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Ketone functionalization is a cornerstone of organic synthesis. Herein, we describe the development of an intermolecular C-H alkenylation of enamides with the feedstock chemical vinyl acetate to access diverse functionalized ketones. Enamides derived from various cyclic and acyclic ketones reacted efficiently, and a number of sensitive functional groups were tolerated. In this iridium-catalyzed transformation, two structurally and electronically similar alkenes-enamide and vinyl acetate-underwent selective cross-coupling through C-H activation. No reaction partner was used in large excess. The reaction is also pH- and redox-neutral with HOAc as the only stoichiometric by-product. Detailed experimental and computational studies revealed a reaction mechanism involving 1,2-Ir-C migratory insertion followed by syn-β-acetoxy elimination, which is different from that of previous vinyl acetate mediated C-H activation reactions. Finally, the alkenylation product can serve as a versatile intermediate to deliver a variety of structurally modified ketones.

RAFT polymerization of N‐vinylimidazole followed pseudo‐first‐order kinetics. Morpholine‐based chain transfer agents for rapid polymerization of vinyl acetate afforded high‐molar‐mass poly(vinyl acetate) (up to 130 kg mol−1).

International audience; Switchable polymerization affords a unique opportunity to regulate polymer sequence and structure in a one-pot process from mixtures of monomers. Here we report a strategy that uses O2 as an external stimulus to switch the polymerization mechanism from the organometallic mediated radical polymerization (OMRP) of vinyl monomers mediated by (Salen)Co III-R [Salen=N,N'-bis(3,5-di-tertbutylsalicylidene)-1,2-cyclohexanediamine; R = alkyl] to the ringopening copolymerization (ROCOP) of CO2/epoxides. A critical issue is the unprecedented mono oxygen insertion into the Co-C bond, as demonstrated by experimental results and rationalized by DFT calculations, leading to the formation of (Salen)Co III-OR as an active species to initiate ROCOP. Diblock poly(vinyl acetate)-bpolycarbonate could be obtained from ROCOP of CO2/epoxides with preactivation of (Salen)Co end-capped poly(vinyl acetate). Furthermore, a poly(vinyl acetate)-b-poly(methyl acrylate)-bpolycarbonate triblock copolymer has been successfully synthesized via a (Salen)cobalt-mediated sequential polymerization with an O2triggered switch in a one-pot process.

A pseudo-comprehensive two-dimensional liquid chromatography approach with size exclusion chromatography in the first dimension and gradient reversed-phase liquid chromatography in the second dimension was successfully developed for the characterization of vinyl acetate/acrylic acid copolymers and vinyl acetate/itaconic acid/acrylic acid terpolymers. Active solvent modulation was exploited to prevent the polymer breakthrough in the second dimension separation caused by the strong solvent used in the first dimension. The conditions of the active solvent modulation valve were optimized to achieve sufficient on-line dilution and to completely prevent polymer breakthrough without adding excessive time to the modulation cycle. Using this approach, copolymers made with different monomer ratios and processes were studied. Heterogeneous composition distribution due to insufficient monomer incorporation was detected in some of the copolymer samples. We demonstrated that with active solvent modulation, the two-dimensional liquid chromatography approach is no longer limited to water-soluble polymers and can be used for a broader range of polymers and copolymers.

Inspired by polyvalency and its prevalence in nature, we developed an efficient synthetic route for accessing a large variety of multivalent and dual-cavity baskets from inexpensive and abundant starting materials. First, the cycloaddition of vinyl acetate to anthracene was optimized to, upon hydrolysis, give dibenzobarrelene derivative 6, which after five functional group transformations and then cyclotrimerization gave heptiptycene dodecaester 4 in an overall 17 % yield. Following that, compound 4 was converted into D3h symmetric 1, composed of two fused cavitands each holding three terminal alkynes at the rim for conjugation to functional molecules using the highly efficient CuAAC reaction. To survey the reactivity of hexavalent 1, we "clicked" 2-acetamido-2-deoxy-β-d-glucopyranosyl azide 3,4,6-triacetate (carbohydrate), methoxypolyethylene glycol azide (PEG, Mn =2000; polymer) and benzyl azide (aromatic) to obtain hexavalent conjugates 12-14 in 50-79 % yields. In summary, dual-cavity 1 is an accessible, structurally-unique and hexavalent host that can be "clicked" to a variety of functional molecules for (a) combinatorial lead identification of drugs, (b) preparation of hierarchical soft materials and (c) design of selective chemosensors, scavengers, or supramolecular catalysts.

Robots are typically controlled by electrical signals. Resistive heating is an option to electrically trigger actuation in thermosensitive polymer systems. In this study electrically triggerable poly[ethylene‐co‐(vinyl acetate)] (PEVA)‐based fiber actuators are realized as composite fibers as well as polymer fibers with conductive coatings. In the coated fibers, the core consists of crosslinked PEVA (cPEVA), while the conductive coating shell is achieved via a dip coating procedure with a coating thickness between 10 and 140µm. The conductivity of coated fibers σ= 300–550 S m−1is much higher than that of the composite fibers σ= 5.5 S m−1. A voltage (U) of 110V is required to heat 30cm of coated fiber to a targeted temperature of ≈65 °C for switching in less than a minute. Cyclic electrical actuation investigations reveal ε′rev= 5 ± 1%reversible change in length for coated fibers. The fabrication of such electro‐conductive polymeric actuators is suitable for upscaling so that their application potential as artificial muscles can be explored in future studies.

In the present paper, we describe several pathways employing immobilized lipase from Candida antarctica B (CAL-B) as biocatalyst to prepare easily both enantiomers of 3-(1-hydroxyethyl)phenol. We have applied hydrolysis with Na2 CO3 in organic media under mild conditions. The reaction parameters solvent effect, amount of lipase, and Na2 CO3 were examined with 3-(1-acetoxyethyl)phenyl acetate as substrate. In alkaline hydrolysis, (R)-3-(1-hydroxyethyl)phenol was obtained with ee = 99% and (S)-(-)-3-(1-acetoxyethyl)phenol with ee = 98% at optimal conversion (c = 50%) and high selectivity (E > 200). Two other deacylation reactions were compared: alcoholysis with MeOH and with NEt3 . The acylation of 3-(1-hydroxyethyl)phenol with vinyl acetate was also examined. Alkaline hydrolysis gave the best results, while good regioselectivity and enantioselectivity were observed in alcoholysis and acylation reactions. Finally, (S)- and (R)-3-(1-hydroxyethyl)phenol (ee > 98%), key intermediates for the synthesis of important drugs, were prepared from the corresponding racemic diacetate through alkaline hydrolysis.

Author(s): Higa, Chad Masaharu | Advisor(s): Braslau, Rebecca | Abstract: Poly(vinyl chloride) (PVC) is one of the most utilized thermoplastics on Earth. However, PVC by itself is brittle and not readily processable. This material reached the success of its worldwide demand because of phthalates, a cost-effective additive (emollient) that imparts flexibility and resistivity towards weathering, temperature extremes and electrical conductivity. The use of phthalates as plastic emollients is widespread, representing approximately three quarters of all plasticizers globally, with applications ranging from industrial to consumer products. The pervasive utilization of low molecular weight blended phthalates as emollients inevitably leads to leaching, contamination and exposure. Phthalates and their metabolites have displayed negative effects on various organs and act as potent endocrine disrupting chemicals that cause deleterious pre- and postnatal developmental effects, notably in males. Bans of phthalates by the European Union and the United States in children’s articles have spurred the development of less toxic PVC plasticizer alternatives.Branched and linear non-migratory internal plasticizers attached to PVC by a pendant triazole linkage were synthesized. Copper-free azide-alkyne thermal cycloaddition was employed to covalently bind triazole-based phthalate mimics to poly(vinyl chloride) (PVC). To systematically investigate the effect of plasticizer structure on glass transition temperature, several architectural motifs were explored. Free volume theory was considered when designing many of these internal plasticizers: hexyl-tethers were utilized to generate additional space between the triazole-phthalate mimic and the polymer backbone. Miscibility of these triazole-plasticizers in PVC is important: variation of the ester moieties on the triazole possessing alkyl and/or poly(ethylene oxide) (PEO) chains produced a wide range of glass transition temperatures (Tg): from anti-plasticizing 96 °C, to highly efficient plasticized materials exhibiting Tg values as low as -42 °C.Triazole methyl esters directly appended to PVC displays an inherent anti-plasticization effect originating from the aromatic ring, which diminishes with increasing molecular weight and branching of the alkyl ester chains. Introduction of a flexible hexyl tether to the secondary triazole group acts as additional molecular weight and branching, further lowering Tg values. Attachment of two hexyl tethered secondary triazoles follows this trend by enforcing another branch point and increasing molecular weight. Utilization of PEO esters in all architectural types significantly enhances Tg depressions, with longer PEO chains exhibiting remarkable results. Single PEO triazole esters readily prepared from propiolic esters using low-cost, commercially available materials combine excellent plasticization with straightforward synthesis, making these non-migratory internal plasticizers extremely attractive for industrial applications.An alternative strategy to post-polymerization direct modification of PVC to obtain internally plasticized materials involves the copolymerization of vinyl chloride monomer (VCM) with a monomer functionalized with a triazole-phthalate mimic. Electron-rich vinyl acetate monomers with an appended triazole-plasticizer were synthesized for this purpose. Copolymerizations with the vinyl acetate triazole monomers and VCM were largely unsuccessful. It was envisaged that an acrylate derivative should remedy the low reactivity of these vinyl acetate monomers. An acrylate incorporating a hexyl-tethered triazole-phthalate mimic served two purposes: 1) generate space between the triazole and polymerizing vinyl group to prevent monomer deactivation and, 2) enhance the plasticization efficiency of the triazole.

para‐Hydrogen‐induced polarization (PHIP) is a method to rapidly generate hyperpolarized compounds, enhancing the signal of nuclear magnetic resonance (NMR) experiments by several thousand‐fold. The hyperpolarization of metabolites and their use as contrast agents in vivo is an emerging diagnostic technique. High degrees of polarization and extended polarization lifetime are necessary requirements for the detection of metabolites in vivo. Here, we present pulsed NMR methods for obtaining hyperpolarized magnetization in two metabolites. We demonstrate that the hydrogenation with para‐hydrogen of perdeuterated vinyl acetate allows us to create hyperpolarized ethyl acetate with close to 60 % 1H two‐spin order. With nearly 100 % efficiency, this order can either be transferred to 1H in‐phase magnetization or 13C magnetization of the carbonyl function. Close to 60 % polarization is experimentally verified for both nuclei. Cleavage of the ethyl acetate precursor in a 20 s reaction yields ethanol with approximately 27 % 1H polarization and acetate with around 20 % 13C polarization. This development will open new opportunities to generate metabolic contrast agents in less than one minute.

A new, concise, and efficient route towards both antipodes of N-(β-hydroxypropyl)indoles is described. The key step is an enantioselective lipase-mediated acetylation of racemic indolic alcohols [1-(1H-indol-1-yl)propan-2-ol, 1-(2-methyl-1H-indol-1-yl)propan-2-ol, and 1-(5-bromo-1H-indol-1-yl)propan-2-ol] with enol esters (vinyl acetate and isopropenyl acetate) as acyl group donors, performed under kinetically controlled conditions. A substantial influence of enzyme type, acyl group donor, and organic solvent on conversion rates and enantioselectivity of the enzymatic kinetic resolutions (EKRs) of the respective racemates was examined in detail. The best results in terms of enantioselectivity were obtained for the resolutions performed with native lipase from Pseudomonas fluorescens (PFL, Amano AK) in diisopropyl ether (DIPE) or tert-butyl methyl ether (TBME) solution. To support the assignment of the absolute configurations of EKR products, chemical correlations with enantiomerically enriched analytical standards and single-crystal X-ray diffraction analysis were applied.

The Friedel–Crafts acylation is a broadly applied reaction that can be conducted using various types of catalyst. However, a biocatalytic alternative has only been reported recently. In this study, the scope of acetyl donors is described, showing that, in addition to vinyl acetate derivatives, phenyl esters are also suitable donors. Furthermore, it was found that various amines enhance the reaction, whereby the effect do not seem to be correlated to the pH but to the structure of the donor. For instance, 1,4-diazabicyclo[2.2.2]octane (DABCO) turned out to be a viable alternative to imidazole; however the former performed best at pH 9.85, whereas the latter performed best at pH 8.3.

This work studies the ultraviolet (UV) protection properties of poly(lactic acid) (PLA) nanocomposites. A functional property of UV protection was achieved by adding the active component [zinc oxide (ZnO) modified with poly(vinyl acetate) (PVAc)] to the PLA matrix. PLA nanocomposites were prepared by solution casting technique. PLA nanocomposites were characterized by scanning electron microscopy, mechanical properties tests, and UV-Vis spectroscopy. The results showed that UV-blocking property of PLA nanocomposites were improved in relation to a pure PLA. Samples where nanoparticles were homogeneously dispersed in the PLA matrix showed good mechanical properties. The results also showed that adding the active component ZnO modified with PVAc contributes to the improved UV protection property of nanocomposite materials. J. VINYL ADDIT. TECHNOL., 2017. © 2017 Society of Plastics Engineers

Homogeneous multiwalled carbon nanotube/montmorillonite hybrid filler (HMM) dispersion was prepared by co-ultrasonication and was subsequently used to prepare ethylene-co-vinyl acetate (EVA) nanocomposites by solution blending method. XRD and TEM analysis of HMM confirm significant interaction between the montmorillonite (MMT) layers and multiwalled carbon nanotubes (MWCNT) in line with previous reports. Analysis of the nanocomposites shows the constituent fillers to be homogeneously dispersed in EVA matrix. Mechanical properties of neat EVA are remarkably improved with HMM content up to 3 wt% followed by reversion. Maximum improvement observed in tensile strength, elongation at break, and toughness are 424%, 109%, and 1122%, respectively. Results show maximum thermal stability at 4 wt% and best dielectric response at 1 wt% HMM content. Exceptional mechanical and dielectric properties of EVA nanocomposites attained may be attributed to homogeneous dispersion of fillers and improved polymer–filler interaction. Comparison shows excellent synergy between MWCNT and MMT towards mechanical reinforcement of EVA. POLYM. ENG. SCI., 2017. © 2017 Society of Plastics Engineers

In a conventional semi-batch seeded emulsion copolymerization of vinyl acetate/butyl acrylate (VA/BA) using hybrid surfactants namely, dioctyl sulfosuccinate (DOSS) as an anionic surfactant, nonylphenol ethoxylate (KENON 30) as a non-ionic type, and polydimethylsiloxane surfactant (having hydrophilic silanol-terminated, called PDMS). The effect of PDMS on the properties of the latex synthesized was investigated by measuring solid content, viscosity, colloidal stability, particle size distributions of the base latex, viscosity average molecular weight ( $$ \bar{M}_{\text{v}} $$ ) of the copolymer, latex particle morphology, glass transition temperature (T g) of a copolymer and thermal gravimetric analysis (TGA). Particle size of the base latex decreases (Z-average from 246.48 to 143.69 nm) upon increasing the amount of PDMS surfactant in the recipe (up to 6 wt%). The presence of PDMS surfactant in the hybrid surfactants led to a significant increase in the solid content (from 48.71 to 51.31 wt%), viscosity (from 334 to 806 centipoise, cp) and $$ \bar{M}_{\text{v}} $$ (from 1.91 × 105 to 2.34 × 105 g mol−1). Thermal stability and T g of the copolymer were increased with addition of PDMS surfactant (thermal stability from 344.77 to 389.81 °C and T g from −20.7 to 21.7 °C). The colloidal stability evaluated using the electrolyte addition method was improved with addition of PDMS surfactant. The uniform morphological structure of the final particle is the main effect of using PDMS in the hybrid surfactants.

EVA copolymer foils are widely used as encapsulants for photovoltaic (PV) cells in PV modules. These foils need to be crosslinked during module manufacturing, to enhance their properties. Accurate and reliable methods for the determination of their crosslinking degree are thus very important. In this work, two semi-empirical calorimetric methods are considered and compared to a scientifically sound rheological method used as a reference. The main purpose of this work is to reveal the chemical and physical fundamentals on which the two calorimetric methods are based, to allow for a scientific understanding of their advantages, and limitations. For one of these calorimetric methods, the so-called “Melt-Freeze” method, we have sought for a deeper understanding of the underlying crystallization physics through the use of successive selfnucleation and annealing experiments, which give access to the crystallite size distribution of EVA, and to the influence of crosslinking upon it.

The Hansen solubility parameters (HSPs) of two ethylene–vinyl acetate (EVA) copolymers (with 18 and 33 wt% of vinyl acetate) and their corresponding homopolymers (polyethylene, PE, and poly(vinyl acetate), PVAc) have been studied at various temperatures, employing the previously obtained Flory–Huggins parameters. From these latter values, a procedure based on the Hansen solubility spheres theory was employed to determine the HSPs, as well as the radius of interaction. The procedure was validated with literature data, with deviations of around 3%. The HSP values (dispersion, polar and association terms, respectively, all in MPa1/2) at 333.15 K are 14.84, −3.88 and 1.78 for PE, 17.65, −1.24 and 2.76 for EVA410 (with 18 wt% of vinyl acetate), 17.52, 0.15 and 3.61 for EVA460 (with 33 wt% of vinyl acetate) and 19.45, 10.59 and 5.76 for PVAc. The main characteristic of the obtained HSP values is that the high polar term of PVAc tends to increase the solubility character of the pure PE, and thus the EVA copolymers, allowing them to solubilize dispersion and polar compounds. Finally, it was also demonstrated that it is possible to predict the HSPs of EVA copolymers using the vinyl acetate content and the HSPs of pure PE and PVAc as input data. © 2017 Society of Chemical Industry

Two five-membered cyclic nitrones derived from hexoses, a newly synthesized D-allo-configured nitrone and an already known D-talo-configured nitrone, have been examined in 1,3-dipolar cycloaddition reactions with vinyl acetate, allyl benzoate, methyl acrylate, acrylonitrile, and vinylene carbonate. The reactions of the D-allo-configured nitrone proceeded preferentially through the expected exo-anti transition state, but all the cycloadditions of the D-talo-configured nitrone surprisingly showed high exo-syn selectivity. This reversal of stereoselectivity has been explained by 3D analysis of the preferred conformations of the nitrones, obtained from X-ray data. The structures were further inspected using CONFLEX, PM5, and DFT calculations. All these methods revealed that the dioxolane substituents attached to C-5 of both nitrones had opposite spatial locations.

Residual dipolar couplings (RDCs) are a rich source of structural information that goes beyond the range covered by the nuclear Overhauser effect or scalar coupling constants. They can only be measured in partially oriented samples. RDC studies of peptides in organic solvents have so far been focused on samples in chloroform or DMSO. Here, we show that stretched poly(vinyl acetate) can be used for the partial alignment of a linear β-peptide with proteinogenic side chains in methanol. 1 DCH , 1 DNH , and 2 DHH RDCs were collected with this sample and included as restraints in a simulated annealing calculation. Incorporation of RDCs in the structure calculation process improves the long-range definition in the backbone of the resulting 314 -helix and uncovers side-chain mobility. Experimental side-chain RDCs of the central leucine and valine residues are in good agreement with predicted values from a local three-state model. Copyright © 2016 John Wiley & Sons, Ltd.

NiCoAl layered double hydroxide (NiCoAl LDH) and multiwalled carbon nanotubes (CNTs) were successfully self-assembled to generate a three-dimensional CNTs-NiCoAl LDH hybrid by means of a urea-hydrolysis method. The scanning electron microscopy observations revealed that the hybrid was composed of both “core/shell” and flower-like nanostructure. Composites of poly(ethylenes-co-vinyl acetate) (EVA) with CNTs-NiCoAl LDH were prepared by melt blending. Their flammability performance and smoke toxicity were evaluated. CNTs-NiCoAl LDH was found to be an efficient additive to improve the flame retardancy of EVA and reduce the smoke toxicity by suppressing the emission of carbon monoxide (CO). The physical properties of the char were believed to be critical in improving the flame retardancy. The remarkable reduction in smoke toxicity of EVA upon CNTs-NiCoAl LDH was probably attributed to the combined effects of adsorption and catalysis on the oxidation of CO. POLYM. COMPOS., 2017. © 2017 Society of Plastics Engineers

Optically pure 2-chloromandelic acid (ClMA) is a very important chiral drug intermediate for synthesis of (S)-clopidogrel, belonging to the platelet aggregation inhibitor. Enantioselective resolution of (R,S)-2-chloromandelic acid was carried out in organic solvent through irreversible transesterification catalyzed by lipase AK with vinyl acetate acting as the acyl donor. Effects of various conditions on enantioselectivity and activity of lipase were investigated, including organic solvents, temperature, water content, substrate ratio, enzyme loading, and reaction time. Based on homogeneous reaction and Ping-Pong bi-bi mechanism, a quantitative model was constructed to simulate and optimize the reaction process. Under the optimal conditions, excellent results were obtained with high conversion of (R)-2-ClMA (c R , ≥98.85%) and large enantiomeric excess of substrate (ee s , ≥98.15%). There is a good agreement between predicted values and experiment data, which indicates that the established method is a powerful tool for optimization of the enantioselective transesterification process for enantiomers separation.

Supported metal catalyst was designed, characterized and tested for aqueous phase heterogeneous hydrogenation of vinyl acetate with parahydrogen to produce 13C-hyperpolarized ethyl acetate for potential biomedical applications. The Rh/TiO2 catalyst with 23.2 wt% loading produced strong hyperpolarized 13C-enriched ethyl acetate-1-13C detected at 9.4 T. Approximately 14-fold 13C signal enhancement was detected using ~50% parahydrogen gas without taking into account relaxation losses before and after polarization transfer via magnetic field cycling from nascent parahydrogen-derived protons to 13C nuclei. This first observation of 13C PHIP-hyperpolarized products over supported metal catalyst in the aqueous medium opens up new possibilities for production of catalyst-free aqueous solutions of nontoxic hyperpolarized contrast agents for a wide range of biomolecules amenable to Parahydrogen Induced Polarization via Side Arm Hydrogenation (PHIP-SAH) approach.

This study describes a simple, rapid, and cost-effective fabrication of PDMS electrophoresis microchips using poly(vinyl acetate) (PVAc) emulsion as photoresist master. High-relief microfluidic structures were defined on poly(vinyl acetate) previously deposited on printed circuit boards surfaces without cleanroom facilities and sophisticated instrumentation. After a UV exposure, channels with heights ranging from 30 to 140 μm were obtained by controlling the emulsion mass deposited on the master surface. The developing stage was performed using water rather than the organic solvents that are applied for conventional masks. The surface morphology was characterized by optical imaging, profilometry, and SEM. Based on the achieved results, the proposed method offers suitable reproducibility for the prototyping of electrophoresis microchips in PDMS. The feasibility of the resulting PDMS electrophoresis chips was successfully demonstrated with the separation of major inorganic cations within 100 s using a contactless conductivity detection system. The separation efficiencies ranged from ca. 67 900 to 125 600 plates/m. Due to the satisfactory performance and simplified instrumentation, we believe this fabrication protocol presents potential to be implemented in any chemical, biochemical, or biological laboratory.

A new redox initiation system, potassium persulfate/N,N-dimethylethanolamine, was used to initiate traditional radical emulsion polymerization of vinyl acetate at low temperature. Polymers were characterized using gel permeation chromatography, scanning electron microscopy and dynamic light scattering. The results showed that poly(vinyl acetate) with high molar mass and small dispersity (Đ) was successfully synthesized. © 2016 Society of Chemical Industry

We report the influence of adding five short-chain glycol ethers (SCGEs) on the structure, stability, and viscoelastic properties of aqueous dispersions of partially hydrolyzed poly(vinyl acetate) and borax. The properties of these gel-like materials have been investigated as a function of the structure of the added SCGE both below and above the critical aggregation (or micellar) concentrations using (11) B and (13) C NMR, rheology, and small-angle neutron scattering. The results indicate that the SCGE aggregation behavior is not affected by incorporation into the gel-like network. However, changes in the viscoelasticity and structural properties of the dispersions were detected that can be correlated to the nature of the solvent system. Also, the ability of these materials to clean an unvarnished acrylic paint surface coated with synthetic soil has been evaluated using colorimetery, and the surface of the dispersion after cleaning was visualized with scanning electron microscopy.