We report studies of the self-assembly of amphiphilic diblock copolymers, polystyrene-b-poly(alkyl acrylate) at the air water interface. Using the Langmuir film balance, unusual multiple plateau/inflection transitions in surface pressure / molecular area isotherms have been observed. Transmission electron microscopy of the corresponding Langmuir-Blodgett films has shown the presence of surface micelles. We have studied the effect of a range of different alkyl blocks on the isotherms. Possible mechanisms for the multiple inflections observed in the isotherms are discussed.