Reactivity Of Double Bond Research Articles

Precise Supramolecular Control of Selectivity in the Rh-Catalyzed Hydroformylation of Terminal and Internal Alkenes

In this study, we report a series of DIMPhos ligands L1-L3, bidentate phosphorus ligands equipped with an integral anion binding site (the DIM pocket). Coordination studies show that these ligands bind to a rhodium center in a bidentate fashion. Experiments under hydroformylation conditions confirm the formation of the mononuclear hydridobiscarbonyl rhodium complexes that are generally assumed to be active in hydroformylation. The metal complexes formed still strongly bind the anionic species in the binding site of the ligand, without affecting the metal coordination sphere. These bifunctional properties of DIMPhos are further demonstrated by the crystal structure of the rhodium complex with acetate anion bound in the binding site of the ligand. The catalytic studies demonstrate that substrate preorganization by binding in the DIM pocket of the ligand results in unprecedented selectivities in hydroformylation of terminal and internal alkenes functionalized with an anionic group. Remarkably, the selectivity controlling anionic group can be even 10 bonds away from the reactive double bond, demonstrating the potential of this supramolecular approach. Control experiments confirm the crucial role of the anion binding for the selectivity. DFT studies on the decisive intermediates reveal that the anion binding in the DIM pocket restricts the rotational freedom of the reactive double bound. As a consequence, the pathway to the undesired product is strongly hindered, whereas that for the desired product is lowered in energy. Detailed kinetic studies, together with the in situ spectroscopic measurements and isotope-labeling studies, support this mode of operation and reveal that these supramolecular systems follow enzymatic-type Michaelis-Menten kinetics, with competitive product inhibition.

Surface Enrichment by Conventional and Polymerizable Sulfated Nonylphenol Ethoxylate Emulsifiers in Water-Based Pressure-Sensitive Adhesive

Comparisons of properties are made for pressure-sensitive adhesives (PSAs) generated via emulsion polymerization using both conventional and reactive emulsifiers. The emulsifiers are ammonium salts of sulfated nonylphenol ethoxylates with similar chemical structures and hydrophilic–lipophilic balances. The polymerizable surfactant possesses a reactive double bond at its phenyl ring allowing for participation in free-radical polymerization reactions. Incorporation of the polymerizable surfactant into the adhesive polymer was confirmed via reverse-phase liquid chromatography. Surfactant distributions in PSA films were characterized using confocal Raman microscopy and contact angle measurements. Increasing conventional surfactant concentrations in emulsion polymerization reactions resulted in proportional increases in concentrations at the surfaces of latex-cast films. No surface enrichment of adhesive films was observed when reactive emulsifiers were employed. Variations in measured depth profiles and conta...

Linseed-oil-based waterborne UV/air dual-cured wood coatings

The synthesis of linseed oil (LO)-based waterborne polyurethane dispersion (PUD) wood coatings using different curing processes, as well as their coating and film properties, were examined. The waterborne prepolymer was synthesized first from modified linseed oil (MLO), dimethylol propionic acid (DMPA), isophorone diisocyanate (IPDI), hexamethylene diisocyanate (HDI) and hydroxyethyl methacrylate (HEMA) using an acetone process to prepare a solvent-borne prepolymer with CC bonds derived from methacrylic acid and fatty acids. The prepolymer was subsequently neutralized with triethylamine (TEA) and dispersed in water. After removing acetone, PUD was obtained. The results showed that the PUD could be readily synthesized and that it possessed reactive double bonds derived from HEMA and LO. Wood coatings were formulated by mixing PUD with photoinitiator for UV curing alone or by mixing PUD with metal dryers for air drying alone or by combining PUD with the two formulations as UV/air and air/UV dual-cured systems. The waterborne wood coatings were cured through different curing processes, as previously mentioned, and the properties of the cured films were characterized. The results showed that the durability and the lightfastness of films prepared using the UV/air dual-curing process (i.e., first UV-cured, followed by air drying) were better than those of the coatings cured using UV alone. Furthermore, the poor adhesion of the films cured using UV alone was significantly improved through the use of the UV/air dual-curing system. In conclusion, the linseed-oil-based waterborne UV/air dual-cured coatings possess the potential to provide high-efficiency, high-performance and environmentally friendly coatings for furniture finishing and it is a candidate for the application of coatings in the wood industry.

Bioplastic Nanocomposite Prepared from Acrylated Epoxidized Soybean Oil-PMMA Copolymer and Nano-Titanium Dioxide

Acrylated epoxidized soybean oil (AESO) with different degree of acrylation (50-70 mol%) were produced by acrylation reaction between epoxidized soybean oil (ESO) and acrylic acid. These AESOs were copolymerized with methyl methacrylate (MMA) monomer by free radical polymerization to produce bio-based copolymers (AESO-co-PMMA). Effect of degree of acrylation on tensile properties and thermal properties of the copolymers were investigated. The tensile strength increased with increasing degree of acrylation whereas the elongation at break decreased. The glass transition temperature (Tg) was determined by using dynamic mechanical thermal analysis. Higher degree of acrylation provided higher Tg and crosslink density because of higher reactive double bonds arising from acrylate group. Bioplastic nanocomposite was prepared from AESO-co-PMMA blended with 0.1-0.2 wt% nano-titanium dioxide, the commercial grade, dispersed in ethyl acetate. Its particle size was 2-5 nm. TiO2 increased the tensile strength and decreased the elongation at break of the copolymer. The addition of TiO2 did not significantly affect on Tg and thermal stability of the copolymer. (Resume d'auteur)

From CO2‐Based Multifunctional Polycarbonates With a Controlled Number of Functional Groups to Graft Polymers

AbstractCopolymerization of CO2 and epoxides is employed to generate functional polycarbonates. The introduction of reactive double bonds at a poly(propylene carbonate) (PPC) backbone is realized by the copolymerization of aliphatic alkene epoxides with propylene oxide (PO) and carbon dioxide (CO2). A series of copolymers with random structure and varying comonomer content (3–22%) with molecular weights in the range of 22 000–34 000 g mol−1 is synthesized and characterized with respect to their microstructure and thermal properties. The facile transformation of the double bonds is verified by a thiol‐ene reaction, resulting in quantitative conversion of the double bonds. Polycarbonate derivatives with multiple functionalities are prepared, providing suitable moieties for further grafting.magnified image

Thermal and Mechanical Property Research of Polyethylene Modified by Reactive Quatemary Ammonium Salt

In this investigation, dodecyl dimethyl(vinylbenzyl)ammonium chloride is applied to modify properties of polyethylene, and it is greatly focused on influences of it on the thermal properties and mechanical properties of this polymer. The results demonstrate that addition of this compound into polyethylene has little effect on thermal properties except for little improvement of its glass temperature, although it has reactive double bond in its molecular. Moreover, it is observed that it can enhance mechanical properties of this polymer and its addition has little change in colors of bulk materials. Therefore, it is believed that these excellent properties help to drive this antibacterial compound in applications.

Enzyme-Mediated Ring-Opening Polymerization of Pentadecalactone to Obtain Biodegradable Polymer for Fabrication of Scaffolds for Bone Tissue Engineering

The optimization of enzyme-mediated polymerization of pentadecalactone (PDL) was performed to obtain macromolecular products suitable for generation of 3D cell supports (scaffolds) for bone tissue engineering. Such parameters as temperature, monomer/enzyme ratio, and monomer concentration were studied. The maximum molecular weight of synthesized polymers was about 90,000. Methods allowing the introduction of reactive double bonds into polypentadecalactone (polyPDL) structure were developed. The macroporous matrices were obtained by modification of thermoinduced phase separation method.

Synthesis, characterization and properties of novel linear poly(butylene fumarate) bearing reactive double bonds

Poly(butylene fumarate) (PBF) bearing reactive double bonds on the polymer main chains has been designed and synthesized by coupling with hexamethylene diisocyanate (HDI) under very mild condition. The chemical structure, conformational structure, crystal structure and molecular weight of PBF were systematically characterized by ATR-FTIR, 1H NMR, 13C NMR, GPC and WARD. The thermal properties, mechanical properties and biodegradability of PBF were carefully studied by DSC, mechanical testing and enzymatic degradation. The results of 1H NMR and 13C NMR spectra indicate that no isomerization or Ordelt saturation reaction of trans CC took place during the bulk polymerization and the reaction just proceeded in the way we designed. Linear PBF with high-molecular-weight has been successfully synthesized. This new type of uncrosslinked polyester is shown to have many merits such as relatively high melting point (Tm), satisfactory processability and good mechanical properties. The impact strength of PBF is higher than 200 J/m; tensile and flexural strength can reach to 41.0 and 26.7 MPa, respectively.

Some trends observed in [60]fullerene polymerization activated by butyllithium isomers

It was found that BuLi plays a dual role in the polymerization of [60]fullerene: the addition of a first molecule of BuLi makes C60 tending to polymerize, while the addition of more BuLi molecules to the other reactive double bonds impedes this process.

3‐P⩵O‐Functionalized Phospholane 1‐Oxides by the Michael Reaction of 1‐Phenyl‐2‐phospholene 1‐Oxide and Dialkyl Phosphites, H‐Phosphinates, or Diphenylphosphine Oxide

ABSTRACTThe addition of dialkyl phosphites, H‐phosphinates, and diphenylphosphine oxide on the β carbon atom of the not too reactive double bond of 1‐phenyl‐2‐phospholene 1‐oxide was carried out in two ways. According to the first approach (A), the P‐reagents were activated by trimethylaluminum prior to the Michael addition. The second method (B) involved the microwave(MW)‐assisted solventless reaction of the P‐species with the phospholene oxide. In general, method A was more efficient and more selective than route B. However, the addition of dialkyl phosphites and diphenylphosphine oxide could also be accomplished well under MW conditions. The disadvantage of the MW‐assisted approach is that the Michael adducts are formed as a mixture of isomers. The 3‐P⩵O‐phospholane oxides are novel products, and among these, the bis(phosphine oxide) is the precursor of the bidentate P‐ligand LuPhos.

Novel Unsaturated Aliphatic Polyesters: Synthesis, Characterization, and Properties of Multiblock Copolymers Composing of Poly(Butylene Fumarate) and Poly(1,2-Propylene Succinate)

Widespread application of biodegradable polyesters is restrained by various disadvantages such as inadequate thermomechanical properties, high cost, and lack of reactive sites for further modification. Poly(butylene fumarate) (PBF), as a novel and low-cost aliphatic polyester, possesses good physical properties and reactive double bonds along with the polymer backbones which can be potentially modified to endow the polyester with specific properties. However, the biodegradation rate of PBF is too slow to meet the requirement of practical application. In this contribution, amorphous poly(1,2-propylene succinate) (PPS) was copolymerized with PBF to decrease the crystallinity (Xc) and accelerate the biodegradability of PBF via chain-extension with diisocyanate. The chemical structures of the copolymers were confirmed by 1H NMR spectra and gel permeation chromatography (GPC). The crystal structure and physicochemical properties were investigated by wide-angle X-ray diffraction (WAXD), differential scanning ca...

Biosynthesis and characterization of polyhydroxyalkanoates by Pseudomonas guezennei from alkanoates and glucose

The biosynthesis of medium chain length poly(3-hydroxyalkanoates) mcl PHAs by Pseudomonas guezennei using glucose, sodium octanoate, and 10-undecenoic acid as sole or mixed carbon sources was investigated. Chemical composition of polyesters was analyzed by GCMS and NMR. The copolyester produced by P. guezennei from glucose mainly consisted of 3-hydroxyoctanoate and 3-hydroxydecanoate, and the presence of 3-hydroxydodec-5-enoate was demonstrated. Using sodium octanoate as the sole nutrient, the microorganism produced a poly(3-hydroxyoctanoate) (PHO) polymer containing up to 94mol% 3-hydroxyoctanoate. Biosynthesis of poly[(3-hydroxyoctanoate)-co-(3-hydroxyundecenoate)] (PHOU) copolymers bearing terminal reactive double bonds on its side chains with unsaturation degree ranging from 8.8% to 78.2% was obtained by tuning the ratio of sodium octanoate/10-undecenoic acid in the medium. Thermal analysis indicated semi-crystalline polymers with melting temperatures (Tm) ranging from 46 to 55°C, fusion enthalpy (ΔH) comprised between 3 and 35J/g and glass transition temperature (Tg) from −36 to −44°C, except for the highly amorphous 78.2% unsaturated PHOU with a low Tg (−50°C). Molecular weights determined by GPC ranged from 119000 and 530000g/mol.The biosynthesis of natural polyesters with controlled ratio of vinyl-terminated side chains is of great interest for further chemical modifications.

Enantio- and Regioselective Epoxidation of Olefinic Double Bonds in Quinolones, Pyridones, and Amides Catalyzed by a Ruthenium Porphyrin Catalyst with a Hydrogen Bonding Site

An array of differently substituted 3-alkenylquinolones was synthesized, and the enantio- and regioselectivity of their Ru-catalyzed epoxidation were studied. A precursor ruthenium(II) complex with a chiral tricyclic γ-lactam skeleton (octahydro-1H-4,7-methanoisoindol-1-one) was available by Sonogashira cross-coupling with a monobromo-substituted ruthenium(II) porphyrin. Enantioselective epoxidation reactions (60-83% yield, 85-98% ee) were achieved with this catalyst, and it was shown that the enantioselectivity depends critically on the presence of a two-point hydrogen bond interaction between the γ-lactam site of the catalyst and the δ-lactam (quinolone) site of the substrate. DFT calculations support the hypothesis that the reaction occurs via a hydrogen-bound transition state, in which the 3-alkenylquinolone adopts an s-trans conformation. The calculations further revealed that this transition state is preferred over a competing s-cis transition state because it exerts less strain in the rigid backbone and because the hydrogen bond interaction is more stable. The catalyst loading required for complete conversion was low (<0.2 mol %), and turnover numbers exceeding 4000 were recorded. It was shown that there is little, if any, inhibition of the catalytic process by other quinolones, which could potentially compete with the binding site. A mechanistic model for the catalytic reaction is presented. In accordance with this model 3-alkenylpyridones reacted with similar enantioselectivities as the respective quinolones. The epoxidation products were unstable, however, and the enantiomeric purity (77-87% ee) of the products could be established only after derivatization. Primary alkenoic acid amides also underwent the epoxidation but gave the respective products in lower enantioselectivities (70% and 45% ee), presumably because the enantioface differentiation is hampered by the increased flexibility of the substrates, which exhibit two or three rotatable single bonds between the binding site and the reactive olefinic double bond.

Investigation of termination reactions in free radical photopolymerization of UV powder formulations

The termination mechanisms occurring in a UV powder coating system during photopolymerization process are investigated and compared to a conventional acrylate monomer system. The influence of the photoinitiator concentration, viscosity and conversion percentage of the monomer are assessed leading to the study of curing kinetics of a UV powder urethane diacrylate based system. It is shown that termination occurs mainly by bimolecular termination (PRT). This mechanism is related to low reactive double bonds concentration and high photoinitiator concentration in the UV powder system. Moreover, the effect of surrounding atmosphere points out the role of the oxygen on polymerization mechanisms.

Modification of oligo-Ricinoleic Acid and Its Derivatives with 10-Undecenoic Acid via Lipase-Catalyzed Esterification

Lipases were employed under solvent-free conditions to conjugate oligo-ricinoleic acid derivatives with 10-undecenoic acid, to incorporate a reactive terminal double bond into the resultant product. First, undecenoic acid was covalently attached to oligo-ricinoleic acid using immobilized Candida antarctica lipase (CAL) at a 30% yield. Thirty percent conversion also occurred for CAL-catalyzed esterification between undecenoic acid and biocatalytically-prepared polyglycerol polyricinoleate (PGPR), with attachment of undecenoic acid occurring primarily at free hydroxyls of the polyglycerol moiety. The synthesis of oligo-ricinoleyl-, undecenoyl- structured triacylglycerols comprised two steps. The first step, the 1,3-selective lipase-catalyzed interesterification of castor oil with undecenoic acid, occurred successfully. The second step, the CAL-catalyzed reaction between ricinoleyl-, undecenoyl structured TAG and ricinoleic acid, yielded approximately 10% of the desired structured triacylglycerols (TAG); however, a significant portion of the ricinoleic acid underwent self-polymerization as a side-reaction. The employment of gel permeation chromatography, normal phase HPLC, NMR, and acid value measurements was effective for characterizing the reaction pathways and products that formed.

Thermo- and pH-sensitive IPN hydrogels based on PNIPAAm and PVA-Ma networks with LCST tailored close to human body temperature

Interpenetrating polymer network (IPN) hydrogels based on chemically modified poly(vinyl alcohol) (or PVA-Ma), with different degrees of substitution (DS), and poly(N-isopropylacrylamide) (or PNIPAAm) were obtained and characterized in this work. The PVA-Ma/PNIPAAm membrane hydrogels were prepared in two steps. In the first step the PVA-Ma hydrogels (with using PVA-Ma with different DS) were prepared by the reaction of double bonds on PVA-Ma, using the persulfate/TEMED pathway. In the second step the PNIPAAm network was prepared within the parent PVA-Ma network at different PVA-Ma/NIPAAm ratios using a photoreaction pathway. The studies show that degree of swelling of PVA-Ma/PNIPAAm IPN hydrogels is dependent on both temperature and pH of the soaking solution. The LCST of PVA-Ma/PNIPAAm IPN hydrogels, which was determined by measuring the intensity of light transmitted through the swollen hydrogels, can be tailored closer to human body temperature. Furthermore, SEM images showed that the IPN hydrogels present characteristic morphology as compared to parent PVA-Ma networks. IPN hydrogels presented lower cytotoxicity as compared to respective PVA-Ma hydrogels but the increase in the PVA-Ma/NIPAAm ratio allows the respective hydrogels being lesser cytocompatibles. The IPN hydrogels synthesized in this work presented characteristics that potentize their application as biomaterials, drug carriers, artificial muscles and treatment of wound.

IPN hydrogels based on PNIPAAm and PVA-Ma networks: characterization through measure of LCST, swelling ratio and mechanical properties

IPN hydrogels based on chemically modified poly(vinyl alcohol) (or PVA-Ma), with different degrees of substitution (DS), and poly(N-isopropylacrylamide) (or PNIPAAm) were obtained and characterized through measures of LCST, swelling ratio and mechanical properties. Linear PVA-Ma with several DS were obtained through the chemical reaction of PVA with glycidyl methacrylate (GMA). The DS of various PVA-Ma were determined through 1H NMR spectroscopy. Two steps were used for preparation the PVA-Ma/PNIPAAm membrane hydrogels. In the first step the PVA-Ma hydrogels (using PVA-Ma with different DS) were prepared by reaction of double bonds on PVA-Ma, using the persulfate/TEMED system. Using a photoreaction pathway in the second step, PNIPAAm network was prepared within the parent PVA-Ma network at different PVA-Ma/NIPAAm ratios. The studies show that degree of swelling ratio (SR) of PVA-Ma/PNIPAAm IPN hydrogels is dependent of temperature. The LCST for each IPN-hydrogel was determined by measuring the intensity of light transmitted through the hydrogel. The LCST of the IPN hydrogels ranged from 34.6 to 38.1oC. The elastic modules of swollen IPN hydrogels increased from 25 to 35oC but decreased by further warming to 45oC. The LCST, swelling ratio and mechanical properties of PVA-Ma/PNIPAAm IPN hydrogels can be tailored by tuning the PVA-Ma/NIPAAm ratio.

Investigating the UV-curing performance for polyacrylated polymer in dendritic and regular conformation

In this study, PDSC was employed to monitor the UV curing process for dendritic and regular monomers with various acrylate sites. Experimental results reveal that even with only a small increase in molecular weight for regular monomers caused a large increase in viscosity. A dendritic monomer with the same number of sites has a much lower viscosity. The conversion of hydroxyl groups into acrylic groups in the dendritic monomer slightly reduces the viscosity by destroying the hydrogen bonds. The curing conversion and curing rate increased with the number of acrylate sites to maxima at five. The acceleration of the double bond reaction within a dense group of multiacrylate sites is responsible for the initial rise, but the steric effect of the branches, hindering the simultaneous free-radical propagation, causes a decline as the number of sites increases in the curing of dendrimers. The autocatalyzed reaction model was then applied to simulate the curing results from PDSC. Dendrimers with 10–19 acrylate sites were found to have lower rate constant k and smaller autocatalyzed order m than the traditional ones. Finally, the heterogeneity of the cross-linking density of dendrimers generally causes dendritic monomers to have weaker hardness and lower Td values than the regular ones. Nevertheless, dendrimers with 19 acrylate sites yield a film having low processing viscosity, satisfactory hardness (6H), reasonable Td (290 °C), and a superior refractive index (1.5).

Magnetic solid‐phase extraction using magnetic hypercrosslinked polymer for rapid determination of illegal drugs in urine

A novel magnetic material Fe(3)O(4)/SiO(2)/P(MAA-co-VBC-co-DVB) was prepared via the hypercrosslinking of its precursor which was produced via precipitation polymerization of methacrylic acid (MAA), vinylbenzyl chloride (VBC), and divinylbenzene (DVB) in the presence of Fe(3)O(4)/SiO(2) submicrospheres with the surface containing abundant reactive double bonds. The resultant sorbent was characterized by scan electron microscopy, N(2) adsorption, and Fourier transform infrared spectroscopy. It was found that this material had remarkable features such as large surface area (500 m(2)/g) and pore volume (0.32 cm(3)/g), as well as desirable chemical composition (including hydrophobic and ion-exchange moieties). Taking advantages of the Fe(3)O(4)/SiO(2)/P(MAA-co-VBC-co-DVB), a magnetic SPE (MSPE) coupled with capillary electrophoresis (CE) method was developed for the determination of illegal drugs in urine samples. The extraction time could be clearly shortened up to 3 min. The recoveries of these drug compounds were in the range of 84.0-123% with relative standard deviations ranging between 1.7 and 10.5%; the limit of detection was in the range of 4.0-6.0 μg/L. The proposed method is simple, effective, and low-cost, and provides an accurate and sensitive detection platform for abused drug analysis.

Effects of ozone on gene expression and lipid peroxidation in adults and larvae of the red flour beetle ( Tribolium castaneum)

Ozone has in recent years been increasingly investigated for its potential use in the control of insect pests of stored cereals. Ozone is a powerful oxidizing agent that can react directly, or via production of reactive oxygen species, with proteins, DNA and double bonds of polyunsaturated fatty acids (PUFA). The aim of the present study was to investigate the mode of action in ozone toxicity using the red flour beetle, Tribolium castaneum (Herbst), as a relevant model. Transcription of focal genes thought to be involved in protection against ozone, and repair of cellular damage caused by ozone exposure, was studied together with the composition of storage lipid fatty acids and membrane phospholipid fatty acids in order to detect lipid peroxidation. Contrary to expectations, transcription of focal genes ( Cu/Zn-Superoxide Dismutase, Catalase, Glutathione Peroxidase, Glutathione S-Transferase, Δ-9 Desaturase 1, Δ-12 Desaturase, DNA Ligase IV, Heat Shock Proteins 60, 70, 83) was either decreased or unchanged in larvae and adults exposed to 40 ppm ozone for 6 or 24 h, respectively, as compared to parallel control samples. No, or only little, peroxidation of lipid fractions occurred during exposure to 40 ppm ozone, although it was demonstrated that this concentration is sufficient to kill both larvae and adults of the red flour beetle. Possible explanations for these observations may be that the time-scale of the experimentation was such that any up-regulatory change may have been missed, or that ozone had caused a general depression of metabolism (including transcription of reactive oxygen species detoxifying genes) as the insects had been oxygen-deprived due to longer than normal closure of the spiracles.