Boundary Lubrication Performance of Polyelectrolyte-Surfactant Complexes on Biomimetic Surfaces

Hair care formulations like shampoos and conditioners contain a mixture of surfactants and polyelectrolytes to modify different properties. One important target of conditioners is to leave the hair feeling smooth, by reducing friction. In this study, we use non-equilibrium molecular dynamics simulations to study the lubrication performance of surfactants and polyelectrolytes between model hair surfaces. The systems are modelled using a coarse-grained force field, which reduces the computational cost by more than an order of magnitude compared to atomistic models. We show that both polyelectrolytes and surfactants are able to reduce friction by adsorbing to the sliding surfaces and providing hydrated interfaces where the systems can be easily sheared. For mixtures of oppositely charged polyelectrolytes and surfactants, synergistic behaviour is observed whereby the friction is lower than with either individual component. The simulations provide important insights into the lubrication performance of conditioners, which can be used to design more sustainable formulations.


Erik Weiand, Peter H. Koenig, Francisco Rodriguez-Ropero, Yuri Roiter, Stefano Angioletti-Uberti, Daniele Dini and James P. Ewen