Vitrimer is a new reprocessable thermosetting polymer based on the exchange of dynamic covalent bonds. However, the vitrimer reported in the literatures can usually be reprocessed at very high temperature, while the vitrimer reprocessed at a relatively low temperature exhibits poor mechanical properties. It is still a great challenge to design mechanically robust vitrimer with a moderate reprocessing temperature. Herein, a polyurethane‐urea vitrimer elastomer including N,N′‐diaryl urea with electron donating effect is first reported, and it possesses a moderately remoldable temperature (100 °C, 23% of soft segments content) and robust mechanic al performance. The associative exchange mechanism of N,N′‐diaryl urea with electron donating effect is investigated by the stress relaxation, variable temperature Fourier transform infrared spectra of elastomer, as well as nuclear magnetic resonance spectra, and Fourier transform infrared spectra based on model compounds. Besides, for the preparation of polyurethane‐urea vitrimer elastomers, all monomers are directly from commercial raw materials, thereby providing a possibility of large‐scale production for the polyurethane‐urea vitrimers.

Transparent self-healing polymers have a promising future, but the research on the relationship among transparency, self-healing, and structure is still challenging. The thermoplastic polyurethane elastomers containing aryl carbamate were prepared by the reaction of isocyanate-terminated prepolymer and chain-extender bisphenol A (BPA). On the one hand, the thermoplastic polyurethane elastomer could heal at a relatively low temperature due to the exchange of aryl carbamate, and exhibits 83% of healing efficiency at 90 C for 2 h. On the other hand, two methyl groups of BPA hinder the crystallization of hard segments in polyurethane, so the domain of hard segments is amorphous, while the microcrystals of soft segments dispersed in the polyurethane are affected by the content of hard segments, therefore, the transparency of polyurethane can be tailored by the content of hard segments. It provides a simple design and a feasible preparation method for transparent self-healing polymer.

Polymers can repair their own mechanical damage and prolong their service life by self-healing, so it has received extensive attention in recent years. But the self-healing polymers through the exchangeable dynamic covalent bonds have relatively poor mechanical performance. The polyurethanes were prepared with poly(tetramethylene ether) glycol (PTMG) as soft segments and 4,4′-diphenylmethane diisocyanate, 1,4-butanediol as hard segments, in the absence of catalyst. The change of carbamate and hydrogen bonding in polyurethane was studied by variable-temperature infrared spectroscopy. The results showed that there were exchangeable dynamic equilibria of above two. The effect of molecular weight of soft segments on the healing efficiency was also discussed. The results showed that the higher molecular weight of soft segments enhanced the microphase separation of polyurethane. It not only provided the high mechanical strength, but also facilitated the reversible exchange of carbamate and hydrogen bonding in the region of the fracture, thus promoting the self-healing effect. The study will provide a healing method for the PTMG-based polyurethane elastomer of scale production.

as the hard segment phase. Montana et al. [14] discovered that the block copolymer PMMA-PBA-PMMA could toughen PMMA up to an elongation at break about 17.5%, but decrease its tensile strength. It can be seen from the above-mentioned literatures that the toughness of PMMA can be greatly improved by introducing inorganic nanofillers, polymers with lower T g , or copolymerization units. However, the methods can cause relatively low strength of polyacrylate, and reduce its transparency at visible light deriving from the presence of phase separation structure. The incorporation of the third or more monomer units into binary polyacrylate can increase the compatibility of original polymers, that is, a narrower T g gap between the soft and hard phases, [16] thereby changing the phase separation structure. [17,18] The particle-brush and star polymers with the core-shell structure are prepared by atom transfer radical polymerization of BA with styrene and acrylonitrile, and then blended with PMMA. [19] The toughness of the blend prepared is better than PMMA, and its transparency is close to that of PMMA. The polymer films prepared by methyl methacrylate, butyl methacrylate, and glycidyl methacrylate exhibit different T g s with the increase of glycidyl methacrylate content, so the phase separation structure was modified and the latex film cast on the glass plate was transparent. [20] It can be seen that the copolyacrylate is still an elastomer and has good visible-light transmittance after the incorporation of the third or more monomer units.The transmittance of elastomer will be significantly reduced after damage, while the self-healing of transparent elastomer can improve its application performance and service life. The self-healing effect derived from dynamic non-covalent interactions, such as hydrogen bonding, [21][22][23] electrostatic, [7] dipoledipole, [3] host-guest, [24,25] intermolecular interactions, [26,27] and so on, can be applied to the transparent elastomer. The copolyacrylate is still an elastomer after the incorporation of the third or more monomer units, which will provide the mobility of molecular chain and contribute to intermolecular interactions, promoting self-healing, but will decrease the mechanical strength of copolyacrylate. So the healing of transparent copolyacrylate elastomer remains to be further studied. [28,29] The copolymerization of BA and MMA can improve the toughness of PMMA, but its transparency is reduced by the phase separation behavior. The glass transition temperature of HEA homopolymer is between those of PMMA and PBA. HEA will be incorporated into the copolymerization system as a third Transparent ElastomersThe contradiction between mechanical properties, transparency, and healing effects for polyacrylate elastomers is not solved yet. The copolyacrylate elastomers are prepared based on the bulk copolymerization with methyl methacrylate (MMA) and butyl acrylate (BA), incorporating the β-hydroxyethyl acrylate (HEA) monomer. Compared with PMMA-co-PBA, with the incorporation of HEA...