Control over the Self-Assembly and Dynamics of Metallacarborane Nanorotors by the Nature of the Polymer Matrix: A Solid-State NMR Study

Abstract

Solids that combine long-range order with rapid molecular reorientation offer a promising approach for the development of a novel class of functional materials with potential applications in materials science and nanotechnology. In this contribution, the capability of dicarbollide ions to undergo self-assembly processes with suitable macromolecules is demonstrated, and a strategy leading to the formation of structurally and dynamically well-defined amphidynamic polymeric composites is introduced. For this purpose, three amphidynamic nanocomposites were synthesized via the selfassembly of cobalt bis(dicarbollide) anions (CoD − ), with neutral poly(ethylene oxide) (PEO), and two isomers of poly(vinylpyridine), P2VP and P4VP, in protonated form. All of the systems were characterized by a combined study employing WAXS, advanced solid-state NMR, and quantum chemical calculations. It was found out that the interaction of neutral PEO with CoD − ions driven by weak dihydrogen bonding resulted in the formation of a uniquely organized periodic structure. In contrast, the self-assembly of the systems based on the electrostatic interactions (charge-transfer-assisted hydrogen bonding) of P2(4)VP was controlled by the position of the positive charge in pyridine ring and resulted in unique well-defined orientations of the CoD − ions (parallel and perpendicular) with respect to the polymer chains. In addition, the CoD − ions exhibited uniaxial relatively large-amplitude rotational motions in all of the nanocomposites over the broad range of T g . The motional amplitudes executed by the CoD − ions are significantly more extensive than those of the polymer segments in all of the systems. Macromolecules thus represent a rigid support (stator) for the more mobile CoD − ions (rotators). The obtained findings revealed that a relatively simple self-assembly procedure could be used for the preparation of well-defined amphidynamic nanocomposites, thereby opening a route to construct sophisticated supramolecular systems.

Nonclassical Hydrophobic Effect in Micellization: Molecular Arrangement of Non‐Amphiphilic Structures

“…[35] Surprisingly, no aggregates form in the PEO-complex, where the clusters are evenly dispersed within the PEO-matrix. [35] Thus, the aggregation is probably controlled by the mutual COSAN-matrix interaction.…”

Carboranes in the chemist's toolbox

“…120 The feasibility and performance of several possible rotors have been investigated in molecular dynamics studies, including polyhedral CB 11 , C 2 B 8 , or supra-icosahedral CB 13 or C 2 B 12 clusters that have [n]staffane "axles" and condensed aromatic ring "blades" and are mounted on a square grid and driven by flowing gas or an electric field. 117 Solid-state NMR spectra show that the metallacarborane anions rotate relatively freely in a rigid polymer matrix. 21(b) illustrates one such system containing a CB 11 cluster.…”

The Chaotropic Effect as an Assembly Motif in Chemistry

“…[3,19,20] Thee ffect becomes particularly pronounced for superchaotropic ions that reach beyond the classical Hofmeister scale. [10,18] Thechaotropic effect extends to molecular recognition events with macrocyclic hosts, [10,12,[21][22][23][24][25][26][27] biologically relevant interactions with proteins and peptides, [13,[28][29][30][31][32] association to small organic molecules, [10,33] binding to membranes, [17,[34][35][36][37][38] polymers, [39] as well as colloids, [15,18,40] and it manifests itself in solid-state structures between superchaotropic ions and organic components. [10,12,26,41,42] Thet erms "chaotropic effect" and "superchaotropic ions" have been readily absorbed by the chemical literature in different contexts.…”