KR101828670B1 - Novel triazole-based compound, method for preparing the same and ferroelectric columnar liquid crystals comprising the same - Google Patents

Abstract

The present invention relates to a novel triazole-based compound and a ferroelectric liquid crystal material containing the same. The ferroelectric liquid crystal material of the present invention can form a spontaneous polarization structure smaller than a Smectic liquid crystal having a conventional layer structure, and thus can be applied to a terra-class memory device.

Description

TECHNICAL FIELD The present invention relates to a novel triazole-based compound, a method for producing the same, and a ferroelectric liquid crystal material comprising the same.

The present invention relates to a novel triazole-based compound, a process for producing the same, and a ferroelectric liquid crystal material containing the same.

Terabyte memory devices are basically high capacity memory semiconductors with a capacity of one thousandths of gigabyte semiconductors. They can store more than 16,000 times 64M DRAMs and more than 4,000 times more than 256M DRAMs. Researches on ferroelectric liquid crystals as a material of such a terra-class memory device are under way.

Conventional ferroelectric liquid crystals are mostly composed of Smectic liquid crystals having a layered structure, which is inadequate for application to a terra-class memory device requiring high density. Therefore, a ferroelectric liquid crystal material has been studied as a candidate material applicable to a terra class memory device.

Ferroelectric columnar liquid crystals (FCLCs) are useful materials for nonvolatile memory devices because they are spontaneously organized into nanoscale regions and polarization switching by electric field due to dynamic behavior. In addition, nanoscale cylinder assemblies enable ultra-terabit memory to be as small as 1 cm ² . Despite these advantages, it is still difficult to obtain a switchable and stable axial polarization, and design of a rapid switching mode is still required.

Until recently, many ferroelectric liquid crystal materials consisting of chiral-rod or bent-core molecules have been reported. However, switching occurs in each smectic layer (1-bit memory region), limiting its application to memory.

The ferroelectric cylindrical liquid crystal material (FCLC) was very difficult to devise because of the two contrasting characteristics, namely, the stability and dynamics of the axial polarization must be precisely manipulated. Thus, while only one FCLC example using amide-based dendron has been reported until recently, the polarization switching frequency is too low (~ 0.008 Hz) to be applied to memory devices. In addition, some of the columnar LCs exhibiting ferroelectric behavior for a short time (less than 100 s) were found to be paraelectric.

For applications in memory devices, the polarization switching speed is as important as the LC morphology. In order to increase the switching speed, it is necessary to use a simpler switching motif.

The present inventors have found that 1,2,3-triazolyl compounds exhibit stable axial polarization due to steric and hydrogen bonding action derived from bulky dendron through head-to-tail stacking And a novel rapid polarization switching mode corresponding to an electric field can be achieved by simple rotation of the triazole group, thereby synthesizing the 1,2,3-triazole compound of the present invention.

U.S. Publication No. US 2015-0368530 A1 (December 24, 2015)

In order to solve the problems of the prior art, it is an object of the present invention to provide a ferroelectric liquid crystal material capable of dramatically increasing the polarization density, achieving a stable axis polarization, and designing a rapid switching mode, in comparison with a ferroelectric smectic liquid crystal .

The first aspect of the present invention provides a 1,2,3-triazole-based compound represented by the following formula (1) or (2) which is a morpholine isomer.

[Chemical Formula 1]

 (2)

In the formulas (1) and (2), R ₁ to R ₆ are alkyl groups having 1 to 20 carbon atoms having the same carbon number.

In one embodiment, R ₁ to R ₆ are the same alkyl group of 1 to 12 carbon atoms. The alkyl group may be linear or branched.

In the above formulas (1) and (2), R ₁ to R ₆ are (CH ₂ ) ₅ CH ₃ or (CH ₂ ) ₇ CH ₃ , but it is not limited thereto.

The compounds of the formulas (1) and (2) are represented by the non-center symmetry of 1,2,3-triazole derivatives designed by click chemistry, which is a binding reaction connecting two molecules through interaction between two molecules of reactors It is a noncentrosymmetric cisoid conformer.

The compounds of formulas (1) and (2) are crystalline and are isotropic liquid crystals.

The compound of Formula 1 has a melting point of 100.8 ° C and the compound of Formula 2 has a melting point of 63.3 ° C.

We have investigated 1,2,3-triazolyl units, known as the products of click chemistry, as potential candidates for ferroelectric liquid crystal (FCLC) compounds with axial polarization stability and dynamics.

Figure 1 relates to a ferroelectric liquid crystal based on 1,2,3-triazole units. As shown in FIG. 1, the Smectic liquid crystal is divided into a columnar liquid crystal having axial polarization, and the memory capacity is rapidly increased (see FIG. 1A). For example, for a device with a size of 1 cm ² , the memory capacity using a cylindrical structure (3 nm diameter) is theoretically 10 terabits, 10 ⁶ times more than the capacity based on the Smectic structure.

The 1,2,3-triazolyl compound has a dipole moment as large as 4.55 D, and the axial polarization can be stabilized due to its hydrogen bonding ability (FIG. 1B).

Thus, the present inventors have designed liquid crystal compounds 1 and 2 based on a 1,2,3-triazolyl bond (Figure 1c). The compound is characterized in that the rotation of the C-C bond connecting the naphthalenyl ring and the triazolyl ring produces a cis form and a trans isomer. Of these, the cis isomer is non-centrosymmetric, so the dipole mottent is nonzero.

A second aspect of the present invention relates to a process for producing 2,6-diethynylnaphthalene; And

Reacting the 2,6-diethynylnaphthalene with a compound represented by the following formula (3): < EMI ID =

(3)

In Formula 3, R is an alkyl group having 1 to 20 carbon atoms having the same carbon number.

As the 2,6-diethynylnaphthalene,

2-methyl-3-butyn-2-ol is reacted with 2,6-dibromonaphthalene to give 4,4 '- (naphthalene- Lt; / RTI > And 4,4 '- (naphthalene-2,6-diyl) bis (2-methylbut-3-yn-2-ol) with a basic substance.

The basic substance may be NaOH, KOH, or the like, but is not limited thereto.

The above production method can be carried out by an azide-alkyne ring addition reaction using a Cu (I) catalyst.

For example, the preparation method can be carried out according to the following reaction formula (1).

[Reaction Scheme 1]

In the above Reaction Scheme 1, R is an alkyl group having 1 to 20 carbon atoms having the same carbon number.

Preferably, R may be an alkyl group having 1 to 12 carbon atoms having the same carbon number. The alkyl group may be linear or branched.

The above Reaction Scheme 1 is characterized by the reaction of the triple bond of 2,6-diethynylnaphthalene with the azide period of Formula 3.

A third aspect of the present invention provides a ferroelectric liquid crystal material comprising the compound of the first aspect of the present invention.

The ferroelectric liquid crystal material may be such that the compound of Formula 2 is stacked in a columnar manner.

The ferroelectric liquid crystal material of the present invention can successfully perform both polarization and hydrogen bonding. The non-axial polarization is maintained at zero electric field and stabilized by the interaction of steric and hydrogen bonding action.

For a ferroelectric liquid crystal material comprising compound 2 of the present invention, the f _max of 1 Hz observed at 115 ^° C is the only known FCLC example (D. Miyajima et al ., Science 336 , 209-213 (2012)) It was 125 times faster than 0.008 Hz. This rapid polarization switching is due to the simple rotation of the triazolyl unit.

A fourth aspect of the present invention provides a storage element comprising a ferroelectric liquid crystal material according to the third aspect of the present invention.

The ferroelectric liquid crystal material of the present invention is suitable for a terra-class memory device because it can form a spontaneous polarization structure smaller than a smectic liquid crystal material having a conventional layer structure.

The ferroelectric liquid crystal material of the present invention is thermodynamically stable by the hydrogen bonding triazole network and the steric constraint that the axial polarization at the electric field of 0 is thermodynamically stable. Moreover, the simple switching mode based on the rotation of the triazolyl unit enables polarization switching 125 times faster than conventional simple FCLC.

The ferroelectric liquid crystal material of the present invention can provide an advanced design concept of nanostructured organic ferroelectrics in the field of sensor applications from nonvolatile memory devices. Specifically, the present invention can be applied to a memory device which is applicable to a terra-class high-density memory device and is nonvolatile and can be written and erased.

Figure 1 shows a ferroelectric column LC based on a 1,2,3-triazole unit. and a is a schematic diagram of a smectic and cylindrical liquid crystal (LC) having a remnant polarization. b is a schematic diagram of the dipole moment and the hydrogen bonding form of 1,2,3-triazole. c is the molecular structure and variable stereoscopic form of the designed liquid crystal compounds 1 and 2 (Cr: crystalline, COL: cylindrical, ISO: isotropic liquid phase)
Figure 2 shows a morphology analysis. a is the XRD profile at various temperatures, and the blue and red dots lines are reflections corresponding to the 2D hexagonal and spiral sequences, respectively. b is a GIXS image of 2 at 110 ^° C. c is a structural diagram of a C ₂ -symmetric column-type slice consisting of two cis-shaped molecules. d is the structure of the cis-helical structure, and the oxygen atom represented by the yellow sphere indicates the helical direction. e is the experimental (left) and simulation (right) 2D scattering image, for clarity, the alkyl perimeter omits c and d.
Fig. 3 is a schematic view of a hydrogen-bonded triazolyl network in a cis-spiral column model, b is a schematic diagram of a hydrogen-bonded triazolyl network in a trans-spiral column model, c Is the IR spectrum at various temperatures (Above: compound 1, below: compound 2).
4 is a polarization switching mode of the LC state, a is a POM image of a polarized sample, b is a PE loop measured at 1 Hz, c is a schematic diagram of polarization switching based on a simple rotation of a triazolyl group, It is the PE loop of LC-III at various frequencies.
Figure 5 is a crystal of Non-permanent remnant polarization in the LC state, a is directed to the pulse sequence in the PUND method, b is the extinction profile on the ferroelectric switching of the T _r increases LC, c is P at T _r = 7200 s _r Value and its P _sw and P _ns data.
Figure 6 relates to a pyrocurrent measurement, where a is the experimental condition of the supercurrent and control experiments and b is the supercurrent data as a function of time and temperature.
Figure 7 is a DSC thermogram of compounds 1 and 2, where a is the enthalpy change of each transition (KJ mol ^{- 1} ), and b is the POM image of compound 1 and compound 2 on LC.
In Figure 8, a is the XRD spectrum on the LC, the blue and red lines are reflections corresponding to the 2D hexagonal and spiral order, and b is the GIXS image of Compound 1 at 105 ° C.
9, a is a schematic diagram of a C ₁ -symmetric column-type slice with two trans type molecules. b is a schematic diagram of a trans-form helical structure, in which the oxygen atom shown as a yellow sphere indicates the helical direction.
10 is a PE loop of LC (1) and LC-II (2) at various frequencies.

Hereinafter, the present invention will be described in more detail with reference to Examples. These examples are for further illustrating the present invention, and the scope of the present invention is not limited to these examples.

<Material and Experimental Method>

Trimethylsilyl azide (Trimethylsilyl azide), Pyro gaelrol (pyrogallol), 2,6- dibromo-naphthalene, t - butyl nitrite, sodium L- ascorbyl bait (sodium L-ascorbate), and CuSO _{4 ·} 5H ₂ O Was purchased from Sigma-Aldrich Chemical. 1-bromohexane, 1-bromooctane and hydrazine monohydrate (at least 98%) were purchased from Tokyo Chemical Industry. Anhydrous MgSO ₄ (99% minimum), anhydrous potassium carbonate (99% minimum), and graphite powder were purchased from Duksan Chemical Industry Co., Nitric acid and silica gel were purchased from Samseon Pure Chemical Industries, Ltd.

N, N ' -dimethylformamide (DMF) was vacuum distilled and placed in a 4-Å molecular sieve flask. Tetrahydrofuran (THF), dichloromethane (DCM), and acetonitrile (ACN) were distilled with calcium hydroxide (CaH ₂ ) and placed in a 4-Å molecular sieve flask.

&Lt; Example 1 >

The intermediate compounds a and b were synthesized according to Reaction Scheme 2 below. Liquid crystal (LC) molecular compound 1 (R (CH ₂ ) ₅ CH ₃ ) and compound 2 (R (CH ₂ ) ₇ CH ₃ ) were synthesized by click chemistry.

[Reaction Scheme 2]

4,4 '- (naphthalene-2,6- diyl ) bis (2- methylbut -3- yn -2- be ) (Synthesis of compound a)

(1.0 g, 3.50 mmol), 2-methyl-3-butyn-2-ol (3.4 ml, 34.97 mmol), copper iodide (0.05 g, 0.26 mmol) and PdCl _{2 (PPh 3) 2 (0.08} g, 0.11 mmol) was dissolved in 30 mL of dry triethylamine (TEA). The reaction mixture was heated and refluxed at 100 ^° C for 8 hours under N ₂ atmosphere. After removing the TEA using a rotary evaporator, the mixture was extracted with deionized water and DCM. The DCM layer was washed several times with deionized water and then dried over anhydrous MgSO ₄ . After removing the DCM using a rotary evaporator, the mixture was purified by silica gel column chromatography ( n- hexane: ethyl acetate = 4: 1 solvent mixture, yellow solid, yield 0.95 g (92.9%) as eluent)

_{^{1 H-NMR (CDCl 3,}} δ, ppm): 7.89 (s, 2H, Ar- H), 7.70 (d, 2H, J = 8.4 Hz, Ar- H), 7.46 (d, 2H, J = 8.4 Hz , Ar- H ), 1.66 (s, 12H, -C H ₃ ).

2,6- 디 에티ynylnaphthalene (Compound b)

Compound a (0.95 g, 3.25 mmol) and sodium hydroxide (1.3 g, 32.49 mmol) were dissolved in 25 mL of toluene. The reaction mixture was heated and refluxed at 100 ^° C for 12 hours under N ₂ atmosphere. After removing the toluene using a rotary evaporator, the mixture was extracted with deionized water and DCM. The DCM layer was washed several times with deionized water and then dried over anhydrous MgSO ₄ . After removal of the DCM using a rotary evaporator, the resulting mixture was purified by silica gel column chromatography using n- hexane as eluent (yellowish white solid, yield 0.35 g (61.1%)).

_{^{1 H-NMR (CDCl 3,}} δ, ppm): 7.99 (s, 2H, Ar- H), 7.75 (d, 2H, J = 8.4 Hz, Ar- H), 7.54 (d, 2H, J = 8.6 Hz , Ar- H ), 3.18 (s, 2H, -C H ).

Synthesis of liquid crystal molecules (compounds 1 and 2)

Compounds 1 and 2 were synthesized by the same method. The synthesis for compound 2 is described representatively. 2,6-diethoxy-ethynyl-naphthalene (0.30 g, 1.70 mmol), 5-azido-1,2,3-tris (dodecyloxy) benzene (1.89 g, 3.75 mmol), copper sulfate -5 beard (CuSO ₄ -5H ₂ O) (0.42 g, 1.41 mmol) and (+) - sodium ascorbate (0.67 g, 3.41 mmol) were dissolved in 20 mL of dry THF and 2 mL of water. The reaction mixture was degassed three times with freeze-pump-thaw cycles. The mixture was stirred under N ₂ atmosphere for 12 hours at room temperature. After removing the THF using a rotary evaporator, the mixture was extracted with deionized water and DCM. The DCM layer was washed several times with deionized water and then dried over anhydrous MgSO ₄ . After removing the DCM using a rotary evaporator, the mixture was purified by silica gel column chromatography using DCM solvent as eluent (yellow solid, yield 1.3 g (64.5%))

_{^{1 H-NMR (CDCl 3,}} δ, ppm): 8.43 (s, 2H, Ar- H), 8.24 (s, 2H, triazole- H), 8.04-7.97 (m, 4H, Ar- H), 6.99 ( s, 4H, Ar- H), 4.09-4.00 (m, 12H, -OC H 2 CH 2 (CH 2) 5 CH 3), 1.88-1.78 (m, 12H, -OCH 2 C H 2 (CH 2) _{5 CH 3), 1.59-1.30 (m} , 60H, -OCH 2 CH 2 (C H 2) 5 CH 3), 0.91-0.88 (m, 18H, -OCH 2 CH 2 (CH 2) 5 C H 3) . ¹³ C-NMR (100 MHz, CDCl ₃ ,?, Ppm): 153.97,148.25,138.67,133.53,132.62,129.11,128.20,124.69,124.62,118.41,99.85,73.85,69.67,32.07,30.48,29.51,26.26, 22.83, 14.25. Anal. Calcd for C ₇₄ H ₁₁₄ N ₆ O ₆ : C, 75.08; H, 9.71; N, 7.10, found: C, 75.09; H, 9.71; N, 7.10. M _w / M _n = 1.01 (GPC).

Compound 1 was obtained in a yield of 0.8 g (55.6%) (yellow solid).

_{^{1 H-NMR (CDCl 3,}} δ, ppm): 8.43 (s, 2H, Ar- H), 8.24 (s, 2H, triazole- H), 8.04-7.98 (m, 4H, Ar- H), 6.99 ( s, 4H, Ar- H), 4.09-4.00 (m, 12H, -OC H 2 CH 2 (CH 2) 5 CH 3), 1.88-1.76 (m, 12H, -OCH 2 C H 2 (CH 2) _{5 CH 3), 1.53-1.35 (m} , 36H, -OCH 2 CH 2 (C H 2) 5 CH 3), 0.94-0.90 (m, 18H, -OCH 2 CH 2 (CH 2) 5 C H 3) . ¹³ C-NMR (100 MHz, CDCl ₃ ,?, Ppm): 153.96,148.24,138.63,133.51,138.61,129.10,128.18,124.67,124.60,118.41,99.81,73.83,69.65,31.80,30.41,29.40,25.88, 22.77, 14.24. Anal. Calcd for C ₆₂ H ₉₀ N ₆ O ₆ : C, 73.34; H, 8.93; N, 8.28, found: C, 73.32; H, 8.96; N, 8.36. M _w / M _n = 1.01 (GPC).

Experimental Example 1: ¹ H- and ¹³ C-NMR spectroscopy and chromatography

^{The 1} H- and ¹³ C-NMR spectra were recorded from the CDCl ₃ solution using a Bruker AM 400 spectrometer. The purity of the compound was checked by thin layer chromatography (TLC; Merck, silica gel 60).

Gel permeation chromatography (GPC) columns for Stragel HR 2,3 and using Shodex AT-8045 instrument equipped with Waters 401 1.0 mL min ^{- 1} at a flow rate of THF and N, N '- dimethylacetamide (99.9%) (40 : 1 volume ratio).

Experimental Example 2: Differential scanning calorimetry (DSC) experiment

Differential scanning calorimetry (DSC) experiments were performed at 10 ^° C min ^-1 using a Perkin Elmer DSC-7 equipped with a 1020 thermal analyzer.

As shown in FIG. 7A, the compounds exhibited an enantiotropic liquid crystal phase. In addition, a fan-like similar structure was observed with a polarizing optical microscope (POM), and it was found that the morphology unit in the liquid crystal phase was a one-dimensional (1D) column (see FIG.

Experimental Example 3: X-ray diffraction (XRD) measurement

X-ray diffraction (XRD) measurements were performed in a synchronous transmission mode at the Pahal Accelerator Laboratory (PAL) 9A beamline. The samples were stored in aluminum sample holders equipped with polyimide films on both sides.

의 q-간격비를 갖는 4개의 뚜렷한 반사를 나타내는데, 이로부터 시료 1 및 2는 육각형 원기둥 구조를 가짐을 알 수 있다(도 2a 및 도 8a 참조). 화학식 1의 화합물 및 화학식 2의 화합물의 기둥사이의 거리는 각각 30.5 및 32.8 Å로 평가되었다. 흥미롭게도, q=0.4, 1.0 및 1.3 Å^-1 근처에서 상대적으로 넓은 반사가 잘 나타나는데, 이로부터 기둥 내 나선형 순서가 존재함을 알 수 있다.X-ray diffraction (XRD) data using bulk samples 1 and 2

The q - 4 to represent a distinct reflection with a distance ratio, from which the samples 1 and 2 it can be seen having a hexagonal columnar structure (see Fig. 2a and Fig. 8a). The distances between the pillars of the compound of formula (1) and the compound of formula (2) were evaluated to be 30.5 and 32.8 Å, respectively. Interestingly, relatively large reflections appear well around q = 0.4, 1.0 and 1.3 Å ^-1 , indicating that there is a spiral sequence in the column.

Also, in XRD data, reflections from the X-axis corresponding to wide reflection appeared. Of these, two diagonal spots near q = 0.44 Å ^-1 are evidence of a helical order in the column. The angle (α) between the meridian and the diagonal points is about 40 ^° . From the d-spacing and a, The average spiral period ( h ) can be calculated as 19.0 Å for 1 and 2. q Considering the position of the reflection off the X axis along the _z -axis, the helical period can be divided into four layers. The d - spacing (4.77 Å) of the meridian reflections at L = 4 can be regarded as the mean stacking distance between the naphthalene cores along the cylinder axis.

Based on the XRD data and the molecular volume, the number of molecules ( N ) in the column-type slice can be calculated to be two, 1 and 2 (see FIG. 2C). Bond rotation between a triazolyl group and a naphthalenyl group may allow for a cis isomer or a trans isomer. Here, it can be seen that the isomer is organized into a cylindrical structure.

To this end, two possible spiral models matching the four-layer X-ray data may be proposed. In the case of the cis-column model with a C ₂ -symmetric column slice (FIG. 2c), the mutual rotation angle between adjacent column slices is 45 ^° (FIG. 2d) and the angle between C ₁ -symmetric column slices is 90 ° ^o (see Fig. 9).

Simulations of the α values using Helix software showed that the simulation values for the sheath and trans-helical models were 40 and 23 ^°, respectively (FIG. 2e). The sheath model angle is almost identical to the experimentally observed angle (40 ^° ) from the GIXS data, from which it can be seen that the cis-isomer forms a spiral column.

Hydrogen bonding between amide bonds can lead to spiral column LC structures. Considering the similarity in size and shape, it can be seen that the triazolyl unit can form a hydrogen bonding network in the column.

The present inventors have studied the optimal hydrogen bonding distance between triazolyl CH and nitrogen atoms for the cis and trans helical models, and found that the hydrogen bonding distances of the cis and trans types are 1.83 and 2.53 A, respectively (Figures 3A and B) . This is evidence supporting the cis-helical model.

<Experimental Example 4> Morphology analysis

For the morphology analysis of the compounds, a tilt angle incident scattering (GIXS) experiment was carried out using oriented film samples (see Figures 2b and 8b). (GIXS) experiments were performed on the PAL 9A beamline. For GIXS experiments, surface alignment samples were prepared by spin casting a sample solution (dissolved in THF, ~3 wt%) on a Si wafer functionalized with 3-aminopropyltriethoxysilane (APS).

As a result, the GIXS image of Compound 1 and Compound 2 at 100 ° C shows a 2D hexagonal reflection in the equator, from which it can be seen that the column is standing on the substrate.

Experimental Example 5: Spiral column formation by hydrogen-bonded triazolyl network

The temperature-variable IR spectra were obtained using a Perkin Elmer Spectrum 100 FT-IR spectrometer combined with a homemade heating stage. Samples were placed between KBr plates.

The hydrogen bonding action between 1,2,3-triazolyl units was confirmed using a temperature variable infrared (IR) spectrometer. Both free and hydrogen bonded triazolyl CH signals coexist on the LC, consistent with a cis-helical packing model using either an H-donor (CH) or H-acceptor (nitrogen) to participate in the hydrogen bonding network Appear at 3140 and 3115 cm ^-1 , respectively (Figure 3c). The hydrogen bonding CH signal for Compound 1 and Compound 2 weakened with increasing temperature.

On the other hand, especially in the case of compound 2, the free triazolyl C-H signal showed different temperature dependency.

The LC phase of compound 2 can be classified into three temperature ranges in terms of the free CH signal. At LC-I (63 ^o C to 93 ^o C) with the strongest hydrogen bond, the free CH signal was the broadest. This suggests a broad distribution of the isomeric state of the triazolyl unit. On the other hand, in LC-II with intermediate hydrogen bonds (93 ^° C to 109 ^° C), the free CH signal was the narrowest. From this, it can be seen that the isomeric state of the triazolyl group is uniform although the hydrogen bonding network is loosened due to the steric constraint due to dense packing of the bulked drones.

At LC-III (109 ^o C to 119 ^o C) with the weakest hydrogen bond, the free CH signal is somewhat wider than LC-II, but narrower than LC-I. From this it can be seen that the steric constraints still limit the isomeric behavior of the triazolyl units to some extent.

As a result, the three kinetic behavior of the triazolyl group is present with the temperature on the LC of compound 2.

On the other hand, the LC phase of Compound 1 exhibits a simple IR pattern over the entire temperature range in that a broad free C-H signal is observed with a hydrogen-bonded C-H signal.

Experimental Example 6: Analysis of Polarization Switching Phase on LC

Prior to the switching experiments, LC samples (ITO cell thickness: 5 m) were polarized by cooling to LC phase in liquid phase under a DC electric field (20 Vm ^-1 ).

As suggested by structural analysis and spectroscopic analysis, LC phases composed of cis isomers can be switched by an alternating current (AC) electric field.

As confirmed by the POM, the polarization region was completely dark, indicating that the column was aligned vertically to the substrate (FIG. 4A).

It was investigated polarization switched by the Sawyer-Tower measurement method using ^{- [1 0.5 ~ 5.0 Hz,} 28 V peak-to-peak (V pp) m] triangular wave voltage.

The LC-I of compound 2 represents a phase-dielectric polarization electric field ( PE ) loop while the other LC phases of compound 1 and compound 2 exhibit a ferroelectric pattern with non-P _r values (40-400 nC cm ^-2 ) ).

In the PE loop, the convex region indicates the lossy characteristic of the sample. The P _r value at 1 Hz increases in the following order: LC-III ( 2 )> LC-II ( 2 )> LC ( 1 )

This order is the reverse of the order of hydrogen bond strength. This suggests that the hydrogen bonding action retarded polarization switching through rotation of the triazolyl group (Fig. 4C).

FIG. 4D shows the switching effect of the spontaneous polarization according to the frequency of the alternating electric field. It can be seen that spontaneous polarization is still present in the zero voltage electric field, and the remanent polarization is saturated at 1 Hertz. That is, it is shown that the polarization direction can be reversed within one second. This shows that the columnar liquid crystal of the present invention exhibits ferroelectric properties.

In addition, the maximum driving frequency (fmax) saturating the P _r value is measured only in the LC-III with the weakest hydrogen bond (see Figs. 4D and 10).

Experimental Example 7: Determination of non-linear residual polarization in LC state

The PUND measurement was performed using a Keithley 2410 source meter combining a heating oven (controlled temperature range: 25-200 ^o C).

To meet the ferroelectric criterion, the switching polarization must be stable at zero electric field. In order to avoid the confusion caused by the ferroelectricity LC exhibiting ferroelectric behavior for a short period of time, the extinction profile P _r for the diastole (T _r ) was investigated using a positive up negative (PUND) method consisting of a pulse sequence. [pulse width (pw) = 31 s, 20 V m ^-1 ] (see Fig. 5A).

P _r [= (P _sw -P _ns ) / 2] can be determined from the switching polarization (P _sw ) and the non-switching polarization (P _ns ). In the case of a ferroelectric switching LC, the polarization ratio [P _r (T _r ) / P _r (initial)] disappears in the initial stage and finally approaches 14-20% of the initial P _r (FIG.

In addition, a sufficiently long diastolic _{(T r = 7200 s, pw} = 45 s) of the P _r values for each of the LC (1), LC-II (2), and LC-III (2) 153.6, 654.1 and 430.6 from nC cm & lt ^; &quot; ² &gt; (Fig. 5C). In Fig. 5c, the difference between the switching polarization Psw and the non-switching polarization Pns is still shown at 7200 seconds. That is, it can be seen that the switching polarization is greater than the non-switching polarization, and thus the remanent polarization is thermodynamically stable. These results show that the cylindrical liquid crystal of the present invention exhibits ferroelectric properties.

&Lt; Experimental Example 8 >: Pyrocurrent measurement [

For electrical measurements, indium tin oxide (ITO) coated glass oxidation cell (thickness: 5 ㎛, the area: 1 cm ^{- 2)} was purchased from Linkam Scientific Instruments Company. A second current measurement was performed using a Keithley 2410 source meter combined with a heating oven (controlled temperature range 25-200 ^o C).

Claims (8)

A triazole-based compound represented by the following formula (1) or (2)
[Chemical Formula 1]

(2)

In the formulas (1) and (2), R ₁ to R ₆ are alkyl groups having 1 to 20 carbon atoms having the same carbon number. The method according to claim 1,
In the above formulas (1) and (2), R ₁ to R ₆ are (CH ₂ ) ₅ CH ₃ or (CH ₂ ) ₇ CH ₃ . Synthesizing 2,6-diethynylnaphthalene; And
Reacting the 2,6-diethynylnaphthalene with a compound represented by the following formula (3): &lt; EMI ID =
(3)

In Formula 3, R is an alkyl group having 1 to 20 carbon atoms having the same carbon number. The method of claim 3,
As the 2,6-diethynylnaphthalene,
2-methyl-3-butyn-2-ol is reacted with 2,6-dibromonaphthalene to give 4,4 '- (naphthalene- Lt; / RTI &gt; And the 4,4 '- (naphthalene-2,6-diyl) bis (2-methylbut-3-yn-2-ol) with a basic substance. The method of claim 3,
Wherein the triple bond of the 2,6-diethynylnaphthalene is reacted with the azide group of the formula (3). A ferroelectric liquid crystal material comprising the compound of claim 1. The method according to claim 6,
Wherein the ferroelectric liquid crystal material is a ferroelectric liquid crystal material having a compound represented by the following formula (2)
(2)

In Formula 2, R ₁ to R ₆ are alkyl groups having 1 to 20 carbon atoms having the same carbon number. A storage element comprising the ferroelectric liquid crystal material of claim 6 or 7.

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