			Home About us Contact

Reversible Switching (reversible + switching)

Distribution by Scientific Domains

Polymers and Materials Science	61%
Chemistry	38%

Selected Abstracts

Reversible Switching of Water-Droplet Mobility on a Superhydrophobic Surface Based on a Phase Transition of a Side-Chain Liquid-Crystal Polymer

ADVANCED MATERIALS, Issue 42 2009
Chao Li
Reversible switching of the mobility of a water microdroplet between rollable and pinned simply by changing the temperature is realized by coordination of the phase transition of a side-chain liquid-crystal polymer (SCLCP) with optimized surface roughness of a superhydrophobic surface. The responsive surface has potential applications in microreactor design and microfluidic control systems. [source]

Nanometer-Range Communication of Stereochemical Information by Reversible Switching of Molecular Helicity,

ANGEWANDTE CHEMIE, Issue 38 2010
Dr. Jordi Solà
Ein Ferngespräch: Die Inversion der Konfiguration eines stereogenen Zentrums verursachte eine nachweisbare Änderung der Position einer 40,Bindungen (2.5,nm) entfernten stereochemischen 13C-Sonde. Die Information wurde wie illustriert über eine Inversion des Schraubensinns der dazwischenliegenden Helix übermittelt. 13C-NMR-Signale dienten als Ausgabe. [source]

Water-Vapor-Induced Reversible Switching of Electronic States in an MMX-Type Chain Complex with Retention of Single Crystallinity,

ANGEWANDTE CHEMIE, Issue 3 2010
Hiroaki Iguchi
Eine reversible Strukturänderung und Änderungen der physikalischen Eigenschaften eines zweikernigen Quasi-1D-Pt-Komplexes werden durch De- und Rehydratisierung ausgelöst. Beim Dehydratisieren geht der elektronische Zustand von einem ACP+CDW- (ACP: alternierende Ladungspolarisierung, CDW: Ladungsdichtewellen) in einen CDW-Zustand mit enger Lücke über, wobei die elektrische Leitfähigkeit und die molare Spinsuszeptibilität bei Raumtemperatur zunehmen. [source]

Two-Color Reversible Switching in a Photochromic Ruthenium Sulfoxide Complex,

ANGEWANDTE CHEMIE, Issue 45 2009
Anne McClure
Strahlungsempfänglich: Ein reversibler photochromer Mechanismus wird für den Komplex [Ru(bpy)2(pySO)]2+ (bpy=2,2,-Bipyridin, pySO=2-(Isopropylsulfinylmethyl)pyridin) vorgestellt. Die Isomerisierung von der S-gebundenen (blau im Bild) zur O-gebundenen Form (rot) erfolgt bei Anregung mit UV-Licht mit einer Zeitkonstanten , von 1.5,ns (,=0.11); für den umgekehrten Prozess gilt ,=6.3,ns (,=0.027). [source]

Electrochemical Nanotransistor from Mixed-Polymer Brushes

ADVANCED MATERIALS, Issue 16 2010
Tsz Kin Tam
Reversible switching of the electrode interface between OFF/ON states is achieved by electrochemically triggered reorganization of a nanostructured polymer brush associated with the interface. The switching process is accomplished by local interfacial pH changes allowing operation in buffered biological environments (see figure). The fabricated device mimics the performance of switching electronic devices such as transistors. [source]

Reversible Switching of Water-Droplet Mobility on a Superhydrophobic Surface Based on a Phase Transition of a Side-Chain Liquid-Crystal Polymer

Reversible Superhydrophobicity to Superhydrophilicity Transition by Extending and Unloading an Elastic Polyamide Film

MACROMOLECULAR RAPID COMMUNICATIONS, Issue 6 2005
Jilin Zhang
Abstract Summary: Reversible switching between superhydrophobic and superhydrophilic wettability of a polyamide film with a triangular net-like structure can be achieved by biaxially extending and unloading the elastic film. Both the change of the average side-length of the triangular net-like structure upon biaxial extension and unloading, and the surface tension of the water droplet, are believed to be responsible for the reversible switching between superhydrophobicity and superhydrophilicity. Change in structure and wettability of the triangular net-like polyamide film upon extension and unloading. [source]

Electrochemically Induced Modulation of the Catalytic Activity of a Reversible Redoxsensitive Riboswitch

ELECTROANALYSIS, Issue 9 2008
Denise Strohbach
Abstract Over the past decade, RNA conformation has been shown to respond to external stimuli. Thus, dependent on the presence of a high affinity ligand, specifically designed ribozymes can be regulated in a classical allosteric way. In this scenario, a binding event in one part of the RNA structure induces conformational changes in a separated part, which constitutes the catalytic centre. As a result activity is switched on (positive regulation) or off (negative regulation). We have developed a hairpin aptazyme responding to flavine mononucleotide (FMN). Ribozyme activity is dependent on binding of FMN and thus is switched on in the presence of FMN in its oxidized form. Under reducing conditions, however, FMN changes its molecular geometry, which is associated with loss of binding and consequently down-regulation of ribozyme activity. While in previous experiments sodium dithionite was used for reduction of FMN, we now present an assay for electrochemically induced activity switching. We have developed an electrochemical microcell that allows for iterative cycles of reduction/oxidation of FMN in an oxygen free atmosphere and thus for reversible switching of ribozyme activity. The reaction proceeds in droplets of 3 to 10,,L at micro- to nanomolar concentrations of the reaction components. [source]

Photoswitchable Gas Permeation Membranes Based on Liquid Crystals

ADVANCED FUNCTIONAL MATERIALS, Issue 17 2010
Eric G, owacki
Abstract We have fabricated switchable gas permeation membranes in which a photoswitchable low-molecular-weight liquid crystalline (LC) material acts as the active element. Liquid crystal mixtures are doped with mesogenic azo dyes and infused into commercially available track-etched membranes with regular cylindrical pores (0.40 to 10.0 ,m). Tunability of mass transfer can be achieved through a combination of (1) LC/mesogenic dye composition, (2) surface-induced alignment, and (3) reversible photoinduced LC-isotropic transitions. Photo-induced isothermal phase changes in the imbibed material afford large and fully reversible changes in the permeability of the membrane to nitrogen. Both the LC and photogenerated isotropic states demonstrate a linear permeability/pressure relationship, but they show significant differences in their permeability coefficients. Liquid crystal compositions can be chosen such that the LC phase is more permeable than the isotropic,or vice versa , and can be further tuned by surface alignment. Permeability switching response times are 5 s, with alternating UV and >420-nm radiation at an intensity of 2 mW/cm2 being sufficient for complete and reversible switching. Thermal and kinetic properties of the confined LC materials are evaluated and correlated with the observed permeation properties. We demonstrate for the first time reversible permeation control of a membrane with light irradiation. [source]

Helically ,-Stacked Conjugated Polymers Bearing Photoresponsive and Chiral Moieties in Side Chains: Reversible Photoisomerization-Enforced Switching Between Emission and Quenching of Circularly Polarized Fluorescence

ADVANCED FUNCTIONAL MATERIALS, Issue 8 2010
Hiroyuki 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]

Reversible Conductance Switching of Single Diarylethenes on a Gold Surface,

ADVANCED MATERIALS, Issue 11 2006
N. Katsonis
Light-controlled conductance switching of diarylethenes attached to Au(111) is reported (see figure). First, scanning tunneling microscopy is used to demonstrate reversible photoswitching for individual molecules. Second, reversible switching in self-assembled monolayers is established by means of optical spectroscopy. [source]

Reversible Superhydrophobicity to Superhydrophilicity Transition by Extending and Unloading an Elastic Polyamide Film

Photochemical Z,E Isomerization of a Hemithioindigo/Hemistilbene ,-Amino Acid

CHEMPHYSCHEM, Issue 11 2007
Thorben Cordes
Abstract The molecule HTI, which combines hemithioindigo and hemistilbene molecular parts, allows reversible switching between two isomeric states. Photochromic behaviour of the HTI molecule is observed by irradiation with UV/Vis light. The photochemical reaction, a Z/E isomerization around the central double bond connecting the two molecular parts, is investigated by transient absorption and emission spectroscopy. For a special HTI molecule, namely, an ,-amino acid, the Z,E isomerization process occurs on a timescale of 30 ps. In the course of the reaction fast processes on the 1,10 ps timescale are observed which point to motions of the molecule on the potential-energy surface of the excited state. The combination of transient absorption experiments in the visible spectral range with time-resolved fluorescence and infrared measurements reveal a photochemical pathway with three intermediate states. Together with a theoretical modelling procedure the experiments point to a sequential reaction scheme and give indications of the nature of the involved intermediates. [source]