Enhanced drag reduction performance by interactions of surfactants and polymers

The interactions of cationic surfactant cetyltrimethyl ammonium chloride (CTAC) and polyacrylamide (PAM) in drag reduction solutions are studied by experiments and simulations. Cryogenic Transmission Electron Microscopy shows that CTAC and PAM form aggregates with interconnected network structures, and the bridge effect from polymers can improve the network structures' density. The associated potential of mean force (PMF) value indicates that surfactant/polymer attractions contribute to the formation of aggregates. Meanwhile, the mechanism of the enhanced drag reduction performance of surfactant/polymer solution is discussed by the extension energy of the aggregate structures. It is found that the interactions of surfactants and polymers help to improve the anti-shear performance of the surfactant micelles. Furthermore, polymers can balance micelles energy distribution, postpone the appearance of energy extreme point, and delay the rupture of micelles. This work fundamentally demonstrates that interactions and strengthened structures of micelle aggregates can intensify drag reduction in surfactant/polymer solutions. (C) 2020 Elsevier Ltd. All rights reserved.