An Exceptionally Stable and Scalable Sugar–Polyolefin Frank–Kasper A15 Phase

Abstract

One-component" soft material Frank-Kasper (FK) phases are an intriguing structural form of matter that possess periodically ordered structures arising from the self-reconfiguration and close packingo fa ni nitial assembly of identical "deformable" spheres into two or more size-or shape-distinct sets of particles.S ignificant challenges that must still be addressed to advance the field of soft matter FK phases further,h owever,i nclude their rare and unpredictable occurrence,u ncertain mechanisms of solid-state assembly,a nd low thermodynamic stability.H ere we show that ar eadily-accessible sugar-polyolefin conjugate quantitatively produces an exceptionally stable solid-state FK A15 phase through arapid and irreversible thermotropic order-order transition, which contrary to other prevailing proposed mechanisms,d oes not require mass transfer between particles or large structural reorganization in the bulk to establish unit cell non-equivalency.Our results provide the basis for arealistic strategy for obtaining practical and scalable quantities of adiverse range of sugar-polyolefin FK A15 phases with unique intrinsic physical properties and chemical reactivities not previously seen in such systems. Periodically-ordered, "one-component" soft matter Frank-Kasper (FK) phases,w hich arise from the topological close packing (TCP) of "deformable" sphere-shaped particles,have now been experimentally verified for amphiphilic liquid crystals and dendrons,b lock copolymers," giant" molecules and surfactants,a nd colloidal nanoparticles. [1-9] Frank and Kasper [10] originally developed the concept of TCP to rationalize how the complex crystal structures of certain intermetallic alloys arise through the packing of asymmetric polyhedra that are associated with different sets of atoms that define ap articular coordination number, CNx, where x = 12, 14, 15, or 16. Forexample,asshown in Figure 1, the unit cell of the cubic FK A15 (Pm3 n)p hase,w hich is found for some bimetallic alloys with A 3 Bstoichiometry (e.g. Nb 3 Sn), can be seen as arising from two crystallographically equivalent B sites that reside within CN12 distorted icosahedra, while six equivalent face-shared As ites are associated with CN14 polyhedra. Other commonly encountered bimetallic FK phases include the Laves C14 and C15 structures for A 2 B alloys (e.g.MgZn 2), and the complex s phase for AB alloys of

Discrete Block Copolymers with Diverse Architectures: Resolving Complex Spherical Phases with One Monomer Resolution

“…Block copolymers with chemically distinct components continue to fascinate the scientific community for their capability to spontaneously form exquisitely ordered structures at the nanometer scale, offering a broad and expanding range of practical applications. 1 The recent discovery of intriguing unconventional spherical packing lattices, e.g., Frank–Kasper phases and quasicrystalline phases, in block copolymer system 2 − 11 disrupts the long-standing principles of block copolymer phase behaviors, 12 − 14 representing significant advances in fundamental polymer science and opening up numerous possibilities for designing materials with unique properties. Despite interesting and unusual structures, detailed mechanisms of the formation and evolution of these complex lattices have yet to be fully established.…”

“…The Frank–Kasper phases (e.g., A15 and σ phase) are a family of low symmetry spherical structures with large unit cells consisting of multiple nonequivalent lattice sites, 16 , 17 observed originally in metals and alloys, and recently in soft matter systems. 2 − 11 , 18 − 26 Different from common periodic packing of identical spherical motifs (i.e., body/face centered cubic), the A15 phase is built up by a cubic lattice containing eight distorted spherical supramolecular motifs partitioned into two dissimilar groups with different sizes and shapes, while the σ phase is featured by a more complicated tetragonal unit cell with 30 spheres adopting five different coordination environments (see Scheme 1 , indicated by the different colored particles). On the other hand, the dodecagonal quasicrystalline phase (DQC) is generally recognized as an aperiodic structure that is closely related to the σ phase with 12-fold rotational symmetry ( Scheme 1 ).…”

Small‐Molecule Modulation of Soft‐Matter Frank–Kasper Phases: A Method for Adding Function to Form

“…Thermotropic one-component soft-matter Frank-Kasper (FK) phases are fascinating topologically close-packed (TCP) periodic structures that arise in the condensed state through the reconfiguration and self-sorting of deformable sphere-shaped particles into two or more crystallographically distinct sets with different coordination number, size, or shape. [1][2][3][4][5][6][7][8][9][10][11] On the other hand, the small set of currently known thermotropic FK phases that have now been experimentally established over the past 20 years for a range of different soft materials are largely of structural interest, and with only a few rare examples that can be viewed as coupling form with function. [12] Very recently, we reported that the sugar-polyolefin conjugate, cellobiose-triazole-linked atactic poly(4-methyl-1-pentene) (CB-aPMP) (1), undergoes an irreversible thermotropic order-order transition from an initial hexagonal cylindrical (C) morphology to produce a cubic FK A15 (Pm3 n) phase with the unit cell shown in Figure 1.…”

“…[12] Very recently, we reported that the sugar-polyolefin conjugate, cellobiose-triazole-linked atactic poly(4-methyl-1-pentene) (CB-aPMP) (1), undergoes an irreversible thermotropic order-order transition from an initial hexagonal cylindrical (C) morphology to produce a cubic FK A15 (Pm3 n) phase with the unit cell shown in Figure 1. [8] Further to the unique exceptional stability displayed by this A15 nanostructure over long periods of time of at least several months and upon thermal cycling over a wide temperature range from 25 8C to 200 8C, sugar-polyolefin conjugates, such as 1, can also be obtained in abundant quantities from readily available precursors and scalable synthetic processes, which include the living coordinative chain transfer polymerization (LCCTP) of a-olefins. [13,14] Given all of these favorable attributes of sugar-polyolefin FK phases, we have now embarked on a program to increase functional versatility.…”

“…As previously reported, the synthesis of 1 is easily achieved using copper-mediated click chemistry between a cellobiose propargyl amide derivative and an azidoterminated atactic poly(4-methyl-1-pentene) (N 3 -aPMP) building block. [8] For production of the N 3 -aPMP component, living chain transfer polymerization (LCCTP) of a fixed (1), vitamin E (2), and generic unit cells for A15, s, and BCC phases. Colored spheres of arbitrary but equal size represent different sets of crystallographically equivalent positions with a total sphere count of 8, 30, and 2 for the unit cells of A15, s, and BCC, respectively.…”