Formula of shape memory part based on photopolymerization carbazole liquid crystal 3D printing, shape memory part and preparation method of shape memory part

Abstract

The invention belongs to the technical field of materials, and relates to a formula for 3D printing of a shape memory part based on photopolymerization carbazole liquid crystal, the shape memory part and a preparation method thereof.The formula is composed of hydrogel monomers, liquid crystal monomers, a cross-linking agent and a photoinitiator, and the cross-linking agent is photopolymerization carbazole liquid crystal. In the formula, the carbazole liquid crystal with an optimized structure is adopted as a cross-linking agent, and a carbazole functional group is introduced into the carbazole liquid crystal, so that the photosensitive responsiveness and the electronic transmission performance of the material are enhanced; the carbazole liquid crystal material adopted by the invention can form highly ordered molecular arrangement in 3D printing, so that the material has anisotropy and programmable deformability. And through a photocuring technology, the liquid crystal molecular network can realize reversible deformation under external stimulation, so that the shape memory liquid crystal hydrogel is prepared and is widely applied to the field of flexible electronic and intelligent materials.

Description

Technical Field

[0001] The present invention belongs to the technical field of materials, relates to the technical field of 3D printing liquid crystal intelligent materials, and particularly relates to a formulation, a shape memory component and a preparation method thereof for 3D printing a shape memory component based on photopolymerizable carbazole liquid crystal. Background Art

[0002] As a disruptive manufacturing process, 3D printing (additive manufacturing) technology has been widely applied in fields such as aerospace, biomedicine, electronic devices, and automotive manufacturing in recent years. Compared with traditional subtractive manufacturing and forming manufacturing technologies, 3D printing can directly construct complex three-dimensional structures based on digital models by layer-by-layer material accumulation, not only improving material utilization but also reducing waste during the processing. In addition, as a further extension of 3D printing, 4D printing can utilize the response characteristics of intelligent materials to enable controllable changes in the shape or performance of printed structures under external stimuli (such as temperature, light, electric field or magnetic field), thereby endowing materials with broader adaptability. Especially in terms of high precision, high complexity, low material loss, and personalized manufacturing, additive manufacturing technology has shown irreplaceable advantages. However, although photocuring 3D printing technologies (such as digital light processing DLP and stereolithography SLA) are favored for their high resolution and rapid prototyping capabilities, they still face challenges such as a single material system and limited curing processes. Therefore, developing new photocurable materials with specific functions to further expand the application boundaries of additive manufacturing technology is a current research hotspot.

[0003] Liquid crystal materials have been widely applied in fields such as display, sensing, photonics, and intelligent materials due to their unique molecular orientation and tunable physical and chemical properties. In particular, photopolymerizable liquid crystal materials combine the high order of liquid crystal molecules and the rapid curing characteristics of photopolymer materials, making them have broad prospects in optical devices, programmable surfaces, flexible electronics, etc. The molecular orientation of photopolymerizable liquid crystal materials can be precisely regulated by external fields (such as electric field, magnetic field, light field), thereby endowing the materials with special optical anisotropy, reversible deformation or self-healing ability. In addition, the photocuring process can complete the construction of the polymer network in a short time, achieving a high-resolution and low-shrinkage forming effect. This characteristic makes photopolymerizable liquid crystal materials show significant advantages in 3D printing applications, such as high precision, high mechanical strength, and good environmental adaptability.

[0004] The photocuring 3D printing technology can rapidly form fine structures, and the self-assembly characteristics of liquid crystal materials endow the printed parts with unique anisotropy and controllability at the microscale. This combination is expected to promote the development of intelligent electronic skin, wearable devices, and advanced photonics. However, there are still some key problems to be solved in the current 3D printing system based on photopolymerized liquid crystals, such as the difficulty in controlling the orientation of liquid crystal molecules, the phase separation phenomenon during the curing process affecting the final mechanical properties, and the limited printing stability. In addition, the existing photocuring formulations are difficult to simultaneously achieve high mechanical strength, high optical properties, and excellent processing adaptability. Summary of the Invention

[0005] Aiming at the deficiencies of the existing technology, the purpose of the present invention is to provide a formulation for 3D printing shape memory parts based on photopolymerized carbazole liquid crystals. In the formulation of the present invention, the carbazole liquid crystal with optimized structure is used as a crosslinking agent. In the carbazole liquid crystal, a carbazole functional group is introduced to enhance the photosensitive response and electron transport properties of the material. The carbazole liquid crystal material used in the present invention can form a highly ordered molecular arrangement during 3D printing, endowing the material with anisotropy and programmable deformation ability. Through the photocuring technology, the liquid crystal molecular network can achieve reversible deformation under external stimuli, thus making a shape memory liquid crystal hydrogel, which is widely used in the fields of flexible electronics and intelligent materials.

[0006] The present invention is achieved through the following technical solutions:

[0007] A formulation for 3D printing shape memory parts based on photopolymerized carbazole liquid crystals, which is composed of the following components: hydrogel monomer, liquid crystal monomer, crosslinking agent, and photoinitiator. Among them, the crosslinking agent is photopolymerized carbazole liquid crystal, and the structure of the photopolymerized carbazole liquid crystal is shown in the following formula:

[0008]

[0009] In the formula, n = 1 - 30;

[0010] R1 and R2 are selected from substituted or unsubstituted alkyl groups with 1 - 20 carbon atoms. R1 and R2 are the same or different, and both R1 and R2 contain a photopolymerizable end group, and the photopolymerizable end group is one of the following groups:

[0011]

[0012] Further, the hydrogel monomer is a mixture of 2-acryloylhydrazine-1-carboxamide and acrylic acid;

[0013] And / or, the liquid crystal monomer is 6-((4'-cyano-[1,1'-biphenyl]-4-yl)oxy)hexyl acrylate;

[0014] And / or, the photoinitiator is diphenyl(2,4,6-trimethylbenzoyl)phosphine oxide.

[0015] Furthermore, in the hydrogel monomer, the molar ratio of 2-acryloylhydrazine-1-carboxamide to acrylic acid is 1:1 to 23.

[0016] Furthermore, the molar ratio of the crosslinking agent to the liquid crystal monomer is 1:10 to 36,

[0017] And / or, the mass ratio of the crosslinking agent to the hydrogel monomer is 1:10 to 52,

[0018] And / or, the mass ratio of the photoinitiator to the hydrogel monomer is 1:25 to 100.

[0019] A further improvement of the present invention is:

[0020] A photo-polymerized carbazole liquid crystal shape memory component, which is prepared by DLP 3D printing with the above formula.

[0021] A further improvement of the present invention is:

[0022] A preparation method of a photo-polymerized carbazole liquid crystal shape memory component, comprising the following steps:

[0023] Step (1): Mix the liquid crystal monomer and 2-acryloylhydrazine-1-carboxamide in an organic solution and completely dissolve them;

[0024] Step (2): Add a photoinitiator to the solution in step (1) and shake well until completely dissolved;

[0025] Step (3): Add a crosslinking agent and an acrylic acid monomer, heat and stir evenly to obtain a transparent printing ink;

[0026] Step (4): The printing ink forms a liquid crystal organic gel component under the ultraviolet light irradiation of a DLP 3D printer, and the organic solvent inside the liquid crystal organic gel is replaced with water by a solvent replacement method.

[0027] Furthermore, the organic solvent is dimethylformamide or dimethyl sulfoxide or a mixture of the two.

[0028] Furthermore, the heating temperature in step (3) is 50 - 150 °C.

[0029] Furthermore, the wavelength range of the ultraviolet light irradiation in step (4) is between 300 - 450 nm, and the replacement time is 3 - 15 days.

[0030] Compared with the prior art, the beneficial effects of the present invention are:

[0031] By reasonably designing the structure of the photopolymerizable liquid crystal monomer, the molecules are kept in a highly ordered arrangement during the printing process. Utilizing the excellent optical properties of the carbazole group, ultraviolet fluorescence visualization is provided, and the optical anisotropy and mechanical strength of the formed parts are enhanced. This method can be adapted to DLP 3D printing technology, enabling the rapid manufacturing of complex and delicate structures, providing new solutions for intelligent electronic skin, flexible sensors, and programmable materials, and broadening the application of photopolymerizable liquid crystal materials in the field of advanced manufacturing.

[0032] By reasonably regulating the photoinitiator system and curing process, the orderly arrangement of liquid crystal molecules during the curing process is ensured, thereby endowing the final formed structure with excellent optical and mechanical properties. The present invention not only provides a new material solution for the photocuring 3D printing technology, but also expands a new direction for the research and application of intelligent materials. Description of the Drawings

[0033] Figure 1 1H NMR spectrum of the photopolymerizable carbazole liquid crystal used in Example 1;

[0034] Figure 2 1H NMR spectrum of the photopolymerizable carbazole liquid crystal used in Example 2;

[0035] Figure 3 Stress-strain curves of the test specimens printed in the examples and comparative examples of the present invention;

[0036] Figure 4 The petal-shaped part printed in Example 1, and under the excitation of ultraviolet light at 365 nm, it presents a blue fluorescence image. Detailed Description of the Invention

[0037] The present invention will be introduced in detail below in conjunction with specific embodiments.

[0038] Example 1

[0039] (1) Preparation of the photopolymerizable carbazole liquid crystal (((9-propyl-9H-carbazole-2,7-diyl)bis(4,1-phenylene))bis(oxy))bis(ethane-2,1-diyl) diacrylate

[0040]

[0041] Synthesis of Intermediate (2)

[0042] Prepare a 100 mL Schlenk reaction flask, preheat it at 40 °C for 30 min for drying, then add compound 1 (5.60 g, 13.28 mmol) into the reaction flask. Evacuate and replace with argon three times. Use a syringe to inject 50 mL of chloroform to dissolve the compound to form solution A, and transfer it to a cryogenic reaction pump at -78 °C, and stir for 10 min. Prepare a single-neck vial. Under ice bath conditions, dissolve and dilute boron tribromide (19.96 g, 79.70 mmol) with 20 mL of dichloromethane to form solution B. Use a syringe to slowly add solution B dropwise to solution A. Stir vigorously at low temperature for 2 h, then slowly warm up to room temperature and continue the reaction for 12 h. Determine the end of the reaction by TLC. Slowly pour the reaction solution into 200 mL of aqueous solution and stir for 6 h to quench BBr3. Then extract the mixture with ethyl acetate. After removing the solvent using a rotary evaporator, the crude product is purified by column chromatography with PE:Ea = 25:1 - 10:1 (v / v) to obtain the intermediate (2) as a white solid with a yield of 89%.

[0043] Synthesis of liquid crystal compound (4)

[0044] Prepare a 100 mL two-neck round-bottom flask, add compound 2 (3.00 g, 7.62 mmol) and potassium carbonate (2.95 g, 21.34 mmol). Evacuate and replace with argon, and maintain an argon atmosphere. Use a syringe to draw DMF (30 mL) and inject it. Stir and heat to reflux at 100 °C. After 12 h, add compound 3 (5.01 g, 21.34 mmol) and continue stirring for 24 h. After the reaction is completed, add water to precipitate the crude product. The remaining solution is extracted with dichloromethane. After removing the solvent using a rotary evaporator, the obtained crude product is purified by column chromatography. The eluent is PE:DCM = 1:10 - 1:2 (v / v). The liquid crystal compound (4) is a white powder, and the reaction yield is 77%.

[0045] 11H NMR (400 MHz, Chloroform-d) δ 8.10 (d, J = 8.0 Hz, 2H), 7.65 (d, J = 8.8 Hz, 4H), 7.53 (d, J = 1.5 Hz, 2H), 7.43 (dd, J = 8.1, 1.5 Hz, 2H), 7.01 (d, J = 8.8 Hz, 4H), 6.41 (dd, J = 17.3, 1.5 Hz, 2H), 6.13 (dd, J = 17.3, 10.4 Hz, 2H), 5.82 (dd, J = 10.4, 1.5 Hz, 2H), 4.35 (t, J = 7.2 Hz, 2H), 4.19 (t, J = 6.6 Hz, 4H), 4.04 (t, J = 6.4 Hz, 4H), 2.02–1.93 (m, 2H), 1.89–1.81 (m, 4H), 1.78–1.69 (m, 4H), 1.54–1.44 (m, 8H), 1.02 (t, J = 7.4 Hz, 3H).

[0046] (2) Preparation of Flexible Shape Memory Intelligent Parts

[0047] Step (1): Mix 6-((4'-cyano-[1,1'-biphenyl]-4-yl)oxy)hexyl acrylate (1.00 g, 2.86 mmol) with 2-acryloylhydrazine-1-carboxamide (1.50 g, 11.61 mmol) in dimethyl sulfoxide and place it on a roller shaker with a rotation speed of 80 rpm to completely dissolve it;

[0048] Step (2): Add diphenyl(2,4,6-trimethylbenzoyl)phosphine oxide (0.04 g, 0.12 mmol) to the solution obtained in Step (1), and also shake it on a roller shaker until TPO is completely dissolved;

[0049] Step (3): Add the photo-polymerizable carbazole liquid crystal cross-linking agent (0.12 g, 0.17 mmol) and acrylic acid (1.10 g, 15.26 mmol) prepared in this example to the solution obtained in Step (2), heat and stir evenly at 100 °C to obtain a transparent printing ink;

[0050] Step (4): The printing ink forms a liquid crystal organic gel part under ultraviolet light irradiation (wavelength 405 nm) of a DLP 3D printer, and the organic solvent inside the liquid crystal organic gel is replaced with water by a solvent replacement method (the replacement time is 7 days).

[0051] Example 2

[0052] (1) Preparation of Photo-Polymerizable Carbazole Liquid Crystal

[0053]

[0054] The intermediate (2) was obtained according to the synthesis steps in Example 1.

[0055] Synthesis of liquid crystal compound (6)

[0056] Prepare a 50 mL two-necked round-bottom flask, add compound 2 (0.50 g, 1.27 mmol) and potassium carbonate (0.49 g, 3.55 mmol), evacuate and replace with argon, keep it under an argon atmosphere, draw DMF (10 mL) with a syringe and inject it, stir and heat to reflux at 100 °C. After 12 h, add compound 5 (5.01 g, 21.34 mmol) and continue stirring for 24 h. After the reaction is completed, add water to precipitate the crude product, extract the remaining solution with dichloromethane, remove the solvent using a rotary evaporator, and purify the obtained crude product by column chromatography. The eluent is PE:DCM = 1:5 - 2:1 (v / v). The liquid crystal compound (6) is a white powder, and the reaction yield is 69%.

[0057] 1 H NMR (600 MHz, DMSO-d6) δ 8.15 (d, J = 8.1 Hz, 2H), 7.80 (s, 2H), 7.74 (d, J = 8.7 Hz, 4H), 7.44 (d, J = 8.1, 1.5 Hz, 2H), 7.04 (d, J = 8.7 Hz, 4H), 5.88–5.79 (m, 2H), 5.77–5.67 (m, 2H), 5.19–5.07 (m, 8H), 4.49 (t, J = 7.2 Hz, 2H), 4.01 (t, J = 6.4 Hz, 4H), 3.88 (t, 8H), 2.33 (t, J = 7.3 Hz, 4H), 1.89–1.82 (m, 2H), 1.78–1.70 (m, 4H), 1.63–1.55 (m, 4H), 1.49–1.40 (m, 4H), 0.93 (t, J = 7.3 Hz, 3H).

[0058] (2) Preparation of flexible shape memory smart components

[0059] The tri-photopolymerizable carbazole liquid crystal prepared by the above process of this example was used as the cross-linking agent, the organic solvent was dimethylformamide, and other operations were substantially the same as those in Example 1, which will not be elaborated here.

[0060] Comparative Example 1

[0061] In this comparative example, poly(ethylene glycol) diacrylate was used instead of the photopolymerizable carbazole liquid crystal as the cross-linking agent, and other operations were substantially the same as those in Example 1, which will not be elaborated here.

[0062] Example 3: Detection and comparison of component performance

[0063] The parts prepared in Examples 1 and 2 of this application were subjected to performance testing and comparison with the parts prepared in Comparative Example 1. Significant differences were shown between Examples 1 and 2 and Comparative Example 1 in terms of mechanical properties. The specific stress-strain test results are as Figure 1 shown. The maximum strain of Example 1 reached 356.15%, and that of Example 2 was 305.21%, much higher than 31.83% of Comparative Example 1; their fracture stresses were 0.99 MPa and 1.14 MPa respectively, which were also significantly better than 0.24 MPa of Comparative Example 1; in terms of elastic modulus, Example 1 was 1.13 MPa and Example 2 was 2.01 MPa, which also showed improvement compared with 0.89 MPa of Comparative Example 1.

[0064] Strain / % Stress / MPa Modulus / MPa Example 1 356.15 0.99 1.13 Example 2 305.21 1.14 2.01 Comparative Example 1 31.83 0.24 0.89

[0065] These performance differences are mainly attributed to the unique structural characteristics of carbazole liquid crystal molecules. The carbazole group has a rigid planar structure, which can enhance the π-π stacking interaction between molecules, promote the formation of a more ordered and dense molecular arrangement during the polymerization of liquid crystal monomers, thereby improving the crosslinking density of the material and the uniformity of internal stress distribution. At the same time, in Example 2, the original "acryloyloxy group" of the liquid crystal monomer was replaced with an "N,N-diallylacetamide" structure. The introduction of the nitrogen alkyl chain enhanced the hydrogen bond interaction and polar interaction between molecular chains, and the lone pair electrons on the nitrogen atom enhanced the intermolecular force between liquid crystal monomers, stabilizing the liquid crystal orientation structure during the photopolymerization process. At the same time, "N,N-diallylacetamide" contains four polymerizable double bonds, which can form a denser three-dimensional crosslinked network during the curing process, which is beneficial to improving the structural stability and mechanical properties. In addition, the parts printed in Examples 1 and 2 also have shape memory and fluorescence visualization functions. As Figure 2 shown, under external thermal stimulation conditions, the material can quickly recover from the deformed state to the initial shape, showing a good reversible shape memory effect, which is suitable for the application requirements of flexible devices and intelligent response systems. At the same time, the material shows a stable and uniform fluorescence emission phenomenon under ultraviolet light irradiation. This fluorescence property comes from the good photoluminescence performance of the carbazole group, and it is easier to form an excited state energy migration channel in the state of molecular ordered arrangement, enhancing the fluorescence intensity and stability. Therefore, Examples 1 and 2 not only have better mechanical properties than Comparative Example 1, but also achieve a breakthrough in multifunctional response ability, and have the potential to be widely used in fields such as intelligent display, soft robots, and information marking.

[0066] The above embodiments are only for illustrating the technical concept and characteristics of the present invention, and their purpose is to enable those who are familiar with this technology to understand the content of the present invention and implement it accordingly, and it should not be used to limit the protection scope of the present invention. Any equivalent transformation or modification made according to the spirit and essence of the present invention should be covered within the protection scope of the present invention.

Claims

1. A formulation for 3D printing shape memory parts based on photopolymerized carbazole liquid crystal, characterized in that: The invention is composed of the following components: a hydrogel monomer, a liquid crystal monomer, a crosslinking agent and a photoinitiator, wherein the crosslinking agent is a photopolymerizable carbazole liquid crystal, and the structure of the photopolymerizable carbazole liquid crystal is shown in the following formula: Wherein, n = 1 to 30; R1 and R2 are selected from substituted or unsubstituted alkyl groups having 1 to 20 carbon atoms, R1 and R2 are the same or different, and both R1 and R2 contain a photopolymerizable terminal group, and the photopolymerizable terminal group is one of the following groups:

2. A formulation for 3D printing shape memory parts based on photopolymerized carbazole liquid crystal according to claim 1, characterized in that: The hydrogel monomer is a mixture of 2-acryloylhydrazide-1-formamide and acrylic acid; And / or, the liquid crystal monomer is 6-((4'-cyano-[1,1'-biphenyl]-4-yl)oxy)hexyl acrylate; And / or, the photoinitiator is diphenyl (2,4,6-trimethylbenzoyl) phosphine oxide.

3. The formula of a 3D printed shape memory product based on photopolymerized carbazole liquid crystal according to claim 2, characterized in that: In the hydrogel monomer, the molar ratio of 2-acryloylhydrazide-1-formamide to acrylic acid is 1:1-23.

4. The formula for 3D printing shape memory parts based on photopolymerized carbazole liquid crystal according to claim 1, characterized in that: The molar ratio of the crosslinking agent to the liquid crystal monomer is 1:10 to 36, and / or, the mass ratio of the cross-linking agent to the hydrogel monomer is 1:10-52, And / or, the mass ratio of the photoinitiator to the hydrogel monomer is 1:25-100.

5. A shape memory component based on photopolymerized carbazole liquid crystal, characterized in that: The formulation described in any one of claims 1 to 4 is prepared by DLP 3D printing.

6. A method for preparing a shape memory component based on photopolymerized carbazole liquid crystal, characterized in that: The following steps are involved: Step (1): mixing the liquid crystal monomer and 2-acryloylhydrazide-1-formamide in an organic solution and dissolving them completely; Step (2): Add the photoinitiator to the solution of step (1) and shake until completely dissolved; Step (3): adding a cross-linking agent and acrylic acid monomer, heating and stirring to obtain a transparent printing ink; Step (4): The printing ink forms a liquid crystal organic gel product under the ultraviolet light of the DLP 3D printer, and the organic solvent inside the liquid crystal organic gel is replaced with water by a solvent replacement method.

7. The method for preparing a shape memory component based on photopolymerized carbazole liquid crystal according to claim 6, characterized in that: The organic solvent is dimethylformamide or dimethyl sulfoxide or a mixture of the two.

8. The method for preparing a shape memory component based on photopolymerized carbazole liquid crystal according to claim 6, characterized in that: The heating temperature in step (3) is 50-150°C.

9. The method for preparing a shape memory component based on photopolymerized carbazole liquid crystal according to claim 6, characterized in that: The wavelength range of the ultraviolet light in step (4) is between 300-450 nm, and the replacement time is 3-15 days.

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