Preparation of waterborne polyurethane adhesives based on macromolecular-diols containing different diisocyanate

<p>Three different macromolecular diols were synthesized by the reaction of Poly(1,4-butanediol adipate) diol (PBA) and diisocyanate (Isophorone diisocyanate (IPDI), Hexamethylene diisocyanate (HDI) and Methylene-bis(4-cyclohexylisocyanate)(HMDI)) at the ratio of 2:1. Based on these macromolecular diols, waterborne polyurethane (WPU) adhesives were prepared. The structure and molecular weights of the WPU were characterized by Nuclear magnetic resonance spectroscopy (¹H NMR), Fourier Transform Infrared Spectroscopy (FTIR) and Gel permeation chromatography (GPC) respectively. Furthermore, the hydrogen bonding interaction of WPU were analyzed by the deconvolution FTIR spectra. The results showed that the hydrogen bonded NH was increased when carbamate was in the soft segment. The crystallinity of WPU was tested by X-ray diffraction (XRD) and Differential scanning calorimetry (DSC). The results showed that the crystallinity of WPU2 (HDI) and WPU3 (HMDI) were enhanced, especially for WPU2. Meanwhile, the Tg,s as well as the mechanical strength, storage modulus, the contact angle and thermo-stability were increased with the introduced carbamate into soft segment. The T-peel tests of plasticized PVC/WPU/plasticized PVC joints and lap-shear tests of wood/WPU adhesive/wood joints were carried out. The results indicated that the carbamate in the soft segment could significantly enhance the adhesion of WPU at an appropriate activation temperature.</p

Molecular-Level Understanding of Solvation Structures and Vibrational Spectra of an Ethylammonium Nitrate Ionic Liquid around Single-Walled Carbon Nanotubes

Molecular dynamics simulations have been performed to explore the solvation structures and vibrational spectra of an ethylammonium nitrate (EAN) ionic liquid (IL) around various single-walled carbon nanotubes (SWNTs). Our simulation results demonstrate that both cations and anions show a cylindrical double-shell solvation structure around the SWNTs regardless of the nanotube diameter. In the first solvation shell, the CH₃ groups of cations are found to be closer to the SWNT surface than the NH₃⁺ groups because of the solvophobic nature of the CH₃ groups, while the NO₃^– anions tend to lean on the nanotube surface, with three O atoms facing the bulk EAN. On the other hand, the intensities of both C–H (the CH₃ group of the cation) and N–O (anion) asymmetric stretching bands at the EAN/SWNT interface are found to be slightly higher than the corresponding bulk values owing to the accumulation and orientation of cations and anions in the first solvation shell. More interestingly, the N–O stretching band exhibits a red shift of around 10 cm^–1 with respect to the bulk value, which is quite contrary to the blue shift of the O–H stretching band of water molecules at the hydrophobic interfaces. Such a red shift of the N–O stretching mode can be attributed to the enhanced hydrogen bonds (HBs) of the NO₃^– anions in the first solvation shell. Our simulation results provide a molecular-level understanding of the interfacial vibrational spectra of an EAN IL on the SWNT surface and their connection with the relevant solvation structures and interfacial HBs

Lumenal Loop M672-P707 of the Menkes Protein (ATP7A) Transfers Copper to Peptidylglycine Monooxygenase

Copper transfer to cuproproteins located in vesicular compartments of the secretory pathway depends on activity of the copper-translocating ATPase (ATP7A), but the mechanism of transfer is largely unexplored. Copper-ATPase ATP7A is unique in having a sequence rich in histidine and methionine residues located on the lumenal side of the membrane. The corresponding fragment binds Cu­(I) when expressed as a chimera with a scaffold protein, and mutations or deletions of His and/or Met residues in its sequence inhibit dephosphorylation of the ATPase, a catalytic step associated with copper release. Here we present evidence for a potential role of this lumenal region of ATP7A in copper transfer to cuproenzymes. Both Cu­(II) and Cu­(I) forms were investigated since the form in which copper is transferred to acceptor proteins is currently unknown. Analysis of Cu­(II) using EPR demonstrated that at Cu:P ratios below 1:1 ¹⁵N-substituted protein had Cu­(II) bound by 4 His residues, but this coordination changed as the Cu­(II) to protein ratio increased toward 2:1. XAS confirmed this coordination via analysis of the intensity of outer-shell scattering from imidazole residues. The Cu­(II) complexes could be reduced to their Cu­(I) counterparts by ascorbate, but here again, as shown by EXAFS and XANES spectroscopy, the coordination was dependent on copper loading. At low copper Cu­(I) was bound by a mixed ligand set of His + Met, whereas at higher ratios His coordination predominated. The copper-loaded loop was able to transfer either Cu­(II) or Cu­(I) to peptidylglycine monooxygenase in the presence of chelating resin, generating catalytically active enzyme in a process that appeared to involve direct interaction between the two partners. The variation of coordination with copper loading suggests copper-dependent conformational change which in turn could act as a signal for regulating copper release by the ATPase pump

Concentration-Dependent Hydrogen Bond Behavior of Ethylammonium Nitrate Protic Ionic Liquid–Water Mixtures Explored by Molecular Dynamics Simulations

The detailed hydrogen bond (HB) behavior of ethylammonium nitrate (EAN) ionic liquid (IL)–water mixtures with different water concentrations has been investigated at a molecular level by using classical molecular dynamics simulations. The simulation results demonstrate that the increasing water concentration can weaken considerably all cation–anion, cation–water, anion–water, and water–water HBs in EAN–water mixtures, and the corresponding HB networks around cations, anions, and water molecules also change significantly with the addition of water. Meanwhile, both the translational and the rotational motions of anions, cations, and water molecules are found to be much faster as the water concentration increases. On the other hand, the order of their HB strength is found to be cation–anion > anion–water > cation–water > water–water at low water mole fractions (<38%), while the corresponding order is cation–anion > cation–water > anion–water > water–water at high water mole fractions (>38%). The opposite orders of anion–water and cation–water HBs at low and high water concentrations, as well as the different changes of HB networks around cations and anions, should be responsible for the increasing deviation in diffusion coefficient between cations and anions with the water concentration, which is favorable to the cation–anion dissociation. In addition, the competing effect between ionic mobility and ionic concentration leads to that the ionic conductivity of EAN–water mixtures initially increases with the water mole fraction and follows a sharp decrease beyond 90%. Our simulation results provide a molecular-level concentration-dependent HB networks and dynamics, as well as their relationship with unique structures and dynamics in protic IL–water mixtures

Molecular-Level Insights into Size-Dependent Stabilization Mechanism of Gold Nanoparticles in 1‑Butyl-3-methylimidazolium Tetrafluoroborate Ionic Liquid

Here we report a series of classical molecular dynamics simulations for the icosahedral Au nanoparticles with four different diameters of 1.0, 1.4, 1.8, and 2.3 nm in 1-butyl-3-methylimidazolium tetrafluoroborate ([bmim]­[BF₄]) room-temperature ionic liquid (RTIL). Our simulation results reveal for the first time a size-dependent stabilization mechanism of the Au nanoparticles in the [bmim]­[BF₄] RTIL, which may help to clarify the relevant debate on the stabilization mechanism from various experimental observations. By comparison, the alkyl chains in the [bmim]⁺ cations are found to dominate the stabilization of the smallest Au₁₃ nanoparticle in the RTIL while the imidazolium rings should be mainly responsible for the stabilization of other larger nanoparticles in the RTIL. Compared to the [bmim]⁺ cations, the [BF₄]⁻ anions are found to have an indirect influence on stabilizing the Au nanoparticles in the RTIL because of the weak interaction between the Au nanoparticles and the anions. However, such differences in the stabilization mechanism between the small and the large Au nanoparticles can be attributed to the unique hydrogen bond (HB) network between the cations and the anions in the first solvation shell. Meanwhile, increasing the particle size can lead to the enhanced HBs on the surface of Au nanoparticles, so slower rotational motions and more pronounced orientation distribution of cations can be observed around the larger nanoparticles. Our simulation results in this work provide a molecular-level understanding of the unique size-dependent stabilization mechanism of the Au nanoparticles in the imidazolium-based RTILs

Structural Properties and Vibrational Spectra of Ethylammonium Nitrate Ionic Liquid Confined in Single-Walled Carbon Nanotubes

The structures and relevant vibrational spectra of an ethylammonium nitrate (EAN) ionic liquid (IL) confined in single-walled carbon nanotubes (SWCNTs) with various diameters have been investigated in detail by using classical molecular dynamics simulation. Our simulation results demonstrate that the EAN IL confined in larger SWCNTs can form well-defined multishell structures with an additional cation chain located at the center. However, a different single-shell hollow structure has been found for both the cations and the anions in the 1 nm SWCNT. For the cations confined in SWCNTs, the CH₃ groups stay closer to the nanotube walls because of their solvophobic nature, while the NH₃⁺ groups prefer to point toward the central axis. Accordingly, the NO₃^– anions tend to lean on the SWCNT surface with three O atoms facing the central axis to form hydrogen bonds (HBs) with the NH₃⁺ groups. In addition, in the 1 nm SWCNT, the CH₃ groups of cations exhibit an obvious blue shift of around 16 cm^–1 for the C–H stretching mode with respect to the bulk value, and the N–H stretching mode of NH₃⁺ groups is split into two characteristic peaks with one peak appearing at a higher frequency. Such a blue shift is attributed to the existence of more free space for the C–H bonds of confined CH₃ groups, while the splitting phenomenon is due to the fact that more than 60% of the confined NH₃⁺ groups have one dangling N–H bond. For the anions confined in the 1 nm SWCNT, the N–O stretching mode of NO₃^– has a maximum red shift of around 24 cm^–1 with respect to the bulk value, which is attributed to enhanced HBs between anions and cations. Our simulation results reveal a molecular-level correlation between confined structural configurations and the corresponding vibrational spectra changes for the ILs confined in nanometer scale environments

Preparation of Porous Polysulfone Microspheres and Their Application in Removal of Oil from Water

The monodisperse porous polysulfone (PSF) microspheres with hollow core/porous shell structure were prepared by a water-in-oil-in-water (W/O/W) emulsion solvent evaporation method. The morphology of PSF is investigated by using three different surfactants such as oleic acid, polyvinylpyrrolidone and polyoxyethylen(20)-sorbitanmonooleat. The prepared microspheres are developed as sorbents to remove oil from water due to their highly hydrophobic and superoleophilic properties. The PSF microspheres synthesized in the presence of oleic acid exhibit the best separation efficiency, which is 44.8 times higher than that of the pristine PSF powder. The microspheres with appropriate size, unsinkable properties, and excellent reproducibility can be quickly distributed and collected in seconds on the surface of water. The pore structure of PSF microspheres and interaction between oil and PSF are proposed to explain the high efficiency

Preparation of Porous Polysulfone Microspheres and Their Application in Removal of Oil from Water

The monodisperse porous polysulfone (PSF) microspheres with hollow core/porous shell structure were prepared by a water-in-oil-in-water (W/O/W) emulsion solvent evaporation method. The morphology of PSF is investigated by using three different surfactants such as oleic acid, polyvinylpyrrolidone and polyoxyethylen(20)-sorbitanmonooleat. The prepared microspheres are developed as sorbents to remove oil from water due to their highly hydrophobic and superoleophilic properties. The PSF microspheres synthesized in the presence of oleic acid exhibit the best separation efficiency, which is 44.8 times higher than that of the pristine PSF powder. The microspheres with appropriate size, unsinkable properties, and excellent reproducibility can be quickly distributed and collected in seconds on the surface of water. The pore structure of PSF microspheres and interaction between oil and PSF are proposed to explain the high efficiency

Preparation of Porous Polysulfone Microspheres and Their Application in Removal of Oil from Water

The monodisperse porous polysulfone (PSF) microspheres with hollow core/porous shell structure were prepared by a water-in-oil-in-water (W/O/W) emulsion solvent evaporation method. The morphology of PSF is investigated by using three different surfactants such as oleic acid, polyvinylpyrrolidone and polyoxyethylen(20)-sorbitanmonooleat. The prepared microspheres are developed as sorbents to remove oil from water due to their highly hydrophobic and superoleophilic properties. The PSF microspheres synthesized in the presence of oleic acid exhibit the best separation efficiency, which is 44.8 times higher than that of the pristine PSF powder. The microspheres with appropriate size, unsinkable properties, and excellent reproducibility can be quickly distributed and collected in seconds on the surface of water. The pore structure of PSF microspheres and interaction between oil and PSF are proposed to explain the high efficiency

Preparation of Porous Polysulfone Microspheres and Their Application in Removal of Oil from Water

The monodisperse porous polysulfone (PSF) microspheres with hollow core/porous shell structure were prepared by a water-in-oil-in-water (W/O/W) emulsion solvent evaporation method. The morphology of PSF is investigated by using three different surfactants such as oleic acid, polyvinylpyrrolidone and polyoxyethylen(20)-sorbitanmonooleat. The prepared microspheres are developed as sorbents to remove oil from water due to their highly hydrophobic and superoleophilic properties. The PSF microspheres synthesized in the presence of oleic acid exhibit the best separation efficiency, which is 44.8 times higher than that of the pristine PSF powder. The microspheres with appropriate size, unsinkable properties, and excellent reproducibility can be quickly distributed and collected in seconds on the surface of water. The pore structure of PSF microspheres and interaction between oil and PSF are proposed to explain the high efficiency