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Title: Reordering transitions during annealing of block copolymer cylinder phases

While equilibrium block-copolymer morphologies are dictated by energy-minimization effects, the semi-ordered states observed experimentally often depend on the details of ordering pathways and kinetics. In this study, we explore reordering transitions in thin films of block-copolymer cylinder-forming polystyrene- block-poly(methyl methacrylate). We observe several transient states as films order towards horizontally-aligned cylinders. In particular, there is an early-stage reorganization from randomly-packed cylinders into hexagonally-packed vertically-aligned cylinders; followed by a reorientation transition from vertical to horizontal cylinder states. These transitions are thermally activated. The growth of horizontal grains within an otherwise vertical morphology proceeds anisotropically, resulting in anisotropic grains in the final horizontal state. The size, shape, and anisotropy of grains are influenced by ordering history; for instance, faster heating rates reduce grain anisotropy. These results help elucidate aspects of pathway-dependent ordering in block-copolymer thin films.
 [1] ;  [1]
  1. Brookhaven National Lab. (BNL), Upton, NY (United States)
Publication Date:
OSTI Identifier:
Report Number(s):
Journal ID: ISSN 1744-683X; SMOABF; R&D Project: 16075; KC0403020
Grant/Contract Number:
Accepted Manuscript
Journal Name:
Soft Matter
Additional Journal Information:
Journal Name: Soft Matter; Journal ID: ISSN 1744-683X
Royal Society of Chemistry
Research Org:
Brookhaven National Laboratory (BNL), Upton, NY (United States)
Sponsoring Org:
USDOE Advanced Research Projects Agency - Energy (ARPA-E)
Country of Publication:
United States
77 NANOSCIENCE AND NANOTECHNOLOGY; block copolymer; self-assembly; reorientation; SEM; Center for Functional Nanomaterials