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501.
502.
《Liquid crystals》2012,39(12):1889-1898
ABSTRACTA series of novel azobenzene chiral liquid crystals (Mt4AZOnB) containing (-)-menthyl were successfully synthesised. Terminal alkyl chains of the molecules varied from methyl to hexyl. The chemical structures were characterised by Fourier transform infrared and 1H-NMR spectra. Liquid crystalline behaviour of the chiral liquid crystals was characterised by differential scanning calorimetry and polarising optical microscopy. The effect of terminal alkyl chains on mesomorphic and photoisomerisation behaviour of azobenzene-based liquid crystals is discussed. The lower members (n = 1, 2, 3, 4) are monotropic and only the higher members (n = 5, 6) show enantiotropic behaviour. These compounds show a distinct odd-even effect for the phase transition temperature when the parity of the terminal chain is varied. 相似文献
503.
Ulises Ruiz Pasquale Pagliusi Clementina Provenzano Valery P. Shibaev Gabriella Cipparrone 《Advanced functional materials》2012,22(14):2964-2970
Chiral periodic structures and photonic crystals have attracted a great deal of interest due to their applications in advanced photonics. As a consequence, the design and the fabrication of periodic microstructures in photosensitive materials have been widely investigated. Many achievements in the fabrication of such devices have been made over the last decade, but most of the established methods are still restricted to light intensity distribution with different structural shapes and minor attention has been devoted to exploit the vectorial nature of the light coupled with the response of polarization sensitive materials. Here, supramolecular chiral structuring in an amorphous azo‐polymer is demonstrated, coupling the strong and diversified photoresponse of the material with the holographic recording of 2D polarization patterns. The smart polymer organization guided by the complex light field induces periodic chiral microstructures, with spiral‐ or ribbon‐like shape and identical or opposite helicity, characterized by high stability and complete reconfigurability. The holographic structures are theoretically described by means of the Jones matrix method and experimentally investigated, confirming the simultaneous presence of both linear and circular photoinduced anisotropies. These results prove an alternative approach to design a new class of materials with periodic chiral arrangement. 相似文献
504.
Summary: A microscopic theory is proposed to describe light-induced deformation of photo-sensitive elastomers bearing azobenzene chromophores in their strands. We use an orientation approach in which it is assumed that the light-induced deformation is caused by reorientation of azobenzene chromophores with respect to the electric vector of the linearly polarized light, E , due to the trans-cis-trans photoisomerizaion process whose efficiency depends on the orientation of the chromophores with respect to the vector E . In the framework of the Gaussian approximation for elasticity of network strands it is shown that the value of the light-induced deformation depends on the chemical structure of network strands, namely, on the orientation distribution of chromophores around the main chains which is related to the length and elasticity of spacers. Depending on the chemical structure, azobenzene elastomers can demonstrate expansion or uniaxial contraction along the vector E , as well as non-monotonic deformation with increasing light intensity (expansion at small light intensities and contraction at high ones). 相似文献
505.
506.
Methacrylate copolymers containing, in side chain azobenzene groupings with heterocyclic sulfonamide substituents: N-(2,6-dimethylpyrimidin-4-yl)sulfamoyl (sulfisomidine) and N-(5-methylisoxazol-3-yl) sulfamoyl (sulfamethoxazole) were investigated. The materials undergo reversible trans-cis isomerisation during illumination with light. This results in changes of dipole moment, polarizability and refractive index. Ellipsometric measurements showed a distinct decreasing refractive index during illumination with light corresponding to absorption band (ca. 450 nm). Depending on the polymer, the change of real part of refractive index in spin-coated films was between 0.016 and 0.031. The dynamics of growth and decay of refractive index changes, was described by biexponential function approach. 相似文献
507.
Alaa S. Abd-El-Aziz Erin K. Todd Rawda M. Okasha Tarek H. Afifi 《Macromolecular Symposia》2003,196(1):89-99
The synthesis of cationic organoiron polymers with azobenzene moieties in their side chains has been accomplished via nucleophilic aromatic substitution and ring-opening metathesis polymerization (ROMP) reactions. Polyaromatic ethers and thioethers with azobenzene moieties in their side chains were functionalized with different chromophores to yield yellow-, orange- and red-colored polymers. Polynorbornenes with azobenzene-containing side chains were isolated following ROMP of their monomeric analogs. All of the organoiron polymers were soluble in polar organic solvents and underwent reversible electrochemical reduction processes. Photobleaching of the azobenzene-containing polymers was achieved in the presence of hydrogen peroxide. The metallated polymers had glass transition temperatures approximately 50 to 80°C higher than their organic analogs. 相似文献
508.
Antoni Snchez‐Ferrer Alexey Merekalov Heino Finkelmann 《Macromolecular rapid communications》2011,32(8):671-678
The mechanical behaviour of monodomain nematic side‐chain liquid‐crystalline elastomers containing azoderivatives as pendant groups or crosslinkers has been studied under UV irradiation and in the darkness at different temperatures. From the evaluation of the opto‐mechanical experiments, the mechanical efficiency, kinetic rates, activation energies and the isomerization mechanism of the azocompounds in the liquid‐crystalline matrix could be determined, as well as the effect of the chemical constitution of the azobenzene derivatives and their role in the elastomeric network.