Supramolecular ferroelectric nematic materials

Figures & data

Figure 1. (Colour Online) Programmatically generated cartoon depictions of ellipsoids forming a conventional apolar nematic phase (a) and polar nematic phase (b), with order parameters (<P2>) of 0.60 and 0.67, respectively. (c) Molecular structure and transition temperatures of RM734 and a homologous hydrogen-bonded complex synthesised as part of this work. An idealised polar ellipsoid representation of molecular structure is used elsewhere in this figure, with the red/white/blue colouring used to illustrate regions of electronegativity/electropositivity.

Figure 2. (Colour Online) (a) Synthetic scheme for the synthesis of complexes 1 (Rm733.4npy) and 2 (Rm733.3f4npy), including the MVAC process. Photographs captured during the MVAC process for 2: (b) initial state (complex dissolved in acetone); (c) turbid state (maximum antisolvent concentration reached, complex precipitated); (d) final state (complex redisolved with heating); (e) complex 2 isolated as a colourless microcrystalline solid following suction filtration and drying.

Table 1. Transition temperatures (T, °C) and associated enthalpies (ΔH, kJ mol⁻¹) for the complexes 1 (Rm733.4npy) and 2 (Rm733.3f4npy). Transition temperatures for the analogous parent covalent materials RM734 and RM734-3F are given, above. # Transition observed by POM only. * the complex begins to decompose at   250°C.

No.	R =		Melt	NF-N	N-Iso
1 RM733.4NPy	H	T	225	45^#	145
		ΔH	50.6	-^#	0.3
2 RM733.3F4NPy	F	T	239*	50^#	110.9
		ΔH	47.1	-^#	0.6

Figure 3. (Colour Online) Photomicrographs of complex 1: (a) the schlieren texture of nematic phase at 67°C; (b) at N_F-N transition at 45°C; (c) the schlieren texture of the N_F phase at 41°C. Photomicrographs a–c are of the same region of the sample, with the scale bar corresponding to 50 µm. Phase diagrams for binary mixtures of: (d) complex 1 and RM734; (e) complex 2 and RM734; note that melting points are omitted for clarity.

Table 2. Dipole moment (µ, Debye), dipole angle (β, °) and anisotropy of polarizability (Δα, ų) for complexes 1 and 2, along with the parent covalent materials RM734 and RM734-3F, as calculated at the B3LYP-GD3BJ/6-31 g(d,p) level. Shape Anisotropy Parameter (ShAP) defined here as $l/\sqrt{\left(wb\right)}$, where $l/w/b$ are the molecular length, width and breadth, respectively.

No.	µ	β	Δα	ShAP
1	5.7	22.1	39.4	5.39
2	6.6	24.5	39.4	5.13
RM734	11.4	15.5	47.5	4.07
RM734-3F	12.3	15.6	48.5	4.34

Figure 4. (Colour Online) Optimized geometries of RM734 (a) and complexes 1 (b) and 2 (c) at the B3LYP-GD3BJ/6-31g(d,p) level of DFT, with the electrostatic potential (ESP, isovalue = 0.04 au) on the 0.001 au electron density isosurface.