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Compositionally asymmetric diblock copolymers provide an attractive platform for understanding the emergence of tetragonally close-packed, Frank–Kasper phases in soft matter. Block-polymer phase behavior is governed by a straightforward competition between chain stretching and interfacial tension under the constraint of filling space at uniform density. Experiments have revealed that diblock copolymers with insufficient conformational asymmetry to form Frank–Kasper phases in the neat-melt state undergo an interconversion from body-centered cubic (bcc) close-packed micelles to a succession of Frank–Kasper phases (σ to C14 to C15) upon the addition of minority-block homopolymer in the dry-brush regime, accompanied by the expected transition from bcc to hexagonally packed cylinders in the wet-brush regime. Self-consistent field theory data presented here qualitatively reproduce the salient features of the experimental phase behavior. A particle-by-particle analysis of homopolymer partitioning furnishes a basis for understanding the symmetry breaking from the high-symmetry bcc phase to the lower-symmetry Frank–Kasper phases, wherein the reconfiguration of the system into polyhedra of increasing volume asymmetry delays the onset of macroscopic phase separation.
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Self-assembled complex micelle phase stability in ABA-type triblock copolymers and related core-shell bottlebrushes
We report the synthesis and temperature-dependent morphologies of a series of polylactide-block-poly (ε-decalactone)-block-polylactide (LDL) triblock copolymers with 𝑀𝑛=16.0–18.1kg/mol and volume fractions 𝑓L=0.27–0.31 and associated core-shell bottlebrush (csBB) polymers, which derive from enchaining LDL triblocks through a polymerizable midchain functionality. While the LDL triblocks form micellar Frank-Kasper A15 and σ phases due to the conformational asymmetry of this monomer pair, the csBB morphologies sensitively depend on the backbone degree of polymerization (𝑁bb). At low 𝑁bb values, micellar Frank-Kasper phases with the brush backbone situated in the matrix domain are stable, albeit with a modest reduction in the mean interfacial curvature evidenced by a σ to A15 order-to-order transition. However, larger 𝑁bb values drive csBBs to form hexagonally packed cylinders phases. This 𝑁bb-dependent phase behavior is rationalized in terms of a star-to-bottlebrush transition. At low 𝑁bb values, the csBBs are akin to star polymers with pointlike junctions that can support complex micelle packings. As 𝑁bb increases, the csBBs adopt cylindrical molecular geometries with extended backbones situated in the matrix domain that prefer hexagonally packed cylinders morphologies.
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- Award ID(s):
- 2003668
- PAR ID:
- 10512234
- Publisher / Repository:
- American Physical Society
- Date Published:
- Journal Name:
- Physical Review Materials
- Volume:
- 8
- Issue:
- 1
- ISSN:
- 2475-9953
- Page Range / eLocation ID:
- 015603
- Subject(s) / Keyword(s):
- Self-Assembly Block Copolymers Frank-Kasper Phases Bottlebrush Polymers Brush Block Polymers
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1103/PhysRevMaterials.8.015603
