Liquid crystal elastomer ink for 3D printing and preparation method thereof

Abstract

The invention relates to liquid crystal elastomer ink for 3D printing and a preparation method thereof, belongs to the technical field of high polymer materials, and solves the problem that mechanical properties of materials are difficult to adjust in the prior art. The liquid crystal elastomer adopted by the liquid crystal elastomer ink for 3D printing comprises the following raw materials: a liquid crystal unit oligomer of a component A and a component B, wherein the acrylate monomer, the chain extender and the catalyst form a liquid crystal unit oligomer of the component A; the chain extender and the photoinitiator form a component B; the liquid crystal elastomer ink does not contain a solvent, so that the storage time is greatly prolonged; in addition, the raw materials are prepared into two components, and the component A and the component B can be used for extrusion type 3D printing after being simply mixed. The modulus and the actuating strain of the printed sample can be regulated and controlled through the ratio of the component A to the component B. The operation is simple, and the controllability is high.

Description

Technical Field

[0001] The present invention relates to the technical field of polymer materials, and in particular to a liquid crystal elastomer ink for 3D printing and a preparation method thereof, and in particular to a liquid crystal elastomer ink for 3D printing with adjustable mechanical properties and a preparation method thereof. Background Art

[0002] Smart materials are a type of functional materials that can undergo macroscopic deformation when external conditions change. They have been widely used in the fields of deformable structures, intelligent robots, etc., including traditional shape memory alloys, shape memory polymers, dielectric elastomers, smart hydrogels, liquid crystal elastomers, etc. Compared with traditional smart materials, liquid crystal elastomers have the advantages of anisotropic contraction, strong deformation ability, fast response speed, mild stimulation conditions, and good reversible cycle performance. In addition, liquid crystal elastomers can be made into different contraction modes through 3D printing methods, which meets the multi-faceted needs of the intelligent field for high-performance smart soft materials, has attracted widespread attention, and has broad development potential.

[0003] Liquid crystal elastomers are generally prepared by liquid crystal box orientation curing, mechanical stretching, electrospinning, and extrusion 3D printing methods. The existing preparation method of liquid crystal elastomer ink involving extrusion 3D printing method is composed of a single component of acrylate-terminated liquid crystal oligomers, and it is difficult to achieve the regulation of modulus and actuation strain of the ink.

[0004] Chinese patent CN115710354B discloses a method of dissolving a liquid crystal monomer, a cross-linking agent and a chain extender in an organic solvent, mixing them evenly, continuing to add an ionic liquid to mix evenly to form a mixed solution, and then initiating a cross-linking reaction. This method can produce a liquid crystal elastomer composite film with excellent mechanical properties. However, the solvent needs to be removed during the film preparation process, the preparation cycle is long, and it is not suitable for 3D printing. CN114851551B prepares a liquid crystal elastomer 3D printing ink by mixing a liquid crystal macromolecular monomer with a photoinitiator, a cross-linking agent, a thermal initiator and a thiol at room temperature, and reacting after melting. However, the reaction time is long, and it takes 3-48 hours to ensure that the reaction is complete, which affects the printing efficiency. Summary of the invention

[0005] In view of the above problems, the present invention provides a liquid crystal elastomer ink for 3D printing and a preparation method thereof, which solves the problem that the mechanical properties of materials are difficult to adjust in the prior art.

[0006] The present invention provides a liquid crystal elastomer ink for 3D printing, wherein the raw material of the ink is a liquid crystal elastomer, and the raw material for preparing the liquid crystal elastomer includes a liquid crystal oligomer of component A and a component B;

[0007] The acrylate monomer, chain extender and catalyst constitute the liquid crystal oligomer of component A; the chain extender and photoinitiator constitute the component B; and the acrylate liquid crystal monomer is a diacrylate-terminated liquid crystal monomer.

[0008] Optionally, the acrylate liquid crystal monomer is 1,4-bis-[4-(3-acryloxypropoxy)benzoyloxy]-2-methylbenzene (RM257), 1,4-bis-[4-(6-acryloxyhexyloxy)benzoyloxy]-2-methylbenzene or 4-((6-(acryloxy)hexyl)oxy)phenyl 4-((6-(acryloxy)hexyl)oxy)benzoate.

[0009] Optionally, the chain extender is a dithiol.

[0010] Optionally, the dithiol is 3,6-dioxa-1,8-octanedithiol, 1,3-propanedithiol or 1,5-pentanedithiol, or the like.

[0011] Optionally, the catalyst is di-n-propylamine.

[0012] Optionally, the photoinitiator is 2-hydroxy-4'-(2-hydroxyethoxy)-2-methylpropiophenone.

[0013] Optionally, the molar ratio of the acrylic ester liquid crystal monomer to the chain extender is 2:1-7:6.

[0014] Optionally, the photoinitiator is 0.2wt%-1.0wt% of the total mass of the liquid crystal elastomer ink system.

[0015] Another aspect of the present invention further provides a method for preparing a liquid crystal elastomer ink for 3D printing, which is used to prepare the aforementioned liquid crystal elastomer ink for 3D printing, and the specific steps are as follows:

[0016] Step 1, dissolving an acrylic acid ester liquid crystal monomer in a solvent; adding a chain extender and a catalyst and stirring to obtain a mixed solution;

[0017] Step 2, stirring the mixed solution to react to obtain a liquid crystal elastomer oligomer solution;

[0018] Step 3, removing the solvent in the liquid crystal elastomer oligomer solution to obtain component A;

[0019] Step 4, uniformly mixing the photoinitiator and the chain extender to obtain component B;

[0020] Step 5: Evenly mix components A and B to obtain liquid crystal elastomer ink.

[0021] Compared with the prior art, the present invention has at least the following beneficial effects:

[0022] (1) The liquid crystal elastomer ink of the present invention does not contain solvent, which greatly increases the shelf life.

[0023] (2) The present invention prepares the raw materials into two components, and can be used for extrusion 3D printing by simply mixing the two components AB. The modulus and actuation strain of the printed sample can be adjusted by the ratio of the two components AB. The operation is simple and the controllability is strong. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 It is the mechanical curve of the liquid crystal elastomer of the present invention. DETAILED DESCRIPTION

[0025] In order to more clearly understand the above-mentioned purpose, features and advantages of the present invention, the present invention is further described in detail below in conjunction with the accompanying drawings and specific embodiments. It should be noted that, in the absence of conflict, the embodiments of the present invention and the features in the embodiments can be combined with each other. In addition, the present invention can also be implemented in other ways different from those described herein, and therefore, the protection scope of the present invention is not limited by the specific embodiments disclosed below.

[0026] A specific embodiment of the present invention, as Figure 1 , discloses a liquid crystal elastomer ink for 3D printing, wherein the raw material of the ink is a liquid crystal elastomer, and the raw materials for preparing the liquid crystal elastomer include an acrylate monomer, a chain extender, a catalyst and a photoinitiator.

[0027] The acrylate monomer, the chain extender and the catalyst constitute the liquid crystal oligomer (component A); the chain extender and the photoinitiator constitute the component B.

[0028] Specifically, the acrylate monomer is 1,4-bis-[4-(3-acryloxypropoxy)benzoyloxy]-2-methylbenzene (RM257); the chain extender is 3,6-dioxa-1,8-octanedithiol (EDDET); the catalyst is di-n-propylamine (DPA); and the photoinitiator is 2-hydroxy-4′-(2-hydroxyethoxy)-2-methylpropiophenone (I2959).

[0029] The structural formulas are:

[0030]

[0031] In order to illustrate the effectiveness of the method proposed in the present invention, the above technical solution is described in detail through experiments below, and the specific implementation steps are as follows:

[0032] (1) 7.06 g of acrylate monomer RM257 is reacted with 1.46 g of dithiol chain extender EDDET and 0.03 g of catalyst DPA to obtain component A;

[0033] (2) 0.36 g of EDDET and 0.05 g of I2595 were mixed to obtain component B;

[0034] (3) 8.55 g of component A and 0.41 g of component B were mixed at 80°C;

[0035] (4) Vacuum to remove air bubbles;

[0036] (5) adding the 3D printer syringe to print, and then post-curing with a UV lamp for 30 minutes to obtain a single-domain liquid crystal elastomer;

[0037] Effect: The tensile modulus of the single-domain liquid crystal elastomer finally obtained by 3D printing can reach 9MPa, and the actuation strain is 45.0%.

[0038] On the other hand, the present invention also discloses a method for preparing the liquid crystal elastomer ink for 3D printing, the specific steps of which are:

[0039] Step 1, dissolving an acrylate liquid crystal monomer in dichloromethane; adding dithiol and a catalyst and stirring to obtain a mixed solution;

[0040] Further, the acrylate liquid crystal monomer is a different diacrylate-terminated liquid crystal monomer such as 1,4-bis-[4-(3-acryloxypropoxy)benzoyloxy]-2-methylbenzene (RM257), 1,4-bis-[4-(6-acryloxyhexyloxy)benzoyloxy]-2-methylbenzene (RM82) or 4-((6-(acryloxy)hexyl)oxy)phenyl 4-((6-(acryloxy)hexyl)oxy)benzoate (C6BAPE);

[0041] Furthermore, the dithiol is 3,6-dioxa-1,8-octanedithiol, 1,3-propanedithiol or 1,5-pentanedithiol.

[0042] Furthermore, the catalyst is di-n-propylamine (DPA).

[0043] Furthermore, the molar ratio of the acrylic ester liquid crystal monomer to the dithiol is 2:1-7:6, preferably 3:2 or 2:1.

[0044] Preferably, the acrylic ester liquid crystal monomer is 1,4-bis-[4-(3-acryloxypropoxy)benzoyloxy]-2-methylbenzene; the dithiol is 3,6-dioxa-1,8-octanedithiol; and the catalyst is di-n-propylamine (DPA).

[0045] Furthermore, the catalyst is used in an amount of 1% to 3% of the molar amount of the acrylic ester liquid crystal monomer, preferably 2%.

[0046] Step 2, stirring the mixed solution at room temperature to react to obtain a liquid crystal elastomer oligomer solution;

[0047] Furthermore, the reaction time is 12 hours.

[0048] Step 3, removing dichloromethane from the liquid crystal elastomer oligomer solution by rotary evaporation to obtain component A;

[0049] Furthermore, the solvent removal time is 0.5 hours.

[0050] Step 4, uniformly mixing the photoinitiator and dithiol to obtain component B;

[0051] Furthermore, the photoinitiator is 2-hydroxy-4′-(2-hydroxyethoxy)-2-methylpropiophenone (I2959); and the dithiol is 3,6-dioxa-1,8-octanedithiol.

[0052] Preferably, the photoinitiator is 0.2wt%-1.0wt% of the total mass of the liquid crystal elastomer ink system, preferably 0.5wt%.

[0053] Preferably, the amount of dithiol used is determined according to the required mechanical properties, thereby obtaining a liquid crystal elastomer ink for 3D printing with adjustable mechanical properties.

[0054] Furthermore, the relationship between the mass of dithiol and the tensile modulus of the liquid crystal elastomer is:

[0055] y=2.5*10 7 -6.7*10 7 x+6.0*10 7 x 2 -1.8*10 7 x 3

[0056] Wherein, x is the mass of dithiol, and y is the tensile modulus of the liquid crystal elastomer finally prepared.

[0057] Step 5: Evenly mix components A and B at a mass ratio of 50-5:1 to obtain liquid crystal elastomer ink.

[0058] The preferred ratio is 15:1.

[0059] Furthermore, the relationship between the mass ratio of components A and B and the tensile modulus of the liquid crystal elastomer is:

[0060] y=4.6*10 5 -1.5*10 5 z+1.4*10 4 z 2 +2.7*10 2 z 3

[0061] Wherein, z is the mass ratio of components A and B, and y is the tensile modulus of the liquid crystal elastomer finally prepared.

[0062] Step 6: The liquid crystal elastomer ink is 3D printed by an extrusion-type 3D printing device equipped with a UV curing device.

[0063] Furthermore, the ultraviolet lamp irradiation time is 15-20 minutes, the ultraviolet light wavelength is 365nm, the power is 20W, and the irradiation distance is 5cm-15cm.

[0064] In order to illustrate the effectiveness of the method proposed in the present invention, the above technical solution of the present invention is described in detail below through a specific embodiment, and the specific implementation steps are as follows:

[0065] Example 1

[0066] A method for preparing liquid crystal elastomer ink for 3D printing comprises the following steps:

[0067] (1) 8.18 g of component A and 0.04 g of photoinitiator I2959 (nA (oligomer): nB (EDDET) = 3:0) were mixed at 80° C., wherein n represents the amount of the substance;

[0068] It is understood that the amount of substance is the theoretical molar number of the oligomer and the molar number of EDDET, for example, 2 mmol of EDDET is used for 6 mmol of the oligomer.

[0069] (2) Vacuum to remove air bubbles;

[0070] (3) pouring into a mold and curing under ultraviolet light at room temperature for 20 min to obtain a multi-domain LCE (liquid crystal elastomer ink);

[0071] Example 2

[0072] A method for preparing liquid crystal elastomer ink for 3D printing comprises the following steps:

[0073] (1) 8.18 g of component A and 0.41 g of component B (nA (oligomer): nB (EDDET) = 3:1) were mixed at 80°C;

[0074] (2) Vacuum to remove air bubbles;

[0075] (3) Pour into a mold and cure under UV light at room temperature for 20 min to obtain a multi-domain LCE;

[0076] Example 3

[0077] A method for preparing liquid crystal elastomer ink for 3D printing comprises the following steps:

[0078] (1) 8.18 g of component A and 0.82 g of component B (nA (oligomer): nB (EDDET) = 3:2) were mixed at 80°C;

[0079] (2) Vacuum to remove air bubbles;

[0080] (3) Pour into a mold and cure under UV light at room temperature for 20 min to obtain a multi-domain LCE;

[0081] Example 4

[0082] A method for preparing liquid crystal elastomer ink for 3D printing comprises the following steps:

[0083] (1) 8.18 g of component A and 1.23 g of component B (n(oligomer):nB(EDDET)=1:1) were mixed at 80°C;

[0084] (2) Vacuum to remove air bubbles;

[0085] (3) Pour into a mold and cure under UV light at room temperature for 20 min to obtain a multi-domain LCE;

[0086] Example 5

[0087] A method for preparing liquid crystal elastomer ink for 3D printing comprises the following steps:

[0088] (1) 8.18 g of component A and 1.64 g of component B (n(oligomer):nB(EDDET)=3:4) were mixed at 80°C;

[0089] (2) Vacuum to remove air bubbles;

[0090] (3) Pour into a mold and cure under UV light at room temperature for 20 min to obtain a multi-domain LCE;

[0091] Performance Testing

[0092] (1) Mechanical properties test

[0093] The LCE samples prepared in Examples 1 to 5 were subjected to uniaxial tensile testing on an electronic universal testing machine (WANCE), with sample dimensions of 30 mm × 10 mm × 0.5 mm and a tensile rate of 0.2 min. -1 , the results are as follows Figure 1 As shown. By simply changing the ratio and amount of component B, the mechanical properties of LCE are also well adjustable. In Examples 1 to 4, the tensile strength of LCE can reach up to 12.68 MPa, the elongation at break can reach up to 362%, and the modulus can reach up to 58.12 MPa.

[0094] (2) Comparative test between the prior art and the present invention

[0095] Cai et al. printed a three-dimensional liquid crystal elastomer structure capable of gradient deformation by changing the printing parameters, greatly increasing the design space of actively deformable structures (Science Advances, 2020, 6(39): eabc0034). However, it is inconvenient to adjust the mechanical properties of the material, and it is necessary to change the proportion of raw materials and the preparation method from the very beginning. The present invention can significantly adjust the mechanical properties of the material by only changing the proportion of components A and B.

[0096] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by any technician familiar with the technical field within the technical scope disclosed by the present invention should be covered within the protection scope of the present invention.

Claims

1. A liquid crystal elastomer ink for 3D printing, wherein the raw material of the ink is a liquid crystal elastomer, characterized in that: The raw materials for preparing the liquid crystal elastomer include a liquid crystal oligomer of component A and a component B; The acrylate monomer, chain extender and catalyst constitute the liquid crystal oligomer of component A; the chain extender and photoinitiator constitute the component B; and the acrylate liquid crystal monomer is a diacrylate-terminated liquid crystal monomer.

2. The liquid crystal elastomer ink for 3D printing according to claim 1, characterized in that: The acrylic acid ester liquid crystal monomer is 1,4-bis-[4-(3-acryloxypropoxy)benzoyloxy]-2-methylbenzene (RM257), 1,4-bis-[4-(6-acryloxyhexyloxy)benzoyloxy]-2-methylbenzene or 4-((6-(acryloxy)hexyl)oxy)phenyl 4-((6-(acryloxy)hexyl)oxy)benzoate.

3. The liquid crystal elastomer ink for 3D printing according to claim 1, characterized in that: The chain extender is dithiol.

4. The liquid crystal elastomer ink for 3D printing according to claim 3, characterized in that: The dithiol is 3,6-dioxa-1,8-octanedithiol, 1,3-propanedithiol or 1,5-pentanedithiol.

5. The liquid crystal elastomer ink for 3D printing according to claim 1, characterized in that: The catalyst is di-n-propylamine.

6. The liquid crystal elastomer ink for 3D printing according to claim 1, characterized in that: The photoinitiator was 2-hydroxy-4′-(2-hydroxyethoxy)-2-methylpropiophenone.

7. The liquid crystal elastomer ink for 3D printing according to claim 1, characterized in that: The molar ratio of the acrylic ester liquid crystal monomer to the chain extender is 2:1-7:

6.

8. The liquid crystal elastomer ink for 3D printing according to claim 1, characterized in that: The photoinitiator accounts for 0.2wt%-1.0wt% of the total mass of the liquid crystal elastomer ink system.

9. A method for preparing a liquid crystal elastomer ink for 3D printing, for preparing the liquid crystal elastomer ink for 3D printing according to any one of claims 1 to 8, characterized in that: The specific steps are as follows: Step 1, dissolving an acrylic acid ester liquid crystal monomer in a solvent; adding a chain extender and a catalyst and stirring to obtain a mixed solution; Step 2, stirring the mixed solution to react to obtain a liquid crystal elastomer oligomer solution; Step 3, removing the solvent in the liquid crystal elastomer oligomer solution to obtain component A; Step 4, uniformly mixing the photoinitiator and the chain extender to obtain component B; Step 5: Evenly mix components A and B to obtain liquid crystal elastomer ink.

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