A bipolar group acrylate polymer-based dielectric elastomer material and a method for preparing the same

Abstract

The application discloses a bipolar group acrylate polymer-based dielectric elastomer material and a preparation method thereof, and belongs to the technical field of polymer synthesis. The method comprises the following steps: uniformly mixing hydroxybutyl acrylate and dichloromethane, adding organic acid and acylation catalyst, stirring and reacting, and obtaining a hydroxybutyl acrylate-based diester monomer after purification; then adding a crosslinking agent and a photoinitiator, uniformly mixing, and obtaining the bipolar group acrylate polymer-based dielectric elastomer material after solidification and crosslinking under ultraviolet light irradiation. The bipolar group acrylate polymer-based dielectric elastomer material is prepared by taking hydroxybutyl acrylate as a dielectric elastomer matrix, performing esterification reaction on the dielectric elastomer matrix with organic acid, and then adding a crosslinking agent to prepare a diester-based dielectric elastomer film. The bipolar group acrylate polymer-based dielectric elastomer material solves the problems of high elastic modulus and low dielectric constant, and improves the mechanical properties, driving performance and dielectric properties of the bipolar group acrylate polymer-based dielectric elastomer material.

Description

Technical Field

[0001] This invention belongs to the field of polymer synthesis technology, specifically relating to a bipolar group acrylate polymer-based dielectric elastomer material and its preparation method. Background Technology

[0002] Electroactive polymers (EAPs) are smart materials that can undergo significant deformation upon electrical stimulation. Since the early 1990s, EAPs have attracted considerable attention from the scientific community due to their excellent deformation capabilities. Because EAPs share similarities with biological muscle tissue, they are also known as "artificial muscles." Compared to traditional piezoelectric materials, EAPs possess greater strain capacity, are lightweight, have high actuation efficiency, good shock resistance, and unique electrical and mechanical properties, making them one of the most promising biomimetic materials. Based on their mechanism of action, EAPs can be divided into two categories: Coulomb force-driven electronic EAPs and ion diffusion-migrating driven ionic EAPs. Electronic EAPs include all-organic composites (AOCs), dielectric EAPs (DEAPs), electrostrictive grafted elastomers (ESGEs), electrostrictive films (ESPs), electroviscoelastic polymers (EVEMs), ferroelectric polymers (FEPs), and liquid crystal elastomers (LCEs), among others. Ionic EAPs include carbon nanotubes (CNTs), conductive polymers (CP), electrorheological fluids (ERF), ionomer gels (IPG), and ionomer-based metal composites (IPMC). Electronic EAPs, under an applied electric field, induce electrostriction, electrostatic, piezoelectric, and ferroelectric effects through Coulomb forces, resulting in induced displacement under a DC electric field. However, to achieve a certain level of electrostriction, electronic EAPs require a high excitation electric field (>100 V / μm), which approaches the material's breakdown electric field. Ionic EAPs, composed of two electrodes and an electrolyte, can be excited at lower voltages (1–2 V) due to ion migration or dispersion, thus inducing bending displacement. The disadvantages of these EAP materials are the requirement for a certain degree of wettability and the difficulty in ensuring stable induced displacement under DC excitation (except for conductive polymers).

[0003] Since the early 1990s, 3M Corporation of the United States has launched a series of VHBs (Vibrating Hard Handy-Handed Machines). TMPolyacrylate elastomers have inspired researchers' enthusiasm for dielectric elastomers. Dielectric elastomers (DEs) are a new type of electronic EAP. They deform when an external electric field is applied and return to their original shape when the field is removed. This process generates stress and strain while simultaneously converting energy, transforming electrical energy into mechanical energy, exhibiting high electromechanical conversion efficiency. Currently, the most common dielectric elastomers are silicone rubber elastomers, polyurethane elastomers, and polyacrylate elastomers. Among these, polyacrylate elastomers possess the best performance of the three elastomer materials and are the preferred material for dielectric elastomer research. Polyacrylate elastomers are inexpensive, have good adhesion, and possess a high dielectric constant and energy density (3.4 MJ / m³). 3 The dielectric constant and breakdown strength of polyacrylate elastomers are relatively high, with excellent breakdown strength after high pre-stretching and electroinduced deformation reaching up to 380%, generating a maximum stress of 7.7 MPa. Although polyacrylate elastomers have high dielectric constant and breakdown strength, many obstacles still limit their applications. These materials only exhibit valuable stress-strain and high dielectric properties under high pre-strain and high driving voltage conditions, but many instability problems arise in practical applications. Their high viscoelasticity leads to long response times, and they are also highly sensitive to temperature and humidity, severely limiting the widespread application of polyacrylate materials.

[0004] The shortcomings of existing acylation reaction technologies include: Hydroxybutyl acrylate (4-HBA) is an important functional monomer, and its industrial production is mainly achieved through multi-stage continuous esterification of acrylic acid with 1,4-butanediol. However, the subsequent modification of its hydroxyl groups (especially selective acylation) faces challenges: (1) Existing acylation catalysts (such as concentrated sulfuric acid) are prone to side reactions; (2) The reaction efficiency is low and the product viscosity is high; (3) The functional groups have poor tolerance, making it difficult to achieve high selective modification. Technical bottlenecks in polymer network construction: When constructing networks through free radical polymerization, multifunctional monomers are prone to generating high crosslinking density regions, leading to internal stress concentration and material brittleness. Studies have shown that adding thiol chain transfer agents can improve network uniformity, but will reduce mechanical strength. In addition, the compatibility of existing crosslinking agents (CN9021NS) with monomers is significantly affected by the monomer structure. Long-chain hydrophobic monomers are prone to phase separation, resulting in a decrease in material transmittance. Summary of the Invention

[0005] In order to overcome the shortcomings of the prior art, the present invention aims to provide a bipolar group acrylate polymer-based dielectric elastomer material and its preparation method, so as to solve the technical problems of multiple side reactions and low efficiency of acylation reaction in the synthesis of existing acrylate-based dielectric elastomers, as well as poor polymer network compatibility and easy phase separation.

[0006] To achieve the above objectives, the present invention employs the following technical solution: This invention discloses a method for preparing a bipolar group acrylate polymer-based dielectric elastomer material, comprising the following steps: Hydroxybutyl acrylate and dichloromethane were mixed evenly, organic acid and acylation catalyst were added, and after stirring and reaction, the mixture was purified to obtain hydroxybutyl acrylate diester monomer; then crosslinking agent and photoinitiator were added, mixed evenly, and cured and crosslinked under ultraviolet light to obtain bipolar group acrylate polymer-based dielectric elastomer material.

[0007] Preferably, the mass ratio of hydroxybutyl acrylate, dichloromethane, organic acid and 4-dimethylaminopyridine is 100:(300~500):(60~90):(3~5) by mass parts.

[0008] Preferably, the organic acid is acetic anhydride, propionic anhydride, or butyric anhydride.

[0009] Preferably, the acylation catalyst is 4-dimethylaminopyridine.

[0010] Preferably, the stirring reaction conditions include: stirring at 25~40℃ for 2~6 hours.

[0011] Preferably, the purification conditions include: first, washing repeatedly with deionized water to remove unreacted organic acids and byproducts generated in the reaction; separating the organic layer; then adding anhydrous sodium sulfate or anhydrous magnesium sulfate to remove excess water; and finally, evaporating dichloromethane to obtain hydroxybutyl acrylate diester monomer.

[0012] Preferably, the crosslinking agent is a multifunctional acrylate crosslinking agent; the mass ratio of hydroxybutyl acrylate diester monomer to crosslinking agent is 1:(0.004~0.008).

[0013] Preferably, the photoinitiator is 2-hydroxy-2-methylphenylacetone; the mass percentage of the photoinitiator is 0.4% to 0.8%.

[0014] Preferably, the ultraviolet light irradiation time is 20-30 minutes.

[0015] The present invention also discloses a bipolar group acrylate polymer-based dielectric elastomer material, which is prepared by the above-mentioned preparation method of the bipolar group acrylate polymer-based dielectric elastomer material.

[0016] Compared with the prior art, the present invention has the following beneficial effects: This invention discloses a method for preparing bipolar group acrylate polymer-based dielectric elastomer materials. By employing a mild and highly selective acylation catalyst system, it efficiently synthesizes hydroxybutyl acrylate diester monomers with precisely customizable side chain structures (R groups) while preserving the activity of the acrylic acid double bond. Traditional monomers such as hydroxyalkyl acrylates (e.g., HEA / HPA) contain only one polymerizable double bond and one hydroxyl group, requiring additional modification of the hydroxyl group to regulate properties. The diester compound of this invention retains the acrylic acid double bond and participates in free radical polymerization to construct a network, introducing ester side chains (-OCOR). The intermolecular forces, chain flexibility, and free volume are directly controlled through the R groups (H, CH3, C2H5, C3H7), enabling the integration of polymerization sites and performance-regulating groups within the monomolecule, avoiding compatibility issues with comonomers. R(H / CH3) enhances intermolecular forces to increase crosslinking density, while R(C2H5 / C3H7) increases interchain spacing to reduce crosslinking density and increase elongation at break. This hydroxybutyl acrylate diester monomer, with its tunable polarity and excellent compatibility with crosslinking agents, enabled the construction of a uniform and dense crosslinked network via UV photoinitiation. It successfully avoids the problems of double bond side reactions, multi-component phase separation, and cumbersome post-modification inherent in traditional methods, resulting in highly predictable and reproducible material properties and laying the foundation for the controllable preparation of high-performance dielectric elastomers. The ability to develop a series of structurally tunable hydroxybutyl acrylate derivatives and construct performance-controllable polymer networks through their synergistic effect with crosslinking agents is of great significance for promoting the customized development of functional polymer materials.

[0017] Furthermore, the mass ratio of hydroxybutyl acrylate, dichloromethane, organic acid, and 4-dimethylaminopyridine, by mass parts, is 100:(300~500):(60~90):(3~5); this effectively balances conversion rate and cost, avoiding the purification burden caused by excessive reagents or incomplete reaction caused by insufficient reagents. It achieves high efficiency and selectivity in hydroxylation, with a double bond retention rate >98%.

[0018] Furthermore, the organic acid is acetic anhydride, propionic anhydride, or butyric anhydride, corresponding to the R groups in the diester monomer as H (acetyl), CH3 (propionyl), and C2H5 (butyryl), respectively. R being H or CH3 (short chain) aims to enhance intermolecular forces and increase crosslinking density (corresponding to acetic anhydride and propionic anhydride). R being C2H5 aims to increase interchain spacing, reduce crosslinking density, and increase elongation at break (corresponding to butyric anhydride).

[0019] Furthermore, the acylation catalyst is 4-dimethylaminopyridine, which effectively avoids side reactions such as hydrolysis of the acrylic acid double bond and has a high double bond retention rate; through the nucleophilic activation mechanism, the reaction time is shortened to 2-6 hours; the catalyst system is mild, reducing neutralization, complex distillation and other steps, and reducing waste generation.

[0020] Furthermore, the stirring reaction conditions include: stirring at 25~40℃ for 2~6 hours; this avoids side reactions that may be caused by high temperature, ensures the mildness and controllability of the reaction, and significantly shortens the reaction time compared to traditional methods.

[0021] Furthermore, water washing removes unreacted acid and byproducts, and the use of a DMAP catalyst allows the post-treatment to primarily target water-soluble impurities, resulting in a simple and efficient process. The overall purification steps—water washing, drying, and rotary evaporation—avoid complex chemical post-treatments, demonstrating the process's environmental friendliness and ease of operation.

[0022] Furthermore, the crosslinking agent is a multifunctional acrylate crosslinking agent; the mass ratio of hydroxybutyl acrylate diester monomer to crosslinking agent is 1:(0.004~0.008); by adjusting the polarity of the diester monomer side chain (-OCOR), its compatibility with the selected crosslinking agent is improved. The optimized dosage ratio helps to form a uniform and controllable crosslinking network, avoiding phase separation caused by compatibility issues, thereby improving the uniformity of material properties.

[0023] Furthermore, the photoinitiator is 2-hydroxy-2-methylphenylacetone; the mass percentage of the photoinitiator is 0.4%~0.8%; ensuring the high efficiency and controllability of the ultraviolet curing process is an important process guarantee for achieving stable and repeatable preparation of elastomer films.

[0024] Furthermore, the ultraviolet light irradiation time was 20-30 minutes, ensuring the fullness and completeness of the network construction.

[0025] This invention discloses a bipolar acrylate polymer-based dielectric elastomer material. The material's unique molecular structure of an acrylate backbone and diester polar side chains cleverly balances the key properties of high dielectric constant and low elastic modulus—a combination typically difficult to achieve synergistically—through the rational design of the R-groups in the side chains. The introduction of polar ester groups enhances the material's polarization ability, which is beneficial for increasing the dielectric constant; while the flexible side chains increase chain mobility, effectively reducing the modulus. Furthermore, by changing the chain length of the R-groups, the tensile strength and elongation at break of the material can be continuously adjusted over a wide range. The resulting uniform network structure also gives the material excellent performance consistency and stability, solving the performance inconsistencies and defects caused by compatibility issues in traditional materials, and expanding its application prospects in fields such as flexible actuators and sensors. Attached Figure Description

[0026] Figure 1 This is a schematic diagram of the DMAP-catalyzed acylation reaction of hydroxybutyl acrylate with different acid anhydrides according to the present invention; wherein, (a) is acetic anhydride; (b) is propionic anhydride; and (c) is butyric anhydride. Figure 2This describes the three-dimensional network formation process between hydroxybutyl acrylate diester monomer and CN9021NS crosslinking agent; Figure 3 Hydroxybutyl acrylate diester monomers generated by the reaction of different acid anhydrides with hydroxybutyl acrylate 1 Schematic diagram of H NMR spectrum; (a) shows acetic anhydride. 1 Schematic diagram of H NMR spectrum; (b) shows propionic anhydride. 1 Schematic diagram of H NMR spectrum; (c) is butyric anhydride. 1 Schematic diagram of H NMR spectrum; Figure 4 Schematic diagram of FT-IR spectra of hydroxybutyl acrylate diester monomers generated by the reaction of different acid anhydrides with hydroxybutyl acrylate; Figure 5 Schematic diagram of FT-IR spectra of acrylate polymers generated by reacting different hydroxybutyl acrylate diester monomers with CN9021NS crosslinking agent; Figure 6 The strain diagram shows the electrically driven strain of the acrylate polymer formed by the reaction of the diester compound with CN9021NS crosslinking agent. Detailed Implementation

[0027] The technical solution of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0028] Unless otherwise specified, all embodiments and preferred embodiments mentioned herein can be combined to form new technical solutions.

[0029] Unless otherwise specified, all the technical features and preferred features mentioned herein can be combined to form new technical solutions.

[0030] In this invention, unless otherwise specified, percentage (%) or parts refer to weight percentage or parts relative to the composition.

[0031] Unless otherwise specified, the components or preferred components involved in this invention can be combined with each other to form new technical solutions.

[0032] In this invention, unless otherwise specified, the numerical range "a~b" represents a shortened representation of any combination of real numbers between a and b, where a and b are both real numbers. For example, the numerical range "6~22" indicates that all real numbers between "6~22" have been listed in this document, and "6~22" is simply a shortened representation of these numerical combinations.

[0033] The "scope" disclosed in this invention can be in the form of a lower limit and an upper limit, and can be one or more lower limits and one or more upper limits, respectively.

[0034] In this invention, the term "and / or" as used herein refers to any combination of one or more of the associated listed items, as well as all possible combinations, and includes such combinations.

[0035] In this invention, unless otherwise stated, the various reactions or operation steps may be performed sequentially or in a particular order. Preferably, the reaction methods described herein are performed sequentially.

[0036] Unless otherwise stated, the technical and scientific terms used herein have the same meanings as those familiar to those skilled in the art. Furthermore, any methods or materials similar to or equivalent to those described herein may also be used in this invention.

[0037] Structural design and preparation of diester monomers This invention first provides a novel type of hydroxybutyl acrylate-based diester monomer. In order to further expand the application range of acrylate dielectric elastomers and solve the problems of high elastic modulus and low dielectric constant, this invention uses hydroxybutyl acrylate as a matrix to prepare diester-based polymer dielectric elastomer materials with different chain lengths through esterification reaction, thereby improving the mechanical properties, driving properties, dielectric properties, etc. of bipolar group acrylate polymer-based dielectric elastomer materials.

[0038] The bipolar acrylate polymer-based dielectric elastomer material provided by this invention uses hydroxybutyl acrylate (HBA) as a matrix, which undergoes an esterification reaction with an organic acid to esterify the -OH group in HBA into -COO, thereby increasing the polarity of the matrix and preparing an elastomer material with superior performance. This effectively improves the tensile strength of the elastomer material, reduces the elastic modulus, and increases the dielectric constant, thus significantly improving the dielectric properties of the dielectric elastomer material. The specific technical solution is as follows: A method for preparing a hydroxybutyl acrylate diester monomer includes the following steps: Prepare 100 parts by weight of dielectric elastomer matrix, 300-500 parts by weight of dichloromethane, 60-90 parts by weight of organic acid, and 3-5 parts by weight of catalyst.

[0039] 100 parts by weight of purified hydroxybutyl acrylate (HBA) are mixed evenly with 300-500 parts by weight of dichloromethane. 60-90 parts by weight of organic acid and 3-5 parts by weight of 4-dimethylaminopyridine (DMPA) are added as initiators. The mixture is stirred and reacted at 25-40°C for 2-6 hours. After purifying the reaction product, the hydroxybutyl acrylate diester monomer is obtained.

[0040] These compounds are prepared by the selective acylation of hydroxybutyl acrylate with hydroxyl groups. The core technology lies in: (1) Catalytic system innovation: 4-Dimethylaminopyridine (DMAP) is used as the acylation catalyst, and its dosage is 0.04~0.08 mol of hydroxybutyl acrylate. DMAP significantly improves the reaction efficiency through nucleophilic activation mechanism (the reaction time is shortened to 2~6h), while avoiding the side reaction of acrylic acid double bond caused by acid catalyst.

[0041] (2) Optimization of reaction conditions: The reaction was carried out under mild conditions of 25~40℃. The molar ratio of hydroxybutyl acrylate to acylation reagent (acid anhydride) was 1:0.5 to balance the conversion rate and cost.

[0042] Methods for constructing acrylate polymer networks Based on the above diester monomers, the present invention further provides a method for constructing an acrylate-based polymer network and a method for preparing a bipolar group acrylate polymer-based dielectric elastomer material, comprising the following steps: (1) Preparation of prepolymer: Hydroxybutyl acrylate diester monomer and crosslinking agent (CN9021NS) are mixed at a mass ratio of 1:0.004~1:0.008.

[0043] (2) Selection of initiation system: 2-hydroxy-2-methylphenylacetone (HMPP) photoinitiator was added at a dosage of 0.4% to 0.8% of the total mass. The crosslinking agent CN9021NS is a multifunctional acrylate crosslinking agent. The carbon chain length of the R group in the diester monomer is different, which affects the glass transition temperature and dielectric properties, thereby regulating the electro-driven performance. The electro-driven strain is 17% to 27.6%.

[0044] (3) Network molding process: The mixture is injected into a mold and free radical polymerization is initiated under ultraviolet light for 20-30 min to form a three-dimensional network structure of acrylate-based polymer, thus obtaining a bipolar group acrylate polymer-based dielectric elastomer material. The network structure is controlled by the chain length of the R group. Short chain R (H / CH3) increases the intermolecular forces and forms a high crosslinking density network, while long chain R (CH2CH3 / CH2CH2CH3) introduces flexible spacers, reduces the crosslinking density, and increases the elongation at break.

[0045] (4) Perform dielectric property tests on the thin film in step (3).

[0046] This invention successfully prepared a novel acrylate polymer-based dielectric elastomer material with different chain lengths and diester groups through free radical polymerization and esterification reaction.

[0047] This invention has the following advantages: 1. Advantages of molecular structure design (1) Synergistic effect of bifunctional groups: Traditional monomeric hydroxyalkyl acrylates (such as HEA / HPA) contain only one polymerizable double bond and one hydroxyl group. The hydroxyl group needs to be modified to regulate the properties. The diester compound of this invention retains the acrylic double bond and participates in free radical polymerization to construct a network and introduces ester side chains (-OCOR). Through the R groups (H, CH3, C2H5, C3H7), the intermolecular forces, chain flexibility and free volume are directly regulated, so that the polymerization site and the performance regulating group are integrated within the monomolecule, avoiding the compatibility problem of comonomers.

[0048] (2) Precise control of R group chain length: R(H / CH3) enhances intermolecular forces to increase crosslinking density, and R(C2H5 / C3H7) increases interchain spacing to reduce crosslinking density and increase elongation at break.

[0049] 2. Advantages of the synthesis process (1) High efficiency and selectivity of hydroxy acylation: Traditional methods use concentrated sulfuric acid as a catalyst for acylation, which can lead to side reactions and hydrolysis of double bonds. Furthermore, the subsequent processing is complex and requires steps such as neutralization and distillation purification. The method of this invention uses DMAP catalysis (0.05 mol), which results in a double bond retention rate of >98%, a 50% reduction in reaction time, and the solvent system is easy to remove, reducing the generation of waste.

[0050] (2) Improved uniformity of network construction. Traditional methods use crosslinking agents (CN9021NS) and hydrophilic monomers for construction, which leads to poor compatibility and problems such as phase separation. This invention adjusts the polarity of the diester compound by adjusting the -OCOR group, which has better compatibility with the crosslinking agent (CN9021NS) and is superior to traditional methods.

[0051] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0052] Example 1 Preparation of hydroxybutyl acrylate diester monomer Raw materials: Hydroxybutyl acrylate (purity ≥99%), dichloromethane, acetic anhydride / propionic anhydride / butyric anhydride (chemically pure), 4-dimethylaminopyridine (DMAP) (analytical grade) (1) In a dry reaction flask, add hydroxybutyl acrylate (10 g, 0.069 mol), acetic anhydride (3.519 g, 0.0345 mol), and dichloromethane (30 mL).

[0053] (2) Add DMAP (0.4209 g, 0.00345 mol) with stirring and react at room temperature for 6 h.

[0054] (3) The reaction solution was washed twice with 5% NaHCO3 solution and then washed with water until neutral.

[0055] (4) The organic phase was dried with anhydrous MgSO4 to absorb water, and then vacuum dried to obtain colorless transparent liquid hydroxybutyl acrylate acetate.

[0056] Other diester monomers were prepared using the same method: Propionate: The reaction was carried out at room temperature for 6 hours using propionic anhydride as the acylating agent.

[0057] Butyrate ester: with butyric anhydride as the acylating agent, the reaction is carried out at room temperature for 6 hours.

[0058] Construction of polymer networks (using hydroxybutyl acrylate acetate as an example) Raw materials: Hydroxybutyl acrylate acetate prepared in Example 1, crosslinking agent (CN9021NS), and photoinitiator 2-hydroxy-2-methylphenylacetone (HMPP). Steps: (1) Mix hydroxybutyl acrylate acetate (2.5 g) with crosslinking agent (CN9021NS) (0.4% 0.01 g by mass fraction) and add photoinitiator (HMPP 0.4% 0.01 g by mass fraction).

[0059] (2) The mixture is ultrasonically degassed and then injected into a polytetrafluoroethylene mold.

[0060] (3) React under ultraviolet light for 30 min.

[0061] (4) Cool and demold to obtain a transparent sheet-like polymer network.

[0062] (5) The dielectric properties of the obtained bipolar group acrylate polymer-based dielectric elastomer material were tested.

[0063] Example 2 Preparation of hydroxybutyl acrylate diester monomer Raw materials: Hydroxybutyl acrylate (purity ≥99%), acetic anhydride / propionic anhydride / butyric anhydride (chemically pure), 4-dimethylaminopyridine (DMAP) (analytical grade) (1) In a dry reaction flask, add hydroxybutyl acrylate (10 g, 0.069 mol), acetic anhydride (3.519 g, 0.0345 mol), and dichloromethane (30 mL).

[0064] (2) Add DMAP (0.4209 g, 0.00345 mol) with stirring and react at room temperature for 6 h.

[0065] (3) The reaction solution was washed twice with 5% NaHCO3 solution and then washed with water until neutral.

[0066] (4) The organic phase was dried with anhydrous MgSO4 to absorb water, and then vacuum dried to obtain colorless transparent liquid hydroxybutyl acrylate acetate.

[0067] Other diester monomers were prepared using the same method: Propionate: The reaction was carried out at room temperature for 6 hours using propionic anhydride as the acylating agent.

[0068] Butyrate ester: with butyric anhydride as the acylating agent, the reaction is carried out at room temperature for 6 hours.

[0069] Construction of polymer networks (using hydroxybutyl acrylate acetate as an example) Raw materials: Hydroxybutyl acrylate acetate prepared in Example 1, crosslinking agent (CN9021NS), and photoinitiator 2-hydroxy-2-methylphenylacetone (HMPP). Steps: (1) Mix hydroxybutyl acrylate acetate (2.5 g) with crosslinking agent (CN9021NS) (0.5% by mass, 0.0125 g) and add photoinitiator (HMPP, 0.5% by mass, 0.0125 g).

[0070] (2) The mixture is ultrasonically degassed and then injected into a polytetrafluoroethylene mold.

[0071] (3) React under ultraviolet light for 30 min.

[0072] (4) Cool and demold to obtain a transparent sheet-like polymer network.

[0073] (5) The dielectric properties of the obtained bipolar group acrylate polymer-based dielectric elastomer material were tested.

[0074] Example 3 Preparation of hydroxybutyl acrylate diester monomer Raw materials: Hydroxybutyl acrylate (purity ≥99%), acetic anhydride / propionic anhydride / butyric anhydride (chemically pure), 4-dimethylaminopyridine (DMAP) (analytical grade) (1) In a dry reaction flask, add hydroxybutyl acrylate (10 g, 0.069 mol), acetic anhydride (3.519 g, 0.0345 mol), and dichloromethane (30 mL).

[0075] (2) Add DMAP (0.4209 g, 0.00345 mol) with stirring and react at room temperature for 6 h.

[0076] (3) The reaction solution was washed twice with 5% NaHCO3 solution and then washed with water until neutral.

[0077] (4) The organic phase was dried with anhydrous MgSO4 to absorb water, and then vacuum dried to obtain colorless transparent liquid hydroxybutyl acrylate acetate.

[0078] Other diester monomers were prepared using the same method: Propionate: The reaction was carried out at room temperature for 6 hours using propionic anhydride as the acylating agent.

[0079] Butyrate ester: with butyric anhydride as the acylating agent, the reaction is carried out at room temperature for 6 hours.

[0080] Construction of polymer networks (using hydroxybutyl acrylate acetate as an example) Raw materials: Hydroxybutyl acrylate acetate prepared in Example 1, crosslinking agent (CN9021NS), and photoinitiator 2-hydroxy-2-methylphenylacetone (HMPP). Steps: (1) Mix hydroxybutyl acrylate acetate (2.5 g) with crosslinking agent (CN9021NS) (0.6% by mass, 0.015 g) and add photoinitiator (HMPP, 0.6% by mass, 0.015 g).

[0081] (2) The mixture is ultrasonically degassed and then injected into a polytetrafluoroethylene mold.

[0082] (3) React under ultraviolet light for 30 min.

[0083] (4) Cool and demold to obtain a transparent sheet-like polymer network.

[0084] (5) The dielectric properties of the obtained bipolar group acrylate polymer-based dielectric elastomer material were tested.

[0085] Example 4 Preparation of hydroxybutyl acrylate diester monomer Raw materials: Hydroxybutyl acrylate (purity ≥99%), acetic anhydride / propionic anhydride / butyric anhydride (chemically pure), 4-dimethylaminopyridine (DMAP) (analytical grade) (1) In a dry reaction flask, add hydroxybutyl acrylate (10 g, 0.069 mol), acetic anhydride (3.519 g, 0.0345 mol), and dichloromethane (30 mL).

[0086] (2) Add DMAP (0.4209 g, 0.00345 mol) under stirring and react at room temperature for 6 h.

[0087] (3) The reaction solution was washed twice with 5% NaHCO3 solution and then washed with water until neutral.

[0088] (4) The organic phase was dried with anhydrous MgSO4 to absorb water, and then vacuum dried to obtain colorless transparent liquid hydroxybutyl acrylate acetate.

[0089] Other diester monomers were prepared using the same method: Propionate: The reaction was carried out at room temperature for 6 hours using propionic anhydride as the acylating agent.

[0090] Butyrate ester: with butyric anhydride as the acylating agent, the reaction is carried out at room temperature for 6 hours.

[0091] Construction of polymer networks (using hydroxybutyl acrylate acetate as an example) Raw materials: Hydroxybutyl acrylate acetate prepared in Example 1, crosslinking agent (CN9021NS), and photoinitiator 2-hydroxy-2-methylphenylacetone (HMPP). Steps: (1) Mix hydroxybutyl acrylate acetate (2.5 g) with crosslinking agent (CN9021NS) (0.7% by mass, 0.0175 g) and add photoinitiator (HMPP, 0.7% by mass, 0.0175 g).

[0092] (2) The mixture is ultrasonically degassed and then injected into a polytetrafluoroethylene mold.

[0093] (3) React under ultraviolet light for 30 min.

[0094] (4) Cool and demold to obtain a transparent sheet-like polymer network.

[0095] (5) The dielectric properties of the obtained bipolar group acrylate polymer-based dielectric elastomer material were tested.

[0096] Example 5 Preparation of hydroxybutyl acrylate diester monomer Raw materials: Hydroxybutyl acrylate (purity ≥99%), acetic anhydride / propionic anhydride / butyric anhydride (chemically pure), 4-dimethylaminopyridine (DMAP) (analytical grade) (1) In a dry reaction flask, add hydroxybutyl acrylate (10 g, 0.069 mol), acetic anhydride (3.519 g, 0.0345 mol) and dichloromethane (30 mL).

[0097] (2) Add DMAP (0.4209 g, 0.00345 mol) under stirring and react at room temperature for 6 h.

[0098] (3) The reaction solution was washed twice with 5% NaHCO3 solution and then washed with water until neutral.

[0099] (4) The organic phase was dried with anhydrous MgSO4 to absorb water, and then vacuum dried to obtain colorless transparent liquid hydroxybutyl acrylate acetate.

[0100] Other diester monomers were prepared using the same method: Propionate: The reaction was carried out at room temperature for 6 hours using propionic anhydride as the acylating agent.

[0101] Butyrate ester: with butyric anhydride as the acylating agent, the reaction is carried out at room temperature for 6 hours.

[0102] Construction of polymer networks (using hydroxybutyl acrylate acetate as an example) Raw materials: Hydroxybutyl acrylate acetate prepared in Example 1, crosslinking agent (CN9021NS), and photoinitiator 2-hydroxy-2-methylphenylacetone (HMPP). Steps: (1) Mix hydroxybutyl acrylate acetate (2.5 g) with crosslinking agent (CN9021NS) (0.8% by mass, 0.02 g) and add photoinitiator (HMPP, 0.8% by mass, 0.02 g).

[0103] (2) The mixture is ultrasonically degassed and then injected into a polytetrafluoroethylene mold.

[0104] (3) React under ultraviolet light for 30 min.

[0105] (4) Cool and demold to obtain a transparent sheet-like polymer network.

[0106] (5) The dielectric properties of the obtained bipolar group acrylate polymer-based dielectric elastomer material were tested.

[0107] Example 6 Construction of propionate polymer network Preparation of hydroxybutyl acrylate diester monomer: Raw materials: Hydroxybutyl acrylate (purity ≥99%), propionic anhydride (chemically pure), 4-dimethylaminopyridine (DMAP) (analytical grade) (1) In a dry reaction flask, add hydroxybutyl acrylate (10 g, 0.069 mol), propionic anhydride (4.223 g, 0.0414 mol) and dichloromethane (30 mL).

[0108] (2) Add DMAP (0.505 g, 0.00414 mol) with stirring and react at room temperature for 6 hours.

[0109] (3) The reaction solution was washed twice with 5% NaHCO3 solution and then washed with water until neutral.

[0110] (4) The organic phase was dried with anhydrous MgSO4 to absorb water, and then vacuum dried to obtain a colorless and transparent liquid hydroxybutyl acrylate propionate.

[0111] Construction of polymer networks: Raw materials: Hydroxybutyl acrylate propionate (2.5g), crosslinking agent CN9021NS (0.6% by mass, 0.015g), photoinitiator HMPP (0.6% by mass, 0.015g); Steps: After ultrasonic degassing, the mixture is injected into a polytetrafluoroethylene mold; the mixture is reacted under ultraviolet light for 30 min; after cooling and demolding, a transparent sheet-like polymer network is obtained; the dielectric properties of the obtained bipolar group acrylate polymer-based dielectric elastomer material are tested.

[0112] Example 7 Butyrate polymer network construction Preparation of hydroxybutyl acrylate diester monomer: Raw materials: Hydroxybutyl acrylate (purity ≥99%), butyric anhydride (chemically pure), 4-dimethylaminopyridine (DMAP) (analytical grade) (1) In a dry reaction flask, add hydroxybutyl acrylate (10 g, 0.069 mol), butyric anhydride (4.5696 g, 0.0448 mol) and dichloromethane (30 mL).

[0113] (2) Add DMAP (0.5892 g, 0.00483 mol) with stirring and react at room temperature for 6 hours.

[0114] (3) The reaction solution was washed twice with 5% NaHCO3 solution and then washed with water until neutral.

[0115] (4) The organic phase was dried with anhydrous MgSO4 to absorb water, and then vacuum dried to obtain a colorless and transparent liquid hydroxybutyl acrylate.

[0116] Construction of polymer networks: Raw materials: Hydroxybutyl butyrate acrylate (2.5g), crosslinking agent CN9021NS (0.6% by mass, 0.015g), photoinitiator HMPP (0.6% by mass, 0.015g); Steps: After ultrasonic degassing, the mixture is injected into a polytetrafluoroethylene mold; the mixture is reacted under ultraviolet light for 30 min; after cooling and demolding, a transparent sheet-like polymer network is obtained; the dielectric properties of the obtained bipolar group acrylate polymer-based dielectric elastomer material are tested.

[0117] Example 8 Preparation of hydroxybutyl acrylate diester monomer: Raw materials: hydroxybutyl acrylate (10g, 0.069mol), acetic anhydride (6g, 0.0588mol, corresponding to hydroxybutyl acrylate: organic acid = 100:60), dichloromethane (30g), DMAP (0.3g, corresponding to a ratio of 100:3); Steps: Add the raw material to the dry reaction flask, stir and react at 40℃ for 2 hours, wash twice with 5% NaHCO3 solution, wash with water until neutral, dry with anhydrous MgSO4, and evaporate under vacuum to obtain hydroxybutyl acrylate acetate.

[0118] Construction of polymer networks: Raw materials: the above monomer (2.5g), crosslinking agent CN9021NS (mass fraction 0.6%, 0.015g), photoinitiator HMPP (mass fraction 0.6%, 0.015g).

[0119] Steps: After ultrasonic degassing, the mixture is injected into a polytetrafluoroethylene mold; the mixture is reacted under ultraviolet light for 20 min; after cooling and demolding, a transparent sheet-like polymer network is obtained; the dielectric properties of the obtained bipolar group acrylate polymer-based dielectric elastomer material are tested.

[0120] Example 9 Preparation of hydroxybutyl acrylate diester monomer: Raw materials: hydroxybutyl acrylate (10g, 0.069mol), acetic anhydride (9g, 0.0882mol, corresponding to hydroxybutyl acrylate: organic acid = 100:90), dichloromethane (50g, corresponding to a ratio of 100:500), DMAP (0.5g, corresponding to a ratio of 100:5). Steps: Add the raw material to the dry reaction flask, stir and react at 30℃ for 4 hours, wash twice with 5% NaHCO3 solution, wash with water until neutral, dry with anhydrous MgSO4, and evaporate under vacuum to obtain hydroxybutyl acrylate acetate. Construction of polymer networks: Raw materials: the above monomer (2.5g), crosslinking agent CN9021NS (0.6% by mass, 0.015g), photoinitiator HMPP (0.6% by mass, 0.015g); Steps: After ultrasonic degassing, the mixture is injected into a polytetrafluoroethylene mold; the mixture is reacted under ultraviolet light for 25 minutes; after cooling and demolding, a transparent sheet-like polymer network is obtained; the dielectric properties of the obtained bipolar group acrylate polymer-based dielectric elastomer material are tested.

[0121] See Figure 1 This is a schematic diagram of the DMAP-catalyzed acylation reaction of hydroxybutyl acrylate with different acid anhydrides according to the present invention; wherein, (a) is acetic anhydride; (b) is propionic anhydride; and (c) is butyric anhydride. As can be seen from the figure, hydroxybutyl acrylate undergoes esterification reaction with different acid anhydrides to generate the corresponding hydroxybutyl acrylate diester monomers.

[0122] Figure 2 This diagram illustrates the three-dimensional network formation process of hydroxybutyl acrylate diester monomers and CN9021NS crosslinking agent. As shown in the figure, rapid polymerization is achieved using a UV-photopolymerization mechanism. This process effectively integrates functional acrylate diester monomers with a flexible crosslinking agent into a three-dimensional polymer network, providing a well-defined and tunable material basis for subsequent research on its dielectric and electro-driven properties.

[0123] Figure 3 Hydroxybutyl acrylate diester monomers generated by the reaction of different acid anhydrides with hydroxybutyl acrylate 1 Schematic diagram of H NMR spectrum; (a) acetic anhydride; (b) propionic anhydride; (c) butyric anhydride; As can be seen from the figure, the NMR peak at chemical shift value δ=3.27 ppm, which originally belonged to -OH in the (HBA) molecular structure, disappeared, and the NMR peak at chemical shift value δ=4.11 ppm(h) represents the hydrogen atom of the formate ester -OC(O)H of esterified (HBA-AA). The appearance of this peak indicates the successful synthesis of (HBA-AA); similar NMR peaks were also observed in propionic anhydride and butyric anhydride, proving their successful synthesis.

[0124] Figure 4 Schematic FT-IR spectra of hydroxybutyl acrylate diester monomers generated by the reaction of different acid anhydrides with hydroxybutyl acrylate; where HBA represents hydroxybutyl acrylate, HBA-AA represents hydroxybutyl acetate, HBA-PA represents propionyloxybutyl acrylate, and HBA-BA represents acryloyloxybutyl butyrate. As can be seen from the figure, compared with HBA, the FT-IR spectra of HBA-AA, HBA-PA, and HBA-BA are at 1720 cm⁻¹, respectively. -1 1240cm -1 and 1180 cm -1New absorption peaks appeared at 2940 cm⁻¹, corresponding to the stretching vibration peak of C=O in the ester group, the antisymmetric stretching vibration absorption peak of -COC- on the ester group, and the symmetric stretching vibration absorption peak of -COC-. -1 and 2800 cm -1 The absorption peak appearing at 3400 cm⁻¹ corresponds to the stretching vibration absorption peak of methylene / methyl (-CH₂, -CH₃). Meanwhile, compared to HBA, other synthesized diester compounds show a peak at 3400 cm⁻¹. -1 The absence of a prominent -OH stretching vibration peak nearby suggests the successful preparation of the diester compound.

[0125] Figure 5 This is a schematic diagram of the FT-IR spectra of acrylate polymers generated by reacting different hydroxybutyl acrylate diester monomers with CN9021NS crosslinking agent. In the diagram, P(HBA-CN9021NS) represents the hydroxybutyl acrylate crosslinked network polymer, P(HBA-AA-CN9021NS) represents the hydroxybutyl acrylate acetate crosslinked network polymer, P(HBA-PA-CN9021NS) represents the propionyloxybutyl acrylate crosslinked network polymer, and P(HBA-BA-CN9021NS) represents the acryloyloxybutyl butyrate crosslinked network polymer. As can be seen from the figure, the FT-IR spectra of the photocrosslinked acrylate diester polymer network structures of P(HBA-CN9021NS), P(HBA-AA-CN9021NS), P(HBA-PA-CN9021NS), and P(HBA-BA-CN9021NS) at 1640 cm⁻¹... -1 The C=C double bond absorption peak disappeared at 1730 cm⁻¹, indicating that the double bond participated in polymerization, and the peak intensity decreased significantly. This directly proves the successful synthesis of the polymer crosslinking network. -1 and 1160 cm -1 New absorption peaks appeared at 3400 cm⁻¹, corresponding to the stretching vibration peak of the C=O carbonyl group in the ester group and the vibration absorption peak of the -COC- ether bond on the ester group, respectively. The increase in ether bonds resulted in peak broadening and enhancement. Meanwhile, compared to P(HBA-CN9021NS), other synthesized diester polymers showed higher absorption peaks at 3400 cm⁻¹. -1 The absence of a prominent -OH stretching vibration peak nearby suggests the successful preparation of the four diester polymers.

[0126] Figure 6Electro-driven strain diagrams of acrylate polymers generated by reacting different hydroxybutyl acrylate diester monomers with CN9021NS crosslinking agent. The diagrams show that, under the same electric field strength, the P(HBA-AA-CN9021NS) dielectric elastomer material exhibits the largest electro-driven strain. When the electric field strength is 10.3 kV / mm, the driven strains of P(HBA-CN9021NS), P(HBA-AA-CN9021NS), P(HBA-PA-CN9021NS), and P(HBA-BA-CN9021NS) reach 11.6%, 16.1%, 14.3%, and 13.7%, respectively. The maximum electro-driven strain of P(HBA-AA-CN9021NS) is attributed to its high polarity and good chain flexibility, which maximizes the electromechanical sensitivity β value.

[0127] Table 1. Dielectric property test results of the bipolar group acrylate polymer-based dielectric elastomer materials prepared in Examples 1-5

[0128] Table 1 shows the dielectric properties of the bipolar group acrylate polymer-based dielectric elastomer materials prepared in Examples 1-5. As can be seen from the table, the strong polarity of acetic anhydride results in the highest dielectric constant. This is because hydroxybutyl acetate acrylate, with its strongest intrinsic polar acetic acid group, minimal steric hindrance, and structural advantage of forming a network with higher polar group density, exhibits the highest dielectric constant macroscopically. Increasing the amount of initiator HMPP and crosslinking agent CN9021NS improves the dielectric constant to some extent. On the one hand, increasing the amount of crosslinking agent leads to a more complete and uniform three-dimensional network. The molecular chains are moderately fixed, the free volume is reduced, and the structure is more compact, which may be beneficial for charge storage. On the other hand, the crosslinking agent CN9021NS itself is a polyurethane acrylate containing polar urethane groups (-NH-COO-). Increasing its amount directly introduces more strongly polar groups into the system, thereby increasing the dielectric constant (ε). Excessive crosslinking density severely restricts the mobility of molecular chain segments and polar groups. Under an alternating electric field, polar groups (such as ester groups in the system) cannot reorient themselves in time to follow the direction of the electric field, resulting in a decrease in orientation polarization ability and a corresponding decrease in dielectric constant.

[0129] In summary, this invention provides a bipolar group acrylate polymer-based dielectric elastomer material and its preparation method. By employing DMAP catalysis to efficiently and selectively acylate the hydroxyl groups of hydroxybutyl acrylate, the double bond retention rate is high and the reaction time is short, avoiding the side reactions of traditional acid catalysis. Through the design of diester monomers and the control of R-group chain length, intermolecular forces and chain flexibility are precisely adjusted, optimizing crosslinking density and elongation at break. Simultaneously, network uniformity and compatibility with crosslinking agents are improved, thereby significantly enhancing the mechanical, driving, and dielectric properties of the dielectric elastomer, such as increasing tensile strength, reducing elastic modulus, and increasing dielectric constant, thus broadening its application range.

[0130] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing a bipolar group acrylate polymer-based dielectric elastomer material, characterized in that, Includes the following steps: Hydroxybutyl acrylate and dichloromethane were mixed evenly, organic acid and acylation catalyst were added, and after stirring and reaction, the mixture was purified to obtain hydroxybutyl acrylate diester monomer; then crosslinking agent and photoinitiator were added, mixed evenly, and cured and crosslinked under ultraviolet light to obtain bipolar group acrylate polymer-based dielectric elastomer material.

2. The method for preparing the bipolar group acrylate polymer-based dielectric elastomer material according to claim 1, characterized in that, The mass ratio of the hydroxybutyl acrylate, dichloromethane, organic acid and 4-dimethylaminopyridine is 100:(300~500):(60~90):(3~5) by mass parts.

3. The method for preparing the bipolar group acrylate polymer-based dielectric elastomer material according to claim 1, characterized in that, The organic acid is acetic anhydride, propionic anhydride, or butyric anhydride.

4. The method for preparing the bipolar group acrylate polymer-based dielectric elastomer material according to claim 1, characterized in that, The acylation catalyst is 4-dimethylaminopyridine.

5. The method for preparing the bipolar group acrylate polymer-based dielectric elastomer material according to claim 1, characterized in that, The conditions for the stirring reaction include: stirring at 25~40℃ for 2~6 hours.

6. The method for preparing the bipolar group acrylate polymer-based dielectric elastomer material according to claim 1, characterized in that, The purification conditions include: first, washing repeatedly with deionized water to remove unreacted organic acids and byproducts generated during the reaction; separating the organic layer; then adding anhydrous sodium sulfate or anhydrous magnesium sulfate to remove excess water; and finally, evaporating dichloromethane to obtain hydroxybutyl acrylate diester monomer.

7. The method for preparing the bipolar group acrylate polymer-based dielectric elastomer material according to claim 1, characterized in that, The crosslinking agent is a multifunctional acrylate crosslinking agent; the mass ratio of the hydroxybutyl acrylate diester monomer to the crosslinking agent is 1:(0.004~0.008).

8. The method for preparing the bipolar group acrylate polymer-based dielectric elastomer material according to claim 1, characterized in that, The photoinitiator is 2-hydroxy-2-methylphenylacetone; the mass percentage of the photoinitiator is 0.4%~0.8%.

9. The method for preparing the bipolar group acrylate polymer-based dielectric elastomer material according to claim 1, characterized in that, The ultraviolet light irradiation time is 20-30 minutes.

10. A bipolar group acrylate polymer-based dielectric elastomer material, characterized in that, The bipolar group acrylate polymer-based dielectric elastomer material was prepared using the preparation method described in any one of claims 1 to 9.

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