Liquid crystal trimers containing secondary amide groups

Figures & data

Figure 1. (Colour online) (a) A sketch of the molecular arrangement in the a) nematic phase, showing the director, n; (b) lamellar smectic A phase; (c) twist-bend nematic phase showing the formation of degenerate helices.

Figure 2. The structures of the trimers discussed here.

Table 1. Transition temperatures and the associated enthalpy and entropy changes for the trimers shown in Figure 2. Monotropic transition temperatures are shown in ().

		Melt	SmX	SmCA	SmA	NTB	N
1	T /°C	147				• (104)^†	• (144)^†
	ΔH/kJ mol^−1	28.67				• 0.44^†	• 1.58^†
	ΔS /R	8.21				• 0.14^†	• 0.46^†
2	T /°C	175		• (168)^†			• 298
	ΔH/kJ mol^−1	24.63		• 2.40^†			• 4.86
	ΔS /R	6.61		• 0.65^†			• 1.02
3	T /°C	162		• (152)^†	• 186		• 283
	ΔH/kJ mol^−1	67.60		• 0.30^†	• 0.29		• 5.07
	ΔS /R	18.56		• 0.09^†	• 0.08		• 1.10
4	T /°C	138				• 145^‡	• 267
	ΔH/kJ mol^−1	52.08					• 5.41
	ΔS /R	14.83					• 1.21
5	T /°C	235	• (199)^†				• 298
	ΔH/kJ mol^−1	39.71	• 1.34^†				•  2.26
	ΔS /R	9.33	• 0.34^†				• 0.47
6	T /°C	191					• 254
	ΔH/kJ mol^−1	27.29					• 3.06
	ΔS /R	7.07					• 0.63
7	T /°C	185		• 199			• 296
	ΔH/kJ mol^−1	31.30		• 3.26			• 4.31
	ΔS /R	8.22		• 0.83			• 0.91

^†Denotes values taken from DSC cooling trace. ^‡ Denotes value taken from POM.

Figure 3. (Colour online) The change in the optical birefringence of trimer 1 on cooling. (Inset left): the striped POM texture of the N_TB phase shown by 1 in a cell treated for planar alignment at 98°C. (Inset right): the schlieren texture seen for 1 in the nematic phase at 127°C on untreated glass.

Figure 4. (Colour online) (a) POM texture of trimer 2 in the SmC_A phase at 155°C on untreated glass with (inset) the schlieren texture seen upon shearing of the sample; (b) the X-ray diffraction pattern seen for 2 at 155°C; (c) truncated fan-like texture of the SmA phase of trimer 3 on untreated glass at 171°C and (inset) optically extinct texture on untreated glass; (d) the banded fan-like texture of the SmC_A phase for trimer 3 on untreated glass at 136°C with (inset) the schlieren texture seen upon shearing; (e) the rope-like texture of the N_TB phase of trimer 4 at 125°C on untreated glass; (f) the X-ray diffraction pattern of trimer 4 in the N_TB phase at 120°C.

Figure 5. (Colour online) The temperature dependence of optical birefringence of trimers 2 and 4 on cooling.

Figure 6. (Colour online) The layer spacing in the smectic phases and local periodicity detected in the nematic phase of trimer 3, with sketches showing the packing of trimers in the SmC_A and SmA phases.

Figure 7. The shift in the amide (I) band maxima for trimer 2 on cooling.

Figure 8. (Colour online) AFM picture of 4 recorded in QNM mode, height, showing stripes. Inset FFT analysis of the height picture, based on the FFT d spacing is calculated.

Figure 9. (Colour online) (a) The appearance of bâtonnets from the N phase at 198°C for compound 5; (b) the focal conic fan and (inset) schlieren textures seen on untreated glass at 196°C for the lower temperature phase of 7.

Figure 10. (Colour online) The molecular electrostatic potential surface for trimer 1.

Table 2. Transition temperatures of trimers with benzanilide, benzylideneaniline, and biphenyl-based central mesogenic groups.