Molecular Weight Dependence of Block Copolymer Micelle Fragmentation Kinetics

Julia T. Early, Alison Block, Kevin G. Yager, Timothy P. Lodge

Research output: Contribution to journalArticlepeer-review

13 Scopus citations


The effect of molecular weight (M) on the fragmentation kinetics of micelles formed by 1,2-polybutadiene-block-poly(ethylene oxide) (PB-PEO) copolymers was studied in the ionic liquid 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide. A series of six samples, with total M ranging from 104 to 105 g mol-1 and nearly constant composition (fPEO ≈ 0.4), were examined; all six formed spherical micelles with PEO coronas. Nonequilibrium PB-PEO micelles were prepared by direct dissolution, a process that systematically produces nanoparticles with mean aggregation numbers more than twice the equilibrium values. When subjected to high temperature annealing (170 °C), the average micelle radius was found to decrease substantially, as determined by temperature-jump dynamic light scattering (T-jump DLS) and time-resolved small-angle X-ray scattering (TR-SAXS). The characteristic fragmentation times (τ) were found to increase strongly with increasing degree of polymerization N, as τ ∼N1.8. This result compares favorably with the prediction of a previously untested model.

Original languageEnglish (US)
Pages (from-to)7748-7758
Number of pages11
JournalJournal of the American Chemical Society
Issue number20
StatePublished - May 26 2021

Bibliographical note

Funding Information:
This work was supported primarily by the National Science Foundation (DMR-1707578). Additional support came from the University of Minnesota Doctoral Dissertation Fellowship (JTE), the University of Minnesota Robert and Jill DeMaster Excellence Fellowship (J.T.E.), the Research Experiences for Undergraduates (REU) Program of the National Science Foundation under Award Number DMR-1559833 (through the University of Minnesota MRSEC under Award Number DMR-2011401, A.B.), and from the U.S. Department of Energy (DOE), Office of Science, Office of Workforce Development for Teachers and Scientists, Office of Science Graduate Student Research (SCGSR) program (J.T.E.). The SCGSR program is administered by the Oak Ridge Institute for Science and Education (ORISE) for the DOE. ORISE is managed by ORAU under contract number DE-SC0014664. Portions of this work were performed at the Center for Functional Nanomaterials, and the National Synchrotron Light Source II, Brookhaven National Laboratory, which are supported by the U.S. DOE Office of Science under Contract DE-SC0012704. Portions of this work were performed at the DuPont-Northwestern-Dow Collaborative Access Team (DND-CAT) located at Sector 5 of the Advanced Photon Source (APS). DND-CAT is supported by Northwestern University, E.I. DuPont de Nemours & Co., and The Dow Chemical Company. This research used resources of the Advanced Photon Source, a U.S. Department of Energy (DOE) Office of Science User Facility operated for the DOE Office of Science by Argonne National Laboratory under Contract No. DE-AC02-06CH11357. We thank Dr. Ruipeng Li and Dr. Esther Tsai for assistance with TR-SAXS measurements at the 11-BM CMS beamline at the NSLS-II and Dr. Lihua Zhang for insightful discussions on high temperature LP-TEM. We thank Claire Seitzinger for assisting with SAXS measurements of bulk PB-PEO diblocks.

Publisher Copyright:

MRSEC Support

  • Partial

PubMed: MeSH publication types

  • Journal Article
  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.


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