A self-healing polymer network based on reversible covalent bonding

Abstract A self-healing polymer network for potential coating applications was designed based on the concept of the reversible Diels–Alder (DA) reaction between a furan functionalized compound and a bismaleimide. The network allows local mobility in a temperature window from ca. 80 °C to 120 °C by shifting the DA equilibrium towards the initial building blocks. Changing the spacer length in the furan functionalized compound leads to tailor-made properties. Elastomeric model systems were chosen to evaluate the kinetic parameters by Fourier transform infrared spectroscopy. For the DA reaction a pre-exponential factor ln( A DA in kg mol −1  s −1 ) equal to 13.1 ± 0.8 and an activation energy ( E DA ) of 55.7 ± 2.3 kJ mol −1 are found. For the retro-DA reaction, ln( A rDA ) and E rDA are 25.8 ± 1.8 s −1 and 94.2 ± 4.8 kJ mol −1 , respectively. The enthalpy and entropy of reaction are calculated as −38.6 kJ mol −1 and −105.3 J mol −1  K −1 . The kinetic results are validated by micro-calorimetry. Non-isothermal dynamic rheometry provides the gel-point temperature of the reversible network. The sealing capacity is evaluated by atomic force microscopy for micro-meter sized defects. Repeatability of the non-autonomous healing is checked by micro-calorimetry, ruling out side-reactions below 120 °C.

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