A flexible electric response liquid crystal polymer material and a preparation method and application thereof

Abstract

The application discloses a novel flexible electric response liquid crystal polymer material and a preparation method thereof, and the novel material has the capability of reversible response to an electric field at room temperature. Existing electric response liquid crystal polymer materials often have a high glass transition temperature and need to be in a high-temperature environment to produce response to an electric field. In the application, the novel flexible electric response liquid crystal polymer material is generated by the reaction of a mono-acrylate monomer, a di-acrylate monomer and a chain transfer agent, has a glass transition temperature lower than room temperature, can produce reversible response to an electric field at room temperature, and has wide application prospects. The novel material can be used in many fields such as self-cleaning surfaces and touch displays in the future.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of electric responsive material, in particular to a flexible electric responsive liquid crystal polymer material and a preparation method and application thereof. BACKGROUND

[0002] Currently, the research on responsive liquid crystal polymer materials mainly focuses on thermal and light stimulation response. Although some research has successfully demonstrated the application prospect of such materials, it is still unrealistic to use such photo-thermal driven materials in daily life. In contrast, electric driving shows excellent controllability. Some research shows that part of the liquid crystal polymer network does have the ability to change its own morphology in response to electricity. Generally, when there are polar groups such as cyano groups in liquid crystal molecules, the molecules will exhibit a strong dipole moment and will exhibit the ability to respond to electricity. When such molecules are exposed to an electric field, the molecules will rotate and arrange along the direction of the electric field lines, and when such molecules are part of a liquid crystal polymer network, the macroscopic shape of the material will change. In previous research, the material needs to be in a high-temperature environment to produce surface deformation in a direct current electric field, which greatly limits the application scenarios.

[0003] Therefore, it is urgent to find a method to overcome the defects of the above-mentioned responsive liquid crystal polymer materials. SUMMARY

[0004] The present application aims to at least solve one of the technical problems existing in the prior art. In previous research, the material needs to be in a high-temperature environment to produce surface deformation in a direct current electric field, which greatly limits the application scenarios. Therefore, by selecting a suitable monomer mixture and chain transfer agent, the raw materials are mixed together to react to form a cross-linked network of acrylic ester main chain polymers with polar groups, so that the material has a glass transition temperature lower than room temperature and softness. As shown in (a)-(c). Figure 1 (a) shows a schematic diagram of a main chain polymer formed by reaction of a single acrylic ester monomer;

[0005] Figure 1 (a) shows a schematic diagram of a main chain polymer formed by reaction of a single acrylic ester monomer; Figure 1 (b) shows a schematic diagram of a side chain polymer formed by reaction of a double acrylic ester monomer; Figure 1 (c) shows a schematic diagram of a liquid crystal polymer network formed by reaction of a single acrylic ester monomer and a double acrylic ester monomer.

[0006] In the chemical structural formula in the specification, "*" indicates the position of the chemical bond connection.

[0007] To this end, the present application provides a flexible electric response liquid crystal polymer material, which has the characteristics of convenient preparation, low glass transition temperature and wide application range, and can make up for the shortcomings of the current electric response liquid crystal polymer material which needs to be in a high temperature environment to produce surface deformation in a direct current electric field.

[0008] The preparation raw materials of the flexible electric response liquid crystal polymer material include: a liquid crystal monomer mixture, a chain transfer agent, and a catalyst.

[0009] The liquid crystal monomer mixture includes a diacrylate monomer and a monoacrylate monomer.

[0010] The chain transfer agent is an organic sulfur compound containing a thiol group.

[0011] Further, the diacrylate monomer is a monomer containing two acrylate groups in the molecular structure, and the diacrylate monomer has the following structure:

[0012]

[0013] R1 is selected from one or more of ester groups, alkoxy groups, aromatic rings, alkyl groups, and other units of combinations thereof.

[0014] Further, the monoacrylate monomer is a monomer containing one acrylate group and a polar group in the molecular structure, and the monoacrylate monomer has the following structure:

[0015]

[0016] wherein M is a polar group, independently selected from one of cyano group, hydroxyl group, amino group, and carbonyl group; preferably, the polar group is selected from cyano group.

[0017] The structure of R2 is selected from one or more of ester groups, alkoxy groups, aromatic rings, alkyl groups, and other units of combinations thereof.

[0018] Further, R1 can be selected from, but not limited to

[0019]

[0020] one of the following structures.

[0021] Further, R2 can be selected from, but not limited to

[0022] one of the following structures.

[0023] Preferably, the diacrylate monomer adopts TPGDA (tri(propylene glycol) diacrylate);

[0024] Preferably, the single acrylate monomer adopts RM23 (4-cyanophenyl 4'-(6-acryloyloxy hexyloxy) benzoate);

[0025] Further, the organic sulfur compound containing four thiol groups is a structure as follows:

[0026]

[0027] Wherein, R3 is a unit with a functionality of 4;

[0028] The R3 is selected from one or more of aromatic group, ester group, alkoxy group, alkyl group, and combination unit thereof.

[0029] Further, the R3 can be selected from, but not limited to:

[0030]

[0031] Preferably, the chain transfer agent adopts PETMP (pentaerythritol tetra-3-mercaptopropionate).

[0032] Further, the preparation raw material of the flexible electric response liquid crystal polymer material includes: 5-60wt% of single acrylate monomer, 5-30wt% of double acrylate monomer, 10-70wt% of chain transfer agent, 0.5-2.0wt% of catalyst.

[0033] Preferably, the optimal mass fraction ratio of the preparation raw material of the flexible electric response liquid crystal polymer material is: 55wt% of single acrylate monomer, 12wt% of double acrylate monomer, 32wt% of chain transfer agent, and 1wt% of catalyst, and the material prepared by using the ratio has the best electric response effect, and the surface morphology can be restored to the initial state after the electric field is removed.

[0034] Further, the mass fraction ratio of the liquid crystal monomer mixture to the chain transfer agent is 5:1-1:5.

[0035] Further, the mass fraction ratio of the single acrylate monomer to the double acrylate monomer is 1:6-6:1.

[0036] Another object of the present application is to provide a preparation method of the flexible electric response liquid crystal polymer material, which comprises the following steps:

[0037] S1. The liquid crystal monomer mixture, the chain transfer agent, and the catalyst are heated, melted, and stirred to obtain a mixture I;

[0038] S2. The mixture I is subjected to polymerization reaction to obtain the flexible electric response liquid crystal polymer material.

[0039] Further, in step S2, the temperature of the polymerization reaction is above the clearing point of the liquid crystal monomer mixture, and the reaction time is 12-16 hours.

[0040] A further object of the present application is to provide the use of the flexible electrically responsive liquid crystal polymer material in self-cleaning surfaces and touch displays.

[0041] The present application has the following advantages:

[0042] The flexible electrically responsive liquid crystal polymer material disclosed in the present application does not need to be driven by heat or light, and it itself responds to electric fields. The thin film made of the material can change its surface morphology by changing the orientation of the liquid crystal molecules inside it in a direct current electric field at room temperature, and the orientation of the liquid crystal molecules and the surface morphology can be reversibly restored to the initial state after the electric field is removed. It can generate shock by the reversible surface morphology change of the material to remove dust on the surface, and can be used in the fields of self-cleaning surfaces and touch displays. In previous studies, electrically responsive liquid crystal polymer materials often have a high glass transition temperature and need to be in a high temperature environment to respond to electric fields. In the present application, a single acrylate monomer and a double acrylate monomer are connected to form a liquid crystal polymer network by reacting with a suitable chain transfer agent, an organic sulfur compound containing a tetra-thiol group. The network density is moderate, it can change its surface morphology by changing the orientation of the liquid crystal molecules inside it in a direct current electric field at room temperature, and the orientation of the liquid crystal molecules and the surface morphology can be reversibly restored to the initial state after the electric field is removed, and it also has a glass transition temperature below room temperature, and can reversibly respond to electric fields at room temperature. BRIEF DESCRIPTION OF DRAWINGS

[0043] The present application will be further described below in conjunction with the drawings and examples, in which:

[0044] Figure 1 (a) shows a schematic diagram of the main chain polymer formed by the reaction of a single acrylate monomer; Figure 1 (b) shows a schematic diagram of the side chain polymer formed by the reaction of a double acrylate monomer; Figure 1 (c) shows a schematic diagram of the liquid crystal polymer network synthesized by the single acrylate monomer and the double acrylate monomer.

[0045] Figure 2 (a) shows a schematic diagram of the change in the arrangement of liquid crystal molecules in the thin film prepared in the test example of the present application without an electric field; Figure 2 (b) shows a schematic diagram of the change in the arrangement of liquid crystal molecules in the thin film prepared in the test example of the present application with an electric field.

[0046] Figure 3(a) shows a diagram of the liquid crystal molecule orientation state of the thin film prepared in the test example of the present invention without an electric field; Figure 3 (b) shows a diagram of the liquid crystal molecule orientation state when an electric field is applied to the thin film prepared in the test example of the present invention; Figure 3 (c) shows a diagram of the liquid crystal molecule orientation state when the electric field is removed from the thin film prepared in the test example of the present invention.

[0047] Figure 4 (a) shows a surface morphology diagram of the thin film prepared in the test example of the present invention when an electric field is applied; Figure 4 (b) shows the surface morphology of the thin film prepared in the test example of the present invention after the electric field was removed. Detailed Implementation

[0048] To more clearly illustrate the technical solution of the present invention, the following embodiments are provided. Unless otherwise stated, the raw materials, reactions, and post-processing methods appearing in the embodiments are all commercially available raw materials and technical methods well known to those skilled in the art.

[0049] Details of the chemical reagents used in the embodiments of this invention are as follows:

[0050] The monoacrylate liquid crystal monomer RM23 (4-cyanophenyl 4'-(6-acryloyloxyhexyloxy)benzoate) was purchased from Jiangsu Hecheng New Materials Co., Ltd.

[0051] The diacrylate liquid crystal monomers—TPGDA (tripropylene glycol diacrylate), were purchased from Tokyo Chemical Industry Co., Ltd.; LC756 ((3R,3AR,6S,6AR)-hexahydrofuran[3,2-B]furan-3,6-dimethylbis(4-((acryloyloxy)butoxy)carbonyl)oxy)benzoyl)oxy)benzoate) and RM82 (bis(6'-acryloyloxyhexyloxy)methylhydroquinone ester) were purchased from Jiangsu Hecheng New Materials Co., Ltd.

[0052] The catalyst, α-methylbenzylamine, was purchased from Sigma-Aldrich Chemicals.

[0053] Chain transfer agent – ​​PETMP (pentaerythritol tetra-3-mercaptopropionate), purchased from Sigma-Aldrich Chemicals.

[0054] Example 1

[0055] A flexible electroresponsive liquid crystal polymer material, the preparation method of which includes the following steps:

[0056] S1. Take raw materials in total 1.0 g in the following weight percentage: 55wt% of RM23, 12wt% of TPGDA, 32wt% of chain transfer agent, 1wt% of catalyst, melt the above raw materials by hot air gun and stir uniformly to obtain mixture I.

[0057] S2. Heat mixture I to 130℃ to carry out thermal polymerization reaction for 12h to obtain the flexible electro-responsive liquid crystal polymer material.

[0058] Example 2

[0059] S1. Take raw materials in total 1.0 g in the following weight percentage: 45wt% of RM23, 20wt% of RM82, 34wt% of chain transfer agent, 1wt% of catalyst, melt the above raw materials by hot air gun and stir uniformly to obtain mixture I.

[0060] S2. Heat mixture I to 130℃ to carry out thermal polymerization reaction for 12h to obtain the flexible electro-responsive liquid crystal polymer material.

[0061] Example 3

[0062] S1. Take raw materials in total 1.0 g in the following weight percentage: 40wt% of RM23, 40wt% of LC 756, 19wt% of chain transfer agent, 1wt% of catalyst, melt the above raw materials by hot air gun and stir uniformly to obtain mixture I.

[0063] S2. Heat mixture I to 130℃ to carry out thermal polymerization reaction for 12h to obtain the flexible electro-responsive liquid crystal polymer material.

[0064] Test Example

[0065] The flexible electro-responsive liquid crystal polymer material prepared in Example 1 is tested for its electro-responsive property, and the testing method is as follows:

[0066] Preparation of flexible electro-responsive liquid crystal polymer film: melt the flexible electro-responsive liquid crystal polymer material prepared in Example 1 by hot air gun, coat on the interdigital electrode with glass as substrate, add 30μm spacers to the four corners of the glass substrate to control the thickness, cover with a glass cover plate on the top, and polymerize at 130℃ for 12h to prepare the film, and then naturally cool to room temperature after polymerization to obtain the flexible electro-responsive liquid crystal polymer film (30μm);

[0067] Figure 2 (a) shows the schematic diagram of the change of liquid crystal molecular arrangement of the film prepared in the test example of the present application without electric field; Figure 2 (b) shows the schematic diagram of the change of liquid crystal molecular arrangement of the film prepared in the test example of the present application with electric field.

[0068] The test conditions were as follows: At room temperature (25°C), the positive and negative terminals of the interdigitated electrodes of the glass-based substrate with a flexible electroresponsive liquid crystal polymer film were connected to the two terminals of a DC power supply with a voltage of 300V. The results are as follows. Figure 3 (a)-(c) Figure 4 As shown in (a)-(b).

[0069] Figure 3 (a) shows a diagram of the liquid crystal molecule orientation state of the thin film prepared in the test example of the present invention without an electric field; Figure 3 (b) shows a diagram of the liquid crystal molecule orientation state when an electric field is applied to the thin film prepared in the test example; Figure 3 (c) shows a diagram of the liquid crystal molecule orientation state when the electric field is removed from the thin film prepared in the test example of the present invention;

[0070] Figure 4 (a) shows the surface morphology of the thin film prepared in the test example when an electric field is applied; Figure 4 (b) shows the surface morphology of the thin film prepared in the test example after the electric field was removed.

[0071] from Figure 3 (a)-(c) Figure 4 As can be seen from (a)-(b), under room temperature and without an applied electric field, the liquid crystal molecules in the thin film prepared from the flexible electroresponsive liquid crystal polymer material are in a multi-domain or isotropic state, arranged randomly. After applying an electric field, the liquid crystal molecules in the thin film change their orientation and align neatly along the electric field lines, thereby changing the surface morphology of the thin film. After removing the electric field, the orientation of the liquid crystal molecules and the surface morphology of the thin film reversibly return to their initial state, making it applicable to the field of touch displays. Simultaneously, by repeatedly applying or removing an electric field to the interdigitated electrodes, the thin film can generate oscillations through reversible changes in the surface morphology of the material to remove surface dust, making it applicable to the field of self-cleaning surfaces.

[0072] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments and test examples described above, and that the invention can be implemented in other specific forms without departing from the spirit or essential characteristics of the invention. Therefore, the embodiments and test examples should be considered in all respects as exemplary and not restrictive, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, it is intended that all variations falling within the meaning and scope of equivalents of the claims be included within the present invention.

[0073] Furthermore, it should be understood that although the specification is described in terms of embodiments, not every embodiment includes every feature or implementation described herein. The specification can include implicit combinations of explicitly mentioned features and / or implicit combinations of implicitly mentioned features. Such combinations are also expressly included within the scope of the specification and an embodiment.

Claims

1. A flexible electroresponsive liquid crystal polymer material, characterized in that, The raw materials for preparing the flexible electroresponsive liquid crystal polymer material include: a mixture of liquid crystal monomers, a chain transfer agent, and a catalyst; The liquid crystal monomer mixture includes diacrylate monomers and monoacrylate monomers; The chain transfer agent is an organic sulfur compound containing a tetrathiol group; The diacrylate monomer is a monomer whose molecular structure contains two acrylate groups, and the diacrylate monomer has the following structure: ； R1 is selected from one or more of ester, alkoxy, aromatic, and alkyl groups; The monoacrylate monomer is a monomer whose molecular structure contains an acrylate group and a polar group, and the monoacrylate monomer has the following structure: ； Wherein, M is a polar group, selected from one of cyano, hydroxyl, amino, and carbonyl groups; R2 is selected from one or more ester groups, alkoxy groups, aromatic groups, and alkyl groups; The organosulfur compound containing a tetrathiol group has the following structure: ； Among them, R3 is a unit with a functionality of 4; The R3 is selected from one or more of aromatic, ester, alkoxy, and alkyl groups; The mass fraction ratio of the liquid crystal monomer mixture to the chain transfer agent is 5:1 to 1:5; The mass fraction ratio of the monoacrylate monomer to the diacrylate monomer is 1:6-6:

1.

2. The method for preparing the flexible electroresponsive liquid crystal polymer material according to claim 1, characterized in that, The preparation method of the flexible electroresponsive liquid crystal polymer material includes the following steps: S1. The liquid crystal monomer mixture, chain transfer agent, and catalyst are heated, melted, and stirred to obtain mixture I; S2. Mixture I undergoes a polymerization reaction to obtain a flexible electroresponsive liquid crystal polymer material.

3. The method for preparing the flexible electroresponsive liquid crystal polymer material according to claim 2, characterized in that, In step S2, the polymerization temperature is above the clearing point of the liquid crystal monomer mixture, and the reaction time is 12-16 hours.

4. The application of the flexible electroresponsive liquid crystal polymer material according to claim 1 in the fields of self-cleaning surfaces and touch displays.

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