Elastic-Modulus-Dependent Macroscopic Supramolecular Assembly of Poly(dimethylsiloxane) for Understanding Fast Interfacial Adhesion

Abstract

Macroscopic supramolecular assembly (MSA) is a new concept of supramolecular science with an emphasis on noncovalent interactions between macroscopic building blocks with sizes exceeding 10 μm. Owing to a similar noncovalently interactive nature with the phenomena of bioadhesion, self-healing, etc. and flexible features in tailoring and designing modular building blocks, MSA has been developed as a simplified model to interpret interfacial phenomena and a facile method to fabricate supramolecular materials. However, at this early stage, MSA has always been limited to hydrogel materials, which provide flowability for high molecular mobility to the interfacial binding. The extension to a wide range of materials for MSA is desired. Herein, we have developed a strategy of adjusting intrinsic properties (e.g., elastic modulus) of nonhydrogel materials to realize MSA, which could broaden the material choices of MSA. Using the widely used elastomer of poly­(dimethylsiloxane) (PDMS) as building blocks, we have demonstrated the elastic-modulus-dependent MSA of PDMS based on the host/guest molecular recognition between supramolecular groups of β-cyclodextrin and adamantane. In the varied elastic modulus range of 0.38 to 3.84 MPa, we obtained the trend of the MSA probability decreasing from 100% at 0.38 MPa to 0% at 3.84 MPa. Meanwhile, in situ measurements of interactive forces between PDMS building blocks have supported the observed assembly phenomena. The underlying reasons are interpreted with the low-modulus flexible surfaces favoring for high molecular mobility to achieve interactions between multiple sites at the interface based on the theory of multivalency. Taken together, we have demonstrated the feasibility of directly adjusting the modulus of bulk materials to realize MSA of nonhydrogel materials, which may provide clues to the fast wet adhesion and new solutions to the additive manufacture of elastomer materials.

Self-sorting in macroscopic supramolecular self-assembly via additive effects of capillary and magnetic forces

“…1d ). To obtain free-standing stable assemblies immediately after the capillary-driven assembly, we applied the previously developed concept of ‘flexible spacing coating’ beneath the charged groups to facilitate the multivalent binding upon rapid contacting 29 , 39 – 41 . This coating was made from the composite polyelectrolyte multilayers (Fig.…”

“…The magnetic force was measured during the dynamic approaching process of A-B with a force apparatus shown in (Supplementary Fig. 6 ) 41 . The measurement was conducted by a cycled contact-separation process between A-B, during which the force changes exerted on A and the distance that B had been moved were in situ recorded.…”

Supramolecular Polymerization at Interfaces

“…In addition to common organic solvents, the ionic liquids and supercritical fluids can also form stable interfaces with aqueous solution, which could also be designed for constructing supramolecular polymers with novel architectures. Furthermore, interfaces other than the ones mentioned, such as gas–liquid, solid–solid, gel–gel, and gel–solution, could also be used . We anticipate the development of new supramolecular polymerization methods at different interfaces for the construction of supramolecular polymeric materials with diverse architectures and tailored functions to enrich the realm of molecular engineering of functional supramolecular systems.…”

Sunlight Recovering the Superhydrophobicity of a Femtosecond Laser-Structured Shape-Memory Polymer

“…These biological organisms can always maintain vigorous vitality by the self-growth process even if they are damaged by external forces. Among them, the special superwetting surfaces such as the self-cleaning effect of lotus leaves, the directional sliding of rice leaves, the water-walking capability of water striders, and the directional adhesion of butterfly wings have allured continuous attentions for researchers. − The cutting edge in development of artificial superhydrophobic surfaces is first inspired by the lotus leaf . Due to the dual action of hierarchical micro/nanostructures and low-surface-energy wax materials, the water droplets display ultrahigh contact angle and ultralow sliding angle on the surface of the lotus leaf. , On the basis of the excellent liquid-repellent property, artificial superhydrophobic surfaces are extremely attractive in the fields of self-cleaning, anti-fouling, and heat transfer. − For example, the water droplet on the superhydrophobic surface can stay nearly in a spherical state with high mobility and minimal droplet adhesion and thus can easily remove dirt particles and other contaminants sitting on the sample surface and also effectively enhance condensation performance. , However, one of the major problems of the artificial superhydrophobic surface in practical applications is the poor durability. , For instance, the hierarchical micro/nanostructures of the artificial superhydrophobic surfaces are easily damaged by mechanical actions, thus resulting in the permanent loss of surface superhydrophobicity. , …”