Topological Defects in Tubular Network Block Copolymers

Materials based on the double gyroid multicontinuous tubular structure can exhibit an array of exotic properties due to the unique 3D network structure. The nature, frequency and potential influence of topological defects present in the interpenetrating gyroid networks on various physical properties is an open question. We examined a polystyrene – polydimethylsiloxane copolymer possessing the double gyroid microdomain morphology in order to identify the types of topological defects present in high fidelity 3D reconstructions made by slice and view scanning electron microcopy tomography. Large volume tomograms were made by repeated sequentially ion beam milling of a thin section and then using a normal incidence electron beam to image the sample surface. We found node functionality “f defects” where the normal node functionality of 3 rose to 4 and to 5, broken network struts, bridging struts linking the two different networks as well as donut loops comprised of 5 or 6 node rings instead of the characteristic 10 node ring of the (10,3)-a gyroid network. We term the 5 node donut loops as 5-4,3 and 5-4,4,3 defects while the 6 node donut loop is termed a 6-4,3,4 defect to indicate, following Wells, the number of struts in the loop as well as the node functionality and sequence.