Advances and Challenges of Self-Healing Elastomers: A Mini Review

In the last few decades, self-healing polymeric materials have been widely investigated because they can heal the damages spontaneously and thereby prolong their service lifetime. Many ingenious synthetic procedures have been developed for fabricating self-healing polymers with high performance. This mini review provides an impressive summary of the self-healing polymers with fast self-healing speed, which exhibits an irreplaceable role in many intriguing applications, such as flexible electronics. After a brief introduction to the development of self-healing polymers, we divide the development of self-healing polymers into five stages through the perspective of their research priorities at different periods. Subsequently, we elaborated the underlying healing mechanism of polymers, including the self-healing origins, the influencing factors, and direct evidence of healing at nanoscopic level. Following this, recent advance in realizing the fast self-healing speed of polymers through physical and chemical approaches is extensively overviewed. In particular, the methodology for balancing the mechanical strength and healing ability in fast self-healing elastomers is summarized. We hope that it could afford useful information for research people in promoting the further technical development of new strategies and technologies to prepare the high performance self-healing elastomers for advanced applications.

A Dielectric Elastomer Actuator That Can Self-Heal Integrally

Dielectric actuators are prone to be worn or partially damaged when operating at high electric fields. The introduction of self-healing features into dielectric actuators is favorable for extending its life span and security. Although many attempts have been made to produce self-healing dielectric actuators, most of them focus on the healing of either the electrodes or the dielectric layers. A dielectric actuator that exhibits integral self-healing is still unprecedented. Meanwhile, realizing integral self-healing in dielectric actuator is highly challenging because both the electrode and the dielectric layer need to be healed while the interface between the electrode and the dielectric layer should remain unaffected during the healing process. In this paper, we synthesized self-healing polydimethylsiloxane (PDMS) polymers containing different amounts of polyaniline (PANI) (denoted as PDMS-PANI_n, where n represents the weight percentage of PANI) as the dielectric layer and electrode, respectively. PDMS-PANI_2.5 polymer exhibits good dielectric properties (ε = 11.11 at 50 Hz) and was used as the dielectric layer, while PDMS-PANI₂₀ polymer having a high conductivity of 4.5 × 10^-5 S/cm was used as the electrode. As both of them have excellent self-healing ability and are compatible and diffusible to each other, the entire actuator device can still cause actuated strain after cutting and healing at room temperature for 48 h. Our strategy for realizing integral self-healing of actuator is also applicable to other electronic devices.

High-Strength, Fast Self-Healing, Aging-Insensitive Elastomers with Shape Memory Effect

Self-healing materials, which can autonomously repair damages like living organisms, have undergone extensive development in the last decades. The bottleneck problems for their practical applications are long healing time, inferior mechanical strength, and aging sensitivity. Here, a new class of polymeric materials rationally grafted with oligo poly(ethylene glycol) is reported. The network based on the formation of multiple weak hydrogen bonds endows the elastomers with good comprehensive performances including high stretchability (725%), high strength (4.20 MPa), and fast self-healing process (40 s). Benefiting from characteristic multiple weak hydrogen bond interactions, the fractured elastomers maintain high healing efficiency even after aging for 192 h, showing an unusual aging insensitivity. A Sudoku structural device based on the developed elastomer shows shape memory effect, providing a new avenue for fabricating novel smart devices with complicated shapes.

A Self-Healing and Shape Memory Polymer that Functions at Body Temperature

Dual-functional polymeric system combining shape memory with self-healing properties has attracted increasingly interests of researchers, as both of these properties are intelligent and promising characteristics. Moreover, shape memory polymer that functions at human body temperature (37 °C) are desirable because of their potential applications in biomedical field. Herein, we designed a polymer network with a permanent covalent crosslinking and abundant weak hydrogen bonds. The former introduces elasticity responsible and maintain the permanent shape, and the latter contributes to the temporary shape via network rearrangement. The obtained PDMS-COO-E polymer films exhibit excellent mechanical properties and the capability to efficiently self-heal for 6 h at room temperature. Furthermore, the samples turn from a viscous state into an elastic state at 37 °C. Therefore, this polymer has shape memory effects triggered by body temperature. This unique material will have a wide range of applications in many fields, containing wearable electronics, biomedical devices, and 4D printing.

The journey of self-healing and shape memory polyurethanes from bench to translational research

In this critical review, we have enlisted a comprehensive summary of different approaches that have been used over the past decade to synthesize self-healing polyurethanes including “close then heal” and “shape memory assisted self-healing” concept.

Reconfigurable photonic crystals with optical bistability enabled by “cold” programming and thermo-recoverable shape memory polymers

A type of reconfigurable photonic crystals with optically bistable states enabled by capillary pressure-induced programming and heat-caused recoverable shape memory polymers was reported.

Multiple shape memory polymers for self-deployable device

Three-segments MH copolymers with well-separated glass transition temperatures can subsequently change their shapes in a pre-defined way.

Preparation of microcapsules containing multi-functional reactive isocyanate-terminated-polyurethane-prepolymer as healing agent, part II: corrosion performance and mechanical properties of a self healing coating

Stress–strain curves in three modes (intact, scratched and healed) for; (a) neat epoxy and (b) sample containing 5 wt% microcapsules. SEM micrographs of scratched area of; (c) neat epoxy film, and (d) film with 5 wt% microcapsule.