Symmetry breaking in particle-forming diblock polymer/homopolymer blends

Abstract

<jats:p>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.</jats:p>

Binary Blends of Diblock Copolymers: An Efficient Route to Complex Spherical Packing Phases

“…showing that the FK , Laves C14 and C15 phases could become stable phases in AB/A binary blends in the dry brush regime. [ 6 ] Moreover, the local segregation of the A‐homopolymers has been illustrated by SCFT calculations for AB/A [ 24,25 ] and /A [ 26 ] binary blends. Another blending platform is mixing AB diblock copolymers with different lengths and compositions.…”

Reevaluation of Poly(ethylene-alt-propylene)-block-Polydimethylsiloxane Phase Behavior Uncovers Topological Close-Packing and Epitaxial Quasicrystal Growth

“…The occurrence of such phases, characterized by topological close-packing and unit cells containing ≥7 particles with differing volumes and geometries, represents a striking departure from classical diblock copolymer phase behavior, wherein the high-symmetry body-centered cubic (BCC) phase has long dominated the literature . Nonetheless, continued exploration of asymmetric block polymer melts and related self-assembling amphiphiles has revealed multiple routes to these complex packings, for example, via a reduction in molecular weight, , an increase in architectural/conformational asymmetry, − and/or blending. − Notably, many of these strategies are not new. Researchers have been exploring similar copolymer blends and low molecular weight amphiphiles for decades. − However, past identification of these phases was often complicated by slow ordering kinetics and the high X-ray or neutron scattering resolution necessary to resolve their Bragg reflections.…”

Medial packing and elastic asymmetry stabilize the double-gyroid in block copolymers

“…SCF results [49,50], and experiments [51], show that the stable TPN morphology can be altered upon blending homopolymer to the tubular domain, from DG to DD, and potentially to DP upon further homopolymer fraction. Analogous effects altering the symmetry of the stable morphology have been observed and studied theoretically in FK-forming sphere phases of BCP and homopolymer blends [52,53]. While it is arguably intuitive that homopolymer blends relax packing frustration in complex phases, it remains to be understood what geometric features of these morphologies lead a complex "host" to gain or lose stability over another upon loading with a "guest" species.…”