Films of polystyrene-polybutadiene-polystyrene triblock copolymer were cast from toluene solutions using the technique of ’roll-casting’, which leads to microphase separation of the block copolymer into globally oriented structures that are often termed ’single crystals’. The thermal expansion of unannealed films was found to be dominated by molecular stresses resulting from the casting process. The angular dependence of the thermal expansion coefficient of annealed films, which were free of any preferred molecular orientation, was governed by the supramolecular structure and was found to be in good agreement with theoretical predictions related to traditional composite materials.