Acrylate dielectric elastomer with low strain drift and preparation method thereof

Abstract

The invention provides a low-strain drift acrylate dielectric elastomer and a preparation method thereof, and belongs to the field of dielectric elastomers. The invention provides a low-strain drift acrylate dielectric elastomer, which is prepared from the following preparation raw materials in percentage by mass: 20 to 35 percent of bifunctional aliphatic polyurethane acrylate; 15 to 69% of a monofunctional acrylate reactive diluent; 10 to 60% of a monofunctional acrylate active functional monomer; 0.4-1% of a photoinitiator; the monofunctional acrylate reactive diluent comprises a side chain, and a substituent group of the side chain comprises alkyl; polar groups in the monofunctional acrylate active functional monomer comprise one or more of hydroxyl, carboxyl and amino. The dielectric elastomer disclosed by the invention has the advantages of low mechanical loss, high response speed and low strain drift, the dynamic driving response characteristic is remarkably improved, and the application range in the field of dielectric elastomer flexible devices is widened.

Description

Technical Field

[0001] This invention relates to the field of dielectric elastomers, and more specifically to a low-strain-drift acrylate dielectric elastomer and its preparation method. Background Technology

[0002] Dielectric elastomers exhibit significant reversible elastic deformation under Maxwell stress generated by electrostatic charge, directly converting input electrical energy into mechanical energy output. They possess advantages such as being lightweight and flexible, exhibiting large deformation, high energy density, and high energy conversion efficiency, leading to their widespread application in flexible actuators. However, the high mechanical losses and severe strain drift caused by their viscoelasticity significantly limit their actuation performance. To address this issue, some researchers have attempted to suppress viscoelastic losses and strain drift in elastomers by increasing the degree of material crosslinking. However, while increasing the degree of crosslinking suppresses viscoelastic losses, it typically leads to a significant increase in the Young's modulus, reducing the response speed. Summary of the Invention

[0003] This invention provides a low-strain-drift acrylate dielectric elastomer and its preparation method. The low-strain-drift acrylate dielectric elastomer of this invention has the advantages of low mechanical loss, fast response speed and low strain drift.

[0004] This invention provides a low-strain-drift acrylate dielectric elastomer, comprising the following raw materials by mass fraction: Bifunctional aliphatic polyurethane acrylate 20~35%; Monofunctional acrylate reactive diluent 15~69%; Monofunctional acrylate active functional monomers: 10-60%; Photoinitiator 0.4~1%; The monofunctional acrylate reactive diluent includes a side chain, and the substituents of the side chain include alkyl groups; The polar groups in the monofunctional acrylate active functional monomer include one or more of hydroxyl, carboxyl, and amino groups.

[0005] Preferably, the molecular weight of the bifunctional aliphatic polyurethane acrylate is 10. 4 ~10 5 g / mol.

[0006] Preferably, the bifunctional aliphatic polyurethane acrylate comprises CN9021NS produced by Sartoma Guangzhou Chemical Co., Ltd.

[0007] Preferably, the monofunctional acrylate reactive diluent includes alkyl methacrylates and / or alkyl acrylates.

[0008] Preferably, the alkyl methacrylate includes one or more of undecyl methacrylate, dodecyl methacrylate, tridecyl methacrylate, and tetradecyl methacrylate; The alkyl acrylates include one or more of decyl acrylate, dodecyl acrylate, tridecyl acrylate, and tetradecyl acrylate.

[0009] Preferably, the monofunctional acrylate active functional monomer includes one or more of hydroxyethyl acrylate, hydroxypropyl acrylate, 2-carboxyethyl acrylate, and hydroxybutyl acrylate.

[0010] Preferably, the photoinitiator includes a free radical photoinitiator.

[0011] Preferably, the free radical photoinitiator includes one or more of benzoyl, α,α-diethoxyacetophenone, 2-hydroxy-2-methyl-1-phenyl-1-propanone, 1-hydroxy-cyclohexylbenzophenone, and 2-methyl-2-(4-morpholino)-1-[4-(methylthio)phenyl]-1-propanone.

[0012] The present invention also provides a method for preparing the low strain drift acrylate dielectric elastomer described in the above technical solution, comprising the following steps: The raw materials for preparing the low strain drift acrylate dielectric elastomer are mixed and then subjected to photopolymerization to obtain the low strain drift acrylate dielectric elastomer.

[0013] Preferably, the UV irradiance of the photopolymerization reaction is 80 W·cm. -1 The time is 3 minutes; the photopolymerization reaction is carried out under vacuum conditions.

[0014] This invention utilizes the intermolecular interactions between strongly polar monomers (monofunctional acrylate reactive functional monomers) and weakly polar monomers (monofunctional acrylate reactive diluents) to promote the regular arrangement of chain segments, increasing the content and size of microregions formed by the alkyl side chains of the monofunctional acrylate reactive diluents in the elastomer network, thereby reducing the intrinsic viscoelasticity of the polymer. This invention changes the previous understanding that strongly polar groups increase viscoelasticity, and obtains an advanced acrylate dielectric elastomer with low mechanical loss, fast response speed, and low strain drift, significantly improving dynamic driving response characteristics and broadening its application in the field of dielectric elastomer flexible devices.

[0015] Furthermore, the present invention achieves control over viscoelasticity by adjusting the distance between the strongly polar groups (i.e., the polar groups in the monofunctional acrylate active functional monomers) in the strongly polar monomers and the main chain, as well as the content of the strongly polar monomers in the crosslinking network. Attached Figure Description

[0016] Figure 1 This is a comparison of the low-strain drift acrylate dielectric elastomer network structure, the chain segment rearrangement process after deformation, and the mechanical loss in Example 1. Figure 2 The WAXS curves of the dielectric elastomers of Examples 1-2 and Comparative Examples 1-2 are shown. Figure 3 The infrared spectra of the dielectric elastomers of Examples 1-2 and Comparative Examples 1-2 are shown below. Figure 4 The driving deformation of the dielectric elastomer under square wave voltage in Example 1 and Comparative Example 1 are shown. Detailed Implementation

[0017] This invention provides a low-strain-drift acrylate dielectric elastomer, comprising the following raw materials by mass fraction: Bifunctional aliphatic polyurethane acrylate 20~35%; Monofunctional acrylate reactive diluent 15~69%; Monofunctional acrylate active functional monomers: 10-60%; Photoinitiator 0.4~1%; The monofunctional acrylate reactive diluent includes a side chain, and the substituents of the side chain include alkyl groups; The polar groups in the monofunctional acrylate active functional monomer include one or more of hydroxyl, carboxyl, and amino groups.

[0018] By mass fraction, the raw materials for preparing the low-strain drift acrylate dielectric elastomer of the present invention include 20-35% bifunctional aliphatic polyurethane acrylate, which in specific embodiments of the present invention can be 21%, 22%, 23%, 24%, 25%, 26%, 27%, 28%, 29%, 30%, 31%, 32%, 33%, or 34%; the molecular weight of the bifunctional aliphatic polyurethane acrylate is preferably 10. 4 ~10 5 The bifunctional aliphatic polyurethane acrylate, in g / mol form, preferably includes CN9021NS produced by Sartoma Guangzhou Chemical Co., Ltd. The bifunctional aliphatic polyurethane acrylate serves as a crosslinking agent.

[0019] By mass fraction, the raw materials for preparing the low-strain drift acrylate dielectric elastomer of the present invention include 15-69% monofunctional acrylate reactive diluent, which in specific embodiments of the present invention can be 16%, 17%, 18%, 19%, 20%, 21%, 22%, 23%, 24%, 25%, 26%, 27%, 28%, 29%, 30%, 31%, 32%, 33%, 34%, 35%, 36%, 37%, 38%, 39%, 40%, 41%, 42%, 43%, 44%, 45%, 46%, 47%, 48%, 49%, 50%, 51%, 52%, and 53%. 54%, 55%, 56%, 57%, 58%, 59%, 60%, 61%, 62%, 63%, 64%, 65%, 66%, 67%, 68%, or 69%; the monofunctional acrylate reactive diluent preferably includes alkyl methacrylate and / or alkyl acrylate; the alkyl methacrylate preferably includes one or more of undecyl methacrylate, dodecyl methacrylate, tridecyl methacrylate, and tetradecyl methacrylate; the alkyl acrylate preferably includes one or more of decyl acrylate, dodecyl acrylate, tridecyl acrylate, and tetradecyl acrylate.

[0020] By mass fraction, the raw materials for preparing the low strain drift acrylate dielectric elastomer of the present invention include 10-60% of monofunctional acrylate active functional monomers. In specific embodiments of the present invention, these can be 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20%, 21%, 22%, 23%, 24%, 25%, 26%, 27%, 28%, 29%, 30%, 31%, 32%, 33%, 34%, 35%, 36%, 37%, 38%, 39%, 40%, 41%, 42%, 43%, 44%, 45%, 46%, 47%, 48%, 49%, 50%, 51%, 52%, 53%, 54%, 55%, 56%, 57%, 58%, or 59%. The monofunctional acrylate active functional monomers preferably include one or more of hydroxyethyl acrylate, hydroxypropyl acrylate, 2-carboxyethyl acrylate, and hydroxybutyl acrylate.

[0021] The raw materials for preparing the low strain drift acrylate dielectric elastomer of the present invention, by mass fraction, include 0.4-1% photoinitiator, which in specific embodiments of the present invention can be 0.5%, 0.6%, 0.7%, 0.8%, or 0.9%. The photoinitiator preferably includes a free radical photoinitiator, which preferably includes one or more of benzoyl, α,α-diethoxyacetophenone, 2-hydroxy-2-methyl-1-phenyl-1-propanone, 1-hydroxy-cyclohexylbenzophenone, and 2-methyl-2-(4-morpholino)-1-[4-(methylthio)phenyl]-1-propanone.

[0022] The present invention also provides a method for preparing the low strain drift acrylate dielectric elastomer described in the above technical solution, comprising the following steps: The raw materials for preparing the low strain drift acrylate dielectric elastomer are mixed and then subjected to photopolymerization to obtain the low strain drift acrylate dielectric elastomer.

[0023] In this invention, the mixing process preferably further includes: injecting the resulting mixture into a mold and then drawing a vacuum.

[0024] In this invention, the UV irradiance for the photopolymerization reaction is preferably 80 W·cm⁻¹. -1 The preferred time is 3 minutes; the photopolymerization reaction is preferably carried out under vacuum conditions.

[0025] The following detailed description of the low strain drift acrylate dielectric elastomer and its preparation method provided by the present invention, with reference to specific embodiments, should not be construed as limiting the scope of protection of the present invention.

[0026] Example 1 A low-strain-drift acrylate dielectric elastomer, the preparation process of which is as follows: Weigh out 66.96% LA, 10.33% HEA, 22.26% CN9021NS, and 0.45% photoinitiator 1173 by mass fraction, mix them evenly using a vortex mixer to form a prepolymer, inject it into a special glass mold, evacuate it to a vacuum of 133 Pa for 15 min, and then expose it to UV irradiation of 80 W·cm². -1 Photocuring is completed after 3 minutes of ultraviolet light irradiation.

[0027] Example 2 A low-strain-drift acrylate dielectric elastomer, the preparation process of which is as follows: Weigh out 65.33% LA, 12.52% HBA, 21.72% CN9021NS, and 0.43% photoinitiator 1173 by mass, mix them thoroughly using a vortex mixer to form a prepolymer, inject it into a special glass mold, evacuate to a vacuum of 133 Pa for 15 min, and then expose it to UV irradiation of 80 W·cm². -1 Photocuring is completed after 3 minutes of ultraviolet light irradiation.

[0028] Example 3 Weigh out 46.31% LA, 28.57% HEA, 24.63% CN9021NS, and 0.49% photoinitiator 1173 by mass fraction, mix them evenly using a vortex mixer to form a prepolymer, inject it into a special glass mold, evacuate it to a vacuum of 133 Pa for 15 min, and then expose it to UV irradiation of 80 W·cm². -1 Photocuring is completed after 3 minutes of ultraviolet light irradiation.

[0029] Example 4 Weigh out 43.32% LA, 33.18% HBA, 23.04% CN9021NS, and 0.46% photoinitiator 1173 by mass, mix them thoroughly using a vortex mixer to form a prepolymer, inject it into a special glass mold, evacuate to a vacuum of 133 Pa for 15 min, and expose it to UV irradiation of 80 W·cm². -1 Photocuring is completed after 3 minutes of ultraviolet light irradiation.

[0030] Example 5 Weigh out 20.73% LA, 51.16% HEA, 27.56% CN9021NS, and 0.55% photoinitiator 1173 by mass fraction, mix them evenly using a vortex mixer to form a prepolymer, inject it into a special glass mold, evacuate it to a vacuum of 133 Pa for 15 min, and then expose it to UV irradiation of 80 W·cm². -1 Photocuring is completed after 3 minutes of ultraviolet light irradiation.

[0031] Example 6 Weigh out 18.45% LA, 56.53% HBA, 24.53% CN9021NS, and 0.49% photoinitiator 1173 by mass fraction, mix them evenly using a vortex mixer to form a prepolymer, inject it into a special glass mold, evacuate to a vacuum degree of 133 Pa for 15 min, and expose it to UV irradiation of 80 W·cm². -1 Photocuring is completed after 3 minutes of ultraviolet light irradiation.

[0032] Comparative Example 1 Weigh out 78.66% LA, 20.92% CN9021NS, and 0.42% photoinitiator 1173 by mass, mix them thoroughly using a vortex mixer to form a prepolymer, inject it into a special glass mold, evacuate to a vacuum of 133 Pa for 15 min, and then expose it to UV irradiation of 80 W·cm². -1 Photocuring is completed after 3 minutes of ultraviolet light irradiation.

[0033] Comparative Example 2 Weigh out 69.64% LA, 6.70% AA (acrylic acid), 23.20% CN9021NS, and 0.46% photoinitiator 1173 by mass fraction, mix them evenly using a vortex mixer to form a prepolymer, inject it into a special glass mold, evacuate it to a vacuum of 133 Pa for 15 min, and then expose it to UV irradiation of 80 W·cm². -1 Photocuring is completed after 3 minutes of ultraviolet light irradiation.

[0034] Comparative Example 3 Commercial acrylate elastomer 3MTM VHB4910.

[0035] Comparative Example 4 Weigh out 69.46% HEA, 29.94% CN9021NS, and 0.6% photoinitiator 1173 by mass, mix them thoroughly using a vortex mixer to form a prepolymer, inject it into a special glass mold, evacuate to a vacuum of 133 Pa for 15 min, and then expose it to UV irradiation of 80 W·cm². -1 Photocuring is completed after 3 minutes of ultraviolet light irradiation.

[0036] Figure 1 This is a comparison of the low-strain drift acrylate dielectric elastomer network structure, the chain segment rearrangement process after deformation, and the mechanical loss in Example 1.

[0037] Depend on Figure 1 As shown, during deformation of a dielectric elastomer, the internal molecular chain motion lags behind the external mechanical force, generating internal stress. Due to the thermal motion of the chain segments adjusting the molecular conformation, the internal stress is gradually eliminated, and the molecular chain conformation transitions to a steady state; this process is called chain segment rearrangement. Under cyclic stretching, the chain segment rearrangement eliminates internal stress, causing the stress-strain curves of the stretching and shrinking processes to not overlap. Compared to Comparative Example 1, through copolymerization with a strongly polar monomer (Example 1), the microregions within the dielectric elastomer can serve as physical crosslinking points, acting as "anchor points" during network deformation, reducing chain segment adjustment, accelerating the molecular chain to a steady state, reducing mechanical loss, and significantly suppressing viscoelasticity.

[0038] The properties of the dielectric elastomers in Examples 1-6 and Comparative Examples 1-4 are shown in Table 1.

[0039] Table 1 Performance parameters of dielectric elastomers in Examples 1-6 and Comparative Examples 1-4

[0040] Wherein, the cyclic tensile mechanical loss is the ratio of the mechanical loss work to the absorbed work per unit volume of elastic body, that is: Where σ is stress, λ is strain, and λ max This is the maximum strain value set during the test.

[0041] Examples 1, 3, and 5 use HEA as the strongly polar functional monomer, while Examples 2, 4, and 6 use HBA as the strongly polar functional monomer. Comparative Example 1 contains no functional monomer, and Comparative Example 2 uses AA as the strongly polar functional monomer. The mechanical loss factor (tan...) is compared. δ m The mechanical losses during 100% cyclic stretching and analysis show that the addition of HEA and HBA reduces losses, while AA increases them, and HEA is more effective than HBA. When the content of HEA and HBA increases, the effect of inhibiting viscoelasticity decreases slightly; however, if the HEA content reaches nearly 70% (Comparative Example 4), not only does the modulus increase significantly, but the losses also exceed those of Examples 1-6. This indicates that the effect of inhibiting viscoelasticity is related to the position and content of the strongly polar groups.

[0042] Figure 2 The WAXS curves of the dielectric elastomers of Examples 1-2 and Comparative Examples 1-2 are shown.

[0043] Figure 3 The infrared spectra of the dielectric elastomers of Examples 1-2 and Comparative Examples 1-2 are shown.

[0044] For WAXS maps ( Figure 2 After peak separation, the peaks can be divided into three peaks, named as follows: 1. The diffraction peak with 2theta≈20° is an amorphous peak and is uniformly named I; 2. The sharp diffraction peak with 2theta≈4° and a very narrow half-width is considered as a relatively regular micro-region, which can play a role in physical cross-linking and is uniformly named II. The size of the micro-region can be calculated by Bragg's formula based on the position of the peak center. The smaller the peak center, the larger the micro-region size; 3. The third peak in the middle, when its half-width is greater than 5°, is considered an amorphous diffraction peak and is named I'. Otherwise, it is considered a diffraction peak of a sub-regular micro-region and is named II'.

[0045] The WAXS test results show that: 1. The homopolymer network of Comparative Example 1 contains a small amount (12.79%) of nanoscale microphases with a size of approximately 2.15 nm, which is composed of the long alkyl side chains (-C) of LA. 12 H 251) This is caused by the locally ordered arrangement; 2) The introduction of highly polar monomers reduces the content of amorphous structures and increases the content of ordered microregions in the dielectric elastomer to a certain extent, which helps to suppress mechanical loss and strain drift; 3) Compared with LA homopolymers and other copolymers, the copolymer of Example 1 has the highest content and the largest size (the center of peak I is the smallest, corresponding to a microregion size of 2.45). The size and content of well-ordered microregions (nm) in the copolymer network are closely related to the distance between the strongly polar group on the strongly polar monomer and the main chain (i.e., its position on the side chain). This is because when the strongly polar group is too close to the main chain, such as in Comparative Example 2, the ester group on AA and LA will interfere with the influence of the strongly polar group on the conformation of the alkyl side chain. When the strongly polar group is too far from the main chain, such as in Example 2, the influence of the strongly polar group on the conformation of the alkyl side chain can only act on the terminal part of the chain segment. When the distance between the strongly polar group and the main chain is appropriate, such as in HEA (Example 1), the influence of the strongly polar group on the conformation of the alkyl side chain can act on a longer chain segment range, maximizing the promotion of the well-ordered arrangement of the molecular chain.

[0046] Infrared spectroscopy ( Figure 3 This confirmed the molecular interaction between strongly polar monomers and weakly polar monomers. Stronger intermolecular interactions also increase mechanical loss, as seen in Comparative Example 2. However, the intermolecular forces in Example 2 are relatively weak. Although the increase in micro-regions is not significant, the negative impact of increased mechanical loss due to intermolecular forces is also smaller, resulting in lower overall mechanical loss.

[0047] Figure 4 The driving deformation of the dielectric elastomer under square wave voltage in Example 1 and Comparative Example 1 are shown.

[0048] Compared with Comparative Example 1, Example 1 has a more stable drive deformation cycle and lower drive deformation drift.

[0049] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A low-strain-drift acrylate dielectric elastomer, characterized in that, The following raw materials are included by mass fraction: Bifunctional aliphatic polyurethane acrylate 20~35%; Monofunctional acrylate reactive diluent 15~69%; Monofunctional acrylate active functional monomers: 10-60%; Photoinitiator 0.4~1%; The monofunctional acrylate reactive diluent includes a side chain, and the substituents of the side chain include alkyl groups; The polar groups in the monofunctional acrylate active functional monomer include one or more of hydroxyl, carboxyl, and amino groups.

2. The low strain drift acrylate dielectric elastomer according to claim 1, characterized in that, The molecular weight of the bifunctional aliphatic polyurethane acrylate is 10. 4 ~10 5 g / mol.

3. The low strain drift acrylate dielectric elastomer according to claim 1 or 2, characterized in that, The bifunctional aliphatic polyurethane acrylate includes CN9021NS produced by Sartoma Guangzhou Chemical Co., Ltd.

4. The low strain drift acrylate dielectric elastomer according to claim 1, characterized in that, The monofunctional acrylate reactive diluent includes alkyl methacrylates and / or alkyl acrylates.

5. The low strain drift acrylate dielectric elastomer according to claim 4, characterized in that, The alkyl methacrylates include one or more of undecyl methacrylate, dodecyl methacrylate, tridecyl methacrylate, and tetradecyl methacrylate; The alkyl acrylates include one or more of decyl acrylate, dodecyl acrylate, tridecyl acrylate, and tetradecyl acrylate.

6. The low strain drift acrylate dielectric elastomer according to claim 1, characterized in that, The monofunctional acrylate active functional monomers include one or more of hydroxyethyl acrylate, hydroxypropyl acrylate, 2-carboxyethyl acrylate, and hydroxybutyl acrylate.

7. The low strain drift acrylate dielectric elastomer according to claim 1, characterized in that, The photoinitiator includes a free radical photoinitiator.

8. The low strain drift acrylate dielectric elastomer according to claim 7, characterized in that, The free radical photoinitiator includes one or more of benzoyl, α,α-diethoxyacetophenone, 2-hydroxy-2-methyl-1-phenyl-1-propanone, 1-hydroxy-cyclohexylbenzophenone, and 2-methyl-2-(4-morpholino)-1-[4-(methylthio)phenyl]-1-propanone.

9. A method for preparing the low-strain drift acrylate dielectric elastomer according to any one of claims 1 to 8, characterized in that, Includes the following steps: The raw materials for preparing the low strain drift acrylate dielectric elastomer are mixed and then subjected to photopolymerization to obtain the low strain drift acrylate dielectric elastomer.

10. The preparation method according to claim 9, characterized in that, The UV irradiance for the photopolymerization reaction is 80 W·cm. -1 The time is 3 minutes; the photopolymerization reaction is carried out under vacuum conditions.

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