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.