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Self-Assembly of Shaped ABC Coil-Bottlebrush Block Terpolymers
Camila Perales Rodriguez1, Mahesh K Mahanthappa1, Timothy P Lodge1
1†Department of Chemistry and ‡Department of Chemical Engineering & Materials Science, University of Minnesota, 207 Pleasant St SE, Minneapolis, Minnesota 55455, United States.
ACS Polymers Au
|August 15, 2026
Summary
Shaped coil-brush triblock terpolymers were synthesized, but the bottlebrush architecture suppressed the expected double gyroid phase. Instead, hexagonal and lamellar phases formed, indicating slow ordering kinetics.
Area of Science:
- Polymer Chemistry
- Materials Science
- Supramolecular Chemistry
Background:
- Block copolymers self-assemble into ordered nanostructures, crucial for advanced materials.
- The influence of polymer architecture, particularly bottlebrush structures, on phase behavior is not fully understood.
- Understanding phase stability is key for designing materials with specific network morphologies like the double gyroid (GYR).
Purpose of the Study:
- To investigate the effect of a digitally shaped bottlebrush architecture on the phase stability of ABC triblock terpolymers.
- To explore the formation of network phases, specifically the double gyroid (GYR), in these novel terpolymers.
- To correlate polymer composition and architecture with observed nanostructure formation.
Main Methods:
- Synthesis of ABC coil-brush triblock terpolymers via sequential living ring-opening metathesis polymerization (ROMP).
- Characterization of polymer molecular weight (M_n) and dispersity (Đ).
- Small-angle X-ray scattering (SAXS) analysis at elevated temperatures (100 °C) to determine phase behavior.
Main Results:
- All synthesized terpolymers (M_n = 7-30 kg/mol, Đ ≤ 1.04) were well-segregated, showing no order-disorder transition.
- Predominant formation of hexagonal (HEX) and lamellar (LAM) phases, with some HEX/LAM coexistence.
- Systematic suppression of the double gyroid (GYR) phase by the shaped bottlebrush architecture, especially with longer P blocks (P_9). Previously studied diblocks showed GYR windows.
Conclusions:
- The specific 'shaped' bottlebrush architecture hinders the formation of the double gyroid (GYR) phase in these triblock terpolymers.
- Phase transitions (HEX/LAM) depend on the volumetric fraction (f_M) and the length/sequence of the P blocks.
- Ordering kinetics are very slow, with no structural refinement observed over hours, despite low glass transition temperatures.
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