Compound, liquid crystal composition and display device
阅读说明：本技术 化合物、液晶组合物以及显示装置 (Compound, liquid crystal composition and display device ) 是由 贾刚刚 于 2021-07-16 设计创作，主要内容包括：本申请涉及液晶领域,公开一种化合物、液晶组合物及显示装置。该化合物具有式(I)的结构：式(I)。该化合物可作为一种新型的液晶化合物,使用该化合物的液晶组合物具有较好的显示效果。(The application relates to the field of liquid crystal, and discloses a compound, a liquid crystal composition and a display device. The compound has the structure of formula (I): formula (I). The compound can be used as a novel liquid crystal compound, and a liquid crystal composition using the compound has a good display effect.)
1. A compound having the structure of formula (I):
wherein R is2In the presence or absence of R2When present, R1、R2Each independently selected from hydrogen, fluorine, chlorine, C1-C15 alkyl, C1-C15 alkoxy, C3-C15 cycloalkyl, C2-C15 alkenyl, C2-C15 alkenyloxy, C2-C15 alkynyl, ether group, thioether group, ester group, cyano group, cyanato group, thiocyano group or isothiocyanato group;
Z1、Z2each independently present or absent; z1、Z2Each independently of the other, Z1、Z2Each independently selected from linear C1-C5 alkyl, linear C2-C5 alkenyl, linear C2-C5 alkynyl, ester group and ether group;
the hydrogen in the C1-C15 alkyl, C1-C15 alkoxy, C3-C15 cycloalkyl, C2-C15 alkenyl, C2-C15 alkenyloxy, C2-C15 alkynyl, ether, thioether, ester, cyano, cyanato, thiocyano, isothiocyanato, straight-chain C1-C5 alkyl, straight-chain C2-C5 alkenyl and straight-chain C2-C5 alkynyl is unsubstituted, or part or all of the hydrogen is substituted by at least one of fluorine and chlorine;
m is selected from 0, 1 or 2;
L0、L1、L2each independently represents a hydrogen atom, a fluorine atom or a methyl group.
2. The compound of claim 1, wherein L is0And said L1At the same time being F, L2Is hydrogen or methyl; or said L0And said L2At the same time being F, L2Is hydrogen or methyl.
3. The compound of claim 1, wherein Z is1Z to2Each independently selected from-CH2-、-CH2-CH2-、-(CH2)3-、-(CH2)4-、-CH＝CH-、-C≡C-、-COO-、-OOC-、-CF2O-、-OCH2-、-CH2O-、-OCF2-、-CF2-CH2-、-CH2-CF2-、-C2F4-or-CF ═ CF.
4. The compound of claim 1, wherein the compound of formula (I) is selected from the group consisting of:
5. a liquid crystal composition comprising 0.5 to 50% by weight of a compound of formula (I) as claimed in any one of claims 1 to 4.
6. The liquid crystal composition of claim 5, further comprising 30% to 99% by weight of a compound represented by formula (II):
wherein R is3And R4Each independently selected from hydrogen, halogen, C1-C15 alkyl, C1-C15 alkoxy, C2-C15 alkenyl, C2-C15 alkynyl, ether group, ester group or cyano; hydrogen in the C1-C15 alkyl, C1-C15 alkoxy, C2-C15 alkenyl, C2-C15 alkynyl, ether group, ester group and cyano is unsubstituted, or partial hydrogen or all hydrogen is replaced by at least one of fluorine and chlorine;
Z3selected from an alkylene bridge, an alkyleneoxy bridge, an alkenylene bridge, an alkynyl bridge, an ester bridge, or an alkyleneoxy bridge; wherein hydrogen on the alkylene bridge, alkyleneoxy bridge, alkenylene bridge, alkynyl bridge, ester bridge or alkyleneoxy bridge is unsubstituted or part or all of the hydrogen is substituted by at least one of fluorine and chlorine;
each independently selected from the group consisting of alicyclic, aryl or heteroaryl, wherein the hydrogens on the alicyclic, aryl or heteroaryl groups are unsubstituted, or some or all of the hydrogens are replaced with fluorine;
p and q are each independently selected from 0, 1 or 2.
7. The liquid crystal composition of claim 5, further comprising 0.01 to 1% by weight of at least one of a chiral dopant and 0.01 to 20% of a polymeric monomer director.
8. A display device comprising the liquid crystal composition according to any one of claims 5 to 7.
Technical Field
The invention relates to the field of liquid crystal display, in particular to a compound, a liquid crystal composition and a display device.
Background
Depending on the display mode, the liquid crystal display device is classified into the following modes: twisted Nematic (TN) mode, Super Twisted Nematic (STN) mode, in-plane mode (IPS), Vertical Alignment (VA) mode. The liquid crystal composition is required to have the following characteristics regardless of the display mode: chemical property, stable physical property, low viscosity, proper delta epsilon and resolution ratio delta n, and good compatibility with other liquid crystal compounds. The application discloses a compound, a liquid crystal composition and a display device, wherein the compound is simple and convenient in synthesis method and easy to produce, can be used as a novel liquid crystal compound, and the liquid crystal composition using the compound has a good display effect.
Disclosure of Invention
The application discloses a compound, a liquid crystal composition and a display device, wherein the compound can be used as a novel liquid crystal compound, and the liquid crystal composition using the compound has a good display effect.
In order to achieve the purpose, the application provides the following technical scheme:
a compound having the structure of formula (I):
wherein R is2In the presence or absence of R2When present, R1、R2Each independently selected from hydrogen, fluorine, chlorine, C1-C15 alkyl, C1-C15 alkoxy, C3-C15 cycloalkyl, C2-C15 alkenyl, C2-C15 alkenyloxy, C2-C15 alkynyl, ether group, thioether group, ester group, cyano group, cyanato group, thiocyano group or isothiocyano group;
Z1、Z2each independently present or absent; z1、Z2Each independently of the other, Z1、Z2Each independently selected from linear C1-C5 alkyl, linear C2-C5 alkenyl, linear C2-C5 alkynyl, ester group and ether group;
the hydrogen in the C1-C15 alkyl, C1-C15 alkoxy, C3-C15 cycloalkyl, C2-C15 alkenyl, C2-C15 alkenyloxy, C2-C15 alkynyl, ether, thioether, ester, cyano, cyanato, thiocyano, isothiocyano, straight-chain C1-C5 alkyl, straight-chain C2-C5 alkenyl and straight-chain C2-C5 alkynyl is unsubstituted, or part or all of the hydrogen is replaced by at least one of fluorine and chlorine;
m independently represents 0, 1 or 2;
L0、L1、L2each independently represents a hydrogen atom, a fluorine atom or a methyl group. Said L0And said L1Simultaneously F and L2Is hydrogen or methyl; or said L0And said L2At the same time being F, L2Is hydrogen or methyl.
Further, Z is1、Z2Each independently selected from-CH2-、-CH2-CH2-、-(CH2)3-、-(CH2)4-、 -CH＝CH-、-C≡C-、-COO-、-OOC-、-CF2O-、-OCH2-、-CH2O-、-OCF2-、-CF2-CH2-、 -CH2-CF2-、-C2F4-or-CF ═ CF; preferably a single bond, -CF2O-or-CF2CF2-。
Further, the compound represented by the formula (I) is selected from:
a liquid crystal composition comprising from 0.5% to 50% by weight of a compound as described herein.
Further, the liquid crystal composition also comprises 30-99% by weight of a compound shown as a formula (II):
wherein R is3And R4Each independently selected from hydrogen, halogen, C1-C15 alkyl, C1-C15 alkoxy, C2-C15 alkenyl, C2-C15 alkynyl, ether group, ester group or cyano; hydrogen in the C1-C15 alkyl, C1-C15 alkoxy, C2-C15 alkenyl, C2-C15 alkynyl, ether group, ester group and cyano is unsubstituted, or partial hydrogen or all hydrogen is replaced by at least one of fluorine and chlorine;
Z3selected from an alkylene bridge, an alkyleneoxy bridge, an alkenylene bridge, an alkynyl bridge, an ester bridge, or an alkyleneoxy bridge; wherein hydrogen on the alkylene bridge, alkyleneoxy bridge, alkenylene bridge, alkynyl bridge, ester bridge or alkyleneoxy bridge is unsubstituted or part or all of the hydrogen is substituted by at least one of fluorine and chlorine;
each independently selected from the group consisting of alicyclic, aryl or heteroaryl, wherein the hydrogens on the alicyclic, aryl or heteroaryl groups are unsubstituted, or some or all of the hydrogens are replaced with fluorine;
p and q are each independently selected from 0, 1 or 2.
Further, the liquid crystal composition also comprises 0.01-1% of chiral dopant and 0.01-20% of at least one of polymer monomer orientation agent.
A display device comprising a liquid crystal composition as in the present application.
By adopting the technical scheme of the application, the beneficial effects are as follows:
the compound shown in the formula (I) is a novel liquid crystal compound, comprises the compound shown in the formula (I), can be a positive liquid crystal composition, can also be a negative liquid crystal composition, has a wide liquid crystal phase temperature range, a high clearing point and low viscosity, has a proper refractive index anisotropy constant, can improve the performance of a liquid crystal composition material and a display, and has an important significance for realizing quick response of the display. Meanwhile, the compound also has the advantages of simple preparation steps and low cost.
Detailed Description
The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the embodiments of the present application, and it is obvious that the described embodiments are only a part of the embodiments of the present application, and not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present application.
It should be noted that: in the present application, all embodiments and preferred methods mentioned herein can be combined with each other to form new solutions, if not specifically stated. In the present application, all the technical features mentioned herein as well as preferred features may be combined with each other to form new technical solutions, if not specifically stated. In the present application, percentages (%) or parts refer to percentages by weight or parts by weight relative to the composition, unless otherwise specified. In the present application, the components referred to or the preferred components thereof may be combined with each other to form new embodiments, if not specifically stated. In this application, unless otherwise stated, the numerical range "a-b" represents a shorthand representation of any combination of real numbers between a and b, where a and b are both real numbers. For example, a numerical range of "6 to 22" means that all real numbers between "6 to 22" have been listed herein, and "6 to 22" is simply a shorthand representation of the combination of these values. The "range" disclosed herein may be in the form of one or more lower limits and one or more upper limits, respectively, in the form of lower limits and upper limits. In the present application, unless otherwise indicated, the individual reactions or process steps may be performed in sequence, or may be performed in sequence. Preferably, the reaction processes herein are carried out sequentially.
Unless otherwise defined, technical and scientific terms used herein have the same meaning as is familiar to those skilled in the art. Moreover, any methods or materials similar or equivalent to those described herein can also be used in the present application.
In a first aspect, the present application provides a compound having the structure of formula (I):
wherein R is2In the presence or absence of R2When present, R1、R2Each independently selected from hydrogen, fluorine, chlorine, C1EC15 alkyl, C1-C15 alkoxy, C3-C15 cycloalkyl, C2-C15 alkenyl, C2-C15 alkenyloxy, C2-C15 alkynyl, ether, thioether, ester, cyano, cyanato, thiocyano or isothiocyano;
Z1、Z2each independently present or absent; z1、Z2Each independently of the other, Z1、Z2Each independently selected from linear C1-C5 alkyl, linear C2-C5 alkenyl, linear C2-C5 alkynyl, ester group and ether group;
the hydrogen in the C1-C15 alkyl, C1-C15 alkoxy, C3-C15 cycloalkyl, C2-C15 alkenyl, C2-C15 alkenyloxy, C2-C15 alkynyl, ether, thioether, ester, cyano, cyanato, thiocyano, isothiocyano, straight-chain C1-C5 alkyl, straight-chain C2-C5 alkenyl and straight-chain C2-C5 alkynyl is unsubstituted, or part or all of the hydrogen is replaced by at least one of fluorine and chlorine;
m independently represents 0, 1 or 2;
L0、L1、L2each independently represents a hydrogen atom, a fluorine atom or a methyl group. Wherein, L is0And said L1At the same time being F, L2Is hydrogen or methyl; or said L0And said L2At the same time being F, L2Is hydrogen or methyl.
The compound shown in the formula (I) is a novel liquid crystal compound, comprises the compound shown in the formula (I), can be a positive liquid crystal composition, can also be a negative liquid crystal composition, has a wide liquid crystal phase temperature range, a high clearing point and low viscosity, has a proper refractive index anisotropy constant, can improve the performance of a liquid crystal composition material and a display, and has an important significance for realizing quick response of the display.
Wherein Z is1、Z2Each independently present or absent as a bridge. When Z is1、Z2When each independently is present, Z1、Z2Independently selected from linear C1-C5 alkyl, linear C2-C5 alkenyl, linear C2-C5 alkynyl, ester group and ether group. At this time, Z1、Z2Each independently selected from an alkylene bridge, an alkyleneoxy bridge, an alkenylene bridge, an alkynyl bridge, an ester bridge, or an alkyleneoxy bridge; wherein hydrogen on the alkylene bridge, alkyleneoxy bridge, alkenylene bridge, alkynyl bridge, ester bridge or alkyleneoxy bridge is unsubstituted or part or all of hydrogen is substituted by at least one of fluorine and chlorine.
In one embodiment of the present application, Z is1、Z2Each independently selected from-CH2-、-CH2-CH2-、 -(CH2)3-、-(CH2)4-、-CH＝CH-、-C≡C-、-COO-、-OOC-、-CF2O-、-OCH2-、-CH2O-、 -OCF2-、-CF2-CH2-、-CH2-CF2-、-C2F4-or-CF ═ CF; preferably a single bond, -CF2O-or-CF2CF2-。
The compound of formula (I) is selected from:
in a second aspect, the present application provides a liquid crystal composition comprising from 0.5% to 50% by weight of a compound of formula (I) as described herein.
The liquid crystal composition has the advantages of wide temperature range of liquid crystal phase, high clearing point, low viscosity and proper refractive index anisotropy constant, can improve the performance of liquid crystal composition materials and displays, and has important significance for realizing quick response of the displays.
In the examples of the present application, the mass ratio of the compound represented by the formula (I) in the liquid crystal composition may be, for example, 0.5%, 1%, 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, or 50%.
In one embodiment of the present application, the liquid crystal composition further comprises 30% to 99% by weight of a compound represented by formula (II):
wherein R is3And R4Each independently selected from hydrogen, halogen, C1-C15 alkyl, C1-C15 alkoxy, C2-C15 alkenyl, C2-C15 alkynyl, ether group, ester group or cyano; hydrogen in the C1-C15 alkyl, C1-C15 alkoxy, C2-C15 alkenyl, C2-C15 alkynyl, ether group, ester group and cyano is unsubstituted, or partial hydrogen or all hydrogen is replaced by at least one of fluorine and chlorine;
Z3selected from an alkylene bridge, an alkyleneoxy bridge, an alkenylene bridge, an alkynyl bridge, an ester bridge, or an alkyleneoxy bridge; wherein hydrogen on the alkylene bridge, alkyleneoxy bridge, alkenylene bridge, alkynyl bridge, ester bridge or alkyleneoxy bridge is unsubstituted or part or all of the hydrogen is substituted by at least one of fluorine and chlorine;
each independently selected from the group consisting of alicyclic, aryl or heteroaryl, wherein the hydrogens on the alicyclic, aryl or heteroaryl groups are unsubstituted, or some or all of the hydrogens are replaced with fluorine;
p and q are each independently selected from 0, 1 or 2.
In the examples of the present application, the mass ratio of the compound represented by the formula (II) in the liquid crystal composition may be, for example, 0.5%, 1%, 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, or 50%.
In one embodiment of the present application,each independently selected from:
in one embodiment of the present application, the liquid crystal composition further comprises at least one of a chiral dopant in an amount of 0.01 to 1% by weight and a polymer monomer alignment agent in an amount of 0.01 to 20% by weight.
Among them, the chiral dopant may be, for example:
the polymeric monomer director (for alignment) may be, for example:
the preparation method of the liquid crystal composition of the present application includes, but is not limited to, the following: (1) heating, mixing and stirring various monomer liquid crystal compounds uniformly, and filtering to obtain a liquid crystal material; (2) dissolving various monomer liquid crystal compounds by using a solvent, uniformly mixing, and then extracting the solvent under a vacuum condition to obtain a liquid crystal material; (3) various monomer liquid crystal compounds are uniformly mixed by using oscillation mixing or ultrasonic mixing and the like, and then the liquid crystal material is obtained by filtering. The proportion of each monomer liquid crystal material is prepared according to the specific display performance requirement. The mixed liquid crystal material can be prepared by the method.
In a third aspect, the present application provides a display device comprising a liquid crystal composition as in the present application.
The display device may be a liquid crystal display device or an electro-optical display device, and specifically, a device used for display such as a TN type display, a VA type display, an IPS type display, or a blue phase display.
The display device comprises a liquid crystal display panel, wherein the liquid crystal display panel comprises a first substrate and a second substrate which are arranged in a manner of opposite to each other, and a liquid crystal layer filled between the first substrate and the second substrate, and the liquid crystal layer contains the liquid crystal composition.
Examples of the synthetic methods of specific compounds
Synthesis method-Synthesis example propyl group is exemplified
Synthesis of intermediate I
Adding 80g of n-butyl aldehyde, 300ml of cyclohexane, 136g of pentaerythritol and 10ml of 0.1mol/l of dilute hydrochloric acid into a three-necked flask, stirring for 5-6h at 50 ℃, washing with water for neutralization, removing the solvent from the organic phase by rotation, and recrystallizing with petroleum ether and ethanol to obtain the compound I.
1100 g of compound and 90g of p-bromobenzaldehyde are added into a three-necked bottle, 500ml of toluene and 5g of p-toluenesulfonic acid are added, reflux dehydration reaction is carried out for 5-6h, after the reaction solution is washed once, the organic phase passes through a silica gel column, concentration and ethanol petroleum ether recrystallization are carried out, and an intermediate I is obtained.
Example 1
Compound S11:
the synthetic route of the compound is as follows:
preparing a Grignard reagent from 356g of the intermediate I and 24g of magnesium metal in THF, cooling to-20-30 ℃, introducing carbon dioxide into the reaction system, keeping the environment for 1h when the reaction system does not absorb the carbon dioxide any more, and slowly heating to room temperature. Slowly pouring dilute hydrochloric acid for acidolysis under ice bath condition, extracting organic phase with ethyl acetate, concentrating reaction solution to obtain solid, adding petroleum ether, pulping, and filtering to obtain intermediate acid.
Adding 33g of intermediate acid, 0.15mol of propanedithiol, 0.15mol of trifluoromethanesulfonic acid and 100ml of methyl tert-butyl ether, carrying out reflux dehydration reaction for 6h, cooling, filtering to obtain a solid, dissolving the solid with THF, adding into a three-neck flask, adding 15g of 3,4, 5-trifluorophenol, reacting at 60 ℃ for 1h, dropwise adding 50g of triethylamine hydrofluoride and 50g of bromine, continuing controlling the temperature to react for 1h, heating to room temperature, hydrolyzing, concentrating, pulping with 500ml of petroleum ether to extract a product, filtering with diatomite, concentrating to obtain a crude product, and carrying out column chromatography to obtain the target compound.
Analysis and test: 1H NMR (400MHz, Chloroform-d) Δ: 7.42(q, 4H), 6.81 (m, 2H), 5.86(s, 1H), 4.77(t, 1H), 3.65(m, 8H),1.60(q, 2H),1.31 (m, 2H), 0.89(t, 3H).
Mass spectral data m/z: m+474。
Example 2
Compound S12:
the synthetic route of the compound is as follows:
stirring 136g of intermediate, 16g of 3, 5-difluorophenylboronic acid, 80ml of toluene, 60ml of ethanol and 50ml of water, carrying out reflux reaction for 6 hours, filtering, extracting filter residues from the toluene, combining organic phases, neutralizing and concentrating to obtain a crude product, and recrystallizing with ethanol and toluene to obtain a coupling product;
taking 40g of the coupling product, dissolving the coupling product by using THF, then cooling to-60-70 ℃, dropwise adding 0.12mol of n-BuLi solution, reacting for 1h at a controlled temperature, dropwise adding 25g of dibromodifluoromethane, reacting for 1h at a controlled temperature, heating to room temperature, carrying out acidolysis, extracting an organic phase by using toluene, neutralizing, and carrying out spin drying to obtain an intermediate compound;
taking DMF as a solvent for 50g of the intermediate compound, adding 20g of sodium carbonate, 15g of 3,4, 5-trifluorophenol and 10g of water, carrying out reflux reaction for 12h, extracting the reaction solution with toluene, neutralizing, spin-drying, and recrystallizing with ethanol toluene to obtain the product compound.
Compound assay test: 1H NMR (400MHz, Chloroform-d) Δ: 7.39(m, 6H), 6.82(q, 2H), 5.92(s, 1H), 4.71(t, 1H),3.60(q, 8H),1.60(q, 2H),1.30 (m, 2H), 0.90(t, 3H).
Mass spectral data m/z: m+586。
Example 3
Compound S13:
the synthetic route of the compound is as follows:
136g of intermediate, 20g of 2, 3-difluoro, 4-propoxyphenylboronic acid, 80ml of toluene, 60ml of ethanol and 50ml of water are stirred, refluxed and reacted for 6 hours, filtered, filter residue is extracted from the toluene, organic phases are combined, neutralized and concentrated to obtain a crude product, and the crude product is recrystallized by using ethanol and toluene to obtain the compound.
Compound assay test: 1H NMR (400MHz, Chloroform-d) Δ: 7.08(q, 1H), 6.52(q, 1H), 5.88(s, 1H), 4.70(t, 1H), 4.01(t, 2H), 3.66(q, 8H), 1.63(m, 4H), 1.30(m, 2H), 0.89(t, 6H).
Mass spectral data m/z: m+372。
The preparation of the above compounds is merely illustrative, and other compounds referred to herein can be performed by reference to the preparation of the compounds provided in examples 1-3. During the preparation process, the raw materials can be replaced correspondingly according to the target product.
Example 4
This example is a liquid crystal composition whose composition of the compound monomers is shown in table 1.
TABLE 1
Example 5
This example is a liquid crystal composition whose composition of the compound monomers is shown in Table 2.
TABLE 2
Comparative example 1
This example is a liquid crystal composition whose composition of compound monomers is shown in Table 3.
TABLE 3
The liquid crystal compositions of examples 4 to 5 and comparative example 1 were respectively tested for the clearing point Cp, the optical anisotropy Δ n, and the dielectric anisotropy Δ Σ, and the test results are shown in table 4.
The optical anisotropy test method comprises the following steps: the measurement was carried out at 25 ℃ and 589nm wavelength using an Abbe refractometer. The surface of the main prism is rubbed in the same direction, and the sample is dropped onto the main prism after rubbing. Refractive index n11Measuring when the polarization direction is parallel to the rubbing direction; refractive index n⊥Measuring when the polarization direction is vertical to the rubbing direction; the optical anisotropy Δ n is represented by the formula Δ n ═ n11-n⊥And calculating.
The dielectric anisotropy was measured as follows: the measurements were carried out using a Hewlett packard model HP4284 a. The dielectric constant Σ of the liquid crystal molecules in the axial direction was measured at 25 ℃11And dielectric constant Sigma in the direction of the short axis of the liquid crystal molecules⊥Dielectric anisotropy is determined by the formula Δ ∑ ═∑11-∑⊥And (6) calculating.
TABLE 4
Serial number
Clearing Point/. deg.C
Optical anisotropy
Anisotropy of dielectric constant
Example 4
92
0.12
6.7
Example 5
90
0.11
-5.0
Comparative example 1
86
0.113
6.5
From the data in table 4, example 4 obtained a significant increase in liquid crystal phase transition temperature and optical anisotropy using the compound monomer defined in the present application, relative to comparative example 1, which is probably due to the high content of oxygen atoms, which can increase the electron cloud density relative to C atoms, resulting in the above results. In addition, the compound has the characteristics of simple synthesis process and easily obtained raw materials.
As can be seen from the data of example 4 and example 5 in table 4, the liquid crystal composition prepared by using the compounds of the present application can obtain a positive liquid crystal composition and also can obtain a negative liquid crystal composition by adjusting the mixture ratio of the compounds, the obtained liquid crystal composition has a high clearing point which can reach more than 80, and the optical anisotropy and the dielectric constant anisotropy can both meet the display requirements of a liquid crystal display panel, thereby providing a new selectable compound for the development of a VA-mode display.
It will be apparent to those skilled in the art that various changes and modifications may be made in the embodiments of the present application without departing from the spirit and scope of the application. Thus, if such modifications and variations of the present application fall within the scope of the claims of the present application and their equivalents, the present application is intended to include such modifications and variations as well.