[1] [1] Meyer R B. Structural problems in liquid crystal physics, Les Houches summer school in theoretical physics ［M］. Balian R, Weil G, editor. 1973 Molecular Fluids. New York: Gordon and Breach, 1976: 273-373.

          Meyer R B. Structural problems in liquid crystal physics, Les Houches summer school in theoretical physics ［M］. Balian R, Weil G, editor. 1973 Molecular Fluids. New York: Gordon and Breach, 1976: 273-373.

[2] [2] DOZOV I. On the spontaneous symmetry breaking in the mesophases of achiral banana-shaped molecules ［J］. EPL (Europhysics Letters), 2001, 56(2): 247-253.

          DOZOV I. On the spontaneous symmetry breaking in the mesophases of achiral banana-shaped molecules ［J］. EPL (Europhysics Letters), 2001, 56(2): 247-253.

[3] [3] CESTARI M, DIEZ-BERART S, DUNMUR D A, et al. Phase behavior and properties of the liquid-crystal dimer 1′′,7′′-bis(4-cyanobiphenyl-4′-yl) heptane: A twist-bend nematic liquid crystal ［J］. Physical Review E, 2011, 84(3): 031704.

          CESTARI M, DIEZ-BERART S, DUNMUR D A, et al. Phase behavior and properties of the liquid-crystal dimer 1′′,7′′-bis(4-cyanobiphenyl-4′-yl) heptane: A twist-bend nematic liquid crystal ［J］. Physical Review E, 2011, 84(3): 031704.

[4] [4] MEYER C, LUCKHURST G R, DOZOV I. The temperature dependence of the heliconical tilt angle in the twist-bend nematic phase of the odd dimer CB7CB ［J］. Journal of Materials Chemistry C, 2015, 3(2): 318-328.

          MEYER C, LUCKHURST G R, DOZOV I. The temperature dependence of the heliconical tilt angle in the twist-bend nematic phase of the odd dimer CB7CB ［J］. Journal of Materials Chemistry C, 2015, 3(2): 318-328.

[5] [5] JOKISAARI J P, LUCKHURST G R, TIMIMI B A, et al. Twist-bend nematic phase of the liquid crystal dimer CB7CB: orientational order and conical angle determined by129Xe and2H NMR spectroscopy ［J］. Liquid Crystals, 2015, 42(5-6): 708-721.

          JOKISAARI J P, LUCKHURST G R, TIMIMI B A, et al. Twist-bend nematic phase of the liquid crystal dimer CB7CB: orientational order and conical angle determined by129Xe and2H NMR spectroscopy ［J］. Liquid Crystals, 2015, 42(5-6): 708-721.

[6] [6] LUCKHURST G R, TIMIMI B A, WELLS N J, et al. On orientational order in nematic and twist-bend nematic phases: a2H-NMR study of binary mixtures of the odd dimer, 1″,9″-bis(4-cyanobiphenyl-4′-yl) nonane, (CB9CB), and the monomer, 4-pentyl-4′-cyanobiphenyl, (5CB-d2) ［J］. Liquid Crystals, 2018, 45(13-15): 1913-1928.

          LUCKHURST G R, TIMIMI B A, WELLS N J, et al. On orientational order in nematic and twist-bend nematic phases: a2H-NMR study of binary mixtures of the odd dimer, 1″,9″-bis(4-cyanobiphenyl-4′-yl) nonane, (CB9CB), and the monomer, 4-pentyl-4′-cyanobiphenyl, (5CB-d2) ［J］. Liquid Crystals, 2018, 45(13-15): 1913-1928.

[7] [7] MANDLE R J, GOODBY J W. Order parameters, orientational distribution functions and heliconical tilt angles of oligomeric liquid crystals ［J］. Physical Chemistry Chemical Physics, 2019, 21(13): 6839-6843.

          MANDLE R J, GOODBY J W. Order parameters, orientational distribution functions and heliconical tilt angles of oligomeric liquid crystals ［J］. Physical Chemistry Chemical Physics, 2019, 21(13): 6839-6843.

[8] [8] MACH P, PINDAK R, LEVELUT A M, et al. Structural characterization of various chiral smectic-C phases by resonant X-ray scattering ［J］. Physical Review Letters, 1998, 81(5): 1015-1018.

          MACH P, PINDAK R, LEVELUT A M, et al. Structural characterization of various chiral smectic-C phases by resonant X-ray scattering ［J］. Physical Review Letters, 1998, 81(5): 1015-1018.

[9] [9] FERNANDES P, BAROIS P, WANG S T, et al. Polarization studies of resonant forbidden reflections in liquid crystals ［J］. Physical Review Letters, 2007, 99(22): 227801.

          FERNANDES P, BAROIS P, WANG S T, et al. Polarization studies of resonant forbidden reflections in liquid crystals ［J］. Physical Review Letters, 2007, 99(22): 227801.

[10] [10] FOLCIA C L, ORTEGA J, ETXEBARRIA J, et al. Spontaneous and field-induced mesomorphism of a silyl-terminated bent-core liquid crystal as determined from second-harmonic generation and resonant X-ray scattering ［J］. Soft Matter, 2014, 10(1): 196-205.

          FOLCIA C L, ORTEGA J, ETXEBARRIA J, et al. Spontaneous and field-induced mesomorphism of a silyl-terminated bent-core liquid crystal as determined from second-harmonic generation and resonant X-ray scattering ［J］. Soft Matter, 2014, 10(1): 196-205.

[11] [11] GLEESON H F, HIRST L S. Resonant X-ray scattering: a tool for structure elucidation in liquid crystals ［J］. ChemPhysChem, 2006, 7(2): 321-328.

          GLEESON H F, HIRST L S. Resonant X-ray scattering: a tool for structure elucidation in liquid crystals ［J］. ChemPhysChem, 2006, 7(2): 321-328.

[12] [12] WANG C, LEE D H, HEXEMER A, et al. Defining the nanostructured morphology of triblock copolymers using resonant soft X-ray scattering ［J］. Nano Letters, 2011, 11(9): 3906-3911.

          WANG C, LEE D H, HEXEMER A, et al. Defining the nanostructured morphology of triblock copolymers using resonant soft X-ray scattering ［J］. Nano Letters, 2011, 11(9): 3906-3911.

[13] [13] TUMBLESTON J R, COLLINS B A, YANG L Q, et al. The influence of molecular orientation on organic bulk heterojunction solar cells ［J］. Nature Photonics, 2014, 8(5): 385-391.

          TUMBLESTON J R, COLLINS B A, YANG L Q, et al. The influence of molecular orientation on organic bulk heterojunction solar cells ［J］. Nature Photonics, 2014, 8(5): 385-391.

[14] [14] ZHU C H, WANG C, YOUNG A, et al. Probing and controlling liquid crystal helical nanofilaments ［J］. Nano Letters, 2015, 15(5): 3420-3424.

          ZHU C H, WANG C, YOUNG A, et al. Probing and controlling liquid crystal helical nanofilaments ［J］. Nano Letters, 2015, 15(5): 3420-3424.

[15] [15] ZHU C H, TUCHBAND M R, YOUNG A, et al. Resonant carbon K-edge soft X-ray scattering from lattice-free heliconical molecular ordering: soft dilative elasticity of the twist-bend liquid crystal phase ［J］. Physical Review Letters, 2016, 116(14): 147803.

          ZHU C H, TUCHBAND M R, YOUNG A, et al. Resonant carbon K-edge soft X-ray scattering from lattice-free heliconical molecular ordering: soft dilative elasticity of the twist-bend liquid crystal phase ［J］. Physical Review Letters, 2016, 116(14): 147803.

[16] [16] SALAMON＇CZYK M, VAUPOTIC N, POCIECHA D, et al. Structure of nanoscale-pitch helical phases: blue phase and twist-bend nematic phase resolved by resonant soft X-ray scattering ［J］. Soft Matter, 2017, 13(38): 6694-6699.

          SALAMON＇CZYK M, VAUPOTIC N, POCIECHA D, et al. Structure of nanoscale-pitch helical phases: blue phase and twist-bend nematic phase resolved by resonant soft X-ray scattering ［J］. Soft Matter, 2017, 13(38): 6694-6699.

[17] [17] BABAKHANOVA G, PARSOUZI Z, PALADUGU S, et al. Elastic and viscous properties of the nematic dimer CB7CB ［J］. Physical Review E, 2017, 96(6): 062704.

          BABAKHANOVA G, PARSOUZI Z, PALADUGU S, et al. Elastic and viscous properties of the nematic dimer CB7CB ［J］. Physical Review E, 2017, 96(6): 062704.

[18] [18] STEVENSON W D, ZENG X B, WELCH C, et al. Macroscopic chirality of twist-bend nematic phase in bent dimers confirmed by circular dichroism ［J］. Journal of Materials Chemistry C, 2020, 8(3): 1041-1047.

          STEVENSON W D, ZENG X B, WELCH C, et al. Macroscopic chirality of twist-bend nematic phase in bent dimers confirmed by circular dichroism ［J］. Journal of Materials Chemistry C, 2020, 8(3): 1041-1047.

[19] [19] BEGUIN L, EMSLEY J W, LELLI M, et al. The chirality of a twist-bend nematic phase identified by NMR spectroscopy ［J］. The Journal of Physical Chemistry B, 2012, 116(27): 7940-7951.

          BEGUIN L, EMSLEY J W, LELLI M, et al. The chirality of a twist-bend nematic phase identified by NMR spectroscopy ［J］. The Journal of Physical Chemistry B, 2012, 116(27): 7940-7951.

[20] [20] EMSLEY J W, LELLI M, LESAGE A, et al. A comparison of the conformational distributions of the achiral symmetric liquid crystal dimer CB7CB in the achiral nematic and chiral twist-bend nematic phases ［J］. The Journal of Physical Chemistry B, 2013, 117(21): 6547-6557.

          EMSLEY J W, LELLI M, LESAGE A, et al. A comparison of the conformational distributions of the achiral symmetric liquid crystal dimer CB7CB in the achiral nematic and chiral twist-bend nematic phases ［J］. The Journal of Physical Chemistry B, 2013, 117(21): 6547-6557.

[21] [21] EMSLEY J W, LESOT P, LUCKHURST G R, et al. Chiral solutes can seed the formation of enantiomorphic domains in a twist-bend nematic liquid crystal ［J］. Physical Review E, 2013, 87(4): 040501.

          EMSLEY J W, LESOT P, LUCKHURST G R, et al. Chiral solutes can seed the formation of enantiomorphic domains in a twist-bend nematic liquid crystal ［J］. Physical Review E, 2013, 87(4): 040501.

[22] [22] MEYER C, LUCKHURST G R, DOZOV I. Flexoelectrically driven electroclinic effect in the twist-bend nematic phase of achiral molecules with bent shapes ［J］. Physical Review Letters, 2013, 111(6): 067801.

          MEYER C, LUCKHURST G R, DOZOV I. Flexoelectrically driven electroclinic effect in the twist-bend nematic phase of achiral molecules with bent shapes ［J］. Physical Review Letters, 2013, 111(6): 067801.

[23] [23] GORECKA E, SALAMONCZYK M, ZEP A, et al. Do the short helices exist in the nematic TB phase? ［J］. Liquid Crystals, 2015, 42(1): 1-7.

          GORECKA E, SALAMONCZYK M, ZEP A, et al. Do the short helices exist in the nematic TB phase? ［J］. Liquid Crystals, 2015, 42(1): 1-7.

[24] [24] SINGH G, FU J X, AGRA-KOOIJMAN D M, et al. X-ray and Raman scattering study of orientational order in nematic and heliconical nematic liquid crystals ［J］. Physical Review E, 2016, 94(6): 060701.

          SINGH G, FU J X, AGRA-KOOIJMAN D M, et al. X-ray and Raman scattering study of orientational order in nematic and heliconical nematic liquid crystals ［J］. Physical Review E, 2016, 94(6): 060701.

[25] [25] XIANG Y, JING H Z, ZHANG Z D, et al. Tunable optical grating based on the flexoelectric effect in a bent-core nematic liquid crystal ［J］. Physical Review Applied, 2017, 7(6): 064032.

          XIANG Y, JING H Z, ZHANG Z D, et al. Tunable optical grating based on the flexoelectric effect in a bent-core nematic liquid crystal ［J］. Physical Review Applied, 2017, 7(6): 064032.

[26] [26] VAUPOTIN, ALI M, MAJEWSKI P W, et al. Polarization gratings spontaneously formed from a helical twist-bend nematic phase ［J］. ChemPhysChem, 2018, 19(19): 2566-2571.

          VAUPOTIN, ALI M, MAJEWSKI P W, et al. Polarization gratings spontaneously formed from a helical twist-bend nematic phase ［J］. ChemPhysChem, 2018, 19(19): 2566-2571.

[27] [27] KRISHNAMURTHY K S, KANAKALA M B, YELAMAGGAD C V, et al. Instabilities in the electric Freedericksz state of the twist-bend nematic liquid crystal CB7CB ［J］. Soft Matter, 2018, 14(26): 5393-5406.

          KRISHNAMURTHY K S, KANAKALA M B, YELAMAGGAD C V, et al. Instabilities in the electric Freedericksz state of the twist-bend nematic liquid crystal CB7CB ［J］. Soft Matter, 2018, 14(26): 5393-5406.

[28] [28] KLEMAN M, KRISHNAMURTHY K S. Defects in the twist-bend nematic phase: stabilities and instabilities of focal conic domains and related topics ［J］. Physical Review E, 2018, 98(3): 032705.

          KLEMAN M, KRISHNAMURTHY K S. Defects in the twist-bend nematic phase: stabilities and instabilities of focal conic domains and related topics ［J］. Physical Review E, 2018, 98(3): 032705.

[29] [29] PARTHASARATHI S, RAO D S S, PALAKURTHY N B, et al. Binary system exhibiting the nematic to twist-bend nematic transition: behavior of permittivity and elastic constants ［J］. The Journal of Physical Chemistry B, 2016, 120(22): 5056-5062.

          PARTHASARATHI S, RAO D S S, PALAKURTHY N B, et al. Binary system exhibiting the nematic to twist-bend nematic transition: behavior of permittivity and elastic constants ［J］. The Journal of Physical Chemistry B, 2016, 120(22): 5056-5062.

[30] [30] ROBLES-HERNNDEZ B, SEBASTIN N, DE LA FUENTE M R, et al. Twist, tilt, and orientational order at the nematic to twist-bend nematic phase transition of 1'',9''-bis(4-cyanobiphenyl-4'-yl) nonane: A dielectric,2H NMR, and calorimetric study ［J］. Physical Review E, 2015, 92(6): 062505.

          ROBLES-HERNNDEZ B, SEBASTIN N, DE LA FUENTE M R, et al. Twist, tilt, and orientational order at the nematic to twist-bend nematic phase transition of 1'',9''-bis(4-cyanobiphenyl-4'-yl) nonane: A dielectric,2H NMR, and calorimetric study ［J］. Physical Review E, 2015, 92(6): 062505.

[31] [31] CUKROV G, GOLESTANI Y M, XIANG J, et al. Comparative analysis of anisotropic material properties of uniaxial nematics formed by flexible dimers and rod-like monomers ［J］. Liquid Crystals, 2017, 44(1): 219-231.

          CUKROV G, GOLESTANI Y M, XIANG J, et al. Comparative analysis of anisotropic material properties of uniaxial nematics formed by flexible dimers and rod-like monomers ［J］. Liquid Crystals, 2017, 44(1): 219-231.

[32] [32] TRBOJEVIC N, READ D J, NAGARAJ M. Dielectric properties of liquid crystalline dimer mixtures exhibiting the nematic and twist-bend nematic phases ［J］. Physical Review E, 2017, 96(5): 052703.

          TRBOJEVIC N, READ D J, NAGARAJ M. Dielectric properties of liquid crystalline dimer mixtures exhibiting the nematic and twist-bend nematic phases ［J］. Physical Review E, 2017, 96(5): 052703.

[33] [33] VARANYTSIA A, CHIEN L C. Giant flexoelectro-optic effect with liquid crystal dimer CB7CB ［J］. Scientific Reports, 2017, 7: 41333.

          VARANYTSIA A, CHIEN L C. Giant flexoelectro-optic effect with liquid crystal dimer CB7CB ［J］. Scientific Reports, 2017, 7: 41333.

[34] [34] WANG Y, ZHENG Z G, BISOYI H K, et al. Thermally reversible full color selective reflection in a self-organized helical superstructure enabled by a bent-core oligomesogen exhibiting a twist-bend nematic phase ［J］. Materials Horizons, 2016, 3(5): 442-446.

          WANG Y, ZHENG Z G, BISOYI H K, et al. Thermally reversible full color selective reflection in a self-organized helical superstructure enabled by a bent-core oligomesogen exhibiting a twist-bend nematic phase ［J］. Materials Horizons, 2016, 3(5): 442-446.

[35] [35] LPEZ D O, SEBASTIAN N, DE LA FUENTE M R, et al. Disentangling molecular motions involved in the glass transition of a twist-bend nematic liquid crystal through dielectric studies ［J］. The Journal of Chemical Physics, 2012, 137(3): 034502.

          LPEZ D O, SEBASTIAN N, DE LA FUENTE M R, et al. Disentangling molecular motions involved in the glass transition of a twist-bend nematic liquid crystal through dielectric studies ［J］. The Journal of Chemical Physics, 2012, 137(3): 034502.

[36] [36] ROBLES-HERNNDEZ B, SEBASTIN N, SALUD J, et al. Molecular dynamics of a binary mixture of twist-bend nematic liquid crystal dimers studied by dielectric spectroscopy ［J］. Physical Review E, 2016, 93(6): 062705.

          ROBLES-HERNNDEZ B, SEBASTIN N, SALUD J, et al. Molecular dynamics of a binary mixture of twist-bend nematic liquid crystal dimers studied by dielectric spectroscopy ［J］. Physical Review E, 2016, 93(6): 062705.

[37] [37] MERKEL K, WELCH C, AHMED Z, et al. Dielectric response of electric-field distortions of the twist-bend nematic phase for LC dimers ［J］. The Journal of Chemical Physics, 2019, 151(11): 114908.

          MERKEL K, WELCH C, AHMED Z, et al. Dielectric response of electric-field distortions of the twist-bend nematic phase for LC dimers ［J］. The Journal of Chemical Physics, 2019, 151(11): 114908.

[38] [38] VANAKARAS A G, PHOTINOS D J. Molecular dynamics simulations of nematic phases formed by cyano-biphenyl dimers ［J］. Liquid Crystals, 2018, 45(13/15): 2184-2196.

          VANAKARAS A G, PHOTINOS D J. Molecular dynamics simulations of nematic phases formed by cyano-biphenyl dimers ［J］. Liquid Crystals, 2018, 45(13/15): 2184-2196.

[39] [39] TRIPATHI C S P, LOSADA-PREZ P, GLORIEUX C, et al. Nematic-nematic phase transition in the liquid crystal dimer CBC9CB and its mixtures with 5CB: a high-resolution adiabatic scanning calorimetric study ［J］. Physical Review E, 2011, 84(4): 041707.

          TRIPATHI C S P, LOSADA-PREZ P, GLORIEUX C, et al. Nematic-nematic phase transition in the liquid crystal dimer CBC9CB and its mixtures with 5CB: a high-resolution adiabatic scanning calorimetric study ［J］. Physical Review E, 2011, 84(4): 041707.

[40] [40] MIGLIOLI I, BACCHIOCCHI C, ARCIONI A, et al. Director configuration in the twist-bend nematic phase of CB11CB ［J］. Journal of Materials Chemistry C, 2016, 4(41): 9887-9896.

          MIGLIOLI I, BACCHIOCCHI C, ARCIONI A, et al. Director configuration in the twist-bend nematic phase of CB11CB ［J］. Journal of Materials Chemistry C, 2016, 4(41): 9887-9896.

[41] [41] BACCHIOCCHI C, TAMBA M G, MEHL G H, et al. EPR study of the polydomain structure of the twist-bend nematic phase of CB9CB in the bulk ［J］. Liquid Crystals, 2018, 45(13/15): 2109-2120.

          BACCHIOCCHI C, TAMBA M G, MEHL G H, et al. EPR study of the polydomain structure of the twist-bend nematic phase of CB9CB in the bulk ［J］. Liquid Crystals, 2018, 45(13/15): 2109-2120.

[42] [42] SATAPATHY P, PARTHASARATHI S, RAO D S S, et al. Influence of zinc oxide nanorods on an orientationally ordered fluid comprising soft-bent dimers ［J］. Bulletin of Materials Science, 2018, 41(5): 116.

          SATAPATHY P, PARTHASARATHI S, RAO D S S, et al. Influence of zinc oxide nanorods on an orientationally ordered fluid comprising soft-bent dimers ［J］. Bulletin of Materials Science, 2018, 41(5): 116.

[43] [43] YOU R, PARK W, CARLSON E, et al. Nanoconfined heliconical structure of twist-bend nematic liquid crystal phase ［J］. Liquid Crystals, 2019, 46(2): 316-325.

          YOU R, PARK W, CARLSON E, et al. Nanoconfined heliconical structure of twist-bend nematic liquid crystal phase ［J］. Liquid Crystals, 2019, 46(2): 316-325.

[44] [44] CHEN D, NAKATA M, SHAO R F, et al. Twist-bend heliconical chiral nematic liquid crystal phase of an achiral rigid bent-core mesogen ［J］. Physical Review E, 2014, 89(2): 022506.

          CHEN D, NAKATA M, SHAO R F, et al. Twist-bend heliconical chiral nematic liquid crystal phase of an achiral rigid bent-core mesogen ［J］. Physical Review E, 2014, 89(2): 022506.

[45] [45] MANDLE R J, GOODBY J W. A liquid crystalline oligomer exhibiting nematic and twist-bend nematic mesophases ［J］. ChemPhysChem, 2016, 17(7): 967-970.

          MANDLE R J, GOODBY J W. A liquid crystalline oligomer exhibiting nematic and twist-bend nematic mesophases ［J］. ChemPhysChem, 2016, 17(7): 967-970.

[46] [46] DAWOOD A A, GROSSEL M C, LUCKHURST G R, et al. On the twist-bend nematic phase formed directly from the isotropic phase ［J］. Liquid Crystals, 2016, 43(1): 2-12.

          DAWOOD A A, GROSSEL M C, LUCKHURST G R, et al. On the twist-bend nematic phase formed directly from the isotropic phase ［J］. Liquid Crystals, 2016, 43(1): 2-12.

[47] [47] DAWOOD A A, GROSSEL M C, LUCKHURST G R, et al. Twist-bend nematics, liquid crystal dimers, structure-property relations ［J］. Liquid Crystals, 2017, 44(1): 106-126.

          DAWOOD A A, GROSSEL M C, LUCKHURST G R, et al. Twist-bend nematics, liquid crystal dimers, structure-property relations ［J］. Liquid Crystals, 2017, 44(1): 106-126.

[48] [48] JANSZE S M, MARTNEZ-FELIPE A, STOREY J M D, et al. A twist-bend nematic phase driven by hydrogen bonding ［J］. Angewandte Chemie International Edition, 2015, 54(2): 643-646.

          JANSZE S M, MARTNEZ-FELIPE A, STOREY J M D, et al. A twist-bend nematic phase driven by hydrogen bonding ［J］. Angewandte Chemie International Edition, 2015, 54(2): 643-646.

[49] [49] WALKER R, POCIECHA D, ABBERLEY J P, et al. Spontaneous chirality through mixing achiral components: a twist-bend nematic phase driven by hydrogen-bonding between unlike components ［J］. Chemical Communications, 2018, 54(27): 3383-3386.

          WALKER R, POCIECHA D, ABBERLEY J P, et al. Spontaneous chirality through mixing achiral components: a twist-bend nematic phase driven by hydrogen-bonding between unlike components ［J］. Chemical Communications, 2018, 54(27): 3383-3386.

[50] [50] WALKER R, POCIECHA D, MARTINEZ-FELIPE A, et al. Twist-bend nematogenic supramolecular dimers and trimers formed by hydrogen bonding ［J］. Crystals, 2020, 10(3): 175.

          WALKER R, POCIECHA D, MARTINEZ-FELIPE A, et al. Twist-bend nematogenic supramolecular dimers and trimers formed by hydrogen bonding ［J］. Crystals, 2020, 10(3): 175.

[51] [51] PATERSON D A, WALKER R, ABBERLEY J P, et al. Azobenzene-based liquid crystal dimers and the twist-bend nematic phase ［J］. Liquid Crystals, 2017, 44(12/13): 2060-2078.

          PATERSON D A, WALKER R, ABBERLEY J P, et al. Azobenzene-based liquid crystal dimers and the twist-bend nematic phase ［J］. Liquid Crystals, 2017, 44(12/13): 2060-2078.

[52] [52] ANGIOLINI L. Smart light-responsive materials: azobenzene-containing polymers and liquid crystals ［J］. Macromolecular Chemistry and Physics, 2010, 211(4): 481.

          ANGIOLINI L. Smart light-responsive materials: azobenzene-containing polymers and liquid crystals ［J］. Macromolecular Chemistry and Physics, 2010, 211(4): 481.

[53] [53] YELAMAGGAD C V, PRASAD S K, LI Q. Photo-stimulated phase transformations in liquid crystals and their non-display applications ［M］//LI Q. Liquid Crystals Beyond Displays: Chemistry, Physics, and Applications. Hoboken: Wiley, 2012.

          YELAMAGGAD C V, PRASAD S K, LI Q. Photo-stimulated phase transformations in liquid crystals and their non-display applications ［M］//LI Q. Liquid Crystals Beyond Displays: Chemistry, Physics, and Applications. Hoboken: Wiley, 2012.

[54] [54] PRASAD S K, MADHURI P L, SATAPATHY P, et al. A soft-bent dimer composite exhibiting twist-bend nematic phase: photo-driven effects and an optical memory device ［J］. Applied Physics Letters, 2018, 112(25): 253701.

          PRASAD S K, MADHURI P L, SATAPATHY P, et al. A soft-bent dimer composite exhibiting twist-bend nematic phase: photo-driven effects and an optical memory device ［J］. Applied Physics Letters, 2018, 112(25): 253701.

[55] [55] PATERSON D A, XIANG J, SINGH G, et al. Reversible isothermal twist-bend nematic-nematic phase transition driven by the photoisomerization of an azobenzene-based nonsymmetric liquid crystal dimer ［J］. Journal of the American Chemical Society, 2016, 138(16): 5283-5289.

          PATERSON D A, XIANG J, SINGH G, et al. Reversible isothermal twist-bend nematic-nematic phase transition driven by the photoisomerization of an azobenzene-based nonsymmetric liquid crystal dimer ［J］. Journal of the American Chemical Society, 2016, 138(16): 5283-5289.

[56] [56] LU Z B, HENDERSON P A, PATERSON B J A, et al. Liquid crystal dimers and the twist-bend nematic phase. The preparation and characterisation of the α,ω-bis(4-cyanobiphenyl-4′-yl) alkanedioates ［J］. Liquid Crystals, 2014, 41(3): 471-483.

          LU Z B, HENDERSON P A, PATERSON B J A, et al. Liquid crystal dimers and the twist-bend nematic phase. The preparation and characterisation of the α,ω-bis(4-cyanobiphenyl-4′-yl) alkanedioates ［J］. Liquid Crystals, 2014, 41(3): 471-483.

[57] [57] ARCHBOLD C T, ANDREWS J L, MANDLE R J, et al. Effect of the linking unit on the twist-bend nematic phase in liquid crystal dimers: a comparative study of two homologous series of methylene-and ether-linked dimers ［J］. Liquid Crystals, 2017, 44(1): 84-92.

          ARCHBOLD C T, ANDREWS J L, MANDLE R J, et al. Effect of the linking unit on the twist-bend nematic phase in liquid crystal dimers: a comparative study of two homologous series of methylene-and ether-linked dimers ［J］. Liquid Crystals, 2017, 44(1): 84-92.

[58] [58] PATERSON D A, ABBERLEY J P, HARRISON W T, et al. Cyanobiphenyl-based liquid crystal dimers and the twist-bend nematic phase ［J］. Liquid Crystals, 2017, 44(1): 127-146.

          PATERSON D A, ABBERLEY J P, HARRISON W T, et al. Cyanobiphenyl-based liquid crystal dimers and the twist-bend nematic phase ［J］. Liquid Crystals, 2017, 44(1): 127-146.

[59] [59] SEBASTIN N, LPEZ D O, ROBLES-HERNNDEZ B, et al. Dielectric, calorimetric and mesophase properties of 1''-(2',4-difluorobiphenyl-4'-yloxy)-9''-(4-cyanobiphenyl-4'-yloxy) nonane: an odd liquid crystal dimer with a monotropic mesophase having the characteristics of a twist-bend nematic phase ［J］. Physical Chemistry Chemical Physics, 2014, 16(39): 21391-21406.

          SEBASTIN N, LPEZ D O, ROBLES-HERNNDEZ B, et al. Dielectric, calorimetric and mesophase properties of 1''-(2',4-difluorobiphenyl-4'-yloxy)-9''-(4-cyanobiphenyl-4'-yloxy) nonane: an odd liquid crystal dimer with a monotropic mesophase having the characteristics of a twist-bend nematic phase ［J］. Physical Chemistry Chemical Physics, 2014, 16(39): 21391-21406.

[60] [60] ARAKAWA Y, KOMATSU K, TSUJI H. Twist-bend nematic liquid crystals based on thioether linkage ［J］. New Journal of Chemistry, 2019, 43(17): 6786-6793.

          ARAKAWA Y, KOMATSU K, TSUJI H. Twist-bend nematic liquid crystals based on thioether linkage ［J］. New Journal of Chemistry, 2019, 43(17): 6786-6793.

[61] [61] STEVENSON W D, ZOU H X, ZENG X B, et al. Dynamic calorimetry and XRD studies of the nematic and twist-bend nematic phase transitions in a series of dimers with increasing spacer length ［J］. Physical Chemistry Chemical Physics, 2018, 20(39): 25268-25274.

          STEVENSON W D, ZOU H X, ZENG X B, et al. Dynamic calorimetry and XRD studies of the nematic and twist-bend nematic phase transitions in a series of dimers with increasing spacer length ［J］. Physical Chemistry Chemical Physics, 2018, 20(39): 25268-25274.

[62] [62] LONGA L, TOMCZYK W. Twist-bend nematic phase in the presence of molecular chirality ［J］. Liquid Crystals, 2018, 45(13/15): 2074-2085.

          LONGA L, TOMCZYK W. Twist-bend nematic phase in the presence of molecular chirality ［J］. Liquid Crystals, 2018, 45(13/15): 2074-2085.

[63] [63] ABBERLEY J P, JANSZE S M, WALKER R, et al. Structure-property relationships in twist-bend nematogens: the influence of terminal groups ［J］. Liquid Crystals, 2017, 44(1): 68-83.

          ABBERLEY J P, JANSZE S M, WALKER R, et al. Structure-property relationships in twist-bend nematogens: the influence of terminal groups ［J］. Liquid Crystals, 2017, 44(1): 68-83.

[64] [64] MANDLE R J, GOODBY J W. Optically active bimesogens incorporating branched central spacers ［J］. RSC Advances, 2018, 8(33): 18542-18548.

          MANDLE R J, GOODBY J W. Optically active bimesogens incorporating branched central spacers ［J］. RSC Advances, 2018, 8(33): 18542-18548.

[65] [65] ADLEM K,OPIM, LUCKHURST G R, et al. Chemically induced twist-bend nematic liquid crystals, liquid crystal dimers, and negative elastic constants ［J］. Physical Review E, 2013, 88(2): 022503.

          ADLEM K,OPIM, LUCKHURST G R, et al. Chemically induced twist-bend nematic liquid crystals, liquid crystal dimers, and negative elastic constants ［J］. Physical Review E, 2013, 88(2): 022503.

[66] [66] RIBEIRO DE ALMEIDA R R, ZHANG C, PARRI O, et al. Nanostructure and dielectric properties of a twist-bend nematic liquid crystal mixture ［J］. Liquid Crystals, 2014, 41(11): 1661-1667.

          RIBEIRO DE ALMEIDA R R, ZHANG C, PARRI O, et al. Nanostructure and dielectric properties of a twist-bend nematic liquid crystal mixture ［J］. Liquid Crystals, 2014, 41(11): 1661-1667.

[67] [67] MANDLE R J, GOODBY J W. Does topology dictate the incidence of the twist-bend phase? Insights gained from novel unsymmetrical bimesogens ［J］. Chemistry-A European Journal, 2016, 22(51): 18456-18464.

          MANDLE R J, GOODBY J W. Does topology dictate the incidence of the twist-bend phase? Insights gained from novel unsymmetrical bimesogens ［J］. Chemistry-A European Journal, 2016, 22(51): 18456-18464.

[68] [68] MANDLE R J, GOODBY J W. Progression from Nano to macro science in soft matter systems: dimers to trimers and oligomers in twist-bend liquid crystals ［J］. RSC Advances, 2016, 6(41): 34885-34893.

          MANDLE R J, GOODBY J W. Progression from Nano to macro science in soft matter systems: dimers to trimers and oligomers in twist-bend liquid crystals ［J］. RSC Advances, 2016, 6(41): 34885-34893.

[69] [69] CHALLA P K, BORSHCH V, PARRI O, et al. Twist-bend nematic liquid crystals in high magnetic fields ［J］. Physical Review E, 2014, 89(6): 060501.

          CHALLA P K, BORSHCH V, PARRI O, et al. Twist-bend nematic liquid crystals in high magnetic fields ［J］. Physical Review E, 2014, 89(6): 060501.

[70] [70] MEYER C. Nematic twist-bend phase under external constraints ［J］. Liquid Crystals, 2016, 43(13/15): 2144-2162.

          MEYER C. Nematic twist-bend phase under external constraints ［J］. Liquid Crystals, 2016, 43(13/15): 2144-2162.

[71] [71] PARTHASARATHI S, RAO D S S, PALAKURTHY N B, et al. Effect of pressure on dielectric and frank elastic constants of a material exhibiting the twist bend nematic phase ［J］. The Journal of Physical Chemistry B, 2017, 121(4): 896-903.

          PARTHASARATHI S, RAO D S S, PALAKURTHY N B, et al. Effect of pressure on dielectric and frank elastic constants of a material exhibiting the twist bend nematic phase ［J］. The Journal of Physical Chemistry B, 2017, 121(4): 896-903.

[72] [72] SHAMID S M, DHAKAL S, SELINGER J V. Statistical mechanics of bend flexoelectricity and the twist-bend phase in bent-core liquid crystals ［J］. Physical Review E, 2013, 87(5): 052503.

          SHAMID S M, DHAKAL S, SELINGER J V. Statistical mechanics of bend flexoelectricity and the twist-bend phase in bent-core liquid crystals ［J］. Physical Review E, 2013, 87(5): 052503.

[73] [73] VIRGA E G. Double-well elastic theory for twist-bend nematic phases ［J］. Physical Review E, 2014, 89(5): 052502.

          VIRGA E G. Double-well elastic theory for twist-bend nematic phases ［J］. Physical Review E, 2014, 89(5): 052502.

[74] [74] KATS E I, LEBEDEV V V. Landau theory for helical nematic phases ［J］. JETP Letters, 2014, 100(2): 110-113.

          KATS E I, LEBEDEV V V. Landau theory for helical nematic phases ［J］. JETP Letters, 2014, 100(2): 110-113.

[75] [75] GRECO C, LUCKHURST G R, FERRARINI A. Molecular geometry, twist-bend nematic phase and unconventional elasticity: a generalised Maier-Saupe theory ［J］. Soft Matter, 2014, 10(46): 9318-9323.

          GRECO C, LUCKHURST G R, FERRARINI A. Molecular geometry, twist-bend nematic phase and unconventional elasticity: a generalised Maier-Saupe theory ［J］. Soft Matter, 2014, 10(46): 9318-9323.

[76] [76] BARBERO G, EVANGELISTA L R, ROSSETO M P, et al. Elastic continuum theory: towards understanding of the twist-bend nematic phases ［J］. Physical Review E, 2015, 92(3): 030501.

          BARBERO G, EVANGELISTA L R, ROSSETO M P, et al. Elastic continuum theory: towards understanding of the twist-bend nematic phases ［J］. Physical Review E, 2015, 92(3): 030501.

[77] [77] ZOLA R S, BARBERO G, LELIDIS I, et al. A continuum description for cholesteric and nematic twist-bend phases based on symmetry considerations ［J］. Liquid Crystals, 2017, 44(1): 24-30.

          ZOLA R S, BARBERO G, LELIDIS I, et al. A continuum description for cholesteric and nematic twist-bend phases based on symmetry considerations ［J］. Liquid Crystals, 2017, 44(1): 24-30.

[78] [78] ZOLA R S, RIBEIRO DE ALMEIDA R R, BARBERO G, et al. Behaviour of twist-bend nematic structure under a uniform magnetic field ［J］. Molecular Crystals and Liquid Crystals, 2017, 649(1): 71-78.

          ZOLA R S, RIBEIRO DE ALMEIDA R R, BARBERO G, et al. Behaviour of twist-bend nematic structure under a uniform magnetic field ［J］. Molecular Crystals and Liquid Crystals, 2017, 649(1): 71-78.

[79] [79] SHIYANOVSKII S V, SIMONRIO P S, VIRGA E G. Coarse-graining elastic theory for twist-bend nematic phases ［J］. Liquid Crystals, 2017, 44(1): 31-44.

          SHIYANOVSKII S V, SIMONRIO P S, VIRGA E G. Coarse-graining elastic theory for twist-bend nematic phases ［J］. Liquid Crystals, 2017, 44(1): 31-44.

[80] [80] ROSSETO M P, RIBEIRO DE ALMEIDA R R, ZOLA R S, et al. Nanometric pitch in modulated structures of twist-bend nematic liquid crystals ［J］. Journal of Molecular Liquids, 2018, 267: 266-270.

          ROSSETO M P, RIBEIRO DE ALMEIDA R R, ZOLA R S, et al. Nanometric pitch in modulated structures of twist-bend nematic liquid crystals ［J］. Journal of Molecular Liquids, 2018, 267: 266-270.

[81] [81] FERRARINI A. The twist-bend nematic phase: Molecular insights from a generalised Maier-Saupe theory ［J］. Liquid Crystals, 2017, 44(1): 45-57.

          FERRARINI A. The twist-bend nematic phase: Molecular insights from a generalised Maier-Saupe theory ［J］. Liquid Crystals, 2017, 44(1): 45-57.

[82] [82] MATSUYAMA A. Twist-bend nematic phases in binary mixtures of banana-shaped liquid crystalline molecules ［J］. Liquid Crystals, 2018, 45(4): 607-624.

          MATSUYAMA A. Twist-bend nematic phases in binary mixtures of banana-shaped liquid crystalline molecules ［J］. Liquid Crystals, 2018, 45(4): 607-624.

[83] [83] XIANG J, LI Y N, LI Q, et al. Electrically tunable selective reflection of light from ultraviolet to visible and infrared by heliconical cholesterics ［J］. Advanced Materials, 2015, 27(19): 3014-3018.

          XIANG J, LI Y N, LI Q, et al. Electrically tunable selective reflection of light from ultraviolet to visible and infrared by heliconical cholesterics ［J］. Advanced Materials, 2015, 27(19): 3014-3018.

[84] [84] XIANG J, VARANYTSIA A, MINKOWSKI F, et al. Electrically tunable laser based on oblique heliconical cholesteric liquid crystal ［J］. Proceedings of the National Academy of Sciences of the United States of America, 2016, 113(46): 12925-12928.

          XIANG J, VARANYTSIA A, MINKOWSKI F, et al. Electrically tunable laser based on oblique heliconical cholesteric liquid crystal ［J］. Proceedings of the National Academy of Sciences of the United States of America, 2016, 113(46): 12925-12928.

[85] [85] YUAN C L, HUANG W B, ZHENG Z G, et al. Stimulated transformation of soft helix among helicoidal, heliconical, and their inverse helices ［J］. Science Advances, 2019, 5(10): eaax9501.

          YUAN C L, HUANG W B, ZHENG Z G, et al. Stimulated transformation of soft helix among helicoidal, heliconical, and their inverse helices ［J］. Science Advances, 2019, 5(10): eaax9501.

[86] [86] VELZQUEZ C A, REYES J A. Cherenkov radiation in a twist bend nematic ［J］. Molecular Crystals and Liquid Crystals, 2017, 657(1): 167-172.

          VELZQUEZ C A, REYES J A. Cherenkov radiation in a twist bend nematic ［J］. Molecular Crystals and Liquid Crystals, 2017, 657(1): 167-172.

[87] [87] YOU R, PATERSON D A, STOREY J M D, et al. Formation of periodic zigzag patterns in the twist-bend nematic liquid crystal phase by surface treatment ［J］. Liquid Crystals, 2017, 44(1): 168-176.

          YOU R, PATERSON D A, STOREY J M D, et al. Formation of periodic zigzag patterns in the twist-bend nematic liquid crystal phase by surface treatment ［J］. Liquid Crystals, 2017, 44(1): 168-176.