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Abstract Herein, we examine pathway complexity in the supramolecular polymerization of a novelm‐terphenyl bis‐urea macrocycle. Designed to induce kinetically metastable states, the macrocycle‘s concentration‐dependent aggregation was studied via¹H NMR and IR spectroscopy in THF and CHCl₃. Temperature‐dependent UV‐Vis spectroscopy in water/THF revealed a cooperative nucleation‐growth mechanism, indicated by a shift in λmax to longer wavelengths upon cooling. Morphological studies using DLS, AFM, and SEM demonstrated fibrous aggregate formation. Thermal hysteresis observed in assembly‐disassembly cycles indicated kinetically trapped species, with cooling governed by kinetic control and heating by thermodynamic processes. Deviations in ΔH values during cooling, compared to van′t Hoff analysis and alignment of heating ΔH values with thermodynamic predictions, reinforced this distinction. Spontaneous nucleation retardation, resulting from monomer trapping, led to lag times of up to 50 minutes under specific conditions. Computational studies revealed the parallel urea conformation as the more stable monomer configuration, whereas the antiparallel conformation is more stable in dimers. By probing pathway complexity of the macrocycle, we demonstrate a distinct ability to control and stabilize kinetically trapped states, broadening the scope for designing macrocyclic supramolecular polymers with tailored properties. This work deepens our understanding of supramolecular dynamics, exploring ON‐pathway mechanisms and advancing tunable supramolecular materials. 

Abstract Herein, we probe the hydrogen bond‐driven self‐assembly of a triphenylamine (TPA) bis‐urea macrocycle in the presence and absence of guests. Comprised of methylene urea‐bridged TPAs with exterior tridodecyloxy benzene solubilizing groups, the macrocycle exhibits concentration‐dependent aggregate formation in THF and H₂O/THF mixtures as characterized by¹H NMR and DOSY experiments. Its assembly processes were further probed by temperature‐dependent UV/Vis and fluorescence spectroscopy. Upon heating, UV/Vis spectra exhibit a hypsochromic shift in the λ_max, while fluorescence spectra show an increase in emission intensity. Conversely, the protected macrocycle that lacks hydrogen bond donors demonstrates no significant change. Thermodynamic analysis indicates a cooperative self‐assembly pathway with distinct nucleation and elongation regimes. The morphology and structure of the aggregate were elucidated by dynamic light scattering, atomic force microscopy, scanning and transmission electron microscopy. Variable temperature emission spectra were utilized to monitor the impact of guests, such as diphenylacetylene, that can be bound in the columnar channels. The findings suggest that the elongation of assemblies is influenced by the presence of these guests. In comparison, diphenyl sulfoxide, likely functioning as a chain stopper, limited the assembly size. These studies suggest that judicious selection of (co)monomers may modulate the function and utility of these supramolecular systems.