Effect of an n-Alkoxy-2,4-hexadiene Polymerizable Tail System on the Mesogenic Properties and Cross-Linking of Mono-Imidazolium-Based Ionic Liquid Crystal Monomers

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• 作者：Lily A. Robertson ; Douglas L. Gin
• 刊名：ACS Macro Letters
• 出版年：2016
• 出版时间：July 19, 2016
• 年：2016
• 卷：5
• 期：7
• 页码：844-848
• 全文大小：303K
• 年卷期：0
• ISSN：2161-1653

文摘

We demonstrate that an ether-based n-alkoxy-2,4-hexadiene polymerizable tail system is an effective and modular alternative to traditional ester-based polymerizable tail groups (i.e., acrylate, methacrylate, sorbate) and alkyl-1,3-diene tails for the design of radically polymerized ionic liquid crystal (ILC) monomers. Several series of nonsymmetric 1-vinylimidazolium-bromide-based ILC monomers containing these different polymerizable tail systems were synthesized and compared for their ability to form thermotropic liquid crystal (TLC) phases and to be photo-cross-linked with TLC phase retention. The n-alkoxy-2,4-hexadiene tail system was found to be more favorable/conducive to TLC phase formation than acrylate, methacrylate, and sorbate tails. It was more similar to the alkyl-1,3-diene tail system in terms of its more favorable effect on TLC behavior; however, it is more modular/easier to synthesize, more resistant to thermal Diels–Alder side reaction, and more isomerically pure, making it better for ILC monomer design. Also, the n-alkoxy-2,4-hexadiene tail system was found to be very amenable to radical photo-cross-linking with TLC phase retention. To demonstrate this feature, an example cross-linkable ILC monomer with this tail system was synthesized and polymerized in the smectic A TLC phase, and the monomer and polymerized material were characterized for their ionic conductivity behavior.