Michler's Ketone Research Articles

Shotgun Lipidomic Profiling of Sebum Lipids via Photocatalyzed Paternò-Büchi Reaction and Ion Mobility-Mass Spectrometry.

Sebum lipids are composed of nonpolar lipids, and they pose challenges for mass spectrometry-based analysis due to low ionization efficiency and the existence of numerous isomers and isobars. To address these challenges, we have developed ethyl 2-oxo-2-(pyridine-3-yacetate as a charge-tagging Paternò-Büchi reagent and Michler's ketone as a highly efficient photocatalyst, achieving ∼90% conversion for C═C derivatization under 440 nm LED irradiation. This derivatization, when coupled with electrospray ionization-tandem mass spectrometry, boosts the detection of sebum lipids and pinpoints C═C location in a chain-specific fashion. Identification and quantitation of isomers are readily achieved for wax esters, a class of underexplored sebum lipids, which have C═C bonds distributed in fatty alcohol and fatty acyl chains. A shotgun analysis workflow has been developed by pairing the offline PB derivatization with cyclic ion mobility spectrometry-mass spectrometry. Besides the dominant n-10 C═C location in unsaturated wax esters, profiling of low abundance isomers, including the rarely reported n-7 and n-13 locations, is greatly enhanced due to separations of C═C diagnostic ions by ion mobility. Over 900 distinct lipid structures from human sebum lipid extract have been profiled at the chain-specific C═C level, including wax esters (500), glycerolipids (393), and cholesterol esters (22), far more exceeding previous reports. Overall, we have developed a fast and comprehensive lipidomic profiling tool for sebum samples, a type of noninvasive biofluids holding potential for the discovery of disease markers in distal organs.

Occurrence and prioritization of non-volatile substances in recycled PET flakes produced in China

Recycled PET (rPET) is gaining popularity for use in the production of new food contact materials (FCMs) under the context of circular economy. However, the limited information on contaminants in rPET from China and concerns about their potential risk are major obstacles to their use in FCM in China. Fifty-five non-volatile compounds were tentatively identified in 126 batches of hot-washed rPET flakes aimed for food packaging applications in China. Although the 55 substances are not necessarily migratable and may not end up in the contacting media, their presence indicates a need for proper management and control across the value chain. For this reason, the 55 substances prioritized on the basis of level of concerns and in-silico genotoxicity profiler. Among them, dimethoxyethyl phthalate, dibutyl phthalate, bis(2-ethylhexyl) phthalate were classified as level V substances, and Michler's ketone and 4-nitrophenol were both categorized as level V substances and had the genotoxic structure alert, while 2,4,5-trimethylaniline was specified with genotoxic structure alert. The above substances have high priority and may pose a potential risk to human health, therefore special attention should be paid to their migration from rPET. Aside from providing valuable information on non-volatile contaminants present in hot-washed rPET flakes coming from China, this article proposed a prioritization workflow that can be of great help to identify priority substances deserving special attention across the value chain.

Photocrosslinking of ethylene‐vinyl acetate (EVA)–polyethylene‐octene (POE) copolymer containing halogen‐free flame retardants

AbstractPhotocrosslinking of polymers for industrial applications show undoubted advantages related to the mild conditions needed and the economical equipment. However, some issues include: the use of (i) mercury lamps as light sources, which poses concerns about safety and energy consumption, (ii) typical additives, such as halogen‐free flame‐retardant fillers (HFFR) are powdered materials, which can scatter UV photons and avoid a deep penetration of the light. In this study, we explore the UV‐curing of an innovative EVA‐POE blend containing hydrotalcite and aluminum hydroxide as HFFR in the presence of a 370‐nm UV LED, namely Ekopren® XI1321, a plastic used as coverage for electric cables. Two commercially available photoinitiators (benzophenone and ethyl Michler's ketone) were analyzed as well as two crosslinking coagents widely used in industry, that is, triallyl cyanurate and trimethylolpropane trimethacrylate. A comparison with pure EVA and LDPE was performed to show a higher cross‐linked content of the proposed blend, even in the presence of light scattering mineral fillers at high concentration.

Synthesis and characterization of aqueous base developable negative-tone poly(imide-amic acid) copolymers by the effect of the imidization ratio

Negative-tone photosensitive poly(imide-amic acid) (PIA) copolymers were synthesized from a chemical imidization process using poly(amic acid) that was prepared from a polycondensation reaction of 4,4′-(hexafluoroisopropylidene) diphthalic anhydride (6FDA), 4,4′-oxydianiline (ODA), and di[2-(methacryloyloxy)ethyl]-5-aminoisophthalate (Di-HEMA-AP) with photoreactive acrylate groups. The imidization ratio was controlled by the reaction time, and the synthesized PIA copolymers were investigated using spectroscopic methods. The photolithographic behaviors of the formulations composed of PAA and PIA copolymers, Michler’s Ketone (MK), and crosslinker were evaluated using a 2.38 wt. % tetramethylammonium hydroxide (TMAH) solution. The solubility decreased with increasing imidization ratio in an alkaline base solution because of the reducing content of carboxylic acid groups in the polymer main chain. The formulations from PIA copolymers gave clear patterns without distortion by UV light i-line irradiation and followed 2.38 wt. % TMAH solution development.

Two-photon absorption cross-section investigation of visible-light photoinitiators under Q-switched Nd:YAG nanosecond pulse laser at 1064 nm

Two-photon polymerization (TPP) technologies commonly rely on femtosecond lasers such as Ti:sapphire which limits their accessibility due to high costs and complexities. Recently, multiple reports showed TPP under near-infrared irradiation which enables the use of alternative light sources such as Neodymium-doped lasers known to be affordable and efficient for a nanosecond and picosecond pulsed generation. 4,4′-Bis(dimethyl-amino) benzophenone or Michler’s ketone (MK), one of the photoinitiators commonly used for photopolymerization under UV irradiation, also shows an absorption band in the visible region which allows for two-photon polymerization at the fundamental wavelength of Neodymium-doped lasers at 1064 nm. In this report, we investigated the two-photon absorption (TPA) of MK in contrast with Irgacure-784 and Indane-1,3-dione, reported to also be promising photoinitiators for the same TPP process. Among them, MK showed a large TPA cross-section measured via the nonlinear transmission method and Z-scan technique with Q-switched Nd:YAG nanosecond pulse laser at 1064 nm, demonstrating MK as a promising photoinitiator for the low-cost two-photon polymerization.

Bis(trimethylsilyl)amino modified Type Ⅱ photoinitiators can alleviate oxygen inhibition of near-UV LED photopolymerization due to moisture induced decomposition of initiators

Near UV-LED photopolymerization of acrylates can find many crucial applications in industrial fields, such as coatings, adhesives and 3D printing of hydrogels. However, developing the photoinitiators (PIs) well matching with the commercial LED light sources and reducing oxygen inhibition effect remain challenges. Herein, we have synthesized three kinds of type Ⅱ PIs containing bis(trimethylsilyl)amino groups; Molar extinction coefficients of these PIs are all at the 103 ∼ 104 (L·mol−1·cm−1) order of magnitude at the 365 ∼ 395 nm, comparable to the commercial PIs including Michler’s ketone (MK) and 2-isopropylthioxanthone (ITX); However, their photoinitiation capacity is much better than the MK and the ITX. In addition, these PIs have better resistance to the oxygen inhibition effect than the MK. Some researchers think the PIs containing rich Si/F elements can self-migrate towards upper layers of curing systems to reduce the oxygen inhibition effect, however, these obtained PIs with high Si fraction did not have such effect. Based on the obtained experimental results, we have proposed a new mechanism explaining their good ability to reduce the oxygen inhibition: The moisture induced decomposition of the initiators can play a key role in alleviating the oxygen inhibition; The generated Si-containing fragments after PIs’ hydrolysis can self-float towards the top surfaces to hinder the oxygen penetration, not the self-floating effect of the PIs by themselves.

Michler's Ketone: β-Cyclodextrin Host-Guest Inclusion Complex for Enhancing the Ultraviolet Protection Factor of Poplin Cotton Fabric.

Michler's ketone (4,4' bis(N,N-dimethylamino)benzophenone) mk is a potential ultraviolet radiation (UVR) absorber in various materials. In this study, we have tested the UVR filtering ability of mk on cotton fabric. The beta-cyclodextrin (β-CD) inclusion complex of mk enhances ultraviolet protection factor (UPF) drastically. The impact of β-CD on the UVR filtering of mk are demonstrated by investigating the guest (mk:absorbers)-host (β-CD:enhancer) inclusion complex. Spectral and molecular docking analysis of mk:β-CD complex infers the vertical insertion of the guest molecule by positioning -C=O group of mk at the center of the host molecule with the exclusion of the terminal atoms of guest molecule outside the β-CD cavity. Thus, the host; β-CD renders an inflexible fit to the guest:mk. The inflexible fit of mk into the β-CD cavity enhances the UVR dissipation when it is incorporated on the poplin cotton fabric. With UPF = 46 mk:β-CD complex is proposed as a potential UVR absorber suitable for manufacturing sun protective textiles. The holding of mk by β-CD enhances the UVR dissipation and hence facilitates the native red-shifted emission and non-radiative relaxation by the formation of twisted intramolecular charge transfer in mk.

Coal-Tar Dye-based Coordination Cages and Helicates.

A strategy to implement four members of the classic coal‐tar dye family, Michler's ketone, methylene blue, rhodamine B, and crystal violet, into [Pd2L4] self‐assemblies is introduced. Chromophores were incorporated into bis‐monodentate ligands using piperazine linkers that allow to retain the auxochromic dialkyl amine functionalities required for intense colors deep in the visible spectrum. Upon palladium coordination, ligands with pyridine donors form lantern‐shaped dinuclear cages while quinoline donors lead to strongly twisted [Pd2L4] helicates in solution. In one case, single crystal X‐ray diffraction revealed rearrangement to a [Pd3L6] ring structure in the solid state. For nine examined derivatives, showing colors from yellow to deep violet, CD spectroscopy discloses different degrees of chiral induction by an enantiomerically pure guest. Ion mobility mass spectrometry allows to distinguish two binding modes. Self‐assemblies based on this new ligand class promise application in chiroptical recognition, photo‐redox catalysis and optical materials.

Versatile light‐responsive organogels: Evaluation of their dye releasing and photoinitiation behaviors

ABSTRACTLight‐responsive crosslinked structures were prepared by a straightforward quaternization strategy using chloride functional polystyrene copolymers and commercially available Michler's ketone with varying feed ratios. Resulting organogels demonstrated excellent solvent absorption and their swelling characteristics were altered by UV‐light irradiation. According to scanning electron microscope images, UV‐illuminated samples showed an obvious photodecomposition, which enhanced their solvent uptake capacity with increase of UV exposure. Additionally, release behavior of eosin Y as a model compound was determined by UV–vis and fluorescence spectrometers. Achieved photoactive gels were also employed as the reusable heterogeneous initiators for photoinduced free‐radical polymerization of methyl methacrylate. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019, 57, 1275–1282

Intramolecular photocycloaddition reactions of 2- and 4-(5-arylpent-4-enyl)-1-cyanonaphthalenes

Photoreactions of 1-cyanonaphthalene derivatives containing 5-arylpent-4-enyl groups at C-2 or C-4 of the naphthalene ring were investigated. Photoreactions of C-2 derivatives in benzene or CH3CN generated intramolecular [2 + 2] and [3 + 2] photocycloadducts. Substances bearing electron-rich and electron-poor phenyl groups produced respective [2 + 2] and [3 + 2] photocycloadducts preferentially. In contrast, photoreactions of C-4 linked 1-cyanonaphthalenes produced intramolecular [4 + 2] photocycloadducts as main products along with stereoisomers of tricyclic compounds as minor products. The formation of [4 + 2] photocycloadducts was promoted by using benzophenone or Michler's ketone triplet photosensitization, and quenched by O2 or ferrocene. Intramolecular singlet exciplexes, which serve as important intermediates in the mechanistic pathways for these reactions, governed the site-selectivities in photoreactions of both of the 2- and 4-(5-arylpent-4-enyl)-1-cyanonaphthalenes. In addition, [4 + 2] photocycloadducts were observed to undergo di-π-methane rearrangement under irradiation conditions to produce angular triquinane derivatives.

Enhanced biodegradation and detoxification of malachite green by Trichoderma asperellum laccase: Degradation pathway and product analysis

The central composite design (CCD)-based response surface methodology (RSM) was engaged in optimizing the biodegradation process of malachite green (MG), a potentially toxic dye, by a laccase identified from Trichoderma asperellum with various parameters viz., enzyme concentration, dye concentration, reacting pH and incubation time. The maximal degradation of MG was obtained to be 97.18% under the optimum conditions with the enzyme concentration of 1.50 U/mL, the dye concentration of 122.66 mg/L, pH of 6.75and the incubation time of 98.58 min. The kinetics investigation of MG degradation was studied at various concentrations of MG, and the values of Km and Vmax were determined as 87.50 mg/L and 1.28 mg/L/min, respectively. Through the UV-Visible spectroscopy, FTIR, HPLC and GC-MS/MS analysis, the metabolites during the biodegradation of MG were identified to include Michler's ketone,4-(dimethylamino)benzophenone, 4-aminobenzophenone and 4-(dimethylamino)benzaldehyde, indicating that the hydroxylation, oxidation, deamination and demethylation processes were all involved in this laccase-mediated MG degradation without the formation of leuco-malachite green derivatives. The genotoxicity studies using the Allium cepa assay have further confirmed that the metabolites are less minimally toxic than the untreated MG. Therefore, this T. asperellum laccase-mediated dye degradation possesses the potentially promising biotreatment process.

Photochemical Energy Storage and Electrochemically Triggered Energy Release in the Norbornadiene-Quadricyclane System: UVPhotochemistry and IR Spectroelectrochemistry in a Combined Experiment.

The two valence isomers norbornadiene (NBD) and quadricyclane (QC) enable solar energy storage in a single molecule system. We present a new photoelectrochemical infrared reflection absorption spectroscopy (PEC-IRRAS) experiment, which allows monitoring of the complete energy storage and release cycle by in situ vibrational spectroscopy. Both processes were investigated, the photochemical conversion from NBD to QC using the photosensitizer 4,4'-bis(dimethylamino)benzophenone (Michler's ketone, MK) and the electrochemically triggered cycloreversion from QC to NBD. Photochemical conversion was obtained with characteristic conversion times on the order of 500 ms. All experiments were performed under full potential control in a thin-layer configuration with a Pt(111) working electrode. The vibrational spectra of NBD, QC, and MK were analyzed in the fingerprint region, permitting quantitative analysis of the spectroscopic data. We determined selectivities for both the photochemical conversion and the electrochemical cycloreversion and identified the critical steps that limit the reversibility of the storage cycle.

Synthesis of allyl acrylpimarate by microwave irradiation and phase-transfer catalytic reaction and its UV-curing reactions as a new monomer

The rosin molecules can improve the adhesion and mechanical properties of polymers. It may be introduced either directly or via active functional groups. The focus of this work has been to develop a new method for creating such active functional groups connected to the acrylpimarate molecule by a microwave irradiation and phase-transfer catalytic reaction with allyl chloride. The synthesized monomer was then polymerized under ultraviolet (UV) irradiation. A new polymerization monomer with two functional groups (two allyl groups) has been synthesized through Diels-Alder reaction using levopimaric acid (an important component of rosin) as raw material under microwave irradiation. The yield and gas chromatography on content of the allyl acrylpimarate monomer were 92.2% and 98.6%, respectively. Due to the steric hindrance in the original rosin molecules, two major allyl acrylpimarate isomers in a 1:4 ratio were observed in the monomeric products, as confirmed by two-dimensional nuclear magnetic resonance spectroscopy (2D NMR). UV-curing reaction of the synthesized monomer confirmed that its two functional groups led to a novel polymerization pathway compared with that of the monomer bearing only one allyl group. Conversion of the monomer reached 90% by using Michlers ketone as a photoinitiator. The cured film was composed of a three-dimensional cross-linked polymer due to the bifunctional monomer, and showed good performance in terms of thermal stability, hardness, and chemical resistance.

Synthesis of photoactive single‐chain folded polymeric nanoparticles via combination of radical polymerization techniques and Menschutkin click chemistry

ABSTRACTThis contribution reports that synthesis of polystyrene based photoactive polymeric nanoparticles by radical copolymerization and Menschutkin Chemistry methodology. In the first step, poly(styrene‐co‐chloromethyl styrene) was achieved by thermally initiated radical copolymerizations and subsequently copolymers were reacted to commercially available Type II photoiniator (Michler's ketone) in dilute condition in order to achieve intramolecular crosslinked polymeric nanoparticles. After the characterization studies, polymeric nanoparticles were used for free radical photopolymerization of methacrylic formulations to determine the initiation efficiency. Upon UV irradiation, resulting polymeric nanoparticle lost its globular structure by releasing benzophenone part and transformed into linear copolymer analogue. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017, 55, 1998–2003

Migration of photoinitiators from cardboard into dry food: evaluation of Tenax® as a food simulant

ABSTRACTPhotoinitiators are widely used to cure ink on packaging materials used in food applications such as cardboards for the packaging of dry foods. Conventional migration testing for long-term storage at ambient temperature with Tenax® was applied to paperboard for the following photoinitiators: benzophenone (BP), 4,4ʹ-bis(diethylamino)benzophenone (DEAB), 2-chloro-9H-thioxanthen-9-one (CTX), 1-chloro-4-propoxy-9H-thioxanthen-9-one (CPTX), 4-(dimethylamino)benzophenone (DMBP), 2-ethylanthraquinone (EA), 2-ethylhexyl-4-dimethylaminobenzoate (EDB), ethyl-4-dimethylaminobenzoate (EDMAB), 4-hydroxybenzophenone (4-HBP), 2-hydroxy-4-methoxybenzophenone (HMBP), 2-hydroxy-4ʹ-(2-hydroxyethoxy)-2-methylpropiophenone (HMMP), 2-isopropyl-9H-thioxanthen-9-one (ITX), 4-methylbenzophenone (MBP) and Michler’s ketone (MK). Test conditions (10 days at 60°C) were according to Regulation (EU) No. 10/2011 and showed different migration patterns for the different photoinitiators. The results were compared with the migration in cereals after a storage of 6 months at room temperature. The simulation with Tenax at 60°C overestimated actual migration in cereals up to a maximum of 92%. In addition, the effect of a lower contact temperature and the impact of the Tenax pore size were investigated. Analogous simulation performed with rice instead of Tenax resulted in insufficiently low migration rates, showing Tenax is a much stronger adsorbent than rice and cereals.

Modulating Solubility and Enhancing Reactivity of Photo-Cross-Linkable Poly(styrene sulfonyl azide-alt-maleic anhydride) Thin Films

To formalize our understanding of indiscriminate grafting chemistries as they pertain to cross-linkable polymers and emerging patterning technologies, we designed a new polymer, poly(styrene sulfonyl azide-alt-maleic anhydride) (PSSMA). By modulating its solubility, it can be deposited into smooth, ultrathin films atop polar and nonpolar polymers. Upon heating above 120 °C or exposure to UV light, highly reactive nitrene intermediates are generated from the azide groups which form covalent adducts and cross-link the PSSMA. Azide photolysis and polymer gelation were studied in the context of a statistical model to gain insight into the network outcomes of nitrenes in a polymer film. For every azide group converted to a nitrene in ambient atmosphere, it has an 11% likelihood of grafting to another chain and a 5% chance of causing a scission. These values can be increased over 3-fold by reducing the O2 content by 85%. Alternatively, the effects of quenching by ground-state O2 can be mitigated by adding Michler’s ketone (MK) to the film. PSSMA/MK blend films possess a 39% (±13) likelihood for grafting and 29% (±10) for scission. The higher ratio of scission to grafting is a consequence of the sensitized azides producing triplet-state nitrenes, which favor hydrogen abstraction. These broadly generalizable considerations will be useful to others who wish to maximize light sensitivity in related polymer systems.

Electronic Interactions of Michler's Ketone with DNA Bases in Synthetic Hairpins

The mechanism and dynamics of photoinduced electron transfer in two families of DNA hairpins possessing Michler's ketone linkers have been investigated by means of steady state and time-resolved transient absorption and emission spectroscopies. The excited state behavior of the diol linker employed in hairpin synthesis is similar to that of Michler's ketone in methanol solution. Hairpins possessing only a Michler's ketone linker undergo fast singlet state charge separation and charge recombination with an adjacent purine base, attributed to well-stacked ground state conformations, and intersystem crossing to the triplet state, attributed to poorly stacked ground state conformations. The failure of the triplet to undergo electron transfer reactions on the 7 ns time scale of our measurements is attributed to the low triplet energy and reduction potential of the twisted triplet state. Hairpins possessing both a Michler's ketone linker and a perylenediimide base surrogate separated by four base pairs undergo photoinduced hole transport from the diimide to Michler's ketone upon excitation of the diimide. The efficiency of hole transport is dependent upon the sequence of the intervening purine bases.

Facile Preparation of a Macromolecular Benzophenone Photoinitiator

Photoinitiators play important roles in the preparation of photo-cured resins. Macromolecular as well as reactive photoinitiators have attracted much attention both in industry and in academia due to the disadvantages of conventional small molecular photoinitiators such as volatility and mobility. A macromolecular benzophenone photoinitiator was designed and efficiently synthesized in this study. Hydroxyl-containing Michler's ketone was firstly synthesized in 82% yield, followed by reacting with toluene di-isocyanate (TDI) to prepare polyurethanetype macromolecular benzophenone photoinitiator.

Evaluation of the migration of 15 photo-initiators from cardboard packaging into Tenax® using ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS)

Photo-initiators are widely used to cure ink on packaging materials used in food applications such as plastic films or cartonboards. In migration studies, food simulants are very often used to simulate food, like Tenax®, which is the simulant for dry foodstuffs. In this paper a fast and reliable confirmation method for the determination of the following photo-initiators in Tenax® is described: benzophenone (BP), 4,4´-bis(diethylamino)benzophenone (DEAB), 2-chloro-9H-thioxanthen-9-one (CTX), 1-chloro-4-propoxy-9H-thioxanthen-9-one (CPTX), 2,4-diethyl-9H-thioxanthen-9-one (DETX), 2,2-dimethoxy-2-phenyl acetophenone (DMPA), 4-(dimethylamino)benzophenone (DMBP), 2-ethylanthraquinone (EA), ethyl-4-dimethylaminobenzoate (EDMAB), 1-hydroxylcyclohexyl phenyl ketone (HCPK), 2-hydroxy-4´-(2-hydroxyethoxy)-2-methylpropiophenone (HMMP), 2-isopropyl-9H-thioxanthen-9-one (ITX), 4-methylbenzophenone (MBP), Michler’s ketone (MK), and 4-phenylbenzophenone (PBZ). After the migration study was completed, the simulant Tenax® was extracted using acetonitrile, followed by analysis on ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS). Quantification was carried out using benzophenone-d10 (BP-d10) as internal standard. The presented method is validated in terms of matrix effect, specificity, linearity, recovery, precision and sensitivity, showing the method can detect all photo-initiators at very low concentrations (LOD < 0.125 µg g–1 for all substances). Finally, the procedure was applied to real samples, proving the capabilities of the presented method.

Michler's Ketone as an Interesting Scaffold for the Design of High‐Performance Dyes in Photoinitiating Systems Upon Visible Light

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. image