Characterization of diblock copolymer monolayers at the liquid-air interface by neutron reflectivity and surface tension measurements

Simultaneous measurements of the concentration profile and the free energy of the submerged PS blocks of PDMS-PS diblock copolymers spread as monolayers at the air surface of ethyl benzoate are carried out as a function of surface concentration. A parabolic concentration profile is found to give the best fit to neutron reflectivity curves among the set of two-parameter models examined. The maximum extension h * /R g is comparable to previously reported values obtained from a variety of techniques for similar values of the reduced surface density σ * and indicates some stretching perpendicular to the surface