Reversible Assembly of Terpyridine Incorporated Norbornene-Based Polymer via a Ring-Opening Metathesis Polymerization and Its Self-Healing Property

Self-Healing of Polymers and Polymer Composites

This review is devoted to the description of methods for the self-healing of polymers, polymer composites, and coatings. The self-healing of damages that occur during the operation of the corresponding structures makes it possible to extend the service life of the latter, and in this case, the problem of saving non-renewable resources is simultaneously solved. Two strategies are considered: (a) creating reversible crosslinks in the thermoplastic and (b) introducing a healing agent into cracks. Bond exchange reactions in network polymers (a) proceed as a dissociative process, in which crosslinks are split into their constituent reactive fragments with subsequent regeneration, or as an associative process, the limiting stage of which is the interaction of the reactive end group and the crosslink. The latter process is implemented in vitrimers. Strategy (b) is associated with the use of containers (hollow glass fibers, capsules, microvessels) that burst under the action of a crack. Particular attention is paid to self-healing processes in metallopolymer systems.

Preparation of basalt fibers grafted with amine terminated urea-based oligomer and its application in reinforcing conventional glass ionomer cement

The purpose of this study was to improve interfacial interaction between basalt fibers (BF) and glass ionomer cement (GIC) matrix with grafting amine terminated urea-based oligomer (DIEDA) onto the surface of BF. The DIEDA-BF was prepared by the reaction between 3-aminopropyl- triethoxysilane (APS) modified BF with Isophorone diisocyanate (IPDI) and followed with ethylenediamine (EDA). The reaction was repeated to obtain three generations of DIEDA-BF which were marked as DIEDA-BF-G₁, DIEDA-BF-G₂, and DIEDA-BF-G₃, respectively. X-ray photoelectron spectroscopy (XPS) was used to characterize DIEDA-BF. 3D morphology analysis was taken to investigate the variation of BF after being treated with EDA. Three-point bending-test, compressive strength (CS) test, and fracture toughness (FT) were used to evaluate the reinforcement effect of DIEDA-BF on commercial GIC (GC Fuji IX). Water sorption (WS) and solubility (SL) were measured according to the mass variation at fixed time intervals. The changes of flexural strength (FS) and modulus (FM) after water immersion were used to evaluate the water-aging resistance of DIEDA-BF reinforced GIC. Pure GIC and APS reinforced GIC (APS-GIC) were used as double control groups. The XPS analysis indicated that DIEDA was successfully grafted onto the surface of BF. 3D morphology analysis revealed that BF could be corroded in EDA, thus DIEDA-BF-G₃ had lower N content on the surface than DIEDA-BF-G₂. The results of mechanical tests showed that DIEDA-BF-G₁ and DIEDA-BF-G₂ had the best reinforcement effect. The DIEDA-BF-G₁ reinforcement GIC (DIEDA-BF-G₁-GIC) was chosen for WS, SL, and water aging resistance test further. The results showed that all fiber reinforced GICs had higher WS than pure GIC, and the relationship in SL between fiber reinforced GICs and pure GIC varied with immersion time. The FS of DIEDA-BF-G₁-GIC decreased after one week of water immersion, and had no variation after prolonging the immersion time. After three months of water immersion, DIEDA-BF-G₁-GIC still had much higher FS than pure GIC and APS-BF-GIC. DIEDA could improve the interfacial interaction between BF and GIC matrix. After long term of water immersion, DIEDA-BF reinforced GIC still had FS higher than 50 MPa, which even met the ISO requirement in FS for dental resin composite. Therefore, GIC/DIEDA modified BF composite had potential to be used in stress bearing areas in dentistry.

Shape-Memory and Self-Healing Polymers Based on Dynamic Covalent Bonds and Dynamic Noncovalent Interactions: Synthesis, Mechanism, and Application

Shape-memory and self-healing polymers have been a hotspot of research in the field of smart polymers in the past decade. Under external stimulation, shape-memory and self-healing polymers can complete programed shape transformation, and they can spontaneously repair damage, thereby extending the life of the materials. In this review, we focus on the progress in polymers with shape-memory and self-healing properties in the past decade. The physical or chemical changes in the materials during the occurrence of shape memory as well as self-healing were analyzed based on the polymer molecular structure. We classified the polymers and discussed the preparation methods for shape-memory and self-healing polymers based on the dynamic interactions which can make the polymers exhibit self-healing properties including dynamic covalent bonds (DA reaction, disulfide exchange reaction, imine exchange reaction, alkoxyamine exchange reaction, and boronic acid ester exchange reaction) and dynamic noncovalent interactions (crystallization, hydrogen bonding, ionic interaction, metal coordination interaction, host-guest interactions, and hydrophobic interactions) and their corresponding triggering conditions. In addition, we discussed the advantages and the mechanism that the shape-memory property promotes self-healing in polymers, as well as the future trends in shape-memory and self-healing polymers.

Novel Self-Healing Metallocopolymers with Pendent 4-Phenyl-2,2':6',2″-terpyridine Ligand: Kinetic Studies and Mechanical Properties

We report here our successful attempt to obtain self-healing supramolecular hydrogels with new metal-containing monomers (MCMs) with pendent 4-phenyl-2,2′:6′,2″-terpyridine metal complexes as reversible moieties by free radical copolymerization of MCMs with vinyl monomers, such as acrylic acid and acrylamide. The resulting metal-polymer hydrogels demonstrate a developed system of hydrogen, coordination and electron-complementary π–π stacking interactions, which play a critical role in achieving self-healing. Kinetic data show that the addition of a third metal-containing comonomer to the system decreases the initial polymerization rate, which is due to the specific effect of the metal group located in close proximity of the active center on the growth of radicals.

Self-healing and shape memory metallopolymers: state-of-the-art and future perspectives

Recent achievements and problems associated with the use of metallopolymers as self-healing and shape memory materials are presented and evaluated.