Presence Of Acrylate Research Articles

Highly Efficient Photoinitiation Systems Based on Dibenzo[a,c]phenazine Sensitivity to Visible Light for Dentistry.

In this work, photoinitiation systems based on dibenzo[a,c]phenazine sensitivity to visible light were designed for their potential application in dentistry. Modification of the structure of dibenzo[a,c]phenazine consisted of introducing electron-donating and electron-withdrawing substituents and heavy atoms into position 11. The synthesized compounds are able to absorb radiation emitted by dental lamps during photoinitiation of the polymerization process. In the presence of acrylates, dibenzo[a,c]phenazines show excellent photoinitiating abilities in systems containing an electron donor or a hydrogen-atom donor as a second component. The developed systems initiate the polymerization process comparable to a commercial photoinitiator, i.e., camphorquinone. Moreover, the performed studies showed a significant shortening of the polymerization time and a reduction in the amount of light absorber. This indicates that polymeric materials are obtained at a similar rate despite a significant reduction in the concentration of the newly developed two-component photoinitiating systems.

Utilization of carbon dioxide for preparation of polyurethane coatings without using the toxic isocyanates

Carbon dioxide (CO2) which is an infinite carbon resource in gaseous form is utilized for many industrial purposes and for the synthesis of materials. In this work, it is being used for the preparation of polyurethanes (PU) using 2-dioxolone (cyclic carbonate) and amine chemistry. Since the conventional polyurethanes are synthesized by the reaction of polyols and the toxic diisocyanates, there is need of adopting an environment-friendly route. Glycidyl methacrylate (GMA) was copolymerized with methyl methacrylate and butyl acrylate in presence of azobisisobutyronitrile as initiator and dimethyl sulfoxide (DMSO) as solvent. In parallel, by reacting with CO2 the epoxide groups of glycidyl methacrylate were converted into 2-dioxolone groups, using tetrabutylammonium bromide (TBAB) as a catalyst. When these 2-dioxolone groups present in the polymer structure were reacted with the primary diamine group of a curing agent, urethane linkage was created without using the toxic isocyanates. The Fourier Transform Infra-Red (FTIR) Spectroscopy reports confirmed the respective conversions. The polyurethane films thus formed after baking, were evaluated for mechanical properties, gloss, and water resistance, and found to be suitable for the topcoat application. This method thus utilizes CO2 for the transformation of epoxide groups to urethane linkages.

Synthesis of polyester thermosets via internally catalyzed Michael-addition of methylene compounds on a 2-(trifluoromethyl)acrylate-derived building block

The Michael-addition reaction of methylene compounds has been known and used for>120 years in organic chemistry synthesis. We report herein a new type of application for this reaction: the preparation of thermosets by catalyst-free bis-Michael addition. In this study, the addition of various methylene C-nucleophiles on tert-butyl 2-(trifluoromethyl)acrylate in presence of a tertiary amine was preliminary evaluated. Then, a tris-2-(trifluoromethyl)acrylate monomer incorporating a tertiary amine was synthesized and used with methylene monomers to prepare innovative polyester networks at temperature going from 25 °C to 100 °C. Finally, the resulting fluorinated carbon-Michael networks were characterized by FTIR, differential scanning calorimetry, thermal gravimetry, dynamic mechanical and swelling analyses. These thermosets exhibited high gel content (>86 %) and good thermo-mechanical properties with a rubbery plateau above 7 MPa and a glass transition temperature above 44 °C. The material thermal properties could be adapted to a targeted application (binder or coating) by the choice of the methylene compound used in the thermoset formulation.

Acrylate protects a marine bacterium from grazing by a ciliate predator.

Cleavage of dimethylsulfoniopropionate (DMSP) can deter herbivores in DMSP-producing eukaryotic algae; however, it is unclear whether a parallel defence mechanism operates in marine bacteria. Here we demonstrate that the marine bacterium Puniceibacterium antarcticum SM1211, which does not use DMSP as a carbon source, has a membrane-associated DMSP lyase, DddL. At high concentrations of DMSP, DddL causes an accumulation of acrylate around cells through the degradation of DMSP, which protects against predation by the marine ciliate Uronema marinum. The presence of acrylate can alter the grazing preference of U. marinum to other bacteria in the community, thereby influencing community structure.

Conversion layers by plasma-electrolytic oxidation of aluminum in acrylate and benzoate electrolytes

Within this work, aluminum is oxidized via plasma-electrolytic oxidation (PEO) in the presence of organic substances, including reactive monomers. The aim of this approach is to generate polymers and simultaneously bind them to the surface of the freshly generated oxide layers. For this purpose, sheets of aluminum were immersed into electrolytes that comprised either 4 % of sodium acrylate or 10 % of sodium benzoate. The aluminum sheets were oxidized by anodic pulse current at 0.25 A/cm2 for 30–90 s. By this process, predominantly oxidic conversion layers were produced. The presence of the monomers in the electrolyte influenced the passivation and discharge behavior and finally the microstructure of the layers. It further gave rise to organic material in the layer. In particular, infrared attenuated total reflection spectroscopy (ATR-IR) and X-ray photoemission spectroscopy (XPS) show that layers which were generated in the presence of acrylate or benzoate comprised -C-C-, -C=C-, -C-O, and C=O bonds.

Preparation of Hexamethyldisilazanomethacryloxyphenyl ketone (HDMK) and its copolymerization in the presence of acrylates

PurposeThis paper aims to improve some properties of poly (methyl methacrylate) by copolymerization with butyl acrylate (BA) monomer along with the incorporation of the stable and economical synthesized silicone-containing monomer hexamethyldisilazanomethacryloxyphenyl ketone (HDMK) into the copolymer matrix.Design/methodology/approachFor this target solution copolymerization of methyl methacrylate (MMA), BA and HDMK were carried out using a 250 mL four-necked round-bottom flask. Before solution polymerization start-up, the reaction vessel was first charged with 34.8 mL toluene and heated to 170 °C with stirring and reflux cooling. A monomer mixture of 25.86 g (260 mmol) MMA, 26.40 g (200 mmol) BA, 3.00 g (8.60 mmol) HDMK and 0.45 g (2.00 mmol) dibenzoyl peroxide was added continuously from the dropping funnel over a period of 4 h.FindingsThe HDMK was successfully synthesized and the water resistance of acrylic resins was improved because of the existence of HDMK.Research limitations/implicationsThe materials that were used in this research paper had a reasonably low cost. Also, the procedures for synthesis of monomers and polymers were extremely easy because there was no need for high pressure or temperature and no dangerous solvents were used.Practical implicationsThe acrylic resin that contained HDMK was used to synthesis a white architectural paint for exterior coating. Examining the paint characteristics has shown acceptable washing and abrasion resistance, good brushing, excellent storage stability and great surface coating.Originality/valueHDMK was synthesized for the first time.

Multicomponent domino protocol for the stereoselective synthesis of novel pyrrolo[3,2-c]quinolinone hybrid heterocycles

A series of structurally intriguing novel pyrrolo[3,2-c]quinolinone heterocyclic hybrids have been synthesized for the first time via a one-pot multicomponent domino reaction sequence that involves a 1,3-dipolar cycloaddition and two subsequent annulation steps. Baylis-Hillman adducts derived from various substituted benzaldehyde and methyl acrylate in presence of DABCO were used as a dipolarophiles, while the 1,3-dipole components were azomethine ylides, formed in situ from isatin derivatives and l-phenylalanine. The reaction generated five new bonds, three new rings and four contiguous stereocenters, which were created with full diastereomeric control.

Engineered polyester-PEG nanoparticles prepared through a “grafting through” strategy and post-functionalization via Michael type addition

Free radical polymerization (FRP) is widely used in industrial processes as an efficient and versatile method to engineer polymeric nanoparticles (PNPs) of controlled size, narrowly distributed, and of well-defined surface properties. Functional Poly(ε-caprolactone) (PCL) and poly(lactic acid) (PLA) can be utilized as macromonomers in FRP in combination with a co-polymerizable poly(ethylene glycol) (PEG), to achieve aqueous dispersions of PNPs composed of a hydrophobic polyester core and a hydrophilic PEG shell of tuneable size. For several industrial and biological applications, PNPs also need surface functionalization to provide specific physicochemical characteristics, including stimuli-responsiveness, and bioactivity.In this work, a flexible “grafting through” strategy based on Ring opening polymerization (ROP) and FRP was proposed to obtain engineered polyester-PEG nanoparticles functionalized with acrylate groups on the hydrophilic shell. The presence of acrylates allows a versatile surface functionalization through Michael-type addition with a thiolated ligand (peptide), in aqueous solution under physiological pH, with the advantage of high conversion and absence of reaction side products. A cysteine-containing cyclic RGD was used as model peptide for conjugation, due to its potential application as ligand for endothelial cells. Results indicated that active cell targeting can be achieved by using this surface functionalization approach.

In-situ Water Based Emulsion Copolymerization of Styrene/ Ethylhexyl Acrylate in Presence of Cloisite 15A

Nowadays, due to the outstanding chemical and physical properties of nanomaterials such as montmorillonite, which is resulted from increased surface area to volume ratio of montmorillonite platelets (high aspect ratio), they are using in many applications for fabrication of special products having higher barrier properties and so on. Major challenge in this work is dispersing well of nanoclay sheets within the polymeric matrix completely, to obtain the best structure (with high degree of intercalation and exfoliation). In this paper, we synthesized poly (styrene-co-2-ethylhexyl acrylate) / montmorillonite in order to receive a well dispersed structure of nanocomposite through in-situ emulsion copolymerization in water. The FTIR method was used to characterize the copolymer structure. The dispersion of nanoparticles through polymer matrix was characterized by X-ray diffraction (XRD) for samples having nanoclay. The dispersibility and size of MMT particles was investigated by using scanning electron microscopy (SEM) for obtained nanocomposite. In all cases we obtained reasonable polymer conversions up to 98% which was calculated by gravimetrical measurements.

Screening of metagenomic and genomic libraries reveals three classes of bacterial enzymes that overcome the toxicity of acrylate.

Acrylate is produced in significant quantities through the microbial cleavage of the highly abundant marine osmoprotectant dimethylsulfoniopropionate, an important process in the marine sulfur cycle. Acrylate can inhibit bacterial growth, likely through its conversion to the highly toxic molecule acrylyl-CoA. Previous work identified an acrylyl-CoA reductase, encoded by the gene acuI, as being important for conferring on bacteria the ability to grow in the presence of acrylate. However, some bacteria lack acuI, and, conversely, many bacteria that may not encounter acrylate in their regular environments do contain this gene. We therefore sought to identify new genes that might confer tolerance to acrylate. To do this, we used functional screening of metagenomic and genomic libraries to identify novel genes that corrected an E. coli mutant that was defective in acuI, and was therefore hyper-sensitive to acrylate. The metagenomic libraries yielded two types of genes that overcame this toxicity. The majority encoded enzymes resembling AcuI, but with significant sequence divergence among each other and previously ratified AcuI enzymes. One other metagenomic gene, arkA, had very close relatives in Bacillus and related bacteria, and is predicted to encode an enoyl-acyl carrier protein reductase, in the same family as FabK, which catalyses the final step in fatty-acid biosynthesis in some pathogenic Firmicute bacteria. A genomic library of Novosphingobium, a metabolically versatile alphaproteobacterium that lacks both acuI and arkA, yielded vutD and vutE, two genes that, together, conferred acrylate resistance. These encode sequential steps in the oxidative catabolism of valine in a pathway in which, significantly, methacrylyl-CoA is a toxic intermediate. These findings expand the range of bacteria for which the acuI gene encodes a functional acrylyl-CoA reductase, and also identify novel enzymes that can similarly function in conferring acrylate resistance, likely, again, through the removal of the toxic product acrylyl-CoA.

Semi-continuous emulsion copolymerization of vinyl acetate and butyl acrylate in presence of AMPS

The emulsifier-free emulsion polymerization of vinyl acetate (VAc) and butyl acrylate (BA) in the presence of 2-acrylamido-2-methylpropane sulfonic acid (AMPS) was carried out by a semi-continuous process. AMPS was a reactive surfactant in the aqueous emulsion, due to its amphiphilic structure and the unsaturated double bonds. Potassium persulfate (KPS) was used as initiator. The following factors were mainly examined: quantity of AMPS, BA and KPS concentrations, which could significantly affect the particle size and its distribution, conversion, gel content, minimum film-forming temperature, etc. The particle size and its distribution were characterized by dynamic laser particle size analyzer, and morphology of the latex particles was characterized by transmission electron microscopy (TEM). Fourier transform infrared spectroscopy was used to characterize chemical structure of copolymers. The results indicated that AMPS was successfully reacted onto the resulted copolymer of vinyl acetate and butyl acrylate. A hydrophilic sulfonic acid group in the molecular structure of AMPS tended to be distributed in particles surface after polymerization. As a result, an electrostatic repulsion between the particles was produced in order to maintain stability of the system. Thermogravimetric analysis curves suggested that as BA content increased, thermal stability of the polymer increased accordingly. The conversion-time plots with varying AMPS and initiator contents were obtained, which illustrated that the initiator concentration could greatly influence the polymerization rate and the final conversion. The TEM micrographs of the final emulsifier-free latex particles for P(VAc/BA/AMPS) system revealed small particle size in monodisperse polymer latex. The particles of the latex were measured as about 150 nm.

ChemInform Abstract: Mizoroki—Heck Reactions of Methyl Acrylate in Presence of a Palladated Rasta Resin.

AbstractMizoroki—Heck cross‐couplings of aryl iodides (I) in the presence of a Pd‐catalyst supported on a rasta resin bearing diphenylphosphanyl ligands are reported.

Mizoroki–Heck reactions of methyl acrylate in presence of a palladated rasta resin

Abstract Mizoroki–Heck cross-couplings of aryl halides in the presence of a palladium catalyst supported on a rasta resin bearing diphenylphosphanyl ligands are reported. In particular, we show that tiny amounts of soluble palladium species leached from the polymeric support catalyze the reaction. A one-pot two steps preparation of alkenes from aryl bromides using a Finkelstein halogen exchange reaction is also described.

Relative reactivity and selectivity of vinyl sulfones and acrylates towards the thiol–Michael addition reaction and polymerization

The reactivity, selectivity and kinetics of vinyl sulfones and acrylates in base and nucleophile-catalyzed thiol–Michael addition reactions were examined in detail in this study. The vinyl sulfones react selectively and more rapidly with thiols in the presence of acrylates, which was clearly indicated from reactions of hexanethiol (HT), ethyl vinyl sulfone (EVS) and hexyl acrylate (HA) at a molar ratio of 2 : 1 : 1. EVS reaches 100% conversion with minimal consumption (<10%) of HA, which demonstrates the high selectivity of vinyl sulfones over acrylates. The reaction rate of EVS with HT was approximately 7 times higher than that of HA. A detailed study of the kinetics of the nucleophile-catalyzed thiol–Michael addition reaction was carried out, and it was shown that the delay observed in the initial stages of the nucleophile-catalyzed thiol–Michael addition reaction is due to the relatively slow attack of the nucleophiles on the vinyl. The presence of protic species other than thiols in the reaction mixture has also been shown to significantly impede the reaction rate, and in extreme cases, has been shown to inhibit the Michael addition reaction. These results provided a better understanding of the conditions under which the thiol–Michael addition reaction can or cannot be considered as a click reaction. Finally, the high reaction selectivity of vinyl sulfones over acrylates via thiol–Michael addition reaction in ternary systems is used to control gelation behavior in crosslinked polymer networks formed by thiol–Michael addition reactions.

Shear Stability of EOR Polymers

Summary An experimental study of shear stability of several high-molecular-weight polymers used as mobility-control agents in EOR projects has been performed in well-controlled conditions. The shearing device was made of a capillary tube with an internal diameter (ID) of 125 μm, through which polymer solution was injected at a controlled rate. The setup enables a precise measurement of the shear rate to which the polymer macromolecule is submitted. The degradation rate was measured by the viscosity loss induced by the passage into the capillary tube. The shear rate was gradually increased up to 106 sec–1 while checking degradation rate at each stage. Different commercial EOR polymer products were submitted to the test with polyacrylamide backbone and different substitution monomer groups. All macromolecules behave as flexible coils in solution. The parameters investigated were Molecular weight (between 6 and 20×106)Nature of substitution group (acrylate, ATBS/sulfonate, nVP/ vinyl-pyrrolidone)Salinity Polymer shear degradation increases with molecular weight and salinity, but decreases with the presence of acrylate, ATBS, and nVP. All results can be interpreted in terms of chain flexibility. The highly flexible polyacrylamide homopolymer is the most sensitive to shear degradation. Introduction of acrylate groups in the polymer chain induces some stability because of the rigidity provided by charge repulsion, which vanishes in the presence of high salinity because of the screening of acrylate negative charges. ATBS and VP groups, which are larger in size, provide significant chain rigidity, and thus better shear stability. It is also shown that some very-high-molecular-weight polymers, after passing the shearing device, attain a final viscosity lower than lower-molecular-weight products with the same chemical composition. This factor has to be taken into account in the final choice of a polymer for a given field application. As a comparison, although less popular today than 2 decades ago, xanthan gum (XG), which behaves like a semirigid rod, is shown to be much less sensitive to the shear-degradation test than the coiled polyacrylamides (Sorbie 1991).

Acrylate‐Facilitated Cellular Uptake of Gold Nanoparticles

Uptake of PEGylated gold nanoparticles by HeLa cells in the presence of acrylate is described. Nanoparticles that are usually not taken up readily cross the plasma membrane into the cytosol in the presence of acrylate. In addition, a method is described that allows the introduction of large amounts of pre-aggregated gold nanoparticles into the cells without compromising the cell viability

ChemInform Abstract: Boron Trifluoride as a Promoter and Fluoride Donor in the Aldol Reaction of trans α,β-Epoxyaldehydes. Access to 5- and 6-Fluoro Heptulosonic Ester Analogues.

Abstract A direct synthesis of 5- and 6-fluoro heptulosonic esters is achieved by reaction of trans α,β-epoxyaldehydes with 2-(trimethylsilyloxy)acrylate in presence of BF 3 ·Et 2 O.

Unraveling Mechanistic Events in Solids-Stabilized Emulsion Polymerization by Monitoring the Concentration of Nanoparticles in the Water Phase

The fate of nanoparticles used as stabilizers in solids-stabilized, or Pickering, emulsion polymerization for the formation of armored hybrid polymer latexes was studied. We showed that disk centrifugation can be used as a powerful quantitative tool to analyze and determine the concentration of nanoparticles in the water phase throughout solids-stabilized emulsion polymerizations. We performed a series of emulsion polymerizations using vinyl acetate, vinyl pivalate, methyl methacrylate, or butyl acrylate in presence of silica nanoparticles (Ludox TM-40, ca. 25 nm in diameter). The developed method to quantify the number of silica nanoparticles in the water phase proved to be an invaluable tool for determining key features of the polymerization process. The obtained concentration profiles versus monomer conversion explained the existence of limited coalescence of armored particles in the later stages of the solids-stabilized emulsion polymerization process of vinyl acetate, leading to nonspherical structures. Moreover, we demonstrated that the correlation of the measured number of silica nanoparticles present in the water phase with the average particle sizes of the latex particles provided excellent predictions for the coverage of the armored layer of nanoparticles on the surfaces of the polymer particles, corresponding to observed packing patterns.

The Emulsion Polymerization of Each of Vinyl Acetate and Butyl Acrylate Monomers Using bis (2-ethylhexyl) Maleate for Improving the Physicomechanical Properties of Paints and Adhesive Films

Improving the water sensitivity of polyvinyl acetate PVAc films as well as pressure sensitivity, adhesion and washability of polybutyl acrylate were achieved by using bis (2-ethylhexyl) maleate (BEHM). The emulsion polymerization kinetics of vinyl acetate and butyl acrylate in presence of BEHM was studied. The order of the polymerization reaction with respect to the BEHM in presence of each of vinyl acetate and butyl acrylate was studied. The physicomechanical properties of the polyvinyl acetate films and vinyl acetate-butyl acrylate copolymer films were studied in presence of BEHM and the obtained results were matched with those prepared in the presence of pluronic F 108 and showed superior values. The obtained mean average molecular weights were found to be smaller in presence of BEHM assuring the presence of chain transfer reaction.

Synthesis and chemical transformations of 2-cyclopropyl-2-diazoacetates

Methyl 2-cyclopropyl-2-diazoacetate was synthesized from acetylcyclopropane in few chemical steps in ∼55% total yield. Its copper or rhodium-catalyzed dediazoniation exclusively proceeds through the intramolecular isomerization of generated cyclopropyl(methoxycarbonyl)carbene to 1-methoxycarbonylcyclobutene, irrespective of the presence or the absence of unsaturated compounds. However, in the presence of acrylates or strained cycloalkenes, this diazo ester is being slowly involved into the 1,3-dipolar cycloaddition, giving cyclopropyl-substituted pyrazolinecarboxylates, which in case of 1-pyrazolines easily lose nitrogen molecule to selectively afford 1-cyclopropylcyclopropanecarboxylate derivatives.