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Spiropyran

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https://www.readbyqxmd.com/read/28530723/precision-control-of-flow-rate-in-microfluidic-channels-using-photoresponsive-soft-polymer-actuators
#1
Colm Delaney, Peter McCluskey, Simon Coleman, Jeffrey Whyte, Nigel Kent, Dermot Diamond
A novel approach that allows control of flow in microfluidic channels with unsurpassed performance using light is described. Valve structures have been created using photoresponsive hydrogels based on spiropyran-functionalised pNIPAAm hydrogels photopolymerised around pillar structures within the channels. Valve actuation is controlled from outside the fluidic system using externally located LEDs. Highly precise and accurate flow rates can be selected by passing real-time flow rate measurements into a PID algorithm...
May 22, 2017: Lab on a Chip
https://www.readbyqxmd.com/read/28509916/systematic-variation-of-thiophene-substituents-in-photochromic-spiropyrans
#2
Dushanthi S Dissanayake, Gregory T McCandless, Mihaela C Stefan, Michael C Biewer
Spiropyrans are notable among different classes of photochromic compounds due to their large structural and electronic transformation upon isomerization. In order to parlay the electronic differences associated with the two isomeric forms into a materials based switch, the spiropyran ultimately requires a covalent attachment through a conjugated pathway. In this work a synthetic method was developed to incorporate spiropyran (SP) into thiophene based materials. A series of compounds with a systematic variation of substituents were synthesized (SP-T, SP-T-Br, SP-T-T, SP-T-T-T and SP-T-T-T-T-SP) and their photochromism in both polar (methanol) and non-polar (toluene) solvents were studied...
May 16, 2017: Photochemical & Photobiological Sciences
https://www.readbyqxmd.com/read/28443924/investigations-on-the-photochromic-properties-of-2-6-bis-5-bromo-2-hydroxybenzylidene-cyclohexanone
#3
L N Corîci, S Shova, V Badea, D Aparaschivei, O Costisor, L Cseh
The network of chemical reactions of 2,6-bis(5-bromo-2-hydroxybenzylidene)cyclohexanone (BHBC) when subjected to light and different pH values has been investigated. The pH dependent species involved in the chemical network have been identified and characterized by NMR and UV-VIS spectroscopy. Direct pH jumps were carried out by adding a strong acid to equilibrated solutions of trans-chalcone (Ct) forming the flavylium cation which was stable only under extremely acidic conditions (pH < 0.5). The single crystal X-ray study and NMR analysis has confirmed the structure of the new flavylium cation...
April 26, 2017: Photochemical & Photobiological Sciences
https://www.readbyqxmd.com/read/28425282/mechanical-force-sensitive-acrylic-latex-coating
#4
Meng Li, Weifeng Liu, Qi Zhang, Shiping Zhu
We prepared force sensitive acrylic latex coatings by covalently incorporating spiropyran mechanophore. The acrylic latexes were obtained through emulsion copolymerization of butyl acrylate (BA), methyl methacrylate (MMA) with vinyltriethoxysilane (VTES) as interparticle cross-linker, and (1'-(2-(methacryloyloxy)ethyl)-3',3'-dimethylspiro[chromene-2,2'-indolin]-6-yl)methyl methacrylate) (SP) as intraparticle cross-linker. The latexes of P(BA-co-MMA-co-SP-co-VTES) were subsequently cast onto Teflon-coated surface to form latex coatings...
April 21, 2017: ACS Applied Materials & Interfaces
https://www.readbyqxmd.com/read/28418112/photoresponsive-passive-micromixers-based-on-spiropyran-size-tunable-hydrogels
#5
Jeroen Ter Schiphorst, Giuseppe G Melpignano, Hossein Eslami Amirabadi, Menno H J M Houben, Sterre Bakker, Jaap M J den Toonder, Albertus P H J Schenning
Microfluidic devices allow the manipulation of fluids down to the micrometer scale and are receiving a lot of attention for applications where low volumes and high throughputs are required. In these micro channels, laminar flow usually dominates, which requires long residence times of the fluids, limiting the flow speed and throughput. Here a switchable passive mixer has been developed to control mixing and to easily clean microchannels. The mixer is based on a photoresponsive spiropyran based hydrogel of which the dimensions can be tuned by changing the intensity of the light...
April 18, 2017: Macromolecular Rapid Communications
https://www.readbyqxmd.com/read/28397485/large-area-cross-aligned-silver-nanowire-electrodes-for-flexible-transparent-and-force-sensitive-mechanochromic-touch-screens
#6
Seungse Cho, Saewon Kang, Ashish Pandya, Ravi Shanker, Ziyauddin Khan, Youngsu Lee, Jonghwa Park, Stephen L Craig, Hyunhyub Ko
Silver nanowire (AgNW) networks are considered to be promising structures for use as flexible transparent electrodes for various optoelectronic devices. One important application of AgNW transparent electrodes is the flexible touch screens. However, the performances of flexible touch screens are still limited by the large surface roughness and low electrical to optical conductivity ratio of random network AgNW electrodes. In addition, although the perception of writing force on the touch screen enables a variety of different functions, the current technology still relies on the complicated capacitive force touch sensors...
April 25, 2017: ACS Nano
https://www.readbyqxmd.com/read/28349141/synthesis-of-phenanthridine-spiropyrans-and-studies-of-their-effects-on-g-quadruplex-dna
#7
M Livendahl, J Jamroskovic, M Hedenström, T Görlich, N Sabouri, E Chorell
G-quadruplex (G4) DNA structures are involved in many important biological processes and can be linked to several human diseases. Drug-like low molecular weight compounds that target G4 structures are therefore interesting not only for their potential therapeutic properties but also for their potential use as chemical research tools. We report here on the development of methods to synthesize spiropyrans using a condensation-cyclisation reaction of quaternary salts of α-methyl quinoline or phenanthridine with salicylaldehydes...
April 11, 2017: Organic & Biomolecular Chemistry
https://www.readbyqxmd.com/read/28345857/self-cleaning-membranes-from-comb-shaped-copolymers-with-photoresponsive-side-groups
#8
Papatya Kaner, Xiaoran Hu, Samuel W Thomas, Ayse Asatekin
In this study, we present a novel self-cleaning, photoresponsive membrane that is capable of removing predeposited foulant layers upon changes in surface morphology in response to UV or visible light irradiation while maintaining stable pore size and water permeance. These membranes were prepared by creating thin film composite (TFC) membranes by coating a porous support membrane with a thin layer of novel comb-shaped graft copolymers at two side-chain lengths featuring polyacrylonitrile (PAN) backbones and photoreactive side chains, synthesized by atom transfer radical polymerization (ATRP)...
April 5, 2017: ACS Applied Materials & Interfaces
https://www.readbyqxmd.com/read/28326771/shuttling-motion-in-a-host-guest-complex-triggered-by-spiropyran-to-merocyanine-reversible-chemical-transformation
#9
Denhy Hernández-Melo, Ruy Cervantes, Jorge Tiburcio
A stimulus-responsive guest-containing spiropyran and viologen unit assembles with a 24-membered crown ether into a stable host-guest complex displaying a partially threaded geometry. Acid addition induces guest transformation to a merocyanine species activating a second recognition site, suitable for the formation of a pseudorotaxane. The simultaneous presence of two recognition sites produces a small-amplitude macrocycle shuttling motion, from the viologen to the merocyanine moiety. Base addition returns the guest to its spiropyran form, and concurrently the translation motion stops...
March 30, 2017: Journal of Organic Chemistry
https://www.readbyqxmd.com/read/28301170/substituent-correlations-characterized-by-hammett-constants-in-the-spiropyran-merocyanine-transition
#10
Oliver Brügner, Thomas Reichenbach, Michael Sommer, Michael Walter
The modification of molecular properties by the use of substituents is a versatile route for molecular design. Here we show for the example of multiresponsive spiropyrans that substituent effects and their correlations can be accurately described by Hammett constants, which in turn can be obtained directly from density functional theory calculations. The internal energetic difference ΔU between the noncolored and the colored form is determined for 63 spiropyran derivatives with substituents at the spiropyran N- and C6-positions, and can be described by only five parameters with an accuracy better than 0...
March 24, 2017: Journal of Physical Chemistry. A
https://www.readbyqxmd.com/read/28295677/a-novel-design-of-multi-mechanoresponsive-and-mechanically-strong-hydrogels
#11
Hong Chen, Fengyu Yang, Qiang Chen, Jie Zheng
A newly developed polyacrylamide-co-methyl acrylate/spiropyran (SP) hydrogel crosslinked by SP mechanophore demonstrates multi-stimuli-responsive and mechanically strong properties. The hydrogels not only exhibit thermo-, photo-, and mechano-induced color changes, but also achieve super-strong mechanical properties (tensile stress of 1.45 MPa, tensile strain of ≈600%, and fracture energy of 7300 J m(-2) ). Due to a reversible structural transformation between spiropyran (a ring-close) and merocyanine (a ring-open) states, simple exposure of the hydrogels to white light can reverse color changes and restore mechanical properties...
March 15, 2017: Advanced Materials
https://www.readbyqxmd.com/read/28266210/reversible-light-switching-of-enzymatic-activity-on-orthogonally-functionalized-polymer-brushes
#12
Matthias Dübner, Victor J Cadarso, Tugce N Gevrek, Amitav Sanyal, Nicholas D Spencer, Celestino Padeste
Copolymer brushes, composed of glycidyl methacrylate and a furan-protected maleimide-containing monomer, were grafted from radical initiators at the surface of irradiation-activated fluoropolymer foils. After postpolymerization modification with enzymatically active microperoxidase-11 and photochromic spiropyran moieties, the polymer brushes catalyzed the oxidation of 3,3'5,5'-tetramethylbenzidine. Exposure to either UV or visible-light allowed switching the turnover by more than 1 order of magnitude, as consequence of the reversible, light-induced spiropyran-merocyanine transition...
March 22, 2017: ACS Applied Materials & Interfaces
https://www.readbyqxmd.com/read/28110068/a-photoresponsive-soft-interface-reversibly-controls-wettability-and-cell-adhesion-by-conformational-changes-in-a-spiropyran-conjugated-amphiphilic-block-copolymer
#13
Di He, Yoshinori Arisaka, Kenichi Masuda, Mitsuya Yamamoto, Naoya Takeda
The functionalities of soft interfaces including cell adhesion can be enhanced by dynamic conversion of polymer properties and movement via external stimuli. Light is a superior stimulus, and various surfaces modified with photoreactive molecules have been prepared. However, in most of these studies, the surface properties are irreversibly changed due to photo-degradation, and reversible adhesion and collection of cells is not feasible. In this study, we developed a photoresponsive polymer soft interface that was able to spatiotemporally control wettability, cell adhesion, and detachment in a reversible manner...
January 18, 2017: Acta Biomaterialia
https://www.readbyqxmd.com/read/28079224/suitability-of-n-propanoic-acid-spiropyrans-and-spirooxazines-for-use-as-sensitizing-dyes-in-dye-sensitized-solar-cells
#14
Noah M Johnson, Yuriy Y Smolin, Daniel Hagaman, Masoud Soroush, Kenneth K S Lau, Hai-Feng Ji
This work deals with the fabrication and evaluation of color-changing dye-sensitized solar cells (DSSCs) that include N-propanoic acid-functionalized spiropyrans and spirooxazines as sensitizing dyes. We investigated the photophysical properties of these compounds in various solvents and pH conditions using UV-Vis spectroscopy, and their behavior on TiO2 photoanode surfaces using a combination of UV-Vis and FT-IR. Their performance as sensitizing dyes for DSSCs was also analyzed. This study revealed a number of unique properties for this class of compounds that affect their performance as both photochromic compounds and DSSC sensitizers, which allow for future creation of efficient photochromic DSSCs...
January 12, 2017: Physical Chemistry Chemical Physics: PCCP
https://www.readbyqxmd.com/read/28042662/water-soluble-spiropyrans-with-inverse-photochromism-and-their-photoresponsive-electrostatic-self-assembly
#15
Daniel Moldenhauer, Franziska Gröhn
A new type of light responsive nanoscale assemblies based on water-soluble spiropyrans is presented. We have synthesized four anionic spiropyrans bearing multiple sulfonate groups and investigated their photochromic behavior in aqueous solution. Depending on the pH, either inverse photochromism (acidic conditions) or normal photochromism (alkaline conditions) is found. Kinetic data for the interconversion of the spiropyran and merocyanine isomers including the subsequent slow hydrolysis have been obtained by UV/Vis spectroscopy...
January 1, 2017: Chemistry: a European Journal
https://www.readbyqxmd.com/read/27987981/photochromic-paper-from-wood-pulp-modification-via-layer-by-layer-assembly-of-pulp-fiber-chitosan-spiropyran
#16
Xiaojun Tian, Bin Wang, Jinpeng Li, Jinsong Zeng, Kefu Chen
Cellulosic fiber introducing with photochromic properties can be used in many fields such as security packaging, printing paper, and rewritable paper. To introduce photochromic property to individual fiber, a polyelectrolyte composite layer composed of cationic chitosan (CS) and anionic carboxyl-containing spiropyran (SPCOOH) on pulp fibers was designed using layer-by-layer assembly technique. Scanning electron microscope observation showed that the SPCOOH was successfully absorbed onto the surface of fiber...
February 10, 2017: Carbohydrate Polymers
https://www.readbyqxmd.com/read/27889853/photo-physical-behavior-and-fluorescence-of-thermo-switchable-nanocomposite-based-on-methyl-methacrylate-spirobenzopyran
#17
Shohre Rouhani, Malihe Pishvaei
Nanocomposites with thermo and photo-switchable fluorescent properties were synthesized via mini-emulsion polymerization based on spiropyran and methyl methacrylate monomer. The photophysical behavior of fluorescence nanocomposites was investigated by fluorescence spectrophotometry in different temperature, UV-light and time of exposure. It was found that methyl methacrylate polymer is capable of acting as a protective layer and play a critical role in improving the photostability of colorants. The nanocomposites exhibited excellent fluorescent thermo-switching action with respect to the free spiro molecule...
November 26, 2016: Journal of Fluorescence
https://www.readbyqxmd.com/read/27830865/controlling-the-lifetimes-of-dynamic-nanoparticle-aggregates-by-spiropyran-functionalization
#18
Pintu K Kundu, Sanjib Das, Johannes Ahrens, Rafal Klajn
Novel light-responsive nanoparticles were synthesized by decorating the surfaces of gold and silver nanoparticles with a nitrospiropyran molecular photoswitch. Upon exposure to UV light in nonpolar solvents, these nanoparticles self-assembled to afford spherical aggregates, which disassembled rapidly when the UV stimulus was turned off. The sizes of these aggregates depended on the nanoparticle concentration, and their lifetimes could be controlled by adjusting the surface concentration of nitrospiropyran on the nanoparticles...
November 10, 2016: Nanoscale
https://www.readbyqxmd.com/read/27819106/accidental-degeneracy-in-the-spiropyran-radical-cation-charge-transfer-between-two-orthogonal-rings-inducing-ultra-efficient-reactivity
#19
David Mendive-Tapia, Luuk Kortekaas, Jorn D Steen, Aurélie Perrier, Benjamin Lasorne, Wesley R Browne, Denis Jacquemin
Photochromism of the spiropyran radical cation to the corresponding merocyanine form is investigated by a combination of electrochemical oxidation, UV/vis absorption spectroscopy, spectroelectrochemistry and first-principles calculations (TD-DFT, CAS-SCF and CAS-PT2). First, we demonstrate that the ring-opening of mono-spiropyrans occurs upon one-electron oxidation and that it can be driven photochemically as well as thermally, with trapping of the merocyanine by protonation. Second, in order to explain this experimentally observed spectroelectrochemical behaviour we suggest a theoretical mechanism based on the reactivity of the two lowest electronic excited-states, which promotes effective electron transfer from the indoline (nitrogen-ring) to the pyran (oxygen-ring) moieties (and vice versa) through a conical intersection seam of degeneracy...
November 16, 2016: Physical Chemistry Chemical Physics: PCCP
https://www.readbyqxmd.com/read/27791322/temperature-controlled-switchable-photochromism-in-solid-materials
#20
Alex Julià-López, Jordi Hernando, Daniel Ruiz-Molina, Pablo González-Monje, Josep Sedó, Claudio Roscini
A novel strategy to achieve thermally switchable photochromism in solid materials is reported, which relies on the preparation of polymeric core-shell capsules containing solutions of photochromic dyes in acidic phase-change materials. Upon changing the phase (solid or liquid) of the encapsulated medium, one of the two photochromic states of the system is selectively stabilized on demand, allowing for reversible interconversion between direct and reverse photochromism when thermally scanning through the melting temperature of the phase-change material...
October 28, 2016: Angewandte Chemie
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