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摘要
Polyurethane elastomers (PUEs) not only have high intrinsic dielectric constants, but also possess repeated deformation ability due to their crosslinking structure, so the conventional cross-linked PUE is often used as a dielectric elastomer. However, cross-linked PUEs cannot be reprocessed or heal as this will lower their use efficiency. Although the introduction of dynamic covalent bonds can solve this problem, it is a great challenge to design dynamic covalent cross-linked PUEs with excellent dielectric properties. Based on this consideration, ketal with two hydroxyl groups obtained by the reaction of 2,5-hexanedione and glycerol is used as a chain extender to prepare ketal-containing dynamic covalent cross-linked PUE. Cyclic ketal contains polar C-O bonds, and its asymmetric structure can weaken the interactions between hard segments in polyurethane, which enhance the orientation of polar groups, thus improving the dielectric properties. Moreover, the ketal-containing cross-linked PUE is capable of self-healing, reshaping, and reprocessing owing to the reversible heat exchange of ketal. Thus, the ketal-containing PUE exhibits reprocessability and excellent dielectric properties (a dielectric constant of 11.9 and a dielectric loss factor of 0.045 at 10(3) Hz). In addition, the ketal-containing cross-linked PUE has better water resistance. This study provides a way to obtain dynamic covalent cross-linked PUEs with excellent dielectric properties.
