Jose Esteban Valentini

Adsorption of ethylene oxide/propylene oxide/ethylene oxide triblock copolymers at the air/water interface

Abstract Capillary wave and Wilhelmy plate techniques have been used to study the adsorption kinetics of ethylene/propylene/ethylene oxide triblock copolymers (F127 and F68). By using the simple test that we proposed earlier, we have established that adsorption concentration Γ(t) of these copolymers increases with t 1 2 , after the formation of fresh interface. This observation suggests that the adsorption of these copolymers is diffusion-limited. The stress relaxation experiments performed on equilibrium surfaces of these copolymers show that the surface tension response to a step-type surface area change can be interpreted by the diffusion-controlled matter-exchange mechanism, even though these polymers are polydispersed. The high-frequency surface dilational modulus ϵ0 and the average diffusive relaxation time constant τ d are obtained as functions of polymer concentration.