Journal
LIQUID CRYSTALS
Volume 45, Issue 13-15, Pages 2341-2351Publisher
TAYLOR & FRANCIS LTD
DOI: 10.1080/02678292.2018.1525503
Keywords
Twist-bend nematic; dimer; intercalated phases; terminal chain
Funding
- National Science Centre (Poland) [2016/22/A/ST5/00319]
- Carnegie Trust for the Universities of Scotland
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The syntheses and characterisation of the first 10 homologues of the 1-(4-cyanobiphenyl-4'-yl)-6(4-alkyloxyanilinebenzylidene-4'-oxy)hexanes (CB6O.Om) are reported. All 10 homologues exhibit nematic, N, and twist-bend nematic, N-TB, phases. In addition, an intercalated, anticlinic smectic C, SmCA, phase is observed for m = 3-5. A second smectic phase is seen for m = 4,5 but for which no structural information was obtained. For short chain lengths, the local packing in the nematic phases is an intercalated arrangement. As the chain length increases monolayer fluctuations are observed in both nematic phases. The N-TB-N and N-isotropictransition temperatures exhibit a weak odd-even effect as m is increased in which even members show the higher values. This behaviour is accounted for in terms of the change in shape anisotropy and the dilution of the interactions between the mesogenic units on increasing m. The N-I transition temperature falls faster than the N-TB-N temperature on increasing m suggesting that the dilution of the interactions between the mesogenic groups has a smaller effect on the shape-driven N-TB-N transition than on N-I. Increasing the terminal chain length does not strongly promote smectic behaviour for the CB6O.Om series. This is attributed to the difficulties associated with packing these bent molecules into smectic arrangements. [GRAPHICS] .
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