The dynamics of lamellar re-orientation in free-standing diblock copolymer films: flipping the morphology from edge-on to flat-on

Many exquisite structures formed by diblock copolymers have been studied rigorously over the past two decades. Using a symmetric polystyrene-poly(methyl methacrylate) diblock copolymer, we prepare thin films on a substrate which form lamellae oriented perpendicular to the film interfaces. These ``edge-on'' samples are subsequently transferred, by floating onto water, to produce free-standing films with a symmetric boundary condition. Upon annealing these free-standing films, the lamellae switch from edge-on, to ``flat-on'' such that the domains are oriented parallel to the interface. Using atomic force microscopy, we study the dynamics of pattern formation as lamellae flip from the edge-on to flat-on morphology.