Photochromic Kinetics Research Articles

Metallic-Ion Controlled Dynamic Bonds to Co-Harvest Isomerization Energy and Bond Enthalpy for High-Energy Output of Flexible Self-Heated Textile.

Molecular light‐harvesting capabilities and the production of low‐temperature heat output are essential for flexible self‐heated textiles. An effective strategy to achieve these characteristics is to introduce photoresponsive molecular interactions (photodynamic bonds) to increase the energy storage capacity and optimize the low‐temperature photochromic kinetics. In this study, a series of sulfonic‐grafted azobenzene‐based polymers interacted with different metal ions (PAzo‐M, M = Mg, Ca, Ni, Zn, Cu, and Fe) to optimize the energy level and isomerization kinetics of these polymers is designed and prepared. Photoinduced formation and dissociation of M—O dynamic bonds enlarge the energy gap (∆E) between trans and cis isomers for high‐energy storage and favor a high rate of isomerization for low‐temperature heat release. The suitable binding energy and high ∆E enable PAzo‐M to store and release isomerization energy and bond enthalpy even in a low‐temperature (−5 °C) environment. PAzo‐Mg possesses the highest energy storage density of 408.6 J g−1 (113.5 Wh kg−1). A flexible textile coated with PAzo‐Mg can provide a high rise in temperature of 7.7–12.5 °C in a low‐temperature (−5.0 to 5.0 °C) environment by selectively self‐releasing heat indoors and outdoors. The flexible textile provides a new pathway for wearable thermal management devices.

Light- and temperature-responsive micellar carriers prepared by spiropyran-initiated atom transfer polymerization: Investigation of photochromism kinetics, responsivities, and controlled release of doxorubicin

Stimuli-responsive block copolymer assemblies are a significant class of smart materials extensively studied for advanced applications such as drug- and gen-delivery systems. Different types of light- and temperature-responsive polymer assemblies containing photochromic spiropyran chain end groups, temperature-responsive poly (N-isopropylacrylamide) (PNIPAM) block, and hydrophobic poly (methyl methacrylate) (PMMA) block were developed. These amphiphilic block copolymers with the ability of self-assembly to micellar structures were synthesized using spiropyran-initiated atom transfer radical polymerization. Regarding the hydrophilic fraction (0.5<fphilic), the amphiphilic block copolymers were self-assembled to spherical micelles in aqueous media as confirmed by TEM images. The size of these polymer assemblies was changed in response to temperature changes and also UV light (365 nm) irradiation. The results of UV–Vis spectroscopy display that photochromic behavior, the kinetics of spiropyran (SP) to merocyanine (MC) and MC to SP isomerizations were significantly affected by the polarity of the polymer blocks in neighboring of the spiropyran chain end group. The lower critical solution temperature (LCST) of PNIPAM shows a shift from 26.5 to 37.5 °C after isomerization of the SP to MC, as a result of increase of its polarity and water-solubility. The doxorubicin (DOX) release can be controlled by pH, temperature, and light by using of multi-responsive block copolymer micelles as smart drug carriers. The release efficiency was reached to 60–85% at pH 5.3, 80–90% at temperatures of above LCST of PNIPAM (40 °C), and also 90–100% under UV irradiation after 48 h. The results display that stimuli-responsive polymer assemblies based on amphiphilic block copolymers containing spiropyran chain end groups are applicable in smart drug-delivery systems, and offer controlling over drug-release by different triggers, such as light irradiation, pH variation, and temperature changes.

Synthesis and Photochromism Studies of 1-(3,5-dimethyl-4-isoxazole)-2-[2-methyl-5-naphthyl-3-thienyl] perfluorocyclopentene

A new class of unsymmetrical photochromic diarylethene bearing an isoxazole moiety was synthesized. Its photochemical properties, including photochromic behavior and kinetics, have been investigated systematically. The result indicated that the Diarylethene 1a changed the color from colorless to pink irradiation with 297 nm UV light, in which absorption maxima were observed at 522 nm in hexane. The photochromic reaction kinetics indicated that the cyclization processes of 1a belong to the zeroth order reaction and the cycloreversion process belong to the first order reaction.

Synthesis and Photochromism Studies of 1-(2,5-Dimethyl-3-Thienyl)-2-[2-Methyl-5-Naphthyl-3-Thienyl] Perfluorocyclopentene

A novel photochromic diarylethene 1a has been synthesized. Its photochemical properties, including photochromic behavior and kinetics, have been investigated in detail. The result indicated that the Diarylethene 1a changed the color from colorless to pink irradiation with 297 nm UV light, in which absorption maxima were observed at 548 nm in hexane. The photochromic reaction kinetics indicated that the cyclization processes of 1a belong to the zeroth order reaction and the cycloreversion process belong to the first order reaction. The back irradiation by appropriate wavelength visible light regenerated its open-ring isomers and recovered the original emission intensity.

Synthesis and Properties of a New Diarylethene1-[2-methyl-5-(10-phenanthrenyl)-3-thienyl]-2-[2-methyl-5-(4-formylphenyl)-3-thienyl]perfluorocyclopentene

A new photochromic diarylethene based on a phenanthrene, which is named 1-[2-methyl-5-(10-phenanthrenyl)-3-thienyl]-2-[2-methyl-5-(4-formylphenyl)-3-thienyl] perfluorocyclopentene, was designed and constructed successfully. At the same time, its photochromic properties, kinetics and fluorescence switch were investigated in detail. The results indicated that its photochromic behaviors could be modulated by UV/Vis light, changing from colorless to blue in dichloromethane solution. What is more, the kinetic experiments illustrated that the cyclization/cycloreversion process of this compound was determined to be the zeroth/first reaction. Furthermore, the optical switch experiment illustrated that the diarylethene1ofunctioned as a remarkable fluorescent switch.

IR-stimulated visible fluorescence in pink and brown diamond

Irradiation of natural pink and brown diamond by middle-ultraviolet light (photon energy ϵ ≥ 4.1 eV ) is seen to induce anomalous fluorescence phenomena at N3 defect centres (structure N3−V). When diamonds primed in this fashion are subsequently exposed to infrared light (even with a delay of many hours), a transient burst of blue N3 fluorescence is observed. The dependence of this IR-triggered fluorescence on pump wavelength and intensity suggest that this fluorescence phenomena is intrinsically related to pink diamond photochromism. An energy transfer process between N3 defects and other defect species can account for both the UV-induced fluorescence intensity changes, and the apparent optical upconversion of IR light. From this standpoint, we consider the implications of this N3 fluorescence behaviour for the current understanding of pink diamond photochromism kinetics.

Synthesis and photochromic properties of novel spiro[indoline-quinoline]oxazine derivatives

A series of novel spirooxazine derivatives containing nitrogen heterocycles have been synthesized and characterized by 1H NMR, 13C NMR, IR and HRMS in this paper, and the photochromic behaviors of the compounds have been studied in different solutions and the compounds were embedded into a poly(methylmethacrylate) and poly(vinyl butyral) matrix (PMMA, PVB). In solutions, they showed thermochromism and acidichromism. Embedded into polymeric films, the photochromic kinetics of the thermal decoloration of the compounds significantly changed and it was found that the decoloration curves fitted biexponential function. Detailed studies showed that representative compound 1 [1,3,3-trimethyl-6′-piperidino-spiro(indoline-2,3′-[3H]-quinolino[2,1-b][1,4]oxazine)] exhibited high fatigue resistance in poly(methylmethacrylate) and poly(vinyl butyral) matrix.

Synthesizes and Properties of 1-[2-methyl-5-(4-methoxyphenyl)-3-thieny-2-[2-methyl-5-(3-methoxy-4-formyphenyl)-3-thienyl] perfluorocyclopentene

A new unsymmetrical photochromic diarylethene compound, namely 1-[2-methyl-5-(4-methoxyphenyl)-3-thieny-2-[2-methyl-5-(3-methoxy-4-formyphenyl)-3-thieny perfluorocyclopentene, was synthesized and its properties were investigated in detail, including photochromic reactivity kinetics and concentration effect. The results showed that the compound exhibited remarkable photochromism, changing between colorless and blue in solution, respectively. What is more, the kinetic experiments illustrated that the cyclization/cycloreversion process of this compound was determined to be the zeroth/first reaction.

Photochromic and Kinetics Properties of a New Symmetrical Diarylethene Containing a Terminal Hydroxyl

A symmetrical photochromic diarylethene1ahas been synthesized. Its photochemical properties, including photochromic behavior and kinetics, have been investigated in detail. The compound showed good photochromism both in solution and in solid state. The back irradiation by appropriate wavelength visible light regenerated its open-ring isomers and recovered the original emission intensity. Using diarylethene1aas recording medium, polarization holographic optical recording was carried out successfully.

Synethesis and Properties of 1-(2-trifluoromethylphenyl)-2-[2-methyl-5-(3-N,N-dimethylphenyl)-3-thienyperfluorocyclopentene

An unsymmetrical photochromic diarylethene 1-(2-trifluoromethylphenyl)-2-[2-methyl-5-(3-N,N-dimethylphenyl)-3-thienyperfluorocyclopentene (1a) was synthesized and its photochromism, fluorescent properties and reaction kinetics of cyclization and cycloreversion were studied in detail. The compound exhibited remarkable photochromism and its absorption maxima were observed at 552 nm in hexane and at 569 nm in PMMA films upon irradiation with 297 nm UV light. The fluorescence intensity of diarylethene decreased upon irradiation with 297 nm UV light. In addiation, reaction kinetics of the cyclization and cycloreversion processes of the compound were determined to be the zeroth and first order reaction by UV-Vis spectra, respectively.

Photochromic Kinetics of a Diarylethene Bearing an Azido Moiety in Solution and in PMMA Amorphous Film

A new photoinduced fluorescent switch based on a photochromic diarylethene, 1-(2-methyl-3-benzothiophenyl)-2-[2-methyl-5-(4-azidomethylphenyl)-3-thienyperfluorocyclope-ntene was synthesized and its photochromism was investigated. The results showed that this compound exhibited reversible photochromism, changing from colorless to purple upon irradiation with UV light both in solution and in PMMA amorphous film. In acetonitrile, the open-ring isomer of the diarylethene1oexhibited relatively strong fluorescence at 473 nm when excited at 320 nm. The results demonstrated that the diarylethene can be also functioned as a fluorescence switch.

Synthesis, Photochromic Properties of a Novel Unsymmetrical Hybrid Diarylethene Material with Benzene Unit

A new unsymmetrical photochromic diarylethene 1o, which is named 1-[2-methyl-5-(4-methoxyphenyl)-3-thienyl]-2-[2-methyl-5-(4-formyphenyl)-3-thienyl] perfluorocyclopentene, was synthesized. Its optical properties, including photochromic reactivity, kinetics and fluorescence properties were investigated in detail. The result indicated that the diarylethene underwent reversible photochromism, changing between colorless and blue in hexane solution and in PMMA, respectively. What is more, the kinetic experiments illustrated that the cyclization/cycloreversion process of this compound was determined to be the zeroth/first reaction. In addition, the results demonstrated that the diarylethene 1o had remarkable fluorescence switching properties.

Photochromic Kinetics of a Novel Unsymmetrical Diarylethene

A new unsymmetrical photochromic diarylethene1o, which is named 1-[2-methyl-5-(4-methoxyphenyl)-3-thienyl)-2-{2-methyl-5-[4-methoxyl-3-(2-(1,3-dioxolane)) phenyl]-3-thienyl} perfluorocyclopentene, was synthesized. Its optical properties, including photochromic reactivity, kinetics and fluorescence properties were investigated in detail. The result indicated that the diarylethene underwent reversible photochromism, changing between colorless and blue in hexane solution upon appropriate irradiation with UV light or visible light, respectively. What is more, the kinetic experiments illustrated that the cyclization/cycloreversion process of this compound was determined to be the zeroth/first reaction. In addition, the results demonstrated that the unsymmetrical diarylethene compound1ohad remarkable fluorescence switching properties.

Bis-spironaphthooxazine based photochromic polymer materials

The photochromism and guest binding of spiro-naphtho-oxazine dimer (SNOD) based materials were investigated. The specifically angled, conjugated dimer, SNOD, was covalently connected to α-methoxy-ω-amino-poly(ethylene glycol) (PEG) and studied under UV irradiation. Results showed the specific effects of the polymer chain on their photochromic properties and relaxation kinetics. These new materials exhibited repeatable photo-switchability and little kinetics dependency on solvent polarity. The nanoscale micelles were prepared by self-assembly of amphiphilic SNOD–PEG conjugates in aqueous medium. A palladium catalyst as a guest agent was encapsulated in the micelle core, which reduced the thermal closing rate of the merocyanine isomer of the spirooxazine dimer. SNOD was also conjugated onto solid polymer beads and investigated for the binding affinity with dyes and catalysts. The stable binding affinity towards the palladium catalyst indicated potential applications for selective recognition, extraction, and controlled release.

Photochromic, Kinetics, and Fluorescence of a Novel Diarylethene

A new unsymmetrical photochromic diarylethene, 1-(2-ethyl-3-benzofuranyl)-2-(2,5 -dimethyl-3-thienyl)perfluorocyclopentene (1) was synthesized, and its photochromic properties and kinetics of the photochromic cyclization/cycloreversion were investigated. The results showed that the cyclization/cycloreversion process of these compounds were determined to be the zeroth/first order reaction.The compound exhibited good photochromism in hexane solution with alternating irradiation by UV/Vis light, and the maxima absorption of its closed-ring isomer 1c are 502 nm. The open-ring isomer of the diarylethene 1 exhibited relatively strong fluorescence at 402 nm in hexane solution (2 × 10-5 mol/L) and 412 nm in PMMA amorphous film when excited at 312 nm and 310 nm,respectively. The fluorescence intensity decreased along with the photochromism upon irradiation with 297 nm light and its closed-ring isomer showed almost no fluorescence.The fluorescence spectra of diarylethene 1o depended on the concentration.

Synthesis, characterization, and solvent-independent photochromism of spironaphthooxazine dimers

Abstract Specifically angled, conjugated spiroindolinonaphthooxazine dimers (SNOD) have been synthesized. The photochromic reactions of two types of SNOD were studied under continuous UV irradiation in solvents of different polarity. Comparison of these results with the single unit provides the examination of the specific effect of substituents on their photochromic properties and relaxation kinetics. The photomerocyanine isomers showed positive solvatochromism, supporting the premise for a less polar quinoidal structure. The thermal closing rate at 25 °C ranged from 0.2 to 1.6 s−1 depending on the compound and solvent. Photochromism of these new compounds showed little dependency on solvent polarity and stable cyclability.

Polarized Normal-Incidence Cavity Ring-Down Spectroscopy: Probing Spiropyran Photochromism in Thin PMMA Films and Toluene

A normal-incidence geometry, polarization-resolved cavity ring-down spectroscopy technique (polarized NICRDS) is described to probe the polarized absorbance of surface-adsorbed thin films and short-path length liquid samples. The technique is demonstrated by a kinetic study of the photochromic behavior of the spiropyran dye 6,8-dibromo-1', 3'-dihydro-1', 3', 3'-trimethylspiro[2H-1-benzopyran-2, 2'-(2H)-indole]. The technique is shown potentially to have monolayer coverage sensitivity and can measure the angular orientation distribution of analyte molecules. The photochromic kinetics of 6,8-dibromoBIPS in toluene solution were qualitatively consistent with a previous study of this molecule using conventional absorption spectroscopy. The absorption polarizations and slow ring-closing kinetics measured in a thin poly(methyl methacrylate) film are consistent with a strong interaction of the spiropyran and merocyanine forms with the polymer matrix.

Synthesis and thermal decomposition and photochromic kinetics of a charge-transfer salt (C3H5N2)3[PMo12O40

Synthesis and thermal decomposition and photochromic kinetics of a charge-transfer salt (C3H5N2)3[PMo12O40

Comprehensive Modulation of Naphthopyran Photochromism in a Rigid Host Matrix by Applying Polymer Conjugation

Naphthopyran polymer conjugates of various rigidities were synthesized by atom transfer radical polymerization (ATRP), and their photochromic properties were tested within a rigid host matrix. Broad tuning of photochromic kinetics was displayed as a result of polymer conjugation because of its ability to alter the local environment of the naphthopyran within the host. End-functionalized conjugates, synthesized from a naphthopyran-functionalized ATRP initiator, allowed systematic tuning of kinetics via modulation of chain length of attached polymer. Reducing the rigidity of the conjugate resulted in an acceleration of kinetics and an increase in colorability. Pronounced chain lengths of poly(methyl methacrylate) (>18 000 g/mol) were required for decoloration kinetics to be effectively depressed compared with an unconjugated naphthopyran control. Random in-chain incorporation of the naphthopyran was afforded by copolymers made with naphthopyran-functionalized monomers. At the expense of a defined placement ...

PHOTOCHROMIC KINETICS OF ASYMMETRICAL DIARYLETHENES IN DIFFERENT SOLVENTS AND IN PMMA FILMS

Three new asymmetric photochromic diarylethenes bearing fluorine atoms at the ortho-, meta-, or para-position of one terminal phenyl group were synthesized, and their photochromism and kinetics of the photochromic cyclization/cycloreversion both in different solvents and in PMMA films were investigated. The results showed that the cyclization/cycloreversion process of these compounds were determined to be zeroth/first order reaction, and the reaction rates (k) were obtained from the slope of every line. The substituent position effect on the cycloreversion process of the three compounds was remarkable and the solvent polarity enhanced this effect. The values of reaction rates in PMMA films were quite different from those in solvents indicating that the kinetics processes of the three compounds taking place in PMMA films differs from the same processes occurring in common solvent.