Assembling a Natural Small Molecule into a Supramolecular Network with High Structural Order and Dynamic Functions

Abstract

Programming the hierarchical self-assembly of small molecules has been a fundamental topic of great significance in biological systems and artificial supramolecular systems. Precise and highly programmed self-assembly can produce supramolecular architectures with distinct structural features. However, it still remains a challenge how to precisely control the self-assembly pathway in a desirable way by introducing abundant structural information into a limited molecular backbone. Here we disclose a strategy that directs the hierarchical self-assembly of sodium thioctate, a small molecule of biological origin, into a highly ordered supramolecular layered network. By combining the unique dynamic covalent ring-opening-polymerization of sodium thioctate and an evaporation-induced interfacial confinement effect, we precisely direct the dynamic supramolecular self-assembly of this simple small molecule in a scheduled hierarchical pathway, resulting in a layered structure with long-range order at both macroscopic and molecular scales, which is revealed by small-angle and wide-angle X-ray scattering technologies. The resulting supramolecular layers are found to be able to bind water molecules as structural water, which works as an interlayer lubricant to modulate the material properties, such as mechanical performance, self-healing capability, and actuating function. Analogous to many reversibly self-assembled biological systems, the highly dynamic polymeric network can be degraded into monomers and reformed by a water-mediated route, exhibiting full recyclability in a facile, mild, and environmentally friendly way. This approach for assembling commercial small molecules into structurally complex materials paves the way for low-cost functional supramolecular materials based on synthetically simple procedures.

An Ultrastrong and Highly Stretchable Polyurethane Elastomer Enabled by a Zipper‐Like Ring‐Sliding Effect

“…The stress–strain curve in the second cycle was more compliant than that in the first cycle, and the curves tended to be stable after four cycles, indicating that the chain sliding in the supramolecular network occurred mainly in the first cycle. [ 59,60 ] The unloading paths followed the same curve independent of the cycle index. Residual strain was still observed, and the Young's modulus recovered to 21% after 24 h because of the sliding of crosslinked PS rings and the fracture and reformation at new sites of hydrogen bonds leading to a looser network (Figure S21a,b, Supporting Information).…”

Toughening a Self‐Healable Supramolecular Polymer by Ionic Cluster‐Enhanced Iron‐Carboxylate Complexes

“…This large enhancement showed the remarkably toughened mechanical performance of the network after crosslinking by high‐density iron(III)‐carboxylate clusters. The toughening mechanism was attributed to the secondary high‐affinity ionic bonding of the iron(III)‐carboxylate complexes (Figure B) . The toughened poly(TA‐DIB‐Fe) network with an iron(III)‐to‐TA molar ratio of 1/100 exhibited typical rate‐dependent tensile curves (Figure C), in which the sample can be stretched to over 6500 % of original length (Figure D) at a lower strain rate of 20 mm min −1 .…”

“…Polymer materials containing ionic bonds usually exhibit humidity‐responsive properties . The water in the air could enter into the network and hydrate the ionic bonds, resulting in the remarkable decrease in mechanical strength, which might become a disadvantage in practical applications. Surprisingly, the poly(TA‐DIB‐Fe) copolymers crosslinked by high‐density ionic clusters exhibited excellent humidity‐resistance ability, while a reference sample without DIB would be gradually softened and become out‐of‐shape in the air (Figure S5).…”

Toughening a Self‐Healable Supramolecular Polymer by Ionic Cluster‐Enhanced Iron‐Carboxylate Complexes

“…Polymer materials containing ionic bonds usually exhibit humidity-responsive properties. [12] The water in the air could enter into the network and hydrate the ionic bonds, resulting in the remarkable decrease in mechanical strength, [12a] which might become a disadvantage in practical applications. Surprisingly, the poly(TA-DIB-Fe) copolymers crosslinked by high-density ionic clusters exhibited excellent humidityresistance ability, while a reference sample without DIB would be gradually softened and become out-of-shape in the air ( Figure S5).…”