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Here, a benzaldehyde substituted diacetylene vesicle formed through a self‐assembly strategy in water is reported. Under UV irradiation, conjugated polydiacetylene (PDA) could be generated in the blue phase by 1,4‐addition topopolymerization. Furthermore, this newly developed PDA vesicle displays distinctive colorimetric response to triple stimuli, including temperature, pH, and organic amines. Specifically, a clear blue‐to‐purple‐to‐red chromatic transition is observed for the PDA vesicle upon a gradient heating procedure from 25 to 75 °C. Although no obvious colorimetric changes happen when the PDA vesicle is exposed to acidic environments, it gradually turns into red color in alkaline aqueous solution or atmosphere with increasing pH values. More interestingly, this PDA vesicle can serve as an excellent sensor to distinguish some typical aliphatic/aromatic amines based on its different colorimetric and morphologic transformation behaviors. It is suggested that the incorporated benzaldehyde head group in PDA plays an essential role for the resulting responsiveness to the various environmental stimuli. As the preparation method is simple and straightforward, the novel PDA vesicle introduced here holds great potential as a promising sensor with the naked eye. [ABSTRACT FROM AUTHOR]

Many academic and industrial works are carried out for the search of new classes of visible light photoinitiators. In the last decade, new Type I photoinitiator generating silyl, germyl, or stannyl radicals is elegantly reported; the chemical mechanisms being often associated with the cleavage of the C(═O)Si, C(═O)Ge, or C(═O)Sn bonds. In this context, silyl glyoxylates are also reported as dual Type I and Type II photoinitiators. Silyl glyoximides are proposed here as new near‐UV and blue light sensitive photoinitiators. The synthesis of such compounds as well as their light absorption properties is discussed. Their photochemical properties are studied through steady state photolysis experiments and molecular modeling data (i.e., through the calculations of the frontier orbitals, CC bond dissociation energies and triplet state energy levels). To finish, their photoinitiating ability upon near‐UV or blue light emitting diode light is examined in a benchmark methacrylate monomer blend (BisGMA/TEGDMA). Markedly, a Type I photoinitiator behavior is highlighted but better initiating properties are found in multicomponent systems in combination with iodonium salt and amine. [ABSTRACT FROM AUTHOR]

The free radical polymerization of acrylates photo‐initiated by push–pull dye‐based photoinitiating systems (PISs) is widely investigated in previous works. As a supplementary investigation on push–pull dyes, here in this article, 25 push–pull structures comprising electron acceptors derived from indane‐1,3‐dione and 1H‐cyclopenta[b]naphthalene‐1,3(2H)‐dione (series 1) and 4‐dimethoxyphenyl‐1‐allylidene moieties (series 2) and various electron donors are synthesized and examined as innovative structures for photoinitiation. Among the two series of dyes examined in this work and by monitoring the polymerization processes by RT‐FTIR measurements, four dyes are determined as exhibiting excellent photoinitiation performances and these dyes are selected to perform further studies concerning the chemical mechanisms occurring inside the three‐component PISs, for example, steady state photolysis, fluorescence quenching measurements, and cyclic voltammetry. Markedly, their reactivity is also proved by photoinitiation performance upon sunlight. These results prompt us to develop high performance push–pull dyes as photosensitizers and sunlight can be used as a mild and ecofriendly light source, which can advantageously replace LEDs for the free radical photopolymerization in the future. Finally, the formation of 3D patterns with an excellent gradient of resolution is successfully achieved by the direct laser write (DLW) with/without silica fillers. [ABSTRACT FROM AUTHOR]

2‐Oxo‐2‐(tert‐butyldimethylsilyl)acetic acid (DKSi‐COOH), is proposed here as a new high‐performance photoinitiator (PI) for the free radical polymerization of methacrylates under blue light irradiation. In the presence of DKSi‐COOH, very good polymerization performances are reached and outstanding bleaching properties are obtained compared to traditionally used camphorquinone‐based photoinitiating systems. Remarkably, this new developed PI exhibits good water solubility and excellent stability in acidic conditions and represents therefore a promising candidate for water‐based formulations. [ABSTRACT FROM AUTHOR]

Rubrene, a compound that exhibits green light absorption, interacts with an iodonium salt through its excited singlet state to generate cations and free radicals under a green laser line at 532 nm or a halogen lamp delivering a low light intensity of polychromatic visible light. The photochemical mechanisms are investigated by steady-state photolysis, fluorescence, electrochemistry, and electron spin resonance spin trapping techniques. The produced cations and free radicals initiate both the cationic photopolymerization of epoxides and the free radical photopolymerization of acrylates. Moreover, the addition of N-vinylcarbazole into the system enhances the photopolymerization efficiency. The Rubrene/amine/chlorotriazine photoinitiating system also exhibits a much higher photoinitiation ability for the free radical photopolymerization of acrylates. [ABSTRACT FROM AUTHOR]

A series of conjugated polymers and oligomers previously used in organic photovoltaics and organic light-emitting diodes (OLEDs) have been examined for the first time as photoinitiators of polymerization. They address the present and future challenges facing photopolymerization: requirement of high extinction molar coefficients, absorption over the whole visible spectrum, ability to easily withdraw or release electrons. Interestingly, these compounds initiate the cationic polymerization of epoxides or the free radical polymerization of acrylates upon exposure of the photocurable formulations to a LED emitting at 405 nm. Some of them can potentially operate under blue, green, or red laser diodes. [ABSTRACT FROM AUTHOR]

In the present paper, new photoinitiators based on the meta-terphenyl scaffold in combination with an iodonium salt and 9H-carbazole-9-ethanol (CARET) are proposed for the free radical promoted cationic polymerization of epoxides upon visible light exposure using light emitting diodes at 405, 455, and 470 nm. Remarkably, a new high performance additive (i.e., CARET) is proposed here for cationic polymerizations. CARET shows some important advantages compared to other reported additives such as N-vinylcarbazole or benzyl alcohol used as references. Excellent polymerization initiating abilities are found and a full picture of the involved chemical mechanisms is provided. [ABSTRACT FROM AUTHOR]

Five novel thioxanthone (TX)-functionalized methacrylates as copolymerizable photoinitiators (CopPIs) for polymerization of acrylates are synthesized from reactions of tert-butyl α-bromomethacrylate with 2-hydroxy thioxanthone (TX1) and 1,4-dihydroxy thioxanthone (TX3), cleavage of their respective tert-butyl ester groups with trifluoroacetic acid (TX2, TX4), and by reaction of the acid chloride derivative of TX2 with Irgacure 2959 (TX5). These CopPIs absorb in the near UV-visible region (390-420 nm; absorption redshift =10-40 nm, ε values comparable to TX). Their performances are studied under LED exposure at 385 and 405 nm using real-time FTIR. The reactivities of TX1 and TX2 are similar to isopropyl thioxanthone, used as reference; and TX4 have lower reactivities, due to their difunctionality, which however makes them good crosslinking agents. TX5 is the first monomeric PI possessing two different type side-chain photoinitiating groups. The migration stability of two of these CopPIs is shown in the cured polyacrylates. The photochemical mechanisms are studied by electron spin resonance, steady state photolysis, laser flash photolysis, and cyclic voltammetry. [ABSTRACT FROM AUTHOR]

Naphthalimide derivatives (NDAs) with amino- or alkylthio-substituents have been synthesized and combined in photoinitiating systems (PIS) with an iodonium salt, N-vinylcarbazole, an amine, or 2,4,6- tris(trichloromethyl)-1,3,5-triazine to produce radicals, cation radicals, or cations. The photochemical mechanisms are investigated by fluorescence, cyclic voltammetry, laser flash photolysis, electron spin resonance spin trapping, and steady state photolysis techniques. The generated reactive species are capable of initiating the cationic polymerization (CP) of epoxides under air or the free radical polymerization (FRP) of acrylates in laminate upon exposure to visible lights delivered by a halogen lamp, a cold white light-emitting diode (LED), or LEDs at 385, 395, 405, 455, or 470 nm. Compared to the well-known camphorquinone based systems, the novel NDA containing PISs exhibit higher efficiencies both for CP and FRP. Remarkably, the photo­bleaching of some NDAs is significant, and colorless final polymer coatings are obtained. The structure/photochemical property relationships of NDAs are discussed in detail (redox potentials, fluorescence, rate constants of reactions, etc.) to shed some light on their respective photoinitiating ability. [ABSTRACT FROM AUTHOR]

Two star-shaped tris(4-(thiophen-2-yl)phenyl)amine derivatives, namely tris(4-(5-(3-pentylthieno[3,2- b]thiophen-5-yl)thiophen-2-yl)phenyl)amine and tris(4-(5-(3-pentyl-2-(thiophen-2-yl)thieno[3,2- b]thiophen-5-yl)thiophen-2-yl)phenyl)amine, are developed as photoinitiators for radical and cationic polymerizations under near-UV and visible light-emitting diodes (LEDs) (e.g., 385, 405, and 455 nm). When used in combination with an iodonium salt (and optionally N-vinyl carbazole) or an amine/alkyl halide couples, they lead to excellent photoinitiating abilities for the polymerization of epoxides or (meth)acrylates under air. Compared with commercial photoinitiators, i.e., camphorquinone-based systems or bis(2,4,6-trimethylbenzoyl)-phenylphosphineoxide, the novel photoinitiators exhibit noticeably higher polymerization efficiencies under air (epoxide conversions = 41-57% vs ≈0%, halogen lamp exposure; methacrylate conversions = 50-55% vs 44%, LED at 405 nm exposure; methacrylate conversions = 34-42% vs 0-8%, LED at 455 nm exposure). These systems are also interesting in overcoming oxygen inhibition. The photochemical mechanisms are studied by steady-state photolysis, electron spin resonance spin trapping, fluorescence, cyclic voltammetry, and laser flash photolysis techniques. [ABSTRACT FROM AUTHOR]

Four new push-pull dyes derived from Michler's ketones are investigated. These dyes, based on a donor-π-acceptor (D-π-A) structure, exhibit a tunable character according to the electron-withdrawing ability of the acceptor used. The new proposed structures can be used in high-performance photoinitiating systems. Remarkably, two of them are characterized by an excellent reactivity to initiate the free-radical polymerization of acrylates, the ring-opening polymerization of epoxides, as well as the synthesis of interpenetrating polymer networks (IPNs) under exposure to a laser diode at 457 nm. The chemical mechanisms are investigated by steady-state photolysis, fluorescence, and electron spin-resonance (ESR) experiments. [ABSTRACT FROM AUTHOR]

Ten acridinediones (ADs) with different substituents are prepared and investigated for their abilities to initiate a ring-opening cationic photopolymerization in combination with an iodonium salt and N-vinylcarbazole upon UV-vis light (Xe-Hg lamp; >330 nm) or visible light (halogen lamp) exposure. The structural effects in the ADs are outlined. The cationic and radical photopolymerization of an epoxide/acrylate blend in a one-step hybrid cure very efficiently leads to the formation of an interpenetrated polymer network under UV-vis light or visible light irradiation (30 s for tack-free coatings). The photochemical mechanisms are studied by molecular orbital calculations, steady-state photolysis, electron spin resonance-spin trapping, cyclic voltammetry, fluorescence, and laser flash photolysis techniques. [ABSTRACT FROM AUTHOR]

Truxene-acridine-1,8-dione derivatives ( Tr_AD) are proposed as new photoinitiators of polymerization under very soft irradiation (by a household halogen lamp), as well as laser-diode exposure at 405 nm. They exhibit a strong absorption around 380 nm. The Tr_AD/diphenyl iodonium salt/9-vinylcarbazole combination is able to promote the ring-opening polymerization of an epoxide, whereas the Tr_AD/alkyl halide/amine system is very efficient in initiating the radical photopolymerization of an acrylate. Excellent polymerization profiles are obtained. Acrylate/epoxide blends are also easily polymerized. These Tr_ADs in the three-component systems behave as photocatalysts according to oxidative cycles. The mechanisms are discussed for the different multicomponent initiating systems. [ABSTRACT FROM AUTHOR]

New photoinitiating systems based on a polyoxometalate (POM) are proposed: phosphomolybdic acid in combination with silane, germane, or iodonium salt can be used to generate silyl, germyl, or phenyl radicals as well as silylium cations. The photochemical mechanisms are studied by steady-state photolysis and electron spin resonance. The phosphomolybdic acid/silane/iodonium salt system can initiate either the radical photopolymerization of acrylates or the cationic photopolymerization of epoxides. The synthesis of interpenetrated polymer networks can also be carried out. The mechanical properties of the synthesized polymers are affected by the presence of POM in the matrix, as shown by their dynamic mechanical analysis (DMA). [ABSTRACT FROM AUTHOR]

New thiols for efficient thiol-ene polymerization reactions are presented. They do not exhibit any unpleasant odor, are characterized by quite good light-absorption properties at λ > 300 nm, and generate thiyl radicals upon UV-light exposure. Due to these interesting properties and contrary to many previously reported methodologies, the present thiol-acrylate polymerizations can be efficiently carried out without the presence of any additional photoinitiator. The chemical mechanisms are investigated by steady-state photolysis and electron spion resonance (ESR) experiments. Important parameters can also be extracted from molecular orbital calculations. [ABSTRACT FROM AUTHOR]

New perylene-3,4:9,10-bis(dicarboximide) (PBI) photoinitiators/photosensitizers derived from perylene-3,4:9,10-tetracarboxylic dianhydride are synthesized and investigated for the formation of free radicals under air and under very soft irradiation (i.e., halogen lamp) or laser diode exposure at 532 nm. Such a PBI in combination with a diphenyl iodonium salt and N-vinylcarbazole or a silane very efficiently promotes the ring-opening polymerization of epoxides and can also generate acrylate/epoxide interpenetrated polymer networks. It partly behaves as a metal-free organic photocatalyst operating in an oxidative catalytic cycle. The different chemical intermediates are characterized by ESR and laser flash photolysis experiments. The mechanisms involved in the initiation step are discussed. [ABSTRACT FROM AUTHOR]

A household halogen lamp is used to promote the ring-opening photopolymerization of epoxides in the presence of coumarin moiety containing Pt(II) complex/silane/iodonium salt combinations (epoxide/acrylate interpenetrated polymer networks can also be synthesized). Excellent polymerization profiles are obtained (conversions >70%) under this selected very soft irradiation. These Pt(II) complexes behave as photocatalysts in an oxidative cycle. A photoluminescent polymer can be in situ synthesized thanks to the luminescence properties of these complexes. The mechanisms are investigated by ESR, laser flash photolysis, and luminescence experiments. [ABSTRACT FROM AUTHOR]

Upon demand, 1,3-diamino-propane-triethylborane (DAPTB) is photolyzed in the presence of an acid generator such as a diphenyliodonium salt. Interestingly, triethylborane is released. In the presence of oxygen, ethyl radicals are generated and initiate an acrylate polymerization. This is the first example of a phototriggered production of a triethylborane usable in the photoinitiation of acrylate polymerizations. This approach is also worthwhile to overcome the oxygen inhibition for free-radical polymerization processes. [ABSTRACT FROM AUTHOR]