Thermotropic ionic liquid crystal molecule, characterized in that it comprises: • a "rigid" part, constituted of a polycyclic group Ar formed from two to six rings, at least one of which is aromatic, said rings being, independently of each other, 4-to 6-membered, said polycyclic group possibly including up to 18 heteroatoms, chosen in particular from the group constituted of S, N and O; said polycyclic group Ar having one of the following backbones: • a "flexible" part, formed from two linear or branched, saturated or unsaturated, fluorinated or nonfluorinated aliphatic chains, said chain(s) being optionally interrupted with one or more heteroatoms, with one or more metalloids and/or with one or more aromatic or nonaromatic, 4- to 6-membered (hetero)cycles, and optionally substituted with one or more groups chosen from the group constituted by hydroxyl, -NH 2 and oxo groups; said aliphatic chains being covalently bonded via a single trivalent spacer to the same carbon atom of the group Ar forming the rigid part; said spacer being an atom or a group of atoms with a valency equal to 3; and • one or more ionic groups -A x- C x+, -A x- being an anionic group covalently bonded to said rigid part, with x being an integer equal to 1 or 2, -A x- being chosen from the group constituted of sulfonate anions, sulfonylimide of formula -SO 2 -N - -SO 2 C y F 2y+1 with y being an integer ranging from 0 to 4, borate, borane, phosphate, phosphinate, phosphonate, silicate, carbonate, sulfide, selenate, nitrate and perchlorate; and C x+ being a counter-cation of the anionic group - A x, chosen from the group constituted of H + and alkali metal and alkaline-earth metal cations. • a "rigid" part, constituted of a polycyclic group Ar formed from two to six rings, at least one of which is aromatic, said rings being, independently of each other, 4-to 6-membered, said polycyclic group possibly including up to 18 heteroatoms, chosen in particular from the group constituted of S, N and O; said polycyclic group Ar having one of the following backbones: • a "flexible" part, formed from two linear or branched, saturated or unsaturated, fluorinated or nonfluorinated aliphatic chains, said chain(s) being optionally interrupted with one or more heteroatoms, with one or more metalloids and/or with one or more aromatic or nonaromatic, 4- to 6-membered (hetero)cycles, and optionally substituted with one or more groups chosen from the group constituted by hydroxyl, -NH 2 and oxo groups; said aliphatic chains being covalently bonded via a single trivalent spacer to the same carbon atom of the group Ar forming the rigid part; said spacer being an atom or a group of atoms with a valency equal to 3; and • one or more ionic groups -A x- C x+, -A x- being an anionic group covalently bonded to said rigid part, with x being an integer equal to 1 or 2, -A x- being chosen from the group constituted of sulfonate anions, sulfonylimide of formula -SO 2 -N - -SO 2 C y F 2y+1 with y being an integer ranging from 0 to 4, borate, borane, phosphate, phosphinate, phosphonate, silicate, carbonate, sulfide, selenate, nitrate and perchlorate; and C x+ being a counter-cation of the anionic group - A x, chosen from the group constituted of H + and alkali metal and alkaline-earth metal cations. -A x- being an anionic group covalently bonded to said rigid part, with x being an integer equal to 1 or 2, -A x- being chosen from the group constituted of sulfonate anions, sulfonylimide of formula -SO 2 -N - -SO 2 C y F 2y+1 with y being an integer ranging from 0 to 4, borate, borane, phosphate, phosphinate, phosphonate, silicate, carbonate, sulfide, selenate, nitrate and perchlorate; and C x+ being a counter-cation of the anionic group - A x, chosen from the group constituted of H + and alkali metal and alkaline-earth metal cations.