Bio-based dual-dynamic network polymer as well as preparation method and application thereof

Abstract

The invention provides a bio-based dual-dynamic network polymer as well as a preparation method and application thereof. The preparation method comprises the following steps: S1, mixing an epoxy monomer, binary acid, graphene and a transesterification catalyst, and heating for polymerization reaction to obtain a prepolymer; wherein the epoxy monomer comprises polyethylene glycol diglycidyl ether and glycerol triglycidyl ether, and the binary acid comprises sebacic acid, 2, 5-furandicarboxylic acid and 2, 2 '-dithiodibenzoic acid; and S2, removing bubbles from the obtained prepolymer, and then carrying out thermocuring to obtain the bio-based dual-dynamic network polymer. The bio-based dual-dynamic network polymer obtained by the invention has good mechanical properties, hydrophobicity, solvent resistance, alkali recoverability, self-healing and shape memory properties, and has certain application potential in the fields of intelligent actuators and flexible sensors.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of intelligent polymers, in particular to a bio-based double dynamic network polymer and a preparation method and application thereof. BACKGROUND

[0002] Thermosetting materials with three-dimensional network structure play a key role in aerospace, automotive, electronics and construction industries due to their high mechanical strength, good thermal stability and good chemical resistance. However, due to their three-dimensional network structure, they cannot be remolded, repaired or recycled, which not only shortens their service life, but also leads to a large amount of resin waste and pollution from incineration or landfill treatment. In the context of increasing attention to sustainable development and environmental protection, the development of materials derived from renewable resources has become an important research direction.

[0003] In order to solve the problem of difficult recycling and self-repairing of traditional epoxy resin, some researchers introduce dynamic covalent bonds into thermosetting materials. Dynamic network polymers can respond to specific stimuli (such as light, heat, pH) to exchange and reorganize, which not only maintains the high performance of thermosetting materials, but also has the remoldability similar to thermoplastic materials. This characteristic has stimulated extensive research on the self-healing, reprocessing and structure remodeling of cross-linked polymers. However, existing bio-based dynamic polymers still have some problems that need to be solved, such as relying on a single type of dynamic covalent bond (such as ester bond or disulfide bond), which is difficult to balance mechanical strength, environmental stability (such as solvent resistance) and functional plasticity (such as self-healing and shape memory), limiting their application in intelligent devices with high comprehensive performance requirements. Therefore, it is urgent to develop a bio-based polymer system with multiple dynamic network synergistic effects to improve the existing problems of mechanical properties, environmental adaptability and functional application of materials. SUMMARY

[0004] In view of the problems existing in the prior art, the present application provides a bio-based double dynamic network polymer and a preparation method and application thereof. The bio-based double dynamic network polymer has good mechanical properties, hydrophobicity, solvent resistance, alkali recyclability, self-healing and shape memory performance, and has certain application potential in the field of intelligent actuators and flexible sensors.

[0005] The present application is realized by the following technical solutions: In a first aspect, the present application provides a preparation method of a bio-based double dynamic network polymer, comprising: S1, mixing epoxy monomers, dibasic acid, graphene (Gr) and transesterification catalyst, and heating to carry out polymerization reaction to obtain a prepolymer; wherein the epoxy monomers include polyethylene glycol diglycidyl ether (PEGDE) and glycerol triglycidyl ether (GTE), and the dibasic acid includes sebacic acid (SA), 2,5-furan dicarboxylic acid (FDCA) and 2,2'-dithiodibenzoic acid (DTSA); S2, removing bubbles from the obtained prepolymer, and then performing heat curing to obtain the bio-based double dynamic network polymer.

[0006] In some preferred embodiments of the present application, the molar ratio of the epoxy groups in the epoxy monomers to the carboxyl groups in the dibasic acid is 1: (0.5-1.5).

[0007] In some preferred embodiments of the present application, the molar ratio of the polyethylene glycol diglycidyl ether to the glycerol triglycidyl ether is (9-1):(1-9), more preferably (5-7):(3-5).

[0008] In some preferred embodiments of the present application, the molar ratio of the sebacic acid, 2,5-furan dicarboxylic acid and 2,2'-dithiodibenzoic acid is (4-4.75):(4-4.75):(2-0.5).

[0009] In some preferred embodiments of the present application, the mass of the graphene is 5wt%-25wt% of the total mass of the epoxy monomers and the dibasic acid, more preferably 5wt%-10wt%.

[0010] In some preferred embodiments of the present application, the transesterification catalyst is triphenylphosphine or 1,5,7-triazabicyclo[4.4.0]dec-5-ene.

[0011] In some preferred embodiments of the present application, the temperature of the polymerization reaction is 90-120℃, and the time is 40-60 min.

[0012] In some preferred embodiments of the present application, the method for removing bubbles is: reacting the obtained prepolymer in a vacuum oven at 100-120℃ for 10-30 min to remove bubbles.

[0013] In some preferred embodiments of the present application, the heat curing is specifically: curing at 120-130℃ for 2-4 h, and then curing at 140-160℃ for 6-8 h.

[0014] In a second aspect, the present application provides a bio-based double dynamic network polymer obtained by the preparation method described above.

[0015] In a third aspect, the present application provides an application of the bio-based double dynamic network polymer in the field of intelligent actuators and flexible sensors.

[0016] Compared with the prior art, the present application has the following advantages: The present application uses biomass-derived monomers (glycerol triglycidyl ether, sebacic acid and 2,5-furan dicarboxylic acid) and biocompatible monomers (polyethylene glycol diglycidyl ether, 2,2'-dithiodibenzoic acid) and graphene as raw materials to prepare a bio-based double dynamic network polymer. The bio-based double dynamic network polymer system takes epoxy-carboxyl ring-opening polymerization as the core reaction mechanism. Polyethylene glycol diglycidyl ether provides double epoxy groups to construct the basic segment, which can be used as a linear epoxy monomer. Glycerol triglycidyl ether forms a branched structure through a triple epoxy group to improve the crosslinking degree and can be used as an epoxy branched monomer. The long-chain carboxyl group of sebacic acid can be used as a flexible monomer to toughen. The furan ring of 2,5-furan dicarboxylic acid can enhance the strength and thermal stability and can be used as a rigid monomer. 2,2'-dithiodibenzoic acid can impart self-repairing and recyclable dynamic functions to the material through the reversible breaking and recombination of disulfide bonds and can be used as a dynamic covalent monomer. The above-mentioned monomers are co-reacted, the carboxyl group attacks the epoxy ring to open the ring, and the newly generated hydroxyl group continues to react to form a polymer mainly connected by ester bonds and disulfide bonds. At the same time, graphene (nanofunctional filler) is uniformly dispersed in the matrix to further strengthen the mechanical strength and electrical conductivity of the material, and finally a bio-based double dynamic network polymer with coordinated structure and function is formed. The structure is shown in Figure 1 The bio-based double dynamic network polymer obtained by the present application contains two dynamic covalent bonds, hydroxyl-ester bond and disulfide bond. The hydroxyl-ester bond can impart the polymer with structural stability and controllable long-term shape retention ability through slow ester exchange reaction. The disulfide bond can provide efficient damage repair and recyclable dynamic functions through fast disulfide exchange. Compared with a single dynamic covalent bond, the combination of the two can achieve balanced performance (hydroxyl-ester bond ensures long-term stability, and disulfide bond responds to sudden damage) and more flexible function design, breaking through the limitations of single dynamic covalent bond in stability and function dimension. The bio-based double dynamic network polymer described in the present application has good comprehensive performance. The synergistic effect of the structures of each monomer and the graphene filler, and the stable three-dimensional network constructed by the synergistic effect of hydroxyl-ester bond and disulfide bond together impart the material with good mechanical properties (tensile strength of 12.140 MPa, elongation at break of 102.331%); the crosslinked and dense network structure can reduce water molecule adsorption and hinder solvent molecule penetration, thereby achieving good hydrophobicity (hydrophobic angle of 127.2°) and solvent resistance; the hydroxyl-ester bond is easily hydrolyzed and broken under alkaline conditions, making the network depolymerizable and recyclable, and the performance can be restored by polymerization and recombination, realizing alkaline recyclability; the reversible nature of disulfide bond and hydroxyl-ester bond enables the broken bonds to recombine under heating conditions, the network structure self-repairs, and the molecular chain segments change in movement ability under stimulation, the dynamic bond recombination fixes the new shape, imparting self-healing and shape memory properties. The use of bio-based raw materials in the present application also meets the green and environmentally friendly development concept.

[0017] The bio-based double dynamic network polymer prepared by the application can be further made into an intelligent gripper and a strain sensor through simple assembly. The intelligent gripper can realize precise grasping operation on a target object relying on its shape memory effect, and its grasping function can be performed in a hot water environment (90-100℃), which can efficiently complete the grasping and transferring task of objects in the temperature range. As a strain sensor, the strain index GF=8.13, the response time is 1.865 s, the stability is greater than 1000 bending strain cycles, and it can be successfully applied to the motion detection of joints such as human neck, elbow, ankle, wrist, finger and knee. The bio-based double dynamic network polymer has certain application potential in the field of intelligent actuators and flexible sensors. BRIEF DESCRIPTION OF DRAWINGS

[0018] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the drawings needed to be used in the embodiments or prior art description will be briefly introduced. Obviously, the drawings in the following description are some embodiments of the present application, and other drawings can also be obtained by those skilled in the art without creative labor.

[0019] Figure 1 The structure diagram of the bio-based double dynamic network polymer.

[0020] Figure 2 The Fourier transform infrared spectrum of the bio-based double dynamic network polymer in Example 3; Figure 3 The bio-based double dynamic network polymer in Example 3 1 H-NMR spectrum (deuterated DMSO).

[0021] Figure 4 The stress-strain of the bio-based double dynamic network polymer in Example 3.

[0022] Figure 5 The water contact angle of the bio-based double dynamic network polymer in Example 3.

[0023] Figure 6 The solvent resistance of the bio-based double dynamic network polymer in Example 3.

[0024] Figure 7 The alkali recyclability of the bio-based double dynamic network polymer in Example 3.

[0025] Figure 8 The self-healing property of the bio-based double dynamic network polymer in Example 3.

[0026] Figure 9To implement shape memory of the bio-based dual dynamic network polymer in Example 3.

[0027] Figure 10 To implement application of the bio-based dual dynamic network polymer in Example 3 as a smart gripper.

[0028] Figure 11 To implement application of the bio-based dual dynamic network polymer in Example 3 as a strain sensor. DETAILED DESCRIPTION

[0029] The present application is herein described, by way of example only, with the comprehension that the advantages and utility thereof are not limited to specific embodiments described or suggested herein, but extend to whatever falls within the scope of the application. The present application can be implemented or applied in other different embodiments, and the details in the specification can be modified or changed based on different views and applications without departing from the spirit of the present application.

[0030] It should be noted that the process equipment or device not specifically mentioned in the following examples is the conventional equipment or device in the art.

[0031] It should be noted that the terms "comprising" and "having" and any variations thereof are intended to cover non-exclusive inclusions, for example, a process, method, system, product or device comprising a series of steps or units does not have to be limited to those steps or units clearly listed, but can include other steps or units not clearly listed or inherent to these processes, methods, products or devices. Moreover, unless otherwise specified, the numbering of each method step is only a convenient tool for identifying each method step, and is not a limitation on the arrangement order of each method step or a limitation on the scope of the implementation of the present application. Changes or adjustments of the relative relationship, without substantial changes in the technical content, are also considered as the scope of the implementation of the present application.

[0032] Example 1 (1) The epoxy monomer and the dibasic acid are prepared according to the molar ratio of the epoxy group in the epoxy monomer to the carboxyl group in the dibasic acid being 1:0.5. Among them, the epoxy monomer includes polyethylene glycol diglycidyl ether and glycerol triglycidyl ether, and the molar ratio of the two is 9:1; the dibasic acid includes sebacic acid, 2,5-furandicarboxylic acid and 2,2'-dithiodibenzoic acid, and the molar ratio of the three is 4:4:2. The graphene is prepared according to 5wt% of the total mass of the epoxy monomer and the dibasic acid. The above raw materials are mixed and 0.5wt% of the total mass of the epoxy monomer and the dibasic acid is added to the transesterification catalyst (1,5,7-triazabicyclo[4.4.0]dec-5-ene), heated and stirred at 90°C for 40 min to carry out the polymerization reaction.

[0033] (2) The mixture obtained in step (1) was placed in a vacuum oven at 100 °C for 10 min to remove bubbles.

[0034] (3) The mixture obtained in step (2) was loaded into a polytetrafluoroethylene mold and placed in an oven, cured at 120 °C for 2 h, and then cured at 140 °C for 6 h to obtain a bio-based double dynamic network polymer. The tensile strength thereof was 6.107 MPa, the elongation at break was 66.277%, and the hydrophobic angle was 117.2°.

[0035] (4) The bio-based double dynamic network polymer obtained in step (3) was further made into an intelligent gripper and a strain sensor through simple assembly.

[0036] Example 2 (1) The epoxy monomer and the dibasic acid were prepared according to a molar ratio of epoxy groups in the epoxy monomer to carboxyl groups in the dibasic acid of 1:0.5. The epoxy monomer included polyethylene glycol diglycidyl ether and glycerol triglycidyl ether, and the molar ratio of the two was 1:9; the dibasic acid included sebacic acid, 2,5-furan dicarboxylic acid, and 2,2'-dithiodibenzoic acid, and the molar ratio of the three was 4.75:4.75:0.5. Graphene was prepared according to 10wt% of the total mass of the epoxy monomer and the dibasic acid. The above raw materials were mixed and 1wt% of the total mass of the epoxy monomer and the dibasic acid of ester exchange catalyst (triphenylphosphine) was added, heated and stirred at 100 °C for 50 min to perform a polymerization reaction.

[0037] (2) The mixture obtained in step (1) was placed in a vacuum oven at 110 °C for 20 min to remove bubbles.

[0038] (3) The mixture obtained in step (2) was loaded into a polytetrafluoroethylene mold and placed in an oven, cured at 125 °C for 3 h, and then cured at 150 °C for 7 h to obtain a bio-based double dynamic network polymer. The tensile strength thereof was 15.072 MPa, the elongation at break was 43.601%, and the hydrophobic angle was 125.8°.

[0039] (4) The bio-based double dynamic network polymer obtained in step (3) was further made into an intelligent gripper and a strain sensor through simple assembly.

[0040] Example 3 (1) The epoxy monomer and the dibasic acid are prepared according to a molar ratio of epoxy groups in the epoxy monomer to carboxyl groups in the dibasic acid of 1:1. The epoxy monomer includes polyethylene glycol diglycidyl ether and glycerol triglycidyl ether, and the molar ratio of the two is 7:3; the dibasic acid includes sebacic acid, 2,5-furan dicarboxylic acid, and 2,2'-dithiodibenzoic acid, and the molar ratio of the three is 4.375:4.375:1.25. The graphene, a nano filler, is prepared according to 10 wt% of the total mass of the epoxy monomer and the dibasic acid. The above raw materials are mixed and an ester exchange catalyst (triphenylphosphine) with a mass of 1 wt% of the total mass of the epoxy monomer and the dibasic acid is added, and the mixture is heated and stirred at 120°C for 40 min to perform a polymerization reaction.

[0041] (2) The mixture obtained in step (1) is placed in a vacuum oven at 120°C for 30 min to remove bubbles.

[0042] (3) The mixture obtained in step (2) is loaded into a polytetrafluoroethylene mold and placed in an oven, and cured at 120°C for 2 h and then at 160°C for 8 h to obtain a bio-based double dynamic network polymer. The tensile strength thereof is 12.140 MPa, the elongation at break is 102.331%, and the hydrophobic angle is 127.2°.

[0043] (4) The bio-based double dynamic network polymer obtained in step (3) is further made into an intelligent gripper and a strain sensor through simple assembly.

[0044] Example 4 (1) The epoxy monomer and the dibasic acid are prepared according to a molar ratio of epoxy groups in the epoxy monomer to carboxyl groups in the dibasic acid of 1:1. The epoxy monomer includes polyethylene glycol diglycidyl ether and glycerol triglycidyl ether, and the molar ratio of the two is 7:3; the dibasic acid includes sebacic acid, 2,5-furan dicarboxylic acid, and 2,2'-dithiodibenzoic acid, and the molar ratio of the three is 4.375:4.375:1.25. The graphene, a nano filler, is prepared according to 25 wt% of the total mass of the epoxy monomer and the dibasic acid. The above raw materials are mixed and an ester exchange catalyst (1,5,7-triazabicyclo[4.4.0]dec-5-ene) with a mass of 1 wt% of the total mass of the epoxy monomer and the dibasic acid is added, and the mixture is heated and stirred at 120°C for 60 min to perform a polymerization reaction.

[0045] (2) The mixture obtained in step (1) is placed in a vacuum oven at 120°C for 20 min to remove bubbles.

[0046] (3) The mixture obtained in step (2) was loaded into a polytetrafluoroethylene mold and placed in an oven for curing at 130 °C for 2 h and post-curing at 160 °C for 8 h to obtain a bio-based double dynamic network polymer. Its tensile strength was 14.683 MPa, elongation at break was 48.724%, and hydrophobic angle was 120.5°.

[0047] (4) The bio-based double dynamic network polymer obtained in step (3) was further made into intelligent gripper and strain sensor through simple assembly.

[0048] Example 5 (1) The epoxy monomer and the dibasic acid were prepared according to a molar ratio of epoxy groups in the epoxy monomer to carboxyl groups in the dibasic acid of 1:1. The epoxy monomer included polyethylene glycol diglycidyl ether and glycerol triglycidyl ether, and the molar ratio of the two was 1:9; the dibasic acid included sebacic acid, 2,5-furandicarboxylic acid, and 2,2'-dithiodibenzoic acid, and the molar ratio of the three was 4.75:4.75:0.5. The graphene was prepared according to 15 wt% of the total mass of the epoxy monomer and the dibasic acid. The above raw materials were mixed and 1 wt% of the total mass of the epoxy monomer and the dibasic acid of transesterification catalyst (1,5,7-triazabicyclo[4.4.0]dec-5-ene) was added, heated and stirred at 120 °C for 60 min to carry out the polymerization reaction.

[0049] (2) The mixture obtained in step (1) was placed in a vacuum oven at 120 °C for 20 min to remove bubbles.

[0050] (3) The mixture obtained in step (2) was loaded into a polytetrafluoroethylene mold and placed in an oven for curing at 130 °C for 3 h and post-curing at 160 °C for 7 h to obtain a bio-based double dynamic network polymer. Its tensile strength was 17.518 MPa, elongation at break was 23.580%, and hydrophobic angle was 123.9°.

[0051] (4) The bio-based double dynamic network polymer obtained in step (3) was further made into intelligent gripper and strain sensor through simple assembly.

[0052] Example 6 (1) Epoxy monomers and dibasic acids were prepared according to a molar ratio of epoxy groups in the epoxy monomers to carboxyl groups in the dibasic acids of 1:1.5. The epoxy monomers included polyethylene glycol diglycidyl ether and glycerol triglycidyl ether at a molar ratio of 1:9, and the dibasic acids included sebacic acid, 2,5-furan dicarboxylic acid, and 2,2'-dithiodibenzoic acid at a molar ratio of 4.5:4.5:1. Graphene, a nano-filler, was prepared at 20 wt% of the total mass of the epoxy monomers and the dibasic acids. The above raw materials were mixed and an ester exchange catalyst (triphenylphosphine) was added at 1.5 wt% of the total mass of the epoxy monomers and the dibasic acids. The mixture was heated and stirred at 110 °C for 50 min to perform a polymerization reaction.

[0053] (2) The mixture obtained in step (1) was placed in a vacuum oven at 110 °C for 30 min to remove air bubbles.

[0054] (3) The mixture obtained in step (2) was loaded into a polytetrafluoroethylene mold and placed in an oven for curing at 130 °C for 4 h and then at 160 °C for 6 h to obtain a bio-based double dynamic network polymer. The tensile strength of the polymer was 10.655 MPa, the elongation at break was 24.515%, and the hydrophobic angle was 115.8°.

[0055] (4) The bio-based double dynamic network polymer obtained in step (3) was further made into a smart gripper and a strain sensor through simple assembly.

[0056] Example 7 (1) Epoxy monomers and dibasic acids were prepared according to a molar ratio of epoxy groups in the epoxy monomers to carboxyl groups in the dibasic acids of 1:1.5. The epoxy monomers included polyethylene glycol diglycidyl ether and glycerol triglycidyl ether at a molar ratio of 5:5, and the dibasic acids included sebacic acid, 2,5-furan dicarboxylic acid, and 2,2'-dithiodibenzoic acid at a molar ratio of 4:4:2. Graphene, a nano-filler, was prepared at 5 wt% of the total mass of the epoxy monomers and the dibasic acids. The above raw materials were mixed and an ester exchange catalyst (1,5,7-triazabicyclo[4.4.0]dec-5-ene) was added at 1 wt% of the total mass of the epoxy monomers and the dibasic acids. The mixture was heated and stirred at 100 °C for 40 min to perform a polymerization reaction.

[0057] (2) The mixture obtained in step (1) was placed in a vacuum oven at 110 °C for 30 min to remove air bubbles.

[0058] (3) The mixture obtained in step (2) was loaded into a polytetrafluoroethylene mold and placed in an oven for curing at 125 °C for 3 h and then at 150 °C for 7 h to obtain a bio-based double dynamic network polymer. The tensile strength thereof was 6.327 MPa, the elongation at break was 70.806%, and the hydrophobic angle was 116.1°.

[0059] (4) The bio-based double dynamic network polymer obtained in step (3) was further made into intelligent grippers and strain sensors through simple assembly.

[0060] Example 8 (1) The epoxy monomer and the dibasic acid were prepared according to a molar ratio of epoxy groups in the epoxy monomer to carboxyl groups in the dibasic acid of 1:1.5. The epoxy monomer included polyethylene glycol diglycidyl ether and glycerol triglycidyl ether at a molar ratio of 7:3, and the dibasic acid included sebacic acid, 2,5-furandicarboxylic acid, and 2,2'-dithiodibenzoic acid at a molar ratio of 4.25:4.25:1.5. Graphene was prepared according to 10 wt% of the total mass of the epoxy monomer and the dibasic acid. The above raw materials were mixed and an ester exchange catalyst (triphenylphosphine) with a mass of 1 wt% of the total mass of the epoxy monomer and the dibasic acid was added, and the mixture was heated and stirred at 90 °C for 60 min to perform a polymerization reaction.

[0061] (2) The mixture obtained in step (1) was placed in a vacuum oven at 120 °C for 10 min to remove bubbles.

[0062] (3) The mixture obtained in step (2) was loaded into a polytetrafluoroethylene mold and placed in an oven for curing at 120 °C for 4 h and then at 160 °C for 6 h to obtain a bio-based double dynamic network polymer. The tensile strength thereof was 9.331 MPa, the elongation at break was 79.653%, and the hydrophobic angle was 119.7°.

[0063] (4) The bio-based double dynamic network polymer obtained in step (3) was further made into intelligent grippers and strain sensors through simple assembly.

[0064] Comparative Example 1 (1) The epoxy monomer and the dibasic acid were prepared according to a molar ratio of epoxy groups in the epoxy monomer to carboxyl groups in the dibasic acid of 1:1. The epoxy monomer included polyethylene glycol diglycidyl ether and glycerol triglycidyl ether at a molar ratio of 7:3, and the dibasic acid included sebacic acid and 2,5-furandicarboxylic acid at a molar ratio of 1:1. Graphene was prepared according to 10 wt% of the total mass of the epoxy monomer and the dibasic acid. The above raw materials were mixed and an ester exchange catalyst (triphenylphosphine) with a mass of 1 wt% of the total mass of the epoxy monomer and the dibasic acid was added, and the mixture was heated and stirred at 120 °C for 40 min to perform a polymerization reaction.

[0065] (2) The mixture obtained in step (1) was placed in a vacuum oven at 120 °C for 30 min to remove bubbles.

[0066] (3) The mixture obtained in step (2) was loaded into a polytetrafluoroethylene mold and placed in an oven for curing at 120 °C for 2 h and then at 160 °C for 8 h.

[0067] (4) The bio-based double dynamic network polymer obtained in step (3) was further made into smart grippers and strain sensors through simple assembly.

[0068] The polymer material of the present comparative example, due to the absence of 2,2'-dithiodibenzoic acid containing dynamic disulfide bonds, obtained is a bio-based single dynamic network polymer with only single dynamic covalent bond hydroxyl-ester bond. Its tensile strength is 3.253 MPa, the elongation at break is 50.136%, and the hydrophobic angle is 120.3°, which is significantly lower than Example 3 of the present application. Moreover, the sample was placed in an oven at 160 °C for 6 h to achieve partial healing of the cut site, and the self-healing performance is poorer than that of the double dynamic network polymer.

[0069] Comparative Example 2 (1) The epoxy monomer and the dibasic acid were prepared according to a molar ratio of epoxy groups in the epoxy monomer to carboxyl groups in the dibasic acid of 1:1. The epoxy monomer included polyethylene glycol diglycidyl ether and glycerol triglycidyl ether at a molar ratio of 7:3, and the dibasic acid included sebacic acid, 2,5-furandicarboxylic acid, and 2,2'-dithiodibenzoic acid at a molar ratio of 4.375:4.375:1.25. The above raw materials were mixed and 1 wt% of an ester exchange catalyst (triphenylphosphine) based on the total mass of the epoxy monomer and the dibasic acid was added, and the mixture was heated and stirred at 120 °C for 40 min to perform the polymerization reaction.

[0070] (2) The mixture obtained in step (1) was placed in a vacuum oven at 120 °C for 30 min to remove bubbles.

[0071] (3) The mixture obtained in step (2) was loaded into a polytetrafluoroethylene mold and placed in an oven for curing at 120 °C for 2 h and then at 160 °C for 8 h.

[0072] The polymer material of Comparative Example 2, due to the absence of the conductive nano-filler graphene, obtained is a non-conductive bio-based double dynamic network polymer. Its tensile strength is 11.734 MPa, the elongation at break is 80.667%, and the hydrophobic angle is 123.1°. Moreover, the polymer material itself is not conductive and cannot be directly used as the core sensing component of the resistance strain sensor.

[0073] Figure 2The Fourier transform infrared spectrum of the bio-based double dynamic network polymer prepared in Example 3. The characteristic peak of the epoxy group near 910 cm -1 disappeared, the carboxyl C=O peak near 1701 cm -1 weakened, and the stretching vibration peak of the carbonyl C=O double bond in the ester bond appeared near 1733 cm -1 The hydroxyl peak appeared near 3450 cm -1 , indicating that the curing reaction was complete and a cross-linked dynamic network polymer was formed.

[0074] Figure 3 The nuclear magnetic resonance hydrogen spectrum of the bio-based double dynamic network polymer prepared in Example 3. As can be seen from the figure, the peak intensity of the three characteristic peaks of the epoxy group corresponding to the bio-based double dynamic network polymer (2.55 ppm, 2.73 ppm and 3.09 ppm) and the characteristic peak of the carboxyl hydrogen (11.96 ppm, 13.31 ppm and 13.63 ppm) significantly weakened or even disappeared, while new characteristic peaks appeared at 3.9-4.3 ppm (characteristic peaks of ester bonds), and the characteristic peaks of the secondary hydroxyl hydrogen generated by the opening of the epoxy ring at 4.8-5.2 ppm also appeared. Consistent with the results of the Fourier transform infrared spectrum, it further illustrates the successful preparation of the bio-based double dynamic network polymer.

[0075] Figure 4 The stress-strain diagram of the bio-based double dynamic network polymer prepared in Example 3, which can be seen that the tensile strength is 12.140 MPa and the elongation at break is 102.331%, indicating that the bio-based double dynamic network polymer has good mechanical properties.

[0076] Figure 5 The water contact angle of the bio-based double dynamic network polymer prepared in Example 3, which has a hydrophobic angle of 127.2°, indicating that the bio-based double dynamic network polymer has good hydrophobicity.

[0077] Figure 6 The solvent resistance of the bio-based double dynamic network polymer prepared in Example 3 is shown. The bio-based double dynamic network polymer sample prepared in Example 3 was immersed in H2O, 1M HCl, saturated sodium chloride, petroleum ether, ethanol, acetone, toluene, ethyl acetate, and DMSO solution for 30 days, and the dissolution phenomenon of the sample was observed. The results show that the bio-based double dynamic network polymer of the present application has no obvious dissolution phenomenon after being immersed in different solvents for 30 days, only swelling phenomenon, indicating that a stable three-dimensional network structure is formed inside the bio-based double dynamic network polymer of the present application, indicating that it has good solvent resistance.

[0078] Figure 7The alkali recyclability of the bio-based double dynamic network polymer prepared in Example 3 is embodied. The bio-based double dynamic network polymer sample prepared in Example 3 is cut into small pieces, then immersed in 25 mL of 1 M NaOH solution, and after standing at room temperature for 24 h, the dynamic cross-linked polymer network can be completely depolymerized, then the solution is dried at 120℃ for 8 h to obtain a powder sample, and then a proper amount of epoxy monomer (polyethylene glycol diglycidyl ether and glycerol triglycidyl ether) is added for polymerization reaction, and a new bio-based double dynamic network polymer can be obtained by curing, indicating that it has good alkali recyclability.

[0079] Figure 8 The self-healing property of the bio-based double dynamic network polymer prepared in Example 3 is embodied. The strip-shaped sample of the bio-based double dynamic network polymer is cut into two sections, the cut ends of the two damaged samples are contacted and a certain external force is applied to ensure that the cut part is tightly fitted, then the sample is placed in an oven at 160℃ for 2 h to realize the healing of the cut part, and the two damaged samples form a whole sample again, and the healed sample is subjected to bending and twisting test, the results show that the healed sample still has good mechanical properties, indicating that the bio-based double dynamic network polymer of the present application has good self-healing property.

[0080] Figure 9 The shape memory property of the bio-based double dynamic network polymer prepared in Example 3 is embodied. The strip-shaped sample of the bio-based double dynamic network polymer is bent into a twisted shape at 100℃, then cooled to 25℃ to release the external force, and an ideal twisted shape can be obtained, then it is placed in hot water to restore the original shape. In addition, the strip-shaped sample is heated at 160℃ for 1 h to become a twisted shape, then cooled to 25℃ to release the external force to form a permanent twisted shape. Then the twisted sample is heated to 100℃ to become a strip, cooled to fix the shape, and then placed in hot water to restore the twisted shape. The results show that it has good shape memory performance.

[0081] Figure 10 The application of the bio-based double dynamic network polymer prepared in Example 3 as a smart gripper is embodied. The smart gripper is made of three 70 mm x 10 mm x 5 mm bio-based double dynamic network polymer strips, which are fixed by two circular acrylic plates and adhesive tape. The smart gripper has good shape memory effect, and the initial state is closed. It is programmed to be open at 100℃, then cooled to 25℃ to release the external force to fix the shape, and then placed in hot water to restore the closed state. The smart gripper relies on its shape memory effect to achieve precise grasping of target objects, and its grasping function can be performed in a hot water environment (90-100℃), which can efficiently complete the grasping and transferring task of objects in this temperature range.

[0082] Figure 11Application of the bio-based dynamic network polymer prepared in Example 3 as a strain sensor. Strain index GF = 8.13, response time 1.865 s, stability greater than 1000 bending strain cycles, can be successfully applied to the movement detection of joints such as the neck, elbow, ankle, wrist, fingers and knees of the human body.

[0083] From the data of the various examples, it can be seen that the mechanical properties of Example 3 are the best, because: 1. When the molar ratio of epoxy groups to carboxyl groups is 1:1, the epoxy groups and carboxyl groups can fully crosslink to form a dense and uniform network structure; 2. The 7:3 molar ratio of polyethylene glycol diglycidyl ether (linear) to glycerol triglycidyl ether (branched) takes into account the flexibility and crosslinking density of the network, the linear monomer improves the chain segment flowability, and the branched monomer enhances the structural rigidity, avoiding excessive brittleness or softness; 3. 10wt% of graphene can not be insufficiently enhanced due to insufficient amount, nor can it destroy the matrix structure due to excessive agglomeration, but can be uniformly dispersed and form a physical support; 4. The curing time of the dynamic polymer is appropriate to allow the epoxy groups and carboxyl groups to fully react, forming a uniform, dense and moderately crosslinked network structure. The above reasons make the dynamic polymer with this ratio have good mechanical properties. The elongation at break of Example 5 is slightly poor, because: 1. The proportion of glycerol triglycidyl ether (branched) is 90%, making the crosslinked network extremely dense, and the chain segment activity space is severely compressed, making it difficult for the material to effectively deform under external force, resulting in a small strain. At the same time, the high crosslinked rigid network has strong bearing capacity itself, and the stress will increase when external force is applied; 2. The use amount of 15wt% graphene is relatively high, and the agglomeration of nanofillers causes stress concentration, making the stress increase, and the weak interface between the agglomerates and the matrix also hinders the deformation of the surrounding chain segments, further limiting the overall strain.

Claims

1. A method for preparing a bio-based dual-dynamic network polymer, characterized in that, The preparation method comprises the following steps: S1, mixing epoxy monomers, dibasic acid, graphene and ester exchange catalyst, and heating to carry out polymerization reaction to obtain a prepolymer; wherein the epoxy monomers comprise polyethylene glycol diglycidyl ether and glycerol triglycidyl ether, and the dibasic acid comprises sebacic acid, 2,5-furan dicarboxylic acid and 2,2'-dithiodibenzoic acid; S2, removing bubbles from the obtained prepolymer, and then performing heat curing to obtain the bio-based double dynamic network polymer.

2. The method of claim 1, wherein the bio-based dual dynamic network polymer is prepared by the process comprising: The molar ratio of the epoxy groups in the epoxy monomers to the carboxyl groups in the dibasic acid is 1: (0.5-1.5).

3. The method for preparing the bio-based dual dynamic network polymer according to claim 1, characterized in that, The molar ratio of polyethylene glycol diglycidyl ether to glycerol triglycidyl ether is (9-1):(1-9), and the molar ratio of sebacic acid, 2,5-furan dicarboxylic acid and 2,2'-dithiodibenzoic acid is (4-4.75):(4-4.75):(2-0.5).

4. The method for preparing the bio-based dual dynamic network polymer according to claim 1, characterized in that, The mass of the graphene is 5wt%-25wt% of the total mass of the epoxy monomers and the dibasic acid.

5. The method for preparing the bio-based dual dynamic network polymer according to claim 1, characterized in that, The ester exchange catalyst is triphenylphosphine or 1,5,7-triazabicyclo[4.4.0]dec-5-ene.

6. The method of claim 1, wherein the biobased dynamic dual network polymer is prepared by the steps of: The temperature of the polymerization reaction is 90-120℃, and the time is 40-60 min.

7. The method for preparing the bio-based dual dynamic network polymer according to claim 1, characterized in that, The heat curing specifically comprises: curing at 120-130℃ for 2-4 h, and then curing at 140-160℃ for 6-8 h.

8. The bio-based double dynamic network polymer obtained by the preparation method in any one of claims 1-7.

9. An intelligent actuator, characterized by The material thereof is the bio-based double dynamic network polymer in claim 8.

10. A flexible sensor, characterized by The material thereof is the bio-based double dynamic network polymer in claim 8.

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