Wormlike micelles with a unique ladder shape formed by a C22-tailed zwitterionic surfactant bearing a bulky piperazine group

Abstract

Wormlike micelles (WLMs) have been successfully constructed from many different C₂₂-tailed surfactants. Here, we creatively introduced a bulky piperazine group onto a C₂₂-tailed zwitterionic surfactant, N-erucamidopropyl-N,N-piperazine-N-methyl ammonium propanesulfonate (EDPS), and investigated the micellar structure and properties of the EDPS WLMs via molecular dynamics simulation, cryo-TEM and rheological techniques. It was found that 25 mM EDPS increased the zero-shear viscosity to as high as ∼10⁶ mPa s. Furthermore, abnormal rheological behaviors, such as an inflection in the shear thinning region of steady rheology and an abrupt decrease of the shear stress at a critical shear rate, were observed, which was attributed to the unique ladder shape micellar structure. The EDPS WLMs were superior to other C₂₂-tailed surfactants in many aspects, such as a low overlapping concentration, higher viscosity, stable viscosity over the whole pH range, and great temperature and salt (NaCl, CaCl₂ and MgCl₂) tolerance.