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Aromatic esterificated benzophenone derivatives, benzoic acid 4-benzoyl-phenyl ester (BPBz) and bis-benzoic acid 4-benzoyl-phenyl ester (BisBPBz) were simply synthesized and characterized. The triplet states of the photoinitiators were determined by laser flash photolysis and phosphorescence spectroscopy. The photodecomposition of the initiators was performed by UV light; the increase in the absorption spectra was attributed to the decreasing number of ester groups which led to an increase in ketone groups according to the Photo-Fries rearrangement of aromatic esters. The photoinitiation capabilities for methyl methacrylate (MMA) polymerizations were investigated under air and nitrogen atmospheres. Ester-functional benzophenone photoinitiators were found to be more effective than benzophenone (BP) in the presence of a co-initiator for photoinduced free radical polymerization of MMA. The kinetics of photopolymerization for different formulations which consist of multifunctional acrylates was also studied using the Real-Time Fourier Transform infrared spectroscopy (RT-FTIR) method. The film properties of these formulations were investigated after curing of films by Mini-UV-Cure equipment. [ABSTRACT FROM AUTHOR]

Acetic acid-based thioxanthone ( TXCH2 COOH) was synthesized and characterized and used as a photoinitiator for free radical photopolymerization of methyl methacrylate ( MMA) in the absence and presence of a tertiary amine ( MDEA) in different solvents. Different absorption properties were observed depending on the solvent. Fluorescence and phosphorescence experiments were also carried out successfully. The fluorescence quantum yield was found to be 0.09 and the phosphorescence lifetime was calculated as 138 ms at 77 K. The photoinitiator undergoes efficient intersystem crossing into the triplet state and the lowest triplet state possesses π- π* configuration. Laser flash photolysis experiments show that transient absorption of TXCH2 COOH is similar to the parent thioxanthone and the triplet lifetime was calculated as 2.3 μs at 630 nm. [ABSTRACT FROM AUTHOR]

Free radical photopolymerization of methyl methacrylate (MMA) initiated by 2-mercaptothioxanthone (TX-SH), thioxanthone-thioacetic acid (TXSCH2COOH), and thioxanthone-carboxymethoxy acetic acid (TXOCH2COOH) as so called one-component initiators was performed with and without an external magnetic field (MF). These initiators contain light-absorbing and electron/hydrogen-donating fragments in one molecule and do not require an additional hydrogen donor, and initiate the polymerization of MMA in the air. Polymerization experiments were performed in solutions with 3 different optical densities at λ365 nm, where the photoinitiator absorbs. It was observed that application of MF leads to both larger conversion and higher molecular weight of the prepared PMMA, other conditions being equal. The effect of MF on the photopolymerization of MMA is discussed. [ABSTRACT FROM AUTHOR]

Abstract: 2-Methylol-thioxanthone (TX-M) was synthesized and characterized as a new photoinitiator. Photopolymerization experiments were performed with methyl methacrylate and also trimethylolpropanetriacrylate (TMPTA) as a multifunctional monomer in the presence of TX-M with N-methyl diethanol amine. Polymerization did not occur in an air atmosphere with TX-M without adding MDEA. The inhibiting effect of oxygen on the rate of polymerization was observed to be due to quenching of the triplet radicals by the carbonyl compound (TX-M). [Copyright &y& Elsevier]

Abstract: 2-Morpholino acetonaphthone (MPM) was synthesized as a cleavable photoinitiator and the structure of the photoinitiator was confirmed by spectral and elemental analysis. The photoinitiation capability of MPM was demonstrated by using methyl methacrylate and a formulation containing multifunctional monomers. [Copyright &y& Elsevier]

Abstract: The initiation efficiency of 3H-5-Thia-1,2,3-triaza-cyclopenta[b]anthracene-10-one (TX-BT) for free radical polymerization of methyl methacrylate (MMA), is enhanced by the addition of N-methyldiethanolamine (MDEA) to the initiator formulation. Photodegradation of polymethylmethacrylate (PMMA), which was prepared with and without TX-BT, was examined according to its weight loss. The beneficial effects of TX-BT as initiator and stabilizer for polymerization of methyl methacrylate was determined. [Copyright &y& Elsevier]

Abstract: Photoinitiated free radical polymerization of methyl methacrylate (MMA) in aqueous solution via hydrogen abstraction mechanism was described. For this purpose, thioxanthone (TX) chromophoric group was chemically incorporated into β-cyclodextrin (β-CD) by a simple esterification process. The resulting thioxanthone photoinitiator (TX–β-CD) exhibited similar spectral characteristics and photoactivity to that of the parent TX molecule. Host guest complexes of MMA with TX–β-CD in water, in the presence of N-methyldiethanol amine (NMDEA) as a hydrogen donor, facilitated photoinitiated free radical polymerization in aqueous medium. The postulated mechanism is based on the intermolecular reaction of photoexcited triplet TX moiety of TX–β-CD with NMDEA. The resulting amino alkyl radicals initiate the polymerization. [Copyright &y& Elsevier]

Phenacyl onium salts, namely N-phenacyl-N,N-dimethylanilinium-N,N-diethyldithiocarbamate (Ia), phenacyl-triphenylphosphonium-N,N-diethyldithiocarbamate (II), 1-phenacyl pyridinium-N,N-diethyldithiocarbamate (III), are shown to be efficient photoinitiators for polymerization of methyl methacrylate (MMA). Plausible mechanism of the photoinitiation involves both free radical and zwitterionic processes. Phenacyl radicals formed from the homolytic cleavage of carbon heteroatom bond initiates the free radical polymerization while Lewis bases formed from homolytic cleavage followed by electron transfer or heterolytic cleavage responsible for the zwitterionic initiation. The capability of the salts to act as initiators for the polymerization of multifunctional monomer, trimethylolpropane trimethacrylate (TMPTMA), was also demonstrated. [Copyright &y& Elsevier]

[Display omitted] • An annelated thioxanthone thioacetic acid is synthesized and characterized. • High molar absorptivity in visible region made photoinitiator attractive. • Low fluorescence quantum yield and triplet energy leaded production of initiating radicals. • Type II initiation mechanism is responsible. Thioxanthonation of naphthalene thioacetic acid (TXNPSCH 2 COOH) resulted a visible light photoinitiator with the high molar absorptivity (ε 405 : 5680 L.mol−1.cm−1) in the visible spectral region and made this compound an attractive photoinitiator for free radical polymerization reactions. Low fluorescence quantum yield (Φ F : 0.06 in 2-MeTHF) and comparatively low triplet energy (186 kJ/mol in 2-MeTHF) was in favorable for efficient intersystem crossing to the triplet state which is necessary for production of initiating radicals. Indeed, photopolymerization of methyl methacrylate along with TXNPSCH 2 COOH (1 × 10−3 M) and a tertiary amine namely MDEA yielded nearly 25% conversion of monomer to polymer. All spectrophotometric studies including laser flash photolysis which gives triplet lifetime of initiator which is very important information for initiation mechanism of photoinitiators, indeed a long enough triplet lifetime of TXNPSCH 2 COOH (τ T : 1000 ns) allows for efficient reactions with co-initiators to generate radicals. [ABSTRACT FROM AUTHOR]

Abstract: A mechanistic study concerning photoinitiated free radical polymerization using Thioxanthone–Carbazole (TX–Cz) as a one-component Type II photoinitiator was performed. TX–Cz presented visible initiator characteristics with absorptions at 434 and 414nm where the molar absorption coefficients were 2014 and 1754Lmol−1 cm−1, respectively. Fluorescence and phosphorescence spectroscopy, as well as laser flash photolysis was employed to study the photophysical properties of TX–Cz. In addition, photopolymerization of methyl methacrylate (MMA) showed that TX–Cz is efficient photoinitiator. To explain the initiation mechanism of TX–Cz, fluorescence and phosphorescence emission spectra of poly (methyl methacrylate) (PMMA) were also taken to see whether the initiator covalently bonded to the polymer. The postulated mechanism is based on inter- molecular reaction of the triplet, 3(TX–Cz)⁎ with the carbazole moiety at ground state, TX–Cz. The photoinitiation efficiency of TX–Cz during gelation of multifunctional acrylates was also investigated by Photo-Differential Scanning Calorimetry (Photo-DSC) technique and high polymerization rates were obtained. [Copyright &y& Elsevier]

Abstract: The novel 4-(9-oxo-9 H-thioxanthen-2yloxy) phthalonitrile (TX-Pht) and its peripherally tetra substituted zinc phthalocyanine complex (TX-ZnPc) have been prepared and characterized by spectroscopic and elemental analysis techniques. Photoinitiated polymerization of methyl methacrylate (MMA) with TX-ZnPc has been investigated in the presence and absence of a co-initiator. Fluorescence and phosphorescence measurements have been also performed to determine the photophysical properties. Low fluorescence quantum yield (ΦF=0.08) compared to the unsubstituted ZnPc has been found. This allows initiator to undergo intersystem crossing into the triplet state and the lowest triplet state possesses π-π⁎ configuration. [Copyright &y& Elsevier]

Abstract: Photoinitiation of the polymerization of methyl methacrylate by the bis-diethylaminocoumarin dye (BKC) in the presence of various amines was studied in order to determine the efficient amine that leads to the formation of the initiating radicals. RT-FTIR studies were also performed for multifunctional methacrylate. According to photoinduced polymerization and RT-FIR studies, N-methyldiethanol amine was the more efficient H-donor compared with the others. [Copyright &y& Elsevier]

[Display omitted] • New one-component Type II photoinitiator [TX-S-] 2 is synthesized. • Photochemical and photophysical properties are investigated. • Exchange reaction with diphenyl disulfide is investigated. • Photopolymerization experiments are conducted. Herein, we report the successful synthesis of dithioxanthone-disulfide [TX-S-] 2 as a new one-component type II photoinitiator. Photophysical properties of [TX-S-] 2 in terms of fluorescence and phosphorescence properties were investigated and low fluorescence quantum yield was observed, which indicates an efficient intersystem crossing (ISC) that leads to the generation of triplet states. Efficiently produced initiating thiyl radicals from the triplet states lead to polymerization of methyl methacrylate with [TX-S-] 2 in air atmosphere. To elucidate the initiating mechanism, a disulfide exchange reaction was performed in the presence of diphenyl disulfide [Ph-S-] 2 , and the obtained results from HQ-TOF confirmed that [TX-S-] 2 disulfide bond cleavage occurs upon irradiation with light. Initiating mechanism of [TX-S-] 2 revealed the potential usage of this compound as a self-healing agent due to the efficient cleavage of disulfide bonds. In conjunction with the experimental studies series of Density Functional Theory calculations were performed and various photophysical and photochemical properties, including HOMO and LUMO, were computationally calculated and visualized. [ABSTRACT FROM AUTHOR]

• Synthesis of POSS-TX was achieved using TXOCH 2 COOH and POSS-NH 2. • Inititiation efficiency of POSS-TX was examined for the photopolymerization of methyl methacrylate. • POSS-TX initiates polymerization of MMA in air atmosphere at considerably low concentration. Size, shape and distribution-controlled silver nanoparticles (AgNps) were produced by a rapid and efficient method either in solvent or in polymer matrix by which the silver ion is reduced and a polymer matrix is simultaneously generated in the presence of various photoinitiators by the means of UV light. 2-Mercaptothioxanthone (TX-SH), Thioxanthone (TX) and TX + Thiophenol were used as photoinitiator systems for the polymerization of PEGMEA/PEGDA monomer mixture in the presence of AgNO 3 salt. As a summary of results, it is important to note that the size and distribution of Nps depend on the photoreducing species. Therefore TX-SH, due to thiol functionality in its structure, helped production of he 7–40 nm size and distribution-controlled AgNps in polymer matrix. In-situ prepared AgNps/Polymer nanocoatings exhibited a reflected silver mirror view as a result of aggregation depending on the irradiation time. Antibacterial efficiency and susceptibility of AgNps containing nanocomposite films were examined for t E. coli, P. aeruginosa, S. aureus and B. cereus. Obtained antimicrobial results show that photochemically prepared nanocomposites considerably increase the antimicrobial activity on Gram negative bacteria compared to Gram positive bacteria. [ABSTRACT FROM AUTHOR]