Topological Dynamics of Micelles Formed by Geometrically Varied Surfactants

Fabrication and Enzymatic Disorganization of Multiresponse Worm-Like Micelles

How to fabricate multiresponse worm-like micelles (WLMs) and the corresponding green disposal is still challenging. A strategy of fabricating the surfactant-based WLMs that can respond simultaneously to light, heat, and pH was developed by using triple-response sodium (E)-2-(4-(phenyldiazenyl)phenoxy) acetate (AzoNa) and butyrylcholinesterase (BChE)-hydrolyzable palmitoylcholine bromide (PCB). Under the optimal molar ratio of AzoNa to PCB (∼0.5), the PCB-AzoNa WLMs formed with a maximum zero-shear viscosity (η0) value of about 2.1 × 105 mPa·s and an average diameter (D) of 4.1 ± 0.6 nm under conditions of 37 °C and pH 7.4. After irradiated with 365 nm UV light for 80 min, AzoNa underwent the trans-to-cis transition, by which the PCB-AzoNa WLMs was destroyed; however, the PCB-AzoNa WLMs could be reformed upon the irradiation of 455 nm blue light for 18 h or heating at 70 °C for 45 min due to the cis-to-trans isomerization of AzoNa. When pH changed from 7.4 to 2.0, the PCB-AzoNa WLMs was destroyed rapidly because of the conversion of AzoNa to the acid form of AzoH, whereas the PCB-AzoNa WLMs could be reformed after pH was restored to 7.4. The multiple responsiveness of the PCB-AzoNa WLMs was reversible due to the reversible trans-cis isomerization or protonation of AzoNa. Besides, the average D values of light, heat, and pH-regenerated PCB-AzoNa WLMs were 4.2 ± 0.7, 4.0 ± 0.7, and 4.0 ± 0.6 nm, respectively. Finally, the PCB-AzoNa WLMs could be enzymatically disorganized under conditions of 37 °C and pH 7.4 due to the BChE-catalyzed hydrolysis of PCB. We hope that the fabrication and enzymatic disorganization strategies for PCB-based multiresponse WLMs presented here will find potential applications in the formulation of antimicrobial household and personal care products containing PCB and in the green disposal of viscous waste containing PCB.

Performance Evaluation and Formation Mechanism of Viscoelastic Surfactant Fracturing Fluids with Moderate Interfacial Activity Enhanced by Janus-SiO2 Nanoparticles

Nanoparticles (NPs) exhibit great potential to improve various properties of viscoelastic surfactant (VES) fracturing fluids in the development of low-permeability reservoirs. In the present study, the amphiphilic Janus NPs (JANPs) were fabricated via the Pickering emulsion method and employed to construct the novel JA12C (JANPs with dodecyl hydrophobic carbon chains)-assisted VES fracturing fluid (JAVES). The successful fabrication of JANPs was confirmed via Fourier transform infrared spectroscopy (FTIR) measurements and water contact angle tests. The rheology behavior of the VES fracturing fluid incorporating various SiO2 NPs including hydrophilic SiO2 NPs (HLNPs), JA8C (JANPs with octyl hydrophobic carbon chains), and JA12C was systematically investigated. It was revealed that the additional JA12C significantly improved the tolerance and proppant suspension properties. To explore the subsequent oil recovery performance of various gel breaking liquids, the formation wettability and the oil-water interfacial tension (IFT) were studied after the evaluation of breaking properties and formation damage properties of various fracturing fluids. The results suggested that the JAVES gel breaking liquid showed remarkable wettability alternation capability and moderate oil-water IFT reduction ability, which can partially reduce the impact on reservoir permeability. Moreover, the formation mechanism of the JAVES was proposed by molecular dynamics simulations at the molecular level, which was further visually verified via the cryo-TEM images. The improved viscoelasticity of developed the JAVES with moderate interfacial activity is advantageous to enhance subsequent oil recovery.