Disordered Bicontinuous Morphology from Frustrated Dumbbell-Shaped ABC Bottlebrush Block Terpolymers

Area of Science:

• Polymer Science and Engineering
• Materials Science
• Supramolecular Chemistry

Background:

• Bottlebrush block terpolymers offer complex self-assembly possibilities.
• Understanding their phase behavior is crucial for designing advanced materials.
• Architectural asymmetry in ABC block copolymers can lead to unique morphologies.

Purpose of the Study:

• To investigate the phase behavior of poly(ethylene-alt-propylene)-block-poly(d,l-lactide)-block-polystyrene (PEP-b-PLA-b-PS) bottlebrush block terpolymers.
• To characterize the resulting morphologies using advanced scattering and imaging techniques.
• To explore the influence of segment-segment interactions and chain architecture on phase formation.

Main Methods:

• Synthesis of PEP-b-PLA-b-PS bottlebrush block terpolymers via sequential ring-opening metathesis polymerization (ROMP).
• Small-angle X-ray scattering (SAXS) to determine nanoscale structures and phase behavior.
• Transmission electron microscopy (TEM) for direct visualization of polymer morphologies.

Main Results:

• Observed expected ordered hexagonal and lamellar morphologies.
• Discovered an unanticipated equilibrium disordered bicontinuous morphology over a significant compositional range.
• Morphological packing frustration, driven by asymmetric segment interactions and interfacial energies, stabilizes the bicontinuous structure.

Conclusions:

• The study expands the known phase behavior of ABC bottlebrush block terpolymers.
• A new route for creating equilibrium disordered bicontinuous structures has been identified.
• These cocontinuous materials hold promise for diverse applications requiring tailored microstructures.