Surface Hydrophobization Provides Hygroscopic Supramolecular Plastics Based on Polysaccharides with Damage‐Specific Healability and Room‐Temperature Recyclability

Abstract

concern over the global plastic pollution. [1][2][3][4][5][6][7] These supramolecular materials are considered to effectively extend service life and improve recycling rate through readily repairing and reprocessing, which will make significant contribution to realize a sustainable society. [8][9][10][11] Different from the traditional plastics based on extremely stable covalent bonds and crosslinks, supramolecular plastic materials incorporate weak intermolecular interactions such as ionic interactions, [12][13][14] hydrogen bonds [5][6][7][8][15][16][17][18] and coordination interactions, [19][20][21][22] which have been wellestablished to achieve self-healing and reprocessing due to the reversible and dynamic nature of weak supramolecular forces. [23] It should be noted that these weak interactions are generally polar and vulnerable to water. [24][25][26][27] In many cases, the essence of efficient self-healing and reprocessing for supramolecular polymeric materials are ascribed to the readily water absorption and water-induced plasticization, which results in strongly self-adhering. [28][29][30][31][32] However, the waterassisted self-adhering process occurs nonspecifically at the damage sites. Undesired self-adhesion generally occurs beyond the damaged sites when the ambient humidity gets high or the materials are exposed to water, which makes the storage and use demand harsh dry condition. Thus, to eliminate undesired self-adhesion, Supramolecular materials with room-temperature healability and recyclability are highly desired because they can extend materials lifetimes and reduce resources consumption. Most approaches toward healing and recycling rely on the dynamically reversible supramolecular interactions, such as hydrogen, ionic and coordinate bonds, which are hygroscopic and vulnerable to water. The general water-induced plasticization facilitates the healing and reprocessing process but cause a troubling problem of random self-adhesion. To address this issue, here it is reported that by modifying the hygroscopic surfaces with hydrophobic alkyl chains of dodecyltrimethoxysilane (DTMS), supramolecular plastic films based on commercial raw materials of sodium alginate (SA) and cetyltrimethylammonium bromide (CTAB) display extraordinary damagespecific healability. Owing to the hydrophobic surfaces, random self-adhesion is eliminated even under humid environment. When damage occurs, the fresh surfaces with ionic groups and hydroxyl groups expose exclusively at the damaged site. Thus, damage-specific healing can be readily facilitated by waterinduced plasticization. Moreover, the films display excellent room-temperature recyclability. After multiple times of reprocessing and re-modifying with DTMS, the rejuvenated films exhibit fatigueless mechanical properties. It is anticipated that this approach to damage-specific healing and room-temperature recycling based on surface hydrophobization can be applied to design various of supramolecular plastic polysaccharides materials for building sustainable societies.

Effect of the Molecular Weight of Polyelectrolyte and Surfactant Chain Length on the Solid-Phase Molecular Self-Assembly

“…This not only allows the preparation of noncolloidal form self-supporting macroscopic molecular selfassembled materials but also makes it possible to get diversified functions. 23,24,26,[28][29][30]32,33,35 However, we found that the film formation ability and the resultant mechanical strength of the film depend highly on the surfactant and polyelectrolyte structure, in particular, the surfactant chain length and the molecular weight of the PE. In order to reveal the physical insight behind this effect, herein, we report a systematic study of the films formed with sodium alkyl sulfates and poly dimethyl diallyl ammonium chloride (PDDA).…”

“…Under mild mechanical pressure and in the presence of physically adsorbed water to facilitate molecular rearrangement, the caking in the PE/surfactant precipitates leads to a self-supporting supramolecular film, where the surfactant bilayers were bridged by the PE chains to form continuous macroscopic structures. This not only allows the preparation of noncolloidal form self-supporting macroscopic molecular self-assembled materials but also makes it possible to get diversified functions. ,,,− ,,, However, we found that the film formation ability and the resultant mechanical strength of the film depend highly on the surfactant and polyelectrolyte structure, in particular, the surfactant chain length and the molecular weight of the PE. In order to reveal the physical insight behind this effect, herein, we report a systematic study of the films formed with sodium alkyl sulfates and poly dimethyl diallyl ammonium chloride (PDDA).…”

“…Inspired by this phenomenon, recently, our group postulated the strategy of solid-phase molecular self-assembly (SPMSA), − which elegantly utilizes the caking tendency of particles in precipitates formed with molecules with self-assembly ability, in particular, precipitates formed with a surfactant and an oppositely charged polyelectrolyte (PE) . Under mild mechanical pressure and in the presence of physically adsorbed water to facilitate molecular rearrangement, the caking in the PE/surfactant precipitates leads to a self-supporting supramolecular film, where the surfactant bilayers were bridged by the PE chains to form continuous macroscopic structures.…”

Permanently Mechanically Adjustable Photothermal Catalytic Spontaneous Double Cross‐Linking Network Enables Durable and Stretchable Plant Skin‐Like Materials

“…However, it improved flexibility. [35] Nevertheless, plastics repaired by hot-pressing exhibited slight improvements in mechanical properties, which was due to further ester exchange reactions and component densification. The re-processability and reparability of supramolecular biomaterials can effectively extend their lifespan and use time, while wastes can be closed-loop recycled, making them more sustainable, as shown in Figure 5f.…”

An Ultrahighly Stretchable and Recyclable Starch‐Based Gel with Multiple Functions

“…[7] In particular, gels often lack recycling performance, which does not meet the needs of sustainable development with the growing concern over global pollution. [8] Covalently crosslinked rigid networks generally fail to be recycled. However, the mechanical properties of the reversible noncovalent bond network are not ideal.…”