Speaker
Andre Gröschel
(School of Science, Aalto University)
Description
Self-assembly describes the spontaneous arrangement of
building blocks into complex architectures and patterns with
internal symmetries and long-range order. Growth from the
bottom-up often involves local packing disorder and defect
formation. This presentation discusses the nucleation and
evolution of topological defects in template-free
self-assembled bilayer sheets growing to closed capsules
with bilayer thickness. For that, block copolymers were
self-assembled to 50 nm thick sheets and decorated on both
sides with a cylinder morphology forming distinct pattern
with disclinations of topological strength +1/2 in the
origin. The number as well as the distance of disclinations
has subtle influence on the local bending modulus of the
sheets that affect roll-up mechanism and ultimately govern
capsule shape through screening of areas with high-energy
curvatures. Since closed capsules still carry cylinders on
in- and outside of the membrane (50 nm), topological defects
reorganise to four disclinations to satisfy Euler
Characteristic. Electron tomography of the bilayers suggests
communication between the four disclinations on either side
of the membrane, but also across the membrane most likely
connecting all eight defects. Topological defects on
self-assembled closed shells supports the understanding of
complex soft matter nanostructures and may open routes to
precise functionalization for hierarchical self-assembly and
advanced gating.
