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Title: Implications of grain size variation in magnetic field alignment of block copolymer blends

Abstract

Recent experiments have highlighted the intrinsic magnetic anisotropy in coil–coil diblock copolymers, specifically in poly(styrene- block-4-vinylpyridine) (PS- b-P4VP), that enables magnetic field alignment at field strengths of a few tesla. We consider here the alignment response of two low molecular weight (MW) lamallae-forming PS- b-P4VP systems. Cooling across the disorder–order transition temperature (T odt) results in strong alignment for the higher MW sample (5.5K), whereas little alignment is discernible for the lower MW system (3.6K). This disparity under otherwise identical conditions of field strength and cooling rate suggests that different average grain sizes are produced during slow cooling of these materials, with larger grains formed in the higher MW material. Blending the block copolymers results in homogeneous samples which display T odt, d-spacings, and grain sizes that are intermediate between the two neat diblocks. Similarly, the alignment quality displays a smooth variation with the concentration of the higher MW diblock in the blends, and the size of grains likewise interpolates between limits set by the neat diblocks, with a factor of 3.5× difference in the grain size observed in high vs low MW neat diblocks. Finally, these results highlight the importance of grain growth kinetics in dictating the field responsemore » in block copolymers and suggests an unconventional route for the manipulation of such kinetics.« less

Authors:
 [1];  [2];  [3]; ORCiD logo [3];  [4]; ORCiD logo [1]
  1. Yale Univ., New Haven, CT (United States)
  2. Brookhaven National Lab. (BNL), Upton, NY (United States); Univ. of Warsaw, Warsaw (Poland)
  3. Univ. of Wisconsin, Madison, WI (United States)
  4. Brookhaven National Lab. (BNL), Upton, NY (United States)
Publication Date:
Research Org.:
Brookhaven National Lab. (BNL), Upton, NY (United States). Center for Functional Nanomaterials (CFN)
Sponsoring Org.:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
OSTI Identifier:
1368673
Report Number(s):
BNL-114014-2017-JA
Journal ID: ISSN 2161-1653; KC0403020
Grant/Contract Number:
SC00112704
Resource Type:
Journal Article: Accepted Manuscript
Journal Name:
ACS Macro Letters
Additional Journal Information:
Journal Volume: 6; Journal Issue: 4; Journal ID: ISSN 2161-1653
Publisher:
American Chemical Society (ACS)
Country of Publication:
United States
Language:
English
Subject:
77 NANOSCIENCE AND NANOTECHNOLOGY; magnetic alignment; Center for Functional Nanomaterials

Citation Formats

Rokhlenko, Yekaterina, Majewski, Pawel W., Larson, Steven R., Gopalan, Padma, Yager, Kevin G., and Osuji, Chinedum O.. Implications of grain size variation in magnetic field alignment of block copolymer blends. United States: N. p., 2017. Web. doi:10.1021/acsmacrolett.7b00036.
Rokhlenko, Yekaterina, Majewski, Pawel W., Larson, Steven R., Gopalan, Padma, Yager, Kevin G., & Osuji, Chinedum O.. Implications of grain size variation in magnetic field alignment of block copolymer blends. United States. doi:10.1021/acsmacrolett.7b00036.
Rokhlenko, Yekaterina, Majewski, Pawel W., Larson, Steven R., Gopalan, Padma, Yager, Kevin G., and Osuji, Chinedum O.. Tue . "Implications of grain size variation in magnetic field alignment of block copolymer blends". United States. doi:10.1021/acsmacrolett.7b00036. https://www.osti.gov/servlets/purl/1368673.
@article{osti_1368673,
title = {Implications of grain size variation in magnetic field alignment of block copolymer blends},
author = {Rokhlenko, Yekaterina and Majewski, Pawel W. and Larson, Steven R. and Gopalan, Padma and Yager, Kevin G. and Osuji, Chinedum O.},
abstractNote = {Recent experiments have highlighted the intrinsic magnetic anisotropy in coil–coil diblock copolymers, specifically in poly(styrene-block-4-vinylpyridine) (PS-b-P4VP), that enables magnetic field alignment at field strengths of a few tesla. We consider here the alignment response of two low molecular weight (MW) lamallae-forming PS-b-P4VP systems. Cooling across the disorder–order transition temperature (Todt) results in strong alignment for the higher MW sample (5.5K), whereas little alignment is discernible for the lower MW system (3.6K). This disparity under otherwise identical conditions of field strength and cooling rate suggests that different average grain sizes are produced during slow cooling of these materials, with larger grains formed in the higher MW material. Blending the block copolymers results in homogeneous samples which display Todt, d-spacings, and grain sizes that are intermediate between the two neat diblocks. Similarly, the alignment quality displays a smooth variation with the concentration of the higher MW diblock in the blends, and the size of grains likewise interpolates between limits set by the neat diblocks, with a factor of 3.5× difference in the grain size observed in high vs low MW neat diblocks. Finally, these results highlight the importance of grain growth kinetics in dictating the field response in block copolymers and suggests an unconventional route for the manipulation of such kinetics.},
doi = {10.1021/acsmacrolett.7b00036},
journal = {ACS Macro Letters},
number = 4,
volume = 6,
place = {United States},
year = {Tue Mar 28 00:00:00 EDT 2017},
month = {Tue Mar 28 00:00:00 EDT 2017}
}

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  • External electric fi elds readily align birefringent block-copolymer mesophases. In this study the effect of gold nanoparticles on the electric-fi eld-induced alignment of a lamellae-forming polystyrene- block -poly(2-vinylpyridine) copolymer is assessed. Nanoparticles are homogeneously dispersed in the styrenic phase and promote the quantitative alignment of lamellar domains by substantially lowering the critical field strength above which alignment proceeds. The results suggest that the electric-fi eldassisted alignment of nanostructured block copolymer/nanoparticle composites may offer a simple way to greatly mitigate structural and orientational defects of such fi lms under benign experimental conditions.
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  • No abstract prepared.