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Title: Thermally-induced transition of lamellae orientation in block-copolymer films on ‘neutral’ nanoparticle-coated substrates

Block-copolymer orientation in thin films is controlled by the complex balance between interfacial free energies, including the inter-block segregation strength, the surface tensions of the blocks, and the relative substrate interactions. While block-copolymer lamellae orient horizontally when there is any preferential affinity of one block for the substrate, we recently described how nanoparticle-roughened substrates can be used to modify substrate interactions. We demonstrate how such ‘neutral’ substrates can be combined with control of annealing temperature to generate vertical lamellae orientations throughout a sample, at all thicknesses. We observe an orientational transition from vertical to horizontal lamellae upon heating, as confirmed using a combination of atomic force microscopy (AFM), neutron reflectometry (NR) and rotational small-angle neutron scattering (RSANS). Using molecular dynamics (MD) simulations, we identify substrate-localized distortions to the lamellar morphology as the physical basis of the novel behavior. In particular, under strong segregation conditions, bending of horizontal lamellae induce a large energetic cost. At higher temperatures, the energetic cost of conformal deformations of lamellae over the rough substrate is reduced, returning lamellae to the typical horizontal orientation. Thus, we find that both surface interactions and temperature play a crucial role in dictating block-copolymer lamellae orientation. As a result, our combinedmore » experimental and simulation findings suggest that controlling substrate roughness should provide a useful and robust platform for controlling block-copolymer orientation in applications of these materials.« less
Authors:
 [1] ;  [2] ;  [3] ;  [4] ;  [4] ;  [5] ;  [4] ;  [3] ;  [4]
  1. Brookhaven National Lab. (BNL), Upton, NY (United States)
  2. Food and Drug Administration, Silver Springs, MD (United States)
  3. Univ. of Akron, Akron, OH (United States)
  4. National Institute of Standards and Technology, Gaithersburg, MD (United States)
  5. Univ. of Southern Mississippi, Hattiesburg, MS (United States)
Publication Date:
OSTI Identifier:
1213393
Report Number(s):
BNL--100794-2015-JA
Journal ID: ISSN 1744-683X; SMOABF; R&D Project: NC-001
Grant/Contract Number:
SC00112704
Type:
Accepted Manuscript
Journal Name:
Soft Matter
Additional Journal Information:
Journal Volume: 11; Journal Issue: 25; Journal ID: ISSN 1744-683X
Publisher:
Royal Society of Chemistry
Research Org:
Brookhaven National Laboratory (BNL), Upton, NY (United States)
Sponsoring Org:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
Country of Publication:
United States
Language:
English
Subject:
77 NANOSCIENCE AND NANOTECHNOLOGY self-assembly; orientation; nanoparticles; molecular dynamics; SANS; block copolymers; lamellae; RSANS; Center for Functional Nanomaterials