Reformation Of Hydrogen Bonds Research Articles

Effect of jet cavitation on oil recovery from oily sludge

Jet cavitation method was proposed to treat oily sludge to improve oil recovery. The key components affecting the oil desorption efficiency were analyzed by TLC-FID (Thin-layer chromatography and flame ionization detection) method and FT-IR(Fourier-transform infrared spectroscopy), and the mechanism of oil recovery from oily sludge enhanced by jet cavitation was revealed. The results show that when the inlet pressure is 12 MPa, the temperature is 35 °C, the solid concentration is 25 %, and the hydraulic retention time for oily sludge is 4 s, the maximum oil recovery rate is 82.3 %, which is much higher than that after ultrasonic cavitation. After jet cavitation, the sedimentation performance of the oily sludge was improved, and the average particle size was reduced. Asphaltenes and resins are the main components affecting oil desorption. Heteroatoms such as N, S, and O form stable hydrogen bonds with the surface of solid particles, which impede the oil desorption process. The mechanical effect such as micro-jet shock waves and shear forces generated by jet cavitation could disrupt the hydrogen bonds, promoting the reformation of hydrogen bonds between water and solid particles, leading to the separation of oil from the surface of solid particles.

Hybrid aliphatic and aromatic diisocyanates forming mixed urea segments for high-performance polyurea

Polyurea is gaining more traction in the realm of protective coatings on metal surfaces from corrosion. The properties of polyurea can be controlled by the judicious selection of its reactants. Herein, a series of polyurea based on hybrid aliphatic/aromatic diisocyanates are synthesized from isophorone diisocyanate (IP) and polycarbodiimide-modified diphenylmethane diisocyanate (ISO). The formulation composed of 37.5:62.5 (IP: ISO) weight ratio yields the highest tensile strength at 47.80 MPa, elongation at 500 %, and hardness of 95 HA. The findings are validated through field emission scanning and atomic force microscopic analysis, which reveals phase mixing surface and ductile fracture containing wide-ranging stretching lines due to enhanced resistance to deformation. Furthermore, synthesized polyureas present a unique stress relaxation pattern with gradual increase in stress under constant deformation, due to hydrogen bond reformation and dislocation creations during chain alignment. IP37.5-ISO62.5 demonstrates outstanding corrosion resistance after a 28-day exposure in salt spray test.

Extraction of Collagen from Bovine Tannery Solid Waste Preserving Original Conformation via Radical Initiation and Hydrogen Bond Reformation

Extraction of Collagen from Bovine Tannery Solid Waste Preserving Original Conformation via Radical Initiation and Hydrogen Bond Reformation

Extraction of artemisinin using natural deep eutectic solvent selected by COSMO-RS

Natural deep eutectic solvent (NADES) has become an alternative and environmentally friendly solvent. This study designed new eutectic systems for the extraction of artemisinin from the leaves of Artemisia annua L. with the aid of conductor-like screening model for real solvents (COSMO-RS). The performance of the benzoic acid/fenchyl alcohol-based NADES was studied comprehensively under different extraction conditions, including hydrogen-bond donor (HBD)/hydrogen-bond acceptor (HBA) molar ratio, solid-liquid ratio, extraction temperature, and extraction time. It was found that artemisinin extraction should be performed using HBD/HBA 1:4 at 50 °C within 1.5 h. The extraction yield of the target could reach 11.08 mg/g. Artemisinin and the NADES were recovered from the final extract. Furthermore, the extraction mechanism was elucidated by the combination of 1H nuclear magnetic resonance (1H NMR) and scanning electron microscopy (SEM). The hydrogen bond reformation and the plant tissue destruction play vital roles during the extraction process. Therefore, the proposed NADES could serve as a green solvent to effectively extract natural bioactive compounds. The application of the NADESs proved their promise as designable solvents with stronger extraction capabilities than traditional organic solvents.

Deformation Mechanism of Amorphous Plasticized Poly(vinyl butyral)

Understanding the deformation mechanism of amorphous polymeric materials is indispensable for their applications but is quite challenging. Here, with amorphous plasticized poly(vinyl butyral) (PVB) as a model system, we studied its structural change in situ during uniaxial deformation with ultrasmall-angle X-ray scattering (USAXS). We observed a stretch-induced phase separation behavior characterized by a butterfly scattering pattern in plasticized PVB for the first time. This phase separation, featured by a concentration fluctuation along the stretch direction, is a result of stress–concentration coupling under stretch. The phase size at its formation is around 100 nm, which increases almost linearly with strain. The strain rate has a weak effect on the phase size. This suggests that the elastic deformation of the network, cross-linked by entanglements and hydrogen-bonding clusters, governs the phase size. We proposed a tentative model to explain the deformation behavior of plasticized PVB, where the breaking and reforming of hydrogen bonds, the formation and growth of phase separation against osmotic pressure, and the plastic deformation and rupture of phase structure dissipate a large amount of energy and endow the plasticized PVB with excellent mechanical performance. We believe our findings are general and should be applicable to other amorphous polymers with solvents or plasticizers.

Molecular Structure, Dynamics, and Vibrational Spectroscopy of the Acetylene:Ammonia (1:1) Plastic Co-Crystal at Titan Conditions

The Saturnian moon Titan has a thick, organic-rich atmosphere, and condensed phases of small organic molecules are anticipated to be stable on its surface. Of particular importance are crystalline phases of organics, known as cryominerals, which can play important roles in surface chemistry and geological processes on Titan. Many of these cryominerals could exhibit rich phase behavior, especially multicomponent cryominerals whose component molecules have multiple solid phases. One such cryomineral is the acetylene:ammonia (1:1) co-crystal, and here we use density functional theory-based ab initio molecular dynamics simulations to quantify its structure and dynamics at Titan conditions. We show that the acetylene:ammonia (1:1) co-crystal is a plastic co-crystal (or rotator phase) at Titan conditions because the ammonia molecules are orientationally disordered. Moreover, the ammonia molecules within this co-crystal rotate on picosecond time scales, and this rotation is accompanied by the breakage and reformation of hydrogen bonds between the ammonia hydrogens and the π-system of acetylene. The robustness of our predictions is supported by comparing the predictions of two density functional approximations at different levels of theory, as well as through the prediction of infrared and Raman spectra that agree well with experimental measurements. We anticipate that these results will aid in understanding geochemistry on the surface of Titan.

A multi-responsive self-healing and air-stable ionogel for a vertically integrated device comprised of flexible supercapacitor and strain sensor

We report on the synthesis of multi-responsive self-healing and air-stable ionogel for fabrication of integrated devices of supercapacitor and strain sensor. The ionogel is based on hydrophilic ionic liquid, 1-ethyl-3-methylimidazolium ethyl sulfate and poly(acrylic acid), crosslinked by N, N’-bis(acryloyl)cystamine-coated gold nanoparticles (AuNP@BACAs). The self-healing of the synthesized ionogel can be triggered by thermal heating or irradiation of near-infrared (NIR) laser light, via the reformation of hydrogen bonds and Au-thiolate interactions. Optically healing with NIR laser can be activated due to the introduction of AuNP@BACAs and the healing rate is faster than that by thermal heating. Using the synthesized ionogel electrolyte and multi-walled carbon nanotube electrodes, a high-performance flexible supercapacitor is fabricated with an areal capacitance of 20.4 mF cm−2, perfect capacitance recovery after repetitive self-healing cycles, and air stability over 30 days in ambient air conditions without encapsulation. Furthermore, the strain sensor fabricated using the same ionogel exhibits the self-healing performance of recovering the gauge factor of 0.85 regardless of the healing method. With the vertically integrated device consisting of flexible supercapacitor and strain sensor attached onto the skin, body-motions are successfully detected using the energy stored by the supercapacitor. These results suggest the high application potential of our fabricated electronic devices based on the single self-healable ionogel to wearable electronics with durability and longevity.

A confined carbon dot-based self-calibrated fluorescence probe for visible and highly sensitive moisture readouts

Excellent luminescent materials are essential for high-performance fluorescent nanosensors. Here, a new-type of self-calibrated humidity sensor is established through monitoring the fluorescent color change of carbon dots (CDs) confined in sodium hydroxide (CDs@NaOH). The CDs are prepared by a facile and rapid microwave-assisted heating method using citric acid, urea, and NaOH as precursors. The confinement effect from the NaOH reduces the nonradiative transition and suppresses the aggregation-induced quenching of the CDs in the solid. Compared with other sensors based on CD fluorescent visualization, the sensor has good linearity and a wide humidity-detection range from 6.9% to 95.4%. With the increased relative humidity, the fluorescence color of the sensor changes from green to blue. The proposed sensing mechanism is due to the breaking and reforming of hydrogen bonds and proton transfer occurring at the CD-NaOH matrix interfaces. These findings suggest a potential role for the spatial confinement effect and may provide an avenue for developing highly sensitive humidity readouts.

Self-Healing Hydrophilic Porous Photothermal Membranes for Durable and Highly Efficient Solar-Driven Interfacial Water Evaporation

Self-Healing Hydrophilic Porous Photothermal Membranes for Durable and Highly Efficient Solar-Driven Interfacial Water Evaporation

An exact a posteriori correction for hydrogen bond population correlation functions and other reversible geminate recombinations obtained from simulations with periodic boundary conditions. Liquid water as a test case.

The kinetics of breaking and re-formation of hydrogen bonds (HBs) in liquid water is a prototype of reversible geminate recombination. HB population correlation functions (HBPCFs) are a means to study the HB kinetics. The long-time limiting behavior of HBPCFs is controlled by translatoric diffusion and shows a t-3/2 time-dependence, which can be described by analytical expressions based on the HB acceptor density and the donor-acceptor inter-diffusion coefficient. If the trajectories are not properly "unwrapped," the presence of periodic boundary conditions (PBCs) can perturb this long-time limiting behavior. Keeping the trajectories "wrapped," however, allows for a more efficient calculation of HBPCFs. We discuss the consequences of PBCs in combination with "wrapped" trajectories following from the approximations according to Luzar-Chandler and according to Starr, each deviating in a different fashion from the true long-time limiting behavior, but enveloping the unperturbed function. A simple expression is given for estimating the maximum time up to which the computed HBPCFs reliably describe the long-time limiting behavior. In addition, an exact a posteriori correction for systems with PBCs for "wrapped" trajectories is derived, which can be easily computed and which is able to fully recover the true t-3/2 long-time behavior. For comparison, HBPCFs are computed from MD simulations of TIP4P/2005 model water for varying system sizes and temperatures of 273 and 298K using this newly introduced correction. Implications for the computations of HB lifetimes and the effect of the system-size are discussed.

Transparent and mechanically strong hydrogen-bonded polymer complex elastomers with improved self-healability under ambient conditions

A major challenge in designing self-healing polymeric materials is to combine robust mechanical properties and high healing efficiency. Herein, we report a kind of transparent, hydrogen-bonded polymer complex elastomers with both good mechanical strength and rapid self-healing capability under ambient conditions. Such elastomers were simply fabricated by in situ photoinitiated random copolymerization of acrylic acid (AA) and N-acryloyl-6-aminocaproic acid (A6ACA), in the presence of a linear polyethylene oxide (PEO). By evaporating water molecules from the samples via free drying, the dynamical hydrogen bonding between PEO and poly(A6ACA-co-AA) were substantially formed, which endowed the polymer chains to form physically crosslinked three-dimensional polymer network, as well as the topological chain entanglements. The resulting optically transparent elastomers exhibited both good mechanical strengths (at break) as high as 1.73 MPa, and excellent stretchability that could be stretched up to 24 times their initial length, respectively. Comparing with the elastomers based on PEO and PAA homopolymer without the A6ACA comonomer, the introduction of A6ACA as a comonomer afforded complex elastomers with comparable mechanical strength and, more importantly, significantly improved self-healing efficiency even under ambient conditions, probably due to the significantly decreased glass transition temperature that facilitated chain mobility and reformation of hydrogen bonds. It is therefore believed that the copolymerization strategy offers a practical method to tune the compositions and to tailor the properties of hydrogen-bonded polymer complexes for engineering elastomers with balanced mechanical and self-healing performance under ambient environment for various applications.

Flow-Induced Formation of Thin PEO Fibers in Water and Their Stability After the Strain Release

Recently, we have shown that a tensile stress applied to chains of poly(ethylene oxide) (PEO) in water reduces the solubility and leads to phase separation of PEO chains from water with the formation of a two-phase region. In this work, we further elucidate the generic mechanism behind strain-induced phase transitions in aqueous PEO solutions with concentrations of 50-60 wt % by performing all-atom molecular dynamics simulations. In particular, we study the stability of oriented PEO fibers after removing stretching forces. We found that the size of the PEO bundle increased with time, which is associated with the dissolution of PEO chains on the fiber surface due to the reformation of hydrogen bonds between the outer PEO molecules and water. For precise characterization of the fibers, the scattering patterns (small- and wide-angle X-ray spectra) for configurations taken at different relaxation times are calculated. The tendency of the oligomer chains to be peeled off from the surface of the bundle eventually might lead to a complete dissolution of the PEO fiber. We conclude that either entanglement constraints or a quick drying process are necessary to conserve the fiber structure in a quiescent state. The scattering results show that external strain induced a liquid-liquid phase separation first. On long time scales, this can be a precursor for crystallization of the fiber.

Prion Interaction with Normal Protein in Topological Changing Secondary Structure to Aggregation

<p>Prion is a protein smaller than virus and it infects host in the absence of nucleic acid. The secondary structure of protein folds incorrectly from α-helices to β-sheets through breaking and re-formation of hydrogen bond. Structural analogy of α-helix and DNA double helix and comparing differences between α-helix and β-sheet show prion's infectivity and propagation. Aggregates of dimers and polymers generate β-amyloid fibril in Alzheimer's disease.</p>

Branched Alkylamine-Reduced Graphene Oxide Hybrids as a Dual Proton-Electron Conductor and Organic-Only Water-Splitting Photocatalyst.

We report multifunctionalities including the solid electrolytic property, electron conductivity (EnC), and photocatalytic water splitting (PWS) ability of organic-only hybrids obtained by intercalating short and branched-chain alkylamines including methylamine (MA), butylamine (BA), pentylamine (PA), and isomethylbytylamine (IMBA) in reduced graphene oxide (rGO). The alkylamine-rGO hybrids were synthesized by a facile solid-state reduction process. Within the series, IMBA-rGO exhibited high proton conductivity (PrC), EnC, and optimized PWS capacity. The PrC of IMBA-rGO was from 10-4 to 10-3 S cm-1, which is only half an order less than that for pristine GO. The EnC was 1.25 μA/V. Though the PWS performances of MA-rGO, BA-rGO, and PA-rGO were comparatively lower, IMBA-rGO could generate about 1.5 times H2 compared with that for R-TiO2. The IR spectra indicate the association of IMBA and GO by chemical bonds. The Raman spectra show the transformation of GO's nonconductive sp3 carbon sites into electron-conductive sp2 carbon centers. The thermogravimetric analysis show improved water adsorbing capacity of IMBA-rGO, which resulted in higher PrC. Doping of the nitrogen atom at the graphitic sp2 system was confirmed from the presence of pyrrolic N in X-ray photoelectron spectroscopy spectra. The resultant N-type semiconducting behavior is majorly responsible for the PWS process. The powder X-ray diffraction analysis indicates a more flexible interlayer space in IMBA-rGO, which facilitates both the reformation of hydrogen bonds during proton conduction and water dynamics during photocatalysis. The material indicates the possibility of devising graphene-based organic-only multifunctional hybrids.

Silicone dielectric elastomer with improved actuated strain at low electric field and high self-healing efficiency by constructing supramolecular network

Dielectric elastomers (DE) suffer from cracks and breaks during repeated cycles, thus a DE material with both high actuated strain (SA) and self-healing ability is highly desired. Herein, for the first time we report a self-healable silicone DE (SiR-SN) with large SA under low electric field by constructing supramolecular network assembled by hydrogen bonds and ionic bonds from two components involving carboxyl modified polymethylvinylsiloxane (PMS-g-COOH) and amino terminated polydimethylsiloxane (PDMS-NH2). The results show that as PMS-g-COOH content increases, the dielectric constant (ε′) of SiR-SN increases owing to an increase in dipole content whereas the elastic modulus (Y) decreases because of a decrease in crosslinking density, leading to the significantly increased SA at a given electric field. SiR-SN with 0.2/1 of the mass ratio of PMS-g-COOH to PDMS-NH2 shows much higher ε′ and SA than the commercial silicone DE. Interestingly, self-healing of SiR-SN at 80 °C leads to the re-formation of hydrogen bonds, and thus the recovery of network structure, whereas self-healing at 100 °C can lead to the conversion from hydrogen bonds into ionic ones, and thus the change of network structure. As a result, a self-healing efficiency of 115% in tensile strength and almost 100% in SA at a given electric field can be achieved after self-healing at 80 °C for 5 h, whereas an increase in Y and higher breakdown strength can be achieved after self-healing at 100 °C, which may sustain the repeated stress and prolong the service life. It is promising that this new self-healable silicone dielectric elastomer with large actuated strain under low electric field could be used especially in biological and medical fields.

Optimization design on simultaneously strengthening and toughening graphene-based nacre-like materials through noncovalent interaction

Nacre exhibits outstanding mechanical properties due to its hierarchically microstructural features and associated multiscale deformation behaviors, enlightening human to design high-performance graphene-based nacre-like materials (GNMs) in the past decade. However, those GNMs mimicking brick-and-mortar microstructure always cannot give consideration to both strength and toughness because the pullout process of graphene oxide (GO) sheets that amplifies toughness in GNMs is extremely limited compared to natural nacre. Toward this end, a combination of modified shear-lag model and atomic simulations is proposed to investigate the optimal strategy of simultaneously strengthening and toughening for GNMs reinforced by strong noncovalent interfacial interactions. The modified shear-lag model can well couple the interlayer sliding and structural stability to characterize the toughening effect during the pullout process. We demonstrate that the interfacial toughness and shear strength tuned by interlayer noncovalent interactions significantly impact the effective tensile strength of GNMs, while toughness is mainly dominated by the interlayer sliding before strain localization during the pullout process of GO sheets. Melamine molecule is chosen as the representative interlayer crosslink agent owing to the ultrastrong noncovalent interaction between melamine and GO. Our atomic simulations indicate that melamine bound to GO by anomalous hydrogen bonding can greatly improve the interfacial shear stress and maintain the interlayer energy-dissipation efficiency resulting from the breaking and reforming of hydrogen bonds. An optimal range of melamine content and GO oxidation degree is then explored for synchronously superior strength and toughness by balancing the competitions among the reduction of intralayer tensile limit of GO sheets, the improvement of the interlayer shear strength, and the reduction of interfacial toughness. In particular, a scaling law is proposed as the evaluation criterion to correlate the inner inelastic deformation of GNMs and their mechanical properties, revealing why interlayer noncovalent interaction can optimize strength and toughness simultaneously while most other crosslinks usually cannot.

Wood–Moisture Relationships Studied with Molecular Simulations: Methodological Guidelines

This paper aims at providing a methodological framework for investigating wood polymers using atomistic modeling, namely, molecular dynamics (MD) and grand canonical Monte Carlo (GCMC) simulations. Atomistic simulations are used to mimic water adsorption and desorption in amorphous polymers, make observations on swelling, mechanical softening, and on hysteresis. This hygromechanical behavior, as observed in particular from the breaking and reforming of hydrogen bonds, is related to the behavior of more complex polymeric composites. Wood is a hierarchical material, where the origin of wood-moisture relationships lies at the nanoporous material scale. As water molecules are adsorbed into the hydrophilic matrix in the cell walls, the induced fluid–solid interaction forces result in swelling of these cell walls. The interaction of the composite polymeric material, that is the layer S2 of the wood cell wall, with water is known to rearrange its internal material structure, which makes it moisture sensitive, influencing its physical properties. In-depth studies of the coupled effects of water sorption on hygric and mechanical properties of different polymeric components can be performed with atomistic modeling. The paper covers the main components of knowledge and good practice for such simulations.

Intermolecular Dynamics of Water: Suitability of Reactive Interatomic Potential.

Reactive interatomic potentials for water have been developed by researchers based on their ability of bond breaking and formation, which have numerous advantages and applications in different fields. The question that is being addressed in this work is whether these reactive interatomic potentials properly account for the intermolecular dynamics of water that includes both hydrogen bonding as well as librational motions. It should be noted that breaking and reformation of hydrogen bonds occur prior to covalent bond breaking of water molecules (which requires a significant amount of energy), which has numerous applications in absorption as well as solvation problems. Based on correlations with experimental observations, it has been demonstrated that the current forms of the reactive potentials perform poorly in comparison to other well-established empirical interatomic potential models of water, such as TIP4P/2005f, with regard to the intermolecular dynamics of water. Translational and rotational diffusivities, power spectra, and hydrogen-bond lifetime analyses are carried out and compared to available experimental data as well as those obtained from TIP4P/2005f models to arrive at such conclusions.

Smart behavior of collagen skin: water-sensitive shape memory

Abstract Collagen skin (CS) composed of collagen fiber is environment friendly biomaterial may be responsive to water for shape recovery form their temporarily fixed shape. This water induced smart behavior is regarded as shape memory (SM) ability. In this study, the water induced SM effect of CS and its mechanism regarding to structural component was first time investigated. The fixability under both axial and non-axial deformation are high with the fixation rate reach up to 100% while the shape recovery rate (ranged from 60 % to 98 %) is related to the temporary shape and cycle numbers. The effect of water on mechanical behavior, thermal properties, and structural component (hydrogen bonds) of CS the were systematically examined. The reversible cleavage and reforming of hydrogen bonds within collagen was thereafter proposed as “switch” to trigger the shape deformation and recovery in the hypothesized SM mechanism model. This research is expected to reveal a sophisticated structure not found in literature for extremely smart materials and demonstrate an excellent example of adding value to unwanted, discarded by-products by turning into desired and functional materials

Flexible photoluminescent humidity sensing material based on electrospun PVA nanofibers comprising surface-carboxylated QDs

Flexible humidity-sensitive materials have drawn increasing attention due to their vital function in monitoring ambient humidity for tactile sensors, allowing them to approach the functionality of human skin. In this work, an electrospun polyvinyl alcohol (PVA)-based nanofiber film comprising surface-carboxylated CdSe/CdxZn1-xS quantum dots (QDs) is fabricated as a high-performance flexible humidity sensing material, based on the relationship between its photoluminescence (PL) and the humidity. The as-prepared film shows excellent PL-humidity linearity, a wide sensing range from 10% to 90% relative humidity, a relatively fast response time, good recoverability, and flexibility. The humidity sensing mechanism can be attributed to the breaking and reforming of hydrogen bonds and proton transfer occurring at the PVA-QD interfaces. This flexible humidity-sensitive material is believed to be a good candidate for humidity-sensitive components in electronic skin.