Double network self-healing hydrogel based on hydrophobic association and ionic bond for formation plugging

Self-healing hydrogels have attracted tremendous attention in the field of oil and gas drilling and production engineering because of their excellent self-healing performance after physical damage.In this study,a series of double network self-healing(DN_(SA))hydrogels based on hydrophobic association and ionic bond were prepared for plugging pores and fractures in formations in oil and gas drilling and production engineering.The mechanical,rheological,and self-healing properties of the DN_(SA)hydrogels were investigated.Results revealed that the DN_(SA)hydrogels exhibited excellent mechanical properties with a tensile stress of 0.67 MPa and toughness of 7069 kJ/cm^(3) owing to the synergistic effect of the double network.In addition,the DN_(SA)hydrogels exhibited excellent compression resistance,notch insensitivity,and self-healing properties.The DN_(SA)-2 hydrogel was granulated and made into gel particles with different particle sizes and used as a plugging agent.The self-healing mechanism of DN_(SA)-2 hydrogel particles in fractures was explored,and it’s plugging effect on fractures of different widths and porous media of different permeabilities were investigated.Experimental results revealed that the plugging capacity of the DN_(SA)-2 hydrogel particles for a fracture with width of 5 mm and a porous medium with a permeability of 30μm^(2) was 3.45 and 4.21 MPa,respectively,which is significantly higher than those of commonly used plugging agents in the oilfield.The DN_(SA)hydrogels with excellent mechanical and self-healing properties prepared in this study will provide a new approach for applying hydrogels in oil and gas drilling and production engineering.

COSMO-RS: An ionic liquid prescreening tool for gas hydrate mitigation

Recently ionic liquids(ILs) are introduced as novel dual function gas hydrate inhibitors. However, no desired gas hydrate inhibition has been reported due to poor IL selection and/or tuning method. Trial & error as well as selection based on existing literature are the methods currently employed for selecting and/or tuning ILs. These methods are probabilistic, time consuming, expensive and may not result in selecting high performance ILs for gas hydrate mitigation. In this work, COSMO-RS is considered as a prescreening tool of ILs for gas hydrate mitigation by predicting the hydrogen bonding energies(E_(HB)) of studied IL inhibitors and comparing the predicted E_(HB) to the depression temperature(?) and induction time. Results show that, predicted EHBand chain length of ILs strongly relate and significantly affect the gas hydrate inhibition depression temperature but correlate moderately(R = 0.70) with average induction time in literature. It is deduced from the results that, ? increases with increasing IL EHBand/or decreases with increasing chain length. However, the cation–anion pairing of ILs also affects IL gas hydrate inhibition performance. Furthermore, a visual and better understanding of IL/water behavior for gas hydrate inhibition in terms of hydrogen bond donor and acceptor interaction analysis is also presented by determining the sigma profile and sigma potential of studied IL cations and anions used for gas hydrate mitigation for easy IL selection.

A Future Life of Binary Phase Diagrams

The article raises the question of what to do with one of the main achievements of metal science in recent years—binary phase diagrams. These diagrams play a key role in the science of alloys and therefore their reliability must be complete. However, the discovery of the “ordering-separation” phase transition, which showed that in binary alloys at certain temperatures the sign of the chemical interatomic interaction changes (and, consequently, the microstructure changes), forces us to reconsider our ideas about those areas. Currently, these areas are designated on diagrams as areas of a “disordered solid solution.” This article proposes, using transmission electron microscopy, to study all the so-called solid solution regions, and apply the results obtained to the studied regions of the phase diagram.

Experimental Detection of Diffusion Micro-pairs in a Structure of the Ni_(65)Mo_(20)Cr_(15)Alloy

The article raises the question of how diffusion pairs A/B,A/C,and B/C form in three-component alloys ABC.This issue solves experimentally using the TEM(transmission electron microscopy)method and Ni65Mo20Cr15 alloy.The quenching of this alloy from a liquid showed that such pairs form in the liquid state of the alloy,and as the quenching temperature decreases,particles of the new phases form inside them.We concluded that not a disordered solid solution after high-temperature quenching“from a region of disordered solid solution at the phase diagrams”is the starting point for the formation of a low-temperature microstructure,but a liquid state,into which the alloy passes during its melting.The author hopes the results got will lead to a reorientation of our ideas about alloys and will change a lot both in the theory of alloys and in the technology of their manufacture.

Effects of oxygen vacancy on bond ionicity,lattice energy,and microwave dielectric properties of CeO_(2) ceramics with Yb^(3+) substitution

Novel Yb_(x)Ce_(1-x)O_(2-0.5x)(x=0-0.8)ceramics,designed by replacing Ce^(4+)with Yb^(3+)ions were prepared by conventional oxide reaction,and the structural stability of the cubic fluorite structure was assessed using lattice energy and ionic properties of Ce/Yb-O bonds.The oxygen vacancy caused by unequal substitution,which played a decisive role in bond ionicity and lattice energy,was analyzed experimentally by XPS and also theoretically by first principles.The Yb_(x)Ce_(1-x)O_(2-0.5x) ceramics maintain a stable cubic fluorite structure when x≤0.47,corresponding to the minimum lattice energy of 4142 kJ/mol with the lowest ionicity as ƒ_(i)=87.57%.For microwave dielectric properties,when the Yb_(x)Ce_(1-x)O_(2-0.5x)(x=0-0.4)ceramics are pure phase,the porosity-corrected permittivity is dependent on the bond ionicity.The Q׃ values are related to the lattice energy and grain distribution.The temperature coefficient of resonance frequency has been analyzed using bond valence.When the Yb_(x)Ce_(1-x)O_(2-0.5x)(x=0.5-0.8)ceramics are multiple phases,the microwave dielectric properties are associated with the phase composition and grain growth.

Formation of Diffusion Pairs as an Initial Stage in the Process of Decomposition of Alloys

The paper discusses the researches that formed the basis of the study of the transition of “ordering-phase separation” and the reasons for such transition occurrence. Experimental results have presented what diffusion pairs are and how they occur in binary and multicomponent alloys. The paper illustrates that the chemical bonds between atoms are realized on the principle of pair interaction in both solid and liquid states of the alloy. The process of separating a multi-component ABC alloy into diffusion pairs A/B, A/C, and B/C occurs in a liquid solution, where the diffusion mobility of atoms is very high, and the resistance of the environment is relatively low. The driving force of such a process is the chemical attraction between like and unlike atoms, that is, the tendency to phase separation and the tendency to ordering. Quenching the liquid alloy into the water fixes a microstructure consisting of microscopic areas corresponding in composition to one or another diffusion pairs. The paper shows what exactly should be done so that such a branch of science as Materials Science could get rid of the empirical approach when creating new alloys.

Preparation of dynamic polyurethane networks with UV-triggered photothermal self-healing properties based on hydrogen and ion bonds for antibacterial applications

Photo-induced self-healing composites have attracted more and more attention as a kind of materials that can be controlled remotely and accurately in real time.Here,we report a strategy of a photo-responsive system based on hydrogen and ion bonds capable of performing self-healing process by ultraviolet wave-lengths,which is covalently cross-linked zinc-dimethylglyoxime-polyurethane coordination network with triple dynamic bonds.The recombination of hydrogen bond and metal coordination bond produces ef-fective healing performance.The self-healing behavior and temperature dependence of 3D micro-crack is investigated by molecular dynamics simulations to reveal the mechanism of self-healing at molecu-lar level.Moreover,the hybrid of copper-doped zinc oxide not only provides metal coordination bonds to enhance the self-healing rate,but also enhances the photothermal effect and anti-bacterial properties of polyurethane.Importantly,doping of copper generates more defects and forms a space charge layer on the surface of zinc oxide.The defects could trap surface electrons and holes,preventing the recom-bination of photo-induced electron-hole pairs,generating more heat through lattice vibration.Therefore,under ultraviolet light irradiation,the polyurethane can reach 62.7°C for 60 s,and the scratches of the polyurethane can be healed within 30 min and fully healed within 1 h.

Synthesis and properties of ionic conduction polymer for anodic bonding

In this study,powders of polyethylene oxide（PEO） and lithium perchlorate（Li Cl O4） were used as the raw materials for producing the ionic conduction polymer PEO–Li Cl O4 with different complex-ratios and used for anodic bonding through high energy ball milling method,and meanwhile,X-ray diffraction,differential scanning calorimetry（DSC）,ultraviolet absorption spectrum test analysis,and other relevant methods were adopted to research the complexation mechanism of PEO and Li Cl O4 and the impact of the ionic conduction polymer with different complex-ratios on the anodic bonding process under the action of the strong static electric field.The research results showed that the crystallization of PEO could be effectively obstructed with increased addition of Li Cl O4,thus increasing the content of PEO–Li Cl O4 in amorphous area and continuously improving the complexation degree and the room-temperature conductivity thereof,and that the higher room-temperature conductivity enabled PEO–Li Cl O4 to better bond with metallic aluminum and have better bonding quality.As the new encapsulating material,such research results will promote the application of new polymer functional materials in micro-electromechanical system（MEMS） components.

Synthesis of mid-dicarboxy polystyrene by ATRP and formation of ionic-bonded supramolecules

Dimethyl 4,6-bis(bromomethyl)isophthalate was synthesized by bromomethylation,oxidation,esterification and bromination of 1,3-dimethylbenzene.This was used to initiate the atom transfer radical polymerization of styrene successfully.Results showed that the process had some of the good characteristics of controlled/living free radical poly-merization.The molecular weight of the obtained polymer increased linearly with monomer conversion,its molecular weight distribution was very narrow,and a linear relationship between ln([M]0/[M])and polymerization time was found.A well-defined novel structural polystyrene containing two ester groups in the mid-main chain was prepared with con-trolled molecular weight and narrow polydispersity.The structure of the polymer was confirmed by 1H-NMR spectra.After being hydrolyzed,dicarboxy polystyrene was obtained and used to form ionic-bonded supramolecules with 1-dodecanamine as a model of the star-shaped supramolecules.The supramolecules formed were characterized by Fourier transform infrared(FTIR)spectrum.

Hydrogen bonding mediated ion pairs of some aprotic ionic liquids and their structural transition in aqueous solution

Ion pair speciation of ionic liquids(ILs) has an important effect on the physical and chemical properties of ILs and recognition of the structure of ion pairs in solution is essential. It has been reported that ion pairs of some ILs can be formed by hydrogen bonding interactions between cations and anions of them. Considering the fact that far-IR(FIR) spectroscopy is a powerful tool in indicating the intermolecular and intramolecular hydrogen bonding, in this work, this spectroscopic technique has been combined with molecular dynamic(MD) simulation and nuclear magnetic resonance hydrogen spectroscopy(~1H NMR) to investigate ion pairs of aprotic ILs [Bmim][NO_3], [BuPy][NO_3], [Pyr_(14)][NO_3], [PP_(14)][NO_3] and [Bu-choline][NO_3] in aqueous IL mixtures. The FIR spectra have been assigned with the aid of density functional theory(DFT) calculations, and the results are used to understand the effect of cationic nature on the structure of ion pairs. It is found that contact ion pairs formed in the neat aprotic ILs by hydrogen bonding interactions between cation and anion, were still maintained in aqueous solutions up to high water mole fraction(say 0.80 for [BuPy][NO3]). When water content was increased to a critical mole fraction of water(say 0.83 for [BuPy][NO3]), the contact ion pairs could be transformed into solvent-separated ion pairs due to the formation of the hydrogen bonding between ions and water. With the further dilution of the aqueous ILs solution, the solvent-separated ion pairs was finally turned into free cations and free anions(fully hydrated cations or anions). The concentrations of the ILs at which the contact ion pairs were transformed into solvent-separated ion pairs and solvent-separated ion pairs were transformed into free ions(fully hydrated ion) were dependent on the cationic structures. These information provides direct spectral evidence for ion pair structures of the aprotic ILs in aqueous solution. MD simulation and ~1H NMR results support the conclusion drawn from FIR spectra investigations.

Rapid proton diffusion in hydroxyl functionalized imidazolium ionic liquids

There is considerable interest in using ionic liquids(ILs) as protic electrolytes. However, the reported proton transfer rate in ILs is quite slow. In this study, we report functionalizing imidazolium ILs with alcohol hydroxyls, aiming at constructing hydrogen bonding networks in the electrolyte, can stimulate fast proton hopping transfer. For demonstration, the diffusion of proton and Cl. in 1-(3-hydroxypropyl)-3-methylimidazolium tetrafluoroboride(C_3OHmimBF_4) were studied using cyclic voltammetry and potentiostatic method at 30 °C. The diffusion coefficient of proton is about one order of magnitude higher than that of Cl. in the same electrolyte, and about 5 times that of proton in the non-hydydroxyl 1-(butyl)-3-methylimidazolium tetrafluoroboride(BmimBF_4) when normalized to the diffusion coefficients of Cl. in respective ILs. In the meantime, 1H NMR spectra revealed a strong hydrogen bonding interaction between proton and C_3OHmimBF_4 which is absent between proton and BmimBF_4, thus the significantly higher diffusion coefficient of proton in C_3OHmimBF_4 may suggest the formation of effective hydrogen bonding networks, enabling rapid proton hopping via the Grotthuss mechanism.

Interplay between Microscopic Structures and Macroscopic Viscoelastic Properties of Polyampholyte Gels

Polyampholyte gels,which have hierarchical structures,exhibit excellent self-healing properties and have great promise for biomaterials and bioengineering.We investigated the relationship between microscopic structures and macroscopic viscoelastic properties of polyampholyte gels and found three factors influencing their viscoelastic properties,including the chemical crosslinking bonds,topological entanglements controlled by monomer concentration,and the ionic bonds.Ionic strength plays a major role on the strength of ionic bonds.A crossover point of elastic modulus and loss modulus was observed in the dynamic frequency sweeps at low monomer concentration or low chemical crosslinking density for gels with intermediate strength of ionic bonds.The solid-liquid transition signaled by the crossover point is a typical feature of dynamic associated gels,representing the dynamical association-dissociation of the ionic bonds and full relaxation of the topological entanglements in the gel network.While the crossover point disappears when the ionic bonds are too weak or too strong to form“permanent”bonds.Consistently,in the non-linear yielding measurement,gels with intermediate strength of the ionic bonds are ductile and yield at very large shear strain due to the self-healing properties and the dynamic association-dissociation of the ionic bonds.But the self-healing properties disappear when the ionic bond strength is too weak or too strong.Our work reveals the mechanism of how the dynamic association-dissociation of ionic bonds influences both the linear and non-linear viscoelastic properties of the polyampholyte gels.

Effects of Binding Energy of Bioinspired Sacrificial Bond on Mechanical Performance of cis-1,4-Polyisoprene with Dual-crosslink

Although bioinspired sacrificial bonds have been demonstrated to be efficient in improving the mechanical properties of polymer materials, the effect of binding energy of a specific dynamic bond on the ultimate mechanical performance of a polymer network with dual-crosslink remains unclear. In this contribution, diamine and sulfur curing package are introduced simultaneously into a sulfonated cis-1,4-polyisoprene to create dually-crosslinked cis-1,4-polyisoprene network with sulfonate-aminium ionic bonds as the sacrificial bonds. Three diamines （primary, secondary and tertiary） with the same spacer between the two nitrogen atoms are used to create the ionic bonds with different binding energies. Although the binding energy of ionic bond does not affect the glass transition temperature of cis-1,4-polyisoprene （IR）, it exerts definite influences on strain-induced crystallization and mechanical performance. The capabilities of diamine in dissipating energy, promoting strain-induced crystallization and enhancing the mechanical performance are in the same order of secondary diamine 〉 primary diamine 〉 tertiary diamine. The variations in mechanical performances are correlated to the binding energy of the ionic bond, which is determined by pKa values.

Microscopic study of binary mixtures between pyrrolidinium bis(triflorosulfonyl)imide and dimethyl sulfoxide/acetonitrile

Molecular interactions of a representative pyrrolidinium-based ionic liquid 1-butyl-l-methyl-pyrrolidinium bis（triflorosulfonyl）- imide （[BMPyrr][TFSI]） with dimethyl sulfoxide （DMSO） and acetonitrile （AN） have been analyzed in this work. Attenuated total reflection Fourier transform infrared spectroscopy （ATR-FTIR） and density functional theory （DFT） calculations are used in the investigation, while excess infrared spectra and two-dimensional correlation spectroscopy are used to explore the data in detail. It has been found that the molecular solvents can interact with TFSI- （mainly with S=O and weakly with S-N-S group）. AN interacts feebly with BMPyrr＋ as compared with the strong interaction of DMSO. The strength of the interactions depends on the electron donating ability of the solvent. Upon mixing, hydrogen bonds regarding C-Hs in cation and S-N-S in anion are weakened, while that regarding S=O in anion is strengthened. Among the C-Hs which are connected directly with the N of the cation, Cl-H is the main interaction site for both DMSO and AN. This means that Cl-H is the most acidic hydrogen in pyrrolidinium cation.