Fluorescence Detection of Microcapsule-Type Self-Healing, Based on Aggregation-Induced Emission.

An extrinsic self-healing coating system containing tetraphenylethylene (TPE) in microcapsules was monitored by measuring aggregation-induced emission (AIE). The core healing agent comprised of methacryloxypropyl-terminated polydimethylsiloxane, styrene, benzoin isobutyl ether, and TPE was encapsulated in a urea-formaldehyde shell. The photoluminescence of the healing agent in the microcapsules was measured that the blue emission intensity dramatically increased and the storage modulus also increased up to 105 Pa after the photocuring. These results suggested that this formulation might be useful as a self-healing material and as an indicator of the self-healing process due to the dramatic change in fluorescence during photocuring. To examine the ability of the healing agent to repair damage to a coating, a self-healing coating containing embedded microcapsules was scribed with a razor. As the healing process proceeded, blue light fluorescence emission was observed at the scribed regions. This observation suggested that self-healing could be monitored using the AIE fluorescence.

Dual Sulfide-Disulfide Crosslinked Networks with Rapid and Room Temperature Self-Healability.

Polymer-based crosslinked networks with intrinsic self-repairing ability have emerged due to their built-in ability to repair physical damages. Here, novel dual sulfide-disulfide crosslinked networks (s-ssPxNs) are reported exhibiting rapid and room temperature self-healability within seconds to minutes, with no extra healing agents and no change under any environmental conditions. The method to synthesize these self-healable networks utilizes a combination of well-known crosslinking chemistry: photoinduced thiol-ene click-type radical addition, generating lightly sulfide-crosslinked polysulfide-based networks with excess thiols, and their oxidation, creating dynamic disulfide crosslinkages to yield the dual s-ssPxNs. The resulting s-ssPxN networks show rapid self-healing within 30 s to 30 min at room temperature, as well as self-healing elasticity with reversible viscoelastic properties. These results, combined with tunable self-healing kinetics, demonstrate the versatility of the method as a new means to synthesize smart multifunctional polymeric materials.

Dual temperature and thiol-responsive POEOMA-multisegmented polydisulfides: synthesis and thermoresponsive properties.

New thermoresponsive polydisulfides of POEOMA multiblocks linked with disulfide bonds having redox-responsive properties are reported. These POEOMA-multisegmented polydisulfides were synthesized by a new method employing a combined RAFT/aminolysis and reversible thiol-disulfide redox reaction that centers on the synthesis of new disulfide-labeled difunctional RAFT agent. RAFT polymerization proceeded in living fashion, yielding well-defined POEOMA copolymers with middle disulfides and terminal RAFT species. They were then used as precursors for thiol-disulfide polyexchange induced by aminolysis and reductive reaction followed by oxidation: these polydisulfides with different molecular weights and end groups exhibited tunable thermoresponsive properties and thiol-responsive degradation.