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Title: Exchange Kinetics for a Single Block Copolymer in Micelles of Two Different Sizes

Abstract

The effect of micellar size on the chain exchange kinetics in spherical micelles consisting of poly(methyl methacrylate)-block-poly(n-butyl methacrylate) (PMMA-b- PnBMA) in a mixture of ionic liquids (1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, [EMIM][TFSI], and 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)- imide, [BMIM][TFSI]) was investigated using time-resolved small-angle neutron scattering (TR-SANS). Two spherical micelles with different core sizes were prepared from a single block copolymer by using different protocols. In one case the micelles were formed in the presence of a cosolvent, while in the other a polymer thin film was directly dissolved in the ionic liquid. Interestingly, the micelle core size prepared from the latter method is ~30% larger than that obtained in the former case. TR-SANS experiments reveal that the rate of single chain exchange in the micelles with a larger core size is slowed down by ~3 times compared to the smaller core radius. We surmise this can be possibly attributed to the smaller interfacial area per chain, and larger corona density, for micelles with a larger core dimension. These geometrical factors can potentially lead to changes in both the attempt time and activation barrier for chain expulsion during the unimer exchange process. Our results clearly suggest that, in addition to the molecular characteristics of themore » block copolymer and solvent, the geometrical structure of the micelle plays an important role in the unimer dynamic exchange processes in block copolymer micelles.« less

Authors:
 [1];  [1]; ORCiD logo [1]
  1. Univ. of Minnesota, Minneapolis, MN (United States)
Publication Date:
Research Org.:
Argonne National Lab. (ANL), Argonne, IL (United States). Advanced Photon Source (APS)
Sponsoring Org.:
National Science Foundation (NSF); Northwestern University; E.I. DuPont de Nemours & Co.; The Dow Chemical Company; USDOE Office of Science (SC); National Institute of Standards and Technology (NIST)
OSTI Identifier:
1434721
Grant/Contract Number:  
AC02-06CH11357
Resource Type:
Journal Article: Accepted Manuscript
Journal Name:
Macromolecules
Additional Journal Information:
Journal Volume: 51; Journal Issue: 6; Journal ID: ISSN 0024-9297
Publisher:
American Chemical Society
Country of Publication:
United States
Language:
ENGLISH
Subject:
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY; Salts; Micelles; Copolymers; Scattering; Solvents

Citation Formats

Zhao, Dan, Ma, Yuanchi, and Lodge, Timothy P. Exchange Kinetics for a Single Block Copolymer in Micelles of Two Different Sizes. United States: N. p., 2018. Web. doi:10.1021/acs.macromol.7b02550.
Zhao, Dan, Ma, Yuanchi, & Lodge, Timothy P. Exchange Kinetics for a Single Block Copolymer in Micelles of Two Different Sizes. United States. doi:10.1021/acs.macromol.7b02550.
Zhao, Dan, Ma, Yuanchi, and Lodge, Timothy P. Tue . "Exchange Kinetics for a Single Block Copolymer in Micelles of Two Different Sizes". United States. doi:10.1021/acs.macromol.7b02550. https://www.osti.gov/servlets/purl/1434721.
@article{osti_1434721,
title = {Exchange Kinetics for a Single Block Copolymer in Micelles of Two Different Sizes},
author = {Zhao, Dan and Ma, Yuanchi and Lodge, Timothy P.},
abstractNote = {The effect of micellar size on the chain exchange kinetics in spherical micelles consisting of poly(methyl methacrylate)-block-poly(n-butyl methacrylate) (PMMA-b- PnBMA) in a mixture of ionic liquids (1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, [EMIM][TFSI], and 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)- imide, [BMIM][TFSI]) was investigated using time-resolved small-angle neutron scattering (TR-SANS). Two spherical micelles with different core sizes were prepared from a single block copolymer by using different protocols. In one case the micelles were formed in the presence of a cosolvent, while in the other a polymer thin film was directly dissolved in the ionic liquid. Interestingly, the micelle core size prepared from the latter method is ~30% larger than that obtained in the former case. TR-SANS experiments reveal that the rate of single chain exchange in the micelles with a larger core size is slowed down by ~3 times compared to the smaller core radius. We surmise this can be possibly attributed to the smaller interfacial area per chain, and larger corona density, for micelles with a larger core dimension. These geometrical factors can potentially lead to changes in both the attempt time and activation barrier for chain expulsion during the unimer exchange process. Our results clearly suggest that, in addition to the molecular characteristics of the block copolymer and solvent, the geometrical structure of the micelle plays an important role in the unimer dynamic exchange processes in block copolymer micelles.},
doi = {10.1021/acs.macromol.7b02550},
journal = {Macromolecules},
issn = {0024-9297},
number = 6,
volume = 51,
place = {United States},
year = {2018},
month = {3}
}

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