Wavelength-Tunable Light-Induced Polymerization of Cyanoacrylates Using Photogenerated Amines

Cyanoacrylate photopolymerization has already been described, but it generally requires the use of organometallic photoinitiators and highly reactive monomers, which often leads to photoinitiator-monomer mixtures with limited stability. In this work we report a method to tackle these limitations, which relies on the use of amines bearing photoremovable protecting groups as light-responsive nucleophilic cyanoacrylate initiators. By exploiting the versatility of amine photorelease strategies, we have developed a series of all-organic initiators that (a) enable fast, on demand photocuring of commercial formulations of various cyanoacrylates, including less reactive, biologically relevant long alkyl chain monomers; (b) show wavelength tunability along the UV-vis spectrum and good thermal stability in the dark; and (c) lead to polymeric materials with excellent adhesive behavior. Because of this combination of properties, photogenerated amines appear as ideal candidates to bring cyanoacrylate photopolymerization into real application, especially in the biomedical field

Liquid-filled valence tautomeric microcapsules : a solid material with solution-like behavior

The integration of stimuli-responsive valence tautomeric (VT) molecular systems into solid materials without compromising their functionality is a major bottleneck for the use of these compounds in high-added value applications. In this work, an innovative, simple, and universal approach is described to tackle this challenge based on the confinement of the active species into liquid-filled polymeric capsules. A microstructured solid with optimized solution-like behavior is obtained in this way, whose VT properties can be rationally tuned upon variation of the encapsulated solvent. Incorporation of the resulting capsules into thin films or other matrices of interest allows successful transfer of valence tautomerism from the liquid phase to solid materials, thus paving the way to the fabrication of functional devices based on spin transition compounds

Tunable Thermofluorochromic Sensors Based on Conjugated Polymers

Altres ajuts: CERCA Programme/Generalitat de CatalunyaEven though thermofluorochromic materials are eternal candidates for their use in multiple applications, they are still limited as they require complex synthetic strategies to accomplish tunable optical properties and/or provide optical changes only over a very wide temperature range. By taking advantage of the high sensitivity of the optical properties of conjugated polymers and oligomers to the external environment, herein phase change material (PCM)-based thermofluorochromic mixtures are created, where the solid-to-liquid transition of the PCM host triggers a sharp fluorescence color change of the dispersed polymers/oligomers. Fluorophore conjugation length, concentration, and PCM nature can be used to vary the spectral properties of the resulting materials along the visible region, covering a large part of the CIE 1931 color space. For the preparation of functional devices, this behavior can be directly transferred to the solid state by soaking or printing cellulose papers with the obtained thermofluorochromic mixtures as well as by structuring them into solid lipid particles that can be dispersed within polymer matrices. The resulting materials show very promising features as thermal sensors and anticounterfeiting labels

Solid Multiresponsive Materials Based on Nitrospiropyran-Doped Ionogels

Altres ajuts: acords transformatius de la UABThe application of molecular switches for the fabrication of multistimuli-responsive chromic materials and devices still remains a challenge because of the restrictions imposed by the supporting solid matrices where these compounds must be incorporated: they often critically affect the chromic response as well as limit the type and nature of external stimuli that can be applied. In this work, we propose the use of ionogels to overcome these constraints, as they provide a soft, fluidic, transparent, thermally stable, and ionic-conductive environment where molecular switches preserve their solution-like properties and can be exposed to a number of different stimuli. By exploiting this strategy, we herein pioneer the preparation of nitrospiropyran-based materials using a single solid platform that exhibit optimal photo-, halo-, thermo-, and electrochromic switching behaviors

Solid Multiresponsive Materials Based on Nitrospiropyran-Doped Ionogels

Altres ajuts: Acord transformatiu CRUE-CSICThe application of molecular switches for the fabrication of multistimuli-responsive chromic materials and devices still remains a challenge because of the restrictions imposed by the supporting solid matrices where these compounds must be incorporated: they often critically affect the chromic response as well as limit the type and nature of external stimuli that can be applied. In this work, we propose the use of ionogels to overcome these constraints, as they provide a soft, fluidic, transparent, thermally stable, and ionic-conductive environment where molecular switches preserve their solution-like properties and can be exposed to a number of different stimuli. By exploiting this strategy, we herein pioneer the preparation of nitrospiropyran-based materials using a single solid platform that exhibit optimal photo-, halo-, thermo-, and electrochromic switching behaviors

Multimodal Fluorescence Switching Materials : One Dye to Have Them All

Acord transformatiu CRUE-CSICOff/on, on/off, and on/on fluorescence switching systems find application in a variety of areas, for each of which a particular dye or dye-switch tether must be specifically designed and synthesized. Herein it is demonstrated that such tight requirement can be avoided by using easily prepared mixtures of readily available emitters and phase change materials (PCMs). By proper selection of the PCM and, if needed, additives, thermo- and photothermoresponsive materials showing all classes of emission switching modes can be prepared from a single dye and without chemical modifications. This strategy can be generalized to distinct emitters and, thanks to the facile and versatile printability of dye-PCM mixtures, it can be used for the fabrication of fluorescent patterns showing complex (photo)thermal responses with direct applicability in sensing and anti-counterfeiting

Electrocarboxylation of Spiropyran Switches through Carbon-Bromide Bond Cleavage Reaction

Acord transformatiu CRUE-CSICAltres ajuts: Autonomous University of Barcelona predoctoral PIF grantThis manuscript deals with carbon capture and utilization to synthetize high-added chemicals using CO as a C1-organic building block for C−C bond formation. The study focuses on the electrocarboxylation of 1,3,3-trimethylindolino-6'-bromobenzopyrylospiran switch (Br-BIPS). Prior to the electrocarboxylation process, the electrochemical reduction mechanism of Br-BIPS and CO is disclosed in polar aprotic solvents using two different cathodes (glassy carbon and silver) under nitrogen atmosphere. Once the role of the cathode in the reduction carbon-bromide bond cleavage is understood, carboxylated spiropyran derivatives can be synthesized in moderate yields and conversion rates through an electrocarboxylation process using CO silver cathode and polar aprotic solvents. The "green" efficient route described in the current work would open a new sustainable strategy for designing and building "smart" surfaces with switchable physical properties

Dual-Wavelength Gated oxo-Diels-Alder Photoligation

Altres ajuts: Acord transformatiu CRUE-CSICThe control of chemical functionalization with orthogonal light stimuli paves the way toward manipulating materials with unprecedented spatiotemporal resolution. To reach this goal, we herein introduce a photochemical reaction system that enables two-color control of covalent ligation via an oxo-Diels-Alder cycloaddition between two separate light-responsive molecular entities: a UV-activated photocaged diene based on ortho-quinodimethanes and a carbonyl dienophile appended to a diarylethene photoswitch, whose reactivity can be modulated upon illumination with UV and visible light

Reversibly Switchable Fluorescent Molecular Systems Based on Metallacarborane-Perylenediimide Conjugates

Altres ajuts: Universitat Autònoma de Barcelona predoctoral PIF fellowshipIcosahedral metallacarboranes are θ-shaped anionic molecules in which two icosahedra share one vertex that is a metal center. The most remarkable of these compounds is the anionic cobalt-based metallacarborane [Co(CBH)], whose oxidation-reduction processes occur via an outer sphere electron process. This, along with its low density negative charge, makes [Co(CBH)] very appealing to participate in electron-transfer processes. In this work, [Co(CBH)] is tethered to a perylenediimide dye to produce the first examples of switchable luminescent molecules and materials based on metallacarboranes. In particular, the electronic communication of [Co(CBH)] with the appended chromophore unit in these compounds can be regulated upon application of redox stimuli, which allows the reversible modulation of the emitted fluorescence. As such, they behave as electrochemically-controlled fluorescent molecular switches in solution, which surpass the performance of previous systems based on conjugates of perylendiimides with ferrocene. Remarkably, they can form gels by treatment with appropriate mixtures of organic solvents, which result from the self-assembly of the cobaltabisdicarbollide-perylendiimide conjugates into 1D nanostructures. The interplay between dye π-stacking and metallacarborane electronic and steric interactions ultimately governs the supramolecular arrangement in these materials, which for one of the compounds prepared allows preserving the luminescent behavior in the gel state

Polymethylferrocene-induced photopolymerization of cyanoacrylates using visible and near-infrared light

Metallocene-induced photopolymerization of cyanoacrylates based on electron transfer processes has been proposed as an alternative to more conventional light-curing strategies relying on photobase generators. However, successful application of this methodology has so far only been achieved for very reactive cyanoacrylates under UV illumination and long irradiation times, which eventually hampers its practical use. To overcome these limitations, we describe in this work the use of electron-rich polymethylferrocenes as photoinitiators, with which fast light-induced polymerization of commercial formulations of less reactive, but more relevant long alkyl chain cyanoacrylates has been accomplished by illumination with visible and even near-infrared light. In addition, generalization of this technology to other electron-deficient, noncyanoacrylate monomers has been demonstrated. The low oxidation potential of polymethylferrocenes accounts for these excellent results, which strongly favors the formation of radical anions by electron transfer that initiate the polymerization reaction. Because of the high molecular weight and superior adhesive behavior of the resulting polymer materials as well as the facile access to polymethylferrocenes, they emerge as very attractive photoinitiators for the light-curing of cyanoacrylate (and other) glues in real applications