Search results for "Azobenzene"
showing 10 items of 84 documents
One is Enough: Influencing Polymer Properties with a Single Chromophoric Unit
2011
1) Institute for Technical and Macromolecular Chemistry, University of Hamburg, Bundesstrasse 45, D-‐20146 Hamburg, Germany 2) WCU program of C2E2, School of Chemical and Biological, Engineering, College of Engineering, Seoul National University, Seoul, Korea Designing a polymer usually involves the incorporation of multiple functional units into a polymer chain, which mutually determine the polymer properties. By combining various functional units, a myriad of polymer properties can be fine-‐ tuned. Classical polymer chemistry teaches us that a single functional group -‐-‐ in particular the end-‐group of a polymer chain -‐-‐ does not contribute to the polymer properties, as is indee…
Photoresponsive Ferroelectric Liquid-Crystalline Polymers
2007
The photoresponse of ferroelectric smectic side-chain liquid-crystalline (LC) polymers containing a photoisomerizable azobenzene derivative as a covalently linked photochromic side group is investigated. By static measurements in different photostationary states, the effect of trans-cis isomerization on the material's phase-transition temperatures and its ferroelectric properties (spontaneous electric polarization Ps and director tilt angle 0) are analyzed. It turns out that the Curie temperature (transition S C * to S A ) can be reversibly shifted by up to 17 °C. The molecular mechanism of this "photoferroelectric effect" is studied in detail using time-resolved measurements of the dye's o…
Photoreactive Langmuir–Blodgett–Kuhn multilayer assemblies from functionalized liquid-crystalline side chain polymers, I. Homopolymers containing azo…
1991
Stable monomolecular layers of a liquid-crystalline homopolymer bearing azobenzene chromophores in the mesogenic side groups could be prepared at the water–air interface by slow compression at room temperature. From the area per monomer unit of A0≈0.25 nm2 a structural model with tightly packed azobenzene groups oriented nearly parallel to the surface normal was deduced. After transfer to a solid support in a Y-type mode the obtained Langmuir–Blodgett–Kuhn (LBK) multilayer assemblies of varying thicknesses (from a double layer to a thick film of d = 238 nm, capable of guiding optical modes) were prepared and analyzed by X-ray reflection and optical evanescent wave techniques. A monolayer th…
Thermo- and light responsive micellation of azobenzene containing block copolymers
2010
In this communication, the synthesis and characterization of thermo- and light responsive block copolymers is reported. PEO-b-PNIPAM polymers with azobenzene moieties were prepared and analyzed by turbidimetry, fluorescence, NMR and DLS measurements. A temperature controlled reversible formation as well as a light induced disruption and reformation of micellar structures in water was found.
Semicarbazides as gel forming agents for common solvents and liquid crystals
2006
This paper describes the synthesis of 14 new gelling agents with semicarbazide groups as H-bonding motifs and alkyl- and/or azobenzene side groups. They gel solvents like decaline, 1,2-dichlorobenzene and toluene and liquid crystalline mixtures. X-Ray structure analysis shows that the semicarbazides are connected by H-bonds, each molecule to four neighbours. As a result a ribbon is formed with a core of H-bonded semicarbazide groups and alkyl chains sticking to the side. IR measurements show an unchanged H-bonding motif in large crystals and in the gel fibres, even in LC-mixture. During heating the gel melts (rheology), while the H-bonding motif of the crystal disappears (IR and DSC measure…
Polymers films with indandione derivatives as alternatives to azobenzene polymers for optical patterning
2008
Surface relief gratings (SRGs) on organic thin films are studied extensively for both scientific interest and in relevance to the applications. Among the chromophores being used the azobenzenes showed the best performance, but the use of alternative photo-sensitive groups provides better general understanding of the phenomena. A thermodynamic theory and molecular dynamics simulations of photoinduced effects are discussed. In this study we use indandione derivatives, known as promising materials for photonics applications, as an alternative to the azobenzenes. We consider their photoreactions when incorporated into a polymer film. One of interesting features is the spectral dependence of the…
Photoelectrical properties of indandione fragment containing azobenzene compounds
2014
Organic materials are becoming more popular due to their potential application in electronics. Low molecular weight materials possible produce from solution are in special consideration. It gives the possibility to avoid both thermal evaporation in vacuum, and use of polymers in thin film preparation process. Indandione fragment containing azobenzene compounds are one of such materials. These compounds are good candidates for use in design of novel molecular electronic devices due to their possibility to form amorphous structure from solution thus allowing developing flexible, small size systems with low production costs. In this work three indandione fragment containing azobenzene compound…
<title>Optically induced switching of dicyclohexylamino substituted azobenzene derivatives in thin ordered films</title>
2005
During the last years, there has been an increasing interest in the photoinduced switching effects. Among the objects of concern azobenzene derivatives, isomerizing under UV and visible light, occupy a prominent position. To understand the photoresponse of these materials in the condensed phase, their spectroscopic and electrical properties are studied. It is shown that the photoresponse depends on the orientation of the molecules and their packing. A number of novel azobenzene derivatives containing a N,N-dicyclohexyl sulfonamide moiety is synthesized. The derivatives differ in the length of alkyl chains between the azobenzene moiety and SH or COOH groups. The morphology and the photoinduc…
Photoinduced switching of electrical properties in thin films of polar indandione type organic molecules
2006
The optically induced switching of organic materials with large dipole moments consisting of acceptor and donor groups bridged by a delocalized π-electron system is important for investigations of optoelectronic effects. To the contrary of azobenzene molecule, photoinduced change of dipole moment of indandione molecule does not need free volume in thin films. To modify the dipole moment and also to optimise properties of film formation, a number of novel indandione derivatives is investigated. Reversible switching of the surface potential of polymer films with incorporated or chemically attached indandione molecules is observed at irradiation in photoinduced intramolecular electron transfer…
An improved molecular design of obtaining NLO active molecular glasses using triphenyl moieties as amorphous phase formation enhancers
2012
New molecular design of obtaining molecular glasses has been developed by linking triphenylmethyl moieties to chromophore core by flexible C-C bridge. Compounds capable of forming stable amorphous phase with good optical quality have been acquired with increased chemical and thermal sustainability compared to the previously reported design. NLO activity of compounds has been measured after corona discharge polling. Compared to previously synthesized trityloxy fragment containing compounds increase of d 33 coefficient by up to 17 times was achieved for the same chromophore core containing compounds.