Investigation on Viscoelasticity of Waterborne Polyurethane with Azobenzene-containing Pendant Groups under Ultraviolet and Visible-light Irradiation
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Keywords:
Azobenzene
Isophorone diisocyanate
Ultraviolet light
Hydroxymethyl
Azo compound
Ultraviolet
Novel water-soluble triply-responsive homopolymers of N,N-dimethylaminoethyl methacrylate (DMAEMA) containing an azobenzene moiety as the terminal group were synthesized by atom transfer radical polymerization (ATRP) technique. The ATRP process of DMAEMA was initiated by an azobenzene derivative substituted with a 2-bromoisobutyryl group (Azo-Br) in the presence of CuCl/Me₆TREN in 1,4-dioxane as a catalyst system. The molecular weights and their polydispersities of the resulting homopolymers (Azo-PDMAEMA) were characterized by gel permeation chromatography (GPC). The homopolymers are soluble in aqueous solution and exhibit a lower critical solution temperature (LCST) that alternated reversibly in response to Ph and photoisomerization of the terminal azobenzene moiety. It was found that the LCST increased as pH decreased in the range of testing. Under UV light irradiation, the trans-to-cis photoisomerization of the azobenzene moiety resulted in a higher LCST, whereas it recovered under visible light irradiation. This kind of polymers should be particularly interesting for a variety of potential applications in some promising areas, such as drug controlled-releasing carriers and intelligent materials because of the multistimuli responsive property.
Azobenzene
Moiety
Atom-transfer radical-polymerization
Azo compound
Gel permeation chromatography
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When a nematic liquid crystal is doped with a large amount of a liquid crystalline azobenzene compound (15 wt %), the photoisomerization of azobenzene under UV and visible light irradiation can give rise to reversible and interconvertible photochemical phase transition and photochemical phase separation. Both normal and reverse modes of photocontrolled switching of transmittance through crossed polarizers can be realized with the same mixture of liquid crystal/azobenzene dopant.
Azobenzene
Visible spectrum
Polarizer
Azo compound
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Azobenzene
Isophorone diisocyanate
Ultraviolet light
Hydroxymethyl
Azo compound
Ultraviolet
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From all type of external stimuli the light rays are most commonly used because it involves only photochemical processes easily to control. One of the most studied of photochemical processes is photoisomerization groups, in particular the azobenzene groups. The azobenzene and his derivatives, known for Z(sin)-E(anti) reversible photoisomerization properties, have been extensively used as functional groups to synthesize various photosensitive compounds. The UV irradiation at different time of modified maleic anhydride - styrene copolymers with azo dye solutions were with UV light to increase the rate of Z(sin)-E(anti) isomerisation. The changes in the spectral absorption domain for azo compounds, a decrease in optic absorbance after irradiation, with a predisposition to come back at primary value was made with SECOMAMS750 UV–Vis spectrophotometer.
Azobenzene
Absorbance
Azo compound
Maleic anhydride
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Abstract New hydrophilic photochromic polymeric systems containing side‐chain azobenzene groups were synthesized by radical copolymerization of 4‐acryloyloxyazobenzene with hydrophilic acrylic comonomers containing in the side chain either amide or quaternary onium groups. In all cases copolymerization products characterized by an almost random distribution of monomeric units were obtained. On irradiation at 366 nm, azobenzene‐ containing copolymers underwent trans ‐ to ‐ cis photoisomerization of the side‐chain azo groups and in all cases monoexponential decay of the 320 nm absorbance was observed. Copolymer properties were investigated by DSC analysis, solubility measurements, UV spectroscopy and photoisomerization kinetics. The results obtained are discussed in terms of nature and content of hydrophilic comonomer and water content of the solvent used. The possibility of photomodulating copolymer solubility is also suggested.
Comonomer
Azobenzene
Azo compound
Side chain
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The photoisomerization of azo dyes in solvents has been investigated using a mercury lamp (400 W) with the interference filters. Azobenzene in N, N-dimethylformamide showed a typical photoisomerization from trans to cis upon irradiation of the ultraviolet light, and from cis to trans upon irradiation of the visible light. In several systems, however, the photoisomerization was from trans to cis upon irradiation of the ultraviolet or visible light, and from cis to trans when kept in the dark.2-(4-Phenylazophenyl)hydrazine-1-sulfonic acid caused a photoconversion in water. The electron-attracting and electron-releasing substituent groups in azobenzene exerted an influence on the photoisomerization, together with the permanent dipole moment of solvent.
Azobenzene
Dimethyl formamide
Ultraviolet light
Ultraviolet
Visible spectrum
Azo compound
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Abstract A novel monomer, ethyl 4‐[4‐(11‐methacryloyloxyundecyloxy)phenyl azobenzoyl‐oxyl] benzoate, containing a photoisomerizable NN group was synthesized. The monomer was further diblock copolymerized with methyl methacrylate. Amphiphilic diblock copolymer poly(methyl methacrylate‐ block ‐ethyl 4‐[4‐(11‐methacryloyloxyundecyloxy)phenyl azobenzoyl‐oxyl] benzoate ( PMMA ‐ b ‐ PAzoMA ) was synthesized using atom transfer radical polymerization. The reverse micelles with spherical construction were obtained with 2 wt % of the diblock copolymer in a THF/H 2 O mixture of 1:2. Under alternating UV and visible light illumination, reversible changes in micellar structure between sphere and rod‐like particles took place as a result of the reversible E‐Z photoisomerization of azobenzene segments in PMMA ‐ b ‐ PAzoMA . Microphase separation of the amphiphilic diblock copolymer in thin films was achieved through thermal and solvent aligning methods. The microphases of the annealed thin films were investigated using atom force microscopy topology and scanning electron microscopy analyses. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 1142–1148, 2010
Azobenzene
Atom-transfer radical-polymerization
Azo compound
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Citations (27)
Abstract Novel water‐soluble triply‐responsive homopolymers of N,N ‐dimethylaminoethyl methacrylate (DMAEMA) containing an azobenzene moiety as the terminal group were synthesized by atom transfer radical polymerization (ATRP) technique. The ATRP process of DMAEMA was initiated by an azobenzene derivative substituted with a 2‐bromoisobutyryl group (Azo‐Br) in the presence of CuCl/Me 6 TREN in 1,4‐dioxane as a catalyst system. The molecular weights and their polydispersities of the resulting homopolymers (Azo‐PDMAEMA) were characterized by gel permeation chromatography (GPC). The homopolymers are soluble in aqueous solution and exhibit a lower critical solution temperature (LCST) that alternated reversibly in response to Ph and photoisomerization of the terminal azobenzene moiety. It was found that the LCST increased as pH decreased in the range of testing. Under UV light irradiation, the trans ‐to‐ cis photoisomerization of the azobenzene moiety resulted in a higher LCST, whereas it recovered under visible light irradiation. This kind of polymers should be particularly interesting for a variety of potential applications in some promising areas, such as drug controlled‐releasing carriers and intelligent materials because of the multistimuli responsive property. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 2564–2570, 2010
Azobenzene
Moiety
Atom-transfer radical-polymerization
Azo compound
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Azobenzene
Chromophore
Photostationary state
Triad (sociology)
Azo compound
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ABSTRACT Photochromic compounds having plural chiral sites as well as azobenzene groups in a molecule was synthesized by reacting 4-, and 3-, 2-carboxy-4′-hexyloxyazobenzenes with isosorbide, and isomannide. A cholesteric liquid crystal (Ch LC) was induced by adding each chiral azobenzene compound in a nematic LC. Most azo dyes showed photochemical decrease in the helical twisting power ( HTP ) by UV irradiation. The change in HTP was related to the photochemical change in the molecular shape. Reversible control of the reflection wavelength of the Ch LC was achieved over a whole range of visible region by irradiation of UV and visible light.
Azobenzene
Visible spectrum
Azo compound
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