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Title: Martensitic Transformation of Close-Packed Polytypes of Block Copolymer Micelles

Abstract

Here, we report martensitic shear transformation of strongly segregated block copolymer micelles on face-centered cubic (FCC) lattices to hexagonally close-packed (HCP) structures elucidated by X-ray scattering characterizations. The initial FCC crystal structures of the block copolymer micelles were prepared by direct dissolution of poly(1,2-butadiene-b-ethylene oxide) (PB-PEO) diblock copolymer in the water at 25 °C, and the FCC crystal domains were shear-aligned during the sample preparation process for the X-ray scattering measurements. Heating the shear-aligned FCC crystals of the PB-PEO micelles above 80 °C initiated the transformation to HCP structures, which are also found stable at 25 °C when cooled from the transition temperature. Interestingly, we found that the HCP crystal domains are also aligned, and this suggests that the FCC-to-HCP phase transition has occurred by the martensitic shear transformation. Scattering pattern analysis reveals that the martensitic shear transformation proceeds by preferentially dislocating a specific set of two-dimensional hexagonal close-packed (2D-HCP) layers among four equivalent 2D-HCP layers of the initially shear-aligned FCC crystals. We believe that the selective martensitic shear transformation originates from the orthorhombic-like morphology of the FCC crystal domains formed by slip dislocations and stratifications of initial FCC crystal grains during the sample preparation process. In the shear-aligned FCCmore » crystals with the orthorhombic-like crystal domains, the specific 2D-HCP layers chosen for the martensitic shear transformation have the least area of dislocations, i.e., the least kinetic energy barrier, for the FCC-to-HCP phase transition and appear to be preferentially utilized. These results show that the size and morphology of crystal domains are critical to the formation, stability, and transformation of crystalline structures and consequently control the polymorphism of solid compounds.« less

Authors:
 [1];  [2]; ORCiD logo [3]; ORCiD logo [1]
  1. Rensselaer Polytechnic Inst., Troy, NY (United States)
  2. Univ. of Minnesota, Minneapolis, MN (United States)
  3. Brookhaven National Lab. (BNL), Upton, NY (United States)
Publication Date:
Research Org.:
Brookhaven National Lab. (BNL), Upton, NY (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
OSTI Identifier:
1570674
Report Number(s):
BNL-212197-2019-JAAM
Journal ID: ISSN 0024-9297
Grant/Contract Number:  
SC0012704
Resource Type:
Accepted Manuscript
Journal Name:
Macromolecules
Additional Journal Information:
Journal Volume: 52; Journal Issue: 17; Journal ID: ISSN 0024-9297
Publisher:
American Chemical Society
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE

Citation Formats

Chen, Liwen, Lee, Han Seung, Zhernenkov, Mikhail, and Lee, Sangwoo. Martensitic Transformation of Close-Packed Polytypes of Block Copolymer Micelles. United States: N. p., 2019. Web. doi:10.1021/acs.macromol.9b00917.
Chen, Liwen, Lee, Han Seung, Zhernenkov, Mikhail, & Lee, Sangwoo. Martensitic Transformation of Close-Packed Polytypes of Block Copolymer Micelles. United States. doi:10.1021/acs.macromol.9b00917.
Chen, Liwen, Lee, Han Seung, Zhernenkov, Mikhail, and Lee, Sangwoo. Mon . "Martensitic Transformation of Close-Packed Polytypes of Block Copolymer Micelles". United States. doi:10.1021/acs.macromol.9b00917.
@article{osti_1570674,
title = {Martensitic Transformation of Close-Packed Polytypes of Block Copolymer Micelles},
author = {Chen, Liwen and Lee, Han Seung and Zhernenkov, Mikhail and Lee, Sangwoo},
abstractNote = {Here, we report martensitic shear transformation of strongly segregated block copolymer micelles on face-centered cubic (FCC) lattices to hexagonally close-packed (HCP) structures elucidated by X-ray scattering characterizations. The initial FCC crystal structures of the block copolymer micelles were prepared by direct dissolution of poly(1,2-butadiene-b-ethylene oxide) (PB-PEO) diblock copolymer in the water at 25 °C, and the FCC crystal domains were shear-aligned during the sample preparation process for the X-ray scattering measurements. Heating the shear-aligned FCC crystals of the PB-PEO micelles above 80 °C initiated the transformation to HCP structures, which are also found stable at 25 °C when cooled from the transition temperature. Interestingly, we found that the HCP crystal domains are also aligned, and this suggests that the FCC-to-HCP phase transition has occurred by the martensitic shear transformation. Scattering pattern analysis reveals that the martensitic shear transformation proceeds by preferentially dislocating a specific set of two-dimensional hexagonal close-packed (2D-HCP) layers among four equivalent 2D-HCP layers of the initially shear-aligned FCC crystals. We believe that the selective martensitic shear transformation originates from the orthorhombic-like morphology of the FCC crystal domains formed by slip dislocations and stratifications of initial FCC crystal grains during the sample preparation process. In the shear-aligned FCC crystals with the orthorhombic-like crystal domains, the specific 2D-HCP layers chosen for the martensitic shear transformation have the least area of dislocations, i.e., the least kinetic energy barrier, for the FCC-to-HCP phase transition and appear to be preferentially utilized. These results show that the size and morphology of crystal domains are critical to the formation, stability, and transformation of crystalline structures and consequently control the polymorphism of solid compounds.},
doi = {10.1021/acs.macromol.9b00917},
journal = {Macromolecules},
number = 17,
volume = 52,
place = {United States},
year = {2019},
month = {8}
}

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