Inverse Microemulsion Research Articles

Clay Minerals/TiO2 Composites—Characterization and Application in Photocatalytic Degradation of Water Pollutants

TiO2 used for photocatalytic water purification is most active in the form of nanoparticles (NP), but their use is fraught with difficulties in separation from solution or/and a tendency to agglomerate. The novel materials designed in this work circumvent these problems by immobilizing TiO2 NPs on the surface of exfoliated clay minerals. A series of TiO2/clay mineral composites were obtained using five different clay components: the Na-, CTA-, or H-form of montmorillonite (Mt) and Na- or CTA-form of laponite (Lap). The TiO2 component was prepared using the inverse microemulsion method. The composites were characterized with X-ray diffraction, scanning/transmission electron microscopy/energy dispersive X-ray spectroscopy, FTIR spectroscopy, thermal analysis, and N2 adsorption–desorption isotherms. It was shown that upon composite synthesis, the Mt interlayer became filled by a mixture of CTA+ and hydronium ions, regardless of the nature of the parent clay, while the structure of Lap underwent partial destruction. The composites displayed high specific surface area and uniform mesoporosity determined by the size of the TiO2 nanoparticles. The best textural parameters were shown by composites containing clay components whose structure was partially destroyed; for instance, Ti/CTA-Lap had a specific surface area of 420 m2g−1 and a pore volume of 0.653 cm3g−1. The materials were tested in the photodegradation of methyl orange and humic acid upon UV irradiation. The photocatalytic activity could be correlated with the development of textural properties. In both reactions, the performance of the most photoactive composites surpassed that of the reference commercial P25 titania.

Influence of the Interaction of Nickel and Copper with Ceria on Ethanol Steam Reforming over Ni-Cu-CeO2 Catalysts

Catalysts of nickel-ceria, nickel-copper-ceria, and copper-ceria were explored with respect to their properties for hydrogen production through ethanol steam reforming (ESR). They were prepared by coprecipitation of the components within inverse microemulsions to achieve intimate contact between them, and the catalysts were characterized by N2 adsorption measurements, XRD, Raman spectroscopy, TPR, and XPS. The catalysts were tested for the ESR reaction, and they were regenerated with oxygen when significant deactivation took place, as occurred for the copper-containing systems. In contrast, the nickel–ceria catalyst exhibits a high activity and stability despite the formation of an important amount of carbon deposits during the course of the ESR test. The presence of nickel sites, which strongly interact with the ceria support, and which are affected by the presence of copper, and the limitation of copper for C-C bond breaking are invoked to explain the results obtained on the whole.

Cu and Fe modified Cerium and Zirconium Oxides for the Oxidation of Cyclohexane to KA Oil

AbstractCe and Zr oxides have been tested in the oxidation of cyclohexane to KA oil because of the possibility to tune their crystal structure and redox properties by introducing defects, and of modifying their mechanical and thermal stability. The redox properties of the two oxides, prepared by the inverse microemulsion technique, have been tuned by homogeneously including Cu or Fe (10 % molar) into their structures. These modifications led to very different behaviours in terms of both KA oil productivity and K/A ratios, especially upon undergoing reduction treatment, being the reduced Cu‐modified CeO2 oxide the most active catalyst, able to produce 2.2 mmol of KA oil after 5 hours with 93.2 % selectivity (K/A 2.6). The materials obtained have been characterized by solid state analytical techniques to study their structure, morphologies as well as their bulk and surface chemistry (STEM/EDX, BET, XRD, XPS).

TiO2 Nanoparticles with Adjustable Phase Composition Prepared by an Inverse Microemulsion Method: Physicochemical Characterization and Photocatalytic Properties.

Titania nanoparticles (NPs) find wide application in photocatalysis, photovoltaics, gas sensing, lithium batteries, etc. One of the most important synthetic challenges is maintaining control over the polymorph composition of the prepared nanomaterial. In the present work, TiO2 NPs corresponding to anatase, rutile, or an anatase/rutile/brookite mixture were obtained at 80 °C by an inverse microemulsion method in a ternary system of water/cetyltrimethylammonium bromide/1-hexanol in a weight ratio of 17:28:55. The only synthesis variables were the preparation of the aqueous component and the nature of the Ti precursor (Ti(IV) ethoxide, isopropoxide, butoxide, or chloride). The materials were characterized with X-ray diffraction, scanning/transmission electron microscopy, N2 adsorption-desorption isotherms, FTIR and Raman vibrational spectroscopies, and diffuse reflectance spectroscopy. The synthesis products differed significantly not only in phase composition, but also in crystallinity, textural properties, and adsorption properties towards water. All TiO2 NPs were active in the photocatalytic decomposition of rhodamine B, a model dye pollutant of wastewater streams. The mixed-phase anatase/rutile/brookite nanopowders obtained from alkoxy precursors showed the best photocatalytic performance, comparable to or better than the P25 reference. The exceptionally high photoactivity was attributed to the advantageous electronic effects known to accompany multiphase titania composition, namely high specific surface area and strong surface hydration. Among the single-phase materials, anatase samples showed better photoactivity than rutile ones, and this effect was associated, primarily, with the much higher specific surface area of anatase photocatalysts.

Temperature-sensitive polymer grafted with nano-SiO2 improves sealing and inhibition performance of shale water-based drilling fluid

Drilling fluid loss is an important factor restricting oil and gas production. The development of pores and micro-fractures in shale formations is the main cause of drilling fluid loss. In this study, silane coupling agent modified nano-SiO2 was used as the rigid core, and N-isopropylacrylamide and 2-hydroxyethyl methacrylate were used as the flexible outer shell. The temperature-sensitive blocking agent PKSHN was synthesized by inverse microemulsion polymerization method. PKSHN was analyzed and tested through Fourier transform infrared spectroscopy, simultaneous thermal analysis, transmission electron microscopy, dynamic laser scattering and other methods. The results show that PKSHN can achieve a hydrophilic/hydrophobic transition under the response temperature, with a median particle size of 189.35 nm, which can form a hydrophobic layer on the shale surface and reduce fluid intrusion into the shale formation. This study tested the performance of three drilling fluids with different densities by adjusting the amount of weighting agent. The results showed that the high-temperature and high-pressure filter losses of the three different densities of drilling fluids were all less than 10 mL. The addition of PKSHN can effectively reduce fluid loss. The rolling recovery experiment and linear expansion experiment show that after aging for 16 h at 150 °C, the rolling recovery rate is above 90 % and the linear expansion rate is below 7 %, indicating that the addition of PKSHN can effectively control the hydration expansion of shale.

Accelerated hydrolysis and degradation of polylactide nanocomposites using loaded silica nanocarriers

Polylactide (PLA) stands as a prominent commodity biodegradable polymer, yet its inherent slow biodegradation under certain conditions has been a persistent challenge. This study introduces a general approach for enhancing the biodegradation of PLA by employing silica nanoparticles (SiNPs) loaded with diverse cargoes. The SiNPs with diameters of ca. 100 nm are synthesized through a sol–gel process in an inverse microemulsion, enabling in situ loading with functional cargoes such as poly(acrylic acid), lignosulfonate, and chitosan. Surface grafting with PLA (PLA-grafted SiNPs) serves to prevent aggregation, thereby enhancing the dispersion of nanoparticles within the PLA matrix and improving composite properties preventing depletion. Lignin-loaded SiNPs demonstrate the capability to block UV light and enhance antioxidant activity in the composite compared to neat PLA. Notably, SiNPs loaded with poly(acrylic acid) and chitosan exhibit the capacity to accelerate PLA hydrolysis in aqueous environments, while lignin as cargo results in faster composting with an increased weight loss of ca. 20 wt% compared to neat PLA at only 1 wt% loading of SiNPs. This research outlines a versatile strategy utilizing SiNPs to address the slow biodegradation profile of PLA, offering valuable insights and a promising avenue for advancing the environmental sustainability of degradable polyester-based materials in diverse applications.

Recovery of Chlorosilane Residual Liquid to Prepare Nano-Silica via the Reverse Micro-Emulsion Process.

In this paper, nano-silica particles were prepared from chlorosilane residue liquid using an inverse micro-emulsions system formed from octylphenyl polyoxyethylene ether (TX-100)/n-hexanol/cyclohexane/ammonia. The influence of different reaction conditions on the morphology, particle size, and dispersion of nano-silica particles was investigated via single-factor analysis. When the concentration of chlorosilane residue liquid (0.08 mol/L), hydrophile-lipophilic-balance (HLB) values (10.50), and the concentration of ammonia (0.58 mol/L) were under suitable conditions, the nano-silica particles had a more uniform morphology, smaller particle size, and better dispersion, while the size of the nano-silica particles gradually increased with the increase in the molar ratio of water to surfactant (ω). The prepared nano-silica was characterized through XRD, FT-IR, N2 adsorption/desorption experiments, and TG-DSC analysis. The results showed that the prepared nano-silica was amorphous mesoporous silica, and that the BET specific surface area was 850.5 m2/g. It also had good thermal stability. When the temperature exceeded 1140 °C, the nano-silica underwent a phase transition from an amorphous form to crystalline. This method not only promoted the sustainable development of the polysilicon industry, it also provided new ideas for the protection of the ecological environment, the preparation of environmental functional materials, and the recycling of resources and energy.

Superhydrophobic fluorescent micro-/nano-composites from carbon dots encapsulated in CaCO3-SiO2

ABSTRACT In this paper, polyamine-functionalized carbon dots (CDs) were synthesized by means of low temperature (<100°C) carbonization of citric acid at the presence of polyethylenimine (PEI), resulting spherical calcium carbonate micro-particles from inverse micro-emulsion system. Nanoscaled spherical silicas were prepared by Stöber method via deposition on the surface of micron calcium carbonate. Scanning- and transmission-electron microscopic analysis confirmed a micro-/nano-complex structure, enabling the composite material coating possessed coarser surface similar to those of ‘lotus leaf’. After modification with 1 H, 1 H, 2 H, 2 H-perfluorodecanethiol, both good super hydrophobicity and good fluorescent performance were confirmed by the water contact angle of 154.1°±1.5°, their surface-free energy, and fluorescence quantum yield of 14.1%, which provides an inexpensive and easy way to fabricate superhydrophobic material with fluorescence characteristics and promotes high value application of inorganic materials.

Preparation of a Durable CuO/ZnO/CeO2/ZrO2 Catalyst on an SiC Support by an Inverse Microemulsion/Precipitation Method for Methanol Steam Reforming

AbstractDurable CuO/ZnO/CeO2/ZrO2 catalyst on SiC support for methanol steam reforming (MSR) was prepared by the combination of inverse microemulsion method and precipitation method which is termed as inverse microemulsion/precipitation method. The presence of Ce−O−Zr solid solution facilitated the production of oxygen vacancies and Ce3+ species in the prepared CuO/ZnO/CeO2/ZrO2 catalyst. Owing to the unique tiny reaction pool and the addition of precipitant for inverse microemulsion/precipitation method, the particle size of the prepared catalyst was principally between 2 and 6 nm, with an average size of 3.66 nm. Besides, the small particle size and the highly dispersed of Cu species boosted the reduction performance of the catalyst, enabling the reduction temperature to be only 201 °C. The methanol conversion of the reduced catalyst was still reached 98.8 % after 150 h, considerably higher than that of solution combustion method (70 %), without carbon deposition and pronounced sintering after MSR reaction.

Strongly luminescent and highly stable CsPbBr3/Cs4PbBr6 core/shell nanocrystals and their ultrafast carrier dynamics

All-inorganic lead halide perovskites nanocrystals (NCs) have been demonstrated to be promising candidates for optoelectronic devices, but preparing perovskite NCs with high photoluminescence quantum yields (PLQYs) and excellent stability has been a challenge. In this work, CsPbBr3/Cs4PbBr6 core/shell NCs with a PLQYs of 87.23% and long-term stability in ambient environments was prepared by room temperature inverse microemulsion method. The excellent stability of the sample was attributed to the protection of Cs4PbBr6, and higher PLQYs could be owing to the passivation effect of the core/shell structure. To illustrate the distribution of photogenerated carrier in the core/shell structure, a confined excitons model was proposed based on time-resolved PL and temperature dependent PL measurements. Femtosecond time-resolved transient absorption spectra measurements were performed upon different excitation wavelength to unveil the photogenerated carrier dynamics in core/shell NCs. Upon 300 nm excitation, a carrier transfer process with the time of 3.18 ps from shell to core layer was observed. Furthermore, both two- and three-photon absorption PL was discovered in core/shell NCs, further verifying the carrier transfer process.

Synthesis and characterization of PNM@IAM core-shell microgels through inverse emulsion polymerization and its application for heavy metal ions capture

In this study, thermo and pH-sensitive multifunctional poly (N-isopropylacrylamide-co- N,N’-methylenebisacrylamide, Poly(NIPAAm-co-MBA) - (N-4-amino-2-methylene-4-oxobutanoic acid, IAM) named as (PNM@IAM) core-shell microgels are synthesized by inverse microemulsion polymerization technique using two monomers, N-isopropylacrylamide (NIPAAm) and N-4-amino-2-methylene-4-oxobutanoic acid (IAM). The formation of the microgels are confirmed by 1H nuclear magnetic resonance (1H NMR) and attenuated total reflection fourier transform infrared (ATR-FTIR) spectra. The light transmittance study shows that the microgels prepared at different concentrations and pHs exhibit different physical properties. The phase transition temperature is increased with the addition of IAM. Dynamic light scattering (DLS) analysis reveals that the swelling of the microgels at basic environment is due to the deprotonation of the weak acid groups in IAM. The metal ion chelating test shows that the core-shell PNM@IAM could effectively absorb metal ions in highly basic environment. The absorption and release of heavy metal ions from aqueous solution could be controlled by adjusting the pH of the reaction environment.

Preparation and performance of graphene oxide-polyacrylamide based nanoscale microsphere emulsion for profile control

A new kind of in-depth profile control and displacement graphene oxide-polyacrylamide (GO-PAM) based nanoscale microsphere emulsion for enhancing oil recovery was designed by the inverse microemulsion polymerization technology, which simultaneously plays the multifunction roles of plugging pore throat, reducing water-oil interfacial tension and oil viscosity benefiting from the synergistic effect of nanoscale microsphere and GO sheets. The emulsion shows superior suspension properties, thermal stability, hydration swelling, and the excellent emulsifying ability for crude oil. The average particle size of PAM microspheres is about 40 nm, and the size of GO sheets is about 1–10 µm. Only 0.1% dispersion of GO-PAM emulsion reduces the water-oil interfacial tension by 63%, and reduces the viscosity of thick oil by 10%. And with increasing emulsion dosage to 5%, the viscosity can be reduced by more than 50%. For low permeability simulated cores, the plugging efficiency of the GO-PAM emulsion system increases from 80% to 88% compared with PAM emulsion. The microscopic oil displacement experiment shows that our designed emulsion enhanced oil recovery by 6–7%. The GO-PAM composite microsphere emulsion is expected to be a competitive candidate for in-depth profile control and heavy crude recovery.

Stability mechanism of controlled acid-resistant hydrophobic polymer nanospheres on CO2 foam

CO2 foam was an effective way to regulate CO2 mobility and control the gas breakthrough during the process of CO2 flooding. The poor stability of foam-phase restricted the enhanced oil recovery (EOR) ability of CO2 foam flooding, especially under the harsh reservoir conditions and the challenges are yet to be solved. As such, current work hypotheses that by applying the polymer nanosphere as the additive can extend the foam rupture to increase the foam-phase stability. The acid-resistant hydrophobic polymer nanosphere P(AM-AA-ARM-C16DMAAC) was prepared by the inverse microemulsion polymerization method, which used ARM and C16DMAAC as acid-resistant monomer and hydrophobic monomer, respectively. Then, the CO2 foam reinforced by anionic surfactant AOS and P(AM-AA-ARM-C16DMAAC) was developed, and the stability was compared with conventional foam system using Warning Blender method and high temperature and high pressure electromagnetic coupling agitator. Furthermore, the foam aging rules were investigated via the multiple light scattering method and double-layer glass model to further understand the CO2 foam stability mechanism of synthesized acid-resistant hydrophobic polymer nanospheres. The results demonstrated that P(AM-AA-ARM-C16DMAAC) had good swelling performance under acid environment. With the consistency of 0.2% AOS and 0.15% P(AM-AA-ARM-C16DMAAC), the CO2 foam showed the highest foam stability. The dynamic variations in the film thickness of the foam were characterized quantitatively. The prolonged liquid drainage was attributed to the foam liquid film maintained by released water and the liquid film ‘skeleton’ formed by polymer nanospheres. In addition, the formula of acid-resistant hydrophobic polymer nanospheres P(AM-AA-ARM-C16DMAAC) is adjustable under different environmental conditions. After deformation of the foam system, the polymer nanospheres could also act as plugging agent in the formation.

Electrochemiluminescence drug detection with nanoparticle-encapsulated luminophore on screen-printed electrodes

The unprecedented demand for point-of-care testing devices has intensified research interests in developing miniature and cost-effective electroanalytical devices such as electrochemiluminescence (ECL) sensors. Here, we report a simple-structured and disposable ECL sensor platform for drug sensing applications. Our ECL sensor platform consists of screen-printed electrodes using an in-house formulated graphite-based ink, fabricated on flexible polyimide substrates. Silica (SiO2) nanoparticles with sizes of ∼100 nm are synthesized via an inverse microemulsion method, which encapsulates the ECL luminophore tris(2,2′-bipyridyl)ruthenium (II) chloride (Ru(bpy)3Cl2) in situ. The resulting Ru(bpy)32+@SiO2 nanocomposite helps to immobilize the ECL luminophore on the porous surface of screen-printed electrodes. The interface effect introduced by nanoparticles also enhances the ECL efficiency of the resultant sensor significantly by 33% (defined as thearbitrary unit per number of luminophores). The optimized flexible sensor is used for an ECL-based assay of a local anesthetic lidocaine and achieves a wide response range (0 −3.69 mM) and a respectable limit of detection (2.6 μM, S/N ≥ 3). We demonstrate a combination of nanotechnology with readily-available technology in designing scalable, low-cost, and miniature sensor platforms with excellent analytical performance. It serves as a firm foundation for developing point-of-care/in-field testing and wearable sensors for illicit drug detection, water and food security assessment, among other biosensing applications.

Composites of Montmorillonite and Titania Nanoparticles Prepared by Inverse Microemulsion Method: Physico-Chemical Characterization.

TiO2/montmorillonite composites were synthesized using inverse micellar route for the preparation of titania nanoparticles (4-6 nm diameter) in 1-hexanol and for the dispersion of one of the clay components. Two series of composites were obtained: one derived from cetyltrimethylammonium organomontmorillonite (CTA-Mt), exfoliated in 1-hexanol, and the other from sodium form of montmorillonite (Na-Mt) dispersed by formation of an inverse microemulsion in 1-hexanol. The TiO2 content ranged from 16 to 64 wt.%. The composites were characterized with X-ray diffraction, scanning/transmission electron microscopy/energy dispersive X-ray spectroscopy, thermal analysis, and N2 adsorption-desorption isotherms. The Na-Mt-derived component was shown to undergo transformation to CTA-Mt, as indicated by basal spacing of 17.5 nm, due to the interaction with the CTABr surfactant in inverse microemulsion. It was also better dispersed and intermixed with TiO2 nanoparticles. As a result, the TiO2/Na-Mt series displayed superior textural properties, with specific surface area up to 256 m2g-1 and pore volume up to 0.247 cm3g-1 compared with 208 m2g-1 and 0.231 cm3g-1, respectively, for the TiO2/CTA-Mt counterpart. Members of both series were uniformly mesoporous, with the dominant pore size around 5 nm, i.e., comparable with the dimensions of titania nanoparticles. The advantage of the adopted synthesis method is discussed in the context of other preparative procedures used for manufacturing of titania-clay composites.

Multifunctional Low-Generation Dendrimer Nanogels as an Emerging Probe for Tumor-Specific CT/MR Dual-Modal Imaging.

The development of nanoprobes that have amplified enhanced permeability and retention (EPR) effect is crucial for their precise cancer diagnosis performance. Here, we present the development of functional dendrimer-based nanogels (DNGs) with the generation three primary amine-terminated poly(amidoamine) (PAMAM) dendrimers (G3·NH2) cross-linked by N,N'-bis(acryloyl) cystamine (BAC). The DNGs were prepared through a Michael addition reaction between G3·NH2 dendrimers and BAC via an inverse microemulsion method and entrapped with gold nanoparticles (Au NPs) to form Au-DNGs. The Au-DNGs were sequentially modified with diethylenetriamine penta-acetic acid (DTPA)-gadolinium (Gd) complex, poly(ethylene glycol) (PEG)-linked arginine-glycine-aspartic (RGD) peptide, and 1,3-propanesultone (1,3-PS). The formed multifunctional RGD-Gd@Au-DNGs-PS (R-G@ADP) possessing an average diameter of 122 nm are colloidally stable and display a high X-ray attenuation coefficient, excellent r1 relaxivity (9.13 mM-1 s-1), desired protein resistance rendered by the zwitterionic modification, and cytocompatibility. With the targeting specificity mediated by RGD and the much better tumor penetration capability than the counterpart material of single dendrimer-entrapped Au NPs, the developed multifunctional R-G@ADP enable targeted and enhanced computed tomography (CT)/magnetic resonance (MR) dual-modal imaging of a pancreatic tumor model in vivo. The current work demonstrates a unique design of targeted and zwitterionic DNGs with prolonged blood circulation time as an emerging nanoprobe for specific tumor CT/MR imaging through amplified passive EPR effect.

Inflammatory Cell-Inspired Cascade Nanozyme Induces Intracellular Radical Storm for Enhanced Anticancer Therapy.

Manipulating intracellular levels of reactive oxygen and nitrogen species (RONS) is of great potential for cancer treatment. Inspired by the natural mechanism of a radical storm in inflammatory cells via activated and regulatable biocatalysis, the authors herein report a self-powered nanozyme that can enable RONS production in tumor cells via cascade reactions. The nanozymes are constructed via glucose oxidase (GOx)-templated inverse microemulsion polymerization from acrylamide, arginine-acrylamide, ferrocene-acrylate, and N,N'-bis(acryloyl)cystamine, followed by surface coating with hyaluronic acid. After targeted delivery into cancer cells, the nanozymes are dissociated by intracellular glutathioneto release GOx, which decomposed glucose to generate gluconic acid and H2 O2 . Under such acidified conditions, H2 O2 efficiently oxidized pendant arginine residues to produce nitric oxide , transformed into a highly toxic hydroxyl radical and superoxide anion via ferrocene-mediated Fenton reaction and Haber-Weiss cycle, and simultaneously generated peroxynitrite anion via reaction between NO and ·O2 - , thus provoking the RONS radical storm to effectively eradicate A549 tumor cells both in vitro and in vivo. This nature-inspired enzyme-chemical dynamic therapy may provide a promising modality for anti-cancer treatment.

The treatment of hepatocellular carcinoma with SP94 modified asymmetrical bilayer lipid-encapsulated Cu(DDC)2 nanoparticles facilitating Cu accumulation in the tumor

Background Copper diethyldithiocarbamate (Cu(DDC)2) has been demonstrated to possess excellent antitumor activity. However, the extremely poor water solubility of Cu(DDC)2 bring difficulty for its formulation research. In this study, we aim to develop a novel nanocarrier for Cu(DDC)2 delivery to overcome this obstacle and enhance antitumor activity. Methods The SP94 modified asymmetrical bilayer lipid-encapsulated Cu(DDC)2 nanoparticles (DCDP) was established by combining the method of inverse microemulsion aggregation and thin-film dispersion. In vitro cellular assays and in vivo tumor-xenograft experiments were conducted to evaluate the tumor chemotherapeutic effect of DCDP. And the vital role of copper ions played in DSF or DDC (DSF/DDC)-based cancer chemotherapy was also explored. Results DCDP with an encapsulation efficiency (EE%) of 74.0% were successfully prepared. SP94 modification facilitated cellular intake for DCDP, and promoted apoptosis to repress tumor cell proliferation (IC50, 200 nM). And DCDP effectively inhibited tumor growth with a high tumor inhibition rate of 74.84%. Furthermore, Cu(DDC)2 was found to facilitate the copper ion accumulation in tumor tissues, which is beneficial to therapy with high potency. Conclusion DCDP exhibited high-efficient tumor chemotherapeutic efficacy and provided a novel strategy for investigating the anticancer mechanism of Cu(DDC)2.

Synthesis and Rheological Properties of Polyacrylamide Nanospheres and SiO2/PAM Composite Nanospheres

AbstractPolyacrylamide nanospheres are a kind of polymer material that can improve the development effect of oilfield water flooding and realize reservoir stimulation. However, due to its good water absorption, the strength cannot well meet the needs of practical production, and is forced to be limited to application on oil displacement. Therefore, in this paper, SiO2/PAM composite nanospheres were synthesized by the inverse microemulsion method to meet the needs of profile control and water shutoff in oilfields. The structure, oil displacement effect and rheological properties of polyacrylamide nanospheres and SiO2/PAM composite nanospheres were comparatively studied. The results show that both nanospheres are viscoelastic nanospheres. Since the elastic response is greater than the viscous response in SiO2/PAM composite nanospheres, and the polymer nanospheres do the opposite, there are significant differences in various rheological properties, such as variation of apparent viscosity with shear rate, creep recovery characteristics, viscoelasticity etc. This work provides a basis for the practical application of SiO2/PAM composite nanospheres in oilfields.

Preparation and Properties of Temperature-Sensitive P(NIPAM-AM) Nano–Microspheres in Enhanced Oil Recovery

As a new kind of water plugging and profile control agents, the polyacrylamide nano–microspheres have been experimentally applied and achieved satisfactory preliminary results in enhanced oil recovery, especially for low-permeability reservoirs. However, the larger swollen particle size and excessive hydrophilicity limit the effect at the oil–water interface. In order to further improve their profile control and flooding effect, the temperature-sensitive poly(N-isopropylacrylamide-acrylamide) nano–microspheres are prepared by inverse microemulsion polymerization. Based on the principle of conformation transition of PNIPAM triggered by simulated high temperature in reservoirs, the particle size and hydrophilicity of the microspheres are reduced, making it easier to reach the oil–water interface, reduce the oil–water interface tension, and enhance the structural disjoining pressure, which improves the spontaneous emulsification effect and removal effect of residual oil on rocks. The swelling properties, hydrophilicity, interfacial activity, and oil displacement properties of the nano–microspheres were also analyzed. The results show that the swelling ratio of the copolymerized nano–microspheres decreases to 1.5. At simulated reservoir temperature (65 °C), the water contact angle of copolymerized gel increases from 43 to 86°, indicating that its hydrophilicity decreases and shows a clear tendency to migrate to the water–oil interface. At 65 °C, 0.1 wt % PNIPAM-based microsphere emulsion (N3) reduces the oil–water interfacial tension from 17.8 to 0.9 mN m–1. The microscopic oil displacement experiment shows that the recovery efficiency of our designed temperature-sensitive nano–microspheres emulsion is increased by 7%, which is higher than that of the PAM polymer nanosphere. The PNIPAM-based temperature-sensitive nano–microspheres that can function at the oil–water interface have a potential development prospect in low-permeability reservoirs.