Patent Grant
11015120
Ferroelectric liquid crystals (FLCs) materials, because of fast switching speed, low driving voltages, and high optical quality, are in high demand for various display and photonic applications. FLCs, because of spontaneous polarization, are known to have faster response time than nematic liquid crystals. However, they suffer through the low optical contrast due to the occurrence of geometrical defects. Recently FLC electro-optical modes have been developed that provide sufficiently good optical quality. Most of these known electro-optical effects in FLCs work on the principle of retardation introduced by the half-wave-plate mode, which can be defined by equation (1):
d=λ/2Δn (1)
and where
Δn=n∥−n⊥ (2)
where the FLC cell thickness (d) at a given wavelength (λ) is inversely proportion to the FLC birefringence (Δn). Most commercially available FLC materials possess Δn in the range of 0.14-0.18 at λ=0.54 μm and, therefore, require a cell gap of 1.5 to 2 μm to achieve acceptable conditions of the half wave plate, at least for the maximum spectral sensitivity of the human eye at λ=0.54 μm. It is extremely difficult to maintain a high fabrication yield for such a small cell gap. The lowest appropriate thickness is around 3-3.5 μm, that, according to eq. (1), required Δn values at λ=0.54 μm in a range of 0.077-0.09.
Recently, an electro-optical effect for the FLCs has been disclosed, where the helical pitch is comparable to the FLC layer thickness and the anchoring energy of the commanding surfaces balances the elastic energy of the FLC helix. This electro-optical effect called an Electrically Suppressed Helix FLC (ESHFLC) mode displays high optical contrast that is comparable to nematic LC.
A strategic way to reduce the Δn of FLCs is by use of a mixture of low birefringence compounds. The total Δn of such FLC mixtures, for low Δn materials, can be written as:
Δn=ΣxiΔni (3)
where xi is the molar fraction and Δni represents the birefringence of the ith component provided that the Δni are related to the same reduced temperature below, which is proportional to the molar impact of each component. Formula (3) is generally correct only for low Δni values.
The birefringence of the organic material strongly correlates with molecular polarizability, mainly depending on the lengthening of molecular conjugation of π-electron systems. Therefore, strategies to reduce Δn include inclusion of saturated units in the core of LC molecules, such as exchange of aromatic rings with cyclohexane or cyclohexene and breaking of the conjugation by means of aliphatic spacers.
FLC materials are typically a mixture of several of compounds, often 4, 5, or more, with the components of the mixture being divided into several groups depending on their specific role. The major part of FLC mixture is the compound showing smectic-C liquid crystal phase, providing a range of basic characteristics, such as a temperature interval of the ferroelectric phase, viscosity, dielectric and optical properties. Another important component of the FLC mixture can be represented by compounds that are non-mesogenic, often being chiral components of FLCs, or exhibit liquid crystal phases other than SmC types. Although in a few cases such non-SmC and non-mesogenic compounds can enhance the SmC range of the FLC mixture, although typically these components suppress the desired phase, and their content is typically minimized to avoid diminishing the working temperature interval of FLC materials. The degree of Δn adjustment by minor components of FLC is naturally very small.
The effective Birefringence depends on the type of electro-optical effect in a FLC. Birefringence (Δn) is determined by equation (2) only in a low-twisted FLC, where helical pitch (p) is comparable or higher than cell gap, as disclosed in Srivastava et al., J. Soc. Inform. Display 2015, 23(6) 253-72. For highly-twisted FLC (DHF, Kerr effect), where p<< than the cell gap, the effective birefringence (Δneff.) depends on the smectic tilt angle and can be described as:
Δneff.=n∥n⊥/[n⊥2+(n∥2−n⊥2)sin2θ sin2φ]1/2−n⊥ (4)
The typical value of the tilt angle for DHF effect is in the range of 0˜32-37°, and therefore, the effective Δn in the cell is about two times lower, than the estimations from eq. 1 valid for the SSFLC effect. Thus, required Δn values at λ=0.54 μm calculated by eq. 1, in the case of DHFLC can be in the range of 0.15-0.18. However, currently available DHFLC materials based mainly on three-ring aromatic (or heteroaromatic) compounds, thereby possessing Δn values of 0.2 or more.
In liquid crystal materials with considerably slower optical switching, such as nematic LCs or block-polymer smectic-C, low Δn values are well-known. However, non-polymeric low Δn FLCs are still a big challenge. To date, the vast majority of known SmC liquid crystals possess Δn of about 0.14 or higher. Using LiqCryst 5.1 and its database only 1,506 of the 14,260 SmC compounds were found to contain at least one aliphatic ring and only one compound comprises exclusively aliphatic units. This sole example is
as disclosed in Frach et al. Liquid Crystals 1989, 5(1), 197-207 where a more ordered modification of SmC, namely SmE phase, which has little practically applicability due to its very high viscosity. A second example, when SmC phase was found for fully aliphatic compounds is disclosed in Das et al. Chem. Phys. Let. 2005, 410 417-22 for a mixture of two steroids the SmC* phase is induced, however, its small range of concentrations and narrow temperature range leave this mixture unsuited for practical applications. Cholesterol esters are weak chiral dopant to FLC materials in respect of spontaneous polarization induction.
Based on the analysis of the literature, the most widespread classes of LC cores can be ranked accordingly to their conjugation length within molecules allowing the generalization of the effect of conjugation length on Δn as shown in
Embodiments of the invention are directed to low birefringence ferroelectric liquid crystal (FLC) mixtures, which have a plurality of components and show birefringence in the range 0.05 to 0.14, which are suitable for the modern displays and photonic devices. Because of low birefringence, the cell gap, which corresponds to half waveplate retardation of the display cell for the FLCs, can be tuned from 1.5 μm to 4 μm to reduce the fabrication complexity and chromatic distortion of electro-optical modulation. The FLC mixtures possess a wide temperature range. The characteristic of the FLC mixture can be tuned by the concentration of different constituents of the mixture. The helical pitch of the FLC mixtures, depend on the chemical structure of the chiral components and its concentration can be varied from 100 nm to 10 μm. Depending on composition of the low birefringence FLC, the smectic tilt angle can be varied between 17° to 45° and the spontaneous polarization can be tuned in a wide range to meet requirements for different electro-optical modes. With this flexible component choice giving different material characteristics, the FLC is applicable for a wide variety of electro-optical effects.
Embodiments of the present invention are directed to low birefringence ferroelectric liquid crystals (FLC's) where the birefringence can be adjusted in the range of 0.05-0.014 by controlling the constituents of the material. The FLCs are composed of a plurality of components, where a first component is a thermotropic liquid crystal and a second component is a low birefringence material, such as, but not limited to, a smectic-C material. The low Δn FLC mixtures eliminates conjugated aromatic molecules comprising two or more than two aromatic or heteroaromatic rings and avoiding extended conjugation with more than one π-bonds, such as, but not limited to, C═C, C═O, or an ester group. In an embodiment, the chiral fragments of components for the FLC mixtures possess different types of compounds in one or both of the oligomers termini or wings, W1 and/or W2, and the FLC has liquid crystals phases. In an embodiment of the invention the FLC mixture displays a smectic-C phase.
In embodiments of the invention, the low birefringence ferroelectric liquid crystal mixture that shows birefringence (Δn) in the range 0.05 to 0.14 comprises a plurality of components, a first component being a thermotropic liquid crystal, possibly a smectic-C phase, while a second component being a low birefringence material with Δn of 0.02 to 0.1, where either can be a thermotropic liquid crystal, where the low birefringence ferroelectric liquid crystal has the formula:
In embodiments of the invention, the low-birefringence components of the ferroelectric liquid crystal mixture aromatic or heteroaromatic rings where R1-R4 are not conjugated or cross-conjugated with one another. The low birefringence components of the ferroelectric liquid crystal mixture has aromatic or heteroaromatic ring (R1-R4), independently, in conjugation with no more than one double bond of type C═Z, where Z is one of C, N or chalcogen.
In an embodiment of the invention, the first components of the low birefringence FLC mixture are of smectic-C or SmC* types liquid crystals. Other non-SmC mesogenic components, such as, but not limited to, nematic, cholesteric, SmA, and SmB, can be included to adjust phase transition temperatures or the total Δn of the mixture, as shown in
Preparation of PAC and PAC-PC type liquid crystals can be carried out as in reaction scheme 1.
Preparation of CPEH (X1═H) and CPEF (X1═F) type liquid crystals can be carried out as in reaction scheme 2.
Preparation of PCP type liquid crystals can be carried out as in reaction scheme 3.
Phenacylic esters of cyclohexancarboxylic acids (PAC) were firstly disclosed in Petrov et al. Liquid Crystals, 1999, 26(8), 1141-62, however, the mesomorphic properties did not achieve optimal values of parameters needed for various electro-optical modes, having a SmC phase transition that starts above 100° C. PAC and PAC-PC comprising LC materials, according to an embodiment of the invention, possess a wide range for phase transition of the of SmC phase starting from about 60 to 70° C., rather than the high upper temperature limit of typical SmC phases for PAC and PAC-PC compounds, that occurs above 100° C., as indicated in Table 2 and 3, below. Consistent with the chemical formula of the PAC compounds, the Δn is around 0.1. In this embodiment of the invention, a large SmC temperature phase transition range and low Δn occurs. The addition of a chiral component to the body of the PAC allows a chiral mesogens capable of inducing a desirable value of spontaneous polarization, see, for example, entries 1, 2, 4-7, 9-12 in
aAll phase transitions are obtained in the current invention except Entries 7-9, from Petrov et al.;
bC - is 1,4-trans-disubstituted cyclohexane ring; B is 1,4-disubstituted benzene ring; A2 is a single bond.
The PAC series has an orthogonal SmB or another high-ordered phase below SmC (see Table 2).
Compounds with low Δn, other than PAC, reveals some degree of an adverse effect regarding SmC phase. In some cases, the SmC phase becomes inferior to a SmB phase and shows further depression with higher concentrations of dopant with lower birefringence, for example, derivatives of cholesterol and cyclohexyl-bicyclohexyl carboxylate. Working mixtures cannot have a total unsaturated dopant content in excess of 10-12 mol. % for compounds DCHA-3 and Chol-5CHA and no more 5 mol. % for Chol-9. Among other dopants, phenylcyclohexane carboxylates (PCH), so-called Demus' esters, appeared to be superior. In another embodiment of the invention, a short SmC phase is mixed with PCH materials, where mixtures of PAC with nematic PCHs are well suited, for example those of
The trend for SmC-SmA transitions is roughly that of the corresponding phase transitions of individual components, and remains sufficiently high within the entire range of concentrations. However, because of rather a high birefringence of phenylpyrimidines, about 0.14, its content should not exceed 40 mol. %, and is preferably below 20 mol. % to have appropriate Δn values for working mixtures.
Most electro-optical effects for ferroelectric liquid crystals have different requirement for p0 and θC, as summarized in Table 4, below. These effects can be controlled by the concentration of chiral components or dopants. Furthermore, dopants having a large transverse dipole directly attached to a chiral center provide sufficiently large pitches. To this end, many compounds according to embodiments of the invention, include, but not limited to, polar units like C*—F, C*—CF3, C*—O—C, where C* denotes asymmetric, chiral carbon atom. In an embodiment of the invention, cholesterol derivatives that do not possess C*—F, C*—CF3 fragments, do not induce any significant spontaneous polarization or small helical pitch to the FLC mixture when these compounds are used as Δn reducers in the current invention.
For helix formation, lower values of HTP are typical for mono-substituted dopants that contain a single chiral fragment at one of the terminal positions of dopant molecule. With respect to the chemical structure of the chiral fragment, according to an embodiment of the invention, structures can be ranked in the sequence C*—F<C*—O—C<C*—CF3.
Typically, θC values increase with concentration of chiral dopant (CD) often reaching saturation at a CD level specific for each selected pairs of “CD-FLC host”. In general, the chemical structure of the CDs effect on the θC value varies by the chemical class. In an embodiment of the invention, different types of chiral dopants effect the smectic tilt angle in the proposed FLC host where: small angles (θC<10°) are induced by compounds bearing one chiral fragment, preferably a C*—F fragment and useful for fine adjustment of smectic tilt angles that are induced by other dopants; large angles (θC>30°) are induced using chiral dopants having three-ring cores with two chiral fragments derived from 2-CF3-1-alkanols; and intermediate angles (20°±9, for example 22.5°) that are induced with combinations of two types dopant for larger and smaller angles or using a PCP type dopant esterified with chiral 2-octanol or other C4-C16 chiral alcohol. The required amount of chiral component is similar to the content of non-chiral constituents, which effects phase transition and Δn values of the FLC materials. Surprisingly, for example, phenacylic ester bearing a chiral 2-fluorooctanol group shows a mesophase sequence similar to its non-chiral analogs, as shown in
The electro-optics of the low Δn FLC has been studied in different electro-optical modes. The mixture number 7-191-M3, shown in Example 8, below, was infiltrated in the liquid crystals cell with planar alignment and thickness 3 μm. The cell was placed between the crossed polarizer and switching time was determined as a function of the applied voltage, and the measured Δn for mixture 7-191-M3 is about 0.110. The voltage dependence of the switching time is shown in
The FLC mixture can display a tilt angle that varies with temperature, as illustrated in
In an embodiment of the invention, PAC and PAC-PC type FLC mixtures display a Δn value of 0.105 to 0.12, which are the lowest Δn for a wide range of SmC based on the climatic f. These types of host components are summarized in Table 5, below. The PAC and PAC-PC type FLC mixtures can have SmC ranging from 34-48 to 90-140° C. In an embodiment of the invention, the SmC range can be 48 to 90-92° C. These mixtures easily overcool, up to room temperature, revealing a monotropic SmB phase or a higher order phase below the SmC phase. The SmB-SmC phase transitions are almost linearly dependent on the individual components.
In the next embodiment of the invention, the PAC-PC types of compounds do not possess a SmB phase, moreover, in the mixtures with PAC this unwanted SmB is fully suppressed, as can be seen in
In an embodiment of the invention, another Δn and melting point reducers is included. By equation 3, above, an estimate of the content of various Δn reducers in binary mixtures with PAC or PAC-PC needed to reduce the inherent birefringence of the host from 0.105-0.12 to a target Δn value of 0.1 is shown in
A representative list of compounds that can be used as Δn reducers is given in Table 1, where there are almost no LC compounds that combine a SmC phase with Δn values less than 0.08. Therefore, any such compounds chosen as Δn reducer will suppress the SmC phase of the host, and limit their content to 50 or, in the best case, 60 mol. %. All tested compounds showing lower Δn than PAC or PAC-PC reveal adverse effect on the SmC phase. In some cases, the SmC phase becomes inferior to the SmB phase and shows greater depression at high concentrations of dopant.
To facilitate comparison and selection of additives for basic SmC hosts comprising PACs and/or PAC-PCs, the influence of the dopants on the SmC and SmB phase transition temperatures for the mixtures is estimated by the slope of the corresponding line on the phase diagrams, as indicated in Table 6, below.
*)Decreasing of the corresponding phase transition on temperature (° C.) per 10 mol. % of dopant added to PAC, PAC-PC, or PAC-PC mixtures prepared according to Example 13, below
In general, SmC phase thermal stability of PAC type of materials is sensitive to some dopants required to improve Δn, mp, or other parameters. The relatively low concentrations of about 15-20% of bicyclohexyl carboxylate (DCHA-3) or cholesterol esters can fully suppress SmC phases, as indicated in
Among other dopants, those which suppress SmB phase to a greater extent than SmC phase are useful. As can be seen from the Table 6, these requirements are satisfied using CPEH, short-tail Demus esters, and some cholesterols esters. These dopants can be used as Δn reducers for FLC mixtures in concentration up to 10-15 mol. % with an acceptable reduction in the upper-temperature limit for the SmC*. The two rings phenylpyrimidines are effective SmB suppressors, see for example,
A chiral dopant (CD), being necessary to induce ferroelectric properties in a FLC host and the CD affects the SmC phase transitions. Phenacylic esters bearing the chiral 2-fluorooctanol group shows mesophases sequence similar to their non-chiral analogs, and the phase diagram pattern, see
Most electro-optical effects for the ferroelectric liquid crystals have different requirement for p0 and θC, as summarized in Table 7 below, which can be controlled by the types and/or concentration of the chiral dopants.
Dopants with rather large transverse dipole directly attached to the chiral center provide sufficiently large Ps. This is the case for most dopants described herein, but the invention is not limited to typical polar units, such as C*—F, C*—CF3, C*—O—C, where C* denotes an asymmetric chiral carbon. Cholesterol derivatives those do not possess C*—F, C*—CF3 fragments do not induce either a significant spontaneous polarization or a short helical pitch in the FLC mixture and these compounds are used as Δn reducers.
The ability for helix formation is indicated by lower values of HTP, which is typical for mono-substituted dopants, those containing only one chiral fragment at one of the terminal positions of a dopant molecule. With respect to the chemical structure of the chiral fragment, the sequence C*—F<C*—O—C<C*—CF3 correlates to increasing HTP.
Typically, the θC value increases with concentration of CD, often reaching saturation of CD content specifically for a given selected pair with a “CD-FLC host”. In general, the influence of the chemical structure of the chiral dopant on θC values varies among chemical classes. The smallest angles, θC<10°, are induced by compounds bearing one chiral fragment, preferably C*—F. These dopants are useful for fine adjustment of smectic tilt angles induced by other dopants. The intermediate tilt angles, around 20° including 22.5°, can be induced by combinations of the two types dopant mentioned above or with one dopant of the PCP type esterified with chiral 2-octanol. The highest angles, θC>30°, can be induced using chiral dopants having a three-ring core and two chiral fragments, such as, but not limited to, fluorine-containing CDs, such as, but not limited to derivatives of 2-CF3-1-alkanols.
The electro-optics of the low Δn FLCs, as illustrated Examples 2-5, 7-8 and 14, below, find application in so-called low-twisted FLC modes, such as SSFLC or ESH modes, whereas Examples 15-18, below 17-20 are useful for DHFLC's as indicated in
For a mixture, such as that of Example 5, below, filled in a similar cell as that disclosed, above, the typical characteristics of the surface stabilized ferroelectric liquid crystal mode are displayed with a measured Δn of ˜0.109, as illustrated in
For a mixture, such as that of Example 8, below, was infiltrated in the liquid crystals cell with planar alignment and thickness 3 μm. Thereafter, the cell was placed between crossed polarizers and the time of application of current, as a function of the applied voltage, was studied to understand the nature of the electro-optical mode. The measured Δn for the mixture is ˜0.110. The voltage dependence of the time under current, the switching on time, is shown in
Synthesis
Demus esters (n-CHA-m), Bicyclohexane derivatives (BC), Phenylcyclohexane carboxylic acid esters (PCH), Bicyclohexyl carboxylic acid esters (DCHA), Phenylpyrimidine derivatives (PP) Cholesterol derivatives (Chol-n) are commercially available materials and used as is. The 4,4″-terphenyl derivatives, preferably A1=A2=COO bridge group (TDA) were obtained as it was described in Pozhidaev et al Journal of Materials Chemistry C, 2016, 4, 10339-46.
The synthesis of phenacylic esters of PAC and PAC-PC types, were carried out as indicated in Scheme 1, above.
The synthesis of phenacylic esters of type PAC and PAC-PC were carried out in the manner disclosed in Huang et al. Synthetic Communications, 1988, 18(10), 1167-70, except for the isolation and purification. A mixture of a corresponding carboxylic acid (5.5 mmol), phenacyl bromide (5 mmol), potassium carbonate (5.5 mmol), polyethylene glycol (M=4000, 1.1 mmol) and acetonitrile (15 ml) was stirred at room temperature for 20 min and refluxed about 1.5 hours. The reaction mixture was evaporated to dryness at reduced pressure, suspended in 50 mL of 1:1 v/v benzene-hexane mixture, filtered through short pad of silica gel and washed twice with 30 ml of the same solvent, evaporated to dryness, crystallized twice from acetonitrile or 2-propanol and dried in vacuo. The products were dissolved in a minimal volume of benzene and filtered through short path of silica gel on a PTFE sub-micro filter (0.2 μm pore size). The silica gel was washed with benzene, evaporated to dryness under a steam of nitrogen, and dried in vacuo. Thermal characteristics and phase sequences for these obtained compounds are given in Tables 2 and 3, above.
To degassed the solution of corresponding phenacyl bromide (29.9 mmol) in 50 mL of dry benzene under N2 atmosphere, 6 mL of DAST (44.9 mmol) was added at ambient temperature. The mixture was stirred for 20 hours, then heated up to 45° C. for 20 hours till reaction was completed (monitored by GC-MS). Then the mixture of 20 g of NaHCO3 in 200 mL of ice-water was added, organic materials was extracted with DCM, washed with water, dried over Na2SO4, filtered and evaporated to dryness. The oil residue comprising 95-96% of a main component by GC-MS, was used for the next step without additional purification.
A mixture of crude 2-bromo-1,1-difluoro-1-arylethanes (21 mmol), 8.4 g of KOAc (86 mmol), 4.1 g 18-crown-6 (16 mmol) in dry DMF was refluxed till reaction was completed as indicated by GC-MS analysis, typically 12-16 hours. The reaction mixture was evaporated to dry at reduced pressure, dissolved in 130 mL of EtOH, and a solution of 8 g NaOH in 40 mL water was added. The mixture was refluxed for 30 min and the EtOH was evaporated. To the residual water was added HCl and the pH was adjusted to 3-4. Organic materials were extracted with DCM, washed with water, dried over Na2SO4, and evaporated to dryness. The product was isolated by column chromatography on silica gel using hexane-ethyl acetate mixture as eluent. After evaporation the semi-solid product was purified by crystallization from MeCN. Yield 30-35%.
To a degassed solution of the corresponding phenacyl bromide (2.55 mmol) in 10 mL of dry trifluoroacetic acid under N2 atmosphere was added 1.02 mL of triethylsilane (6.37 mmol) at 5-10° C. The mixture was stirred for 25 hours, then heated to 60° C. for 30 min. A 100 mL portion of ice-water was added, and organic materials was extracted with DCM, washed with water, dried over Na2SO4, filtered, and evaporated to dryness. The oil residue, having 86-88% of a main component by GC-MS analysis, was purified by flash chromatography on silica gel/hexane and used without additional purification.
A mixture of the crude 2-bromo-1-arylethanes, 1.0 g of KOAc (10.2 mmol), 0.6 g PEG-4000 in 40 mL of dry DMF was refluxed till reaction was completed as monitored by GC-MS, typically 16 hours. The reaction mixture was evaporated to dryness at reduced pressure, purified by flash-chromatography on silica gel/benzene-hexane (1:1 v/v), evaporated to dryness, dissolved in 25 mL of EtOH and a solution of 2.5 g KOH in 20 mL of water was added. The mixture was refluxed for 2 hours and cooled. EtOH was evaporated to residue water and hydrochloric acid was added to achieve a pH 3-4. Organic materials were extracted with DCM, washed with water, dried over Na2SO4, and evaporated to dryness. The product was isolated by column chromatography on silica gel using hexane as eluent. After evaporation of the oil, product was crystallized, with a yield 85% from the phenacyl bromide.
To an ice-water cooled mixture of 0.66 mmol of the corresponding 1-aryl-2-hydroxyethane, 0.68 mmol of the appropriate carboxylic acid, and a few mg of DMAP in 6 mL of dry DCM, a solution of 165 mg of DCC (0.79 mmol) in 2 mL of DCM was added dropwise. The reaction mixture was stirred overnight, filtered through a short path of silica gel, washed with 15 mL of DCM, and evaporated to dryness. The residue was crystallized from acetonitrile or 2-propanol and dried in vacuo. The product was dissolved in a minimal volume of benzene and filtered through a short path of silica gel on a PTFE 0.2 μm pore size filter. The silica gel was washed with benzene, evaporated to dryness under a steam of nitrogen and dried in vacuo. Thermal characteristics and phase sequences for thus obtained compounds are given in Table 5, below.
Synthesis of cholesterol trans-4-alkylcyclohexane carbxylates was performed essentially as described for esterification of 1-aryl-2-hydroxyethanes, above.
Cholesterol trans-4-pentylcyclohexane carbxylates was obtained in 56% yield and showed the following phase transitions: Cr 117-118° C. SmA. 208.5 N* 237 Iso.
To a refluxed solution of phenylmagnesium bromide, obtained from 9.0 ml bromobenzene (86.1 mmol) and 2.8 g Mg (115 mmol) in 110 ml THF, was added dropwise the solution of 10 g 4-phenylcyclohexanone (57.4 mmol) in 40 mL dry THF for 40 min. The reaction mixture was refluxed for 6 hours, cool down to ambient temperature and poured into 50 mL of AcOH in ice water. Organic materials were extracted into EtOAc and evaporated to dryness. The solid residue was refluxed with 0.2 g of 4-toluensulfonic acid in 250 mL toluene using a Dean-Stark water trap for 10 hours, cooled, filtered through a short path of silica gel, and evaporated to dryness. Solid residue was dissolved in 150 mL of dry THF, flashed with N2, 0.5 g of 10% Pd/C was added, and the mixture hydrogenated till H2 absorption was completed, approx. for 15 h. Catalyst was filtered, washed with toluene, filtrate was evaporated to dryness and solid residue was crystallized from 200 mL EtOH to furnish 4.97 g of needle crystals, yield 37%.
To a suspension of 4.5 g anhydrous AlCl3 (34 mmol) cooled to 2° C. in 20 ml DCM 6.0 mL of (COCl)2 (69 mmol) was added at that temperature. The reaction mixture was stirred for 10 min and solution of 1,4-diphenylcyclohexane in 70 ml DCM was added drop wise for 1 hour at temperatures below 5° C. and stirred overnight. The reaction mixture was poured onto 400 g of an ice-HCl mixture, the volatile solvent evaporated, and the solid residue was filtered, washed with water, and dried. The product was purified using extraction with hot acetonitrile in a Soxlet apparatus, the extract was cooled, and fine crystal filtered and dried. Yield 3.98 g.
A mixture of 0.895 g of 1,4-bis(4-carboxyphenyl)cyclohexane (2.5 mmol) and a few drops of DMF was refluxed in 15 mL of SOCl2 until the solution become homogeneous and an additional 3 hours. Then reaction mixture was evaporated to dryness, the residue dried in vacuo, dissolved in 30 mL of refluxing toluene to which a solution of 2 mL of S-2-octanol (12.6 mmol) was added. A solution of 3 mL pyridine (22 mmol) in 9 mL of toluene was added. The reaction mixture was refluxed for an additional 5 hours, filtered through a short path of silica gel, the silica washed with toluene (3×10 mL), and the combined filtrate was evaporated to dryness. The solid residue was crystallized twice from acetonitrile to yield 0.42 g (31%) of colorless fine crystals, mp 68.4-69.4° C.
In like manner, 0.40 g of 1,4-bis(4-(2-flouro-1-octylcarbonyloxyphenyl)cyclohexane was obtained in a 35% yield from 0.9 g of S-2-flouro-1-octanol and 0.644 g of 1,4-bis(4-carboxyphenyl)cyclohexane. Phase transitions are Cr 72.6 SmA 111.0 Iso.
In like manner, 0.25 g of 1,4-bis(4-(2-trifluoromethyl-1-heptylcarbonyloxyphenyl)-cyclohexane was obtained in a 40% yield (mp 54.1-54.9° C.) from 0.307 g of 1,4-bis(4-carboxyphenyl)cyclohexane and 0.870 g of S-1,1,1-trifluoro-2-octanol 0.25 g of 1,4-bis(4-(2-trifluoromethyl-1-heptylcarbonyloxyphenyl)cyclohexane.
*) Temperature dependencies of these parameter are shown in FIG. 46.
*) Temperature dependencies of these parameter are shown in FIGS. 46.
*)Temperature dependencies of these parameters are shown in FIGS. 34-37.
*)Temperature dependencies of these parameters are shown in FIGS. 38-39.
All patents, patent applications, provisional applications, and publications referred to or cited herein, supra or infra, are incorporated by reference in their entirety, including all figures and tables, to the extent they are not inconsistent with the explicit teachings of this specification.
It should be understood that the examples and embodiments described herein are for illustrative purposes only and that various modifications or changes in light thereof will be suggested to persons skilled in the art and are to be included within the spirit and purview of this application.
This application claims the benefit of U.S. Provisional Application Ser. No. 62/499,527, filed Jan. 30, 2017, which is herein incorporated by reference in its entirety.
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| 20180216004 | Vashchenko | Aug 2018 | A1 |
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| Number | Date | Country | |
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| 20180216004 A1 | Aug 2018 | US |
| Number | Date | Country | |
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| 62499527 | Jan 2017 | US |
