Revision komplexer supramolekularer Polymerisation unter kinetischer und thermodynamischer Kontrolle

Abstract

Pathway‐Complexity, hierarchische Organisation, Außer‐Equilibrium‐ und metastabile oder kinetisch gefangene Spezies sind Begriffe die in jüngsten, hochqualitativen Publikationen im Feld der supramolekularen Polymere häufig verwendet werden. Oftmals sind die Terminologien, die die verschiedenen Selbstassemblierungspfade, die beteiligten Spezies und deren Beziehung sowie relativen Stabilitäten zueinander beschreiben, nicht trivial. In der Literatur sind häufig verschiedene Begriffe und Klassifizierungen zu finden, in vielen Fällen jedoch ohne klare Definitionen oder Richtlinien wie sie zu benutzen sind oder wie sie experimentell unterschieden werden können. Ziel dieses Kurzaufsatzes ist es, die existierenden Konzepte mithilfe jüngster Literatur zu klassifizieren, differenzieren und zu korrelieren. Dadurch soll der Leser eine generelle Einsicht in thermodynamische und kinetische Aspekte komplexer supramolekularer Polymerisationsprozesse erhalten. Ein gutes Verständnis dieser Begriffe und Konzepte sollte dazu beitragen, neue, komplexe, funktionale Materialien zu erschaffen.

Luminescence and Length Control in Nonchelated d8‐Metallosupramolecular Polymers through Metal‐Metal Interactions

“…Notably, the transformation is slightly faster at higher concentrations, indicative of an on-pathway, consecutive transformation. [32] The initially more pronounced increase of the emission intensity ( � 0-200 min) and the subsequent levelling ( � 200-500 min) could possibly be correlated to an initially greater number of SP strands, for which the transformation to SP 1B was already initiated in the precedent sonication step. Once these strands have fully rearranged to SP 1B, the continuous mechanical stirring can only induce a gradual transformation for residual 1A SPs.…”

Interplay Between Hydrogen Bonding and Electron Transfer in Mixed Valence Assemblies of Triarylamine Trisamides

“…The initial state is not recovered upon slow heating since a higher ratio of hydrogen‐bonded monomers appears to be present according to both FTIR and UV‐Vis‐NIR data. Such important thermal hysteresis and the aforementioned observation of gel formation over time are the hallmarks of complex aggregation pathways [49,50] . FTIR and UV‐Vis data in the hysteresis regime are virtually identical and thus do not allow to determine the exact nature of the kinetically formed species [29] .…”

Impact of Positional Isomerism on Pathway Complexity in Aqueous Media

“…This transformation can be accelerated by increasing concentration and/or temperature (see plot of Abs 615 vs.time in Figure 3h), which is typical for the consecutive transformation of an on-pathway species. [6] Therefore, A converts into B via ar earrangement of the dye molecules within the aggregate,w hich does not involve the disassembly into free monomeric species.T his transition between two precise aggregate species is also corroborated by ac lear isosbestic point at 584 nm.…”

“…[5] Control over the competing aggregation pathways in these molecular systems is typically achieved by optimization of sample preparation protocols.These processes are generally tedious and often require avery specific set of experimental conditions (that is,concentration, temperature, solvent composition, and others). [6] Alternatively,these complex sample preparation methods could be simplified by molecular design strategies,w hich have been recently introduced to broaden the scope of pathway complexity.T od ate, these approaches have mainly focused on the geometrical modification of the building blocks either by systematic size variation of substituents [4d,h] or length variation of ag iven molecular fragment (for example, p-system, [4g,5m] alkyl spacers, [4e, 5d] or side chains [5a,j] ). In this regard, controlling pathway complexity in aqueous media by molecular design is particularly challenging,a st he competition between hydrophobic and other non-covalent interactions [5b-f,h,i,k,l] makes the selfassembly considerably less predictable.I na mphiphilic selfassembly,f ine-tuning of the hydrophilic/hydrophobicr atio is aw ell-known strategy for morphology control [7] and, to am inor extent, has also been observed to induce pathway complexity.…”