Showing papers on "Vinyl acetate published in 2018"
TL;DR: Efforts to probe and developCopolymerizations of polar vinyl monomers with ethylene using more functional group-tolerant late metal catalysts potentially offer an attractive alternative for generating value-added copolymers since ligand variations may provide more control of polymer microstructures and milder reaction conditions would apply.
Abstract: ConspectusThe most ubiquitous polymer, polyethylene (PE), is produced either through a radical-initiated process or, more commonly, through a coordination/insertion process employing early transition metal catalysts, particularly titanium- and chromium-based systems. These oxophilic early metal catalysts are not functional-group-tolerant and thus cannot be used to synthesize copolymers of ethylene and polar vinyl monomers such as alkyl acrylates and vinyl acetate. Such PE copolymers have enhanced properties relative to PE and are made through radical polymerization processes, requiring exceptionally high pressures and temperatures. Copolymerizations of polar vinyl monomers with ethylene using more functional group-tolerant late metal catalysts potentially offer an attractive alternative for generating such value-added copolymers since ligand variations may provide more control of polymer microstructures and milder reaction conditions would apply. This Account describes our efforts, particularly through de...
250 citations
TL;DR: In this paper, the reversible shape memory polymer (RSMP) by semicrystalline poly(ethylene-co-vinyl acetate) with dynamic covalent polymer networks was reported.
Abstract: This work reports the reversible shape memory polymer (RSMP) by semicrystalline poly(ethylene-co-vinyl acetate) (PEVA) with dynamic covalent polymer networks. The ester linkages in the cross-linked PEVA acted as dynamic covalent bonds in the presence of a transesterification catalyst. This dynamic covalent network imparted the material with good thermal plasticity in a non-flow state at high temperature. The resulting PEVA possessed both the reversible shape memory effect (RSME) and thermadapt property. The thermadapt performance gave little adverse effect on the RSME. This work provides an approach to improve the reprocessability/recyclability of thermoset RSMPs through simple modification of commercially available polymers.
67 citations
TL;DR: In this article, mixed matrix membranes (MMMs) fabricated from incorporating ZIF-8 nanocrystals into the polyvinyl acetate (PVAc) matrix exhibit significant improvement of propylene/propane permeability and selectivity as well as the operating stability.
57 citations
TL;DR: It is demonstrated 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, which will open new opportunities to generate metabolic contrast agents in less than one minute.
Abstract: 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.
56 citations
TL;DR: The results showed that the properties of wood adhesive could improve dramatically by using two co-monomers VAc and BA during the graft copolymerization reaction.
36 citations
TL;DR: In this article, a novel strategy to prepare polymer composites reinforced with cellulose nanocrystals (CNCs) via pickering emulsion polymerization was reported, and the most promising latexes were then shaped by extrusion molding.
30 citations
TL;DR: In this article, a series of nano-hybrid pour-point depressants (PPDs) which combined nano-montmorillonite (MMT) and ethylene vinyl acetate (EVA) copolymers were prepared.
29 citations
TL;DR: In this paper, a series of copolymers were synthesized with CO2-philic monomer 3, 3,4, 4,5, 5,6, 6,7, 7, 8,8, 9,10, 10, 10 10,10 10-Heptadecafluorodecyl acrylate (HFDA) and CO2phobic monomer vinyl n-Octanoate (VOc), Vinyl acetate (VAc), vinyl pivalate (VPi), respectively.
Abstract: Molecular modeling of CO2-polymer system was established to study the molecular behaviors and intermolecular interaction of copolymers in supercritical carbon dioxide (SC-CO2) by all-atom molecular dynamics (MD) simulation. According to the simulation results, the correlations of the intermolecular interaction with the molecular structure and composition were explored. The effects of intermolecular interactions on the copolymer properties in SC-CO2 were identified. A series of copolymers were synthesized with CO2-philic monomer 3,3,4,4,5,5,6,6,7,7,8,8,9,9,10,10,10-Heptadecafluorodecyl acrylate (HFDA) and CO2-phobic monomer vinyl n-Octanoate (VOc), vinyl acetate (VAc), vinyl pivalate (VPi), respectively. The solubility and viscosification of the copolymers in SC-CO2 were evaluated by cloud point pressure and relative viscosity measurements. It was found that P(HFDA0.49-co-VAc0.51), which is the most effective thickener among the copolymers, could enhance the viscosity of SC-CO2 by 62 times at 5 wt%. It was suggested that the thickening capability of the copolymers in SC-CO2 may originate from intermolecular cross-links generated by associative groups. Combining the molecular simulation and experiment results, the structure-activity relationships of the copolymers in SC-CO2 were revealed. It is believed that the molecular simulation aided design method for the SC-CO2 copolymer thickener is reliable.
25 citations
TL;DR: In this paper, pure silica nanoparticles (SNPs) have been successfully obtained by thermal treatment of rice husk through a sol-gel surfactant free technique, and different concentrations of SNPs were embedded within the polyvinyl chloride-co-vinyl acetate-co 2-hydroxypropyl acrylate (PVVH) copolymer matrix via a solvent casting method.
Abstract: Pure silica nanoparticles (SNPs) have been successfully obtained by thermal treatment of rice husk through a sol-gel surfactant free technique. Different concentrations of SNPs were embedded within the poly(vinyl chloride-co-vinyl acetate-co-2-hydroxypropyl acrylate) (PVVH) copolymer matrix via a solvent casting method. X-ray diffraction analysis (XRD) confirmed the amorphous nature for PVVH combined with an increase in the amorphous regions after addition of SNPs. Fourier transform infrared (FTIR) and ultraviolet/visible (UV/Vis.) spectroscopy revealed the induced changes in chemical structure and optical parameters (i.e. optical energy gap Eg, refractive index n) for PVVH/SNPs composites. Scanning electron microscopy (SEM) was performed to study the surface morphology and homogeneity of the prepared samples.
22 citations
TL;DR: In this article, polyvinyl alcohol (PVA) was incorporated into poly(ethylene vinyl acetate) (EVA) through the simple solution compounding processing, and the results showed that the water-active SME of the blends was greatly dependent upon the blend compositions.
21 citations
TL;DR: In this article, the effect of polyvinyl chloride (PVC) internal plasticizers on glass transition temperature has been investigated in a variety of architectural motifs, including hexyl tethered secondary triazoles and polyethylene oxide (PEO) chains.
Abstract: 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.
TL;DR: The optimum wood bonding strength of the prepared P (VAc-BA) emulsion adhesive was even better than that of a commercial PVAc emulsion glue, suggesting its potential application for the wood industry.
Abstract: Polyvinyl acetate emulsion adhesive has been widely used due to its good bonding performance and environmentally friendly properties. Indeed, the bonding performance can be further improved by copolymerizing with other monomers. In this study, the effect of the adjunction of redox initiator (hydrogen peroxide-tartaric acid, H₂O₂-TA) on the properties of the poly (vinyl acetate-butyl acrylate) (P (VAc-BA)) emulsion adhesive was investigated. With increasing dosage, the reaction became more complete and the obtained film was more compact, as identified via SEM. The core-shell structure of the emulsion particles was confirmed via TEM. Results indicate that while the initiator content increased from 0.5 to 1.0%, a clearer core-shell structure was obtained and the bonding strength of the plywood improved from 2.34 to 2.97 MPa. With the further incorporation of H₂O₂-TA (i.e., 1.5%), the bonding performance deteriorated. The optimum wood bonding strength (2.97 MPa) of the prepared P (VAc-BA) emulsion adhesive was even better than that (2.55 MPa) of a commercial PVAc emulsion adhesive, suggesting its potential application for the wood industry.
TL;DR: In this article, the effect of polyvinylidene fluoride/polyvinyl acetate (PVDF/PVAc) ratio in the cathode binder of the LiMn2O4 (LMO) electrode on the electrochemical performance of a rechargeable hybrid aqueous battery was investigated.
TL;DR: In this paper, an acid/base switchable dithiocarbamate RAFT agent, cyanomethyl (4-fluorophenyl)(pyridin-4-yl) carbamodithioate, with the Lewis acid scandium triflate (Sc(OTf)3) was investigated to examine the ability to deliver improved control over RAFT copolymerizations involving both more-activated and less-activated monomers.
Abstract: Modulation of the activity of an acid/base switchable dithiocarbamate RAFT agent, cyanomethyl (4-fluorophenyl)(pyridin-4-yl)carbamodithioate, with the Lewis acid scandium triflate (Sc(OTf)3) was investigated to examine the ability to deliver improved control over RAFT copolymerizations involving both more-activated and less-activated monomers—specifically the copolymerization of methyl acrylate (MA) and vinyl acetate (VAc). The introduction of either 0.5 or 1 mol equiv of Sc(OTf)3, with respect to RAFT agent, into a RAFT copolymerization of MA and VAc provides substantially improved control resulting in significantly reduced molar mass dispersities (Đ) (∼1.1–1.3) than achieved in its absence (Đ ∼ 1.3–1.4). Furthermore, similar introduction of Sc(OTf)3 into MA homopolymerization mediated by the same RAFT agent also delivered polymers of very low Đ (∼1.15). Sc(OTf)3 was also found to lower the rate of polymerization and alter the copolymerization reactivity ratios for MA and VAc. Increasing the Lewis acid c...
TL;DR: In this paper, a titania nanofibers were produced from different precursor solutions by solution blow spinning and calcined at different annealing temperatures for evaluation of phase transitions.
TL;DR: In this article, a modified polyethylene terephthalate (r-PET) was used to investigate the molecular interaction of the modified films using Fourier transform infrared spectroscopy (FTIR), and the results indicated that modified PET films of better mechanical and thermal properties were successfully prepared using VAc monomer grafting by gamma irradiation technique.
Abstract: Vinyl acetate (VAc) monomer of different percentage was grafted onto the recycled polyethylene terephthalate (r-PET) films using gamma irradiation. The properties of these modified films were characterized by Fourier transform infrared spectroscopy (FTIR), mechanical properties testing (Tensile strength, Elongation at break), dynamic mechanical analysis (DMA) and thermo-gravimetric analysis (TGA). The Tensile Strength (TS) of the modified PET film increased by 132.25 % to the highest value of 50.12 MPa at 15% VAc monomer concentration at 3 kGy gamma dose, while the elongation at break (EB) decreased by 31.83 %. FTIR was used to investigate the molecular interaction of the modified films. TGA revealed that curve of the modified PET film shifted toward higher temperature region by 95 °C, which is very close to that of PET film made from virgin flakes. The results indicate that modified PET films of better mechanical and thermal properties were successfully prepared using VAc monomer grafting by gamma irradiation technique.
TL;DR: In this article, the authors used 1 mm thick melt-extruded films in CO2 at a range of pressures (100, 200, and 300 bar) and temperatures (30, 40, 50, and 60°C).
Abstract: Poly(ethylene-co-vinyl acetate) (EVA-25) and poly(ethylene-co-vinyl acetate-co-carbon monoxide) (EVACO-2410) and their blends with EVACO:EVA ratios of 80:20, 60:40, 40:60, and 20:80 were foamed using CO2. These foams are of interest for applications ranging from footwear to medical devices. Foaming experiments were carried out using 1 mm thick melt-extruded films in CO2 at a range of pressures (100, 200, and 300 bar) and temperatures (30, 40, 50, and 60 °C). Foamability of the polymers was explored both under isothermal and gradient temperature conditions. Foams of EVACO-2410 displayed high initial expansions followed by postfoaming relaxation and shrinkage while foams generated from EVA-25 showed more dimensional stability. Blending EVACO-2410 with EVA-25 was explored as an approach to reduce postfoaming relaxation and shrinkage. The surfaces of the foamed samples displayed blistering that was linked to CO2 bubble entrapment and coalescence at the surface. Scanning electron micrographs of the foams generated from blends displayed distinct morphologies reflecting whether the sections were representing the machine- or cross-machine direction of extruded films. In going from EVACO-2410 to EVA-25, the cell densities ranged from about 106 to 1010 cells/cm3. Foams with low bulk densities of about 0.11 g/cm3 could be generated. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018, 135, 45841.
TL;DR: In this paper, a novel fluoro-xanthate, 2-((4-fluorophenoxycarbonothioyl)thio)ethyl propanoate, was developed and successfully used as a mediator in the photoinduced controlled radical polymerization of more-activated monomers (methyl acrylate (MA), butyl acrylated, and N-isopropylacrylamide) and a less-activated (vinyl acetate (VAc)).
TL;DR: In this paper, the reaction of transesterification between geraniol and vinyl acetate for the enzymatic synthesis of geranyl acetate, using Novozym® 435 as catalyst, was assessed.
Abstract: The interest in new natural products used in cosmetic industry has increased the research in order to synthesize those compounds. The aim of this work is to assess the reaction of the transesterification between geraniol and vinyl acetate for the enzymatic synthesis of geranyl acetate, using Novozym® 435 as catalyst, as well as to obtain a kinetic model for the bioprocess and the values of the kinetic parameters. Five experimental series have been performed with variation of: enzyme amount, concentrations of geraniol and vinyl acetate in molar ratio 1:1, stirring rate, temperature and, finally, substrates molar ratio. A conversion of geranyl acetate of 98.4% has been obtained in the best experimental conditions and, also, high conversions were obtained for most of the other conditions assayed. It has been concluded that the catalyst amount is the most significant variable on the reaction kinetics and the reaction yield and that both the stirring rate and the initial substrates concentrations have no significant influence. Finally, a Ping–Pong bisubstrate kinetic model has been applied and its kinetic parameters have been determined by using an improved version of a procedure developed by authors in a previous work. The values obtained for the Michaelis constants show that, for the equal substrates concentrations series, the Ping–Pong model can be simplified to a pseudo-first order kinetic model, which has been confirmed, with high correlation coefficients, by using the “Curve Expert” software.
TL;DR: A polylactic acid tubular bended reactor, printed by fused deposition modeling with a short and narrow residence time distribution, air-cooled, and with dead volumes below 5vol% was integrated into a modular reaction system enabling product changes in the running system as discussed by the authors.
TL;DR: In this article, a polyvinyl acetate spray-on film containing mangosteen extract (MG/PVAc film) was used as a bioactive wound dressing.
TL;DR: In this article, a copper-catalyzed Huisgen dipolar cycloaddition ring closure reaction was applied to these difunctional precursors paving the way to unprecedented PVAc and/or EVA macrocycles, and to their PVOH- and EVOH-counterparts after hydrolysis.
TL;DR: In this paper, poly(maleic acid amide-co-vinyl acetate) copolymers with various aromatic (phenyl, naphthyl, and benzimidazole) pendants and/or aliphatic grafts were synthesized and found to be capable of dispersing asphaltenes effectively.
Abstract: Asphaltene precipitation often brings difficulties to the recovery and transportation of heavy crude oil. Poly(maleic acid amide-co-vinyl acetate) copolymers with various aromatic (phenyl, naphthyl, and benzimidazole) pendants and/or aliphatic (octyl, tetradecyl, and octadecyl) grafts were synthesized and found to be capable of dispersing asphaltenes effectively. To study the influence of aromatic and aliphatic pendants in copolymers on asphaltene precipitation behaviors, the initial precipitation point, turbidity, and size of asphaltene precipitates from model heavy oils in the presence and absence of copolymers were determined by UV–vis spectroscopy, turbidity meter, and dynamic light scattering, respectively. The effect of copolymers on the viscosity of Tahe heavy oil with high asphaltene content was investigated by the rheological approach. The results revealed that the copolymers with both aromatic and aliphatic pendants dispersed asphaltene, reduced its precipitates, and thus improved the flowabilit...
TL;DR: In this article, the formation mechanism of vinyl acetate in the reaction of acetylene and acetic acid, which was catalyzed by ordered mesoporous carbon supported zinc acetate, was investigated using density functional theory.
Abstract: The formation mechanism of vinyl acetate in the reaction of acetylene and acetic acid, which was catalyzed by ordered mesoporous carbon (OMC) supported zinc acetate, was investigated using density functional theory (DFT). Since the surface functional groups of carbon support influence the reaction significantly and play an important role in catalysis designing, we calculate the elementary steps on pristine ordered mesoporous carbon and carbon modified with carboxyl, carbonyl, and hydroxyl, respectively. After calculation, we find that carbonyl shifts to the epoxy group, which indicates the instability of carbonyl on the catalyst support. We propose the possible reaction mechanism and find that the reaction mechanism is not exactly the same with different functional groups. A remarkably acetate shift will occur in the existence of carboxyl and the activation barrier of rate-limiting steps in this case is also reduced, while the hydroxyl and epoxy groups will increase the barrier to some extent. Therefore, ...
TL;DR: In this paper, sequential polymerization of vinyl acetate and styrene monomer were carried out by reversible addition-fragmentation chain transfer (RAFT) and atom transfer radical polymerization (ATRP) using an innovative amide based difunctional chloroamide-xanthate iniferter.
TL;DR: In this article, the authors employed thermogravimetric analysis to explore the thermal stability of malonic acid (MA) dissolved in several polymer matrices that include poly(vinylpyrrolidone) (PVP), poly(methyl methacrylate) (PMMA), and polyvinyl acetate (PVAc), and found that PVP/MA system decomposes at markedly lower temperature than PMMA/MA and PVAc/MA systems.
Abstract: The present study employs thermogravimetric analysis to explore the thermal stability of malonic acid (MA) dissolved in several polymer matrices that include poly(vinylpyrrolidone) (PVP), poly(methyl methacrylate) (PMMA), and poly(vinyl acetate) (PVAc). It is found that PVP/MA system decomposes at markedly lower temperature than PMMA/MA and PVAc/MA systems. Isoconversional kinetic analysis indicates that the Arrhenius parameters for decomposition of PMMA/MA and PVAc/MA systems are virtually the same as for pure MA. For the PVP/MA system, the Arrhenius parameters differ significantly from the respective parameters for pure MA. The diminished thermal stability of PVP/MA system is linked to the rate constant being considerably larger than in all other systems under study. The effect is explained by a catalytic action of an amino group of PVP, which is similar to the known effect of catalysis of decarboxylation reactions by tertiary amines. The results obtained have important implications for the widespread u...
TL;DR: In this article, bimetallic zinc-nickel catalysts for acetylene acetoxylation were prepared with Zn(OAc)2·2H2O and Ni(O Ac) 2·4H 2O as precursors, and characterized by ICP-AES, BET, XPS, TEM, TPD-MS and TG.
TL;DR: A novel photoiniferter agent 4-(fluorosulfonyl)benzyl diethylcarbamodithioate (FSB-DECT) containing both dithiocarbamates and sulfonyl fluoride moieties is developed to act as both photoinitiator and click sulfur(VI)-fluoride exchange (SuFEx) agent for postpolymerization functionalization.
Abstract: “Click” type reactions represent the currently most prevalent postpolymerization strategy for the preparation of functional polymeric materials. Herein, a novel photoiniferter agent 4-(fluorosulfonyl)benzyl diethylcarbamodithioate (FSB-DECT) containing both dithiocarbamates and sulfonyl fluoride moieties is developed to act as both photoinitiator and click sulfur(VI)-fluoride exchange (SuFEx) agent. The photopolymerization behavior of FSB-DECT is demonstrated via standard photoiniferter-mediated polymerization for various types of monomer including N-isopropylacrylamide (NIPAAm), glycidyl methacrylate, and vinyl acetate (VAc). Gel permeation chromatography data show that the polymerization is relatively well controlled, with polydispersity indices of the product homopolymers in the range of 1.3–1.6. 1H and 19F NMR spectra and “reinitiated” photopolymerization indicate that the sulfonyl fluoride and diethyldithiocarbamyl groups remain at the respective ends of the homopolymer chains. Furthermore, using the sulfonyl fluoride end-functionalized poly(N-isopropylacrylamide) as a model polymer, the utility of the SuFEx reaction for efficient postpolymerization functionalization is demonstrated.
TL;DR: In this paper, the authors evaluate the effects of different materials on the performance of hybrid composites, where the aim is to establish compatibility among several materials, and evaluate the effect of the differences among them.
Abstract: Processing of hybrid composites represents a challenge for engineers where the aim is to establish compatibility among several materials. The aim of this study is to evaluate the effects of differe...
TL;DR: In this article, palladium and Cal B lipase were sequentially co-immobilized in the microenvironment of mesocellular foam to mimic biological systems and fully characterized.