Reprocessable polyurethane elastomers based on reversible ketal exchange: dielectric properties and water resistance

• Published in: Journal of materials chemistry. C, Materials for optical and electronic devices Vol. 11; no. 4; pp. 1369 - 138
• Main Authors: Dong, Jianrong, Yan, Hongye, Lv, Xinhai, Wang, Zhenbang, Rao, Zixuan, Zhu, Bailin, Wu, Jun, Zhou, Yu, Chen, Hongxiang
• Format: Journal Article
• Language: English
• Published: Cambridge Royal Society of Chemistry 26.01.2023
• Subjects: Asymmetric structures; Bonding strength; Covalence; Covalent bonds; Crosslinking; Dielectric loss; Dielectric properties; Elastomers; Heat exchange; Hydroxyl groups; Permittivity; Polyurethane resins; Reprocessing; Water resistance
• ISSN: 2050-7526; 2050-7534
• DOI: 10.1039/d2tc04603b

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. The ketal-containing cross-linked polyurethane elastomer exhibits reprocessability and excellent dielectric properties. In addition, it shows good water resistance.