Benzoin Methyl Ether Research Articles

Capsanthin-iodonium salt system for free radical photopolymerization under LED irradiation

The current photoinitiator (PI) is effective under mercury lamps but exhibits limited selectivity towards different radiation sources, which hinders its compatibility with eco-friendly LED lighting and raises concerns about toxicity and deep coloration. Capsanthin (Cap), with its strong photo-absorption in the 400–500 nm range, utilizes its conjugated structure to align the PI's absorption wavelength with the LED's emission spectrum. This study introduced Cap as a natural photosensitizer (PS) for free radical photopolymerization under LED irradiation. The Cap-based initiation system demonstrated promising photoinitiating capabilities under a 405 nm LED, achieving over 50 % double bond conversion in polymerized monomers. Furthermore, the system's photobleaching properties were exceptional, and its cytotoxicity was significantly lower than that of traditional PIs, such as benzoin methyl ether. The Cap's photochemical behavior under LED irradiation was explored, investigating its photoinitiating capacity and mechanism through fluorescence, photolysis, and electron paramagnetic resonance techniques. This research is vital for developing bio-based photoinitiating systems for photopolymerization in LED light environments.

Fabrication of TMPTMA foams with SiO2 sub-microspheres gradient doped via slope-rotation method

In this paper, we report a novel approach to fabricate gradient doped porous material via the slope-rotation method. By using dibutyl phthalate as the solvent, benzoin methyl ether as the photoinitiator, and silica sub-microsphere as filler, gradient doped trimethylolpropane trimethacrylate (TMPTMA) foams were fabricated after rotating and mixing, ultraviolet curing, and CO2 supercritical drying. The microstructure and gradient distribution of silica fillers were characterized by nitrogen adsorption, scanning electron microscopy, UV–visible absorption spectrum, and thermogravimetric analysis. The mechanical property was obtained by dynamic mechanical analysis. The results indicated that the approach was an effective method to fabricate gradient doped TMPTMA foams and had the potential to prepare any kind of gradient doped porous material derived from a sol–gel process. The mechanical property was further reinforced by gradient doping of silica sub-microspheres.

Facile fabrication of gradient density organic aerogel foams via density gradient centrifugation and UV curing in one-step

Gradient density porous materials have played an important role in areas of aerospace, biomaterials and high-energy absorption experiments. In order to accurately control the process of gradient forming, a new approach was proposed to produce gradient density porous materials. By using dibutyl phthalate as the solvent and benzoin methyl ether as the photoinitiator, gradient density trimethylolpropane trimethacrylate (TMPTMA) foams were fabricated after the density gradient centrifugation, ultraviolet curing and CO2 supercritical drying. The microstructure and density distribution of foams were characterized by nitrogen adsorption, mercury injection apparatus test, scanning electron microscopy, UV–visible absorption spectrum, X-ray phase contrast, and dynamic mechanical analysis. Moreover, the storage modulus of organic foams was significantly improved by the gradient change of foam density. The results indicated that this approach was an effective method for the preparation of gradient density organic foams and could be suitable for producing gradient density porous materials derived from a sol–gel process. We presented a new approach for the preparation of gradient density TMPTMA aerogel foams via density gradient centrifugation and UV curing in one-step. It was the first report so far to rationally design and facilely fabricate TMPTMA foams. The results definitively proved the density distribution of a linear gradient for foams. The approach could be simple and suitable for producing other gradient density porous materials derived from a sol–gel process. Different gradient parameters of TMPTMA foams could be obtained by monitoring the target density of mixture solutions, the sloping angle, and the size of the tube, respectively. Furthermore, it could be seen that the method of analyzing absorbance was actually a suitable tool to observe the density distribution of TMPTMA foams, which showed an intuitionistic figure to realize the density distribution. As a result, it could be believed that this approach could be useful for fabrication of gradient density porous materials in future.

Synthesis and characterization of Cu/Cr hydrotalcite-like compounds and their highly efficient application in catalytic synthesis of benzoin methyl ether

Benzoin methyl ether (BME) is an important photosensitizer for coatings and printing technologies, and Cu/Cr hydrotalcite-like compounds (CuCr-HTLcs) is promising to be used as pollution-free catalyst for BME synthesis. However, little is known about effect of CuCr-HTLcs structure on catalytic synthesis of BME. In this work, a series of CuCr-HTLcs with different ratios of Cu to Cr (nCu/nCr) was successfully prepared by a co-precipitation method. The structure of CuCr-HTLcs were systematically characterized. The copper and chromium in CuCr-HTLcs mainly exist in the form of Cu2+ and Cr3+, respectively. The nCu/nCr has significant effects on crystallinity, acidity, and textural properties of CuCr-HTLcs. Subsequently, catalytic performance of CuCr-HTLcs was tested for BME synthesis. We found that BME synthesis is mainly influenced by combined effects of acid-site concentration and pore size. Moderate acid-site concentration and pore size (mesopores) are the critical factors for improving catalytic activity of CuCr-HTLcs and BME selectivity.

Grafting of Acrylamide onto Polysaccharides Blend Using Photo-initiators

The present paper comprises of hydrogel synthesis processes using a blend of three natural polysaccharides (PsB) “starch, chitosan and alginate” grafted acrylamide (PsB-g-Am) using ultraviolet (UV) irradiation. The grafting process has been undergo using three different photo-initiators [Dimethoxy-2-phenylacetophenone (DMPA), benzoin methyl ether (BME) and benzophenone (BP)]. Furthermore, different PsB/Am weight ratios have been used. The prepared hydrogel has been characterized using XRD and SEM. Grafting percentage (%G), grafting efficiency (%GE), grafting yield (%GY) also have been compared. Among the three used photo-initiators, DMPA gave the maximum attained values of %G (130 %), %GE (72 %) and %GY (89 %) followed by BME and BP, respectively. Swelling water ratio (SWR) for the grafted hydrogels in distilled water (DW) has been studied. Grafted hydrogel using DMPA photo-initiator gave the maximum SWR of 30 g/g. Am/PsB weight ratio and the used photo-initiator had a direct effect on SWR of the produced hydrogel.

Response surface optimization of miniemulsion: application to UV synthesis of hexyl acrylate nanoparticles

This paper presents the UV synthesis in miniemulsion of nanoparticles from hexyl acrylate monomers using radical photoinitiator type I benzoin methyl ether. The optimization of such a miniemulsion composition is studied to produce monodisperse nanoparticles with a mean size d p inferior to 200 nm after photopolymerization of the droplets. The correlation between the size distributions of the droplets and the corresponding nanoparticles was verified. Therefore, a composite design was built as regards to the amount of the surfactant (sodium dodecyl sulfate), the co-stabilizer (pentadecane), and the monomer (hexyl acrylate) in order to model the mean size and the polydispersity of the miniemulsion droplets. A range of monodisperse droplets size between 150 and 175 nm was achieved. After UV irradiation, high monomer conversion yield (>90 %) was reached leading to nanoparticles with mean size ranging from 100 to 165 nm. These hexyl acrylate nanoparticles have been obtained after 10 min of irradiation, offering new opportunities for nanoparticles synthesis in enclosed and/or plastic vessels.

Highly Selective One-Pot Synthesis of Benzoin Ether Compounds on Ni- AlCe-Hydrotalcite Catalysts

In this study, benzoin methyl ether and benzoin ethyl ether were highly selectively synthesized in one-pot reaction using the reusable NiAlCe-hydrotalcite catalysts, where the benzoin ether compounds are traditionally obtained in two steps through condensation and etherification. The high crystallinity NiAlCe-hydrotalcites with different Ni2+/Al3+/Ce3+ ratios were facilely synthesized by the coprecipitation method under a constant pH value. The reaction parameters (e.g., different Ni2+/Al3+/Ce3+ ratios, reaction time, temperature, amount and the stability of catalyst) were studied in details and it was found that the Ni2+/Al3+/Ce3+ ratios, reaction temperature and the reaction medium play crucial influence on the catalytic activity and products distribution. 99.2% selectivity of benzoin methyl ether was achieved at 85.4% conversion of benzaldehyde and 98.3% selectivity was obtained at 63.7% conversion using a NiAlCe-hydrotalcite catalyst with the Ni2+/Al3+/Ce3+ ratio of 22:10:1, respectively. Besides, NiAlCe-hydrotalcite catalysts were easily recycled through a simple separation process and show high stability over three consecutive runs.

A fluorous porous polymer monolith photo‐patterned chromatographic column for the separation of a flourous/fluorescently labeled peptide within a microchip

A fluorous porous polymer stationary phase is photo-patterned within a glass microfluidic chip to conduct CEC. During free radical-initiated polymerization, extraneous polymer forms and contributes to excessive microfluidic channel clogging. Nitrobenzene is explored as free radical quencher to limit clogging by minimizing extraneous polymer formation and a number of initiator to quencher ratios are explored with a 0.5:1 quencher (nitrobenzene): initiator (benzoin methyl ether) molar ratio shown to be optimal. The microchip patterned with a fluorous monolith was used to carry out the electrochromatographic analysis of a mixture containing fluorescent and fluorous labeling products. The fluorous monolithic column shows fluorous selectivity for compounds labeled with perfluoromethylene tags and a custom peptide is synthesized that possesses functional groups that can be both fluorescently and fluorously labeled. MALDI MS was used to identify the labeled fragments and microchip based electrochromatography was used to analyze the resulting labeling mixture. This is the first report to our knowledge that uses fluorous porous polymer monolith within a microchip to separate analytes using fluorous-fluorous interactions.

New “one-step” method for the simultaneous synthesis and anchoring of organic monolith inside COC microchip channels

A new method for monolith synthesis and anchoring inside cyclic olefin copolymer (COC) microchannels in a single step is proposed. It is shown that type I photoinitiators, typically used in a polymerization mixture to generate free radicals during monolith synthesis, can simultaneously act as type II photoinitiators and react with the plastic surface through hydrogen abstraction. This mechanism is used to "photograft" poly(ethylene glycol) methacrylate (PEGMA) on COC surfaces. Contact angle measurements were used to observe the changes in surface hydrophilicity when increasing initiator concentration and irradiation duration. The ability of type I photoinitiators to synthesize and anchor a monolith inside COC microchannels in a single step was proved through SEM observations. Different concentrations of photoinitiators were tried. Finally, electrochromatographic separations of polycyclic aromatic hydrocarbons were realized to illustrate the beneficial effect of anchoring on chromatographic performances. The versatility of the method was demonstrated with two widely used photoinitiators: benzoin methyl ether (BME) and azobisisobutyronitrile (AIBN).

Comparison of Copper and Vanadium Homogeneous Catalysts for Aerobic Oxidation of Lignin Models

The reactivity of copper and vanadium catalysts toward the aerobic oxidation of lignin models has been explored. Both (dipic)VV(O)(OiPr) (3) (dipic = dipicolinate) and CuCl/TEMPO (TEMPO = tetramethylpiperidine N-oxide) catalyzed the aerobic oxidation of the lignin model compound 1,2-diphenyl-2-methoxyethanol (2). The vanadium catalyst 3 produced benzoic acid (85%) and methyl benzoate (84%) as the major products via the intermediate ketone benzoin methyl ether (4). The copper catalyzed reaction afforded benzaldehyde (84%) and methylbenzoate (88%) directly, with no intermediate formation of 4. The more complex lignin model system 1-(3,5-dimethoxyphenyl)-2-(2-methoxyphenoxy)propane-1,3-diol-[2,3-13C2] (5-13C2) was oxidized under air by vanadium catalyst 3, affording ketone 7-13C2 (65%), dehydrated ketone 8-13C2 (5%), alkene product 9-13C2 (14%), 3,5-dimethoxybenzoic acid (11%), 3,5-dimethoxybenzaldehyde (2%), 2-methoxyphenol, and formic acid-13C1 (4%). Aerobic oxidation of ketone 7-13C2 using catalyst 3 prod...

Chiral micellar electrokinetic chromatography‐atmospheric pressure photoionization of benzoin derivatives using mixed molecular micelles

In the present work we report, for the first time, the successful on-line coupling of chiral MEKC (CMEKC) to atmospheric pressure photoionization MS (APPI-MS). Four structurally similar neutral test solutes (e.g. benzoin (BNZ) derivatives) were successfully ionized by APPI-MS. The mass spectra in the positive ion mode showed that the protonated molecular ions of BNZs are not the most abundant fragment ions. Simultaneous enantioseparation by CMEKC and on-line APPI-MS detection of four photoinitiators, hydrobenzoin, BNZ, benzoin methyl ether, benzoin ethyl ether, were achieved using an optimized molar ratio of mixed molecular micelle of two polymeric chiral surfactants (polysodium N-undecenoxy carbonyl-L-leucinate and polysodium N-undecenoyl-L,L-leucylvalinate). The CMEKC conditions, such as voltage, chiral polymeric surfactant concentration, buffer pH, and BGE concentration, were optimized using a multivariate central composite design (CCD). The sheath liquid composition (involving %v/v methanol, dopant concentration, electrolyte additive concentration, and flow rate) and spray chamber parameters (drying gas flow rate, drying gas temperature, and vaporizer temperature) were also optimized with CCD. Models built based on the CCD results and response surface method were used to analyze the interactions between factors and their effects on the responses. The final overall optimum conditions for CMEKC-APPI-MS were also predicted and found in agreement with the experimentally optimized parameters.

Aerobic Oxidation of Lignin Models Using a Base Metal Vanadium Catalyst

Dipicolinate vanadium(V) complexes oxidize lignin model complexes pinacol monomethyl ether (A), 2-phenoxyethanol (B), 1-phenyl-2-phenoxyethanol (C), and 1,2-diphenyl-2-methoxyethanol (D). With substrates having C-H bonds adjacent to the alcohol moiety (B-D), the C-H bond is broken in pyridine-d(5) solvent, yielding 2-phenoxyacetaldehyde from B, 2-phenoxyacetophenone from C, and benzoin methyl ether from D. In DMSO-d(6) solvent the reaction is slower, and both C-H and C-C bond cleavage products are observed for D. The vanadium(IV) products of these reactions have been identified and characterized. Catalytic oxidation of C and D has been demonstrated using air and (dipic)V(O)O(i)Pr. For both substrates, the C-C bond between the alcohol and ether groups is broken in the catalytic oxidation. 1-Phenyl-2-phenoxyethanol is oxidized to a mixture of phenol, formic acid, benzoic acid, and 2-methoxyacetophenone. The products of oxidation of 1,2-diphenyl-2-methoxyethanol depend on the solvent; in DMSO benzaldehyde and methanol are the major products, while benzoic acid and methyl benzoate are the major products obtained in pyridine solvent. Phenyl substituents on the model complex facilitate the oxidation, with relative rates of oxidation D > C > B.

Achiral and chiral separations using MEKC, polyelectrolyte multilayer coatings, and mixed mode separation techniques with molecular micelles.

Mixed mode (MM) separation using a combination of MEKC and polyelectrolyte multilayer (PEM) coatings is herein reported for the separation of achiral and chiral analytes. Many analytes are difficult to separate by MEKC and PEM coatings alone. Therefore, the implementation of a MM separation provides several advantages for overcoming the limitations of these well-established methods. In this study, it was observed that achiral separations using MEKC and PEM coatings individually resulted in partial resolution of eight very similar aryl ketones when the molecular micelle (sodium poly(N-undecanoyl-L-glycinate)) concentration was varied from 0.25 to 1.00% w/v and the bilayer number varied from 2 to 4. However, when MM separation was introduced, baseline resolution was achieved for all eight analytes. In the case of chiral separations, temazepam, aminoglutethimide, benzoin, benzoin methyl ether, and coumachlor were separated using the three separation techniques. For chiral separations, the chiral molecular micelle, sodium poly(N-undecanoyl-L-leucylvalinate), was employed at concentrations of 0.25-1.50% w/v for both MEKC and PEM coatings. Overall, the results revealed partial separation with MEKC and PEM coatings individually. However, MM separation enabled baseline separation of each chiral mixture. The separation of achiral and chiral compounds from different compound classes demonstrates the versatility of this MM approach.

Preparation of a Crosslinked Bioimprinted Lipase for Enrichment of Polyunsaturated Fatty Acids from Fish Processing Waste

Geotrichum sp. lipase modified with a combined method composed of crosslinking and bioimprinting was employed to selectively hydrolyze waste fish oil for enrichment of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) in glycerides. Crosslinked polymerization by monomer (polyethylene glycol 400 dimethyl acrylate), crosslinker (trimethylolpropane trimethylacrylate), and photoinitiator (benzoin methyl ether) coupled to bioimprinting using palmitic acid as imprint molecule, resulted in much more effective enzyme preparation used in aqueous hydrolysis reaction. Since the crosslinked polymerization modification maintained bioimprinted property and gave good dispersion of enzyme in reaction mixture, the crosslinked bioimprinted enzyme exhibited higher hydrolysis temperature, enhanced specific activity, shorter hydrolysis time, and better operational stability compared to free lipase. Crude fish oil was treated at 45 degrees C with this crosslinked bioimprinted lipase for 8 h, and 46% hydrolysis degree resulted in the production of glycerides containing 41% of EPA and DHA (EPA+DHA), achieving 85.7% recovery of initial EPA and DHA. The results suggested that bioimprinted enzymes did not lose their induced property in aqueous environment when prepared according to the described crosslinking-bioimprinting method. It could also be seen that the crosslinked bioimprinted lipase was effective in producing glycerides that contained a higher concentration of polyunsaturated fatty acid with better yield.

Direct Photolithographic Patterning of Electrospun Films for Defined Nanofibrillar Microarchitectures

In this letter, a method of generating spatially defined electrospun microarchitectures by direct photolithographic patterning of electrospun films is described. A photoinitiator, benzoin methyl ether, is incorporated into a solid thermoplastic electrospun polyurethane matrix selectively photo-cross-linked by standard photolithographic methods. Subsequent development in an organic solvent yields spatially defined electrospun microstructures on a single substrate. Utilizing a multilayer approach, the method allows for the assembly of complex hierarchical electrospun structures on single substrates using methods analogous to the conventional microfabrication of solid-state devices.

Effect of temperature during photopolymerization of capillary monolithic columns

Polymeric monolithic capillary columns were synthesized using butyl methacrylate (BMA), ethylene glycol dimethacrylate (EDMA), and 2-acrylamido-2-methylpropanesulfonic acid (AMPS) as monomers and 1,4-butanediol, 1-propanol, and water as a porogen mixture. The synthesis was performed over a wide temperature range from -15 degrees C to +70 degrees C using UV radiation to trigger the polymerization process initiated by benzoin methyl ether (BME). The columns exhibited different hydrodynamic properties (permeability) as well as efficiency. The most efficient and the most permeable columns were those polymerized at low temperatures (-15 degrees C to +10 degrees C). The columns photopolymerized at higher temperatures (T > or = 30 degrees C) were completely useless because of low permeability or efficiency. The presented results indicate that temperature can be another factor which allows control of porosity during the preparation of monoliths by photopolymerization.

Asymmetric Hydrogenation of Aromatic Ketones Catalyzed by the TolBINAP/DMAPEN−Ruthenium(II) Complex: A Significant Effect ofN-Substituents of Chiral 1,2-Diamine Ligands on Enantioselectivity

Asymmetric hydrogenation of acetophenone in the presence of Ru(II) catalysts coordinated by TolBINAP and a series of chiral 1,2-diamines was studied. The sense and degree of enantioselectivity were highly dependent on the N-substituents of the diamine ligands. The N-substituent effect was discussed in detail. Among these catalysts, the (S)-TolBINAP/(R)-DMAPEN-Ru(II) complex showed the highest enantioselectivity. The mode of enantioface selection was interpreted by using transition state models based on the X-ray structure of the catalyst precursor. The chiral catalyst effected the hydrogenation of alkyl aryl ketones and arylglyoxal dialkyl acetals to afford the chiral alcohol in >99% ee in the best cases. Hydrogenation of racemic benzoin methyl ether with the chiral catalyst through dynamic kinetic resolution gave the anti-alcohol (syn:anti = 3:97) in 98% ee, while the reaction of alpha-amidopropiophenones resulted in the syn-alcohols (syn:anti = 96:4 to >99:1) in >98% ee.

Fast preparation of photopolymerized monolithic columns for capillary electrochromatography

Photopolymerized sol-gel(PSG) columns were prepared using methacryloxypropyltrimethoxysilane as the monomer, toluene as the porogen and hydrochloric acid as the catalyst. Four different photoinitiators such as benzoin methyl ether, Irgacure 819, Irgacure 1700 and Irgacure 1800 were comparatively used in the reaction solution in the presence and absence of sodium dodecyl sulfate. The above eight solutions were respectively irradiated at 365 nm for 5–10 min in each capillary (75 μm inside diameter) to prepare the porous monolithic sol-gel column by a one-step, in situ, process. The chromatographic behavior of the eight PSG columns were comparatively studied, all of which exhibit reversed-phase character. Using these columns, several neutral compounds, namely thiourea, benzene, toluene, ethyl benzene, biphenyl and naphthalene can be separated from mixtures with a largest column efficiency of 74 470 plate/column for thiourea. Addition of sodium dodecyl sulfate in the polymerization process has a significant influence on the morphology and migration time.

Preparation, Characterization, and Catalytical Application of MgCoAl-Hydrotalcite-Like Compounds

MgCoAl-hydrotalcite-like compounds (MgCoAl-HTLcs) were synthesized using the copre- cipitation method of variable pH values. The effect of each factor on the preparation of HTLcs was discussed systematically, which included pH values, mole ratios of Mg 2+ to Co 2+, the concentrations of the solution, and the temperature and time of the hydrothermal treatment. Besides, the thermal de- composition of MgCoAl-HTLcs was discussed. X-ray diffraction, thermogravimetric analysis, and FT-IR spectroscopy were performed to characterize the MgCoAl-HTLcs samples. The results showed that when the pH = 7.6–8.5 or 5.5–6.2, atomic ratios of (Mg 2++Co 2+)/Al 3+ =2andMg 2+/Co 2+ ranging from 1.00 to 2.00, temperature and time of hydrothermal treatment being 110 °C and 6 h, unique MgCoAl-HTLcs with high crystallinity could be obtained. When the calcination temperature was up to 250 °C, the MgO phase was detected coexisting with Al 2O 3 and MgAl 2O 4 was highly spreaded on the derived mixed oxides. The synthesis reaction of benzoin methyl ether with methanol and benzaldehyde was chosen to study the catalytic activity of MgCoAl-HTLcs. The catalyst showed high activity and high stability in the synthesis of benzoin methyl ether in the feasible condition.

Efficient synthesis of benzoin methyl ether catalyzed by hydrotalcite containing cobalt

An efficient synthesis of benzoin methyl ether with benzaldehyde and methanol in the presence of MgCoAl–hydrotalcite catalyst has been developed. By this new method, not only the cyanide poisoning is avoided, but also the synthesis of benzoin methyl ether can be completed in one step instead of the traditional two steps with both condensation and etherification. A new way for major industrial processes to synthesize clean benzoin methyl ether was explored.