Syntheses of highly twisted helical polyacetylene under nano-order chiral nematic liquid crystal reaction field

We synthesized novel mesogenic axially chiral binaphthyl derivative by substituting phenyl-cyclohexyl (PCH) moieties into 2, 2′, 6 and 6′ positions of binaphthyl rings. The binaphthyl derivative showed the highest twisting power of βM = 381.87 μm−1, when 0.05 mol% of the chiral dopant was added into a mixture of PCH302 and PCH304. The helical pitches of N∗-LC varied from 270 to 350 nm with changes of the concentration of the chiral dopant from 1.5 to 1.0 mol%. These helical pitches are smaller one-tenth than those (2–5 μm) observed in the N∗-LC containing di-substituted binaphthyl derivatives. This indicates that the present N∗-LC including tetra-substituted binaphthyl derivatives is feasible for much higher twisted asymmetric reaction field. It is of interest that the polyacetylene film synthesized in the N∗-LC with helical pitch of 270 nm showed highly screwed fibrils, but not the bundle of fibril. This is due to the fact that the helical pitch of 270 nm is smaller than the diameter of the bundle of fibril. This situation might depress the formation of the bundle of fibril. The fibrillar morphology without the bundle of fibrils should make it much easier to evaluate electromagnetic properties of the screwed fibril.