Self-Healing Polymer Films Based on Thiol–Disulfide Exchange Reactions and Self-Healing Kinetics Measured Using Atomic Force Microscopy

Abstract

Self-healing polymeric materials with branched architectures and reversible cross-linking functionalities at the periphery of branches were synthesized by atom transfer radical polymerization (ATRP). Poly(n-butyl acrylate) grafted star polymers were prepared by chain extension ATRP from cross-linked cores comprised of poly(ethylene glycol diacrylate). These polymers were further used as macroinitiators for the consecutive chain extension ATRP of bis(2-methacryloyloxyethyl disulfide) (DSDMA), in which way disulfide reversible cross-links (SS) were introduced at the branch peripheries. The SS cross-linked polymers were then cleaved under reducing conditions to form thiol (SH)-functionalized soluble star polymers. The SH-functionalized star polymer solutions were deposited on silicon wafer substrates and converted to insoluble SS re-cross-linked films via oxidation. The self-healing of prepared polymer films was studied by continuous atomic force microscopy (AFM) imaging of cuts micromachined with the AFM tip and by optical microscopy. The re-cross-linked star polymer (X3) showed a rapid spontaneous self-healing behavior, with the extent of healing dependent on the initial film thickness and the width of the cut. The self-healing behavior observed for this sample was attributed to the regeneration of SS bonds via thiol–disulfide exchange reactions. This study demonstrated the suitability of grafted multiarm polymer architectures as building blocks of self-healing polymeric materials and pointed to the importance of low intrinsic viscosity of material and high accessibility of functional groups responsible for healing.

Transiently malleable multi-healable hydrogel nanocomposites based on responsive boronic acid copolymers

“…Notable approaches of this method include the construction of healable polymer networks based on the exploitation of hydrogen bonds, [9][10][11] π-π stacking type of interactions, 12,13 host-guest recognition events, [14][15][16][17] electrostatic interactions, 18,19 metal coordination, [20][21][22] acylhydrazones, 23,24 reversible (hetero) Diels-Alder reaction motifs [25][26][27][28] and disulfide bonds. [29][30][31] Indeed, all these approaches have their own merits, however, the healing process is not always ex vi termini perfect as autonomous/automatic healing must be accompanied by gravitational force or mechanical/manual rejoining of the damaged material. In this regard, remotely controlled healing strategies allow for on-demand repairing of the material at the site of interest, although the need for mechanical intervention is not completely eliminated.…”

Recent Advances in the Anionic Photocurable Epoxy/Thiol-Ene Systems

“…Both extrinsic and intrinsic method have been tested [11]. One of the intrinsic approaches to achieving self healing properties is by introducing functional groups in the polymer that can undergo dynamic Exchange reactions between reversible covalent bonds, Several photochemical reactions have been used such as the DielsAlder reaction, cycloaddition reaction [2+2], cycloadditions [4+4], exchange reaction of siloxanes segments, and disulfide exchange to name a few examples [12]. In our epoxy/thiolene systems, given that a tetrafunctional thiol was used, it was thought that disulfide bonds could be introduced in the polymer if the tetrafunctional thiol was partially oxidized, generating an oligomer with both thiol and disulfide bonds [13].…”

Self-healing Hydrogels Based on Dynamic Chemistry and Their Biomedical Applications

“…例如, 基于可逆二硫键的多 臂高分子 [38] 、光引发修复的三硫代碳酸酯交联网络结 构 [39] 、紫外光修复的壳聚糖-聚氨酯复合材料 [40,41] 、热 引发修复的 Diels-Alder 化学交联结构及基于自由基交 换引发愈合的凝胶材料 [42,43] . 虽然一部分文献中的条件变化是 温和的 [48,49] , …”