Ferroelectric nematic liquid crystal gel

Abstract

Aspects of the present invention relate to liquid crystal gels (liquid crystal gels) that exhibit a ferroelectric nematic liquid crystal phase over a wide range of temperatures, preferably at ambient temperatures. The gel is a physical gel based on a liquid crystal material. In addition, the invention also relates to electric and electronic components containing the ferroelectric liquid crystal gel.

Description

Technical Field

[0001] This invention relates to liquid crystal gels that exhibit a ferroelectric nematic liquid crystal phase over a wide temperature range, preferably at ambient temperature. Furthermore, this invention also relates to electrical and electronic components containing the ferroelectric liquid crystal gel according to the invention. Background Technology

[0002] Energy harvesting is becoming increasingly important in various contexts, such as wearable devices. For a review of the technology, see Xu, C., Song, Y., Han, M., et al. , Portable and wearable self-powered systems based on emerging energy harvesting technology, Microsyst Nanoeng 7, 25 (2021), (https: / / doi.org / 10.1038 / s41378-021-00248-z). Furthermore, for a review of current techniques using piezoelectric polymer composites compared to conventional solid-state piezoelectric-ceramics, see Mishra, S., Unnikrishnan, L., Nayak, SK, Mohanty, S., Macromol. Mater. Eng. 2019, 1800463, (https: / / doi.org / 10.1002 / mame.201800463). Utilizing the properties of some ferroelectric materials, such as piezoelectricity, is a recognized method for energy harvesting, and these properties can also be used for mechanical sensors and sound generation. Piezoelectricity is exhibited by some non-centrosymmetric crystal structures and polarized polymers. However, suitable materials are limited.

[0003] Numerous systems of gels (materials composed of 3D networks of chains that trap liquid phase to form semi-solid, generally elastic structures) have been studied, including combinations of liquid crystals and organic gelling agents. A tutorial article on nematic gels can be found in *Liquid-crystalline physical gels*, T. Kato, Y. Hirai, S. Nakaso, M. Moriyama, *Chem. Soc. Rev.* 2007, 36, 1857 (https: / / pubs.rsc.org / en / content / articlelanding / 2007 / cs / b612546h).

[0004] As supported by Kato et al., liquid crystal physical gels are obtained through the self-assembly of gel factors into fibrous solid networks within liquid crystals. The liquid crystal is transformed into a gel with a chemical or physical 3D network structure. LC chemical gels are prepared by polymerization of LC or non-LC monomers within the liquid crystal. Liquid crystal physical gels are obtained through the self-assembly of gel factors into fibrous solid networks within the liquid crystal. Typically, these networks employ H-donor-acceptor bonds or other reversible molecular interactions between gel factor molecules.

[0005] In recent years, the application areas of liquid crystal compounds have expanded considerably to various types of display devices, electro-optical devices, electronic components, sensors, and more. For this reason, many different structures have been proposed, particularly in the field of nematic liquid crystals. To date, nematic liquid crystal compounds have found the most widespread use in flat panel display devices. They have been used specifically in passive TN or STN matrix displays or systems with TFT active matrices (including well-known TN, IPS, FFS, and VA systems).

[0006] Most of these devices employ the nematic liquid crystal phase, including all common LCD televisions, LCD desktop monitors, and mobile LCD devices. Some alternative liquid crystal phases, such as ferroelectric smectic or blue phases, are known. However, for decades, the ferroelectric nematic phase (N... F The LC phase has been theoretically assumed, and suitable liquid crystal materials with this property have not yet been found. Only recently have some chemical structures been reported to exhibit ferroelectric nematic behavior at certain temperatures.

[0007] First, Hiroya Nishikawa, Kazuya Shiroshita, Hiroki Higuchi, Yasushi Okumura, Yasuhiro Haseba, Shin-ichi Yamamoto, Koki Sago, and Hirotsugu Kikuchi, Adv. Mater. ( 2017) 29 , 1702354 describes a compound of formula A that exhibits ferroelectric nematic behavior at temperatures ranging from about 45°C to 68°C.

[0008]

[0009] In addition, Nerea Sebastián, Luka Cmok, Richard J. Mandle, María Rosario dela Fuente, Irena Dreven ek Olenik, Martin opi Alenka Mertelj and Physical Review Letters (2020), 124, 037801, describe compounds of formula B that exhibit similar behavior at temperatures from about 120°C to 133°C.

[0010]

[0011] Xi Chen et al., PNAS (June 23, 2020), 117 (25) 14021-14031 presents only for N F Further comparison of these two substances available in the -LC phase. New N F The significance of the presence of the -LC phase is highlighted in ODLavrentovich, ProcNatAcadSciUSA (2020), 117(26), 14629-14631. The very high dielectric constants of these materials and some structural variations are reported in Li et al., Sci. Adv. 2021, 7.

[0012] Atsutaka Manabe, Matthias Bremer, Martin Kraska (2021): Ferroelectricphase at and below room temperature, Liquid Crystals Another ferroelectric nematic material of formula C was published in , 48, 1079-1086 (DOI10.1080 / 02678292.2021.1921867), which was described as having a ferroelectric nematic liquid crystal phase (N) with a temperature close to ambient temperature. F -LC phase). Here, ambient temperature, sometimes also called room temperature, narrowly refers to a temperature of 20°C.

[0013]

[0014] Ferroelectric nematic mixtures for room temperature applications have been disclosed in WO2022117552 A1.

[0015] Piezoelectric materials are required that are readily available and easily formed into any desired shape. They should also exhibit a strong response to pressure or shape changes. Summary of the Invention

[0016] The object of this invention is to provide novel polar materials with a combination of physical and electrical properties to meet the technical requirements in applications such as harvesting mechanical or thermal energy, sensors, piezoelectric devices, semi-solid forms of liquid crystals, actuators, and other new applications of liquid crystals.

[0017] Furthermore, the material aims to be thermally and photochemically stable under general conditions in the application field, particularly at room temperature and above and / or below 10K, 20K or greater.

[0018] Surprisingly, it has been found that N can be prepared without losing its ferroelectric behavior. F -LC phase piezoelectric gel. The material is suitable for piezoelectric applications.

[0019] In one aspect, the present invention relates to novel liquid crystal gels comprising ferroelectric nematic liquid crystals and suitable gelling agents having a molecular weight of 250 to 1000 g / mol.

[0020] The gels according to the invention are sufficiently stable and colorless. In particular, they are characterized by extremely high dielectric constants and especially by very high dielectric anisotropy (Δε), thus making them sensitive to external electric fields.

[0021] Furthermore, the gel used according to the present invention has a suitable operating temperature and a high clearing point. The liquid crystal gel exhibits a ferroelectric nematic liquid crystal phase over a significant temperature range (including ambient temperature).

[0022] The liquid crystal gels according to the present invention exhibit excellent dielectric properties. Ferroelectric nematic liquid crystal gels not only provide improved properties for energy harvesting and electric devices, but also have potential applications in other electrical and electronic devices.

[0023] Due to its superior properties, gels can function in many new technological fields and can be used for electro-optic purposes as capacitors, including supercapacitors, nonlinear optical elements, mechanical sensors, sensors for electric fields, storage devices, and electromechanical devices, including generators (i.e., energy harvesting devices, microphones) and actuators (including, for example, loudspeakers). The material can, for example, enable unconventional modes of energy harvesting from vibrational motion.

[0024] A second aspect of the invention relates to a piezoelectric element comprising the ferroelectric nematic liquid crystal gel described above. Specifically, the piezoelectric element comprises a mechanical substrate capable of imparting mechanical stress to the gel or receiving force from the gel. The substrate is brought into contact with the ferroelectric liquid crystal gel, wherein the gel generates an electric charge in response to mechanical stress or exhibits a response to an applied electric field. The piezoelectric element can be used in a variety of applications, including mechanical sensors or energy harvesting devices. When it responds to an electric field, it can be used as an actuator, for example, as an active element in a linear motor or (ultrasonic)wave generator.

[0025] In summary, this invention provides a solution to the challenges faced by traditional energy harvesting devices and piezoelectric elements by utilizing the unique properties of ferroelectric nematic liquid crystal gels. It represents a significant advancement in the field of energy harvesting and mechanical sensor devices and has potential applications in a variety of electrical and electronic devices.

[0026] High dielectric conductivity enables excellent physical properties. A high (relative) dielectric constant is also particularly advantageous for dielectrics in capacitors, as it induces high capacitance in specific electrode regions. Furthermore, gels exhibit very low conductivity and, due to their self-gelling properties, are superior to conventional high-ε... r Materials like barium titanate are unique in their gel properties. These properties advantageously distinguish them from liquid and solid materials. Once formed, the gel is stable but can be reformed at any time through heat-cooling cycles, making its damage repairable. In contrast, conventional solid piezoelectric materials are prone to cracking under irreversible and unrepairable thermal or mechanical stress.

[0027] The gel can be formed from a liquid state for coating substrates. Its flexible nature allows it to adapt its form to any substrate or surface after formation. Therefore, very close contact can be formed with electrodes. In a preferred embodiment of the invention, the gel is used to form a capacitor.

[0028] Liquid crystal gels can also be used in principle for displays based on the principle of twisted cell, host-guest effect, deformation effect of alignment phase DAP or ECB (electrically controlled birefringence), IPS (in-plane switching) effect or dynamic scattering effect.

[0029] Ferroelectric nematic liquid crystal gels exhibit unique spontaneous polarization and piezoelectric behavior, with values ​​that are no different from or even better than those of existing polarized polymers (e.g., PVDF) or rigid, brittle inorganic materials (e.g., zirconium titanate PZT). Like all ferroelectric materials, they also exhibit pyroelectric properties.

[0030] N F The combination of phase and physical gel network allows N F The phase transforms into anisotropic ferroelectric soft solid. (This is in contrast to pure N.) F In contrast, FLNC gel does not exhibit flow and is mechanically stable, allowing for easier handling of liquid ferroelectric LC materials. Furthermore, the resulting elasticity enables reversible deformation and thus facilitates durable mechanical energy harvesting. Compared to typical ceramic (PZT) or polymer (PVDF) ferroelectric materials, N... F The low elastic modulus of -LC gels leads to higher mechanical deformation under similar forces and thus greater changes in effective spontaneous polarization. Due to the inverse piezoelectric effect, the applied electric field causes N... F-LC gels deform and therefore can act as electromechanical actuators (electrostriction). Compared to existing thermoelectric and piezoelectric materials, N F A key advantage of -LC gels is that they are produced via simple, adaptable, and sustainable low-temperature processing through reversible gelation.

[0031] This invention also includes the use of the gel in electrical and electronic components. While gel factors for liquid crystals have been previously described in other patents and publications, combinations of gel factors with ferroelectric nematic liquid crystals have not been reported. In summary, this invention discloses novel and usable ferroelectric nematic liquid crystal gels and their potential uses in a variety of electrical and electronic devices. Repeated heating and cooling cycles at any time renew the gel and reset its alignment. Applying force / moving electrodes compresses the gel, resulting in charge movement and thus energy harvesting.

[0032] In a preferred embodiment, during its preparation, the ferroelectric gel is preferably oriented by external means (electric field, alignment layer) under slow temperature changes to impose an orientation order in the gel network and / or in the director of the LC phase. A gel with polarization and uniform alignment of the gel fibrous structure or liquid crystal director improves polarization (asymmetry of alignment relative to the electrodes). This can further improve the resulting piezoelectric effect. A piezoelectric element is preferred, wherein the liquid crystal gel is aligned with a preferred orientation of at least one component of the group consisting of a gel factor and a ferroelectric nematic liquid crystal, preferably the gel factor. More preferably, the gel in the piezoelectric element comprises a gel factor having a fibrous structure and said fibrous structure oriented in a preferred direction relative to the electrodes. Attached Figure Description

[0033] Figure 1 The graph shows the effective spontaneous polarization of gels gelled from base mixture 1 with different concentrations of gelling agent 1 (12-HOA). P S,eff And it was compared with a non-gelatinized reference sample in the temperature range of 20°C to 80°C. T / P s The graph (measured at 70 Hz) and the voltage of 200 V / mm show the effective spontaneous polarization during cooling. P s,eff The value. For liquid crystal gels, P s,eff The value has a maximum value (plateau shape) of the same order of magnitude as for the non-gelled reference liquid crystal material.

[0034] Figure 2The current response of a base mixture 1 gelled with 0.5 wt% 12-HOA is shown when slight pressure is applied and released. The isotropic sol mixture of the two components was filled into a 1.6 μm thick LC test cell, which had an ITO coating on both sides covered with a nylon insulating layer. An effective change in spontaneous polarization of approximately 35 nC / cm² was recorded when the top of the cell was gently pressed with an insulating glass rod. A reverse current response of similar size and shape was recorded upon release of pressure. Invention Details

[0036] Therefore, in one main aspect, the present invention relates to a liquid crystal gel comprising 91% by weight or more of a ferroelectric nematic liquid crystal mixture and 0.1% by weight to 9% by weight of a gelling agent having a molecular weight of 250 to 1000 g / mol (based on a total of 100% of the mixture). Preferably, the gel according to the invention comprises 0.15% by weight or more, more preferably 0.2% by weight or more of a gelling agent (including a plurality of such gelling agents). The gel preferably contains 7% by weight or less, more preferably 5% by weight or less of a gelling agent. Most preferably, the gel is used in an amount of 0.2% by weight to 1.0% by weight. The liquid crystal gel is preferably piezoelectric. For use at higher frequencies (e.g., above 10 Hz). 2 (Hz, sound wave / ultrasound) may typically require a higher amount of gelling factor, preferably 0.5% to 5% by weight.

[0037] Suitable gelling agents used in this invention typically have linking groups (such as partial groups -OH, -NHCO-, -NH-, or -CO-) capable of forming intermolecular hydrogen bonds within the molecule, optionally aromatic groups (such as phenyl groups for π-bonding), and preferably combinations of such groups. Preferably, the liquid crystal gel according to the invention comprises a gelling agent having at least one -OH or -NH- group and at least one structural element selected from -(CO)-, -(CO)O-, or -(CO)NH- groups, wherein these groups are capable of forming intermolecular hydrogen bonds. The gelling agent preferably comprises any of the following partial formulas.

[0038] or

[0039] in

[0040] R G1 It is an alkyl group having 1 to 18, preferably 2 to 5, carbon atoms, and n is a number from 5 to 15, preferably 7 to 12. Dashed lines indicate single bonds connecting the chain segment to the remainder of the individual gelling agent molecule. The gel according to the invention is preferably a liquid crystal physical gel. Compared to liquid crystal chemical gels, liquid crystal physical gels are gelled with non-polymer additives by definition.

[0041] The ferroelectric nematic LC mixture used as the basis for the gel is described in more detail below.

[0042] The ferroelectric nematic LC material preferably comprises at least two compounds having the molecular structure of Formula I.

[0043] I

[0044] in

[0045]

[0046] R 1 It is an alkyl group having 1 to 12 carbon atoms, preferably 1 to 8, more preferably 1 to 6, and most preferably 1 to 5 carbon atoms, wherein, furthermore, one or more CH2 groups in these groups can be independently converted to each other by -C≡C-, -CF2-O-, -OCF2-, -CH=CH-, , , , , The O / S atoms are replaced by -O-, -S-, -(CO)-O-, or -O-(CO)-, in such a way that the O / S atoms are not directly connected to each other, and in addition, one or more H atoms can be replaced by halogens, or represent H.

[0047] X is CN, F, CF3, -OCF3, -NCS, or Cl, preferably CN or F.

[0048] L 1 It is H or CH3.

[0049] Z 1 It is CF2O or -(CO)-O- or a single bond, preferably CF2O or -(CO)-O-, most preferably -(CO)-O-.

[0050] and

[0051] Z 2 It is CF2O or -(CO)-O- or a single bond, preferably -(CO)-O- or a single bond.

[0052] Ferroelectric media for use in gels preferably contain at least 30% by weight of a compound of formula I, more preferably 40% by weight, even more preferably 50% by weight, and most preferably 90% by weight, 95% by weight, or 98% by weight or greater of a compound of formula I.

[0053] More preferably, the present invention uses a mixture comprising the following as a ferroelectric nematic liquid crystal mixture.

[0054] One or more compounds of formula IA, 15% or more by weight.

[0055]

[0056] One or more compounds of formula IB, 15% or more by weight.

[0057]

[0058] and one or more compounds selected from formulas IC-1 to IC-3, 15% by weight, preferably 20% by weight or more.

[0059]

[0060] in

[0061] X 1B Indicates -CN or -NCS, preferably -CN.

[0062] X 1C This indicates -CN, F, CF3, -OCF3, -NCS, SF5, or O-CF=CF2, preferably -CN or F, and most preferably CN.

[0063] Z 1A and Z 1B Each can be represented independently as -(CO)-O- or -CF2-O- or a single bond.

[0064] Preferably -(CO)-O- or -CF2-O-,

[0065] Z 2A and Z 2B Each can be represented independently as a single bond, -(CO)-O-, or -CF2-O-.

[0066] Preferably a single bond,

[0067] Z 1C and Z 2C One of the two groups represents -(CO)-O- or -CF2-O- and the other represents a single bond.

[0068] Preferably Z 1C It is -(CO)-O- or -CF2-O- and Z 2C It's a single key.

[0069] L 1A L 1B and L 1C Each can be independently represented by H or CH3, preferably H.

[0070] L 2A It is F or H, preferably F.

[0071] L 2C It is F or H, preferably F.

[0072]

[0073]

[0074] Where L 8B This indicates an alkyl, alkoxy, or alkoxyalkyl group, each having 1 to 7 carbon atoms, preferably CH3, OCH3, OCH2CH3, CH2OCH3, CH2OCH2CH3, CH2CH2OCH3, CH2CH2OCH2CH3, or CH2CH2CH2OCH3.

[0075]

[0076]

[0077] m, n are 0, 1, or 2, where (m + n) is 2.

[0078] R 1A R 1B and R 1C Each of these groups independently represents an alkyl group having 1 to 12 C atoms, preferably 1 to 8, more preferably 1 to 6, and most preferably 1 to 5 C atoms, wherein, furthermore, one or more CH2 groups in these groups may in each case be independently replaced by -C≡C-, -CF2-O-, -OCF2-, -CH=CH-, , , , , The O / S atoms are replaced by -O-, -S-, -(CO)-O-, or -O-(CO)-, in such a way that the O / S atoms are not directly connected to each other, and in addition, one or more H atoms can be replaced by halogens, or represent H.

[0079] Preferably R 1A R 1B and R 1C Independently, they are halogenated or unsubstituted alkyl groups having 1 to 10 C atoms, wherein, in addition, one or more CH2 groups in these groups may be replaced by -O-, -(CO)-O- or -CH=CH- in such a way that the O atom is not directly attached.

[0080] The percentage is provided when the entire medium accounts for 100% of the medium's weight.

[0081] The group R in their respective formulas IA, IB and IC-1 to IC-3 and their respective sub-formulas1A R 1B and R 1C Preferably, it represents an alkyl group having 1 to 8 carbon atoms, an alkoxy group having 1 to 8 carbon atoms, or an alkenyl group having 2 to 8 carbon atoms. These alkyl chains are preferably straight-chain, or they are preferably in the form of R... 1C In the case of branching by a single methyl or ethyl substituent, preferably at the 2- or 3-position. 1A R 1B and R 1C Particularly preferred are straight-chain alkyl groups having 1 to 7 carbon atoms or unbranched alkenyl groups having 2 to 8 carbon atoms, especially unbranched alkyl groups having 1 to 5 carbon atoms.

[0082] Alternative preferred group R 1A R 1B and R 1C It is selected from cyclopentyl, 2-fluoroethyl, cyclopropylmethyl, cyclopentylmethyl, cyclopentylmethoxy, cyclobutylmethyl, 2-methylcyclopropyl, 2-methylcyclobutyl, 2-methylbutyl, 2-ethylpentyl and 2-alkoxyethoxy.

[0083] Due to better solubility in liquid crystal base materials, they contain either branched or substituted end groups R. 1A R 1B and R 1C Compounds of formulas IA, IB, and IC1 to IC-3 can sometimes be very important. The group R... 1A R 1B and R 1C Preferably, they are straight chains.

[0084] Group R 1A R 1B and R 1C Each of the following portions is particularly preferred:

[0085]

[0086]

[0087] The following abbreviations are used for end bases:

[0088]

[0089] Preferred embodiments of the present invention relate to ferroelectric nematic liquid crystal media comprising one or more compounds selected from the formulas IA, IB, IC-1, IC-2 and IC-3 as defined above.

[0090] Another embodiment of the invention relates to a ferroelectric nematic liquid crystal medium comprising one or more compounds of formula IC-1 as defined above, preferably in the percentages and preferred formulations provided throughout this disclosure.

[0091] Further embodiments of the present invention relate to a ferroelectric nematic liquid crystal medium comprising one or more compounds of formula IC-3 as defined above, preferably in the percentages and preferred formulations provided throughout this disclosure.

[0092] In a preferred embodiment, the medium according to the invention preferably comprises one, two, three or more compounds of formula IA-1.

[0093]

[0094] Preferably selected from formulas IA-1 to IA-3, and preferably from the group consisting of formula IA-1:

[0095]

[0096]

[0097]

[0098] The parameters have their respective meanings given above, and preferably Z 1A It represents -CF2-O-.

[0099] In a preferred embodiment, the medium according to the invention preferably comprises one, two, three or more compounds of formula IB-1 and / or IB-2, preferably of formula IB-1.

[0100]

[0101] R 1B This indicates an alkyl group having 1 to 12 carbon atoms, preferably 1 to 7, more preferably 1 to 6, and most preferably 1 to 5 carbon atoms, wherein, furthermore, one or more CH2 groups in these groups may in each case be independently converted to -C≡C-, -CF2-O-, -OCF2-, -CH=CH-, , , , , The O / S atoms are replaced by -O-, -S-, -CO-O-, or -O-CO-, in such a way that the O / S atoms are not directly connected to each other, and in addition, one or more H atoms can be replaced by halogens, or represent H.

[0102] Preferably R 1BIt is a halosubstituted or unsubstituted alkyl group having 1 to 12 carbon atoms, wherein, in addition, one or more CH2 groups in these groups may be independently replaced by -C≡C- or -CH=CH- in each case.

[0103]

[0104] and

[0105] Z 1B Z 2B Independently represented as -(CO)-O- or -CF2-O-,

[0106] Preferably selected from the group consisting of the following formulas (Formulas IB-1-1 to IB-2-3):

[0107]

[0108] The parameters have their respective meanings given above, and, in particular, in equations IB-1-1 to IB-1-3,

[0109] Z 1B Preferably, it represents -CF2-O-;

[0110] Furthermore, specifically in formulas IB-2-1 and IB-2-2,

[0111] Z 2B Preferably, it represents -CF2-O-;

[0112] Furthermore, specifically in formula IB-2-3,

[0113] Z 2B Preferably, it represents -C(O)O-.

[0114] In a preferred embodiment, the medium according to the invention preferably comprises one, two, three or more compounds of the selected formulas IC-1-1 to IC-3-5:

[0115]

[0116] Where A 1C As defined above,

[0117] Preferably selected from the group consisting of formulas IC-1-1-1 to IC-3-5-2, more preferably selected from the group consisting of formulas IC-1-1-1, IC-1-1-2, IC-1-1-3, IC-1-1-4, IC-3-1-1, and IC-3-2-1:

[0118]

[0119]

[0120] The parameters have their respective meanings given above, and preferably...

[0121] L 1C H represents

[0122] Z 1C It represents -CF2-O- or -(CO)-O-, and

[0123] X 1C It indicates -CN or F, preferably -CN.

[0124] The particularly preferred compounds of formulas IC-1-1 to IC-1-4 used in the medium are compounds of the following formulas:

[0125]

[0126] The parameters are as defined above, preferably L. 1C It is H.

[0127] In a preferred embodiment of the invention, the medium comprises up to 100% one or more compounds, preferably three, four, five, six or more compounds selected from Group 1 compounds (the group consisting of compounds of formulas IA, IB and IC-1 / -2 / -3). In this embodiment, the medium preferably consists primarily of these compounds, more preferably substantially of these compounds, and most preferably, almost entirely of these compounds.

[0128] For the purposes of this invention, the following definitions apply to the specifications of the components of the composition, unless otherwise specified individually:

[0129] - "comprise": The concentration of the component under discussion in the composition is preferably 5% or more, particularly preferably 10% or more, and very particularly preferably 20% or more.

[0130] - "Mainly composed of": The concentration of the component under discussion in the composition is preferably 50% or greater, particularly preferably 55% or greater, and very particularly preferably 60% or greater.

[0131] - "consisting essentially of": The concentration of the component under discussion in the composition is preferably 80% or greater, particularly preferably 90% or greater, and very particularly preferably 95% or greater, and

[0132] - "consisting almost entirely of": the concentration of the component under discussion in the composition is preferably 98% or greater, particularly preferably 99% or greater, and very particularly preferably 100.0%.

[0133] Preferably, the medium according to this application satisfies one or more of the following conditions. These preferably include:

[0134] - 20% by weight or more of the compound of formula IA, more preferably 25% by weight, more preferably 27% by weight or more, and most preferably 32% by weight or more of the compound of formula IA.

[0135] - 17% by weight or more of a compound of formula IB, more preferably 20% by weight or more, more preferably 22% by weight or more, and most preferably 25% by weight or more of a compound of formula IB.

[0136] - 40% by weight or more of compounds selected from formulas IA and IB, more preferably 45% by weight, even more preferably 50% by weight or more, and most preferably 55% by weight or more of compounds selected from formulas IA and IB, i.e., the sum of compounds of formulas IA and IB is preferably at least the above values.

[0137] - 40% by weight or more, more preferably 50% by weight, more preferably 60% by weight or more, and most preferably 70% by weight or more of compounds selected from the group consisting of formulas IB, IC-1, IC-2, and IC-3, i.e., the sum of compounds of formulas IB, IC-1, IC-2, and IC-3 is preferably at least the above values.

[0138] - Selected compounds of formulas IC-1, IC-2, and IC-3, 20% by weight or more, preferably 25% by weight or more, more preferably 28% by weight, more preferably 32% by weight or more, and most preferably 34% by weight or more.

[0139] - 40% by weight or more, preferably 60% by weight or more, more preferably 70% by weight, more preferably 80% by weight or more, and most preferably 90% by weight or more of the selected compounds of formula IC-1,

[0140] - Optionally 2% by weight or more of compounds of formula ID (ID-1, ID-2, ID-3, ID-4), more preferably 5% by weight, more preferably 10% by weight or more, and most preferably 15% by weight or more of compounds of formula ID.

[0141] - One, two, three or more, preferably three or more compounds of formula IA-1-1, preferably compounds of formula DUUQU-nF, most preferably selected from the group consisting of compounds DUUQU-2-F, DUUQU-3-F, DUUQU-4-F, DUUQU-5-F, and DUUQU-6-F.

[0142] - One, two, three or more, preferably three or more compounds of formula IB-1, preferably compounds of formula GUUQU-nN and / or DUUQU-nN, most preferably selected from the group consisting of compounds GUUQU-2-N, GUUQU-3-N, GUUQU-4-N, GUUQU-5-N, GUUQU-6-N, GUUQU-7-N, DUUQU-2-N, DUUQU-3-N, DUUQU-4-N, DUUQU-5-N, and DUUQU-6-N.

[0143] - One, two, three or more compounds of formula IA-1-3, preferably compounds of formula GUUQU-nF, more preferably selected from the group consisting of compounds GUUQU-3-F, GUUQU-4-F and GUUQU-5-F.

[0144] - One, two, three or more compounds of the formula IB-1-3, preferably compounds of the formula DUUQU-nN, more preferably selected from the group consisting of compounds DUUQU-3-N, DUUQU-4-N and DUUQU-5-N.

[0145] - One, two, three or more compounds of formula IC-1-1, preferably compounds of formula MUZU-nN or MUQU-nN, more preferably selected from the group consisting of compounds MUZU-2-N, MUZU-3-N, MUZU-4-N and MUZU-5-N.

[0146] - One, two, three or more compounds of formula IC-3, preferably selected from formula MUU-nN or UMU-nN, more preferably selected from the group consisting of compounds MUU-3-N, MUU-4-N, MUU-5-F, UMU-3-N, UMU-4-N and UMU-5-N.

[0147] - One, two, three or more compounds of formula IC-1-1, preferably selected from the formula GUZU-nN or GUQU-nN, more preferably selected from the group consisting of compounds GUZU-3-N, GUZU-4-N, GUZU-5-F, GUQU-3-N, GUQU-4-N and GUQU-5-N.

[0148] - Compounds of one, two, three or more formulas IC-1-1-3 and IC-1-1-4, preferably IC-1-1-3-1 and IC-1-1-4-1, preferably UUZU-nN and / or UUQU-nN, most preferably selected from the group consisting of compounds UUZU-2-N, UUZU-3-N, UUZU-4-N, UUZU-5-N, UUZU-6-N, UUQU-2-N, UUQU-3-N, UUQU-4-N, UUQU-5-N and UUQU-6-N.

[0149] - and / or

[0150] One or more compounds selected from the group consisting of compounds DUZGU-1-F, DUZGU-2-F, DUZGU-3-F, DUZGU-4-F, or DUZGU-5-F.

[0151] Where n is 1, 2, 3, 4, 5, 6 or 7.

[0152] In another preferred embodiment of the invention, the compounds of formulas IA, IB, and IC-1 / -2 / -3 are first group compounds (Group 1 compounds). In this embodiment, the concentration of the first group compounds is preferably in the range of 70% or more, preferably 80% or more, more preferably 90% or more to 100% or less.

[0153] In addition to compounds of formulas IA, IB, and IC-1 / -2 / -3, the media according to the invention optionally, preferably mandatory, contain one, two, three, or more compounds selected from formulas ID-1 to ID-4.

[0154]

[0155] X D This indicates CN, F, CF3, -OCF3, NCS, SF5, or O-CF=CF2, preferably -CN, F, -CF3, -OCF3, -Cl, or -NCS, and most preferably F or CN.

[0156] L 1D L 2D L 3D L 4D L 5D L 6D and L 7DIndependently representing F and H, each having 1 to 7 carbon atoms, an alkyl, alkoxy, or alkoxyalkyl group, preferably H, F, CH3, OCH3, OCH2CH3, CH2OCH3, CH2OCH2CH3, CH2CH2OCH3, CH2CH2OCH2CH3, or CH2CH2CH2OCH3.

[0157] Z 1D and Z 2D The terms -(CO)-O-, -CF2-O-, and single bonds can be represented independently of each other, and preferably both represent -(CO)-O-.

[0158] R 1D This indicates an alkyl group having 1 to 12 carbon atoms, preferably 1 to 7, more preferably 1 to 6, and most preferably 1 to 5 carbon atoms, wherein, furthermore, one or more CH2 groups in these groups may in each case be independently converted to -C≡C-, -CF2-O-, -OCF2-, -CH=CH-, , , , , The O / S atoms are replaced by -O-, -S-, -(CO)-O-, or -O-(CO)-, in such a way that the O / S atoms are not directly connected to each other, and in addition, one or more H atoms can be replaced by halogens, or represent H.

[0159] Preferably R 1D It is a halosubstituted or unsubstituted alkyl group having 1 to 12 carbon atoms, wherein, in addition, one or more CH2 groups in these groups may be independently replaced by -C≡C- or -CH=CH- in each case.

[0160] R 2D This indicates an alkyl, alkoxy, or alkoxyalkyl group, each having 1 to 7 carbon atoms, preferably CH3, OCH3, OCH2CH3, CH2OCH3, CH2OCH2CH3, CH2CH2OCH3, CH2CH2OCH2CH3, or CH2CH2CH2OCH3.

[0161]

[0162] in

[0163] L 8D This indicates an alkyl, alkoxy, or alkoxyalkyl group, each having 1 to 7 carbon atoms, preferably CH3, OCH3, OCH2CH3, CH2OCH3, CH2OCH2CH3, CH2CH2OCH3, CH2CH2OCH2CH3, or CH2CH2CH2OCH3.

[0164] Preferably, it includes one or more of the following formulas: ID-1-1 to ID-2-1

[0165]

[0166] Among them, the variable group R 1D and L 8D As defined above.

[0167] The medium optionally further comprises one or more compounds selected from the group consisting of:

[0168] Preferably, the medium contains one or more compounds from Group 1 and Group 2.

[0169] Additional ferroelectric materials and similar compounds with high dielectric constants used in combination with the present material are selected from, for example, the following structures:

[0170]

[0171] The corresponding starting materials can generally be readily prepared by those skilled in the art using synthetic methods known from the literature, or are commercially available. The reaction methods and reagents used are, in principle, known from the literature. Additional reaction conditions are illustrated by working examples. Further preferred method variations not mentioned above are disclosed by way of examples or claims.

[0172] In this disclosure, a 2,5-disubstituted dioxane ring of the following formula is used.

[0173]

[0174] Preferably, it represents a 2,5-trans-configuration dioxane ring, i.e., the substituents are preferably located in the equatorial position in the preferred chair conformation. The 2,5-disubstituted tetrahydropyran of the following formula...

[0175]

[0176] Similarly, it preferably represents a tetrahydropyran ring in the 2,5-trans configuration, i.e., the substituents are preferably located at the equatorial position in the preferred chair conformation.

[0177] The liquid crystal medium used according to the present invention has a wide temperature range of ferroelectric nematic phase. It exhibits a ferroelectric nematic phase range at and above 20°C and below (ambient temperature). It covers a technically attractive range of at least 10°C to 50°C and significantly exceeds lower and / or higher temperatures. Therefore, it is highly suitable for all kinds of domestic or industrial applications, and has some limitations even outdoors. The medium exhibits a ferroelectric nematic phase at least in a temperature range of 20 Kelvin or greater, more preferably 30 K or greater, and most preferably 40 K or greater. The achievable combinations of temperature range, clearing point, low-temperature stability (LTS), (relative) dielectric constant, dielectric anisotropy, and optical anisotropy of the ferroelectric nematic phase of compounds containing formulas IA, IB, and IC-1 / -2 / -3 are far superior to those of such prior art materials. In cases of limited selection, previously only single compound materials with a limited ferroelectric nematic phase range were available.

[0178] Furthermore, the mixtures according to the invention typically exhibit a very wide nematic phase range with a clearing point of 65°C or greater.

[0179] The liquid crystal medium according to the invention preferably exhibits a temperature range of ferroelectric nematic phase of 20 degrees or more, preferably extending to 40 degrees or more, more preferably 60 degrees or more.

[0180] Preferably, the liquid crystal medium according to the invention preferably exhibits a ferroelectric nematic phase at 10°C to 30°C, more preferably 10°C to 40°C, even more preferably 10°C to 50°C, even more preferably 0°C to 50°C, and most preferably -10°C to 50°C.

[0181] In another preferred embodiment, the liquid crystal medium according to the invention preferably exhibits a ferroelectric nematic phase at 10°C to 40°C, more preferably 10°C to 50°C, even more preferably 10°C to 60°C, and most preferably 10°C to 70°C.

[0182] Preferably, the medium according to the invention has an ε of 700 or greater, more preferably 800 or greater, more preferably 15000, even more preferably 30000 or greater, and more preferably 35000 or greater. r Values ​​(at 20°C and 10 Hz).

[0183] These dielectric properties are realized when the dielectric is in the ferroelectric nematic phase. Dielectric properties may exhibit hysteretic behavior, especially at varying temperatures, and the values ​​obtained at a given temperature may depend on the material's history, i.e., whether the material is heated or cooled.

[0184] Among other things, this effect enables the device to operate in a bistable mode, which can be beneficially used in electro-optic devices, such as those known from ferroelectric smectic devices.

[0185] In addition to one or more compounds according to the invention, the liquid crystal medium according to the invention preferably contains 2 to 40, particularly preferably 4 to 20, compounds as additional components. Specifically, in addition to one or more compounds according to the invention, these media may also contain 1 to 25 components. These additional components are preferably selected from ferroelectric nematic or nematic (unidirectional or isotropic) materials.

[0186] The medium according to the invention preferably contains 1% to 100%, more preferably 10% to 100%, and particularly preferably 50% to 100% of compounds of formula IA and / or IB and / or IC-1 / IC-2 / IC-3 preferred for use according to the invention.

[0187] The present invention also relates to a method for preparing the liquid crystal gel described herein, wherein 91% by weight or more of a ferroelectric nematic liquid crystal mixture and 0.1% to 9% by weight of a gelling agent having a molecular weight of 250 to 1000 g / mol are combined and mixed with each other and with any other optional components or additives. The resulting mixture reaches 100% by weight.

[0188] The liquid crystal mixtures and gels according to the invention are prepared in a conventional manner. Typically, the desired amount of the component to be used in a smaller quantity is dissolved in the component constituting the main component, preferably at a high temperature. The solutions of the components can also be mixed in an organic solvent (e.g., acetone, chloroform, or methanol), and the solvent is removed again after thorough mixing, for example, by distillation. Furthermore, the mixtures can be prepared in other conventional ways, such as by using premixes, such as homologue mixtures, or using a so-called "multi-bottle" system.

[0189] The liquid crystal mixture and gel may also contain additional additives known to those skilled in the art and described in the literature. For example, 0 to 15%, preferably 0 to 10%, of pleochroic dyes, chiral dopants, stabilizers, or nanoparticles may be added. The individual compounds added are used at a concentration of 0.01% to 6%, preferably 0.1% to 3%. However, concentration data for other components of the liquid crystal mixture (i.e., liquid crystal or mesocrystalline compound) are given herein without regard to the concentrations of these additives.

[0190] The present invention also relates to electro-optic displays (particularly TFT displays having two planar parallel outer plates forming a cell together with a frame for switching integrated nonlinear elements of individual pixels on the outer plates, and ferroelectric nematic liquid crystal gel with positive dielectric anisotropy and high specific resistance located in the cell).

[0191] The term "alkyl" includes unbranched and branched alkyl groups having 1 to 12 carbon atoms, preferably 1 to 10 carbon atoms, particularly and preferably without branched groups methyl, ethyl, n-propyl, n-butyl, n-pentyl, n-hexyl, and n-heptyl, and alternatively, groups n-butyl, n-pentyl, n-hexane, and n-heptyl that are substituted with one methyl, ethyl, or propyl group. Groups having 1 to 5 carbon atoms are generally preferred.

[0192] The term "alkenyl" includes unbranched and branched alkenyl groups having up to 12 carbon atoms, particularly unbranched groups. Particularly preferred alkenyl groups are C2-C7-1E-alkenyl, C4-C7-3E-alkenyl, C5-C7-4-alkenyl, C6-C7-5-alkenyl, and C7-6-alkenyl, especially C2-C7-1E-alkenyl, C4-C7-3E-alkenyl, and C5-C7-4-alkenyl. Examples of preferred alkenyl groups are vinyl, 1E-propenyl, 1E-butenyl, 1E-pentenyl, 1E-hexenyl, 1E-heptenyl, 3-butenyl, 3E-pentenyl, 3E-hexenyl, 3E-heptenyl, 4-pentenyl, 4Z-hexenyl, 4E-hexenyl, 4Z-heptenyl, 5-hexenyl, 6-heptenyl, etc. Groups having 2 to 5 carbon atoms are generally preferred.

[0193] The expression "halogenated alkyl" preferably includes monofluoro or polyfluoro and / or monochloro or polychloro groups. Perhalogenated groups are included. Fluorinated alkyl groups are particularly preferred, especially CF3, CH2CF3, CH2CHF2, CHF2, CH2F, CHFCF3, and CF2CHFCF3. The expression "halogenated alkenyl" and related expressions are interpreted accordingly.

[0194] Above and below, percentage data are expressed as percentages by weight. Unless otherwise expressly stated, all temperature values ​​indicated in this application, such as, for example, melting point T(C,N), smectic (Sm) to nematic (N) phase transition T(S,N), and clearing point T(N,I), are indicated in degrees Celsius (°C), and all temperature differences are correspondingly indicated in degrees of difference (° or degrees). Furthermore, C = crystalline state, N = nematic phase, N... F = Ferroelectric nematic phase, Sm = smectic phase (especially SmA, SmB, etc.), Tg = glass transition temperature and I = isotropic phase. The data between these symbols represent the transition temperature. Δn represents optical anisotropy (589 nm, 20°C), and Δε represents dielectric anisotropy (1 kHz, 20°C).

[0195] Physical, physicochemical, and electro-optical parameters are determined by commonly known methods, especially as described in the manual "MerckLiquid Crystals - Licristal® - Physical Properties of Liquid Crystals - Description of the Measurement Methods", 1998, Merck KGaA, Darmstadt.

[0196] The presence of the ferroelectric nematic phase in the material was identified by differential scanning calorimetry (DSC) through observation of the texture under a polarizing microscope equipped with a hot stage for controlled cooling and corresponding heating, and further confirmed by the temperature dependence of the dielectric properties. The transition temperature was primarily determined by detecting the optical behavior under a polarizing microscope.

[0197] The dielectric anisotropy Δε of individual substances was determined at 20°C and 1 kHz. For this purpose, 5% to 10% by weight of the substance under investigation dissolved in a dielectric positive mixture ZLI-4792 (Merck KGaA) was measured, and the measurements were extrapolated to 100% concentration. The optical anisotropy Δn was determined at 20°C and a wavelength of 589.3 nm by linear extrapolation.

[0198] The relative permittivity (ε) of the material r The relative permittivity, particularly in the ferroelectric nematic phase, was directly determined by measuring the capacitance of at least one test cell containing the compound and having a cell thickness of 250 μm, both with vertical alignment and with planar alignment. Temperature was controlled by a Novocontrol Novocool system set to apply temperature gradients of + / -1 K / min; + / -2 K / min; + / -5 K / min; + / -10 K / min to the sample cell. Capacitance was measured by a Novocontrol alpha-N analyzer at frequencies of 1 kHz or 10 Hz, with typical voltages <50 mV reduced to 0.1 mV to ensure they were below the threshold of the compound under study. Measurements were performed both while one or more samples were heated and cooled.

[0199] In this application, unless otherwise expressly stated, the plural form of a term refers to both the singular and plural forms, and vice versa. Further combinations of embodiments and variations of the invention, as described, also derive from the appended claims or from a combination of several of those claims. Detailed Implementation

[0200] Example

[0201] The invention is described in detail through the following non-limiting embodiments.

[0202] The claims also disclose embodiments of the invention and other combinations of variations thereof.

[0203] The following embodiments illustrate the invention but are not intended to limit it. Those skilled in the art will be able to extract working details not detailed in the general description from the embodiments, generalize them based on general expertise, and apply them to specific problems.

[0204] Without further elaboration, it is believed that those skilled in the art can utilize the invention to its fullest extent using the foregoing description. Therefore, the previously preferred embodiments should be interpreted as illustrative only and in no way limiting the remainder of this disclosure.

[0205] From the foregoing description, those skilled in the art can readily identify the basic features of the present invention, and various changes and modifications can be made to adapt it to various uses and conditions without departing from its spirit and scope.

[0206] This applies to both a medium having its components (which may be a group of compounds and individual compounds) and a group of compounds having their respective components (compounds). The term "comprise" refers only to the concentration of an individual compound relative to the medium as a whole: the concentration of one or more compounds in question is preferably 1% or greater, particularly preferably 2% or greater, and very particularly preferably 4% or greater.

[0207] In this invention, "≤" means less than or equal to, preferably less than, and "≥" means greater than or equal to, preferably greater than.

[0208] For the present invention,

[0209]

[0210] This represents the trans-1,4-cyclohexyl group.

[0211]

[0212] This represents a mixture of cis- and trans-1,4-cyclohexylene, and

[0213]

[0214] It represents 1,4-phenylene.

[0215] For the purposes of this invention, the term "dielectrically positive compound" refers to a compound having a Δε > 1.5, the term "dielectrically neutral compound" refers to a compound having a Δε ≤ -1.5, and the term "dielectrically negative compound" refers to a compound having a Δε < -1.5. The dielectric anisotropy of the compound is determined by dissolving 10% of the compound in a liquid crystal matrix and, in each case, determining the capacitance of the resulting mixture at 1 kHz with both vertical and planar alignment in at least one test cell having a cell thickness of 20 μm. The measurement voltage is typically 0.5 V to 1.0 V, but always below the capacitance threshold of the corresponding liquid crystal mixture (material) under study.

[0216] The host mixtures for the dielectric positive and dielectric neutral compounds were ZLI-4792, and the host mixture for the dielectric negative compounds was ZLI-2857, both sourced from Merck KGaA, Germany. The values ​​for the respective compounds to be studied were obtained by extrapolating the change in dielectric constant of the host mixture after the addition of the compound to be studied to 100% of the compound used. The compound to be studied was dissolved in the host mixture at a concentration of 10%. For this purpose, if the solubility of the substance was too low, the concentration was gradually halved until the study could be carried out at the desired temperature.

[0217] If desired, the liquid crystal medium according to the invention may also contain additional additives, such as, for example, stabilizers in typical amounts. Based on the total amount of the mixture, the total amount of these additives used is preferably 0% or more to 10% or less, particularly preferably 0.1% or more to 6% or less. The concentration of the individual compounds used is preferably 0.1% or more to 3% or less. The concentrations of these and similar additives are generally not considered when specifying the concentrations and concentration ranges of the liquid crystal compounds in the liquid crystal medium.

[0218] For the purposes of this invention, unless otherwise expressly stated, all concentrations are indicated as percentages by weight and relate to the respective mixtures or mixture components as a whole (again, as a whole, unless otherwise expressly stated). In this context, the term "mixture" describes the liquid crystal medium.

[0219] Unless otherwise explicitly stated, use the following symbols:

[0220]

[0221] The following examples illustrate the invention but do not limit it. However, they demonstrate to those skilled in the art preferred ideas of mixtures of the compounds preferably used, their respective concentrations, and combinations thereof. Furthermore, these examples illustrate accessible properties and combinations of properties.

[0222] The definition of structural elements by abbreviations is used in the acronyms of chemical compounds:

[0223] Table A: Ring Elements

[0224]

[0225]

[0226]

[0227] Table B: Bridging Units

[0228]

[0229] Table C: End groups

[0230]

[0231] Where n and m are each integers, and the three dots “…” are placeholders for other abbreviations from the table.

[0232] In addition to compounds of formulas IA, IB and IC-1 / -2 / -3, the mixtures according to the invention preferably contain one or more of the compounds mentioned below.

[0233] Use the following abbreviations:

[0234] (n, m, k, and l are each an integer, preferably 1 to 9, preferably 1 to 7; k and l may also be 0 and are preferably 0 to 4, more preferably 0 or 2, and most preferably 2; n is preferably 1, 2, 3, 4, or 5; in the combination "-nO-", it is preferably 1, 2, 3, or 4, preferably 2 or 4; m is preferably 1, 2, 3, 4, or 5; in the combination "-Om", it is preferably 1, 2, 3, or 4, more preferably 2 or 4. The combination "-lVm" is preferably "2V1".)

[0235] For the present invention and the following embodiments, the structure of the liquid crystal compound is indicated by acronyms, which are transformed into chemical formulas according to Tables A to C above. All groups C n H 2n+1 C m H 2m+1 and C l H 2l+1 Or C n H 2n C m H 2m and C l H 2lAll are straight-chain alkyl or alkylene groups, each having n, m, and l C atoms respectively. Preferably, n, m, and l are 1, 2, 3, 4, 5, 6, or 7 independently of each other. Table A shows the codes for the ring elements of the compound's core, Table B lists the bridging units, and Table C lists the meanings of the symbols for the left-hand and right-hand end groups of the molecule. Acronyms consist of the code for the ring element with an optional linking group, followed by the first hyphen and the code for the left-hand end group, and the second hyphen and the code for the right-hand end group. Table D shows the illustrative structure of the compound along with its respective abbreviation.

[0236] Table D

[0237] Exemplary and preferred compounds of formula IA

[0238]

[0239] Exemplary and preferred compounds of formula IB

[0240]

[0241] Exemplary and preferred compounds of formula IC-1

[0242]

[0243] Exemplary and preferred compounds of formula IC-3

[0244]

[0245] Other compounds used optionally

[0246]

[0247]

[0248]

[0249]

[0250]

[0251]

[0252]

[0253]

[0254]

[0255]

[0256]

[0257]

[0258]

[0259]

[0260] Table E

[0261] Exemplary, preferred molecular gelling factors (the structures drawn include mixtures of stereoisomers, but pure stereoisomers are preferred)

[0262]

[0263]

[0264]

[0265]

[0266] Mixture Examples

[0267] The mixture representing the ferroelectric nematic gel is prepared by combining a gelling agent with a suitable mesocrystalline material. Typically, the ferroelectric nematic liquid crystal mixture is combined with the gelling agent and mixed at a temperature above the gelation temperature until a homogeneous solution is obtained. Alternatively, the components can be mixed in any order suitable for the processing. The homogenized mixture is then rapidly cooled below the nematic / ferroelectric-nematic transition temperature (T0). FerroN The temperature at which the gel forms. Below the gelation temperature, the gel forms spontaneously and reversibly from the mixture.

[0268] Alternatively, the homogenized mixture can be oriented by external means (electric field, alignment layer) and gelled under slow temperature changes in order to impose an orientation order in the gel network and in the director of the LC phase.

[0269] The following liquid crystal bulk mixture (base mixture) was used for gel preparation.

[0270] Basic Mixture 1

[0271] The following mixture (M-1) was prepared and studied.

[0272]

[0273] c Values ​​during cooling

[0274] Basic Mixture 2

[0275] The following mixture (M-2) was prepared and studied.

[0276]

[0277] c Values ​​during cooling

[0278] Basic Mixture 3

[0279] The following mixture (M-3) was prepared and studied.

[0280]

[0281] c Values ​​during cooling

[0282] Basic Mixture 4

[0283] The following mixture (M-4) was prepared and studied.

[0284]

[0285] c Values ​​during cooling

[0286] These are the relative permittivity ε of any physical substance known to the author to date. r The highest value.

[0287] Basic Mixture 5

[0288] The following mixture (M-5) was prepared and studied.

[0289]

[0290] c Values ​​during cooling

[0291] Basic Mixture 6

[0292] The following mixture (M-6) was prepared and studied.

[0293]

[0294] c Values ​​during cooling

[0295] Basic Mixture 7

[0296] The following mixture (M-7) was prepared and studied.

[0297]

[0298] c Values ​​during cooling

[0299] Basic Mixture 8

[0300] The following mixture (M-8) was prepared and studied.

[0301]

[0302] c Values ​​during cooling

[0303] Basic Mixture 9

[0304] The following mixture (M-9) was prepared and studied.

[0305]

[0306] c Values ​​during cooling

[0307] Basic Mixture 10

[0308] The following mixture (M-10) was prepared and studied.

[0309]

[0310] c Values ​​during cooling

[0311] Basic Mixture 11

[0312] The following mixture (M-11) was prepared and studied.

[0313]

[0314] c Values ​​during cooling

[0315] Basic Mixture 12

[0316] The following mixture (M-12) was prepared and studied.

[0317]

[0318] c Values ​​during cooling

[0319] Basic Mixture 13

[0320] The following mixture (M-13) was prepared and studied.

[0321]

[0322] c Values ​​during cooling

[0323] Basic Mixture 14

[0324] The following mixture (M-14) was prepared and studied.

[0325]

[0326] c Values ​​during cooling

[0327] Basic Mixture 15

[0328] The following mixture (M-15) was prepared and studied.

[0329]

[0330] c Values ​​during cooling

[0331] Mixture Example 16

[0332] The following mixture (M-16) was prepared.

[0333]

[0334] c The value during cooling.

[0335] Mixture Examples

[0336] The liquid crystal gel is prepared by combining the aforementioned basic mixture with gelling agents from Table E above or Table 1 below.

[0337] Table 1. Gel Factors (Structure, Molecular Weight):

[0338]

[0339] The mixtures were prepared from base mixtures 1 to 15 together with the gelling agents listed in Table 1. Unless otherwise specified, the content of the gelling agent is 0.5% by weight.

[0340] To test whether the gelation process was successful, N F A mixture of -LC and a suitable gelling agent is filled into a glass tube as an isotropic liquid. After cooling and waiting for gelation to complete, the tube is angled at approximately 45° with the opening facing downwards. Gelation is considered successful when no flow occurs for at least 24 hours.

[0341] The resulting mixture forms a gel. The results are presented in Table 2 below, showing the selected results for different amounts and types of gelling agents and different base mixtures.

[0342] Table 2. Examples of mixtures of liquid crystal gels:

[0343]

[0344]

[0345] Evaluation of the gel (methods a to h):

[0346] a) Microscopic research

[0347] To study gelled N F The optical properties of the LC were studied by filling the material in a 1.6 μm thick (20 μm for piezoelectric testing) polyimide-coated LC cell (purchased from the Military University of Technology in Warsaw, Poland), in which the director n was pre-tilted to the frictional direction with a small to non-existent pre-tilt alignment. Furthermore, both sides of the cell were coated with a conductive ITO layer. The study was conducted using a Leica DM 2700 P polarizing microscope equipped with an Instec HCS302 heating stage controlled by an MK1000 temperature unit. Images were taken using a PixelLink PL-D752CU camera.

[0348] b) X-ray diffraction

[0349] Small-angle X-ray measurements (SAXS) were performed using a SAXSess MC2 system (Anton Paar) and a Mythen 2 K detector (Dectris). X-ray radiation (Cu-K) , = 0.15418 nm) was generated by an ISO-DEBYEFLEX 3003 X-ray generator (Seifert).

[0350] The Bruker AXS NanoSTAR system (Cu-K) is equipped with a heating stage controlled by a 2216e (Eurotherm) and a cooling box from Huber, Unichiller. Wide-angle X-ray measurements were performed using a Goebel mirror monochromator, a 100 µm spot collimator, and a VÅNTEC-500 detector. The sample was placed in a 0.7 mm outer diameter capillary tube of Glas #14 (Hilgenberg).

[0351] c) Electro-optic measurement

[0352] To measure gelled N F -LC's response to electrical stimulation will N F A mixture of LC and gelling agent was heated to an isotropic sol state and filled into an LC test chamber (IPS1000A035uX003) from Instec. These were 3.5 μm thick and coated with an antiparallel triboelectric alignment layer. Furthermore, two ITO strips, each 1 cm long, were aligned in-plane to generate an electric field. The gap between these strips was 1 mm. The temperature was controlled by a TMS 94 (LINKAM) connected to an LTS 350 hot stage (LINKAM).

[0353] Spontaneous polarization was obtained by recording the current response while a triangular AC voltage at a frequency of 70 Hz was applied [K. Miyasato, S. Abe, H. Takezoe, A. Fukuda, E. Kuze, Jpn. J. Appl. Phys. 1983, 22 [L661-L663.] The voltage was generated using a 33500B waveform generator from KEYSIGHT and amplified using a 7500 amplifier from Krohn-Hite. The voltage response was amplified and noise reduced using an SR560 low-noise preamplifier from STANFORD RESEARCH SYSTEMS. The signal was recorded using a DSO-X 2004A oscilloscope from KEYSIGHT. A 0.5 kΩ current was used to calculate the current from the voltage response. Resistor.

[0354] d) Dielectric measurement

[0355] Dielectric constant measurements were performed using a Hewlett-Packard 4192A LF impedance analyzer. Samples were filled into 20 µm thick polyimide-coated cartridges, rubbed parallel to both sides, from the Military University of Technology, Warsaw. The cartridges had an ITO coating and an effective area of ​​5 mm x 5 mm, connected to the analyzer via copper wire. For all measurements, 0.1 V was used. rms The voltage. The temperature is controlled by a NOVOTHERM temperature control box from Novocontrol.

[0356] e) Dynamic scanning calorimetry

[0357] Samples were transferred in 3–5 mg batches to Perkin Elmer crucibles (part number B016-9321). Measurements were performed using a DSC8000 instrument from Perkin Elmer. Measurements were taken at 1, 5, and 20 K min. -1 The heating / cooling rates were each cycled twice. For analysis, the software Pyris was used.

[0358] f) High-resolution FFTEM

[0359] Cryofracture electron microscopy replicas of the gel were prepared using the EMBAF060 cryofracture and etching system from Leica. At room temperature, a small sample was sandwiched between two copper meshes (hexagonal 360-mesh) and two copper plates (4.5 mm × 3.0 mm). The sample was then immersed in liquid ethane cooled by liquid nitrogen. The frozen and fractured sample was rapidly transferred to the vacuum chamber of the BAF060. At -150°C, the surface was replicated by a layer of Pt / C deposited at a 45° angle (#2 nm) and stabilized at a 90° angle by a layer of pure carbon (#20 nm).

[0360] High-resolution TEM images were captured using a Spectra 300 from Thermo Fisher Scientific. An accelerating voltage of 300 kV was used.

[0361] g) Piezoelectric effect measurement

[0362] N F An isotropic sol mixture of LC and gelling agent is filled into a mold to obtain a disc shape. After gelation, the disc is placed in a custom-built device consisting of stepper motors that move a copper die up and down to press the gel onto a copper plate. The two copper parts are brought into contact so that the voltage generated via the piezoelectric effect can be measured.

[0363] h) Measurement of inverse piezoelectric effect

[0364] The gel was prepared similarly to g), but instead of applying force, an electric field was applied while the gel's response was measured using a Newtonian meter. This electric field reached a maximum of 200 V / cm. The voltage was generated using a 33500B waveform generator from KEYSIGHT and amplified using a 7500 amplifier from Krohn-Hite.

[0365] Evaluation results:

[0366] Through POM (characteristic texture) and SAXS (characteristic scattering properties), the origin of N can be observed. F Phase and typical maximum scattering from gel fibers), FFEM (presence of gel fibers, optical verification), dielectric spectrum (NF (high dielectric constant in phase) and Ps measurement (N F - The ferroelectricity test of the LC gel demonstrates the coexistence of the ferroelectric nematic phase and the gel (successfully gelled). Compared with the non-gelled N... F Compared to -LC, it shows that spontaneous polarization decreases with increasing gel factor content, but still exists up to very high gel factor contents of up to 9 wt.%. A wide range of gel factor concentrations leading to ferroelectric gels is advantageous because mechanical and thermal properties also change with the amount of gel factor (higher mechanical stability and elastic modulus, and higher gel-sol transition temperature, with increasing gel factor concentration). Therefore, materials with customized properties are possible for a given application.

[0367] Device Example 1: Piezoelectric Element and its Electrical Response

[0368] To prove the gelation of N F -LC exhibits a piezoelectric response. Base mixture 1 was mixed with 0.5 wt% 12-HOA and heated to a sol-isotropic state (>70°C). The mixture was then transferred to a 20 μm thick LC test cell coated with ITO on both sides. After cooling and waiting 5 min for gelation to occur, the cell was brought into contact with a preamplifier via copper wire for noise reduction. The amplifier output was then connected to an oscilloscope. Gently pressing the cell with an insulating glass rod resulted in a 0.5 kJ / mol test. The change in voltage across the resistor. From this, the current can be calculated (see...). Figure 2 ).

[0369] The current response is polar and indicates a change in effective spontaneous polarization of approximately 35 nC / cm².

[0370] Device Example 2: Inverse Piezoelectric Effect (Force Implied by Electric Field)

[0371] Furthermore, the inverse piezoelectric effect was investigated. When an electric field was applied to the gel of the previous embodiment, the gel itself exerted a force of up to 0.16 N. This force was partly due to the electrostatic forces between the copper plates, which were amplified by the high dielectric constant, and partly due to the inverse piezoelectric effect.

[0372] Device Example 3: Inverse Piezoelectric Effect (Sound Generation and Recording)

[0373] The base mixture 1 was mixed with 3.5 wt% 12-HOA and heated to a sol isotropic state (>70°C). The mixture was then transferred to a 6 μm thick LC test chamber made of glass coated with ITO on both sides and allowed to cool and form a gel phase.

[0374] An AC power supply (100 V, 5 kHz sine wave) is attached to the box. An audible sound is generated. Furthermore, the device is connected face-to-face to a piezoelectric sensor according to device embodiment 1 by gluing them together. The resulting electrical response of the sensor is matched to the power supply using an oscilloscope. The phase and frequency of the sine wave are matched.

Claims

1. A liquid crystal gel comprising 91% by weight or more of a mixture of ferroelectric nematic liquid crystals and 0.1% by weight to 9% by weight of a gelling agent having a molecular weight of 250 to 1000 g / mol.

2. The liquid crystal gel according to claim 1, which exhibits a ferroelectric nematic phase.

3. The liquid crystal gel according to claim 1 or 2, wherein, The gelling factor has at least one -OH or -NH- group and at least one structural element selected from -(CO)-, -(CO)O- or -(CO)NH-.

4. The liquid crystal gel according to one or more of claims 1 to 3, comprising one or more compounds of formula I, I in R 1 It is an alkyl group having 1 to 12 carbon atoms, preferably 1 to 8, more preferably 1 to 6, and most preferably 1 to 5 carbon atoms, wherein, Furthermore, one or more CH2 groups among these groups can be independently converted to -C≡C-, -CF2-O-, -OCF2-, -CH=CH-, in each case. , , , , The O / S atoms are replaced by -O-, -S-, -(CO)-O-, or -O-(CO)-, in such a way that the O / S atoms are not directly connected to each other, and in addition, one or more H atoms can be replaced by halogens, or represent H. X is CN, F, CF3, -OCF3, -NCS, Cl. L 1 It is H or CH3. Z 1 It is CF2O or -(CO)-O- or a single bond. and Z 2 It is CF2O or -(CO)-O- or a single bond.

5. The liquid crystal gel according to any one of claims 1 to 4, which exhibits a relative permittivity ε of 700 or greater at 20°C and 1 kHz. r .

6. The liquid crystal gel according to one or more of claims 1 to 5, comprising: One, two, three or more compounds selected from formulas ID-1 to ID-4, in X D This indicates CN, F, CF3, -OCF3, NCS, SF5, or O-CF=CF2. L 1D L 2D L 3D L 4D L 5D L 6D and L 7D Independently representing F and H, each having 1 to 7 carbon atoms, alkyl, alkoxy, or alkoxyalkyl. Z 1D and Z 2D The terms -(CO)-O-, -CF2-O-, and single bonds can be represented independently of each other, and preferably both represent -(CO)-O-. R 1D This refers to an alkyl group having 1 to 12 carbon atoms, wherein... Furthermore, one or more CH2 groups among these groups can be independently converted to -C≡C-, -CF2-O-, -OCF2-, -CH=CH-, in each case. , , , , The O / S atoms are replaced by -O-, -S-, -(CO)-O-, or -O-(CO)-, in such a way that the O / S atoms are not directly connected to each other, and in addition, one or more H atoms can be replaced by halogens, N(CH3)2, or H. R 2D This indicates an alkyl, alkoxy, or alkoxyalkyl group, each having 1 to 7 carbon atoms, preferably CH3, OCH3, OCH2CH3, CH2OCH3, CH2OCH2CH3, CH2CH2OCH3, CH2CH2OCH2CH3, or CH2CH2CH2OCH3. in L 8D The alkyl, alkoxy, or alkoxyalkyl groups each having 1 to 7 carbon atoms are preferred to be CH3, OCH3, OCH2CH3, CH2OCH3, CH2OCH2CH3, CH2CH2OCH3, CH2CH2OCH2CH3, or CH2CH2CH2OCH3.

7. The liquid crystal gel according to one or more of claims 1 to 6, which exhibits a ferroelectric nematic phase at a temperature of at least 10°C to 30°C.

8. The liquid crystal gel according to one or more of claims 1 to 7, which exhibits a ferroelectric nematic phase at least in a temperature range of 20 Kelvin.

9. The liquid crystal gel according to at least one of claims 1 to 8 is used in electromechanical devices, the electromechanical devices including generators, mechanical sensors and actuators, for electro-optical purposes or for use in capacitors.

10. Use of the liquid crystal gel according to at least one of claims 1 to 8 for energy harvesting applications.

11. Use of the liquid crystal gel according to at least one of claims 1 to 8 for nonlinear optical elements or storage devices.

12. A piezoelectric element comprising a ferroelectric nematic liquid crystal gel between electrodes.

13. The piezoelectric element according to claim 12, wherein, The liquid crystal gel is a liquid crystal gel according to one or more of claims 1 to 8.

14. The piezoelectric element according to claim 12 or 13, wherein, The liquid crystal gel is aligned in a preferred orientation of at least one of the components of the group consisting of gelling agents and ferroelectric nematic liquid crystals.

15. A method for preparing a liquid crystal gel according to any one of claims 1 to 8, wherein, The mixture comprises at least one ferroelectric nematic liquid crystal mixture or a component thereof, and 0.1% to 9% by weight of a gelling agent having a molecular weight of 250 to 1000 g / mol, and any other optional components or additives thereof.

16. A method for preparing a liquid crystal gel having an orientation direction of a gelling agent according to any one of claims 1 to 8, wherein, The components of the gel are cooled to below the gelation temperature under the influence of an external electric field to form a gel.

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