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Photoresponsive Properties (photoresponsive + property)
Selected AbstractsSynthesis and Photoresponsive Properties of Optically Active Methacrylic Polymers Bearing Side-Chain Azocarbazole MoietiesMACROMOLECULAR CHEMISTRY AND PHYSICS, Issue 1 2009Luigi Angiolini Abstract The synthesis of a novel optically active methacrylic monomer containing in the side chain the (S)-3-hydroxy- N -phenyl pyrrolidine ring linked to a 4-cyanophenylazocarbazole moiety [(S)- MCAPP - C] and of the analogous achiral monomer (MCAPE-C) is described. Both the monomers have been radically polymerized to produce the corresponding homopolymers as well as the copolymer at 50% molar composition. The photoinduction of birefringence has been assessed on thin films of the polymeric materials in order to evaluate their behavior as materials for optical data storage. Surface relief gratings (SRG) can also be inscribed over the material. The results are interpreted in terms of different cooperative performance and conformational stiffness of the chromophoric co-units in the polymeric derivatives. [source] Photochromic and Photoresponsive Properties of Methacrylic Polymers Bearing Optically Active Hydroxysuccinimide in the Side ChainMACROMOLECULAR CHEMISTRY AND PHYSICS, Issue 21 2007Luigi Angiolini Abstract The photochromic and photoresponsive properties of a series of optically active azoaromatic polymers, containing in the side chain the rigid (S)- and/or (R)-hydroxysuccinimide residue, have been investigated in solution and in the solid state as thin films by observing the trans - cis photoisomerisation of the azobenzene chromophore, and the results are compared to the corresponding monomeric (S) and (R) model compounds. The presence of exciton splitting due to dipole-dipole interactions between the trans -azoaromatic rings in the CD spectra confirms the intrinsic chirality of the macromolecules. Thin films of the polymers display the same chiroptical properties as the solution, thus suggesting that the macromolecules maintain chiral conformations also in the solid amorphous state. [source] Molecular Junctions Composed of Oligothiophene Dithiol-Bridged Gold Nanoparticles Exhibiting Photoresponsive PropertiesCHEMISTRY - A EUROPEAN JOURNAL, Issue 2 2006Wei Huang Dr. Abstract Three oligothiophene dithiols with different numbers of thiophene rings (3, 6 or 9) have been synthesized and characterized. The X-ray single crystal structures of terthiophene 2 and sexithiophene 5 are reported herein to show the exact molecular lengths, and to explain the difference between their UV-visible spectra arising from the different packing modes. These dithiols with different chain lengths were then treated with 2-dodecanethiol-protected active gold nanoparticles (Au-NPs) by means of in situ thiol-to-thiol ligand exchange in the presence of 1,,m gap Au electrodes. Thus the molecular junctions composed of self-assembled films were prepared, in which oligothiophene dithiol-bridged Au-NPs were attached to two electrodes by means of AuS bonded contacts. The morphologies and current,voltage (I,V) characteristics of these films were studied by SEM and AFM approaches, which suggested that the thickness of the films (3,4 layers) varied within the size of one isolated Au-NP and typical distance-dependent semiconductor properties could be observed. Temperature dependent I,V measurements for these molecular junctions were performed in which the films served as active elements in the temperature range 6,300 K; classical Arrhenius plots and subsequent linear fits were carried out to give the activation energies (,E) of devices. Furthermore, preliminary studies on the photoresponsive properties of these devices were explored at 80, 160, and 300 K, respectively. Physical and photochemical mechanisms were used to explain the possible photocurrent generation processes. To the best of our knowledge, this is the first report in which oligothiophene dithiols act as bridging units to link Au-NPs, and also the first report about functionalized Au-NPs exhibiting photoresponse properties in the solid state. [source] Helically ,-Stacked Conjugated Polymers Bearing Photoresponsive and Chiral Moieties in Side Chains: Reversible Photoisomerization-Enforced Switching Between Emission and Quenching of Circularly Polarized FluorescenceADVANCED FUNCTIONAL MATERIALS, Issue 8 2010Hiroyuki Hayasaka Abstract Novel multifunctional conjugated polymers, [poly(p -phenylene)s and poly(bithienylene-phenylene)s with (R)- and (S)-configurations], which have fluorescence, chirality, and photoresponsive properties, have been designed and synthesized. The polymers are composed of ,-conjugated main chains, where poly(p -phenylene) and poly(bithienylene-phenylene) are fluorescence moieties, and the side chains of the photochromic dithienylethene moiety are linked with chiral alkyl groups. The polymer films exhibit right- or left-handed circularly polarized fluorescence (CPF) and also show reversible quenching and emitting behaviors as a result of photochemical isomerization of the dithienylethene moiety upon irradiation with ultraviolet and visible light. This is the first report realizing the reversible switching of CPF using chirality and photoresponsive properties. [source] Liquid-Crystalline Polymer with a Block Mesogenic Side Group: Photoinduced Manipulation of Nanophase-Separated StructuresADVANCED FUNCTIONAL MATERIALS, Issue 23 2009Kunihiko Okano Abstract In this report, a novel type of photoresponsive liquid crystalline polymer with a block mesogenic side-group is demonstrated. The block mesogene is an amphipathic molecule containing a hydrophobic mesogene (azotolane moiety) and hydrophilic oligooxyethylene moieties in the same unit. The block mesogene in the polymer plays a role in liquid crystalline, amphiphilic and photoresponsive properties. As expected, a film prepared from the polymer exhibits phase separation of a lamellar structure due to cooperative motion between liquid crystal assembly and nanophase separation. The morphology of the lamellae can be aligned upon irradiation of linearly polarized light. Moreover, a photochemical phase transition induced by unpolarized UV irradiation erases the surface morphology. The erased nanostructure can be recovered by annealing or irradiation of linearly polarized light, meaning that the surface morphology is rewritable via a photochemical process. [source] Phase behavior and photo-responsive studies of photoactive liquid crystalline hyperbranched polyethers containing benzylidene moietyJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 11 2009V. Srinivasa Rao Abstract Two sets of hyperbranched polyether epoxies were synthesized to study the effect of substituent, rigidity, and nature of photoactive unit on the thermal and photoresponsive properties. Each set was comprised of one molecule with an acyclic moiety in the repeating unit, and two molecules with a cyclic moiety of varying rigidity (cycle size) in the repeating unit. Two substituents on aromatic rings in the repeating unit were present in one set, and other set was without a substituent. The mesogenic and photoresponsive properties were studied and correlated to the varied structural parameters. The effects of varied molecular structural parameters on phase behavior and photoresponsive properties were very prominent. Out of six monomeric diols, only four have exhibited liquid crystalline phase while the polymers corresponding to all monomeric diols revealed mesophase. The findings in photoresponsive properties were further supported by molecular modeling studies. The changes in refractive index, photoviscosity, and fluorescence intensity with irradiation time substantiated the spectral pattern observed in UV-Vis spectroscopy. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 2774,2786, 2009 [source] Synthesis and characterization of side-chain liquid crystalline ABC triblock copolymers with p -methoxyazobenzene moieties by atom transfer radical polymerizationJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 13 2008Xiaohua He Abstract A series of novel side-chain liquid crystalline ABC triblock copolymers composed of poly(ethylene oxide) (PEO), polystyrene (PS), and poly[6-(4-methoxy-4,-oxy-azobenzene) hexyl methacrylate] (PMMAZO) were synthesized by atom transfer radical polymerization (ATRP) using CuBr/1,1,4,7,7-pentamethyldiethylenetriamine (PMDETA) as a catalyst system. First, the bromine-terminated diblock copolymer poly(ethylene oxide)- block -polystyrene (PEO-PS-Br) was prepared by the ATRP of styrene initiated with the macro-initiator PEO-Br, which was obtained from the esterification of PEO and 2-bromo-2-methylpropionyl bromide. An azobenzene-containing block of PMMAZO with different molecular weights was then introduced into the diblock copolymer by a second ATRP to synthesize the novel side-chain liquid crystalline ABC triblock copolymer poly(ethylene oxide)- block -polystyrene- block -poly[6-(4-methoxy-4,-oxy-azobenzene) hexyl methacrylate] (PEO-PS-PMMAZO). These block copolymers were characterized using proton nuclear magnetic resonance (1H NMR) and gel permeation chromatograph (GPC). Their thermotropic phase behaviors were investigated using differential scanning calorimetry (DSC) and polarized optical microscope (POM). These triblock copolymers exhibited a smectic phase and a nematic phase over a relatively wide temperature range. At the same time, the photoresponsive properties of these triblock copolymers in chloroform solution were preliminarily studied. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 4442,4450, 2008 [source] Photochromic and Photoresponsive Properties of Methacrylic Polymers Bearing Optically Active Hydroxysuccinimide in the Side ChainMACROMOLECULAR CHEMISTRY AND PHYSICS, Issue 21 2007Luigi Angiolini Abstract The photochromic and photoresponsive properties of a series of optically active azoaromatic polymers, containing in the side chain the rigid (S)- and/or (R)-hydroxysuccinimide residue, have been investigated in solution and in the solid state as thin films by observing the trans - cis photoisomerisation of the azobenzene chromophore, and the results are compared to the corresponding monomeric (S) and (R) model compounds. The presence of exciton splitting due to dipole-dipole interactions between the trans -azoaromatic rings in the CD spectra confirms the intrinsic chirality of the macromolecules. Thin films of the polymers display the same chiroptical properties as the solution, thus suggesting that the macromolecules maintain chiral conformations also in the solid amorphous state. [source] Synthesis, characterization and properties of azobenzene side-chain polythiophene,POLYMERS FOR ADVANCED TECHNOLOGIES, Issue 3-5 2003Leong Huat Gan Abstract Thiophene monomers with an azobenzene moiety of different spacer length at the 3-position of the thiophene ring were synthesized. The monomers were polymerized and copolymerized with 3-hexyl thiophene to investigate the influence of an azobenzene side-chain on the properties of polythiophene, which has been widely used as a conducting polymer and has also been found many other applications. The polymers were characterized with UV-vis, FT-IR spectrophotometry, gel permeation chromatographic (GPC) analysis, DSC, TGA, elemental analysis and X-ray diffractometry. The polymers showed novel thermochromic and photoresponsive properties in polymer solutions and solid films. It was found that an azobenzene side-chain could bring about substantial thermochromic and photochromic changes to the polythiophene backbone as compared with non-azobenzene side-chain polythiophenes. These property changes could be triggered or controlled by light or heat on the basis of azobenzene trans,cis or cis,trans isomerization. Copyright © 2003 John Wiley & Sons, Ltd. [source] Molecular Junctions Composed of Oligothiophene Dithiol-Bridged Gold Nanoparticles Exhibiting Photoresponsive PropertiesCHEMISTRY - A EUROPEAN JOURNAL, Issue 2 2006Wei Huang Dr. Abstract Three oligothiophene dithiols with different numbers of thiophene rings (3, 6 or 9) have been synthesized and characterized. The X-ray single crystal structures of terthiophene 2 and sexithiophene 5 are reported herein to show the exact molecular lengths, and to explain the difference between their UV-visible spectra arising from the different packing modes. These dithiols with different chain lengths were then treated with 2-dodecanethiol-protected active gold nanoparticles (Au-NPs) by means of in situ thiol-to-thiol ligand exchange in the presence of 1,,m gap Au electrodes. Thus the molecular junctions composed of self-assembled films were prepared, in which oligothiophene dithiol-bridged Au-NPs were attached to two electrodes by means of AuS bonded contacts. The morphologies and current,voltage (I,V) characteristics of these films were studied by SEM and AFM approaches, which suggested that the thickness of the films (3,4 layers) varied within the size of one isolated Au-NP and typical distance-dependent semiconductor properties could be observed. Temperature dependent I,V measurements for these molecular junctions were performed in which the films served as active elements in the temperature range 6,300 K; classical Arrhenius plots and subsequent linear fits were carried out to give the activation energies (,E) of devices. Furthermore, preliminary studies on the photoresponsive properties of these devices were explored at 80, 160, and 300 K, respectively. Physical and photochemical mechanisms were used to explain the possible photocurrent generation processes. To the best of our knowledge, this is the first report in which oligothiophene dithiols act as bridging units to link Au-NPs, and also the first report about functionalized Au-NPs exhibiting photoresponse properties in the solid state. [source] | ||||||||||