Using Molecules with Superior Water-Plasticity to Build Solid-Phase Molecular Self-Assembly: Room-Temperature Engineering Mendable and Recyclable Functional Supramolecular Plastics

Abstract

The brittleness of many supramolecular films in a dry environment has prevented their further application as supramolecular plastics. We report here the fabrication of supramolecular plastics displaying excellent dry-flexibility and mechanical strength through room-temperature solid-phase molecular self-assembly using water-locking polyelectrolyte and surfactant. Aided by mild mechanical pressure of about 0.5 MPa, the locked water enables the polyelectrolyte-bridged surfactant microdomains to merge into large mesophases to reduce the interface energy, which yields a transparent supramolecular film. The film still contains 2% water in a dry environment, which is capable of plasticizing the polyelectrolyte and surfactant; thus, it imparts excellent flexibility to the film. The dry film has a stress of 12 MPa and Young's modulus of 188 MPa with a strain of 24%. This mechanical strength is comparable to that of the commercial soft polyethylene plastics. Since the noncovalent interactions in the film can be activated by water under mild mechanical pressure within seconds, mending a broken film by pressing a wet patch with mild mechanical force onto the damage becomes possible. Complete recycling can be achieved under the same conditions. We envision the current roomtemperature mechanical force driven water-based recyclable and mendable supramolecular plastics would be very promising in reducing white pollution and generating integrated materials.

Physical Insight into the Conditions Required in the Solid-Phase Molecular Self-Assembly of SDS Revealed by Coarse-Grained Molecular Dynamics Simulation

“…Recently, Yan et al found that molecules in the precipitates formed with the aqueous mixture of ionic surfactant and oppositely charged polyelectrolyte may undergo self-assembly to form large-area self-supporting films under pressure in the presence of a tiny amount of water. − The driving forces for the multiscale self-assembly process are mainly the hydrophobic interaction between surfactant molecules. The electrostatic interaction between the polyelectrolyte chain and surfactant molecules is to endow the film with the self-supporting ability through the cross-linking of nanodomains formed by surfactants.…”

“…However, so far most molecular self-assemblies are obtained in the form of solution-based colloidal dispersions. − This solution-based molecular self-assembly is hard to work with when bulk macroscopic materials are required . To tackle this problem, we recently developed a strategy of solid-phase molecular self-assembly (SPMSA), − with which supramolecular films can be obtained at large scales . This not only allows the preparation of noncolloidal form self-supporting macroscopic molecular self-assembled materials but also makes it possible to achieve diversified functions. − ,, …”

“…To tackle this problem, we recently developed a strategy of solid-phase molecular self-assembly (SPMSA), − with which supramolecular films can be obtained at large scales . This not only allows the preparation of noncolloidal form self-supporting macroscopic molecular self-assembled materials but also makes it possible to achieve diversified functions. − ,, …”

“…It was previously found that nanoscaled preassembled structure, pressure, and a small amount of water are the necessary factors for the SPMSA. − To gain more physical insights into the mechanism of the SPMSA across multiple time and space scales, in this study, we employ molecular dynamics (MD) simulations in combination with the experiment to reveal the micropictures obtained during the complicated self-assembly process. According to the time and space scale, MD simulation can be divided into quantum MD simulation (QM), all-atom (AA) MD simulation, and coarse-grained (CG) MD simulation.…”

“…Sodium dodecyl sulfate (SDS) is widely applied in many commercial cleaning products, such as soaps, toothpaste, etc . It is also used for DNA and protein extraction in polyacrylamide gel electrophoresis.…”