Phase transitions from density and order parameter from polarisabilities in symmetric dimeric liquid crystals

Figures & data

Plate 1: Focal conic fan texture of smectic – A phase in 5.O7O.5 symmetric DLC.

Figure 1. DSC heating and cooling curves of 3.O7O.3.

Figure 2. DSC heating and cooling curves of 5.O11O.5.

Table 1. The transition temperatures, the heats of transition in heating and cooling cycles from DSC and the transition temperatures from POM in cooling cycle of the compounds.

Compound	Phase variant	Method		I–N	N–A	N/A–K
3.O7O.3	N	DSC	Heating	423.0			393.7
			ΔH (J/g)	1.74			51.71
			Cooling	419.9			381.6
			ΔH (J/g)	1.07			37.58
		TM	Cooling	419.9			397.0
3.O11O.3	N	DSC	Heating	409.6		385.4	378.8
			ΔH (J/g)	0.75		38.47	19.20
			Cooling	407.9			375.0
			ΔH (J/g)	0.84			52.58
		TM	Cooling	407.9			382.0
5.O7O.5	NA	DSC	Heating	407.4	–		389.6
			ΔH (J/g)	2.41	–		72.40
			Cooling	405.4	403.7		374.1
			ΔH (J/g)	–*	–*		66.42
		TM	Cooling	407.9	392.0		388.2

*Indicates ΔH values are not calculated for NSmA transitions because of nearest values.

Table 2. The phase variants exhibited by different compounds of DLCs in this series along with analogous monomers, namely nO.m compounds.

Dimeric compound	Phase variant	Monomeric compound	Ref.	Phase variant	Ref.
3.O7O.3^a	N	7O.3			[17]
3.O8O.3^2	N	8O.3	[2]	N–SmA–SmB–SmG	[17]
3.O9O.3^2	N	9O.3	[2]	SmA–SmB	[17]
3.O10O.3^2	N	10O.3	[2]	SmA–SmB	[17]
4.O8O4^2	N	8O.4	[2]	SmA–SmB–SmG	[17]
4.O10O.4^2	N	10O.4	[2]	SmA–SmB–SmG	[17]
5.O7O.5^a	NSmA	7O.5		N–SmA–SmC–SmG	[17]
5.O8O.5^2	NSmA	8O.5	[2]	SmA–SmB–SmG	[17]
5.O9O.5^2	N	9O.5	[2]	SmA–SmB–SmG	[17]
5.O10O.5^2	N	10O.5	[2]	SmA–SmB–SmG	[17]
5.O11O.5^a	N	11O.5			[17]

^aPresent work.

Table 3. Phase variants, the percentage of density jumps, thermal expansion coefficient maxima at the phase interface and the dρ/dT values in different of dimeric liquid crystals.

Dimeric compound	Phase variant	Percentage of density jumps (Δρ/ρ) across IN phase transition	Percentage of density jumps (Δρ/ρ) across NSmA phase	Thermal expansion coefficient maxima, α (10^−4 °C^−1) at Iso–N	Thermal expansion coefficient maxima, α (10^−4 °C^−1) at N–SmA	(dρ/dT) × 10^−4 °C^−1
						Isotropic phase	Nematic phase	SmA phase
3.O7O.3^a	N	0.67	–	56.89	—	3.52	7.70	–
5.O11O.5^a	N	0.57	–	78.11	–	4.76	8.21	–
3.O8O.3^2	N	0.42		66.84		5.23	8.61	—
3.O9O.3^2	N	1.97		397.10		2.50	5.00	—
3.O10O.3^2	N	2.43		308.90		6.80	9.00	—
4.O8O4^2	N	0.51		71.94		5.40	7.50	—
4.O10O.4^2	N	2.75		284.0		5.50	9.30	—
5.O7O.5^a	NSmA	0.52	0.10	75.60	29.70	5.00	7.90	11.6o
5.O8O.5^2	NSmA	1.44		73.89		5.21	8.63	14.64
5.O9O.5^2	N	1.88		283.25		3.00	6.10	—
5.O10O.5^2	N	1.68		704.0		5.80	9.20	—
6.O12O.6^b	N	2.09		422.97		—	—	—
7.O12O.7^b	N	1.51		290.10		–	—	—
CB.O10O.10^c	NSmC	1.04		86.01		–	—	—

^aPresent work.

^bRef. [3].

^cRef. [18].

Figure 3. Variation of density, ρ (g/cm³) and thermal expansion coefficient, α (10⁻⁴ °C⁻¹) with temperature in 3.O7O.3.

Figure 4. Variation of density, ρ (g/cm³) and thermal expansion coefficient, α (10⁻⁴ °C⁻¹) with temperature in 5.O7O.5.

Figure 5. Variation of density, ρ (g/cm³) and thermal expansion coefficient, α (10⁻⁴ °C⁻¹) with temperature in 5 .O11O.5.

Figure 6. Variation of refractive indices with temperature for the compound 3.O7O.3.

Figure 7. Variation of refractive indices with temperature for the compound 5.O7O.5.

Figure 8. Variation of refractive indices with temperature for the compound 5.O11O.5.

Figure 9. (a) Variation of order parameter with reduced temperature (T/Tc) in 3.O7O.3 compound (Vuks). (b) Variation of order parameter with reduced temperature (T/Tc) in 3.O7O.3 compound (Neugebauer).

Figure 10. (a) Variation of order parameter with reduced temperature (T/Tc) in 5.O7O.5 compound (Vuks). (b) Variation of order parameter with reduced temperature (T/Tc) in 5.O7O.5 compound (Neugebauer).

Figure 11. (a) Variation of order parameter with reduced temperature (T/Tc) in 5.O11O.5 compound (Vuks). (b) Variation of order parameter with reduced temperature (T/Tc) in 5.O11O.5 compound (Neugebauer).

Pisipati VGKM. Polymesomorphism in N-(p-n-Alkoxybenzylidene)-p-n-Alkylanilines (nO.m) compounds. Z Naturforsch. 2003;58a:661.

 Google Scholar

Pardhasaradhi P, Datta Prasad PV, Madhavi Latha D, et al. Orientational order parameter studies in two symmetric dimeric liquid crystals – an optical study. Phase Transit. 2012;85:1031–1044. DOI:10.1080/01411594.2012.671323.

 Web of Science ®Google Scholar

Bhuyan D, Pardhasaradhi P, Gogoi B, et al. Phase transition studies of 6.O12O.6 and 7.O6O.7 using density measurements. Mol Cryst Liq Cryst. 2011;540:205–212. DOI:10.1080/15421406.2011.568882.

 Web of Science ®Google Scholar

Gogoi B, Alapati PR, Verma AL. Phase transition studies in mesogenic dimers. Cryst Res Technol. 2002;37:1331.

 Web of Science ®Google Scholar