A method for preparing a dispersity controllable polymer by a supramolecular induced switchable chain transfer agent

Abstract

The application relates to a method for preparing dispersion controllable polymers by supermolecule-induced switchable chain transfer reagents, and belongs to the technical field of controllable free radical polymerization. The stable host-guest complex formed by cucurbituril[7] and the switchable chain transfer reagent containing an N-containing heteroaromatic ring group promotes the positive movement of the movable acidity coefficient (pKa) of the switchable chain transfer reagent, so that the switchable chain transfer reagent is completely protonated under weak acid conditions, the solubility of the switchable chain transfer reagent in an aqueous solution is increased, the switchable chain transfer reagent is suitable for a water-phase biocompatible system, and the polymerization of a high-activity monomer can be controlled in a weak acid solution. Compared with traditional switchable chain transfer reagents, the supermolecule strategy for controlling the acidity coefficient of the switchable chain transfer reagent has great significance. The switchable chain transfer reagent can not only control the high-activity monomer under weak acid, but also can synthesize polymer materials with different dispersions by controlling the amount of cucurbituril[7], and can be widely applied to the fields of biological medicine, energy and industry.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of controllable radical polymerization, and particularly relates to a method for preparing polymers with controllable dispersity by using supermolecule-induced switchable chain transfer agent. BACKGROUND

[0002] Reversible addition-fragmentation chain transfer (RAFT) is widely used in the controllable synthesis of polymers, and has the advantages of controllable polymerization rate, controllable polymer molecular weight and molecular weight distribution, high fidelity of polymer chain end group, and wide range of monomers. However, the current method for controlling the dispersity of polymers requires complex experimental conditions and experimental devices, which limits its further application. Therefore, it is of great significance to synthesize polymers with controllable dispersity using a simple strategy and simple device to improve polymerization efficiency and reduce cost.

[0003] The monomers used in RAFT polymerization are divided into high activity monomers and low activity monomers according to the reaction properties, and most of the chain transfer agents are only suitable for the polymerization of one type of monomer. The switchable chain transfer agent can be switched in situ under acidic / basic conditions, and can well control the polymerization of high activity and low activity monomers. At present, the polymerization of high activity monomers is controlled by adding strong acid, and the deprotonation requires the addition of equal or excess amount of alkali to control the polymerization of low activity monomers. Moreover, most of the switchable chain transfer agents have poor water solubility, which limits their application in water-based biocompatible systems. Therefore, it is an urgent problem to develop a method for controlling the polymerization of monomers using switchable chain transfer agents under weak acid conditions, increasing the solubility of switchable chain transfer agents in water phase, and controlling the dispersity of polymers. SUMMARY

[0004] In order to solve the problems in the prior art, the present application provides a method for preparing polymers with controllable dispersity by using supermolecule-induced switchable chain transfer agent.

[0005] In the present application, cucurbituril [7] and switchable chain transfer agent containing heteroaromatic ring group form a stable host-guest complex, which promotes the positive shift of the mobile acidity coefficient (pKa) of the switchable chain transfer agent, so that the switchable chain transfer agent is completely protonated under weak acid conditions, the solubility of the switchable chain transfer agent in water solution is increased, and the switchable chain transfer agent is suitable for water-based biocompatible system. The polymerization of high activity monomers can be controlled in weak acid solution. By controlling the amount of cucurbituril [7], the protonation degree of the switchable chain transfer agent can be controlled, and polymers with different dispersity can be synthesized, which are expected to be applied in the fields of biological medicine, beauty, chemical industry, energy and the like.

[0006] The host-guest supramolecular formed by cucurbituril [7] and the switchable chain transfer agent containing heteroaromatic ring group under acid / base condition is protonated and deprotonated as shown below:

[0007]

[0008] In the present application, the heteroaromatic ring group of the switchable chain transfer agent is combined with cucurbituril [7] as a host to form a stable supramolecular host-guest complex, and the negative cavity of cucurbituril [7] can stabilize the protonated N-containing heteroaromatic ring group, so that the pKa of the switchable chain transfer agent is positively shifted, and the degree of protonation of the switchable chain transfer agent can be controlled under weak acid conditions by changing the amount of cucurbituril [7], so as to synthesize polymers with controllable dispersity by using supramolecular switchable chain transfer agents. Generally speaking, high activity monomers are more likely to react with free radicals to obtain more stable free radicals.

[0009] The present application discloses a method for preparing polymers with controllable dispersity by supramolecular-induced switchable chain transfer agent, which comprises the following steps: adding cucurbituril [7] and switchable chain transfer agent in a molar ratio of 1-50:1 into a reaction container, then adding high activity monomers in a molar ratio of 200-2500:1 to the switchable chain transfer agent, adding a thermal initiator in a molar ratio of 0.01-1.5:1 to the switchable chain transfer agent, and finally adding a weak acid buffer solution (pH 3.0-5.5) with a concentration not higher than 200 mM in a molar ratio of 10-500:1 to the switchable chain transfer agent, deoxygenating the reaction container under argon for 20-60 min, and then placing the reaction container in a water bath at 25-45°C for 2-24 hours, opening the reaction container to expose the reaction solution to air to quench the reaction, thereby obtaining polymers with controllable dispersity.

[0010] The high activity monomer is N,N-dimethyl acrylamide, 4-acryloylmorpholine, poly(ethylene glycol) methyl ether acrylate, poly(ethylene glycol) methacrylate, etc.

[0011] The thermal initiator is azobisdimethylimidazoline hydrochloride, 2,2'-azobis(2-methylpropionamidine) dihydrochloride, etc.

[0012] The weak acid buffer solution is acetic acid buffer solution, phthalate-hydrochloric acid buffer solution, disodium hydrogen phosphate-citric acid buffer solution, etc.

[0013] The structure of the switchable chain transfer agent containing heteroaromatic ring group capable of being combined with cucurbituril [7] is shown below:

[0014]

[0015] X is N, P, O, S atom;

[0016] R1 is C1-C8 alkyl, C6-C30 aryl, C5-C24 heteroaryl (heteroatom in heteroaryl is at least one of N, O, S);

[0017] R2 is C1-C12 cyano, C1-C12 alkyl, C1-C12 ester or C6-C30 aryl;

[0018] R3 is N, P, O, S-containing heteroaryl capable of forming conjugated structure with N, P, O, S atom in the above structural formula.

[0019] Further, the specific structure of the switchable chain transfer agent capable of binding with cucurbituril [7] and containing heteroaromatic ring group according to the present application is shown as follows:

[0020]

[0021] The preparation method of the switchable chain transfer agent capable of binding with cucurbituril [7] according to the present application has the following steps: a) preparation of the switchable chain transfer agent:

[0022] N-methylpyridin-4-amine (MPA), N-methylisoquinolin-4-amine (MQA), N-phenylpyridin-4-amine (PPA) or N-(4-methoxyphenyl)pyridin-4-amine (MOPA) is dissolved in anhydrous tetrahydrofuran, stirred and dissolved in a cold bath at -20°C; then under argon protection, n-butyllithium is added dropwise in a molar ratio of 1:0.9-1.2 to the above raw material, stirred and mixed, then carbon disulfide is added dropwise in a molar ratio of 1:1-3 to the above raw material, and the mixture is restored to room temperature; then 2-bromopropionate is added dropwise in a molar ratio of 1:0.9-1.2 to the above raw material, and stirred in the dark for 6-24 hours, then the reaction solution is quenched with saturated ammonium chloride solution, the organic phase is washed with water, then extracted with dichloromethane, the obtained organic phase is distilled under reduced pressure, purified by chromatography column, and dried in vacuum for 6-24 hours to obtain the switchable chain transfer agent.

[0023] The 2-bromopropionate is 2-bromopropionic acid methyl ester, 2-bromopropionic acid ethyl ester, 2-bromopropionic acid 2-methoxyethyl ester, etc.

[0024] Cucurbituril [7] and the switchable chain transfer agent are mixed in a molar ratio of 0-25:1, strong acid and strong base are added to adjust the acidity and alkalinity of the solution to ensure that the switchable chain transfer agent can be completely protonated and deprotonated, and under constant temperature, the absorbance and pH are determined by ultraviolet-visible spectrometer and pH meter to draw the pH-absorbance curve, and the acidity coefficient pKa value is fitted.

[0025] c) preparation of the switchable chain transfer agent with changed acidity coefficient:

[0026] Cucurbita urea [7] and a switchable chain transfer reagent were dissolved in water at a molar ratio of 1 to 25:1 and sonicated until completely dissolved to obtain an aqueous solution of the switchable chain transfer reagent with a shiftable acidity coefficient.

[0027] Compared with the prior art, the present invention has significant advantages:

[0028] First, the method of moving the pKa of a switchable chain transfer reagent through supramolecular interaction is proposed for the first time in this invention. This system is innovative, simple to operate, effective, and mild. The supramolecular host cucurbituril [7] forms a host-guest supramolecular relationship with the switchable chain transfer reagent, which promotes the solubility of the switchable chain transfer reagent in the aqueous phase and allows it to be fully protonated under weak acid conditions, making it suitable for biocompatible systems. Compared with traditional switchable chain transfer reagents, the use of supramolecular strategies to control the change in the acidity coefficient of switchable chain transfer reagents is of great significance. It can not only control highly active monomers under weak acid conditions, but also synthesize polymer materials with different dispersities by controlling the amount of cucurbituril [7], which can be widely used in biomedicine, energy and industry. Attached Figure Description

[0029] Figure 1 The NMR spectrum of MMPCP, the product of Example 1 of this invention;

[0030] Figure 2 The NMR spectrum of MQCP, the product of Example 1 of this invention;

[0031] Figure 3 The NMR spectrum of MOCP, the product of Example 1 of this invention;

[0032] Figure 4 The NMR spectrum of PPCP, the product of Example 1 of this invention;

[0033] Figure 5 MPCP-H, the product of Example 1 of this invention. + pH-absorbance test curve;

[0034] Figure 6 The product CMPC-H in Example 2 of this invention + pH-absorbance test curve;

[0035] Figure 7 MMPCP-H, the product of Example 2 of this invention. + pH-absorbance test curve;

[0036] Figure 8 The product MQCP-H in Example 2 of this invention + pH-absorbance test curve;

[0037] Figure 9 MOCP-H, the product of Example 2 of this invention. + pH-absorbance test curve;

[0038] Figure 10 The product PPCP-H in Example 2 of this invention + pH-absorbance test curve;

[0039] Figure 11 PNAM is the product of Example 4 of this invention. 1000 GPC diagram.

[0040] Figure 12 PDMA, the product of Example 4 of this invention. 2500 GPC diagram. Detailed Implementation

[0041] The following specific embodiments will further illustrate the above scheme, and the substrate structure used is as follows:

[0042]

[0043] Example 1:

[0044] a) Synthesis of switchable chain transfer reagent MMPCP

[0045] In this embodiment, the product characterization results are shown in [reference needed]. Figure 1 This indicates that the product with the target structure was obtained. MPA (0.11 g, 1.0 mmol) was dissolved in anhydrous tetrahydrofuran (15 mL) and stirred in a -20°C cold bath. Under argon protection, a solution of n-butyllithium in n-hexane (0.08 g, 1.2 mmol dissolved in n-hexane, concentration 1.6 M) was added dropwise. After stirring and mixing, carbon disulfide (0.23 g, 3.0 mmol) was added dropwise. The mixture was then brought to room temperature, and PEG-Br (0.5 g, 1.2 mmol) was added dropwise with stirring. The reaction solution was quenched with saturated ammonium chloride solution, and the organic phase was washed with water and extracted with dichloromethane. The product was subjected to vacuum distillation, and the resulting solid was purified by column chromatography (dichloromethane:methanol = 9:1, v / v) to finally obtain 0.27 g of a pale yellow oily substance, MMPCP, with a yield of 45%. The structural formula is as follows:

[0046]

[0047] b) Synthesis of switchable chain transfer reagent MQCP

[0048] In this embodiment, the product characterization results are shown below. Figure 2MQCP, yield 59%, as a dark brown oil, and its structure is as follows:

[0049]

[0050] a) Synthesis of switchable chain transfer agent MOCP

[0051] In this example, the product characterization results are shown in Table 1 below: Figure 3 , indicating that the product of the target structure was obtained. MOPA (0.2 g, 1.0 mmol) was dissolved in anhydrous tetrahydrofuran (10 mL), which was placed in a cold bath at -20 °C to stir and dissolve, and under the protection of argon, n-butyllithium solution in n-hexane (0.08 g, 1.2 mmol dissolved in n-hexane, concentration 1.6 M) was added dropwise, after stirring and mixing, carbon disulfide (0.23 g, 3.0 mmol) was added dropwise, and the mixture was restored to room temperature, then 2-bromopropionic acid methyl ester (0.2 g, 1.2 mmol) was added dropwise and stirred for 24 hours, after the reaction, the solution was quenched with saturated ammonium chloride solution, and then the organic phase was washed with water and extracted with dichloromethane, the product was distilled under reduced pressure, and the obtained solid was purified by column chromatography (dichloromethane:methanol = 9:1, v / v) to finally obtain 0.24 g of brown oil MOCP, yield 73%, and its structure is as follows:

[0052]

[0053] a) Synthesis of switchable chain transfer agent PPCP

[0054] In this example, the product characterization results are shown in Table 1 below: Figure 4, indicating that the product of the target structure was obtained. PPA (0.17 g, 1.0 mmol) was dissolved in anhydrous tetrahydrofuran (10 mL), which was placed in a cold bath at -20 °C to stir and dissolve, and a solution of n-butyllithium in n-hexane (0.08 g, 1.2 mmol dissolved in n-hexane, concentration 1.6 M) was added dropwise under the protection of argon. After stirring the mixture, carbon disulfide (0.23 g, 3.0 mmol) was added dropwise, and the mixture was restored to room temperature. Then, 2-bromopropionic acid methyl ester (0.2 g, 1.2 mmol) was added dropwise and stirred for 24 hours. After the reaction, the solution was quenched with a saturated ammonium chloride solution, and the organic phase was washed with water and then extracted with dichloromethane. The product was distilled under reduced pressure, and the obtained solid was purified by column chromatography (dichloromethane:methanol = 9:1, v / v) to finally obtain 0.29 g of PPCP as a light yellow solid with a yield of 80%, and the structural formula is as follows:

[0055]

[0056] Example 2:

[0057] a) Cucurbit[7]uril induces pKa shift of MPCP-H +

[0058] Cucurbit[7]uril and MPCP were prepared into stock solutions in a ratio of (0, 1, 5, 12.5, 25):1, respectively. The pH of the solution was adjusted by hydrochloric acid or sodium hydroxide, and the temperature was always maintained under the same conditions. The absorbance and pH were determined by ultraviolet-visible spectrometer and pH meter to draw the pH-absorbance curve.

[0059] Experimental test analysis:

[0060] In this example, the method was tested at 25 °C. The spectral changes of MPCP in different pH environments were tested by ultraviolet-visible spectrometer, and the pKa values of MPCP-H + in the presence of different ratios of cucurbit[7]uril were fitted. The pKa value of MPCP-H + without cucurbit[7]uril was 3.57, the pKa value with 1 equivalent of cucurbit[7]uril was 4.73, the pKa value with 5 equivalents of cucurbit[7]uril was 5.20, the pKa value with 12.5 equivalents of cucurbit[7]uril was 5.62, and the pKa value with 25 equivalents of cucurbit[7]uril was 5.64. The pKa value of MPCP-H + was positively shifted after the addition of cucurbit[7]uril. Under the same polymerization conditions, the protonation degree of the convertible chain transfer reagent could be adjusted by the ratio of cucurbit[7]uril added, as shown in Figure 5 .

[0061] b) Cucurbit[7]uril induces pKa shift of CMPC-H +

[0062] Cucurbit[7] and CMPC were prepared into stock solutions with the ratio of (0, 1, 5, 12.5):1, the pH of the solution was adjusted by hydrochloric acid or sodium hydroxide, the temperature was always maintained under the same conditions, the absorbance and pH were determined by ultraviolet-visible spectrometer and pH meter to draw the pH-absorbance curve.

[0063] Experimental test analysis:

[0064] For the test of this embodiment method, the spectral changes of CMPC in different pH environments can be tested by ultraviolet-visible spectrometer under the condition of 25℃, and the pKa values of CMPC-H + in the presence of cucurbit[7] in different proportions are fitted to obtain. The pKa value without the addition of cucurbit[7] is 3.45, the pKa value with the addition of 1 equivalent of cucurbit[7] is 4.67; the pKa value with the addition of 5 equivalents of cucurbit[7] is 5.34; and the pKa value with the addition of 12.5 equivalents of cucurbit[7] is 5.89. The pKa value of CMPC-H + can be positively moved after the addition of cucurbit[7], and under the same polymerization conditions, the protonation degree of the convertible chain transfer reagent can be regulated by the proportion of the addition of cucurbit[7], see Figure 6 .

[0065] c) Test of pKa shift of MMPCP-H + induced by cucurbit[7]

[0066] Cucurbit[7] and MMPCP were prepared into stock solutions with the ratio of (0, 1, 5, 12.5):1, the pH of the solution was adjusted by hydrochloric acid or sodium hydroxide, the temperature was always maintained under the same conditions, the absorbance and pH were determined by ultraviolet-visible spectrometer and pH meter to draw the pH-absorbance curve.

[0067] Experimental test analysis:

[0068] For the test of this embodiment method, the spectral changes of MMPCP in different pH environments can be tested by ultraviolet-visible spectrometer under the condition of 25℃, and the pKa values of MMPCP-H + in the presence of cucurbit[7] in different proportions are fitted to obtain. The pKa value without the addition of cucurbit[7] is 3.34, the pKa value with the addition of 1 equivalent of cucurbit[7] is 3.96; the pKa value with the addition of 5 equivalents of cucurbit[7] is 4.60; and the pKa value with the addition of 12.5 equivalents of cucurbit[7] is 5.44. The pKa value of MMPCP-H + can be positively moved after the addition of cucurbit[7], and under the same polymerization conditions, the protonation degree of the convertible chain transfer reagent can be regulated by the proportion of the addition of cucurbit[7], seeFigure 7 .

[0069] d) Cucurbit[7]uril induced pKa shift of MQCP-H +

[0070] Cucurbit[7]uril and MQCP were prepared into stock solutions with the ratio of (0, 1, 5, 12.5, 25):1, the pH of the solution was adjusted by hydrochloric acid or sodium hydroxide, the temperature was always maintained under the same conditions, the absorbance and pH were determined by UV-visible spectrometer and pH meter to draw the pH-absorbance curve.

[0071] Experimental test analysis:

[0072] For this embodiment method test, at 25°C, the spectral changes of MQCP in different pH environments can be tested by UV-visible spectrometer, and the pKa values of MQCP-H + with different ratios of cucurbit[7]uril are fitted. The pKa value without cucurbit[7]uril is 4.47, the pKa value with 1 equivalent of cucurbit[7]uril is 4.80; the pKa value with 5 equivalents of cucurbit[7]uril is 5.05; the pKa value with 12.5 equivalents of cucurbit[7]uril is 5.50; the pKa value with 25 equivalents of cucurbit[7]uril is 6.00. After adding cucurbit[7]uril, the pKa value of MQCP-H + can be positively shifted. Under the same polymerization conditions, the protonation degree of the transformable chain transfer agent can be adjusted by adding the ratio of cucurbit[7]uril, see Figure 8 .

[0073] e) Cucurbit[7]uril induced pKa shift of MOCP-H +

[0074] Cucurbit[7]uril and MOCP were prepared into stock solutions with the ratio of (0, 12.5):1, the pH of the solution was adjusted by hydrochloric acid or sodium hydroxide, the temperature was always maintained under the same conditions, the absorbance and pH were determined by UV-visible spectrometer and pH meter to draw the pH-absorbance curve.

[0075] Experimental test analysis:

[0076] For this embodiment method test, at 25°C, the spectral changes of PPCP in different pH environments can be tested by UV-visible spectrometer, and the pKa values of PPCP-H + with different ratios of cucurbit[7]uril are fitted. The pKa value without cucurbit[7]uril is 4.11, the pKa value with 12.5 equivalents of cucurbit[7]uril is 4.40; after adding cucurbit[7]uril, the pKa value of PPCP-H + ​​The pKa of PPCP-H can be shifted positively, and the degree of protonation of the transformable chain transfer reagent can be regulated by adding cucurbituril [7] under the same conditions, see Figure 9 .

[0077] f) Cucurbituril [7] induces PPCP-H + pKa shift test

[0078] Cucurbituril [7] and PPCP were prepared into stock solutions in a ratio of (0, 12.5):1, and the pH of the solution was adjusted by hydrochloric acid or sodium hydroxide. The temperature was always maintained under the same conditions. The absorbance and pH were determined by ultraviolet-visible spectrometer and pH meter to draw the pH-absorbance curve.

[0079] Experimental test analysis:

[0080] For the method tested in this example, the spectral changes of PPCP in different pH environments were tested by ultraviolet-visible spectrometer at 25°C. The pKa values of PPCP-H + were obtained by fitting. The pKa value without adding cucurbituril [7] was 4.11, and the pKa value with adding 12.5 equivalents of cucurbituril [7] was 4.40. The pKa of PPCP-H + can be shifted positively after adding cucurbituril [7], and the degree of protonation of the transformable chain transfer reagent can be regulated by adding cucurbituril [7] under the same conditions, see Figure 10 .

[0081] Example 3:

[0082] Preparation of switchable chain transfer reagent with pKa change:

[0083] a) MPCP (1.1 mg, 4 μmol) and cucurbituril [7] (58 mg, 50 μmol) were weighed and dissolved in 100 mL aqueous solution, and ultrasonic was performed until complete dissolution to obtain the aqueous solution of the acidity coefficient shifted transformable chain transfer reagent MQCP; the pKa value was 5.62.

[0084] b) CMPC (1.0 mg, 4 μmol) and cucurbituril [7] (58 mg, 50 μmol) were weighed and dissolved in 100 mL aqueous solution, and ultrasonic was performed until complete dissolution to obtain the aqueous solution of the acidity coefficient shifted transformable chain transfer reagent MQCP; the pKa value was 5.89.

[0085] c) MMPCP (2.4 mg, 4 μmol) and cucurbituril [7] (58 mg, 50 μmol) were weighed and dissolved in 100 mL aqueous solution, and ultrasonic was performed until complete dissolution to obtain the aqueous solution of the acidity coefficient shifted transformable chain transfer reagent MQCP; the pKa value was 5.44.

[0086] d) Weighing MPCP (1.3 mg, 4 μmol) and cucurbituril [7] (58 mg, 50 μmol) into 100 mL aqueous solution, ultrasonic to completely dissolved, to get the aqueous solution of the translatable chain transfer reagent MPCP with the acidity coefficient shift; pKa value is 5.50.

[0087] e) Weighing MOCP (1.4 mg, 4 μmol) and cucurbituril [7] (58 mg, 50 μmol) into 100 mL aqueous solution, ultrasonic to completely dissolved, to get the aqueous solution of the translatable chain transfer reagent PPCP with the acidity coefficient shift; pKa value is 4.23.

[0088] f) Weighing PPCP (1.3 mg, 4 μmol) and cucurbituril [7] (58 mg, 50 μmol) into 100 mL aqueous solution, ultrasonic to completely dissolved, to get the aqueous solution of the translatable chain transfer reagent PPCP with the acidity coefficient shift; pKa value is 4.40.

[0089] Example 4:

[0090] a) Synthesis of poly N, N-dimethylacrylamide PNAM 1000 :

[0091] The translatable chain transfer reagent MPCP (0.19 mg, 0.71 μmol), 4-acryloylmorpholine NAM (0.1 g, 0.71 mmol), azobisisobutyrimidazoline hydrochloride (6.9 μg, 0.02 μmol) were added into a 4 mL dry glass bottle, then acetic acid buffer (50 mM, pH = 3.5, 2.84 mL, 142 μmol) was added, and another 4 mL dry glass bottle was added with the translatable chain transfer reagent MPCP (0.19 mg, 0.71 μmol) and cucurbituril [7] (2.33 mg, 4.2 μmol) solution, 4-acryloylmorpholine NAM (0.1 g, 0.71 mmol), azobisisobutyrimidazoline hydrochloride (0.04 mg, 0.12 μmol), and acetic acid buffer (50 mM, pH = 3.5, 2.84 mL, 142 μmol) was added. After the two glass bottles were deoxygenated in argon for 30 min, they were placed in a 35 °C water bath for 8 hours, then opened to expose the reaction liquid to air to quench the reaction, to obtain a poly 4-acryloylmorpholine PNAM with controllable dispersity, see 1000 . Figure 11 .

[0092] Experimental test analysis:

[0093] The PNAM prepared by the method of this embodiment 1000Tests were conducted, and the integrated area of ​​the signal peak corresponding to the double bond hydrogen on the 4-acryloylmorpholine monomer by NMR analysis showed that the conversion rates without cucurbitacin[7] were 92% and 93%, respectively. Gel permeation chromatography (GPC) tests showed that PNAM without cucurbitacin[7] had a higher conversion rate. 1000 It is M n，GPC =150.1 kg / mol PNAM with added cucurbitacin[7] 1000 It is M n，GPC =148.2 kg / mol See Figure 11 The dispersity changed from 1.52 to 1.25, indicating that polymers with controllable dispersity can be prepared by using supramolecular-induced switchable chain transfer reagents.

[0094] b) Synthesis of poly(N,N-dimethylacrylamide) PDMA 2500 :

[0095] Add the convertible chain transfer agent MPCP (0.11 mg, 0.4 μmol) and N,N-dimethylacrylamide DMA (0.1 g, 1.0 mmol), azobisisobutyrazoline hydrochloride (0.04 mg, 0.12 μmol) to a 4 mL dry glass bottle, then add acetate buffer (50 mM, pH = 3.5, 1.6 mL, 80 μmol); then take another 4 mL dry glass bottle and add the convertible chain transfer agent MPCP (0.11 mg, 0.4 μmol) and cucurbitaureus [7] (2.33 mg, 2 μmol), N,N-dimethylacrylamide (0.1 g, 1.0 mmol), azobisisobutyrazoline hydrochloride (0.04 mg, 0.12 μmol), then add acetate buffer (50 mM, pH = 3.5, 1.6 mL, 80 μmol). After deoxygenating two glass bottles in argon atmosphere for 30 minutes, they were placed in a 35°C water bath for 7 hours. The mixture was then opened to expose the reaction solution to air, thus quenching the reaction and yielding a set of poly(N,N-dimethylacrylamide) (PDMA) with controllable dispersibility. 2500 See Figure 12 .

[0096] Experimental test analysis:

[0097] PDMA prepared by the method of this embodiment 2500 Tests were conducted, and the integrated area of ​​the signal peak corresponding to the double bond hydrogen on the N,N-dimethylacrylamide monomer by nuclear magnetic resonance analysis showed that the conversion rates without cucurbitacrylamide [7] were 72% and 70%, respectively. Gel permeation chromatography (GPC) tests showed that PDMA without cucurbitacrylamide [7] had a higher conversion rate. 2500 It is M n，GPC =176.7 kg / mol PDMA added with 2 μmol cucurbituril [7] 2500 is M n，GPC = 153.0 kg / mol, See Figure 12 The dispersity changed from 1.39 to 1.23, which indicated that the dispersity controllable polymers could be prepared by the switchable chain transfer agent induced by supramolecule.

Claims

1. A method for preparing a dispersity-controllable polymer by a supramolecular-induced switchable chain transfer agent, characterized in that: is to add capping agent of molar ratio 1-50:1 to the reaction vessel, then add high activity monomer of molar ratio 200-2500:1 to the above capping agent, add thermal initiator of molar ratio 0.01-1.5:1 to the above capping agent, finally add weak acid buffer solution of molar ratio 10-500:1 to the above capping agent, wherein the concentration of the weak acid buffer solution is not higher than 200 mM, and the pH is 3.0-5.5, and then the above reaction vessel is deoxygenated under argon for 20 min-60 min, and then placed in a water bath at 25-45 DEG C for 2-24 hours, and then opened to expose the reaction liquid to air to quench the reaction, thereby obtaining the polymer with controllable dispersity; wherein the capping agent with heteroaromatic ring group has one of the following structural formulae, 。 2. A method of preparing a controlled-dispersity polymer by supramolecular induced switchable chain transfer agent as claimed in claim 1, wherein: The high activity monomer is N,N-dimethyl acrylamide, 4-acryloylmorpholine, poly(ethylene glycol) methyl ether acrylate or poly(ethylene glycol) methacrylate.

3. The method for preparing a polymer with controllable dispersibility using a supramolecular-induced switchable chain transfer reagent as described in claim 1, characterized in that: The thermal initiator is azobisdimethylimidazoline hydrochloride or 2,2'-azobis(2-methylpropionamidine) dihydrochloride.

4. The method for preparing a polymer with controllable dispersibility using a supramolecular-induced switchable chain transfer reagent as described in claim 1, characterized in that: The weak acid buffer solution is acetic acid buffer solution, phthalate-hydrochloric acid buffer solution or disodium hydrogen phosphate-citric acid buffer solution.

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