Healable shape memory (thio)urethane thermosets
Urethane-thiourethane networks combining shape memory properties and the ability to self-heal under mild temperature conditions via Diels-Alder (DA) chemistry were developed. As a result of the shape recovery effect, no external force was needed to bring the fracture surfaces into intimate contact during the healing process. Four network architectures with DA net-points were evaluated. Two systems were composed of either bismaleimidic or bisfuranic semi-crystallized polycaprolactone chains acting as shape memory switching segments (T-trans = T-m), whereas the other two networks consisted of bis-/trismale-imidic and trisfuranic monomers and displayed glass transitions for initiating shape recovery behaviour (T-trans = T-g). The formation of the DA cross-links, the DA reversibility and shape memory assisted scratch healing of the materials were studied by FTIR and H-1-NMR spectrometry, differential scanning calorimetry, optical microscopy and tensile measurements. The resul...