THE ANISOTROPIC THERMAL-EXPANSION OF SINGLE-CRYSTAL TRIBLOCK COPOLYMER FILMS

Films of polystyrene-polybutadiene-polystyrene triblock copolymer were cast from toluene solutions using the technique of 'roll-casting', wh ich leads to microphase separation of the block copolymer into globall y oriented structures that are often termed 'single crystals'. The the rmal expansion of unannealed films was found to be dominated by molecu lar stresses resulting from the casting process. The angular dependenc e of the thermal expansion coefficient of annealed films, which were f ree of any preferred molecular orientation, was governed by the supram olecular structure and was found to be in good agreement with theoreti cal predictions related to traditional composite materials.