Multi-component systems often display convoluted behavior, pathway complexity and coupled equilibria. In recent years, several ways to control complex systems by manipulating the subtle balances of interaction energies between the individual components have been explored and thereby shifting the equilibrium between different aggregate states. Here we show the enantioselective chain-capping and dilution-induced supramolecular polymerization with a Zn2+-porphyrin-based supramolecular system when going from long, highly cooperative supramolecular polymers to short, disordered aggregates by adding a monotopic Mn3+-porphyrin monomer. When mixing the zinc and manganese centered monomers, the Mn3+-porphyrins act as chain-cappers for Zn2+-porphyrin supramolecular polymers, effectively hindering growth of the copolymer and reducing the length. Upon dilution, the interaction between chain-capper and monomers weakens as the equilibria shift and long supramolecular polymers form again. This dynamic modulation of aggregate morphology and length is achieved through enantioselectivity in the aggregation pathways and concentration-sensitive equilibria. All-atom and coarse-grained molecular simulations provide further insights into the mixing of the species and their exchange dynamics. Our combined experimental and theoretical approach allows for precise control of molecular self-assembly and chiral discrimination in complex systems.
Despite the noteworthy progress made in the nanotubular architectures with well-de ned lengths and diameter, the synthesis of a purely covalent bonded organic nanotube, so far, proved to be elusive. Our work includes a hitherto unavailable structure, "Covalent Organic Nanotubes (CONTs)," to the repertoire. Strong covalent bonds between C, N, and O imparts high thermal and chemical stability of CONTs. This novel bottom-up approach provides an edge over the carbon nanotubes (CNTs) in functionalization, synthetic conditions, and porosity. CONT-1 exhibits a BET surface area of 321 m2g-1. These exible CONTs intertwine with each other. The computational studies establish the role of solvent as the critical driving force for this type of convolution. Upon ultrasonication, the intertwined CONT-1 coil to form the toroidal superstructure.
The
fast dynamics occurring in natural processes increases the
difficulty of creating biomaterials capable of mimicking Nature. Within
synthetic biomaterials, water-soluble supramolecular polymers show
great potential in mimicking the dynamic behavior of these natural
processes. In particular, benzene-1,3,5-tricaboxamide (BTA)-based
supramolecular polymers have shown to be highly dynamic through the
exchange of monomers within and between fibers, but their suitability
as biomaterials has not been yet explored. Herein we systematically
study the interactions of BTA supramolecular polymers bearing either
tetraethylene glycol or mannose units at the periphery with different
biological entities. When BTA fibers were incubated with bovine serum
albumin (BSA), the protein conformation was only affected by the fibers
containing tetraethylene glycol at the periphery (BTA-OEG
4
). Coarse-grained molecular simulations showed that BSA interacted
with BTA-OEG
4
fibers rather than with BTA-OEG
4
monomers that are present in solution or that may exchange out of
the fibers. Microscopy studies revealed that, in the presence of BSA,
BTA-OEG
4
retained their fiber conformation although their
length was slightly shortened. When further incubated with fetal bovine
serum (FBS), both long and short fibers were visualized in solution.
Nevertheless, in the hydrogel state, the rheological properties were
remarkably preserved. Further studies on the cellular compatibility
of all the BTA assemblies and mixtures thereof were performed in four
different cell lines. A low cytotoxic effect at most concentrations
was observed, confirming the suitability of utilizing functional BTA
supramolecular polymers as dynamic biomaterials.
Free-energy profiles, and associated enthalpic and entropic components, providing atomistic-resolution insights into the mechanisms (thermodynamics and kinetics) of the shuttling processes in rotaxanes.
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