isomerization of Azobenzene Chromophores in Polyelectrolyte Layered Assemblies

Cited by 24 publications

References 26 publications

Optically Driven Encapsulation Using Novel Polymeric Hollow Shells Containing an Azobenzene Polymer

Optically Driven Encapsulation Using Novel Polymeric Hollow Shells Containing an Azobenzene Polymer

Photoresponsive New Polysiloxanes with 4‐Substituted Azobenzene Side‐Groups. Synthesis, Characterization and Kinetics of the Reversible Trans‐Cis‐Trans Isomerization

Photoswitchable gas permeation membranes based on azobenzene-doped liquid crystals

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