Role of New Chiral Additives on Physical-Chemical Properties of the Nematic Liquid Crystal Matrix.

We have synthesized and studied three new chiral substances as additives to a nematic liquid crystal. The difference in the optical activity and chemical structure of additive molecules results in the appearance of the chiral nematic phase and the change in both the compatibility of the mixture components and temperature range of the liquid crystal phase. The role of additives with fundamentally different structures and optical activities is shown. The increase in the TNI that is observed in mixtures with 4-[(2S)-(+)-2-Methylbutoxy]benzoic acid indicate the possibility of the increase in order caused by the formation of molecularly rigid and elongated dimers of the additive, which was confirmed using infrared spectra. The doping of the nematic liquid crystal with (2R)-(+)-2-[4-[2-Chloro-4-(4-hexylphenyl)phenyl]phenoxy]propanoic acid causes the lowering of TNI. The binol derivative S-(+)-6-[1-[2-(5-Carboxypentoxy)naphthalen-1-yl]naphthalen-2-yl] oxyhexanoic acid has the highest chirality among the additives used. One can explain the effects observed in terms of the role of size, shape, and compatibility with the nematic matrix as shown by the molecules that are used as additives.

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.