In recent decades, the discoveries of complex low-symmetry phases in soft matter have inspired advances in molecular and materials design. However, understanding the mechanisms underlying symmetry selection across soft matter remains an important challenge in materials science. Block polymers represent attractive model materials because they permit wide synthetic tunability and provide access to multiple length scales (1-100 nm). However, to date the block polymer design space has been largely limited to variations in molecular weight, block volume fraction, and conformational asymmetry. The molecular architecture - the way in which chains are connected - offers rich potential but remains relatively unexplored in experimental block polymers. Our work bridges this gap, connecting molecular architecture, space-filling demands, and symmetry selection in block polymer self-assembly. Three series of block polymers were synthesized by living polymerization, tuning the architectural asymmetry across the linear-b-linear and linear-b-bottlebrush limits. The bottlebrush architecture amplifies two key ingredients for the formation of Frank-Kasper phases: high conformational asymmetry and high self-concentration. Analysis by small-angle X-ray scattering provides insight into the impact of architectural asymmetry on block polymer self-assembly. Increasing the asymmetry between blocks opens the complex phase window, expanding opportunities to tune symmetry selection in block polymer melts.
Bibliographical noteFunding Information:
This work was supported by the National Science Foundation under Grant DMR-1801993. A.B.C. thanks the Arnold O. Beckman Foundation for support through the Beckman Postdoctoral Fellowship. This work used the resources of the Advanced Photon Source (APS), a U.S. Department of Energy Office of Science User Facility operated by Argonne National Laboratory under Contract DE-AC02-06CH11357. SAXS, MAXS, and WAXS data were collected either at Beamline 12-ID-B of the APS or at the DuPont–Northwestern–Dow Collaborative Access Team (DND-CAT) Beamline, located at Sector 5 of the APS. The authors thank A. Lindsay, A. Mueller, and A. Jayaraman for assistance with select X-ray scattering measurements and for helpful discussions. The authors also gratefully acknowledge B. Lee, K. Dorfman, and M. Mahanthappa for helpful discussions.
© 2020 American Chemical Society.
- block polymer
PubMed: MeSH publication types
- Journal Article