Real-time study of graphene's phase transition in polymer matrices.

We present real-time study of pristine graphene sandwiched in a homogeneous polymer matrix and its phase transition where the graphene membrane irreversibly scrolls and folds above the polymer's glass temperature. Tubular structures tend to form by curling up from edge defects of graphene and roll along its surface. A single-layer can also fold into two- or three-layer stacks and the overlapping between layers extends along the membrane surface to enlarge up to micrometer sizes. Further, oxidized graphene does not show such reactivity at even higher temperatures, indicating that the intrinsic thermal instability of pristine graphene in the polymer matrix is the origin of the transition.