Thermosetting degradable polymer as well as preparation method and application thereof

Abstract

The invention discloses a degradable thermosetting polymer and a preparation method and application thereof, and belongs to the technical field of chemical synthesis, and the preparation method comprises the following steps: in an inert atmosphere, preparing an IPDI solution and a mixed solution of Tryp and DBTDL, dropwise adding the mixed solution into the IPDI solution, heating for reaction, and purifying to obtain ITr; the preparation method comprises the following steps: preparing a PVA solution in an inert atmosphere, adding ITr and DBTDL into the PVA solution, stirring until the ITr and the DBTDL are dissolved, heating the mixture to react, pouring the mixture into dichloromethane after the reaction is finished, collecting a solid polymer, and removing impurities to prepare PIVA; the preparation method comprises the following steps: dissolving PIVA in DMSO, dissolving MDI-TAD in DMAc, and pouring an MDI-TAD solution into a PIVA solution under the condition of high-speed stirring, so as to obtain the PIVA / MDI-TAD composite material. The polymer can be degraded by microorganisms, and the problems of environmental pollution and resource waste existing in an existing thermosetting polymer recovery method are effectively solved.

Description

Technical Field

[0001] The invention belongs to the technical field of chemical synthesis, and in particular relates to a thermosetting degradable polymer and a preparation method and application thereof. Background Art

[0002] Plastics are widely used in aerospace, machinery and electronics because they are easy to manufacture and use and are inexpensive. However, it is generally believed that plastics will aggravate chemical degradation when exposed to ultraviolet rays, heat and oxygen conditions, leading to fragmentation and the formation of microplastics. Microplastics are harmful to animals, plants and the environment due to the ability of plastics to adsorb, transport and release chemicals and the potential toxicity of particles. In order to reduce the generation of microplastics, people usually enhance the durability of plastics by covalent cross-linking, however, this often leads to recycling difficulties. For example, epoxy resin, a typical thermosetting plastic, has significantly improved mechanical properties after curing (covalent cross-linking), but the cured epoxy resin is difficult to melt and recycle. Therefore, the recycling of such plastics can only be achieved through mechanical crushing, high-temperature incineration or chemical recycling. However, these recycling methods will lead to resource waste or secondary pollution.

[0003] In recent years, non-covalent cross-linking technologies based on hydrogen bonding, electrostatic interactions, and metal-coordination have shown great potential in the recyclability of thermosets. However, the dissociation processes of these supramolecular interactions often require the use of toxic reagents, resulting in high energy costs and large amounts of hazardous waste. Therefore, it has become particularly important to develop innovative green recycling technologies to achieve sustainable management of thermosets. Summary of the invention

[0004] In view of the above-mentioned deficiencies in the prior art, the present invention provides a degradable thermosetting polymer and a preparation method and application thereof. The polymer can be degraded by microorganisms, effectively solving the problems of environmental pollution and resource waste in the existing thermosetting polymer recycling methods.

[0005] To achieve the above purpose, the technical solution adopted by the present invention to solve the technical problem is:

[0006] A method for preparing a thermosetting degradable polymer comprises the following steps:

[0007] (1) Synthesis of 2-(1H-indol-3-yl)ethyl(3-(isocyanatomethyl)-3,5,5-trimethylcyclohexyl)carbamate (ITr): Under an inert atmosphere, IPDI is dissolved in a low boiling point solvent to prepare an IPDI solution; Tryp and DBTDL are dissolved in dichloromethane to prepare a mixed solution, the mixed solution is added dropwise to the IPDI solution, and then heated to complete the reaction, purified, and dried to prepare ITr;

[0008] (2) Synthesis of PIVA: Under an inert atmosphere, PVA was dissolved in DMSO to prepare a PVA solution, ITr and DBTDL were added thereto, and stirred until completely dissolved, and the mixture was heated to react. After the reaction was completed, the mixture was poured into dichloromethane, and the solid polymer was collected and impurities were removed to prepare PIVA;

[0009] (3) Synthesis of CPIVA: PIVA was dissolved in DMSO and MDI-TAD was dissolved in DMAc. Under high-speed stirring conditions, the MDI-TAD solution was poured into the PIVA solution to obtain CPIVA.

[0010] Furthermore, in step (1), the low boiling point solvent is dichloromethane or ethyl acetate.

[0011] Furthermore, in step (1), the mass ratio of IPDI:Tryp:DBTDL is 10-30:10-30:1; the mass concentration of the IPDI solution is 100-200 g / L; and the mass concentration of Tryp in the mixture solution is 100-200 g / L.

[0012] Furthermore, in step (1), the heating reaction temperature is 40-50° C., and the reaction time is 3-5 h.

[0013] Furthermore, in the reaction solution of step (2), the mass concentration of PVA is 40-200 g / L, the mass concentration of ITr is 190-770 g / L, and the mass concentration of DBTDL is 6-12 g / L.

[0014] Furthermore, in step (2), the heating reaction temperature is 40-50° C., and the reaction time is 3-5 h.

[0015] Furthermore, in step (3), the mass ratio of PIVA to MDI-TAD is 1000:1-75, and the reaction temperature is 0-25°C.

[0016] Furthermore, the preparation method of 4,4'-(4,4'-diphenylmethylene)triazolidinedione (MDI-TAD) in step (3) is as follows:

[0017] (1) Dissolve ethyl carbazate (40.0 g, 0.384 mol, 2 eq) and 4,4'-methylenebis(phenyl isocyanate) (48.0 g, 0.192 mol, 1 eq) in 300 ml of toluene respectively, and then mix the two solutions in a nitrogen atmosphere. After mixing, stir and react at room temperature for 2 h, then heat to 90° C., continue stirring and react for 2 h, cool to room temperature, and then filter and wash to obtain a difunctional semicarbazide;

[0018] (2) Under nitrogen atmosphere, difunctional semicarbazide (86.2 g, 0.188 mol) was dissolved in 330 ml potassium hydroxide solution, refluxed at 100° C. for 1.5 h, cooled to room temperature, and then hydrogen chloride was added thereto to acidify the pH to 1, and filtered to obtain difunctional ureaazole;

[0019] (3) Triethylenediamine (6.73 g, 60.0 mmol, 1 eq) was dissolved in chloroform (100 mL), and Br was added dropwise thereto. 2 (20.0 g, 0.125 mol, 2.1 eq) in chloroform (100 mL), the resulting mixture was stirred under an inert atmosphere for 1 hour, the yellow precipitate was filtered off, washed with chloroform (50 mL), and dried in a vacuum oven at 40 ° C overnight to obtain DABCO-Br;

[0020] (4) Dissolve difunctional urea azole (2 g, 5.46 mmol, 1 eq) and DABCO-Br (5 g, 3.18 mmol, 0.58 eq) in dichloromethane (30 mL), stir and react under nitrogen at room temperature for 2 h, then filter and concentrate in vacuo to obtain the product.

[0021] The preparation method of DABCO-Br is as follows: in a 500 mL double-necked flask, triethylenediamine (6.73 g, 60.0 mmol, 1 eq) is dissolved in chloroform (100 mL). In the next step, Br is added dropwise using an addition funnel. 2 (20.0 g, 0.125 mol, 2.1 eq) in chloroform (100 mL); the resulting mixture was stirred under an inert atmosphere for 1 hour, the yellow precipitate was filtered off, washed with chloroform (50 mL), and dried in a vacuum oven at 40° C. overnight to obtain DABCO-Br. The MDI-TAD used in Examples 1-3 of the present application was prepared according to this method.

[0022] A thermosetting degradable polymer is prepared by the above method.

[0023] Application of the above-mentioned thermosetting degradable polymer in the preparation of degradable film.

[0024] The beneficial effects produced by the present invention are:

[0025] 1. The polymer prepared in the present invention can be degraded by microorganisms, which effectively improves the convenience of recycling and processing of thermosetting polymers, reduces the environmental pollution and resource waste problems existing in the existing methods for processing thermosetting polymers, and is a low-energy consumption thermosetting plastic recycling method.

[0026] 2. The thermosetting plastics in the present invention can be used as raw materials to produce thermosetting plastics or thermosetting products after recycling, thus realizing the low-temperature degradation and recycling of thermosetting plastics and reducing the waste of resources and the pollution to the environment. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 It is the synthesis process diagram of ITr;

[0028] Figure 2 is the FTIR spectrum of ITr;

[0029] Figure 3 For ITr 1 H-NMR and 13 C-NMR spectrum, where (a) is 1 H-NMR, (b) 13 C-NMR;

[0030] Figure 4 It is a diagram of the synthesis process of PIVA;

[0031] Figure 5 FTIR and 1 H-NMR spectrum; (a) is FTIR, (b) is 1 H-NMR;

[0032] Figure 6 This is a physical picture of PIVA and CPIVA-12.5;

[0033] Figure 7 This is a graph of microbial treatment results;

[0034] Figure 8 Schematic diagram of the preparation and recycling process of degradable thermosetting polymers, wherein 8a is a schematic diagram of the recycling process of thermosetting plastics, 8b is a synthetic route diagram of PIVA and CPIVA, and 8c is a schematic diagram of the reaction process of Tryp in E. coli solution;

[0035] Fig. 9 Figure 9 is a diagram of the cross-linking process and results of thermosetting polymers, wherein 9a is a schematic diagram of the synthesis of CPIVA film, 9b is a diagram of the dissolution results of PIVA and CPIVA, 9c is a diagram of the FTIR results, 9d is a diagram of the TG curves of PIVA and CPIVA, 9e is a diagram of the fluorescence spectra of PIVA and CPIVA, 9f is a diagram of the stress-strain curves of PIVA and CPIVA, and 9g is a diagram of the fracture energy results of PIVA and CPIVA;

[0036] Fig.10 UV-visible spectra of PIVA and CPIVA and DSC spectrum of CPIVA;

[0037] Fig.11 This is a diagram of the reaction process of CPIVA in E. coli culture medium;

[0038] Fig.12 This is a diagram of the biorecovery process of CPIVA;

[0039] Fig.13 Figure 13a is the ultraviolet absorption spectrum of the liquid culture medium after CPIVA was treated with E. coli, Figure 13b is the fluorescence spectrum of the liquid culture medium after CPIVA was treated with E. coli, and Figure 13c is the fluorescence spectrum of the liquid culture medium after CPIVA was treated with E. coli. 1 H-NMR graph, 13d is the fluorescence spectrum before and after CPIVA treatment, 13e is the FTIR graph before and after CPIVA treatment, and 13f is the FTIR graph after CPIVA treatment. 1 H-NMR diagram, 13g is a schematic diagram of the E. coli treatment process;

[0040] Fig.14 Mechanical properties diagram of the reconstructed IPVA;

[0041] Fig.15 This is the mechanical properties test results of CPIVA-x. DETAILED DESCRIPTION

[0042] In order to make the purpose, technical scheme and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention, that is, the embodiments described are only part of the embodiments of the present invention, rather than all of the embodiments.

[0043] Therefore, the following detailed description of the embodiments of the present invention is not intended to limit the scope of the invention claimed for protection, but merely represents selected embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without making creative work are within the scope of protection of the present invention.

[0044] It should be noted that relational terms such as "first" and "second" are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprises" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, an element defined by the sentence "comprises a ..." does not exclude the existence of other identical elements in the process, method, article or device including the element.

[0045] The features and performance of the present invention are further described in detail below in conjunction with the embodiments and drawings.

[0046] Example 1

[0047] A degradable thermosetting polymer, the preparation method of which is as follows:

[0048] (1) Synthesis of ITr: Under an inert atmosphere, 10 g of isophorone diisocyanate (IPDI) was dissolved in 100 ml of dichloromethane to prepare an IPDI solution; 10 g of tryptone (Tryp) and 1 g of dibutyltin dilaurate (DBTDL) were dissolved in dichloromethane to prepare a mixture solution, and then the mixture solution was added dropwise to the IPDI solution, and then the temperature was raised to 45°C for reaction. After reacting for 4 hours, it was purified by column chromatography. The solvent system of the column chromatography was petroleum ether: ethyl acetate = 1:1, and then the solvent was removed under reduced pressure to obtain a light yellow powder ( Figure 1 );

[0049] FTIR spectrum of synthesized ITr ( Figure 2 ) shows strong absorption bands at 3410 (stretching vibration of -OH and -NH), 2277 (stretching vibration of -NCO), 1700 (stretching vibration of C=O), 1600-1450 (skeleton vibration of indole ring) and 740cm -1 (Characteristic CH out-of-plane deformation vibration peak in indolebenzopyrrole structure).

[0050] 1 H-NMR (600 MHz, DMSO-d 6:δ=10.83(s,1H),7.54(d,J=7.9Hz,1H),7.34(d,J=8.3Hz,1H),7.17(s,1H), 7.07(t,J=7.2Hz,1H),7.04(s,1H),6.98(t,J=8.3Hz,1H),4.17(t,J=6.2Hz, 2H),3.65(d,J=7.9Hz,1H),3.09(s,2H),2.97(t,J=7.2Hz,2H),1.52(q,J=12 .2Hz,2H),1.02(d,J=6.2Hz,4H),0.97(s,3H),0.90(s,3H),0.89(s,3H)ppm.

[0051] 13 C-NMR (125 MHz, DMSO-d 6 :δ(ppm)=155.893(C),136.245(C),127.594(C),122.078(CH),122.055(C),12 1.815(CH)),119.431(CH),118.833(CH),112.238(C),111.17(CH),64.865(CH 2 ),57.012(CH 2 ),46.621(CH 2 ),46.081(CH 2 ),44.587(CH 2 ),41.568(CH),36.537(CH 3 ),34.944(CH 3 ),27.539(CH 2 ),26.854(CH 3 ),25.264(C),23.379(C); 1 H-NMR and 13 C-NMR spectrum is shown in Figure 3 ;

[0052] (2) Synthesis of indole functionalized polyvinyl alcohol (PIVA): Under an inert atmosphere, 4 g of PVA was dissolved in 100 ml of dimethyl sulfoxide (DMSO) to prepare a PVA solution, and then 19 g of ITr and 0.6 g of DBTDL solution were added thereto. The mixture was stirred at 40 °C for 4 h. After the reaction was completed, the mixture was poured into dichloromethane to suspend the polymer in the dichloromethane. The polymer was collected and vacuum dried, and then the polymer was purified using acetone to remove impurities to prepare PIVA. The specific synthesis process is shown in Figure 8 b-Ⅰ and Figure 4 ;

[0053] FTIR spectrum of PIVA ( Figure 5 a) At 3460, 2990, 2277, 1660, 1600, 1450, 1060 and 740 cm -1 It has characteristic absorption bands.

[0054] 1 H-NMR (600 MHz, DMSO-d 6 ): δ=10.83(s,1H),7.54(d,J=7.9Hz,1H),7.34(d,J=8.3Hz,1H),7.17(s,1H),7.07(t, J=7.2Hz, 1H), 7.04 (s, 1H), 6.98 (t, J=6.0Hz, 2H), 4.22 / 4.47 / 4.67 (s, 1H), 4.16 (t, J= 6.0Hz,1H),3.90(s,2H),3.84(s,1H),3.80(s,1H),2.96(t,J=12Hz,2H),2.72(s,2H), 1.99(s,2H),1.45(d,J=6.0Hz,2H),1.34(s,2H),0.97(d,J=12Hz,3H),0.90(s,6H)ppm. See Figure 5 b.

[0055] (3) Synthesis of cross-linked indole polyvinyl alcohol polymer (CPIVA): 2 g PIVA was dissolved in 10 ml DMSO to prepare PIVA solution; 2 mg MDI-TAD was dissolved in 2 ml DMAc solvent to prepare MDI-TAD solution; under stirring at 1000 rpm, the pre-cooled MDI-TAD solution was poured into the PIVA solution to prepare polymer CPIVA-12.5. The specific synthesis process is shown in Figure 8 b-Ⅱ; wherein 12.5 represents the molar fraction of MDI-TAD and indole in the initial mixture;

[0056] (4) Preparation of polymer film: The PIVA in step (2) and the CPIVA in step (3) are respectively prepared into polymer films by a casting method. Figure 6 .

[0057] Example 2

[0058] A degradable thermosetting polymer, the preparation method of which is as follows:

[0059] (1) Synthesis of ITr: Under an inert atmosphere, 20 g of isophorone diisocyanate (IPDI) was dissolved in 140 ml of dichloromethane to prepare an IPDI solution; 20 g of tryptophan (Tryp) and 1 g of dibutyltin dilaurate (DBTDL) were dissolved in dichloromethane to prepare a mixture solution, and then the mixture solution was added dropwise to the IPDI solution, and then the temperature was raised to 40°C for reaction. After reacting for 5 h, the mixture was purified by column chromatography, and the solvent system of the column chromatography was petroleum ether: ethyl acetate = 1:1, and then the solvent was removed under reduced pressure to obtain a light yellow powder;

[0060] (2) Synthesis of indole functionalized polyvinyl alcohol (PIVA): Under an inert atmosphere, 10 g of PVA was dissolved in 100 mL of dimethyl sulfoxide (DMSO) to prepare a PVA solution, and then 47.5 g of ITr and 0.8 g of DBTDL solution were added thereto. The mixture was stirred at 40 °C for 5 h. After the reaction was completed, the mixture was poured into dichloromethane to suspend the polymer in the dichloromethane. The polymer was collected and vacuum dried, and then the polymer was purified using acetone to remove impurities to prepare PIVA.

[0061] (3) Synthesis of cross-linked polyindole vinyl alcohol polymer (CPIVA): 2 g PIVA was dissolved in 10 ml DMSO to prepare PIVA solution, and 18 mg MDI-TAD was dissolved in 2 ml DMAc solvent to prepare MDI-TAD solution; under stirring at 1000 rpm, the pre-cooled MDI-TAD solution was poured into the PIVA solution to prepare polymer CPIVA-12.5;

[0062] (4) Preparation of polymer film: CPIVA was prepared into a polymer film by a casting method.

[0063] Example 3

[0064] A degradable thermosetting polymer, the preparation method of which is as follows:

[0065] (1) Synthesis of ITr: Under an inert atmosphere, 30 g of isophorone diisocyanate (IPDI) was dissolved in 150 ml of dichloromethane to prepare an IPDI solution; 30 g of tryptophan (Tryp) and 1 g of dibutyltin dilaurate (DBTDL) were dissolved in dichloromethane to prepare a mixture solution, and then the mixture solution was added dropwise to the IPDI solution, and then the temperature was raised to 50°C for reaction. After reacting for 3 hours, it was purified by column chromatography, and the solvent system of the column chromatography was petroleum ether: ethyl acetate = 1:1, and then the solvent was removed under reduced pressure to obtain a light yellow powder;

[0066] (2) Synthesis of indole functionalized polyvinyl alcohol (PIVA): Under an inert atmosphere, 20 g of PVA was dissolved in 100 ml of dimethyl sulfoxide (DMSO) to prepare a PVA solution, and then 77 g of ITr and 1.2 g of DBTDL solution were added thereto. The mixture was stirred at 50 °C for 3 h. After the reaction was completed, the mixture was poured into dichloromethane to suspend the polymer in the dichloromethane. The polymer was collected and vacuum dried, and then the polymer was purified using acetone to remove impurities to prepare PIVA.

[0067] (3) Synthesis of cross-linked polyindole vinyl alcohol polymer (CPIVA): 2 g PIVA was dissolved in 10 ml DMSO to prepare PIVA solution, and 150 mg MDI-TAD was dissolved in 2 ml DMAc solvent to prepare MDI-TAD solution; under stirring at 1000 rpm, the pre-cooled MDI-TAD solution was poured into the PIVA solution to prepare polymer CPIVA-12.5;

[0068] (4) Preparation of polymer film: CPIVA was prepared into a polymer film by a casting method.

[0069] Test example

[0070] 1. Bio-tailoring of Thermosetting Plastics

[0071] Using Escherichia coli (E. coli) as a representative example of microorganisms, the biological response of a small molecule compound (Tryp) in liquid culture medium of E. coli was studied (see 8c).

[0072] Preparation of E. coli liquid culture medium: weigh 0.85g soluble starch culture medium, 0.5g glucose and 50mL distilled water in a 100mL beaker, stir and boil, continue to boil for 10 minutes, cool to room temperature, and then put into a 250mL conical flask to obtain unsterilized glucose-starch culture solution. Seal the conical flask with cotton gauze and put it into a vertical high-pressure steam sterilizer. Set the autoclave at 121°C for 20 minutes for high-pressure steam sterilization; after sterilization, cool to room temperature and take it out, transfer it to the clean bench to inoculate E. coli, and put the inoculated liquid culture medium into a constant temperature incubator for cultivation for standby use.

[0073] The operation process is as follows: Taking the CPIVA plastic in Example 1 as an example, 2 mL of Escherichia coli liquid culture medium soaked with CPIVA plastic is placed in a small glass bottle, and then 2-3 mL of ether is added to the glass bottle, and indole is extracted into the ether by sufficient shaking. After standing for a period of time, the ether layer floats on the culture medium. At this time, 3-5 drops of Kovacs indole kit are slowly added along the bottle wall (do not shake the glass bottle after adding the reagent); if indole is present, the ether layer will be rose red, which is an indole positive reaction. On the contrary, if the ether layer is yellow or no yellow, it is a negative reaction. Different reaction results are shown in Figure 7 , the reaction process schematic diagram is shown in 8a.

[0074] The positive indole reaction results in this application show that Tryp can react with 4-dimethylaminobenzaldehyde after being cleaved by E. coli, and the solution turns red ( Figure 8 c-Ⅲ). This obvious color change indicates the presence of indole groups in the liquid culture medium. Therefore, it can be inferred that the change process of the polymer in this application is: the alkane side chain at the C3 position of the indole in Tryp is cut by E. coli, exposing the indole C3 position ( Figure 8 c-Ⅰ, Ⅱ); the exposed indole C3 position can be quickly replaced by 4-dimethylaminobenzaldehyde to form rose indole, making the solution red.

[0075] 2. Cross-linking of thermosetting plastics

[0076] In this application, the linear polymer PIVA and MDI-TAD are dissolved in DMSO and the covalently cross-linked thermosetting plastic (CPIVA) is prepared by a rapid click reaction at room temperature. Fig. 9 a; At room temperature, the obtained CPIVA is a transparent, non-sticky yellow solid; when the prepared PIVA is placed in different solvents, PIVA dissolves and disappears; when CPIVA is placed in different solvents, CPIVA curls and swells slightly, indicating that there are crosslinks in CPIVA (see Fig. 9 b and Table 1);

[0077] Table 1: Solubility of PIVA and CPIVA in different solvents

[0078] sample Methyl dimethacrylate Dimethyl sulfoxide dimethylformamide N-Methylpyrrolidone Tetrahydrofuran PIVA + + + + - CPIVA - - - - -

[0079] + means the polymer is completely soluble, - means the polymer is insoluble;

[0080] The structure of the prepared thermosetting plastic CPIVA was characterized and tested by FTIR and TG. The results showed that 2277 cm -1 The disappearance of the -N=N- stretching vibration peak at 100 nm indicates that there is almost no unreacted MDI-TAD in CPIVA, indicating that the conversion efficiency of MDI-TAD in the system is very high ( Fig. 9c). The thermogravimetric (TG) curve has a decomposition peak at 105°C, which is attributed to the covalent bond exchange of TAD-indole at high temperature ( Fig. 9 d). At the same time, the DSC curve of CPIVA shows an obvious glass transition peak at 90°C, further indicating that CPIVA is a thermosetting plastic ( Fig.10 b).

[0081] The click reaction between indole and TAD is competitive. TAD first reacts with the C2 position of indole without destroying the aromaticity of indole. The slight change in the fluorescence intensity of the polymer solution ( Fig. 9 e) and the retention of UV absorption peaks before and after cross-linking ( Fig.10 a) to confirm.

[0082] The uniaxial tensile test of CPIVA showed that the mechanical properties of CPIVA were significantly enhanced due to covalent crosslinking ( Fig. 9 f). The dynamic net effect shows a significant increase in tensile strength by about 2 times, from σPIVA = 26 MPa to σCPIVA-12.5 = 57 MPa. However, the covalent crosslinking restricts the mobility of the polymer chains, which is manifested in a slight increase in elongation at break (from 200% to 243%). In addition, the tensile toughness is significantly increased by 2.5 times, from 45.1 MJ m -3 Increased to 109MJ m -3 ( Fig. 9 g). This room temperature rapid click cross-linking method provides a controllable and simple operation method for constructing thermosetting plastics while ensuring the mechanical properties of the material.

[0083] Add different proportions of MDI-TAD to prepare CPIVA-x, and measure the mechanical properties of different CPIVA-x. Fig.15 The results showed that the mechanical properties of CPIVA plastics with different MDI-TAD ratios were much higher than those of PIVA films. Uniaxial tensile tests showed that the mechanical properties of CPIVA plastics were significantly enhanced due to covalent crosslinking. This room temperature rapid click crosslinking method provides a controllable and simple operation method for constructing thermosetting plastics while ensuring the mechanical properties of the material.

[0084] 3. Recycling of Thermosetting Plastics

[0085] First, CPIVA-12.5 plastic (6 cm × 3 cm, 0.05 mm thick) was immersed in liquid culture medium of E. coli. Changes in CPIVA-12.5 plastic were monitored by recording the macroscopic phenomena of the liquid culture medium and performing an indole positive test ( Fig.11). The indole positive test results showed that as the cutting progressed, indole groups gradually appeared in the liquid culture medium. Compared with the CPIVA-12.5 plastic, the residual plastic in the liquid culture medium showed a surprising dissolution phenomenon after about 50 days of reaction ( Fig.12 ).

[0086] The above liquid culture medium and residual plastic were characterized. Fig.13 a shows the UV absorption spectra of the liquid culture medium in the absence and presence of CPIVA-12.5 plastic. The liquid culture medium after cutting CPIVA-12.5 plastic produced a strong UV absorption peak at 256nm, which is an obvious π-π* transition absorption peak of the indole group ( Fig.13 a). In addition, the fluorescence spectrum also shows a strong fluorescence emission peak at 338nm ( Fig.13 b) Liquid culture medium 1 H-NMR spectroscopy further revealed the above transformation ( Fig.13 c). The characteristic H in the indole group (ITAD) is marked on the figure. 1 H-NMR spectroscopy showed that the ITAD fragment was cleaved by E. coli from CPIVA-12.5 plastic and dropped into the liquid culture medium.

[0087] The residual plastic was further characterized. First, the fluorescence spectrum of the CPIVA-12.5 plastic before and after cutting was tested. The spectrum clearly showed that the fluorescence intensity at 338nm was significantly reduced ( Fig.13 d), this is because CPIVA-12.5 plastic has a large number of indole luminescent groups. As the E. coli is cut, the indole groups gradually fall off, resulting in a significant decrease in the fluorescence intensity of the plastic. The FTIR spectra of CPIVA-12.5 plastic before and after cutting also obtained the same results ( Fig.13 e). First, the 740 cm-1 -1 The characteristic CH out-of-plane deformation vibration peak at 1600 cm -1 The skeleton vibration of benzene in the indole structure disappears in the residual plastic. In addition, the 1770 cm -1 The characteristic carbonyl stretching vibration peak at 20° disappears in the residual plastic. 1 H-NMR spectrum further revealed the above transformation ( Fig.13 f). 1 H-NMR spectra showed that E. coli cleaved the indole group (ITAD) from the CPIVA-12.5 plastic and dropped it into the liquid culture medium. It is worth noting that this structural transformation is highly consistent with the changes in the liquid culture medium mentioned above.

[0088] The specific bio-tailoring technology for E. coli is described as follows ( Fig.13 g). First, the indole groups in the cross-linked network can be accurately recognized by E. coli and the alkane side chain at the C3 position of the indole can be cut, thereby cutting the cross-linked network into a new linear polymer (NPVA) and an indole group (ITAD) ( Fig.13 g). Meanwhile, ITAD easily separated from CPIVA-12.5 plastic and fell into the liquid medium. NPVA still retained large fragments and floated in the liquid medium. NPVA dissolved in DMSO could be reconstituted into a thin film ( Fig.13 g), and the film still maintains considerable mechanical properties ( Fig.14 ), can be used for plastic packaging materials.

Claims

1. A method for preparing a thermosetting degradable polymer, characterized in that: The following steps are involved: (1) Synthesis of ITr: Under an inert atmosphere, IPDI is dissolved in a low boiling point solvent to prepare an IPDI solution; Tryp and DBTDL are dissolved in dichloromethane to prepare a mixed solution, the mixed solution is added dropwise to the IPDI solution, and then heated to complete the reaction, purified, and dried to obtain ITr; (2) Synthesis of PIVA: Under an inert atmosphere, PVA was dissolved in DMSO to prepare a PVA solution, ITr and DBTDL were added thereto, and stirred until completely dissolved, and the mixture solution was heated to react. After the reaction was completed, the mixture solution was poured into dichloromethane, and the solid polymer was collected and impurities were removed to prepare PIVA; (3) Synthesis of CPIVA: PIVA was dissolved in DMSO and MDI-TAD was dissolved in DMAc. Under high-speed stirring conditions, the MDI-TAD solution was poured into the PIVA solution to obtain CPIVA.

2. The method for preparing a thermosetting degradable polymer according to claim 1, characterized in that: In step (1), the mass ratio of IPDI:Tryp:DBTDL is 10-30:10-30:1; the mass concentration of the IPDI solution is 100-200 g / L; and the mass concentration of Tryp in the mixture solution is 100-200 g / L.

3. The method for preparing a thermosetting degradable polymer according to claim 1, characterized in that: In step (1), the heating reaction temperature is 40-50° C. and the reaction time is 3-5 h.

4. The method for preparing a thermosetting degradable polymer according to claim 1, characterized in that: In the mixed solution of step (2), the mass concentration of PVA is 40-200 g / L, the mass concentration of ITr is 190-770 g / L, and the mass concentration of DBTDL is 6-12 g / L.

5. The method for preparing a thermosetting degradable polymer according to claim 1, characterized in that: In step (2), the heating reaction temperature is 40-50° C. and the reaction time is 3-5 h.

6. The method for preparing a thermosetting degradable polymer according to claim 1, characterized in that: In step (3), the mass ratio of PIVA to MDI-TAD is 1000:1-75, and the reaction temperature is 0-25°C.

7. The method for preparing a thermosetting degradable polymer according to claim 1, characterized in that: The preparation method of MDI-TAD in step (3) is as follows: (1) dissolving ethyl carbazate and 4,4'-methylenebis(phenyl isocyanate) in an organic solvent respectively, and then mixing the two solutions in a protective gas atmosphere, stirring and reacting at room temperature for 1-3 hours, then heating to 85-95° C., stirring and reacting for 1-3 hours, and then filtering and washing to obtain a difunctional semicarbazide; (2) dissolving the difunctional semicarbazide in alkaline solution, reflux at 90-120° C. for 1-3 h, then acidifying and filtering to obtain the difunctional ureaazole; (3) Dissolve the difunctional urea azole and DABCO-Br in an organic solvent, stir and react at room temperature for 1-3 hours, then filter and concentrate in vacuo to obtain the product.

8. A thermosetting degradable polymer, characterized in that: The method is prepared by the method described in any one of claims 1 to 7.

9. Use of the thermosetting degradable polymer according to claim 8 in the preparation of a film.

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