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SUMMARY:3D Morphological Characterization of Complex Soft Matter Assemblie
 s at the Sub-Unit Cell Level
DTSTART:20190429T131500
DTEND:20190429T141500
DTSTAMP:20260407T113818Z
UID:e030f61e1434f49dbf75a382c86fa60103e542a60853624c7d67151b
CATEGORIES:Conferences - Seminars
DESCRIPTION:Prof. Erwin Thomas\, Thomas Research Group\, Rice University H
 ouston USA\nThe double gyroid (DG) microdomain structure is a complex 3D t
 ubular network structure found in block copolymers as well as in butterfly
  wings and amphiphilic phases.   We employ a slice and view electron mic
 roscopy technique to directly generate a 3D tomogram of the DG nanoscale s
 tructure.  The material studied is a polystyrene (PS) – polydimethylsil
 oxane (PDMS) diblock copolymer that exhibits the DG network morphology wit
 h a lattice parameter of ~ 130nm\, with feature sizes on the 20 nm scale\,
  typical of many soft matter assemblies.   By alternating between a thin
  ion beam slice and a secondary electron image using a low voltage inciden
 t electron beam\, the voxel size is approximately 3 x 3 x 3 nm3 allowing a
 nalysis of a comprehensive set of sub-unit cell morphological descriptors 
 and enabling critical comparison to theoretical models of the structure. 
  We find that the PS-PDMS material does not exhibit cubic symmetry\, but r
 ather a range of triclinic shapes\, most likely due to distortions of the 
 structure from solvent induced shrinkage during film preparation.  Analys
 is of the triclinic unit cell determines the magnitudes and directions of 
 the shear and tensile deformations that can be re-expressed as an eigen-ma
 trix of principal compressive/tensile strains (average compressive strain 
 of ~ -20% and tensile strain about + 20%).  Morphological characteristics
  are analyzed including direct measures of the distributions of the distan
 ces between the interface between the two blocks and the skeletal graph an
 d the distance between the interface and the triply periodic gyroid minima
 l surface\, the mean and Gaussian curvatures of the interface\, the dihedr
 al angle between adjacent nodes\, as well as the node-node strut lengths a
 nd directions. These very detailed experimental measures are compared with
  self consistent field theory calculations of a PS-PDMS melt undergoing th
 e ODT under boundary conditions that are matched to the deformed cubic (i.
 e. triclinic) unit cell.\n \nReferences:\n \nPrasad\, I.\, Jinnai\, H.\,
  Ho\, R-M.\, Thomas\, E. L. and Grason\, G. “Anatomy of triply-periodic 
 network assemblies:  Characterizing skeletal and inter-domain surface geo
 metry of block copolymer gyroids\,” Soft Matter\, 14\, 3612-3623 (2018).
 \n \nX. Feng\, H. Guo and E. L. Thomas\, “Topological Defects in Tubula
 r Network Block Copolymers\,” Polymer\, (2019) https://doi.org/10.1016/j
 .polymer.2019.01.085\n\nBio: Edwin L. “Ned” Thomas served as William a
 nd Stephanie Sick Dean of the George R. Brown School of Engineering at Ric
 e from 2011 to 2017. He holds joint appointments in the Departments of Mat
 erials Science and NanoEngineering and Chemical and Biomolecular Engineeri
 ng and collaborates with scientists and engineers in the Richard E. Smalle
 y Institute for Nanoscale Science and Technology at Rice.\n \nThomas is a
  materials scientist and mechanical engineer and is passionate about promo
 ting engineering leadership and student design competitions. His research 
 is currently focused on using 2D and 3D lithography\, direct-write and sel
 f-assembly techniques for creating metamaterials with unprecedented mechan
 ical and thermal properties.\n \nThomas is the former head of the Departm
 ent of Materials Science and Engineering at the Massachusetts Institute of
  Technology\, a position he held from 2006 until his appointment at Rice i
 n July 2011. He was named Morris Cohen Professor of Materials Science and 
 Engineering in 1989 and is the founder and former director of the MIT Inst
 itute for Soldier Nanotechnology (2002-2006).\n \nBefore joining MIT in 1
 988\, Thomas founded and served as co-director of the Institute for Interf
 ace Science and was head of the Department of Polymer Science and Engineer
 ing at the University of Massachusetts. He is a recipient of the 1991 High
  Polymer Physics Prize of the American Physical Society and the 1985 Ameri
 can Chemical Society Creative Polymer Chemist award. He was elected to the
  National Academy of Engineering and the American Academy of Arts and Scie
 nces in 2009\, Inaugural Fellow of the Materials Society in 2008\, Fellow 
 of the American Association for the Advancement of Science in 2003 and Fel
 low of the American Physical Society in 1986. He wrote the undergraduate t
 extbook\, The Structure of Materials\, and has coauthored more than 450 pa
 pers and holds 20 patents.\n \nThomas received a B.S. in mechanical engin
 eering from the University of Massachusetts and his Ph.D. in materials sci
 ence and engineering from Cornell University.\n\n 
LOCATION:MXF 1 https://plan.epfl.ch/?room==MXF%201
STATUS:CONFIRMED
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