A high-performance bisindole crown ether-based polyurethane and its preparation method

Abstract

The present invention discloses a high-performance bis-indole crown ether-based polyurethane and its preparation method. The preparation method comprises: reacting a crown ether polyol containing a cationic-π structure with fluoroone diisocyanate and polyethylene glycol through a condensation reaction to prepare the polyurethane material. The tensile strength and elongation at break of the polyurethane material prepared by the present invention are increased by 76% and 24.4%, respectively, and the fracture energy is increased from 41.0 MJ / m 3 Increased to 79.2MJ / m 3 At the same time, its thermal decomposition temperature and glass transition temperature are also higher, indicating that the overall mechanical properties of the polyurethane material prepared by the present invention have been significantly improved.

Description

Technical Field

[0001] The invention belongs to the technical field of polyurethane preparation, and particularly relates to a high-performance bisindole crown ether-based polyurethane and a preparation method thereof. Background Art

[0002] Polyurethane's exceptional mechanical properties are primarily due to the abundance of urethane groups in its backbone. With advancements in technology, conventional polyurethane materials are no longer able to meet the demands of cutting-edge industries, which demand higher performance. Traditional methods of strengthening and toughening polyurethanes primarily involve adding inorganic fillers or increasing crosslinking points between molecular chains. However, high crosslink density restricts molecular chain mobility, reducing the material's toughness and limiting its application. Therefore, resolving the inherent contradiction between material strength and toughness has long been a key research topic in polymer chemistry.

[0003] In recent years, as the reversible dynamics and chemical stability of dynamic bonds have begun to attract scientists' attention, many researchers have successfully constructed polymer materials with improved strength and toughness based on hydrogen bonds, metal coordination, and cation-π. The advantage of dynamic bonds is that their bond energy is lower than that of traditional covalent bonds. They can preferentially break before the material is damaged to dissipate energy, and can strengthen and toughen the material without sacrificing the mechanical properties of the material. However, the introduction of dynamic bonds cannot avoid the increase in the cross-linking density of the polyurethane molecular chain, which limits the application scenarios of the material. Therefore, how to develop a method to strengthen and toughen the material without changing the cross-linking point density of the material remains a challenge. Summary of the Invention

[0004] In view of the above-mentioned deficiencies in the prior art, the present invention provides a high-performance bisindole crown ether-based polyurethane, which can improve the performance of the material without changing the cross-linking point of the material.

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

[0006] A method for preparing high-performance bisindole crown ether-based polyurethane is disclosed, wherein the polyurethane is prepared by polycondensation reaction of a crown ether polyol containing a cationic-π structure with fluoroone diisocyanate and polyethylene glycol.

[0007] Furthermore, the preparation method is as follows:

[0008] In a protective gas atmosphere, fluoroketone diisocyanate, polyethylene glycol and dibutyltin dilaurate are prepolymerized at 80-100° C. for 1-2 hours, and then a crown ether polyol containing a cationic-π structure is added.

[0009] Furthermore, the mass ratio of crown ether polyol, fluoroquinone diisocyanate and polyethylene glycol is 0.5-1:0.1-0.5:0.1-0.5.

[0010] Furthermore, a crown ether polyol containing a cation-π structure is prepared by reacting metal ions with bisindole crown ether diol.

[0011] Furthermore, the polyethylene glycol is polyethylene glycol 400.

[0012] Furthermore, the metal ion is potassium ion, sodium ion or calcium ion.

[0013] Furthermore, the preparation method of bisindole crown ether diol is as follows:

[0014] (1) After dissolving the crown ether, a catalyst is added, and the mixture is refluxed at 80-85° C. for 1-2 hours. Then, a 3-2-bromoethyl indole solution is added under a protective gas atmosphere, and the mixture is refluxed for 20-30 hours to obtain a bisindole crown ether;

[0015] (2) Dissolve the bisindolyl crown ether and add sodium hydride, stir in an ice bath for 1 to 2 hours, then add bromoethoxy tert-butyldimethylsilane solution, stir and react at 80 to 100° C. for 3 to 5 hours to obtain bisindolyl crown ether ethoxy tert-butyldimethylsilane;

[0016] (3) Dissolving bisindole crown ether ethoxy tert-butyldimethylsilane and performing a desilylation reaction to prepare bisindole crown ether diol.

[0017] Furthermore, in step (1), the crown ether is an aza crown ether, and the mass ratio of the aza crown ether to 3-2-bromoethylindole is 0.5-1:0.8-2.

[0018] Furthermore, in step (1), the mass ratio of crown ether to 3-2-bromoethylindole is 0.5-1:0.8-2.

[0019] Furthermore, the crown ether in step (1) is an azacrown ether.

[0020] Furthermore, the crown ether is diaza-18-crown-6 or 4,10-diaza-12-crown-4-ether.

[0021] Furthermore, the catalyst is at least one of sodium carbonate and sodium iodide.

[0022] Furthermore, in step (1), the solvent for dissolving the crown ether and 3-2-bromoethylindole is anhydrous acetonitrile.

[0023] Furthermore, in step (2), the mass ratio of bisindole crown ether to bromoethoxy tert-butyldimethylsilane is 1-1.5:1.2-2.0.

[0024] Furthermore, in step (2), the solvent for dissolving the bisindole crown ether and bromoethoxy tert-butyldimethylsilane is anhydrous N,N-dimethylformamide.

[0025] Furthermore, in step (3), tetrabutylammonium fluoride with a concentration of 1 to 1.5 mol / L is used to remove the silyl groups in bisindole crown ether ethoxy tert-butyldimethylsilane.

[0026] Furthermore, the concentration of tetrabutylammonium fluoride is 1 mol / L.

[0027] Furthermore, step (3) further includes the following process after the reaction is completed:

[0028] After the reaction is completed, the organic phase is extracted with petroleum ether, and then the organic phase is extracted with water. The aqueous phase is collected, and then sodium chloride is added to the aqueous phase until the solution is saturated. After standing, the precipitated solid phase product, namely bisindole crown ether diol, is collected.

[0029] Furthermore, in step (3), the solvent for dissolving bisindole crown ether ethoxy tert-butyldimethylsilane and tetrabutylammonium fluoride is tetrahydrofuran.

[0030] A high-performance bisindole crown ether-based polyurethane is prepared by the method.

[0031] Beneficial effects of the present invention:

[0032] 1. The present invention uses crown ether polyol, isophorone diisocyanate and polyethylene glycol as the main component for preparing polyurethane, wherein, in the crown ether polyol, contain cation-π structure, have dynamic retractable functional characteristic, use it as polyurethane main chain, realize the retractable behavior of polyurethane macromolecular chain under external force, thereby reach the purpose of polyurethane strengthening and toughening.Then introduce isophorone diisocyanate and polyethylene glycol 400 that do not contain aromatic ring structure on this basis, isophorone diisocyanate can further enhance the mechanical property of polyurethane film, promotes its transparency.Simultaneously, polyethylene glycol 400 can not use solvent polymerization, and more easily synthesizes low molecular prepolymer, also reduces dissolution pollution.

[0033] 2. The yield of the bisindole crown ether diol prepared by the present invention can reach 91.1%. The yield of the functional element potassium-bisindole crown ether diol prepared on this basis can reach 99%, indicating that the preparation method constructed by the present invention has excellent effect.

[0034] 3. The tensile strength and elongation at break of the polyurethane material prepared by the present invention are increased by 76% and 24.4% respectively, and the fracture energy is increased from 41.0MJ / m 3 Increased to 79.2MJ / m 3 At the same time, its thermal decomposition temperature and glass transition temperature are also higher, indicating that the overall mechanical properties of the polyurethane material prepared by the present invention are significantly improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1FT-IR spectra of K-BCEPU and IPDI;

[0036] Figure 2 is the energy spectrum of K-BCEPU;

[0037] Figure 3 The UV absorption spectra of BCEPU and K-BCEPU and their difference spectra;

[0038] Figure 4 is the fluorescence spectra of BCEPU and K-BCEPU;

[0039] Figure 5 Comparison of the structural changes and H-NMR spectra of BCEPU and K-BCEPU;

[0040] Figure 6 Thermal decomposition curves of BCEPU and K-BCEPU

[0041] Figure 7 DSC curves of BCEPU and K-BCEPU;

[0042] Figure 8 The tensile test results of BCEPU and K-BCEPU are shown;

[0043] Figure 9 Cyclic tensile test results of BCEPU and K-BCEPU

[0044] Figure 10 Diagram of the mechanism for strengthening and toughening polymers with stretchable functional elements. DETAILED DESCRIPTION

[0045] The specific embodiments of the present invention are described below to facilitate understanding of the present invention by those skilled in the art. However, it should be clear that the present invention is not limited to the scope of the specific embodiments. For those skilled in the art, as long as various changes are within the spirit and scope of the present invention as defined and determined by the appended claims, these changes are obvious, and all inventions and creations utilizing the concepts of the present invention are protected.

[0046] Example 1 Synthesis of polyurethane

[0047] 1. Synthesis of bromoethoxy tert-butyldimethylsilane (Br-OTBMS)

[0048] Weigh tert-butyldimethylsilyl chloride (8.3 g, 55 mmol) and imidazole (3.74 g, 55 mmol), dissolve them in anhydrous N,N-dimethylformamide (20 mL), and add them to a reaction flask under nitrogen. Then, weigh bromoethanol (6.25 g, 50 mmol) in a weighing bottle and add it to the reaction flask. React at room temperature for 15 hours. The reaction process is as follows:

[0049]

[0050] After the reaction time is over, 50mL of 10% sodium bicarbonate solution is prepared and slowly added to the reaction flask to quench until no bubbles are generated. After quenching, the liquid in the reaction flask is poured into a separatory funnel and extracted three times with n-hexane (3×100mL), the organic phase is collected, and the organic phase is washed once with saturated brine. After washing, an appropriate amount of anhydrous magnesium sulfate is added to the organic phase. After drying for one hour, the anhydrous magnesium sulfate is removed by filtration under reduced pressure, and the filtered liquid is transferred to a round-bottom flask and the solvent is evaporated by vacuum distillation using a rotary evaporator to obtain a colorless liquid. The colorless liquid is transferred to an evaporating dish and vacuum dried for 10 hours to obtain a colorless liquid product (9.30g, 41.5mmol) with a yield of 83%. Its NMR data are as follows:

[0051] 1 H NMR (600MHz, CDCl3): δ = 0.09 (s, 6H), 0.91 (s, 9H), 3.38 (t, J = 6.0Hz, 2H), 3.89 (t, J = 6.0Hz, 2H) ppm; 13 C NMR (100MHz, CDCl3): δ=-5.30, 18.2, 25.8, 33.1, 63.48ppm.

[0052] 2. Synthesis of 3-(2-bromoethyl)indole (BRI)

[0053] Tryptone (1.61 g, 10 mmol) and triphenylphosphine (2.75 g, 10.5 mmol) were weighed and dissolved in dichloromethane (40 mL) and added to a reaction flask with stirring to dissolve. Carbon tetrabromide (3.47 g, 10.5 mmol) was dissolved in dichloromethane and added to a dropping funnel. The carbon tetrabromide solution was slowly added dropwise in an ice bath, controlling the addition to be complete within half an hour. The reaction process is as follows:

[0054]

[0055] After the addition was complete, the ice bath was removed and the reaction was carried out at room temperature in the dark. Thin layer chromatography (petroleum ether: ethyl acetate 4:1, R f =0.4) to detect the reaction. Two hours after the addition of carbon tetrabromide solution, water was added to quench the reaction, and the mixture was poured into a separatory funnel. The organic phase was washed twice with water and once with saturated brine. After washing, an appropriate amount of anhydrous magnesium sulfate was added to the organic phase to remove water. After drying, the magnesium sulfate was removed by filtration under reduced pressure, and the resulting solution was concentrated under reduced pressure to obtain a brown oil. Finally, it was purified by column chromatography (petroleum ether: ethyl acetate = 4:1, R f=0.4). After distillation under reduced pressure, a brown solid product (1.92 g, 8.6 mmol) was obtained with a yield of 86%. Its NMR data are as follows:

[0056] 1 H NMR (600MHz, CDCl3): δ = 3.33 (t, J = 7.8Hz, 2H), 3.63 (t, J = 7.8Hz, 2H), 7.08 (s, 1H), 7.1 4(t,J=7.2Hz,1H)7.21(t,J=7.2Hz,1H)7.36(d,J=6.0Hz,1H)7.58(d,J=6.0Hz,1H)ppm; 13 C NMR (151MHz, CDCl3): δ = 29.3, 32.9, 111.0, 113.3, 118.2, 119.4, 122.2, 122.2, 126.7, 136.1ppm; HRMS (BRI): calcd.for C 10 H 10 BrN[M+H] + 223.9997,found234.0071.

[0057] 3. Synthesis of bisindole crown ether (BCE)

[0058] Weigh diaza-18-crown-6 (5.24 g, 20 mmol) and dissolve it in anhydrous acetonitrile (20 mL) and add it to a round-bottom flask. Weigh sodium carbonate (10.6 g, 100 mmol) and sodium iodide (0.3 g, 2 mmol) and add them to the reaction flask. Heat the mixture to 85°C and reflux for 1 hour. Weigh 3-2-bromoethylindole (9.86 g, 44 mmol) and dissolve it in anhydrous acetonitrile (20 mL). Add the mixture dropwise under nitrogen, controlling the addition to be complete within one hour. The reaction process is as follows:

[0059]

[0060] After the addition was complete, the mixture was refluxed for 24 hours and analyzed by thin layer chromatography (petroleum ether: acetone: triethylamine = 10:10:1, R f =0.35) to monitor the reaction. After the reaction is completed, the sodium carbonate and sodium iodide are filtered under reduced pressure, and the filtrate is collected and the solvent is distilled off under reduced pressure to obtain a brown-yellow oily crude product. The oily crude product is dissolved in dichloromethane and washed with water twice, and washed once with saturated brine. After washing, an appropriate amount of anhydrous magnesium sulfate is added to the organic phase until the magnesium sulfate no longer clumps and can flow. After drying, the magnesium sulfate is removed by filtration under reduced pressure, and the resulting solution is concentrated under reduced pressure to obtain a brown-yellow oil. Finally, it is purified by column chromatography, wet loading, and the eluent ratio is petroleum ether: acetone: triethylamine = 10:10:1 (R f=0.35), and the solvent was removed by distillation under reduced pressure to obtain a yellow solid product. Finally, it was recrystallized from ethanol to obtain light yellow crystals (3.19 g, 6.5 mmol) with a yield of 32.8%. Its NMR data are as follows:

[0061] 1 H NMR (600MHz, CDCl3): δ = 2.91 (t, J = 12Hz, 8H), 3.62 (s, 4H), 3.66 (t, J = 8.4Hz, 4H), 7.10 (t,J=7.8Hz,1H)7.11(s,1H)7.32(d,J=12Hz,1H)7.58(d,J=8.4Hz,1H)8.37(s,1H)ppm; 13 C NMR (151MHz, CDCl3): δ = 23.2, 54.5, 56.7, 70.3, 111.4, 114.2, 119.0, 119.3, 121.9, 122.6, 127.9, 136.5ppm; HRMS (BCE): calcd.for C 32 H 44 N4O4[M+H] + 549.3363,found549.3435.

[0062] 4. Synthesis of bisindole crown ether ethoxy tert-butyldimethylsilane (BCE-OTBD)

[0063] Weigh bisindol crown ether (1.1 g, 2 mmol) and dissolve it in anhydrous N,N-dimethylformamide (20 mL) and add it to a round-bottom flask. Weigh sodium hydride (60%) (0.192 g, 8 mmol) and add it to the reaction flask. Stir in an ice bath for one hour. Weigh bromoethoxy tert-butyldimethylsilane (1.43 g, 6 mmol) and dilute it with anhydrous N,N-dimethylformamide (5 mL) and add it to the dropping funnel. Control the addition to be complete over 30 minutes. The reaction process is as follows:

[0064]

[0065] After the addition was complete, the temperature was raised to 100°C and stirred for 4 hours. The mixture was analyzed by thin layer chromatography (petroleum ether: ethyl acetate: triethylamine = 10:10:1, R f=0.5) to monitor the reaction. After the reaction is completed, water is added to quench the reaction, the solution is poured into a separatory funnel and ethyl acetate (100 mL) is added. The organic phase is washed twice with distilled water and once with saturated brine. After washing, an appropriate amount of anhydrous magnesium sulfate is added to remove water. After drying, the magnesium sulfate is filtered off under reduced pressure, and the resulting solution is distilled under reduced pressure to obtain a yellow oil. It is purified by column chromatography, wet column loading, and the eluent ratio is petroleum ether: ethyl acetate: triethylamine = 10:10:1, Rf = 0.4. After removing the solvent by distillation under reduced pressure, a light yellow oily product (1.433 g, 1.65 mmol) is obtained with a yield of 82.9%. Its nuclear magnetic resonance data are as follows:

[0066] 1 H NMR (600MHz, CDCl3): δ = 0.00 (s, 6H), 0.95 (s, 9H), 2.99 (q, J1 = 3.6Hz, J2 = 6Hz 4H), 3.05 (t, J = 5.4Hz, 4H) 3.78 (s, 4H) 3.81 (t, J = 6Hz, 4H) 4.0 0(t,J=5.4Hz,2H)4.00(t,J=6.0Hz,2H)7.06(s,1H)7.20(t,J=7.8Hz,1H)7.30(t,J=7.8Hz,1H)7.41(d,J=9Hz,1H)7.69(d,J=9Hz,1H)ppm; 13 C NMR (151MHz, CDCl3): δ=-5.4,18.0,22.9,25.7,48.3 54.0,56.8 62.4 70.0 70.8,109.2 113.0,118.4,118.9,121.2,125.8,127.8,136.3ppm; HRMS(BCE-OTBD):calcd.for C 48 H 80 N4O6Si2[M+H] + 865.5616, found 865.5691.

[0067] 5. Synthesis of bisindole crown ether diol (BCEG)

[0068] Weigh BCE-OTBD (1.56 g, 1.8 mmol) and dissolve it in tetrahydrofuran (20 mL). Add the solution to a 100 mL single-necked round-bottom flask. Add 1 mol / L tetrabutylammonium fluoride (3 mL) in tetrahydrofuran to the solution and stir at room temperature for 1 hour. The reaction process is as follows:

[0069]

[0070] Then thin layer chromatography (dichloromethane: methanol: triethylamine 20:1:1, Rf =0.45) to monitor the progress of the reaction. After the reaction is completed, water is added to quench the reaction, and the reaction solution is transferred to a separatory funnel and petroleum ether is added thereto. The organic phase is extracted three times with water, and the product is transferred to the aqueous phase. Sodium chloride is added to the aqueous phase until the solution is saturated. At this time, it can be observed that the aqueous phase changes from clear and transparent to turbid. Seal it with plastic wrap and let it stand overnight. After one day, a white solid was found to be precipitated in the beaker. The white solid was obtained by filtration under reduced pressure and washed with acetonitrile several times. After drying, a white crystalline product (1.04g, 1.63mmol) was obtained with a yield of 91.1%. Its nuclear magnetic data are:

[0071] 1 H NMR (600MHz, DMSO-d6): δ = 3.18 (dd, J1 = 9Hz J2 = 9.6Hz 2H), 3.39 (t, J = 4.8Hz.6H), 3.58 (5, J1 = 3.6Hz, J2 = 6Hz 4H), 3.69 (s, 2H) 3.85 (t, J = 6Hz 4H) 4.16 (d, J = 6Hz, 2H) 5.01 (s, 1H) 7.02 (t, J = 7.2Hz, 1H) 7.11 (dd, J1 = 7.8Hz J2 = 7.8Hz 1H) 7.27 (d, J = 4.8Hz, 1H) 7.30 (dd, J1 = 8.4Hz J2 = 8.4Hz 1H)7.63 (dd, J1=3.6Hz J2=3.6Hz 1H)ppm; 13 CNMR (151MHz, DMSO-d6): δ = 18.2, 48.3, 54.1, 56.5, 62.6, 70.0, 70.5, 110.1, 112.0, 118.6, 118.9, 121.0, 127.0, 128.1, 136.6ppm; HRMS (BCEG): calcd.for C 36 H 52 N4O6[M+H] + 637.3887,found 637.3960.

[0072] 6. Preparation of functional element potassium-bisindole crown ether diol (K-BCEG)

[0073] Weigh bisindole crown ether diol (0.63 g, 1 mmol) and dissolve it in deionized water. Add it into a 50 mL beaker, and add potassium hexafluorophosphate (0.22 g, 1.2 mmol). The reaction process is as follows:

[0074]

[0075] During the stirring process, the solution turned from clear to turbid. This is because water is a good solvent for the raw material. After the crown ether coordinates the potassium ion, the polarity of the product decreases. Water is a poor solvent for the product. After a period of time, the solid was filtered under reduced pressure and dissolved in acetonitrile. At this time, the organic phase contained dissolved product and potassium hexafluorophosphate. The acetonitrile was removed by distillation under reduced pressure to obtain a white mixture of product and potassium hexafluorophosphate. The potassium hexafluorophosphate was washed with water and dried to obtain pure white crystalline product potassium-bisindole crown ether diol (K-BCEG) (0.7g, 99%). The yield was 99%. Its nuclear magnetic resonance data are:

[0076] 1 H NMR (600MHz, DMSO-d6): δ = 3.10 (s, 2H), 3.41 (s, 2H), 3.46 (s 4H), 3.59 (s, 4H) 3.69 (dd, J1 = 4.8Hz J2 = 5.4Hz 2H) 3.74 (s, 2H) 4.16 (t, J = 5.4Hz 2H) 4.86 (t, J = 4.2Hz, 1H) 7.05 (t, J = 7.2Hz 1H) 7.14 (t, J = 7.8Hz, 1H) 7.28 (s, 1H) 7.63 (d, J1 = 4.2Hz 1H) 7.58 (d, J1 = 7.2Hz 1H) ppm; 13 C NMR (151MHz, DMSO-d6): δ = 20.0, 48.6, 52.5, 54.2, 60.6, 64.8, 69.9, 108.3, 110.4, 118.8, 119.09, 121.9, 127.2, 127.8, 136.8ppm; HRMS (K-BCEG): calcd.for C 36 H 52 N4O6K + [M+H] + 676.3518,found 676.3584.

[0077] 7. Synthetic K-BCEPU polyurethane

[0078] Isophorone diisocyanate (0.44 g, 2 mmol), polyethylene glycol 400 (0.4 g, 1 mmol), and dibutyltin dilaurate (3 wt%) were added to a branch-necked flask under a nitrogen atmosphere and prepolymerized at 80°C for one hour with stirring. During stirring, bubbles were observed in the flask and the viscosity gradually increased. Adjust the stirring speed to ensure uniform stirring.

[0079] After the prepolymerization, potassium-bisindole crown ether diol (0.67 g, 1 mmol) was dissolved in 1 mL of anhydrous N, N-dimethylformamide and then added to the prepared prepolymer. The reaction was then continued to stir at 85 °C until the isocyanate titration showed complete disappearance, and finally the K-BCEPU polymer was formed.

[0080] 8. Synthetic BCEPU polyurethane

[0081] The preparation method is the same as that of K-BCEPU polyurethane, except that the potassium-bisindole crown ether diol used is replaced by bisindole crown ether diol.

[0082] Example 2K-BCEPU polyurethane material characterization

[0083] 1. FT-IR detection

[0084] FT-IR spectrum is the most commonly used method for characterizing polyurethane. Figure 1 As shown, the 2260 cm -1 The isocyanate absorption peak disappears, indicating that the isocyanate group has reacted completely, thus proving the successful preparation of polyurethane.

[0085] 2. EDS spectrum test

[0086] The element distribution on the surface of K-BCEPU polyurethane film was detected by EDS spectrum. The results are as follows: Figure 2 As shown, it can be seen that K ions are evenly distributed in the K-BCEPU film, indicating that we have successfully introduced potassium ions into the polymer film.

[0087] 3. UV detection

[0088] BCEPU and K-BCEPU films were characterized by UV absorption spectroscopy. Figure 3 As shown in the figure, a pair of positive and negative bands appear at 260nm / 274nm in the UV difference spectrum of the two, which is consistent with the phenomenon reported in the literature, indicating that the potassium ions in the crown ether ring have an impact on the electron cloud density of indole, and indirectly proves the existence of cation-π interaction in the K-BCEPU chain.

[0089] 4. Fluorescence detection

[0090] BCEPU and K-BCEPU films were tested using fluorescence spectroscopy. Figure 4Compared with BCEPU, the fluorescence of K-BCEPU film was significantly weakened and blue-shifted, indicating that the bisindole crown ether diol unit in the polyurethane chain constructed a folded and telescopic structure after the introduction of potassium ions. The potassium ions in the crown ether ring produced cation-π interactions with the indole groups connected on both sides of the ring, thereby affecting the electron cloud density of indole and causing its fluorescence to weaken.

[0091] 5. H NMR spectroscopy

[0092] BCEPU and K-BCEPU were tested by NMR respectively. The results are shown in Figure 5 In the figure, after the introduction of potassium ions as functional units, the hydrogen atoms on the indole and crown ether of the bisindole crown ether diol have shifted to varying degrees. Similarly, the H NMR spectrum of K-BCEPU has also shifted to varying degrees compared with BCEPU. The hydrogen atoms (H1-H5) on the indole of K-BCEPU have shifted to higher fields, while the hydrogen atoms on the crown ether (H 10 -H 12 ) undergoes a small upfield shift, while the hydrogen on isophorone diisocyanate and polyethylene glycol does not shift. In summary, it can be proved that there is a cation-π interaction in the K-BCEPU polymer chain.

[0093] Example 3 Polyurethane Performance Test

[0094] 1. Determination of thermal decomposition temperature

[0095] The thermal decomposition temperature of BCEPU and K-BCEPU films were tested by TGA. The results are shown in Figure 6 As shown in the figure, the weight loss temperature of BCEPU 5% is T 5％ =251℃, and after the cation-π interaction between potassium ions and indole is used to form polyurethane with foldable and retractable functional units, the thermal decomposition temperature T 5％ The decomposition temperature reached 259°C, a slight increase compared to BCEPU, indicating that the addition of retractable functional units can improve the thermal stability of polyurethane to a certain extent. However, the residual carbon rate of K-BCEPU was significantly higher than that of BCEPU. This is because K-BCEPU contains potassium ions. During the heating process, the polymer decomposes and loses weight, and the potassium ions form inorganic substances that remain in the crucible, resulting in an increase in the residual carbon rate.

[0096] 2. Glass transition temperature detection

[0097] The glass transition temperature of BCEPU and K-BCEPU was tested, and the results are shown in Figure 7 As can be seen from the figure, the T g is 28℃, but after adding K ions, the T gIncrease to 36 ° C. With other dynamic bonds, the T of the polymer is increased by increasing the cross-linking density. g The method is different, K-BCEPU's T g The reason for the significant improvement is that the introduction of potassium ions causes the indole and crown ether rings to fold, and the indole and K ions in the crown ether rings form a strong cation-π interaction, thereby restricting the rotation of the molecular conformation and the movement of the chain segments, making the flexibility of the molecular chain worse, and ultimately increasing the glass transition temperature of the polymer.

[0098] 3. Tensile test

[0099] BCEPU and K-BCEPU were subjected to tensile tests, and the results are shown in Figure 8 As shown in the figure, the tensile strength of the BCEPU film without functional units is 16.5 MPa, the elongation at break is 384%, and the fracture energy is 41.0 MJ / m 3 At this time, the main sources of energy dissipation in the film are entanglement, friction and molecular orientation between molecular chains. When the stretchable functional unit is introduced, the tensile strength of K-BCEPU increases to 29Mpa, the elongation at break also increases to 478%, and the fracture energy increases to 79.2MJ / m 3 Compared with BCEPU, the tensile strength of K-BCEPU increased by 76%, the elongation at break increased by 24.4%, and the breaking energy increased by 93%, achieving a simultaneous improvement in mechanical properties.

[0100] This shows that the introduction of functional units causes the easily broken cation-π interaction to be destroyed first and dissipate energy during the stretching process of the polymer chain. However, the molecular chain does not break at this time. Instead, the functional units stretch under the action of external force, causing the polymer chain to lengthen. Therefore, the toughness of the material increases, and the elongation at break and fracture energy increase.

[0101] 4. Cyclic tensile test

[0102] Cyclic tensile tests were carried out on BCEPU and K-BCEPU, respectively. The specific process is as follows:

[0103] The two sample films were stretched to a stress exceeding their yield strength, and unloaded when the strain reached 50% to examine the energy consumption during the loading and unloading process under the action of force, and to characterize the recovery ability of the material. The test results are shown in Figure 9 .

[0104] As shown in the figure, the two films were subjected to 5 loading-unloading cyclic stretching experiments. The comparison results showed that under the same strain conditions, BCEPU ( Figure 9 (a)) is significantly weaker than that of K-BCEPU ( Figure 9At the same time, the elastic hysteresis phenomenon of K-BCEPU during the unloading process is more obvious than that of BCEPU, which indicates that the dissipated energy of K-BCEPU is larger than that of mechanical loading, and it can effectively dissipate the energy caused by external force.

[0105] The above results are due to the fact that during the stretching process, the energy dissipation of BCEPU mainly comes from the slippage of the chain segments and the orientation of the molecules. When the external force is removed, the chain slippage and molecular orientation will recover slowly due to the friction between the molecules, causing the recovery rate in the second cycle to begin to decline significantly. In addition to the chain slippage and molecular orientation, the energy dissipation of K-BCEPU also comes from the cation-π interaction between the cation in the crown ether ring in the functional unit and the adjacent indole. Therefore, when the external force is removed, the metal ion will attract the indole on the side arm to reversibly reconstruct the cation-π interaction ( Figure 10 ), resulting in a significantly greater strain recovery rate after cyclic stretching than BCEPU. The cyclic stretching test results further demonstrate the existence of reversible dynamic changes in the polymer chain.

[0106] Finally, it should be noted that the above specific implementation methods are only used to illustrate the technical solutions of the present invention and are not limiting. Although the present invention has been described in detail with reference to examples, those skilled in the art should understand that the technical solutions of the present invention can be modified or replaced by equivalents without departing from the spirit and scope of the technical solutions of the present invention, which should all be included in the scope of the claims of the present invention.

Claims

1. A method for preparing a high-performance bisindole crown ether-based polyurethane, characterized in that: It is prepared by polycondensation reaction of crown ether polyol containing cationic-π structure with isophorone diisocyanate and polyethylene glycol. The crown ether polyol containing a cation-π structure is prepared by reacting metal ions with bisindole crown ether diol.

2. The preparation method according to claim 1, characterized in that The mass ratio of the crown ether polyol containing a cationic-π structure, isophorone diisocyanate and polyethylene glycol is 0.5-1:0.1-0.5:0.1-0.

5.

3. The preparation method according to claim 1, characterized in that The metal ions are potassium ions, sodium ions or calcium ions.

4. The preparation method according to claim 1, characterized in that The preparation method of the bisindole crown ether diol is as follows: (1) After dissolving the crown ether, add the catalyst, condense and reflux at 80-85°C for 1-2 hours, then add 3-2-bromoethylindole solution under a protective gas atmosphere, continue condensing and reflux for 20-30 hours to obtain the bisindole crown ether; (2) Dissolve the bisindolyl crown ether and add sodium hydride, stir in an ice bath for 1-2 hours, then add bromoethoxy tert-butyldimethylsilane solution, stir and react at 80-100°C for 3-5 hours to obtain bisindolyl crown ether ethoxy tert-butyldimethylsilane; (3) Dissolve bisindole crown ether ethoxy tert-butyldimethylsilane and perform desilylation reaction to obtain bisindole crown ether diol.

5. The preparation method according to claim 4, characterized in that In step (1), the crown ether is an aza crown ether, and the mass ratio of the aza crown ether to 3-2-bromoethylindole is 0.5-1:0.8-2.

6. The preparation method according to claim 4, characterized in that The catalyst is at least one of sodium carbonate and sodium iodide.

7. The preparation method according to claim 4, characterized in that In step (2), the mass ratio of bisindole crown ether to bromoethoxy tert-butyldimethylsilane is 1-1.5:1.2-2.

0.

8. The preparation method according to claim 4, characterized in that In step (3), tetrabutylammonium fluoride with a concentration of 1 to 1.5 mol / L is used to remove the silyl group in bisindole crown ether ethoxy tert-butyldimethylsilane.

9. A high-performance bisindole crown ether-based polyurethane, characterized in that: The method according to any one of claims 1 to 8 is used to prepare the product.

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