1. A preparation method of a recyclable multifunctional dynamic covalent polymer aerogel material is characterized by comprising the following steps:

step S1, dissolving at least one bifunctional reaction monomer A and at least one bifunctional reaction monomer B in a solvent, and stirring to perform a polymerization reaction to obtain a prepolymer; the bifunctional reaction monomer A comprises two functional groups I, and the bifunctional reaction monomer B comprises two functional groups II;

step S2, adding water-soluble organic solvent to the prepolymer obtained in step S1A compound C with at least three functional groups III is used as a cross-linking agent to obtain dynamic covalent polymer wet gel; wherein, the functional group III in the compound C reacts with the excessive functional group I or functional group II in the step S1, and the molar ratio of the bifunctional reaction monomer A, the bifunctional reaction monomer B and the compound C is n_C:|n_A-n_B|＝1:1；

Step S3, carrying out aging treatment and solvent exchange treatment on the obtained dynamic covalent polymer wet gel, and then drying to obtain a recyclable multifunctional dynamic covalent polymer aerogel material;

the dynamic covalent bond in the recyclable multifunctional dynamic covalent polymer aerogel material is at least one of an imine bond, a disulfide bond, a boron-oxygen bond, a silicon-oxygen bond, a carbon-carbon bond and a carbon-oxygen bond.

2. The method for preparing the recyclable multifunctional dynamic covalent polymer aerogel material as claimed in claim 1, wherein the functional group I is one or two selected from aldehyde group, ketone group, hydroxyl group, mercapto group, carboxyl group, carbonyl group, double bond, disulfide bond, boric acid group and isocyanate group; the functional group II is selected from one or two of amino, hydroxyl, sulfydryl, carboxyl, carbonyl, double bond, disulfide bond, boric acid group and isocyanate group.

3. The method of preparing the recyclable multifunctional dynamic covalent polymer aerogel material of claim 2, wherein the aldehyde or ketone groups react with amino groups to form imine linkages; the sulfydryl and the sulfydryl react to form a disulfide bond; the boric acid group reacts to generate a boron-oxygen bond; reacting the silicon hydroxyl with the silicon hydroxyl to generate a silicon-oxygen bond; the double bond reacts with the double bond to generate a carbon-carbon bond; the hydroxyl and hydroxyl, hydroxyl and isocyanate, hydroxyl and carboxyl, hydroxyl and carbonyl, and amino and carbonyl generate carbon-oxygen bonds.

4. The method for preparing the recyclable multifunctional dynamic covalent polymer aerogel material as claimed in claim 1, wherein the solvent in step S1 is selected from any one of dichloromethane, chloroform, dimethyl sulfoxide, N-dimethylformamide, N-dimethylacetamide, N-methylpyrrolidone, dioxane, acetone, methanol, ethanol, propanol, isopropanol, benzene, toluene, xylene, and trimethylbenzene.

5. The method of claim 1, wherein in step S2, the cross-linking agent is at least one selected from triethylamine, tris (2-aminoethyl) amine, 1,3, 5-tris (4-aminophenyl) benzene, 1,3, 5-tris (4-aminophenoxy) benzene, HDI trimer curing agent, trimethylolpropane tris (mercaptopropionate), tetrakis (4-aminophenyl) methane, triethanolamine, triisocyanate, pentaerythritol tetrakis (3-mercaptopropionate), polyformaldehyde, polyethyleneimine, trimesic aldehyde, trialdehyde, polyformaldehyde, and tetraaldehyde tetraphenylethylene.

6. The method for preparing multifunctional dynamic covalent polymer aerogel material capable of being recycled as claimed in claim 1, wherein the solvent used in the solvent exchange treatment in step S3 is at least two selected from dichloromethane, chloroform, dimethyl sulfoxide, N-dimethylformamide, N-dimethylacetamide, N-methylpyrrolidone, dioxane, acetone, methanol, ethanol, propanol, isopropanol, benzene, toluene, xylene, trimethylbenzene, N-hexane and acetone, and the solvent used in step S1 is required to be included.

7. The method for preparing the recyclable multifunctional dynamic covalent polymer aerogel material as claimed in claim 1, wherein the drying method in step S3 is atmospheric drying, supercritical drying, freeze drying or vacuum assisted drying.

8. A recyclable multifunctional dynamic covalent polymer aerogel material, characterized by being prepared by the preparation method of any one of claims 1 to 7.

9. The application of the recyclable multifunctional dynamic covalent polymer aerogel material is characterized in that the recyclable multifunctional dynamic covalent polymer aerogel material is used for preparing water treatment products or conductive aerogels.

10. The use of the recyclable multifunctional dynamic covalent polymer aerogel material of claim 9, wherein the recyclable multifunctional dynamic covalent polymer aerogel material is prepared by incorporating conductive functional fillers and/or carbonizing.

Background

The aerogel material has the characteristics of low density, high porosity and high specific surface area, so that the aerogel material has multiple functions and has great application prospects in the fields of electromagnetic shielding, sensing, energy storage, catalysis, water treatment, heat insulation, noise reduction and the like. But faces three problems in the industrial process of aerogel materials, namely fragility, shrinkage and low yield. On one hand, the aerogel material with ideal mechanical properties can be obtained through process regulation; on the other hand, shrinkage during aerogel production can be suppressed by supercritical drying and freeze-drying. However, neither supercritical drying nor freeze drying techniques are suitable for large-scale preparation of aerogels. Therefore, solving the above existing problems, while imparting new characteristics to aerogel materials, will effectively facilitate the progress of industrialization of aerogels.

With the increase of the requirements of human society on sustainability, the preparation of the recyclable multifunctional material can provide a low-price, green and environment-friendly material for industrial production. Currently, most recyclable materials are made primarily from linear thermoplastic polymers. Although linear polymers are processable, mechanical properties, solvent resistance, etc. are greatly reduced compared to thermoset polymeric materials. The dynamic covalent polymer can be constructed through reversible covalent bonds, and has both the physical properties of thermosetting polymers and dynamic recyclability. Currently, the reactions involved in the study of more dynamic covalent bonds include Diels-Alder reactions, transesterification, olefin metathesis, disulfide interchange, amino-aldehyde condensation, boron-oxygen dynamic bonds, and the like. However, few studies on the construction of aerogels by using dynamic covalent polymer networks have been reported.

Disclosure of Invention

Aiming at the defects in the prior art, the invention aims to provide a recyclable multifunctional dynamic covalent polymer aerogel material and a preparation method and application thereof. The aerogel material prepared by constructing a dynamic polymer network by utilizing dynamic covalent bonds has excellent mechanical properties, low shrinkage, recoverability and multiple functions, and the preparation method is simple, economic and can be produced in large scale.

The purpose of the invention is realized by the following scheme:

the first aspect of the invention provides a preparation method of a recyclable multifunctional dynamic covalent polymer aerogel material, which comprises the following steps:

step S1, dissolving at least one bifunctional reaction monomer A and at least one bifunctional reaction monomer B in a solvent, and stirring to perform a polymerization reaction to obtain a prepolymer; the bifunctional reactive monomer A comprises two functional groups I (the two functional groups I can be the same or different), and the bifunctional reactive monomer B comprises two functional groups II (the two functional groups II can be the same or different); the reaction temperature is between 0 and 80 ℃;

step S2, adding a compound C containing at least three functional groups III as a cross-linking agent into the prepolymer obtained in step S1 to obtain dynamic covalent polymer wet gel; wherein, the functional group III in the compound C reacts with the excessive functional group I or functional group II in the step S1, and the molar ratio of the bifunctional reaction monomer A, the bifunctional reaction monomer B and the compound C is n_C:|n_A-n_B1: 1; the reaction temperature is between 0 and 80 ℃, and the reaction time is between 0.5 and 48 hours;

step S3, carrying out aging treatment and solvent exchange treatment on the obtained dynamic covalent polymer wet gel, and then drying to obtain a recyclable multifunctional dynamic covalent polymer aerogel material; aging at 25-60 deg.C for 12-96 hr;

the dynamic covalent bond in the recyclable multifunctional dynamic covalent polymer aerogel material is at least one of an imine bond, a disulfide bond, a boron-oxygen bond, a silicon-oxygen bond, a carbon-carbon bond and a carbon-oxygen bond.

Preferably, the functional group I is selected from one or two of aldehyde group, ketone group, hydroxyl group, sulfydryl group, carboxyl group, carbonyl group, double bond, disulfide bond, boric acid group and isocyanate group; the functional group II is selected from one or two of amino, hydroxyl, sulfydryl, carboxyl, carbonyl, double bond, disulfide bond, boric acid group and isocyanate group.

Preferably, the aldehyde or ketone group reacts with an amino group to form an imine bond (i.e., schiff base bond); the sulfydryl and the sulfydryl react to form a disulfide bond; the boric acid group reacts to generate a boron-oxygen bond; the silicon hydroxyl and the silicon hydroxyl react to generate a silicon-oxygen bond; the double bond reacts with the double bond to generate a carbon-carbon bond; the hydroxyl and hydroxyl, hydroxyl and isocyanate, hydroxyl and carboxyl, hydroxyl and carbonyl, and amino and carbonyl generate carbon-oxygen bonds.

Preferably, the difunctional reactive monomer A is selected from the group consisting of diethyl 2, 3-diisopropylsuccinate, glyoxal, malondialdehyde, glutaraldehyde, terephthalaldehyde, phthalaldehyde, 2, 6-pyridinedicarboxaldehyde, 4' -biphenyldicarboxaldehyde, phthalaldehyde, 2-bromo-1, 3-dicarboxybenzene, 2, 5-dimethoxyterephthalaldehyde, 2, 5-diacetylene terephthalaldehyde, 3, 4-dibromothiophene-2, 5-dicarboxaldehyde, 2, 5-bis (azidoethylglycol) terephthalaldehyde, 2,3,5, 6-tetrafluoro-terephthalaldehyde, 2, 5-difluoro-terephthalaldehyde, 3, 5-dimethyl-1H-pyrrole-2, 4-dicarboxaldehyde, 2-methylindazine-1, 3-dicarboxaldehyde, 2 '-bipyridine-3, 3' -dicarboxaldehyde, 5-dihydroxy-1, 4-dicarboxaldehyde, 2, 5-dibutoxybenzene-1, 4-dicarboxaldehyde, 10-ethyl-3, 7-diformylphenoxazine, 1, 8-naphthyridine-2, 7-dicarbaldehyde, 10-ethyl-3, 7-diformylphenothiazine, 3 '-bipyridine-5, 5' -dicarboxaldehyde, 2, 5-diheptyloxy-1, 4-terephthalaldehyde, 2, 3-anthracenediformaldehyde, 3, 5-pyridinedicarboxaldehyde, thiophene-2, 4-dicarboxaldehyde, acetaldehyde-polyethylene glycol-acetaldehyde, phenylpropionaldehyde, tolylene diisocyanate, At least one of compounds having two functional groups such as hydroxyl group, aldehyde group, ketone group, borate group, isocyanate group and double bond, such as aminated polydimethylsiloxane, hydroxylated polydimethylsiloxane, isocyanate polydimethylsiloxane, polytetrahydrofuran ether glycol, polyethylene glycol-polypropylene glycol-polyethylene glycol, 4' -diphenylmethane diisocyanate, isophorone diisocyanate, 1, 5-hexadiene, 1, 6-hexanedithiol, hexamethylene diisocyanate, 4' -dicyclohexylmethane diisocyanate, 1, 5' -naphthalene diisocyanate, 4-hydroxyphenylboronic acid and 4-hydroxymethylphenylboronic acid.

Preferably, the difunctional reactive monomer B is selected from the group consisting of o-phenylenediamine, m-phenylenediamine, p-phenylenediamine, 4 '-diaminodiphenyl ether, diphenylenediamine and its derivatives, 2-bis (3-amino-4-hydroxyphenyl) hexafluoropropane, 4' -diaminodiphenylmethane, 4 '-diaminotriphenylmethane, diaminodiphenylmethane, hexafluorodiphenyldiamine and its derivatives, 4' -diaminobenzophenone and its derivatives, 4-diaminodiphenyl sulfide, cyclohexanediamine and its derivatives, ethylenediamine, diethylenetriamine, 1, 2-propylenediamine, triethylenetetramine, ethylene-D4-diamine, 1, 5-diamino-3-methylpentane, isophthaloyl hydrazine and its derivatives, phenylene diisocyanate, toluene diisocyanate, and mixtures thereof, At least one of compounds having two functional groups such as an amino group, an isocyanate group, a hydroxyl group, a mercapto group and the like, such as aminated polydimethylsiloxane, hydroxylated polydimethylsiloxane, isocyanate polydimethylsiloxane, polytetrahydrofuran ether glycol, polyethylene glycol-polypropylene glycol-polyethylene glycol, 4' -diphenylmethane diisocyanate, isophorone diisocyanate, 1, 5-hexadiene, 1, 6-hexanedithiol, hexamethylene diisocyanate, 4' -dicyclohexylmethane diisocyanate and 1, 5' -naphthalene diisocyanate.

Preferably, in the step S1, the solvent is selected from any one of dichloromethane, chloroform, dimethyl sulfoxide, N-dimethylformamide, N-dimethylacetamide, N-methylpyrrolidone, dioxane, acetone, methanol, ethanol, propanol, isopropanol, benzene, toluene, xylene, and trimethylbenzene.

Preferably, in step S2, the crosslinking agent is at least one selected from triethylamine, tris (2-aminoethyl) amine, 1,3, 5-tris (4-aminophenyl) benzene, 1,3, 5-tris (4-aminophenoxy) benzene, HDI TRIMER curing agent HDI-TRIMER (the reactive group is isocyanate), trimethylolpropane tris (mercaptopropionate), tetrakis (4-aminophenyl) methane, triethanolamine, triisocyanate, pentaerythritol tetrakis (3-mercaptopropionate), polyformaldehyde, polyethyleneimine, trimesic aldehyde, trialdehyde, polyformaldehyde, tetraaldehyde tetraphenylethylene and the like having three or more multifunctional compounds such as hydroxyl group, aldehyde group, amino group, isocyanate group, mercapto group and the like.

Preferably, in the step S3, the solvent used in the solvent exchange treatment is at least two selected from dichloromethane, chloroform, dimethyl sulfoxide, N-dimethylformamide, N-dimethylacetamide, N-methylpyrrolidone, dioxane, acetone, methanol, ethanol, propanol, isopropanol, benzene, toluene, xylene, trimethylbenzene, N-hexane and acetone, wherein it is necessary to include one of the solvents used in the step S1.

Preferably, in step S3, the drying method is atmospheric drying, supercritical drying, freeze drying or vacuum assisted drying, and the drying conditions are determined according to different drying methods.

The second aspect of the invention provides a recyclable multifunctional dynamic covalent polymer aerogel material, which is prepared by the preparation method.

In a third aspect of the invention, there is provided a use of a recyclable multifunctional dynamic covalent polymer aerogel material in the preparation of a water treatment product or in the preparation of an electrically conductive aerogel.

Preferably, the recyclable multifunctional dynamic covalent polymer aerogel material is hydrophobically modified by low surface energy chemicals for water treatment. Preferably, the hydrophobic modifier is at least one of low surface energy chemicals such as hydrogen-containing silicone oil, polydimethylsiloxane, perfluorooctyltrimethoxysilane, perfluorooctyltrichlorosilane, perfluorooctyltriethoxysilane, octadecyltrimethoxysilane, and the like.

Preferably, the conductive aerogel is prepared by introducing conductive functional fillers into a recyclable multifunctional dynamic covalent polymer aerogel material and/or carbonizing.

Preferably, the conductive functional filler is at least one of functional nanomaterials such as graphene and derivatives thereof, carbon nanotubes, gold nanoparticles, MXenes, and kaolin.

Preferably, the carbonization condition is completed in one or more mixed gases of nitrogen, argon and carbon dioxide, the temperature is raised in sections, the temperature rise rate is 2-10 ℃/min, and the carbonization temperature is 650-1300 ℃.

Compared with the prior art, the invention has the following beneficial effects:

1. the preparation method of the invention constructs a dynamic polymer gel network through dynamic covalent bonds, successfully combines the recoverability of the dynamic covalent polymers and the multifunction of aerogel materials, and can further expand other functional applications (such as water treatment by hydrophobic modification, functional material addition and/or carbonization so as to have conductivity) on the basis of having multiple functions (such as excellent mechanical properties, noise reduction, heat insulation, low linear shrinkage and the like).

2. The dynamic covalent polymer aerogel material has excellent mechanical properties such as light weight, tensile resistance, strong bearing capacity, good flexibility, compression resilience and the like, has repairability, high sound absorption coefficient and low heat conductivity coefficient, and can be used in the fields of noise reduction, heat insulation, flame retardance and the like on the basis of the properties; after hydrophobic modification, the modified water treatment agent can be used in the field of water treatment; the conductive functional material is added and/or the conductive material is carbonized to obtain the conductivity which can be used in the fields of electromagnetic shielding, energy storage, sensing and the like; in addition, based on low linear shrinkage, the method can be produced in a large scale; most importantly, the method has recyclability and has great significance for the development of sustainable development strategy.

Drawings

Other features, objects and advantages of the invention will become more apparent upon reading of the detailed description of non-limiting embodiments with reference to the following drawings:

FIG. 1 is a photograph of the macroscopic properties of the aerogel prepared in example 1 of the present invention;

FIG. 2 is a plot of the compressive rebound stress strain of the aerogel prepared in example 1 of the present invention;

FIG. 3 is a scanning electron micrograph of an aerogel sample prepared in example 2 of the present invention;

FIG. 4 is a schematic representation of the aerogel samples prepared in example 3 of the present invention before and after degradation and a recoverable mechanism diagram;

FIG. 5 is a comparative graph of the compression mechanical property test of the aerogel sample prepared in example 3 of the present invention and the aerogel prepared by using the recycling solution;

FIG. 6 is a recoverable test chart of a sample aerogel according to example 3 of the present invention;

FIG. 7 is the thermal conductivity of the aerogel sample prepared in example 4 of the present invention;

FIG. 8 is the sound absorption coefficient of the aerogel sample prepared in example 4 of the present invention;

FIG. 9 is a hydrophobicity and oil-water separation test of the hydrophobically modified aerogel samples prepared in example 5 of the present invention;

FIG. 10 is a SEM image of the carbon aerogel obtained after carbonization and prepared in example 6 of the present invention.

Detailed Description

The present invention will be described in detail with reference to specific examples. The following examples will assist those skilled in the art in further understanding the invention, but are not intended to limit the invention in any way. It should be noted that it would be obvious to those skilled in the art that various changes and modifications can be made without departing from the spirit of the invention. All falling within the scope of the present invention.

The present invention will be described in further detail with reference to specific examples.

The performance of the dynamically recyclable multifunctional polymer aerogel prepared by the invention is characterized as follows:

the linear shrinkage of the aerogel was calculated by (D gel before drying/D after coacervation drying-1). times.100%, D being the diameter.

The thermal conductivity of the aerogels was determined according to the transient planar heat source method (TPS-2500S, Hot Disk, Sweden) with the reference standard ISO-22007-2.2.

The acoustic absorption coefficient of the aerogel is determined according to a standing wave tube tester, and is referred to the standard JJF 1223-2009.

The morphology of the aerogel was obtained by field emission scanning electron microscopy (test voltage 10 kV).

The water contact angle of the aerogel is measured by a German DSA100 contact angle tester.

Example 1

This example provides a method for preparing a dynamically recyclable multi-functional polymer. The method specifically comprises the following steps:

step 1: 26.11mmol of 2, 5-dimethoxyphthaldehyde was dissolved in 50ml of dimethyl sulfoxide, and after complete dissolution, 7.84mmol of diethylenetriamine was added thereto and stirred at 25 ℃ for 12 hours to obtain a polyimide prepolymer.

Step 2: adding 12.18mmol of tri (2-aminoethyl) amine into the polyimide prepolymer, fully stirring, pouring into a mold, and then transferring into an environment at 25 ℃ for aging for 3 days.

And step 3: and (3) carrying out solvent exchange on the gel obtained in the step (2) by using a dimethyl sulfoxide/absolute ethyl alcohol/acetone solvent system, placing the sample in an environment of 25 ℃ for natural drying after the solvent exchange is finished, and transferring the sample into a 60 ℃ drying oven for drying for 12 hours after the drying is finished. The obtained aerogel has a density of 120mg/cm³The linear shrinkage was 12%.

The aerogel prepared in example 1 was subjected to macroscopic performance experiments, as shown in fig. 1, (1) the aerogel was placed on the flowers without breaking the flowers, indicating that the aerogel was light and was a low-density material. (2) A 1000g weight (corresponding to 3333 times its own weight) was placed on a 0.3g aerogel cylinder without crushing, and it was seen that its load-bearing capacity was quite high. (3) A weight of 100g (equivalent to 2000 times its own weight) was hung at the lower end of the 0.05g aerogel strip without being pulled apart, indicating that it has a strong stretch resistance. (4) The obtained aerogel is bent and knotted at will without breaking, and the flexibility is proved to be good. (5) Testing the stress-strain curve of the obtained aerogel in compression: the compression test method is that a cylindrical sample with the diameter of 17mm multiplied by the height of 11mm is selected, a compression experiment is carried out at the compression rate of 5mm/min, after the strain reaches 50%, the clamp is removed, the strain recovery of more than 20% can be observed from the morning recovery curve of figure 2, and the excellent compression resilience performance is proved. In conclusion, the obtained aerogel has excellent mechanical properties of light weight, super-strong bearing capacity, excellent tensile resistance, excellent flexibility and excellent compression resilience.

Recovery test: dispersing the obtained aerogel in 10ml of ethanol and 5ml of acidic aqueous solution, heating and ultrasonically treating to obtain light yellow recovery liquid, drying and thermally pressing to obtain a polymer film, and performing tensile test on the obtained aerogel polymer film: a rectangular sample with the length of 30mm, the width of 5mm and the thickness of 1mm is selected, the tensile rate is 100mm/min, and the test shows that the breaking stress reaches 5 MPa.

Example 2

This example provides a method for preparing a dynamically recyclable multi-functional polymer. The method specifically comprises the following steps:

step 1: 3.73mmol of terephthalaldehyde was dissolved in 7ml of anhydrous ethanol, and after complete dissolution, 1.12mmol of diethylenetriamine was added thereto, followed by stirring at 35 ℃ for 12 hours to obtain a polyimide prepolymer.

Step 2: 1.74mmol of tris (2-aminoethyl) amine was added to the polyimide prepolymer, stirred well and poured into a mold, and then aged at 25 ℃ for 2 days.

And step 3: and (3) carrying out solvent exchange on the gel obtained in the step (2) by using an absolute ethyl alcohol/acetone solvent system, naturally drying the sample in an environment at 25 ℃ after finishing the solvent exchange, and transferring the sample into a 60 ℃ drying oven for drying for 12 hours after the drying is finished. The obtained aerogel has a density of 115mg/cm³The linear shrinkage was 15%. As shown in fig. 3, in the scanning electron microscope morphology photograph of the aerogel sample prepared under atmospheric pressure drying in this embodiment, the obtained aerogel is a typical pearl-like particle stacking morphology of the aerogel.

Example 3

The method comprises the following steps of (a) carrying out a recoverable experiment on the aerogel of example 2:

step 1: 3.73mmol of terephthalaldehyde was dissolved in 7ml of anhydrous ethanol, and after complete dissolution, 1.12mmol of diethylenetriamine was added thereto, followed by stirring at 35 ℃ for 12 hours to obtain a polyimide prepolymer.

Step 2: 1.74mmol of tris (2-aminoethyl) amine was added to the polyimide prepolymer, stirred well and poured into a mold, and then aged at 25 ℃ for 2 days.

And step 3: and (3) carrying out solvent exchange on the gel obtained in the step (2) by using an absolute ethyl alcohol/n-hexane solvent system to obtain polyimide aerogel, then placing the sample in an environment at 25 ℃ for natural drying, and after drying, transferring the sample into a 60 ℃ oven for drying for 12 hours.

And 4, step 4: 2.24mmol of diethylenetriamine and 3.48mmol of tris (2-aminoethyl) amine are added into 20ml of absolute ethyl alcohol to prepare a recovery solution, and then the dried polyimide aerogel is cut into pieces and placed into the prepared recovery solution to be degraded under the condition of ultrasonic heating.

And 5: adding 7.46mmol of terephthalaldehyde into the recovered solution to obtain polyimide gel again, and performing the same aging, solvent exchange and normal pressure drying to obtain new polyimide aerogel, wherein the density of the obtained aerogel is 110mg/cm³The linear shrinkage was 14%. As can be seen from fig. 4, the excessive amino groups can degrade the polyimide into soluble prepolymer and cross-linking agent (after degradation, the soluble prepolymer can be used for film pressing or adhesive, etc.), and new polyimide aerogel can be formed through the sol-gel process again. As shown in fig. 5, the overlap ratio of the compressive stress-strain curve of the regenerated aerogel and the compressive stress-strain curve of the original sample is high (the compressive test method of the stress-strain curve is the same as that in example 1), which indicates that the mechanical properties of the regenerated aerogel sample can be guaranteed, and the regenerated aerogel sample can be recycled, not degraded, but can achieve the purpose of 'full recycling-remanufacturing', and has great significance for developing the strategy of sustainable development.

(II) the aerogel obtained in example 2 was subjected to a repairable test, and as shown in FIG. 6, a new mixed solution of terephthalaldehyde and diethylenetriamine polymer sol and tris (2-aminoethyl) amine was dropped on the scratched portion, so that scratches could be repaired in the form of aerogel, which is different from a binder such as glue.

Example 4

This example provides a method for preparing a dynamically recyclable multi-functional polymer. The method specifically comprises the following steps:

step 1: 3.73mmol of terephthalaldehyde was dissolved in 5ml of dimethyl sulfoxide, and after complete dissolution, 2.24mmol of diethylenetriamine was added thereto, followed by stirring at 25 ℃ for 12 hours to obtain a polyimide prepolymer.

Step 2: 0.99mmol of 1,3, 5-tri (4-aminophenyl) is added into the polyimide prepolymer, fully stirred and poured into a mould, and then the mould is moved into an environment with the temperature of 25 ℃ for aging for 3 days.

And step 3: and (3) carrying out solvent exchange on the gel obtained in the step (2) by using a dimethyl sulfoxide/absolute ethyl alcohol/n-hexane solvent system, naturally drying the sample in an environment at 25 ℃, and transferring the sample into a 60 ℃ drying oven for drying for 12 hours after the drying is finished. The obtained aerogel has a density of 120mg/cm³The linear shrinkage was 14%.

As shown in FIG. 7, samples of the prepared aerogels were tested for thermal conductivity according to the transient planar heat source method (TPS-2500S, Hot Disk, Sweden) with reference to ISO-22007-2.2. 3 parallel samples are prepared, the thermal conductivity coefficient is about 42 mW/(m.K), the lower the thermal conductivity coefficient is, the better the thermal insulation effect is, and the dynamic covalent polymer aerogel has important application value in the field of thermal insulation from the aspect of the thermal conductivity coefficient.

As shown in fig. 8, the prepared aerogel samples were subjected to sound absorption coefficient measurement according to a standing wave tube tester, with reference to the standard JJF 1223-2009. From the higher sound absorption coefficient of a high-frequency region (above 2000 Hz), the dynamic covalent polymer aerogel has important application value in the noise reduction field.

Example 5

This example provides a method for preparing a dynamically recyclable multi-functional polymer. The method specifically comprises the following steps:

and (2) dissolving 3.73mmol of 2,3,5, 6-tetrafluoro-terephthalaldehyde in 8ml of dimethyl sulfoxide in the step (1), adding 1.12mmol of 1, 4-cyclohexanediamine after complete dissolution, and stirring at 25 ℃ for 12 hours to obtain a polyimide prepolymer.

And 2, adding 1.74mmol of 1,3, 5-tri (4-aminophenyl) into the polyimide prepolymer, fully stirring, pouring into a mold, and then transferring into an environment at 25 ℃ for aging for 2 days.

And 3, carrying out solvent exchange on the gel obtained in the step 2 by using a dimethyl sulfoxide/absolute ethyl alcohol/isopropanol solvent system, naturally drying the sample in an environment at 25 ℃ after finishing the solvent exchange, and transferring the sample into a 60 ℃ drying oven for drying for 12 hours after finishing the drying. (Water contact Angle < 60 degree)

Step 4, putting the polyimide sample into a vacuum drier, and taking0.5ml perfluorooctyl trichlorosilane is put into a sample bottle and put into a dryer, and the sample bottle is vacuumized and then placed for 48 hours. After the polyimide aerogel is subjected to hydrophobic modification by the vapor deposition method, the density of the obtained aerogel is 132mg/cm³The linear shrinkage was 11% and the contact angle was 134 °. That is, the dynamic covalent polymeric aerogel transitions from hydrophilic to hydrophobic samples with water contact angles to 134 °. As shown in fig. 9, a mixture of water and dichloromethane is prepared, dichloromethane is at the lower layer, water is at the upper layer, the aerogel subjected to hydrophobic modification is immersed in water, and can rapidly adsorb the dichloromethane oily solvent at the bottom of water, so as to realize oil-water separation, and the hydrophobic sample has strong adsorbability,

example 6

This example provides a method for preparing a dynamically recyclable multi-functional polymer. The method specifically comprises the following steps:

step 1: dissolving 1mmol of 4,4 '-biphenyl dicarboxaldehyde and 2.73mmol of terephthalaldehyde in 8ml of N, N-dimethylformamide dispersion liquid compounded by 10mg/ml of graphene and carbon nano tubes, adding 1.12mmol of 4,4' -diaminodiphenyl ether after complete dissolution, and stirring at 25 ℃ for 12 hours to obtain the polyimide prepolymer.

Step 2: 1.74mmol of tris (2-aminoethyl) was added to the polyimide prepolymer, stirred well and poured into a mold, and then aged at 25 ℃ for 2 days.

And step 3: and (3) carrying out solvent exchange on the gel obtained in the step (2) by using an N, N-dimethylformamide/absolute ethyl alcohol/isopropanol solvent system, naturally drying the sample in an environment at 25 ℃ after finishing the solvent exchange, and transferring the sample into a 60 ℃ oven for drying for 12 hours after finishing the drying, wherein the obtained sample is an electrically insulating polymer.

And 4, step 4: and (2) placing the prepared graphene/carbon nano tube/polyimide nano composite aerogel sample in a tube furnace, carbonizing in an argon atmosphere, heating to 350 ℃ from room temperature at a speed of 5 ℃/min, preserving heat for 2h, heating to 850 ℃ at a speed of 10 ℃/min, preserving heat for 6h, and annealing to obtain the conductive aerogel. The density of the obtained carbon aerogel is 110mg/cm³Linear shrinkage of 40% (shrinkage upon carbonization), conductivity of 200S/cm, from the scan of the conductive aerogel in FIG. 10As can be seen from the electron microscope morphology photograph, the high temperature carbonization did not destroy the aerogel morphology.

The method of the invention utilizes dynamic covalent bond to construct dynamic polymer network, uses at least two reaction monomers to obtain prepolymer with certain molecular weight, uses compound containing three or more than three reaction groups as cross-linking agent to complete sol-condensation process, and obtains dynamic covalent polymer aerogel material under specific drying condition. The dynamic covalent polymer aerogel with multiple functions (such as water treatment, electromagnetic shielding, conductivity and the like) with wider application prospect is obtained through functional modification or introduction of functional fillers or carbonization. In addition to the versatility of aerogels, the aerogel materials constructed using the dynamic covalent polymer networks of the present invention are recyclable, and the materials are simple and economical to prepare, and suitable for commercial production. The aerogel prepared by the invention has low linear shrinkage, and is beneficial to large-scale preparation of aerogel materials by utilizing a normal pressure drying technology.

The foregoing description of specific embodiments of the present invention has been presented. It is to be understood that the present invention is not limited to the specific embodiments described above, and that various changes or modifications may be made by one skilled in the art within the scope of the appended claims without departing from the spirit of the invention. The embodiments and features of the embodiments of the present application may be combined with each other arbitrarily without conflict.