Novel Mesogenic Vinyl Ketone Monomers and Their Based Polymers.

In the present research, we have synthesized new vinyl ketone monomers with mesogenic substituents, namely, 8-(3'-chloro-4'-pentyl-[1,1'-biphenyl-4-oxy)oct-1-en-3-one (BVK) and 8-[2'-chloro-4‴-octyl-[1,1':4',1″:4″,1‴-quaterphenyl-4-oxy]oct-1-en-3-one (QVK). The comparison of BVK, QVK, and previously synthesized 8-((4″-((1R,4S)-4-butylcyclohexyl)-2'-chloro-[1,1',4',1″-terphenyl]-4-yl)oxy)oct-1-en-3-one (TVK) has revealed that all of them are able to form crystals, while their ability to exhibit liquid crystalline behavior depends on the number of phenyl substituents attached to the para-position of the phenoxy group and is observed for TVK and QVK only. All of the monomers are able to achieve self-polymerization upon heating and free radical polymerization in bulk or in solution under the action of the common radical initiator AIBN. We have also succeeded in the RAFT polymerization of the synthesized vinyl ketones BVK and TVK using asymmetrical trithiocarbonates. The synthesized poly(vinyl ketones) exhibit LC behavior and are able to undergo photodegradation upon UV irradiation.