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Photoactive Functional Soft Materials (Preparation, Properties, and Applications) || Photoresponsive Soft Materials Based on Reversible Proton Transfer
摘要： Proton transfer is one of the most fundamental processes in nature and numerous chemical, material, and biological processes are driven by proton transfer. For example, biological systems use proton gradient as an energy form to synthesize ATP for their biological functions; many organic reactions are catalyzed by Bronsted acids; and many materials have pH‐sensitive properties. Proton transfer is also involved in different aspects of polymer science relative to preparation, property, and processing. For example, cationic polymerizations can be initiated by proton transfer from a strong acid to a monomer. It has been reported that many polymers are sensitive to the pH (proton concentration) of the environment, and their properties including mechanical, geometrical, electric, optical, and magnetic properties, change with pH due to proton transfer between the polymers and the environment. Polymers with acid‐labile bonds have been studied for drug delivery; and photoinduced cationic polymerization using photoacid‐generators (PAGs) has been applied to photolithography.
关键词： Proton transfer,photoacid,fragrant‐releasing polymers,photoresponsive nanoparticles,photochromic materials,photoresponsive polymers,reversible
更新于2025-09-23 15:21:01
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Reversible intermolecular-coupled-intramolecular (RICI) proton transfer occurring on the reaction-radius <i>a</i> of 2-naphthol-6,8-disulfonate photoacid
摘要： Steady-state and time-resolved fluorescence techniques were employed to study the excited-state proton transfer (ESPT) from a reversibly dissociating photoacid, 2-naphthol-6,8-disulfonate (2N68DS). The reaction was carried out in water and in acetonitrile–water solutions. We find by carefully analyzing the geminate recombination dynamics of the photobase–proton pair that follows the ESPT reaction that there are ? side group at the 8 position which two targets for the proton back-recombination reaction: the original O? dissociation site and the SO3 is closest to the proton OH dissociation site. This observation is corroborated in acetonitrile-water mixtures of χwater < 0.14, where a slow ? group via H-bonding water. The proton-transferred R?O? fluorescence band in mixtures of χwater < 0.14 where only intramolecular ESPT occurs is red shifted by about 2000 cm?1 from the free R?O? band in neat water. As the water content in the mixture increases above χwater = 0.14, the R?O? fluorescence band shifts noticeably to the blue region. For χwater > 0.23 the band resembles the free anion band observed in pure water. Concomitantly, the ESPT rate increases when χwater increases because the intermolecular ESPT to the solvent (bulk water) gradually prevails over the much slower intramolecular via the water-bridges ESPT process.
关键词： 2-naphthol-6,8-disulfonate,photoacid,intermolecular ESPT,geminate recombination,intramolecular ESPT,excited-state proton transfer
更新于2025-09-23 15:19:57
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Recent Advances and Challenges in the Design of Organic Photoacid and Photobase Generators for Polymerizations
摘要： Photopolymerization, or the use of light to trigger polymerization, is one of the most exciting technologies for advanced manufacturing of polymers. One of the key components in the photopolymerization processes is the photoactive compound that absorbs the light generating the active species that promotes the polymerization and largely determines the final properties of the material. The field of photopolymerization has been dominated by photo-radical generators to mediate radical reactions. In the last decade, in order to expand the number of polymers that can be prepared by photopolymerization, intensive research has been devoted to the synthesis and utilization of photoactive molecules that are able to generate a base or an acid upon irradiation. These organic compounds are known to promote not only the ring-opening polymerization of various heterocyclic monomers such as lactones, carbonates or epoxides but also to trigger the step-growth synthesis of polyurethanes. This review highlights the recent advances in the development of organic photobase and photoacid generators, with the aim of encouraging the wider application of these photoactive compounds in the photopolymerization area and to expand the use of these polymers in advanced manufacturing processes.
关键词： advanced manufacturing,photoacid generators,organic compounds,photobase generators,photopolymerization
更新于2025-09-23 15:19:57
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Design of Iodonium Salts for UV or Near-UV LEDs for Photoacid Generator and Polymerization Purposes
摘要： Iodonium salts are well established photoacid generators, cationic photoinitiators, as well as additives commonly used in photoredox catalytic cycles. However, as a strong limitation, iodonium salts are characterized by low light absorption properties for λ > 300 nm so that these latter cannot be activated with cheap, safe, and eco-friendly near UV or even visible light emitting diodes (LEDs). To overcome this drawback, the covalent linkage of an iodonium salt to a chromophore absorbing at longer wavelength is actively researched. With aim at red-shifting the absorption spectrum of the iodonium salt, the synthesis of new compounds combining within a unique chemical structure both the chromophore (here the naphthalimide sca?old) and the iodonium salt is presented. By mean of this strategy, a polymerization could be initiated at 365 nm with the modi?ed iodonium salts whereas no polymerization could be induced with the benchmark iodonium salt i.e., Speedcure 938 at this speci?c wavelength. To examine the e?ect of the counter-anion on the photoinitiating ability of these di?erent salts, ?ve di?erent counter-anions were used. Comparison between the di?erent anions revealed the bis(tri?uoromethane)sulfonimide salt to exhibit the best photoinitiating ability in both the free radical polymerization of acrylates and the cationic polymerization of epoxides. To support the experimental results, molecular orbital calculations have been carried out. By theoretical calculations, the initiating species resulting from the photocleavage of the iodonium salts could be determined. The cleavage selectivity and the photochemical reactivity of the new iodoniums are also discussed.
关键词： LED,photopolymerization,iodonium salt,photoacid,cationic initiator
更新于2025-09-16 10:30:52
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Substituent Effect on Metastable‐State Photoacids: Design, Synthesis and Evaluation of their Photochemical Properties
摘要： Recently, metastable-state photoacids have been widely used to control proton transfer in numerous chemical and biological processes as well as applications with visible light. Generally, substituent groups have great influence on photochemical properties of molecules, which will further affect their applications. Yet, substituent effect on the metastable-state photoacid has not been studied systematically. In this work, sixteen metastable-state photoacid derivatives were designed and synthesized based on their substituents involving a large range of σ-π electron-donor-acceptor capability. Substituent effects main on their color display (or maximum absorption peak(s)), solubility, pKa(s), dark-/photo-acidity, photosensitivity and relaxation kinetic(s) were investigated in detail. This study will be conducive to targetedly design and synthesize promising photoacids as well as to apply their photo-controlled proton-release processes in functional materials/devices.
关键词： visible-light-response,metastable-state photoacid,pH photocontrol,substituent effect,chemical dynamics
更新于2025-09-09 09:28:46
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Materials Overview for 2-Photon 3D Printing Applications
摘要： Interest in microscale 3D lithography continues to grow with the development of new tools and new patterning materials. To date most available materials are rigid, glassy systems derived from stereolithography studies. Soft materials lack the same level of sophistication, but there is a drive to improve this situation with the introduction of new elastomers and hydrogels. A general strategy is lacking for these 3D patterning systems as there is for the production of chemically amplified photoresists. This paper describes both positive and negative tone chemically amplified 3D materials as well and photocured systems based on radical and cationic crosslinking systems.
关键词： lithography,Photoresist,Photoacid,Photosensitizer,Photoradical generator,2-Photon
更新于2025-09-04 15:30:14