Emergence of Frank–Kasper Phases from Chemically Simple Block Copolymer: Poly(ethylene oxide)-block-polyisoprene and Its Dry-Brush Blends
Zi-En Huang, Yung-Chuan Chuang, Yung-Chen Lin, Yu-Chuan Sung, Kai-Wei Luo, Jing-Cherng Tsai, Hsin-Lung Chen
TL;DR
The study shows that a specific block copolymer can form complex Frank–Kasper phases, which are rarely seen in simple polymer systems.
Contribution
A new linear diblock system, PEO-b-PI, is identified as capable of forming the FK σ phase, with expanded phase stability through blending.
Findings
PEO-b-PI forms the FK σ phase with a conformational asymmetry parameter ε ≈ 1.26.
Dry-brush blending with h-PEO enables a sequence of phase transitions from BCC to C15.
The Laves C15 phase remains stable at nearly symmetric compositions, beyond typical stability limits.
Abstract
The Frank–Kasper (FK) phases, also known as tetrahedrally close-packed structures, represent a unique class of ordered morphologies characterized by large unit cells with multiple nonequivalent lattice sites. To date, only a limited number of linear AB-type block copolymers (BCPs) have been shown to form FK phases. Here, we systematically investigate a sphere-forming poly(ethylene oxide)-block-poly(1,4-isoprene) (PEO-b-PI) with a conformational asymmetry parameter ε ≈ 1.26 and identify it as a new linear diblock system capable of forming the FK σ phase. In the neat PEO-b-PI, an abrupt enlargement of micelle size was observed across the BCC-to-σ lattice transition, despite a reduction in diblock molecular weight, indicating the pronounced influence of lattice symmetry on micelle dimensions at the onset of FK phase formation. To further expand the accessible FK phase regime, we employed…
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Taxonomy
TopicsBlock Copolymer Self-Assembly · Polymer crystallization and properties · Advanced Polymer Synthesis and Characterization