Zhihu Yan

Formation and rheological properties of wormlike micelles by N-hexadecyl-N-methylpiperidinium bromide and sodium salicylate

The formation and properties of wormlike micelles composed of a surface-active surfactant N-hexadecyl-N-methylpiperidinium bromide (C16MDB) and organic salt sodium salicylate (NaSal) at room temperature were studied. Rheological measurements and cryogenic transmission electron microscopy (cryo-TEM) were conducted to study the rheological properties and microstructures of wormlike micelles. Cryo-TEM image confirms the formation of wormlike micelles in aqueous solution. Rheological results show that wormlike micelles indicate linear viscoelasticity and follow the Maxwell model. The Cole–Cole plots agree well with the typical characteristic of the Maxwell model at low and middle frequencies. The contour length, mesh size, and entanglement length of wormlike micelles are estimated from the rheological measurements. In addition, the temperature effect on the rheological properties of wormlike micelles is also studied. Through comparison, the entanglement length and mesh size of wormlike micelles are nearly unchanged, while the contour length shows a sharp decrease tendency with the increase of temperature, indicating that the change of rheological properties with the temperature is due to the contour length change of wormlike micelles.

Thermal and pH dual stimulated wormlike micelle in aqueous N-cetyl-N-methylpyrrolidinium bromide cationic surfactant-aromatic dibasic acid system

Dual-stimulated wormlike micelles regulated by pH and temperature in a surface active ionic liquid system comprising of a cationic surfactant (N-cetyl-N-methylpyrrolidinium bromide (C16MDB)) and an aromatic dibasic acid (pyrocatechol) were investigated. Such a system can be reversibly switched between liquid-like and gel-like states on adjusting the solution pH value. The rheology, light scattering techniques and cryogenic-transmission electron microscopy (cryo-TEM) results show the growth of spherical micelles into long and entangled wormlike micelles was responsible for the changes in flow properties such as high viscosity, shear-thinning behaviour and Maxwell-type dynamic rheology. The nuclear magnetic resonance results reveal the binding capacity of pyrocatechol to C16MDB is proposed as the key factor of the unusual rheological and micellar responses of this pH-stimulated system. In addition, with the increase of temperature, molecular motion of surfactant molecules becomes more active, which endow the property of thermo-stimulated to the surface active ionic liquid system.

Formation of worm-like micelles in mixed N-hexadecyl-N-methylpyrrolidinium bromide-based cationic surfactant and anionic surfactant systems.

Through the descriptive and rheological characterization of worm-like micelles formed by N-hexadecyl-N-methylpyrrolidinium bromide and sodium laurate, the formation and properties of the worm-like micelles were affected by the concentrations of sodium laurate and temperature. Additionally, cryogenic transmission electron microscopy images further validated the formation of worm-like micelles.

Study of the formation and solution properties of worm-like micelles formed using both N-hexadecyl-N-methylpiperidinium bromide-based cationic surfactant and anionic surfactant.

The viscoelastic properties of worm-like micelles formed by mixing the cationic surfactant N-hexadecyl-N-methylpiperidinium bromide (C16MDB) with the anionic surfactant sodium laurate (SL) in aqueous solutions were investigated using rheological measurements. The effects of sodium laurate and temperature on the worm-like micelles and the mechanism of the observed shear thinning phenomenon and pseudoplastic behavior were systematically investigated. Additionally, cryogenic transmission electron microscopy images further ascertained existence of entangled worm-like micelles.

Research on a temporary plugging agent based on polymer gel for reservoir acidification

A temporary plugging agent based on polymer gel was successfully prepared for temporary plugging in acidizing treatment. The gelation time, gel-breaking time, viscosity changes, temporary plugging capacity, and permeability recovery capacity were investigated. Increasing the polymer and cross-linker concentration reduced the gelation time of the polymer gel and temporary plugging agent, but caused difficulties in breaking the temporary plugging agent. Ammonium persulfate (APS) could be the driving force for the differences of gelation time between the polymer gel and temporary plugging agent. Additionally, increasing APS concentration made the temporary plugging agent break easily. Viscosity changes are the most important feature of a temporary plugging agent. According to the viscosity changes, the whole process can be divided into two major stages: the cross-linking reaction stage and the degradation reaction stage. The temporary plugging agent had a good plugging capacity which could effectively plug the high permeability zones. By temporary plugging, the pollution near wellbore was removed without damaging non-target zones. As a result, the permeability of the low permeability zones was greatly improved, and the permeability of the high permeability zones was effectively recovered.

Study of pH-responsive surface active ionic liquids: the formation of spherical and wormlike micelles

A noncovalent bonding method is utilized for forming pH-responsive surface active ionic liquids in mixed N-hexadecyl-N-methylpyrrolidinium bromide-based cationic surfactant (C16MPBr) and potassium phthalic acid (PPA). Rheology, cryogenic-transmission electron microscopy, and dynamic light scattering results revealed that the microstructure transition between spherical micelles and wormlike micelles was the fundamental cause of the pH-sensitive rheological properties. In addition, combined with nuclear magnetic resonance and UV–vis analysis, we found that the structure transition of micelles was attributed to different binding abilities of hydrotropes to C16MPBr as pH varies. It is confirmed that the binding ability of PPA to C16MPBr is strongest. This noncovalent bonding method is not only versatile but also economical for fabricating pH-responsive surface active ionic liquids.