Dynamics of amphiphilic diblock copolymers at the air-water interface

Two polyisoprene-polyethyleneoxide diblock copolymers with different block length ratios adsorbed to the water surface were investigated by multiple angle of incidence ellipsometry, evanescent wave light scattering, and surface tension experiments. In a semidilute interfacial regime, the transition from a two-dimensional to a "mushroom" regime, in which polymer chains form loops and tails in the subphase, was discussed. A diffusion mechanism parallel to the interface was probed by evanescent wave dynamic light scattering. At intermediate concentrations, the interfacial diffusion coefficient D-parallel to scales with the surface concentration Gamma, as D-parallel to similar to Gamma(0.77) in agreement with the scaling observed for polymer solutions in a semidilute regime. At relatively high concentrations a decreasing of D-parallel to is discussed in terms of increasing friction due to interactions between polyisoprene chains. (C) 2010 Elsevier Inc. All rights reserved.