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Published June 20, 2017 | Published + Supplemental Material
Journal Article Open

Manipulating the ABCs of self-assembly via low-χ block polymer design


Block polymer self-assembly typically translates molecular chain connectivity into mesoscale structure by exploiting incompatible blocks with large interaction parameters (χ_ij). In this article, we demonstrate that the converse approach, encoding low-χ interactions in ABC bottlebrush triblock terpolymers (χ_(AC) ≲ 0), promotes organization into a unique mixed-domain lamellar morphology, which we designate LAM_P. Transmission electron microscopy indicates that LAM_P exhibits ACBC domain connectivity, in contrast to conventional three-domain lamellae (LAM_3) with ABCB periods. Complementary small-angle X-ray scattering experiments reveal a strongly decreasing domain spacing with increasing total molar mass. Self-consistent field theory reinforces these observations and predicts that LAM_P is thermodynamically stable below a critical χ_(AC), above which LAM_3 emerges. Both experiments and theory expose close analogies to ABA′ triblock copolymer phase behavior, collectively suggesting that low-χ interactions between chemically similar or distinct blocks intimately influence self-assembly. These conclusions provide fresh opportunities for block polymer design with potential consequences spanning all self-assembling soft materials.

Additional Information

© 2017 National Academy of Sciences. Contributed by Robert H. Grubbs, May 7, 2017 (sent for review January 25, 2017; reviewed by Thomas Epps and Edwin L. Thomas). The authors thank M. S. Ladinsky for assistance with ultramicrotomy, as well as M. T. Irwin, S. Chanpuriya, and T. Li for helpful discussions about sample preparation and TEM. The authors gratefully acknowledge helpful discussions with F. S. Bates and Z.-G. Wang. This work was supported by the National Science Foundation through Grant CHE-1502616. A.B.C. thanks the US Department of Defense for support through the National Defense Science and Engineering Graduate (NDSEG) Fellowship. C.M.B. thanks the Dreyfus Foundation for Environmental Postdoctoral Fellowship EP-13-142 and the University of California, Santa Barbara for funding. This research used resources of the Advanced Photon Source, a US Department of Energy Office of Science User Facility operated by Argonne National Laboratory under Contract DE-AC02-06CH11357. Author contributions: A.B.C., C.M.B., and R.H.G. designed research; A.B.C., S.C.J., R.K.W.S., and M.W.M. performed research; A.B.C., B.L., C.M.G., S.C.J., R.K.W.S., and M.W.M. contributed new reagents/analytic tools; A.B.C., C.M.B., B.L., and M.W.M. analyzed data; R.H.G. directed and served as principal investigator and discussed interpretation of the results; and A.B.C. and C.M.B. wrote the paper. Reviewers: T.E., University of Delaware; and E.L.T., Rice University. The authors declare no conflict of interest. This article contains supporting information online at www.pnas.org/lookup/suppl/doi:10.1073/pnas.1701386114/-/DCSupplemental.

Attached Files

Published - PNAS-2017-Chang-6462-7.pdf

Supplemental Material - pnas.1701386114.sapp.pdf


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August 21, 2023
October 25, 2023