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The reaction of β-cyclodextrin (β-CD) and bromoacetic acid in the presence of potassium hydroxide produced a carboxymethylated β-CD (CMβCD) with a substitution degree of 3.0. Thermal curing reactions of sorbitol polyglycidyl ether with CMβCD, cyclohexanecarboxylic acid, and poly(ethylene glycol) bis(carboxymethyl) ether (PEGBC) at 1/1 epoxy/carboxylic acid molar ratios produced carboxylic acid-cured epoxy networks (SCCPB) incorporating the cyclodextrin-cyclohexane host–guest moieties. The FT–IR and gel fraction measurements for the cured products revealed that polymer networks were formed by the reaction between epoxy and carboxy groups. With increasing PEGBC content, the glass transition temperature (Tg), tensile strength, and tensile modulus of SCCPB films decreased. SCCPB films with relatively high PEGBC contents demonstrated self-healing properties after being treated at room temperature for 30 s, whereas SCCPB films with relatively low PEGBC contents did not. The SCCPB film with the highest PEGBC content exhibited an excellent healing efficiency (98%) based on the recovery rate of the tensile strength, when healed at 60 °C for 24 h. [ABSTRACT FROM AUTHOR]

Urethanization of castor oil (CO), β-cyclodextrin (CD), and 1-adamantanol (AdOH) with hexamethylene diisocyanate (HDI) at a CD/AdOH molar ratio of 1:1 and various feed CO fractions produced castor oil-based polyurethane network films (CAPUs) incorporating cyclodextrin and adamantane units as host and guest components, respectively. For comparison, similar urethanization reactions were performed with CO/CD/HDI and CO/AdOH/HDI to produce network films that lacked guest or host moieties (CDPU and ADPU, respectively). The results of Fourier transform infrared spectroscopy and gel fraction measurements confirmed the formation of polyurethane networks. The glass transition temperatures, tensile strengths, and tensile moduli of the network films increased with decreasing CO fractions. All CAPU films demonstrated healing properties at room temperature; however, the CDPU and ADPU films did not. The healing efficiency also increased with decreasing CO fraction. [ABSTRACT FROM AUTHOR]

An aminated β-cyclodextrin (NCD) with an amine substitution degree of 16.4 was prepared through the thiol–ene reaction of allylated β-cyclodextrin and cysteamine hydrochloride. The thermal curing reactions of sorbitol polyglycidyl ether (SPE) with NCD, Jeffamine® ED-600 (JA, an aliphatic polyether amine), and adamantylamine (NAD) with a feed epoxy/NH2 ratio of 1:1 and feed NH2 molar ratios of NCD/JA/NAD = 1/1/1 and 1/2/1 produced epoxy-amine networks. The FT-IR and gel fraction measurements for the cured products revealed that polymer networks were formed by the reaction of epoxy and amino groups. The cured product with a higher JA content showed lower glass transition temperature (Tg), tensile strength, and tensile modulus results than those of the cured product with a lower JA content. Compared with the product with lower JA, the product with higher JA exhibited self-healing properties upon treatment at 60 °C. The self-healing driven by the NCD/NAD host–guest interaction was demonstrated as the self-healed sample returned to its original state after immersion in an ethanol solution of NAD. Moreover, the corresponding SPE/NCD/JA and SPE/JA/NAD cured products did not exhibit self-healing capacity. [ABSTRACT FROM AUTHOR]

To increase the durability and reliability of thermosets, self-healing via a vascular network, is developed. A judicious choice of healing agents proves to be necessary to achieve the best recovery of properties. Four low viscosity two-component epoxy-amine healing systems were compared, to check which glass transition temperature range would be best to recover mechanical properties (T g ranging from −8 to 68 °C). Interdiffusion experiments show that all systems react sufficiently slowly at room temperature to allow interdiffusion of epoxy and amine over more than 1 mm before the diffusion is stopped by vitrification. Swelling tests revealed that most of the selected healing agents diffuse into the surrounding matrix and swell it. This might be beneficial for crack closure and improved adhesion between healing system and matrix. Flexural tests demonstrated that, the higher the glass transition temperature of the fully cured healing system, the higher the healing capability. [ABSTRACT FROM AUTHOR]

Abstract: Healing of epoxy resins can be accomplished using a combination of embedded ethyl phenylacetate (EPA) solvent loaded capsules and shape memory alloy (SMA) wires. Upon crack formation, the EPA solvent diffuses in the resin and induces swelling which tends to close the crack, while the SMA wires upon heating reduce the crack gap and foster residual epoxy cure. The kinetics of EPA diffusion in the epoxy matrix were measured so as to evaluate the swelling thickness versus time, and concentration at saturation. The largest healable crack gap was found to be 30 μm after 24 h. EPA solvent was shown to lower the curing reaction kinetics and the glass transition temperature (Tg ) of the epoxy, as well as its stiffness and strength. Healing efficiency was assessed using long-groove tapered double cantilever beam (TDCB) test samples, with embedded SMA wires across the crack plane. The healing efficiency greatly improved when the crack gap was reduced to 30 μm, from 24% for samples without SMA wires to 78% for samples with SMA wires activated according to an optimized scenario. [Copyright &y& Elsevier]