Water-soluble alkoxylamine initiators, methods for their synthesis and use

Abstract

The application discloses a water-soluble alkoxy amine initiator and a synthesis method and application thereof, and belongs to the technical field of polymer chemistry, wherein the water-soluble alkoxy amine initiator provided by the application comprises a pyridinium benzyl structure and a quinoline aromatic structure, which not only endows the molecule with good water solubility, but also provides a binding site for the formation of a host-guest complex with cucurbituril; through the molecule and the cucurbituril supramolecular complex, a new monomolecular initiation system suitable for water-phase NMP polymerization can be constructed, and the types of existing water-phase NMP alkoxy amine initiators are enriched. The water-soluble alkoxy amine initiator can initiate the polymerization of sodium 4-vinylbenzenesulfonate in water phase; the molecular weight of the obtained polymer increases with the increase of the monomer conversion rate, and the molecular weight distribution is relatively narrow, which indicates that the system has controllable / active polymerization characteristics.

Description

Technical Field

[0001] This invention relates to the field of polymer chemistry, specifically to a water-soluble alkoxyamine initiator, its synthesis method, and its application. Background Technology

[0002] Nitroxide-mediated polymerization (NMP) is an important method in reversible deactivated radical polymerization. Compared with atom transfer radical polymerization (ATRP) and reversible addition-fragmentation chain transfer polymerization (RAFT), NMP typically does not require transition metal catalysts or sulfur-containing chain transfer reagents, has a simpler system composition, yields higher polymer purity, and requires relatively simple post-processing. It has application value in the preparation of functional polymers and water-soluble polymers.

[0003] The NMP system mainly includes bimolecular initiation systems and monomolecular initiation systems. Bimolecular initiation systems typically consist of a common radical initiator and a nitroxide radical regulator. The initiator decomposes upon heating to generate free radicals, which then initiate monomer polymerization. The nitroxide radicals regulate the polymerization process by capturing growing free radicals to form dormant species. While this system is simple to operate, the free radical generation process is difficult to control precisely, easily leading to insufficient polymerization reproducibility and end-group structure control.

[0004] Unimolecular initiation systems typically use alkoxyamines as initiators. Alkoxyamine molecules contain thermally cleavable C–ON bonds, and their structure consists of a carbon-center radical precursor segment and a nitroxide radical regulating segment. Under heating conditions, the C–ON bonds undergo reversible homolytic cleavage, generating a carbon-center radical for initiating polymerization and a nitroxide radical for regulating polymerization in equal proportions. The carbon-center radical initiates monomer polymerization to form a growing radical, which can then be captured by the nitroxide radical to form a dormant species. Through this reversible cleavage-recombination equilibrium between active and dormant species, the concentration of active radicals in the system is maintained at a low level, thereby reducing bimolecular termination reactions and achieving control over the polymer's molecular weight and molecular weight distribution.

[0005] Aqueous-phase NMP is an important development direction in NMP technology. It typically involves dissolving water-soluble monomers and water-soluble alkoxyamine initiators in water, followed by heating and polymerization after deoxygenation. Compared to organic solvent systems, aqueous-phase polymerization offers advantages such as being environmentally friendly, safe, low-cost, easily adjustable in viscosity, and simple post-processing of the product. It is suitable for preparing water-soluble polymers such as sodium 4-vinylbenzenesulfonate, polyacrylamide, and polyN,N-dimethylacrylamide.

[0006] However, existing aqueous NMP technology has the following main shortcomings.

[0007] First, there are relatively few water-soluble alkoxyamine initiators suitable for aqueous NMP. Traditional alkoxyamines are mostly used in organic phase polymerization, but their water solubility is insufficient, making them difficult to use directly in homogeneous aqueous systems. Although some water-soluble alkoxyamines have been reported, their structural types are limited, and their synthesis and application scope still cannot meet the needs of the development of aqueous NMP systems.

[0008] Second, there is still room for improvement in the polymerization efficiency of existing water-soluble alkoxyamine initiators. Some systems exhibit long polymerization induction periods and low polymerization rates in the aqueous phase, limiting monomer conversion and the achievable polymer molecular weight. Therefore, it is necessary to develop new initiator structures to improve aqueous NMP efficiency and obtain water-soluble polymers with higher molecular weights.

[0009] Third, existing methods for regulating the activity of alkoxyamines typically rely on complex covalent structural modifications. For example, C–ON bond cleavage behavior can be modulated by altering the nitroxide radical skeleton, introducing sterically hindered groups, acid-base responsive groups, or metal coordinating groups. These methods often require the redesign and synthesis of complex molecules, involve numerous steps, and lack versatility and modularity.

[0010] Fourth, existing aqueous NMP initiation systems rarely consider both "novel water-soluble alkoxyamine initiator design" and "mainstream macrocyclic supramolecular complex regulation." In other words, current technologies focus more on the initiator itself or the optimization of polymerization conditions, but lack an initiation system that can serve as a single-molecule initiator for aqueous NMP while simultaneously forming a stable complex with cucurbituril to further improve polymerization efficiency.

[0011] In summary, the development of existing aqueous monomolecular NMP systems relies on high-performance water-soluble alkoxyamine initiators. On one hand, the initiator needs good water solubility to participate in polymerization in a homogeneous aqueous solution; on the other hand, the C–ON bond of the initiator needs suitable thermal decomposition activity to effectively generate initiating radicals and nitroxide radicals in the aqueous phase and at relatively mild temperatures. Furthermore, the nitroxide radicals generated after initiator decomposition need to be able to effectively regulate the growth of the radicals, ensuring a controllable / active polymerization process. Therefore, designing novel water-soluble alkoxyamine initiators is a crucial foundation for the development of aqueous NMP polymerization. Summary of the Invention

[0012] The purpose of this invention is to provide a water-soluble alkoxyamine initiator, its synthesis method, and its application, in order to solve the problems mentioned in the background art.

[0013] To achieve the above objectives, the present invention provides the following technical solution:

[0014] Water-soluble alkoxyamine initiators (PQNs) include pyridinium benzyl and quinoline aromatic structures, with the following structural formulas:

[0015] .

[0016] Another object of the present invention is to provide a method for synthesizing the above-mentioned water-soluble alkoxyamine initiator, comprising the following steps:

[0017] Isobutyraldehyde is reacted with 2-methyl-2-nitropropane to produce N-tert-butyl-α-isopropylnitrone;

[0018] N-tert-butyl-α-isopropylnitrone was reacted with 3-bromopyridine via a Grignard reaction to give a pyridine-substituted hydroxylamine intermediate;

[0019] The hydroxylamine intermediate was substituted with pyridine and introduced into a benzylpyridinium structure via a benzyl quaternization reaction to obtain the hydroxylamine precursor;

[0020] The hydroxylamine precursor was oxidized to obtain water-soluble nitric oxide free radicals;

[0021] A water-soluble nitric oxide radical was reacted with 2-bromomethylquinoline to obtain a water-soluble alkoxyamine initiator.

[0022] Furthermore, isobutyraldehyde reacts with 2-methyl-2-nitropropane in the presence of ammonium chloride and zinc powder.

[0023] Furthermore, water-soluble nitric oxide radicals react with 2-bromomethylquinoline in the presence of copper powder and 2,2'-bipyridine.

[0024] Another object of the present invention is to provide a supramolecular complex comprising the above-described water-soluble alkoxyamine initiator and cucurbituril.

[0025] Furthermore, the cucurbituril is cucurbituril[8] (CB[8]).

[0026] Furthermore, the molar ratio of the water-soluble alkoxyamine initiator to cucurbituril is 1:(0.8–1.2).

[0027] Another object of the present invention is to provide the application of the above-mentioned water-soluble alkoxyamine initiator or the above-mentioned supramolecular complex in aqueous nitrogen-oxygen stable free radical polymerization.

[0028] Furthermore, the method for aqueous nitrogen-oxygen stabilized free radical polymerization is as follows: the water-soluble alkoxyamine initiator or supramolecular complex is mixed with the water-soluble vinyl monomer in water, and after deoxygenation treatment, the mixture is heated to the polymerization initiation temperature to carry out the polymerization reaction.

[0029] Furthermore, the water-soluble vinyl monomer includes sodium 4-vinylbenzenesulfonate; the molar ratio of the water-soluble vinyl monomer to the water-soluble alkoxyamine initiator or supramolecular complex is (3000–4000):1; and the polymerization reaction temperature is 80–100°C.

[0030] The water-soluble alkoxyamine initiator provided by this invention comprises a pyridinium benzyl structure and a quinoline aromatic structure, which not only endows the molecule with good water solubility but also provides binding sites for forming host-guest complexes with cucurbituril. Through this molecule and its cucurbituril supramolecular complex, a novel monomolecular initiation system suitable for aqueous NMP polymerization can be constructed, enriching the existing variety of aqueous NMP alkoxyamine initiators. This water-soluble alkoxyamine initiator can initiate the polymerization of sodium 4-vinylbenzenesulfonate in the aqueous phase. The resulting polymer's molecular weight increases with increasing monomer conversion rate, and its molecular weight distribution is relatively narrow, indicating that the system exhibits controlled / living polymerization characteristics.

[0031] The water-soluble alkoxyamine initiator provided by this invention, after forming a supramolecular complex with cucurbituril, can significantly shorten the polymerization induction period. Compared with free water-soluble alkoxyamine initiators, this supramolecular complex initiation system can produce significant monomer conversion in a shorter time and exhibits a faster polymerization growth rate. While increasing the polymerization rate, the supramolecular complex system provided by this invention also ensures that the experimental molecular weight of the resulting polymer remains essentially consistent with the theoretical molecular weight, and the molecular weight distribution remains within a controllable range, indicating that the addition of cucurbituril does not disrupt the basic regulatory characteristics of NMP.

[0032] This invention does not rely on complex covalent structure modification, but improves the efficiency of the initiation system by combining a water-soluble alkoxyamine initiator with a host-guest compound of cucurbituril. It has advantages such as simple operation, high modularity, and suitability for aqueous systems. Attached Figure Description

[0033] Figure 1 The synthetic route and molecular structure of PQN are shown.

[0034] Figure 2 The image shows the HH COSY spectrum of PQN (25℃, deuterated water); in the image, A is the full HH COSY spectrum; B is the related signal in the aromatic region; and C is the related signal in the fatty region.

[0035] Figure 3 For the combination of PQN and CB[8] 1 H NMR spectrum (25℃, deuterium water).

[0036] Figure 4 The ITC spectrum of 0.8 mM PQN added to 0.08 mM CB[8] (25 °C, water).

[0037] Figure 5 Characterization diagrams of aqueous NMP polymerization of sodium 4-vinylbenzenesulfonate initiated by PQN and CB[8]-PQN; In the figure, A is the monomer conversion-time curve of aqueous NMP polymerization of sodium 4-vinylbenzenesulfonate (SS) initiated by free PQN and CB[8]-PQN complex respectively, and the inset is the corresponding first-order kinetic fitting curve; B is the curve of the number-average molecular weight and molecular weight distribution of the obtained polymer in the CB[8]-PQN initiation system as a function of monomer conversion; C is the curve of the number-average molecular weight and molecular weight distribution of the obtained polymer in the free PQN initiation system as a function of monomer conversion.

[0038] Figure 6 The effect of different functional groups on the practicality of initiators.

[0039] Figure 7 The figure shows the comparison of the effects of CB[8] and CB[7] on monomer conversion rate.

[0040] Figure 8 The figure shows the comparison of the effects of CB[8] and CB[7] on polymerization efficiency. Detailed Implementation

[0041] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0042] This invention addresses the problems of limited types of water-soluble alkoxyamine initiators, long polymerization induction periods, low polymerization rates, and difficulty in efficiently preparing high molecular weight water-soluble polymers in existing aqueous nitrogen-oxygen stable radical polymerization (NMP). A new TIPNO-type water-soluble alkoxyamine initiator, denoted as PQN, was designed and synthesized.

[0043] Specifically, in one embodiment of the present invention, a water-soluble alkoxyamine initiator PQN is provided, comprising a pyridinium benzyl structure and a quinoline aromatic structure, the structural formula of which is as follows:

[0044] .

[0045] Among them, the pyridinium salt structure endows PQN with good water solubility, and at the same time provides a cation recognition site for it to form a host-guest complex with cucurbit[8]urea (CB[8]); the quinoline structure, as an aromatic end group, can participate in inclusion with the pyridinium recognition end in the cavity of CB[8], thereby forming a folded host-guest supramolecular complex.

[0046] In this embodiment of the invention, the water-soluble alkoxyamine initiator PQN can initiate NMP polymerization of water-soluble monomers such as sodium 4-vinylbenzenesulfonate in the aqueous phase, exhibiting controlled / living polymerization characteristics. Simultaneously, PQN molecules can form a stable 1:(0.8–1.2) molar ratio host-guest supramolecular complex (CB[8]-PQN) with cucurbita[8]. The introduction of CB[8] further improves the efficiency of PQN-initiated aqueous NMP polymerization. The CB[8]-PQN complex significantly shortens the polymerization induction period, increases the polymerization growth rate, and maintains controllable polymerization characteristics such as polymer molecular weight increasing with conversion rate and a narrow molecular weight distribution. Compared to PQN alone, the CB[8]-PQN complex significantly shortens the polymerization induction period, increases the polymerization rate, and maintains the controllability of polymer molecular weight and molecular weight distribution, possessing water solubility, controllable polymerization capability, and supramolecular regulation capability.

[0047] It should be noted that cucurbituril (CB[n]s) is a class of water-soluble macrocyclic host molecules with rigid hydrophobic cavities and carbonyl-rich port structures, enabling them to form stable host-guest complexes with cationic guests through hydrophobic interactions, ion-dipole interactions, and aromatic interactions. Therefore, introducing structural units that can recognize cucurbituril into water-soluble alkoxyamine molecules holds promise for constructing novel initiation systems that combine water solubility, NMP initiation capability, and supramolecular regulatory ability.

[0048] In another embodiment of the present invention, a method for synthesizing the above-mentioned water-soluble alkoxyamine initiator PQN is also provided, comprising the following steps:

[0049] S1. Isobutyraldehyde and 2-methyl-2-nitropropane are reacted in the presence of ammonium chloride and zinc powder to produce N-tert-butyl-α-isopropylnitrone.

[0050] S2. N-tert-butyl-α-isopropylnitrone was reacted with 3-bromopyridine via a Grignard reaction to obtain a pyridine-substituted hydroxylamine intermediate;

[0051] S3. Pyridine is substituted for hydroxylamine intermediates to introduce benzylpyridinium structure via benzyl bromide quaternization reaction to obtain hydroxylamine precursor;

[0052] S4. The hydroxylamine precursor is oxidized to obtain TIPNO-type water-soluble nitric oxide radical PTNO;

[0053] S5. The water-soluble nitroxide radical PTNO is reacted with 2-bromomethylquinoline in the presence of copper powder and 2,2'-bipyridine to obtain the water-soluble alkoxyamine initiator PQN.

[0054] In another embodiment of the present invention, the application of the above-mentioned water-soluble alkoxyamine initiator or the above-mentioned supramolecular complex (CB[8]-PQN complex) in aqueous nitrogen-oxygen stable free radical polymerization is also provided.

[0055] Specifically, the method for aqueous nitrogen-oxygen stabilized free radical polymerization is as follows: the above-mentioned water-soluble alkoxyamine initiator or CB[8]-PQN complex is mixed with water-soluble vinyl monomers in water, and after deoxygenation treatment, it is heated to the polymerization initiation temperature for polymerization reaction. Among them, the water-soluble vinyl monomers include sodium 4-vinylbenzenesulfonate; the molar ratio of water-soluble vinyl monomers to water-soluble alkoxyamine initiator or supramolecular complex is (3000–4000):1; the polymerization reaction temperature is 80–100℃. The CB[8]-PQN complex shortens the polymerization induction period, increases the polymerization rate, and at the same time maintains the controllable growth of polymer molecular weight and a narrow molecular weight distribution.

[0056] Unless otherwise specified, all raw materials used in the following embodiments are commercially available products and can be purchased through commercial channels. The invention will be described in detail below through specific embodiments in practical applications.

[0057] Example 1: This example provides a method for synthesizing the water-soluble alkoxyamine initiator PQN, as detailed below:

[0058] according to Figure 1The route shown is for the synthesis of the TIPNO-type water-soluble alkoxyamine initiator PQN: Isobutyraldehyde (4.32 g, 60 mmol), 2-methyl-2-nitropropane (6.18 g, 60 mmol), and ammonium chloride (3.54 g, 66 mmol) were added to a 250 mL round-bottom flask, dissolved in deionized water (90 mL) and diethyl ether (90 mL), cooled to 0 °C, and zinc granules (15.6 g, 240 mmol) were added in portions over 1 h. The mixture was then allowed to rise naturally to room temperature and stirred overnight. After the reaction was complete, the mixture was filtered, the filter cake was washed with methanol (3 × 30 mL), and the filtrate was extracted with dichloromethane (3 × 80 mL). The combined organic phases were washed with saturated brine (3 × 50 mL), dried over anhydrous sodium sulfate, filtered, and the solvent was evaporated to obtain N-tert-butyl-α-isopropylnitrone (5.88 g, yield 68%). Subsequently, 3-bromopyridine (5.68 g, 36 mmol) was dissolved in tetrahydrofuran (40 mL). After being frozen in liquid nitrogen, evacuated, and purged with nitrogen three times, 2M isopropyl magnesium chloride tetrahydrofuran solution (17.9 mL, 35.8 mmol) was slowly added at −78 °C. The mixture was allowed to rise naturally to room temperature and stirred for 7 h. The system was then cooled to 0 °C, and N-tert-butyl-α-isopropylnitrone (3.48 g, 24 mmol) was slowly added dropwise. After the addition was complete, the mixture was allowed to rise to room temperature and the reaction continued for 16 h. After the reaction was completed, the mixture was quenched with saturated ammonium chloride solution (30 mL), extracted with diethyl ether (3 × 40 mL), and the organic phases were combined, dried over anhydrous sodium sulfate, filtered, and evaporated to dryness. The mixture was then purified by column chromatography with petroleum ether / ethyl acetate = 4 / 1 (V / V) to give N-(tert-butyl)-N-(2-methyl-1-(pyridin-3-yl)propyl)hydroxylamine (3.0 g, yield 56%). The hydroxylamine intermediate (1.2 g, 5.4 mmol) and benzyl bromide (3.2 mL, 27 mmol) were then dissolved in dichloromethane (10 mL) and reacted overnight at room temperature. The filter cake was washed with dichloromethane (3 × 40 mL) and dried under vacuum to give PTNOH (1.7 g, 80% yield). PTNOH (450 mg, 1.15 mmol) and copper acetate monohydrate (30 mg, 0.15 mmol) were added to a 20 mL vial, followed by methanol (5 mL) and ammonia (600 μL, 25% to 28%). Air was bubbled through the vial for 15 to 20 min, and then saturated sodium bisulfite solution (1 mL) was added. The mixture was filtered, and the filtrate was extracted with chloroform in three fractions (total volume 90 mL). The organic phases were combined, dried over anhydrous sodium sulfate, filtered, and evaporated to dryness. The mixture was then purified by preparative HPLC with a water / methanol mixture as the mobile phase, using a water / methanol gradient of 60 / 40 to 30 / 70 (V / V) to obtain water-soluble nitroxide radical PTNO (248 mg, yield 55%).Finally, PTNO (162 mg, 0.414 mmol), 2-bromomethylquinoline (87.1 mg, 0.392 mmol), copper powder (12.5 mg, 0.196 mmol), and 2,2'-bipyridine (61.3 mg, 0.392 mmol) were dissolved in acetonitrile (10 mL). After being frozen in liquid nitrogen, evacuated, and purged with nitrogen three times, the reaction was carried out overnight at room temperature. After the reaction was completed, the solution was diluted with chloroform (30 mL), and the organic phase was washed successively with 10% hydrochloric acid (3 × 10 mL), saturated sodium bicarbonate solution (3 × 20 mL), and saturated saline solution (3 × 20 mL). The solution was then dried over anhydrous sodium sulfate, filtered, and evaporated to dryness. The solution was purified by preparative HPLC with a water / methanol mixture as the mobile phase and a gradient of water / methanol = 35 / 65 to 15 / 85 (V / V) to obtain the target water-soluble alkoxyamine initiator PQN (203 mg, yield 45%). The obtained PQN was analyzed by proton nuclear magnetic resonance spectroscopy. 1 H NMR, carbon nuclear magnetic resonance (NMR) 13 The structure was confirmed by C10 NMR and high-resolution mass spectrometry (ESI-MS), and the characterization data are as follows:

[0059] 1 H NMR (500 MHz, DMSO-d6) δ 9.49 (s, 1H), 9.18 (d, J = 6.1 Hz, 1H), 8.94 (d, J = 8.2 Hz, 1H), 8.42 (d, J = 8.5 Hz, 1H), 8.14 (dd, J = 8.0, 6.1Hz, 1H), 8.06 (d, J = 8.4 Hz, 1H), 8.02 (dd, J = 8.2, 1.4 Hz, 1H), 7.79 (ddd,J = 8.5, 6.8, 1.5 Hz, 1H), 7.63 (td, J = 7.4, 6.7, 1.2 Hz, 1H), 7.54 (d, J =8.4 Hz, 1H), 7.40–7.19 (m, 5H), 5.81 (s, 2H), 5.27 (dd, J = 89.2, 12.2 Hz, 2H), 4.01 (d, J = 10.7 Hz, 1H), 2.47–2.35 (m, 1H), 1.32 (d, J = 6.3 Hz, 3H), 0.92 (s, 9H), 0.55 (d, J = 6.6 Hz, 3H). The HH COSY assignments for each signal peak are shown in [reference needed]. Figure 2 .

[0060] 13C NMR (126 MHz, DMSO-d6) δ 157.74, 147.95, 147.56, 145.84, 143.68,143.19, 137.51, 134.96, 130.43, 129.66, 129.48, 129.00, 128.46, 127.84,127.70, 127.08, 120.55, 80.50, 68.40, 63.94, 61.02, 31.43, 27.86, 21.70,20.71.

[0061] ESI-MS: m / z [M − Br] + calcd for C30H36N3O + , 454.2853; found, 454.2800.

[0062] The above NMR and mass spectrometry results demonstrate the successful acquisition of the target water-soluble alkoxyamine initiator PQN.

[0063] As a control, when the quinoline group in PQN was replaced with pyridine, naphthalene, and benzene, respectively, none of the corresponding structures could function as water-soluble alkoxyamine initiators. Figure 6 As shown. Specifically, if the pyridine group is used, firstly, there is no commercially available precursor, 2-bromomethylpyridine, and secondly, the yield of this alkoxyamine synthesis is extremely low, making it impossible to effectively separate the corresponding product; while if quinoline is replaced with naphthalene or benzene, the product is insoluble in water and cannot be used for aqueous NMP.

[0064] Example 2: This example provides a method for preparing the supramolecular complex CB[8]-PQN, as follows:

[0065] PQN and cucurbita[8]urea (CB[8]) are dissolved in water or deuterium water respectively, and mixed at a molar ratio of PQN:CB[8]=1:1. The mixture is thoroughly mixed at room temperature to obtain the CB[8]-PQN complex.

[0066] For 1 For 1H NMR characterization, PQN can be prepared as a 2mM deuterium aqueous solution, and CB[8] can be prepared as a 120μM deuterium aqueous solution. Take 500μL of CB[8] deuterium aqueous solution (120μM) and place it in an NMR tube. Gradually add PQN deuterium aqueous solution until PQN and CB[8] reach an equimolar ratio. After mixing evenly, perform 1H NMR spectrum testing. According to this ratio, 500μL of 120μM CB[8] solution contains 60nmol of CB[8], which corresponds to about 30μL of 2mM PQN solution.

[0067] When used for isothermal titration calorimetry (ITC) characterization, PQN was prepared as a 0.8 mM aqueous solution and CB[8] was prepared as a 0.08 mM aqueous solution. The PQN solution was added dropwise to the CB[8] solution at 25 °C, with each injection volume being 2 μL.

[0068] like Figure 3 As shown, 1 ¹H NMR results showed that after PQN bound to CB[8], the proton peaks of the pyridinium fragment and part of the quinoline fragment shifted significantly, indicating that both participated in the cavity inclusion of CB[8]. This result shows that CB[8] can simultaneously recognize the cationic and aromatic ends in the PQN molecule, causing PQN to form an intramolecular folded conformation.

[0069] like Figure 4 As shown, ITC testing further confirms that PQN forms a 1:1 host-guest complex with CB[8], with a binding constant of 9.8 × 10⁻⁶. 6 M −1 This indicates that the two have a strong binding ability.

[0070] Example 3: This example provides a method for applying PQN and CB[8]-PQN in aqueous NMP, as follows:

[0071] PQN and CB[8]-PQN were used as monomer initiators for the aqueous NMP polymerization of sodium 4-vinylbenzenesulfonate (SS). The specific operation was as follows: SS and the corresponding initiator were dissolved in water, the molar ratio of monomer to initiator was controlled to be approximately 3500:1, nitrogen was purged for 30 min to remove oxygen, and polymerization was carried out at 95℃. Samples were taken at different time points, and the polymerization was carried out by... 1 The monomer conversion rate was calculated by 1H NMR, and the molecular weight and molecular weight distribution of the obtained polymer were determined by GPC.

[0072] like Figure 5 As shown, when free PQN initiates the polymerization of SS, the system has a polymerization induction period of approximately 4 hours, and the monomer conversion rate is approximately 58% after 24 hours. Polymerization kinetics analysis shows that its apparent polymerization rate constant is 0.055 h⁻¹. −1 GPC results showed that PQN could initiate NMP in aqueous solution by SS. The molecular weight of the resulting polymer increased with increasing monomer conversion rate. The experimental molecular weight was in good agreement with the theoretical molecular weight. The final molecular weight distribution Mw / Mn was approximately 1.35, indicating that PQN can serve as a monomer initiator for aqueous NMP and has controlled polymerization characteristics.

[0073] Under the same polymerization conditions, PQN was pre-formed with an equimolar amount of CB[8] to form a CB[8]-PQN complex before being used for NMP polymerization in the SS aqueous phase. The results showed that the CB[8]-PQN initiating system could achieve a monomer conversion of about 20% within 0.5 h, and the conversion was about 70% after 16 h. Its apparent polymerization rate constant increased to 0.13 h. −1 The value is approximately 2.4 times that of the free PQN system. This result indicates that the formation of a complex between CB[8] and PQN can significantly shorten the polymerization induction period and increase the polymerization rate.

[0074] Meanwhile, the molecular weight of the polymer obtained by the CB[8]-PQN system still increased with the increase of monomer conversion rate, and the experimental molecular weight was basically consistent with the theoretical molecular weight. The final molecular weight distribution Mw / Mn was about 1.38. This indicates that the addition of CB[8] mainly improved the initiation and polymerization efficiency of PQN, and did not destroy the controllable / active characteristics of NMP polymerization.

[0075] In addition, when CB[8] is replaced with cucurbita[7]urea (CB[7]), under the same polymerization conditions, the CB[7]-PQN complex can also improve the polymerization efficiency compared with PQN, specifically by shortening the induction period to 2 hours and the polymerization rate constant to 0.070h. −1 The efficiency was increased by 1.3 times. However, the overall effect was still not as good as CB[8]. The corresponding polymerization efficiency characterization is as follows: Figure 7 and Figure 8 As shown.

[0076] In summary, this invention has achieved aqueous NMP polymerization of sodium 4-vinylbenzenesulfonate by synthesizing a novel water-soluble alkoxyamine initiator, PQN. Furthermore, by forming a 1:1 folded host-guest supramolecular complex with PQN and CB[8], the polymerization induction period can be significantly shortened, the polymerization rate increased, and the controllability of the polymer molecular weight and molecular weight distribution maintained. Therefore, PQN and its CB[8] supramolecular complex can serve as a novel aqueous NMP initiation system for the efficient preparation of water-soluble polymers.

[0077] Based on the above-described preferred embodiments of the present invention, and through the foregoing description, those skilled in the art can make various changes and modifications without departing from the inventive concept. The technical scope of this invention is not limited to the contents of the specification.

Claims

1. A water-soluble alkoxyamine initiator, characterized in that, It includes a pyridinium benzyl structure and a quinoline aromatic structure, with the following structural formula: 。 2. The method for synthesizing the water-soluble alkoxyamine initiator as described in claim 1, characterized in that, Includes the following steps: Isobutyraldehyde is reacted with 2-methyl-2-nitropropane to produce N-tert-butyl-α-isopropylnitrone; N-tert-butyl-α-isopropylnitrone was reacted with 3-bromopyridine via a Grignard reaction to give a pyridine-substituted hydroxylamine intermediate; The hydroxylamine intermediate was substituted with pyridine and introduced into a benzylpyridinium structure via a benzyl quaternization reaction to obtain the hydroxylamine precursor; The hydroxylamine precursor was oxidized to obtain water-soluble nitric oxide free radicals; A water-soluble nitric oxide radical was reacted with 2-bromomethylquinoline to obtain a water-soluble alkoxyamine initiator.

3. The method for synthesizing the water-soluble alkoxyamine initiator according to claim 2, characterized in that, Isobutyraldehyde reacts with 2-methyl-2-nitropropane in the presence of ammonium chloride and zinc powder.

4. The method for synthesizing the water-soluble alkoxyamine initiator according to claim 2, characterized in that, Water-soluble nitric oxide radicals react with 2-bromomethylquinoline in the presence of copper powder and 2,2'-bipyridine.

5. A supramolecular complex, characterized in that, Includes the water-soluble alkoxyamine initiator as described in claim 1 and cucurbituril.

6. The supramolecular complex according to claim 5, characterized in that, The cucurbituril is cucurbituril[8] urea.

7. The supramolecular complex according to claim 5, characterized in that, The molar ratio of the water-soluble alkoxyamine initiator to cucurbituril is 1:(0.8–1.2).

8. The use of the water-soluble alkoxyamine initiator as described in claim 1 or the supramolecular complex as described in any one of claims 5 to 7 in aqueous nitrogen-oxygen stable free radical polymerization.

9. The application according to claim 8, characterized in that, The method for aqueous nitrogen-oxygen stable free radical polymerization is as follows: the water-soluble alkoxyamine initiator or supramolecular complex is mixed with the water-soluble vinyl monomer in water, and after deoxygenation treatment, the mixture is heated to the polymerization initiation temperature to carry out the polymerization reaction.

10. The application according to claim 9, characterized in that, The water-soluble vinyl monomer includes sodium 4-vinylbenzenesulfonate; the molar ratio of the water-soluble vinyl monomer to the water-soluble alkoxyamine initiator or supramolecular complex is (3000–4000):1; the polymerization temperature is 80–100°C.

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