Preparation and solution properties of a novel cationic hydrophobically modified polyacrylamide for enhanced oil recovery

Abstract

A novel cationic water-soluble monomer allyldimethylisooctylammonium bromide (ADIAB) containing a short-chain alkane was synthesized successfully. This monomer was copolymerized with acrylamide and sodium acrylate to produce hydrophobically modified polyacrylamide (HMPAM) using solution polymerization without surfactants. The structures of monomer ADIAB and HMPAM were characterized with infrared spectroscopy and nuclear magnetic resonance spectroscopy. Influence of preparation condition on viscosities of products was studied. The aqueous solution viscosity of the terpolymer was also investigated as functions of concentration, temperature and salinity. The results showed that when the temperature exceeds the 60?°C and NaCl concentration exceeds about 2000?mg/L, the temperature and salt tolerance characters of terpolymer were demonstrated. The enhanced oil recovery tests were initially carried out using homogeneous sandpack models.     

Rationally Designing Molecularly Imprinted Polymer Toward a High Specific Adsorbent by Using Metal as Assembled Pivot

This article presents an original work aimed at rationally designing molecularly imprinted polymer (MIP) toward a high specific adsorbent. Assembling with cobalt as the pivot, the MIP was prepared by coordinating polymerizable monomers around an inducible template. The use of pivot obviously plays a positive role on increasing the specificity of MIP, so as to adsorb more for the template and less for its analogue. Related studies indicate that these may be a result of increasing specific interaction, which makes the MIP capable of recognizing the imprint species. Further information from thermodynamic analysis reveals that the increasing specific interaction, in logic, can be due to a higher fidelity of imprint, which specifically allures the template to bind.     

Temperature/Light Dual‐Responsive Inclusion Complexes of α‐Cyclodextrins and Azobenzene‐Containing Polymers

Three kinds of photoresponsive copolymers with azobenzene side chains were synthesized by radical polymerization of N‐4‐phenylazophenylacrylamide (PAPA) with N‐isopropylacrylamide (NIPAM), N,N‐diethylacrylamide (DEAM) or N,N‐dimethylacrylamide (DMAM) respectively. Their structures were characterized by FT‐IR, ¹H‐NMR and UV/Vis spectroscopy. Their reversible photoresponses were studied with or without α‐cyclodextrin (α‐CD), which showed that both the copolymers and their inclusion complexes with α‐CD underwent rapid photoisomerization. The lower critical solution temperature (LCST) of the copolymers and their inclusion complexes with α‐CD were investigated by cloud point measurement, which showed that the LCST of three kinds of copolymers increased largely after adding α‐CD. After UV irradiation on the solutions of copolymers and their inclusion complexes, the LCST of the copolymers increased slightly with the absence of α‐CD, while decreased largely with the presence of α‐CD. Furthermore, the LCST reverted to its originality after visible light irradiation. This change of LCST could be reversibly controlled by UV and visible light irradiation alternately. In particular, in the copolymer of PAPA and DMAM, the reversible water solubility of the inclusion complexes could be triggered by alternating UV and visible light irradiation.     

Index Abstracts

Abstract

Calorimetric titrations have been performed in anhydrous acetonitrile at 25°C to give the complex stability constants (K _s) and the thermodynamic parameters (ΔGΔ, ΔHΔ and ΔSΔ) for the complexation of light lanthanoid(III) nitrates (La-Gd) with N-benzylaza-21-crown-7 3. Data analyses, assuming 1:1 stoichiometry, were successfully applied to all light lanthanoid-azacrown ether combinations employed. Using the present and previous data on 15- to 21- membered N-benzylazacrown ethers 1–3, the effect of ring size upon complexation behavior was discussed comparatively and globally from the thermodynamic point of view. The complexation behaviors are analyzed in terms of the size-fit concept, N-substituent coordination numbers, and lanthanoid's surface charge density. Thermodynamically the complexation of light lanthanoids with azacrown ethers is enthalpy-driven, while the cation selectivity is generally entropy-driven in acetonitrile.     

Crystal Structure Investigations of Inclusion Complexes Between β-cyclodextrin and Alkyl(aqua)cobaloximes (Alkyl=Butyl,Hexyl and Cyclohexyl)

The crystal and molecular structures of alkylcobaloxime/ g -cyclodextrin ( g -CD) inclusion complexes: butyl(aqua)cobaloxime/ g -CD ( 1 ). hexyl(aqua)cobaloxime/ g -CD ( 2 ) and cyclohexyl(aqua)cobaloxime/ g -CD ( 3 ) were determined by X-ray diffraction analyses. Crystal data for 1 14H 2 O: P 2 1 2 1 2 1 , a =15.1335(3), b =18.9630(2), c =28.1545(5) Å, Z =4; 2 12H 2 O: P 2 1 2 1 2 1 , a =15.1135(4), b =19.1477(5), c =28.2715(7) Å, Z =4; 3 10H 2 O: P 2 1 2 1 2 1 , a =15.6898(2), b =16.9094(2), c =28.9762(2) Å, Z =4. The structural and conformational comparisons for the three g -CD inclusion complexes with their guest molecules as well as other CD inclusion analogs are discussed.     

Highly sensitive lable-free electrochemical aptasensor for thrombin detection with cobalt hexacyanoferrate as the electrochemical probe

A highly sensitive label-free electrochemical aptasensor has been constructed for the electrochemical detection of thrombin (TB), where two layers of cobalt hexacyanoferrate (CoHCF) redox probes sandwiched with carbon nanotubes–Nafion were directly immobilized on the electrode surface by electrodeposition. Through the strong interaction between CN^? (CoHCF) and gold nanoparticles (GNPs), GNPs were assembled on the CoHCF-modified electrode for the immobilization of thiolated thrombin aptamers (TBA). In the presence of target TB, TBA on the electrode surface could catch TB to form TBA–TB complex, which made a barrier for the electron transfer, resulting in a greater decrease in CoHCF redox probe signals. Thus, the proposed aptasensor showed a high sensitivity and a much wider linearity to TB in the range of 1.0 pg/mL?～?1.0 μg/mL with a detection limit of 0.28 pg/mL.     

Visible‐Light‐Active Elemental Photocatalysts

Seeking visible‐light‐active photocatalysts for efficient solar‐energy conversion has become an intensifying endeavor worldwide. In this concept paper, general requirements for finding new visible‐light‐active photocatalysts are briefly introduced, and recent progress in exploring elemental photocatalysts for clean‐energy generation and environmental remediation are reviewed. Finally, opportunities and challenges facing elemental photocatalysts are discussed.