Self-Healing Thermoset Polyurethanes Driven by Host–Guest Interactions Between α-Cyclodextrin and Poly(ethylene glycol) Monomethyl Ether or Dodecanol Moieties

Self-healing thermoset polymers have attracted significant attention because they contribute to resource and energy savings by extending their service life. The reactions between glycerol ethoxylate (GCE), <i>α</i>-cyclodextrin (<i>α</i>-CD), poly(ethylene glycol) monomethyl ether (MPEG), and hexamethylene diisocyanate (HDI) at molar ratios of GCE:<i>α</i>-CD:MPEG = <i>a</i>:<i>b</i>:<i>c</i> produced polyurethane networks (GCM-<i>abc</i>, <i>abc</i> = 311, 411, and 511) containing α-CD and MPEG as host and guest moieties, respectively. To compare this with GCM-411, 1-dodecanol (DN) was used instead of MPEG as a guest molecule to yield a polyurethane network (GCD-411). Dynamic mechanical analysis revealed the formation of a polymer network, and the loss tangent (tan <i>δ</i>) peak temperature (<i>T</i>_α) and crosslinking density (<i>ν</i>_e) decreased with increasing GCE fraction for GCMs, and the <i>T</i>_α and <i>ν</i>_e values of GCD were slightly higher than those of GCM-411. The tensile strength of the GCMs decreased with increasing GCE fraction, and the tensile strength of GCD-411 was slightly higher than that of GCM-411. All cured films were healed at room temperature for 24 h, and the healing efficiency (<i>η</i>_σ), based on tensile strength, increased in the order of GCM-311 < GCM-411 < GCM-511 < GCD-411. When the healing temperature increased from room temperature to 80 °C, <i>η</i>_σ increased from 24-38% to 45-62%. GCM-411 and GCD-411 were self-healed thrice by treatment at 80 °C, and <i>η</i>_σ gradually decreased with each healing cycle.