A linear liquid crystalline polymer rich in hydrogen bond donors and a method for its preparation

Abstract

The application discloses a linear liquid crystal polymer rich in hydrogen bond donors and a preparation method thereof, and relates to the technical field of polymer chemical synthesis. The method uses bis[4-[3-(acryloyloxy)propoxy]benzoic acid] (2-methyl-1,4-phenylene) ester (RM257) and dithiothreitol (DTT) as raw materials, reacts according to a certain molar ratio to prepare a linear liquid crystal polymer precursor, and then performs end capping on the linear liquid crystal polymer precursor by using a monomercapto end capping agent to synthesize the linear liquid crystal polymer rich in hydrogen bond donors. It is found that the arrangement mode of the hydrogen bond in the target polymer depends on the molecular structure of the end group, and the relationship between the arrangement mode and the structure and properties of the target polymer is indicated. The linear liquid crystal polymer rich in hydrogen bond donors has good universality, and can be introduced into a non-covalent interaction in a liquid crystal elastomer reinforcing system as a reinforcing phase to effectively improve the mechanical properties of the material.

Description

Technical Field

[0001] This invention belongs to the field of polymer chemical synthesis technology, and specifically relates to a linear liquid crystal polymer rich in hydrogen bond donors and its preparation method. Background Technology

[0002] Liquid crystal elastomers are polymeric materials that combine the ordered nature of liquid crystal molecules with the entropic elasticity of rubber. Due to their unique reversible phase transitions and stimulus-responsiveness, they have become a research hotspot and focus in flexible smart materials, showing broad application prospects in fields such as artificial muscles, soft robots, smart fabrics, and damping devices. However, existing liquid crystal elastomer materials generally suffer from a bottleneck in the industry, where it is difficult to simultaneously achieve optimal mechanical properties, actuation properties, and dissipation properties. Obtaining high dissipation properties often comes at the cost of sacrificing the material's mechanical and actuation properties, severely restricting their engineering applications in real-world situations.

[0003] In recent years, through molecular structure design and process technology optimization, researchers have successfully prepared various liquid crystal elastomers with excellent properties, such as high-damping polycrystalline semi-interpenetrating network liquid crystal elastomers, spider silk-inspired multi-scale liquid crystal elastomer fibers, high-performance liquid crystal elastomers with core-shell structures, and carbon-doped composite liquid crystal elastomers. Based on these significant advances in liquid crystal elastomers, the design of semi-interpenetrating network structures, as a typical example of molecular homology reinforcement strategies, holds promise for solving the trade-off between mechanical properties, driving performance, and dissipation performance in liquid crystal elastomers. Specifically, introducing linear liquid crystal polymers as reinforcing phases into cross-linked liquid crystal elastomer matrices can significantly improve the mechanical and dissipation properties of liquid crystal elastomers without sacrificing driving performance through additional non-covalent interactions.

[0004] Most existing linear liquid crystal polymers employ flexible chain extenders without hydrogen bond donors to polymerize reactive liquid crystal monomers. Their reinforcing effect primarily relies on relatively weak non-covalent forces such as physical entanglement, intermolecular π-π stacking, and dipole-dipole interactions, offering limited improvement to the macroscopic properties of liquid crystal elastomers. Furthermore, the lack of high-density, tunable hydrogen bond donor sites within the molecular chain prevents efficient energy dissipation and superior mechanical properties through reversible breakage and recombination of dynamic hydrogen bonds. Therefore, developing a linear liquid crystal polymer rich in hydrogen bond donors, with a simple preparation process and customizable controllability, has become a core technological challenge urgently needing to be addressed in this field. Summary of the Invention

[0005] The purpose of this invention is to overcome the above-mentioned shortcomings of the prior art, and to provide a linear liquid crystal polymer rich in hydrogen bond donors and its preparation method, addressing the limitations of the prior art and the usage requirements in special application scenarios.

[0006] The technical solution of this invention is:

[0007] This method uses bis[4-[3-(acryloyloxy)propoxy]benzoic acid](2-methyl-1,4-phenylene) ester (RM257) and dithiothreitol (DTT) as raw materials to prepare a linear liquid crystal polymer precursor by reacting them in a certain molar ratio. The precursor is then capped with monothiol end-capping agents (ethanethiol, 2-mercaptoethanol, mercaptoacetic acid, and 6-mercapto-1-hexanol) to synthesize the hydrogen-bond-rich linear liquid crystal polymer. It was found that the arrangement of hydrogen bonds within the target polymer depends on the molecular structure of its end groups, and the relationship between this arrangement and the structure and properties of the target polymer was identified. The hydrogen-bond-rich linear liquid crystal polymer exhibits good versatility and can be used as a reinforcing phase to introduce non-covalent interactions within liquid crystal elastomer reinforcement systems, effectively improving the mechanical properties of the material.

[0008] A linear liquid crystal polymer rich in hydrogen bond donors is disclosed. The polymer precursor is formed by polymerizing bis[4-[3-(acryloyloxy)propoxy]benzoic acid](2-methyl-1,4-phenylene) ester (CAS: 174063-87-7) and dithiothreitol (CAS: 3483-12-3), a chain extender with two hydroxyl groups on the same side. The target polymer is then prepared by modifying the polymer precursor with a monothiol end-capping agent. The monothiol end-capping agent regulates the arrangement of hydrogen bonds in the polymer chain through its end-group structure, thereby regulating the liquid crystal phase transition temperature.

[0009] The monothiol capping agent includes ethanethiol, 2-mercaptoethanol, mercaptoacetic acid, or 6-mercapto-1-hexanol.

[0010] Furthermore, the polymer chain of the target polymer precursor has acrylate groups at both ends and has a certain reactivity with thiol groups.

[0011] A linear liquid crystal polymer rich in hydrogen bond donors and its preparation method, comprising the following steps:

[0012] Step 1: Dissolve 40 mmol of bis[4-[3-(acryloyloxy)propoxy]benzoic acid](2-methyl-1,4-phenylene) ester and 36 mmol of dithiothreitol in 100 mL of ultra-dry dichloromethane and stir at room temperature for 30 min to obtain two uniformly dispersed monomer solutions. The heat generated during the dissolution process is negligible.

[0013] Step 2: Add 790 mL of the alkaline catalyst di-n-propylamine to the monomer solution containing bis[4-[3-(acryloyloxy)propoxy]benzoic acid](2-methyl-1,4-phenylene) ester in Step 1, stir in an ice bath for 20 min, purge dissolved oxygen with nitrogen using a bubbling method, and slowly add the monomer solution containing dithiothreitol dropwise through a constant pressure dropping funnel in an ice bath. React for 24 h to obtain a clear, transparent, slightly viscous polymer solution.

[0014] Step 3: Slowly pour the polymer solution described in Step 2 into 300 mL of methanol. The milky white polymer precipitates and settles at the bottom of the glass container. Let it stand at room temperature for 15 min. Use a dropper to remove the milky white supernatant, then add 300 mL of methanol to continue washing. Repeat the above operation 4-5 times until the washing solution is clear.

[0015] Step 4: Transfer the moist, milky-white polymer described in Step 3 to a vacuum oven and dry it at 40 °C for 8 h to obtain the polymer precursor described in claim 1;

[0016] Step 5: Dissolve the polymer precursor described in Step 4 in 200 mL of ultra-dry dichloromethane. After stirring evenly, add the catalyst 1,8-diazabicyclo[5.4.0]undec-7-ene and the monothiol end-capping agent in a molar ratio of 5:4 to the solution in which the polymer precursor is dissolved. React at room temperature for 12 h to obtain a pale yellow polymer solution.

[0017] Step 6: Slowly pour the pale yellow polymer solution described in Step 5 into 300 mL of methanol. The milky white polymer precipitates out and settles at the bottom of the glass container. Repeat the washing operation described in Step 3 until the washing solution is clear.

[0018] Step 7: Transfer the moistened milky white polymer from Step 6 to a vacuum oven and dry at 40 °C for 8 h to obtain the linear liquid crystal polymer rich in hydrogen bond donors as described in claim 1.

[0019] Furthermore, the monothiol capping agent in step 5 is one of ethanethiol, 2-mercaptoethanol, mercaptoacetic acid, or 6-mercapto-1-hexanol.

[0020] Furthermore, the property differences between the different linear liquid crystal polymers in step 7 depend on the end group structure of the polymer chain.

[0021] Use of a linear liquid crystal polymer rich in hydrogen bond donors, the polymer being used to enhance the mechanical properties of liquid crystal elastomers, such as fracture stress, toughness, elongation at break and Young's modulus, wherein the polymer content in the liquid crystal elastomer is 20 wt%-50 wt%.

[0022] Advantages and beneficial effects of the present invention:

[0023] 1. The linear liquid crystal polymer prepared by the present invention is a novel linear liquid crystal polymer with a large number of hydroxyl groups on the same side as hydrogen bond donors, and it is also a linear liquid crystal polymer suitable for different application scenarios;

[0024] 2. The method for preparing the linear liquid crystal polymer described in this invention is a synthesis scheme with characteristics of high reproducibility, strong universality, and high yield;

[0025] 3. The linear liquid crystal polymer prepared by the present invention can be used to adjust the arrangement of multiple hydrogen bonds in the system by adjusting the end group structure at both ends of the polymer chain, thereby controlling its liquid crystal phase transition temperature (which can be adjusted in the range of 106.6°C to 134.7°C), melting point and crystallization behavior and other physicochemical properties.

[0026] 4. The linear liquid crystal polymer prepared in this invention can easily and efficiently form a semi-interpenetrating structure with traditional cross-linked liquid crystal network prepolymers through solution impregnation or mechanical blending. This allows for effective modification and reinforcement of liquid crystal elastomer materials within a wide range of preparation conditions. Taking EM-LLCP as an example, when its content is 33%, the semi-interpenetrating network liquid crystal elastomer fiber exhibits a fracture stress of 50.6 MPa (an increase of 45%), a toughness of 42.8 MJ m⁻³ (an increase of 176%), and an elongation at break of 204.5% (an increase of 69%). Attached Figure Description

[0027] Figure 1 The present invention provides synthetic routes for four linear liquid crystal polymers rich in hydrogen bond donors prepared in this invention.

[0028] Figure 2 P-LLCP, a linear liquid crystal polymer precursor 1 H NMR spectrum (400 MHz, d6-DMSO).

[0029] Figure 3 For linear liquid crystal polymer EM-LLCP 1 H NMR spectrum (400 MHz, d6-DMSO).

[0030] Figure 4 For linear liquid crystal polymer ME-LLCP 1 H NMR spectrum (400 MHz, Chloroform-d).

[0031] Figure 5 For linear liquid crystal polymers MAA-LLCP 1 H NMR spectrum (400 MHz, d6-DMSO).

[0032] Figure 6 For linear liquid crystal polymer MCH-LLCP 1 H NMR spectrum (400 MHz, Chloroform-d).

[0033] Figure 7 This is the GPC spectrum of the linear liquid crystal polymer precursor P-LLCP.

[0034] Figure 8 FTIR plots for EM-LLCP, ME-LLCP, MAA-LLCP, and MCH-LLCP.

[0035] Figure 9 2D-WAXS plots, 1D-WAXS curves, and 1D-SAXS curves for EM-LLCP, ME-LLCP, MAA-LLCP, and MCH-LLCP

[0036] Figure 10 POM plots of EM-LLCP, ME-LLCP, MAA-LLCP and MCH-LLCP at different temperatures.

[0037] Figure 11 Stress-strain curves of semi-interpenetrating network liquid crystal elastomer fibers obtained by melt spinning under different EM-LLCP inputs, and corresponding comparison diagrams of fracture stress, elongation at break and toughness. Detailed Implementation

[0038] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be described in detail below with reference to the accompanying drawings.

[0039] Example 1:

[0040] A method for preparing the linear liquid crystal polymer rich in hydrogen bond donors as described in claim 1, comprising the following steps:

[0041] Step 1: Dissolve 23.544 g of bis[4-[3-(acryloyloxy)propoxy]benzoic acid](2-methyl-1,4-phenylene) ester (40 mmol) and 5.553 g of dithiothreitol in 100 mL of ultra-dry dichloromethane, respectively, and stir at room temperature for 20 min to obtain two uniformly dispersed monomer solutions. The volume and temperature changes of the solution due to the dissolution of the solute are negligible.

[0042] Step 2: 790 mL (5.76 mmol, 2 wt% of total reagent mass) of di-n-propylamine was added dropwise to a monomer solution containing bis[4-[3-(acryloyloxy)propoxy]benzoic acid](2-methyl-1,4-phenylene) ester under ice bath conditions. The compound was stirred for 30 min at 0°C in air, and nitrogen gas was bubbled through to remove dissolved oxygen. Then, 100 mL of a monomer solution containing dithiothreitol was slowly added dropwise to the above solution through a constant pressure dropping funnel. The reaction was allowed to proceed at room temperature for 24 h, yielding a clear, transparent, slightly viscous polymer solution, labeled as P-LLCP solution.

[0043] Step 3: Slowly pour 200 mL of P-LLCP solution into 300 mL of methanol to precipitate the polymer precursor P-LLCP. Let it stand at room temperature for 15 min. Use a dropper to remove the milky white supernatant from the suspension. Wash the precipitated solid repeatedly with methanol 4-5 times until the washing solution is clear to obtain slightly viscous wet P-LLCP.

[0044] Step 4: Transfer the wet P-LLCP to a vacuum oven and dry at 40 °C for 8 h. The resulting P-LLCP is a blocky white solid with high overall hardness;

[0045] Step 5: Dissolve 26.983 g of P-LLCP in 200 mL of ultra-dry dichloromethane, then add 0.994 g (1184 mL, 16 mmol) of ethanethiol and 3.045 g (2.988 mL, 20 mmol) of 1,8-diazabicyclo[5.4.0]undec-7-ene. The resulting mixture was sonicated at room temperature for 15 min, then reacted at room temperature for 12 h. The solute in the resulting pale yellow viscous polymer solution was the target linear liquid crystal polymer EM-LLCP.

[0046] Step 6: Slowly pour the dichloromethane solution of EM-LLCP into 300 mL of methanol. A large amount of milky white flocculent precipitates and accumulates at the bottom of the glass container. Use a dropper to remove the milky white supernatant from the suspension. Wash the precipitated solid repeatedly with methanol 4-5 times until the washing liquid is clear to obtain wet EM-LLCP.

[0047] Step 7: Vacuum dry the wet EM-LLCP (40 °C) for 8 h to obtain white solid EM-LLCP.

[0048] Figure 1 The diagram shows the synthetic route for the linear liquid crystal polymer EM-LLCP, which is rich in hydrogen bond donors. Figure 2 As shown, the hydrogen nuclear magnetic resonance spectrum (NMR) was used. 1The product P-LLCP was characterized by ¹H NMR, revealing that acrylate-terminated P-LLCP was successfully synthesized. End-group analysis showed that its number-average molecular weight M0 was [missing value]. n And aggregation degree X n Approximately 10200 g mol -1 And 13. For example Figure 3 As shown, using 1 HNMR confirmed the successful synthesis of a linear liquid crystal polymer EM-LLCP rich in hydrogen bond donors, with a number-average molecular weight M n And aggregation degree X n Approximately 11000 g mol -1 And 14.

[0049] Example 2:

[0050] A method for preparing the linear liquid crystal polymer rich in hydrogen bond donors as described in claim 1, comprising the following steps:

[0051] Step 1: Dissolve 23.544 g of bis[4-[3-(acryloyloxy)propoxy]benzoic acid](2-methyl-1,4-phenylene) ester (40 mmol) and 5.553 g of dithiothreitol in 100 mL of ultra-dry dichloromethane, respectively, and stir at room temperature for 20 min to obtain two uniformly dispersed monomer solutions. The volume and temperature changes of the solution due to the dissolution of the solute are negligible.

[0052] Step 2: 790 mL (5.76 mmol, 2 wt% of total reagent mass) of di-n-propylamine was added dropwise to a monomer solution containing bis[4-[3-(acryloyloxy)propoxy]benzoic acid](2-methyl-1,4-phenylene) ester under ice bath conditions. The compound was stirred for 30 min at 0°C in air, and nitrogen gas was bubbled through to remove dissolved oxygen. Then, 100 mL of a monomer solution containing dithiothreitol was slowly added dropwise to the above solution through a constant pressure dropping funnel. The reaction was allowed to proceed at room temperature for 24 h, yielding a clear, transparent, slightly viscous polymer solution, labeled as P-LLCP solution.

[0053] Step 3: Slowly pour 200 mL of P-LLCP solution into 300 mL of methanol to precipitate the polymer precursor P-LLCP. Let it stand at room temperature for 15 min. Use a dropper to remove the milky white supernatant from the suspension. Wash the precipitated solid repeatedly with methanol 4-5 times until the washing solution is clear to obtain slightly viscous wet P-LLCP.

[0054] Step 4: Transfer the wet P-LLCP to a vacuum oven and dry at 40 °C for 8 h. The resulting P-LLCP is a blocky white solid with high overall hardness;

[0055] Step 5: Dissolve 26.983 g of P-LLCP in 200 mL of ultra-dry dichloromethane, then add 1.250 g (1121 mL, 16 mmol) of 2-mercaptoethanol and 3.045 g (2.988 mL, 20 mmol) of 1,8-diazabicyclo[5.4.0]undec-7-ene. The resulting mixture was sonicated at room temperature for 15 min, then reacted at room temperature for 12 h. The solute in the resulting pale yellow viscous polymer solution was the target linear liquid crystal polymer ME-LLCP.

[0056] Step 6: Slowly pour the dichloromethane solution of ME-LLCP into 300 mL of methanol. A large amount of milky white flocculent precipitates and accumulates at the bottom of the glass container. Use a dropper to remove the milky white supernatant from the suspension. Wash the precipitated solid repeatedly with methanol 4-5 times until the washing liquid is clear to obtain wet ME-LLCP.

[0057] Step 7: Vacuum dry the wet ME-LLCP (40 °C) for 8 h to obtain white solid EM-LLCP.

[0058] Figure 4 The image shows ME-LLCP, a linear liquid crystal polymer rich in hydrogen bond donors. 1 The 1H NMR spectrum, as determined by end-group analysis, shows that its number-average molecular weight M n And aggregation degree X n Approximately 11100 g mol -1 And 14.

[0059] Example 3:

[0060] A method for preparing the linear liquid crystal polymer rich in hydrogen bond donors as described in claim 1, comprising the following steps:

[0061] Step 1: Dissolve 23.544 g of bis[4-[3-(acryloyloxy)propoxy]benzoic acid](2-methyl-1,4-phenylene) ester (40 mmol) and 5.553 g of dithiothreitol in 100 mL of ultra-dry dichloromethane, respectively, and stir at room temperature for 20 min to obtain two uniformly dispersed monomer solutions. The volume and temperature changes of the solution due to the dissolution of the solute are negligible.

[0062] Step 2: 790 mL (5.76 mmol, 2 wt% of total reagent mass) of di-n-propylamine was added dropwise to a monomer solution containing bis[4-[3-(acryloyloxy)propoxy]benzoic acid](2-methyl-1,4-phenylene) ester under ice bath conditions. The compound was stirred for 30 min at 0°C in air, and nitrogen gas was bubbled through to remove dissolved oxygen. Then, 100 mL of a monomer solution containing dithiothreitol was slowly added dropwise to the above solution through a constant pressure dropping funnel. The reaction was allowed to proceed at room temperature for 24 h, yielding a clear, transparent, slightly viscous polymer solution, labeled as P-LLCP solution.

[0063] Step 3: Slowly pour 200 mL of P-LLCP solution into 300 mL of methanol to precipitate the polymer precursor P-LLCP. Let it stand at room temperature for 15 min. Use a dropper to remove the milky white supernatant from the suspension. Wash the precipitated solid repeatedly with methanol 4-5 times until the washing solution is clear to obtain slightly viscous wet P-LLCP.

[0064] Step 4: Transfer the wet P-LLCP to a vacuum oven and dry at 40 °C for 8 h. The resulting P-LLCP is a blocky white solid with high overall hardness;

[0065] Step 5: Dissolve 26.983 g of P-LLCP in 200 mL of ultra-dry dichloromethane, then add 1.474 g (1116 mL, 16 mmol) of mercaptoacetic acid and 3.045 g (2.988 mL, 20 mmol) of 1,8-diazabicyclo[5.4.0]undec-7-ene. The resulting mixture is sonicated at room temperature for 15 min, reacted at room temperature for 3 h, and then slowly acidified with 5 mL of concentrated hydrochloric acid (36-38% by mass) until the pH value is less than 5. The solute in the resulting viscous solution is the target linear liquid crystal polymer MAA-LLCP.

[0066] Step 6: Slowly pour the dichloromethane solution of MAA-LLCP into 300 mL of methanol. A large amount of milky white flocculent precipitates and accumulates at the bottom of the glass container. Use a dropper to remove the milky white supernatant from the suspension. Wash the precipitated solid repeatedly with methanol 4-5 times until the washing liquid is clear to obtain wet MAA-LLCP.

[0067] Step 7: Vacuum dry the wet MAA-LLCP (40 °C) for 8 h to obtain white solid MAA-LLCP.

[0068] Figure 5 The image shows the linear liquid crystal polymer MAA-LLCP rich in hydrogen bond donors. 1 The 1H NMR spectrum, as determined by end-group analysis, shows that its number-average molecular weight Mn And aggregation degree X n Approximately 11200 g mol -1 And 14.

[0069] Example 4:

[0070] A method for preparing the linear liquid crystal polymer rich in hydrogen bond donors as described in claim 1, comprising the following steps:

[0071] Step 1: Dissolve 23.544 g of bis[4-[3-(acryloyloxy)propoxy]benzoic acid](2-methyl-1,4-phenylene) ester (40 mmol) and 5.553 g of dithiothreitol in 100 mL of ultra-dry dichloromethane, respectively, and stir at room temperature for 20 min to obtain two uniformly dispersed monomer solutions. The volume and temperature changes of the solution due to the dissolution of the solute are negligible.

[0072] Step 2: 790 mL (5.76 mmol, 2 wt% of total reagent mass) of di-n-propylamine was added dropwise to a monomer solution containing bis[4-[3-(acryloyloxy)propoxy]benzoic acid](2-methyl-1,4-phenylene) ester under ice bath conditions. The compound was stirred for 30 min at 0°C in air, and nitrogen gas was bubbled through to remove dissolved oxygen. Then, 100 mL of a monomer solution containing dithiothreitol was slowly added dropwise to the above solution through a constant pressure dropping funnel. The reaction was allowed to proceed at room temperature for 24 h, yielding a clear, transparent, slightly viscous polymer solution, labeled as P-LLCP solution.

[0073] Step 3: Slowly pour 200 mL of P-LLCP solution into 300 mL of methanol to precipitate the polymer precursor P-LLCP. Let it stand at room temperature for 15 min. Use a dropper to remove the milky white supernatant from the suspension. Wash the precipitated solid repeatedly with methanol 4-5 times until the washing solution is clear to obtain slightly viscous wet P-LLCP.

[0074] Step 4: Transfer the wet P-LLCP to a vacuum oven and dry at 40 °C for 8 h. The resulting P-LLCP is a blocky white solid with high overall hardness;

[0075] Step 5: Dissolve 26.983 g of P-LLCP in 200 mL of ultra-dry dichloromethane, then add 2.148 g (2189 mL, 16 mmol) of 6-mercapto-1-hexanol and 3.045 g (2.988 mL, 20 mmol) of 1,8-diazabicyclo[5.4.0]undec-7-ene. The resulting mixture was sonicated at room temperature for 15 min, then reacted at room temperature for 12 h. The solute in the resulting pale yellow viscous polymer solution was the target linear liquid crystal polymer MCH-LLCP.

[0076] Step 6: Slowly pour the dichloromethane solution of MCH-LLCP into 300 mL of methanol. A large amount of milky white flocculent precipitates and accumulates at the bottom of the glass container. Use a dropper to remove the milky white supernatant from the suspension. Wash the precipitated solid repeatedly with methanol 4-5 times until the washing liquid is clear to obtain wet MCH-LLCP.

[0077] Step 7: Vacuum dry the wet MCH-LLCP (40 °C) for 8 h to obtain white solid MCH-LLCP.

[0078] Figure 6 The image shows the linear liquid crystal polymer MCH-LLCP rich in hydrogen bond donors. 1 The 1H NMR spectrum, as determined by end-group analysis, shows that its number-average molecular weight M n And aggregation degree X n Approximately 12000 g mol -1 And 15. Combined Figure 3-6 It can be seen that the number-average molecular weight and degree of polymerization of the four hydrogen bond donor-rich linear liquid crystal polymers EM-LLCP, ME-LLCP, MAA-LLCP, and MCH-LLCP prepared in this invention are basically consistent, and are also similar to... Figure 2 The polymer precursors P-LLCP shown exhibit little difference, indicating that the differences between samples originate from the end-group structures of each polymer chain. For example... Figure 7 As shown, the absolute number-average molecular weight of the polymer precursor P-LLCP, measured by GPC, is 9400 Da, and the molecular weight distribution index is 1.635, corroborating the aforementioned reliable conclusions. Figure 8 As shown, the four linear liquid crystal polymers rich in hydrogen bond donors prepared in this invention exhibit performance at 3200-3600 cm⁻¹. -1 Broad absorption peaks representing hydrogen-bonded hydroxyl groups were observed at all locations, in the range of 1450-1600 cm⁻¹. -1 An absorption peak for the C-C vibration of the benzene ring skeleton appears at 2800 cm⁻¹. -1 An absorption peak for the CH stretching vibration of the benzene ring appears nearby, at 1700 cm⁻¹. -1 A sharp, strong absorption peak of C=O stretching vibration appears nearby. The inset shows the wavenumber variation of hydrogen-bonded hydroxyl groups in the four samples. The wavenumber of the characteristic peak of hydrogen-bonded hydroxyl groups in ME-LLCP is significantly lower than that of the other three LLCPs, indicating that more and stronger hydrogen bonds are formed between its molecules, which is conducive to driving the orderly arrangement of molecular chains and forming local crystallization regions. Other factors such as insufficient polarity of end genes, steric hindrance, more hydrogen bond acceptors, or high flexibility make it difficult to promote crystallization. Figure 9The results of WAXS and SAXS characterization of the four samples are shown. All samples show an unoriented diffraction ring, while ME-LLCP also shows a small diffraction ring with a weaker signal within the large diffraction ring. Figure 9 A). Subsequently, a one-dimensional X-ray diffraction curve is obtained by ring integration of the two-dimensional WAXS image (A). Figure 9 B), four samples at q = 1.36 Å -1 A typical amorphous characteristic peak appears near (2θ ≈ 20°). Correspondingly, the 1D-SAXS curve ( Figure 9 C) indicates that only ME-LLCP at q = 0.40 Å -1 The presence of characteristic peaks corresponding to small diffraction rings in the nearby 2D WAXS image indicates the presence of localized chain segment crystallization induced by hydrogen bonds within the structure. This is attributed to the stronger polarity of the short-chain hydroxyl groups in ME-LLCP compared to other end groups, resulting in hydrogen bonds with higher directionality and strength. These bonds effectively promote the ordered arrangement of molecular chains, thereby increasing crystallinity.

[0079] Example 5:

[0080] The method for preparing the linear liquid crystal polymer rich in hydrogen bond donors differs from that in Examples 1-4 in that other monothiol end-capping agents are used to replace any one of ethanethiol, 2-hydroxyethanol, mercaptoacetic acid, and 6-mercapto-1-hexanol, such as o-hydroxythiophenol (CAS: 1121-24-0), m-hydroxythiophenol (CAS: 40248-84-8), p-hydroxythiophenol (CAS: 637-89-9), o-carboxythiophenol (CAS: 147-93-3), and m-carboxythiophenol (CAS: 40248-84-8), etc. The results are the same as in Examples 1-4.

[0081] Figure 10The image shows POM snapshots of four samples within the range of 25-150 °C. All samples exhibited significant birefringence at room temperature, displaying typical characteristics of a liquid crystal phase. Subsequently, the temperature was increased to 150 °C at a heating rate of 30 °C min⁻¹. The birefringence gradually intensified within the field of view. This is because the hydrogen-bonded hydroxyl groups gradually dissociated into free hydroxyl groups as the temperature increased, enhancing the molecular chain mobility and facilitating the formation of a multi-domain liquid crystal phase within the system. However, the birefringence disappeared at temperatures of 115.7 °C (EM-LLCP), 134.7 °C (ME-LLCP), 128.8 °C (MAA-LLCP), and 124.5 °C (MCH-LLCP), respectively, marking the completion of the anisotropic-isotropic phase transition. The birefringence phenomenon reappeared during constant-rate cooling (30 °C min⁻¹), with corresponding phase transition temperatures of 106.6 °C (EM-LLCP), 128.9 °C (ME-LLCP), 121.7 °C (MAA-LLCP), and 115.6 °C (MCH-LLCP). This result further confirms, through thermally induced phase transition behavior, that the end-group structure can influence the physicochemical properties of the target polymer by modulating the arrangement of multiple hydrogen bonds. Figure 11 As shown, taking EM-LLCP as an example, its introduction into cross-linked network liquid crystal elastomer fibers was verified to enhance and toughen its mechanical properties. Compared to the mechanical properties of single-network LCEAMFs (EM-LLCP content 0%) (fracture stress 34.8 MPa, elongation at break 121.1%, elastic modulus 2.5 MPa, toughness 15.5 MJ / m²), the results demonstrate the superior performance of EM-LLCP. -3 When the EM-LLCP content is 33%, the hydroxyl groups on the same side of the linear chain form hydrogen bonds with the ester groups or hydroxyl groups of adjacent chains in the crosslinked network. This not only enhances the fiber's fracture stress (50.6 MPa) and elastic modulus (21.6 MPa) through hydrogen bond-induced crystallization, but also dissipates additional energy during stretching through the reversible breakage of hydrogen bonds, resulting in increased toughness (42.8 MJ / m²). -3 The tensile stress (83.6 MPa) and elongation at break (204.5%) were significantly improved when the EM-LLCP content was 50%. Although the tensile stress (83.6 MPa) and elastic modulus (89.8 MPa) of the semi-interpenetrating network liquid crystal elastomer fiber were significantly increased, its elongation at break (59.1%) and toughness (17.0 MJ / m²) remained relatively low. -3The hydrogen bond concentration (LLCP) decreases sharply, mainly because excessive hydrogen bond accumulation hinders the relative slippage of molecular chains and induces phase separation of linear chains, causing the fiber to lose its rubbery behavior and exhibit characteristics of a crystalline polymer. While it is not as suitable for dynamically loaded artificial muscles as EM-LLCP at 33%, it has potential applications in the field of statically supported biomimetic scaffolds. Therefore, the hydrogen bond-rich linear liquid crystal polymer prepared in this invention can be customized according to actual needs and objectives, and has broad application value in the field of functional polymer materials.

[0082] In addition, those skilled in the art can make other changes based on the technical solution of this invention, such as modifications, equivalent substitutions and improvements. All changes made based on the technical solution of this invention should be included within the scope of protection of this technical solution.

Claims

1. A linear liquid crystal polymer rich in hydrogen bond donors, characterized in that, The target polymer precursor is formed by polymerizing bis[4-[3-(acryloyloxy)propoxy]benzoic acid](2-methyl-1,4-phenylene) ester and dithiothreitol, a chain extender with two hydroxyl groups on the same side. The target polymer is then prepared by modifying the polymer precursor with a monothiol end-capping agent. The monothiol end-capping agent regulates the arrangement of hydrogen bonds in the polymer chain through its end-group structure, thereby regulating the liquid crystal phase transition temperature. The monothiol capping agent includes ethanethiol, 2-mercaptoethanol, mercaptoacetic acid, or 6-mercapto-1-hexanol.

2. The linear liquid crystal polymer rich in hydrogen bond donors according to claim 1, characterized in that, The polymer precursor of the target polymer has acrylate groups at both ends of its polymer chain and has a certain reactivity with thiol groups.

3. A method for preparing a linear liquid crystal polymer rich in hydrogen bond donors as described in claim 1 or 2, comprising the following steps: Step 1: Dissolve 40 mmol of bis[4-[3-(acryloyloxy)propoxy]benzoic acid](2-methyl-1,4-phenylene) ester and 36 mmol of dithiothreitol in 100 mL of ultra-dry dichloromethane and stir at room temperature for 30 min to obtain two uniformly dispersed monomer solutions. Step 2: Add 790 μL of the alkaline catalyst di-n-propylamine to the monomer solution containing bis[4-[3-(acryloyloxy)propoxy]benzoic acid](2-methyl-1,4-phenylene) ester in Step 1, stir in an ice bath for 20 min, purge dissolved oxygen with nitrogen using a bubbling method, and slowly add the monomer solution containing dithiothreitol dropwise through a constant pressure dropping funnel in an ice bath. React for 24 h to obtain a clear, transparent, slightly viscous polymer solution. Step 3: Slowly pour the polymer solution described in Step 2 into 300 mL of methanol. The milky white polymer precipitates and settles at the bottom of the glass container. Let it stand at room temperature for 15 min. Use a dropper to remove the milky white supernatant, then add 300 mL of methanol to continue washing. Repeat the above operation 4-5 times until the washing solution is clear. Step 4: Transfer the moist, milky-white polymer described in Step 3 to a vacuum oven and dry it at 40 °C for 8 h to obtain the polymer precursor described in claim 1; Step 5: Dissolve the polymer precursor described in Step 4 in 200 mL of ultra-dry dichloromethane, stir evenly, and then add the catalyst 1,8-diazabicyclo[5.4.0]undec-7-ene and the monothiol end-capping agent in a molar ratio of 5:4 to the solution in which the polymer precursor is dissolved. React at room temperature for 12 h to obtain a pale yellow polymer solution. Step 6: Slowly pour the pale yellow polymer solution described in Step 5 into 300 mL of methanol. The milky white polymer precipitates out and settles at the bottom of the glass container. Repeat the washing operation described in Step 3 until the washing solution is clear. Step 7: Transfer the moistened milky white polymer from Step 6 to a vacuum oven and dry at 40 °C for 8 h to obtain the linear liquid crystal polymer rich in hydrogen bond donors as described in claim 1.

4. The method for preparing the linear liquid crystal polymer rich in hydrogen bond donors according to claim 3, characterized in that, The monothiol capping agent is one of ethanethiol, 2-mercaptoethanol, mercaptoacetic acid, and 6-mercapto-1-hexanol.

5. The method for preparing the linear liquid crystal polymer rich in hydrogen bond donors according to claim 3, characterized in that, The differences in properties between different linear liquid crystal polymers depend on the end group structure at both ends of the polymer chain.

6. Use of the hydrogen-bonded linear liquid crystal polymer according to claim 1 or 2, characterized in that, The polymer is used to enhance the fracture stress, toughness, elongation at break and Young's modulus of the liquid crystal elastomer, and the content of the polymer in the liquid crystal elastomer is 20 wt%-50 wt%.

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