Yining Wu

Investigation of Novel Triple-Responsive Wormlike Micelles

Smart wormlike micelles with stimuli-tunable rheological properties may be useful in a variety of applications, such as in molecular devices and sensors. The formation of triplestimuli-responsive systems so far has been a challenging and important issue. In this work, a novel triplestimuli (photo-, pH-, and thermoresponsive) wormlike micelle is constructed with N-cetyl-N-methylmorpholinium bromide and trans-cinnamic acid (CA). The corresponding multiresponsive behaviors of wormlike micellar system were revealed using cryogenic transmission electron microscopy, a rheometer, and 1H NMR. The rheological properties of wormlike micellar system under different temperatures, pH conditions, and UV irradiation times are measured. As confirmed by 1H NMR, chemical structure of a CA molecule can be altered by the multiple stimulation from an exotic environment. We expect it to be a good model for triple-responsive wormlike micelles, which is helpful to understand the mechanism of triple-responsiveness and widen their applications.

Design and Study of a Novel Thermal-Resistant and Shear-Stable Amphoteric Polyacrylamide in High-Salinity Solution

Water-soluble polymers are widely used in oilfields. The rheological behaviors of these polymers in high-salinity solution are very important for stimulation of high-salinity reservoirs. In this work, a novel thermal-resistant and shear-stable amphoteric polyacrylamide (PASD), prepared from acrylamide (AM), sodium styrene sulfonate (SSS), and acryloxyethyl trimethylammonium chloride (DAC) monomers, was prepared by free-radical polymerization in high-salinity solution. The amphoteric polyacrylamide was characterized by Fourier transform infrared (FTIR) spectroscopy, nuclear magnetic resonance spectroscopy (1H NMR), elemental analysis, thermogravimetric analysis (TG), and scanning electron microscopy (SEM). The amphoteric polyacrylamide exhibited excellent salinity tolerance. The slow increase in apparent viscosity of the polymer with increase in salinity was interesting. The amphoteric polyacrylamide showed perfect temperature resistance in high-salinity solution. The viscosity retention reached 38.9% at 120 °C and was restored to 87.8% of its initial viscosity when temperature was decreased to room temperature. The retention ratio of apparent viscosity reached 49.7% at 170 s−1 and could still retain it at 25.8% at 1000 s−1. All these results demonstrated that PASD had excellent thermal-resistance and shear-stability in high-salinity solution. We expect that this work could provide a new strategy to design polymers with excellent salinity-tolerance, thermal-resistance, and shear-stability performances.

The Study of a Novel Nanoparticle-Enhanced Wormlike Micellar System

In this work, a novel nanoparticle-enhanced wormlike micellar system (NEWMS) was proposed based on the typical wormlike micelles composed of cetyltrimethylammonium bromide (CTAB) and sodium salicylate (NaSal). In order to strengthen the structure of wormlike micelles, silica nanoparticles are used to design the novel nanoparticle-enhanced wormlike micelle. The stability and morphologies of silica nanoparticles were studied by dynamic light scattering (DLS) and transmission electron microscopy (TEM) at first. After the formation of NEWMS, the rheological properties were discussed in detail. The zero-shear viscosity of NEWMS increases with the addition of silica nanoparticles. Dynamic oscillatory measurements show the viscoelastic properties of NEWMS. Through comparison with the original wormlike micelles, the entanglement length and mesh size of NEWMS are nearly unchanged, while the contour length increases with the increase of silica concentration. These phenomena confirm the enhanced influence of silica nanoparticles on wormlike micelles. The formation mechanism of NEWMS, especially the interactions between wormlike micelles and nanoparticles, is proposed. This work can deepen the understanding of the novel NEWMS and widen their applications.

Can More Nanoparticles Induce Larger Viscosities of Nanoparticle-Enhanced Wormlike Micellar System (NEWMS)?

There have been many reports about the thickening ability of nanoparticles on the wormlike micelles in the recent years. Through the addition of nanoparticles, the viscosity of wormlike micelles can be increased. There still exists a doubt: can viscosity be increased further by adding more nanoparticles? To answer this issue, in this work, the effects of silica nanoparticles and temperature on the nanoparticles-enhanced wormlike micellar system (NEWMS) were studied. The typical wormlike micelles (wormlike micelles) are prepared by 50 mM cetyltrimethyl ammonium bromide (CTAB) and 60 mM sodium salicylate (NaSal). The rheological results show the increase of viscoelasticity in NEWMS by adding nanoparticles, with the increase of zero-shear viscosity and relaxation time. However, with the further increase of nanoparticles, an interesting phenomenon appears. The zero-shear viscosity and relaxation time reach the maximum and begin to decrease. The results show a slight increasing trend for the contour length of wormlike micelles by adding nanoparticles, while no obvious effect on the entanglement and mesh size. In addition, with the increase of temperature, remarkable reduction of contour length and relaxation time can be observed from the calculation. NEWMS constantly retain better viscoelasticity compared with conventional wormlike micelles without silica nanoparticles. According to the Arrhenius equation, the activation energy Ea shows the same increase trend of NEWMS. Finally, a mechanism is proposed to explain this interesting phenomenon.

A Study on Preparation and Stabilizing Mechanism of Hydrophobic Silica Nanofluids

Nanofluids have increasingly drawn interest in recent years with their various applications in a number of fields. The method for the preparation of stable nanofluids is a key concern for extending the application of nanofluids. This study focuses on the effect of pH, dosage of surfactant (TX-100), and nanofluid concentration on the stability of a silica nanofluid. Particle size and zeta potential are two important factors to consider in evaluating the stability of the silica nanofluid. Results indicate that the stability of the silica nanofluid highly depends on pH, dosage of surfactant (TX-100), and nanofluid concentration. On the basis of these experiments, the best conditions for the preparation of a silica nanofluid are 0.1 wt. % for the concentration of silica nanoparticles and TX-100 and 10 for pH. A transparent and stable silica nanofluid can thus be obtained.

Stability Mechanism of Nitrogen Foam in Porous Media with Silica Nanoparticles Modified by Cationic Surfactants

This work aims at studying the effect of electrostatic interactions between cationic surfactants and silica nanoparticles (NPs) on foam stability in porous media. The physio-chemical property of NPs, the gas-liquid interface properties, the foam flow characteristics, together with the stability under different concentrations of surfactant and NPs were investigated and compared. It was found that the affinity of silica NPs to the surface is tunable by variation of surfactant concentrations. NPs and surfactants as a whole assembling at the surface substantially improve the foam stability in static and dynamic tests. These surfactant-modified NPs accumulate at the bubble surface and remain stable under dilution of brine, providing a barrier effectively preventing coalescence. In addition, foam stability is enhanced since the layer of NPs significantly reduces the mass transfer rate, consequently mitigating the Ostwald ripening.

Investigation of Active-Inactive Material Interdigitated Aggregates Formed by Wormlike Micelles and Cellulose Nanofiber

In this work, a novel active-inactive material interdigitated aggregates (AIMIAs) structure was constructed by self-assembled wormlike micelles (WLMs) and one-dimensional cellulose nanofiber (CNF). The rheological behaviors and microstructures of the AIMIA systems with different CNF concentrations were investigated by rheometer, cryogenic transmission electron microscopy, and environmental scanning electron microscope. Some key parameters, including zero-shear viscosity (η0), relaxing time (τR), and contour length ( L), were calculated to analyze the changes in the properties of different systems. Meanwhile, a proper mechanism describing the interaction between CNF and WLMs was proposed. Through this work, we expect to deepen the understanding of the AIMIAs structure and widen its application.

Study on adsorption characteristic of novel nonionic fluorocarbon surfactant (4-hydroxyethyl ether) (pentadecafluoro-alkyl) amide at coal-water interface

Experimental investigations were carried out to examine the adsorption equilibrium, isotherm, kinetic behaviors of adsorption, and effect on adsorption-desorption of coal-bed methane (CBM) of the nonionic fluorocarbon surfactant (4-hydroxyethyl ether) (pentadecafluoro-alkyl) in the development process of CBM. The results show that the surfactant adsorption pattern is consistent with the Langmuir adsorption law for different rank coals, and the adsorption capacity is increasing from low-rank coal to high-rank coal. The surfactant adsorption process is spontaneous and endothermic, indicating that augmentation of temperature facilitates the adsorption of surfactant. The adsorption densities over electrolytes concentration on the surface of low-rank and medium-rank coal show the same trend; while for high-rank coal, it gives some details about the different trends. Adsorption densities decrease with pH value increasing of bulk solution for all coal samples. Adsorption behavior of surfactant is conducive to accelerating CBM desorption through wettability alteration of a coal surface.

Novel investigation based on cationic modified starch with residual anionic polymer for enhanced oil recovery

ABSTRACT Cationic modified starch polymer (CMSP) is a newly developed green chemical agent designed to reutilize the residual anionic polymer found in reservoirs for enhanced oil recovery (EOR). In this study, a series of experiments were conducted to investigate the phase behavior of the residual anionic polymer, CMSP solution, and the flocculation generated from the mixture in plugging capacity and capability of enhancing oil recovery in heterogeneous reservoirs. The experiment results show that the phase behavior of the residual anionic polymer and CMSP solution could be divided into two parts: rapid flocculation reaction and dispersion reaction. The main mechanisms of the rapid flocculation reaction were charge neutralization and bridging. Based on the above results, an optimal amount of CMSP was chosen for plugging capacity, stability, and EOR study. Plugging tests in both parallel cores and EOR in three-layer heterogeneous square cores illustrate that the injected CMSP slug after polymer flooding can effectively block the high-permeability zone and initiate the remaining oil in middle- to low-permeability zones. The investigation results prove that the CMSP solution, injected after polymer flooding, reduces the pollution of produced fluid and further improves oil recovery. GRAPHICAL ABSTRACT