Join us for a seminar on "Seeing the order-order phase transition between double diamond and double gyroid structures in block copolymers" presented by Edwin Thomas, Texas A&M. 

Thomas is known for his development of novel photonic materials and determination of the morphology of block copolymers. He was elected to the National Academy of Engineering and the American Academy of Arts and Sciences in 2009. Thomas became an inaugural fellow of the Materials Society in 2008, a fellow of the American Association for the Advancement of Science in 2003, and a fellow of the American Physical Society in 1986. He received the High Polymer Physics Prize of the American Physical Society in 1991 and the 1985 American Chemical Society’s Creative Polymer Chemist Award.

Abstract:

The order-order phase transition between the tubular network double diamond (DD,Pn3m) and double gyroid (DG, Ia3d) phases occurs in a variety of soft matter systems including water-surfactant liquid crystal phases, and in block copolymers. Various geometrical and topological transformational pathways have been proposed based on limited microscopy and scattering data, but the specific structural features of the morphological evolution at the interface between the co-existing phases have been very challenging to elucidate.

Here we employ slice and view scanning electron microscopy on polystyrene-polydimethylsiloxane diblock copolymers to examine the phase transition zone between the DD and DG structures. 3D tomograms of the transformation zone show how the mesoatoms and loops of each network are cooperatively modified over a narrow (less than one unit cell wide) zone that shows a facile, low energy transformation pathway between the tubular network phases. A key feature of the transformation is the malleability of the tubular network mesoatoms.