Orientation of grafted polymer chains at the air-water interface studied by PM-IRRAS

Monolayers of polystyrene-polyethylene oxide (PS-PEO) copolymers at the air -water interface have been studied with the Modulation Polarization Infra R ed Spectroscopy technique (PM-IRRAS) to measure the orientation of the PEO chains with respect to the normal to the interface. At surface densities in termediate between the dilute regime and the brush regime, the average tilt angle has been determined: it decreases continuously with the surface dens ity in the monolayer, in good agreement with previous results (M.C. Faure e t al., Macromolecules 32, 8538 (1999)). The further stretching of the molec ules in the brush regime has also been measured. No substantial volume frac tion of PEO crystal domains has been detected in the very dense regime.