Study of crosslinker size on the rheological properties of borate crosslinked guar gum.

Borate crosslinked guar gum gels have played a vital role in stimulating oil and gas wells for many years; however, the high dosage of guar gum in the existing fracturing fluid will increase the cost and cause more damage to the reservoir and ultimately affect the effect of stimulation. In this study, borate esters are modified onto polyethyleneimine (PEI) of different molecular weights, affording organic borate crosslinkers of different sizes. By analyzing the effect of crosslinker size on gel rheology, sand-carrying properties, and microstructure, it is observed that the crosslinking efficiency is most significantly enhanced when the crosslinker size is similar to the diameter of the guar gum molecules.

Enhancement and Restoration of Scratched Murals Based on Hyperspectral Imaging-A Case Study of Murals in the Baoguang Hall of Qutan Temple, Qinghai, China.

Environmental changes and human activities have caused serious degradation of murals around the world. Scratches are one of the most common issues in these damaged murals. We propose a new method for virtually enhancing and removing scratches from murals; which can provide an auxiliary reference and support for actual restoration.

Lignin reinforced hydrogels with multi-functional sensing and moist-electric generating applications.

Hydrogels, including PVA hydrogels, have numerous applications in many fields; however, their poor mechanical strength limits their utilization potential. Lignin, the most abundant aromatic biopolymer in nature from lignocellulosic biomass, is presently under-utilized. Herein, we used lignin to improve strength and impart pH-responsive properties of PVA hydrogel.

Experimental Study on High-Performers Quaternary Copolymer Based on Host-Guest Effect.

A quaternary polymer (HGP) was prepared by the free-radical polymerization of acrylamide, acrylic acid, maleic anhydride functionalized -cyclodextrin (MAH--CD), and N-(3-methacrylamidopropyl)-N, N-dimethylnaphthalen-1-aminium chloride (NAP). It was found that host-guest behavior occurred most effectively at a molar rate of NAP and CD with 1:1, which exhibited better solubility than hydrophobically associative polymer. Moreover, the as-prepared polymer has superior salt tolerance, shear resistance, and viscoelasticity due to host-guest strategy.

Synthesis and Anticancer Properties of Functionalized 1,6-Naphthyridines.

The burgeoning interest in synthesis and biological applications of 1,6-naphthyridines reflects the importance of 1,6-naphthyridines in the synthetic as well as medicinal chemistry fields. Specially, 1,6-naphthyridines are pharmacologically active, with variety of applications such as anticancer, anti-human immunodeficiency virus (HIV), anti-microbial, analgesic, anti-inflammatory and anti-oxidant activities. Although collective recent synthetic developments have paved a path to a wide range of functionalized 1,6-naphthyridines, a complete correlation of synthesis with biological activity remains elusive.

Drag Reduction Performance and Mechanism of Hydrophobic Polymers in Fresh Water and Brine.

Three kinds of drag reducer were synthesized by inverse emulsion polymerization and named PHWAM-1, PHWAM-2, and PHWAM-3. Drag reduction (DR) tests showed that the three drag reducers have different DR characteristics in fresh water and various saline waters because of their different types of hydrophobic monomers. PHWAM-1, without hydrophobic monomers, performs better in fresh water, while PHWAM-2 and PHWAM-3, with hydrophobic monomers, perform better in brine.

Application of a Zwitterionic Hydrophobic Associating Polymer with High Salt and Heat Tolerance in Brine-Based Fracturing Fluid.

ZIDPM, a zwitterionic hydrophobic associating polymer, has equivalent positive and negative charges and some hydrophobic monomers with twin-tailed long hydrophobic chains. It exhibits a great heat resistance and salt tolerance to the common salt in formation brine (MgCl, CaCl, NaCl, and KCl), which is attributed to its anti-polyelectrolyte effect and strong association force. High-salinity water (seawater or formation water) can be prepared as a fracturing fluid directly.

Preparation of a Novel Fracturing Fluid System with Excellent Elasticity and Low Friction.

The quaternary polymer was synthesized by radical polymerization and characterized by H NMR. The tests of critical associating concentration and SEM suggest that there is a multilayered and robust network structure in the polymer solution. An excellent elasticity in the polymer solution by the first normal stress difference, viscoelasticity, and thixotropy was observed.

Redox-Noninnocent Ligand-Supported Vanadium Catalysts for the Chemoselective Reduction of C═X (X = O, N) Functionalities.

Catalysis is the second largest application for V after its use as an additive to improve steel production. Molecular complexes of vanadium(V) are particularly useful and efficient catalysts for oxidation processes; however, their ability to catalyze reductive transformations has yet to be fully explored. Here we report the first examples of polar organic functionality reduction mediated by V.

Improving the Thermal Stability of Hydrophobic Associative Polymer Aqueous Solution Using a "Triple-Protection" Strategy.

Because of their high viscoelasticity, Hydrophobic Associative Water-Soluble Polymers (HAWSPs) have been widely used in many industrial fields, especially in oilfield flooding and fracturing. However, one major problem which limits the wide applications of HAWSPs is their weak resistance to high temperatures. Once the temperature increases over 100 °C, the viscosity of the fracturing fluid decreases rapidly, because high temperatures reduce fluid viscosity by oxidizing the polyacrylamide chains and weakening the association of hydrophobic groups.

High Performance Clean Fracturing Fluid Using a New Tri-Cationic Surfactant.

In order to improve the heat resistance of current clean fracturing fluids, a novel cationic surfactant (VES-T), composed of three single-chains and a spacer group, was designed and synthesized as thickener for the fluids. Various performances of such VES-T fluid in the presence of NaSal were evaluated carefully. Study of the rheological properties demonstrated that the fluids with varying concentrations (3⁻5 wt %) of VES-T have excellent thermal stabilities under ultra-high temperatures ranging from 140 to 180 °C.

Study of a Novel Gemini Viscoelastic Surfactant with High Performance in Clean Fracturing Fluid Application.

Gemini surfactant, as a functionally flexible polymer-like material in the aqueous solution, has attracted increased attention in reservoir stimulation of hydraulic fracturing in recent decades. A new Gemini cationic viscoelastic surfactant named JS-N-JS, which has a secondary amine spacer group and two ultra-long hydrophobic tails, was synthesized from erucamidopropyl dimethylamine, diethanolamine, and thionyl chloride as a thickener for hydraulic fracturing fluid. Compared with some Gemini cationic surfactant with methylene spacer, JS-N-JS showed a lower critical micellar concentration (CMC) and higher surface activity due to the hydrogen bond formed between the secondary amine and water molecule intends to reduce electrostatic repulsion, which is more beneficial to be the fracturing fluid thickener.

Novel Hydrophobic Associating Polymer with Good Salt Tolerance.

A hydrophobic associating polymer named DiPHAM (acrylamide/sodium acrylamide-2-methylpropanesulfonic/sodium acrylate/,-di--dodecylacrylamide) with good salt tolerance was synthesized via photo-initiation polymerization. The critical association concentration (CAC) of DiPHAM was determined by viscosity changes to be 490 mg/L with different DiPHAM concentrations and particle sizes varied under such dynamic conditions. The influences of aqueous metal ions with different charges on its aqueous solution were investigated by measuring apparent viscosity, viscoelasticity, thixotropy, rheology, and particle size, and by SEM observation.

Preparation of a Hydrophobic-Associating Polymer with Ultra-High Salt Resistance Using Synergistic Effect.

Polymer, SRP-2-1, was synthesized by micellar polymerization and characterized by ¹H NMR. Salt tolerance and viscoelasticity tests verified that the salt resistance of SRP-2-1 was promoted by the synergistic effects of oxyethylene groups, sulfonate, and hydrophobic chains. It is suggested that the structure of SRP-2-1 became more compact with increasing salinity.

Preparation of a novel fracturing fluid with good heat and shear resistance.

A new terpolymer (MAS-1) was created by copolymerizing acrylamide (AM), acrylic acid (AA), and 4-isopropenylcarbamoyl-benzene sulfonic acid (AMBS). Thermogravimetric analysis (TGA) suggested that MAS-1 has better heat resistance and meets the requirements for a fracturing fluid at 200 °C. X-ray diffraction (XRD), and conductivity tests showed that MAS-1 has good water solubility.

Intermolecular Acetoxyaminoalkylation of α-Diazo Amides with (Diacetoxyiodo)benzene and Amines.

Multicomponent reactions of diazo compounds have attracted much attention in recent years. Such transformations are generally conducted by applying transition metal catalysis and involve the corresponding metal carbenes as key intermediates. In this letter, a metal-free three-component intermolecular acetoxyaminoalkylation of α-diazo amides with tertiary aryl amines and (diacetoxyiodo)benzene is presented.

Visible light-promoted ring-opening functionalization of unstrained cycloalkanols inert C-C bond scission.

Described herein is a novel, useful, visible light-promoted ring-opening functionalization of unstrained cycloalkanols. Upon scission of an inert cyclic C-C σ-bond, a set of medium- and large-sized rings are readily brominated under mild reaction conditions to afford the corresponding distal bromo-substituted alkyl ketones that are hard to synthesize otherwise. The products are versatile building blocks, which are easily converted to other valuable molecules in one-step operation.

Ligand-Free, Cu- and Fe-Catalyzed Selective Ring-Opening Arylations of Benzoxazoles with Aryl Iodides.

Cu- or Fe-based catalyst systems have been reported to selectively catalyze the N,N-diarylation or N-monoarylation of benzoxazoles ring-opening with aryl iodides in the absence of additional added ligand in polyethylene glycol under an inert atmosphere. Two types of coupling products (triphenylamines and diphenylamines) have been examined and the reaction routes can be simply controlled by changing the metal salts (Cu or Fe) as catalyst. A range of substrates have been investigated for the diverse reactions, and the corresponding arylation products were achieved in good to high yields.

The Application of Copper/Iron Cocatalysis in Cross-Coupling Reactions.

For conventional cross-couplings in organic chemistry, precious metal (such as Pd or Rh) complexes have been the preferable choices as catalysts. However, their high cost, toxicity, and potential contamination of products limit their massive applications on some occasions, particularly in the pharmaceutical industry, where close monitoring of the metal contamination of products is required. Therefore, the use of metals that are less expensive and less toxic than Pd or Rh can be greatly advantageous and earth abundant metal (such Fe or Cu) catalysts have shown promise for replacing the precious metals.

Cyclopentadiene Construction via Rh-Catalyzed Carbene/Alkyne Metathesis Terminated with Intramolecular Formal [3 + 2] Cycloaddition.

A new type of intramolecular carbene cascade reaction of alkynyl-tethered styryl diazoesters is presented, which is terminated with a formal [3 + 2] cycloaddition to give the bicyclic cyclopentadiene derivatives in high yields and selectivity. Additionally, it was found that the β-H shift is the dominating process in the case of alkyl alkyne-tethered substrates.

NaI-Mediated Acetamidosulphenylation of Alkenes with Nitriles as the Nucleophiles: A Direct Access to Acetamidosulfides.

An example of a transition-metal-free, direct, and efficient acetamidosulphenylation reaction of alkenes using nitriles as the nucleophiles via a radical process is presented. This reaction shows a broad substrate scope and high regioselectivity and provides straightforward access to acetamidosulfide derivatives in moderate to high yields.

Cu-Catalyzed direct cyanation of terminal alkynes with AMBN or AIBN as the cyanation reagent.

A Cu-catalyzed direct cyanation of terminal alkynes was reported with broad substrate generality in moderate to high yield, and AMBN (azobisisoamylonitrile)/AIBN (azobisisobutyronitrile) were used as less toxic and effective cyanating sources in open air. Interestingly, addition products were selectively achieved as the major product under the same conditions in argon.

Phosphoric Acid-Mediated Synthesis of Vinyl Sulfones through Decarboxylative Coupling Reactions of Sodium Sulfinates with Phenylpropiolic Acids.

A novel phosphoric acid -mediated synthesis of vinyl sulfones through decarboxylative coupling reactions of sodium sulfinates with phenylpropiolic acids is described. This transformation is efficient and environmentally friendly.

A NCS mediated oxidative C-H bond functionalization: direct esterification between a C(sp(3))-H bond and carboxylic acids.

A transition metal free oxidative C-H bond functionalization/esterification of α-alkoxy alkanes with acids is described in this report. This method is effectively mediated by NCS instead of traditional oxidants, like TBHP or its derivatives, and directly generates the esterification products in moderate to high yield under mild conditions. This tranformation constitutes a practical and general approach toward various α-acyloxy ethers with broad substrate generality; alkyl-, aryl-, alkenyl- and alkynyl-carboxylic acids are all well tolerated.