Thermoresponsive micelles and crosslinked micelles, and methods of making and using the same

Abstract

The application provides a kind of thermoresponsive micelles and crosslinked micelles and its preparation method and application, it is related to lubricant additive technical field.The application mixes sulfide carbonate chain transfer agent, first monomer (glyceryl methacrylate, 2-hydroxyethyl methacrylate and one or several of oxirane), first initiator and organic solvent to carry out RAFT polymerization, obtain macromolecular chain transfer agent;The macromolecular chain transfer agent is mixed with second monomer (including N-isopropyl acrylamide), second initiator and water to carry out polymerization induced self-assembly, obtain thermoresponsive micelles.The application also provides a kind of crosslinked micelles, which is obtained by crosslinking the thermoresponsive micelles with borate ions.The thermoresponsive micelles or crosslinked micelles are used as water lubricating additives for friction lubrication, which can reduce friction and wear and keep the friction coefficient unchanged (friction coefficient ≤0.2) under higher / lower LCST temperature and different loads, with self-adaptability.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of lubricant additives, in particular to a kind of thermal response micelles and crosslinking micelles and preparation method and application thereof. BACKGROUND

[0002] Compared with lubricating oil, water has lower viscosity, although low friction coefficient and wear rate are generated in the process of friction, but it is difficult to form lubricating water film on the friction interface, which leads to the carrying capacity of water is worse than oil, can cause serious cavitation wear, corrosion and leakage, greatly limit the application of water lubrication. SUMMARY

[0003] Therefore, the purpose of the present application is to provide a kind of thermal response micelles and crosslinking micelles and preparation method and application thereof.The thermal response micelles prepared by the present application can significantly improve the friction and wear performance of water-based lubricant as water lubricating additive, and have self-adaptive lubrication performance.

[0004] In order to achieve the above-mentioned purpose of the application, the present application provides the following technical solutions:

[0005] The present application provides a kind of preparation method of thermal response micelles, comprising the following steps:

[0006] The macromolecular chain transfer agent is obtained by mixing thio carbonic ester chain transfer agent, first monomer, first initiator and organic solvent for RAFT polymerization;The thio carbonic ester chain transfer agent includes 2-cyano-2-propyl dithio benzoate and / or 4-cyano-4-thiobenzoyl valeric acid;The first monomer includes one or more of glyceryl methacrylate, 2-hydroxyethyl methacrylate and oxirane;

[0007] The macromolecular chain transfer agent is obtained by mixing thio carbonic ester chain transfer agent, first monomer, first initiator and organic solvent for RAFT polymerization;The thio carbonic ester chain transfer agent includes 2-cyano-2-propyl dithio benzoate and / or 4-cyano-4-thiobenzoyl valeric acid;The first monomer includes one or more of glyceryl methacrylate, 2-hydroxyethyl methacrylate and oxirane;

[0008] Preferably, the first initiator and the second initiator independently include one or more of 4,4'-azobis (4-cyanovaleric acid), 2,2'-azobis (2-(2-imidazoline-2-yl) propane) dihydrochloride and 2,2'-azobis (2-methylpropyl amidine) dihydrochloride.

[0009] Preferably, the molar ratio of the thio carbonic ester chain transfer agent, the first monomer and the first initiator is 1: (20-40) : 0.2.

[0010] Preferably, the temperature of the RAFT polymerization is 50-70 DEG C, and the time is 10-15 h.

[0011] Preferably, the molar ratio of the macromolecular chain transfer agent, the second monomer and the second initiator is 1:(50-110):1.1.

[0012] Preferably, the temperature for the polymerization-induced self-assembly is 60-80℃, and the time is 15-24h.

[0013] The present application provides a thermoresponsive micelle prepared by the preparation method.

[0014] The present application provides a crosslinked micelle prepared by crosslinking the thermoresponsive micelle with borate ions.

[0015] Preferably, the molar ratio of the hydroxyl group in the thermoresponsive micelle to the boron ion in the borate ion is 1:(0.052-0.2), and the crosslinking temperature is 60-80℃, and the time is 8-10h.

[0016] The present application provides the application of the thermoresponsive micelle or the crosslinked micelle as an additive of a water-based lubricant.

[0017] The present application provides a preparation method of a thermoresponsive micelle, comprising the following steps: mixing a thiocarbonic ester chain transfer agent, a first monomer, a first initiator and an organic solvent to perform RAFT polymerization, to obtain a macromolecular chain transfer agent; the first monomer comprises one or more of glyceryl methacrylate, 2-hydroxyethyl methacrylate and oxirane; mixing the macromolecular chain transfer agent with a second monomer, a second initiator and water to perform polymerization-induced self-assembly, to obtain the thermoresponsive micelle; the second monomer comprises N-isopropyl acrylamide. The present application connects the hydrophilic block (i.e. the first monomer) to the thiocarbonic ester chain transfer agent through RAFT polymerization, and then connects the hydrophobic block N-isopropyl acrylamide to form a diblock copolymer and self-assembles, i.e. synthesizes micelle particles with uniform structure in an aqueous solution through the polymerization-induced self-assembly technology (PISA). Due to the introduction of N-isopropyl acrylamide, the polymer micelle particles have temperature responsiveness, and realize the reversible transition between the spherical micelles and smaller micelles above / below the LCST temperature (≈31℃). Specifically, above the LCST temperature, the hydrophobic effect of the N-isopropyl acrylamide block drives the synthesized polymer to self-assemble in the solution to form spherical micelles, below the LCST temperature, the N-isopropyl acrylamide block dissolves in water, the hydrophobic effect (driving effect) disappears, the spherical micelles are disassembled, and the polymer chains in the solution are aggregated to form smaller micelles, and the process has multiple reversibility.

[0018] The application provides a cross-linked micelle obtained by cross-linking the thermoresponsive micelle in the above technical solution with borate ions. The application keeps the originally self-assembled structure of the polymer destroyed below the LCST temperature in a spherical morphology at room temperature through cross-linking with borate ions.

[0019] The application provides an application of the thermoresponsive micelle in the above technical solution or the cross-linked micelle in the above technical solution as a water-based lubricant additive. The thermoresponsive micelle or the cross-linked micelle is used as a water lubricant additive for friction lubrication, and the friction and wear can be reduced, and the friction coefficient remains unchanged under the condition of higher / lower LCST temperature and different loads, and the application has self-adaptability. The results of the examples show that the friction coefficient is less than or equal to 0.2, and the pressure bearing capacity can reach 70 N when the thermoresponsive micelle or the cross-linked micelle provided by the application is used as a water-based lubricant additive. BRIEF DESCRIPTION OF DRAWINGS

[0020] Figure 1 The reaction involved in preparing the thermoresponsive micelle in the examples;

[0021] Figure 2 The principle schematic diagram of the cross-linked micelle in the examples of the application;

[0022] Figure 3 The TEM diagram of the spherical micelle G 32 -N 100 in Example 1;

[0023] Figure 4 The TEM diagram of the cross-linked micelle G 32 -N 100 -B in Example 3;

[0024] Figure 5 The GPC test results of the macromolecular chain transfer agent PGMA 32 -CTA and the polymer micelle G 32 -N 100 in Example 1;

[0025] Figure 6 The dynamic light scattering test results of the micelle G 32 -N 100 synthesized in Example 1, Figure 6 wherein (a) is the particle size change of the micelle at different temperatures, and (b) is the particle size change of the micelle with temperature under the condition of alternating two temperatures of 25 DEG C and 36 DEG C;

[0026] Figure 7 The transmittance change of the micelle G 32 -N 100 with temperature change;

[0027] Figure 8 The transmittance change of the micelle G 32- N 100 - B change in transmittance with temperature;

[0028] Figure 9 G for H2O, uncrosslinked spherical micelles 32 - N 100 - B appearance with temperature;

[0029] Figure 10 G for H2O, uncrosslinked spherical micelles 32 - N 100 and crosslinked spherical micelles G 32 - N 100 - B change in coefficient of friction with load at 25°C;

[0030] Figure 11 G for H2O, uncrosslinked spherical micelles 32 - N 100 and crosslinked spherical micelles G 32 - N 100 - B change in coefficient of friction with load at 36°C;

[0031] Figure 12 G for H2O, uncrosslinked spherical micelles 32 - N 100 G as a lubricating additive, wear volume on steel counterface surface at different load test conditions at 25°C and 36°C, Figure 12 G where (a) is wear volume on steel counterface surface at different load test conditions at 25°C and (b) is wear volume on steel counterface surface at different load test conditions at 36°C;

[0032] Figure 13 G for H2O, uncrosslinked spherical micelles 32 - N 100 - B wear volume on steel counterface surface at different load test conditions at 25°C and 36°C, G as a lubricating additive, Figure 13 G where (a) is wear volume on steel counterface surface at different load test conditions at 25°C and (b) is wear volume on steel counterface surface at different load test conditions at 36°C. DETAILED DESCRIPTION

[0033] The present application provides a preparation method of a thermal responsive micelle, comprising the following steps:

[0034] mixing a thio carbonic ester chain transfer agent, a first monomer, a first initiator and an organic solvent to perform RAFT polymerization to obtain a macromolecular chain transfer agent; the thio carbonic ester chain transfer agent comprises one or more of 2-cyano-2-propyl dithiobenzoate and / or 4-cyano-4-thiobenzoyl valeric acid; the first monomer comprises one or more of glyceryl methacrylate, 2-hydroxyethyl methacrylate and oxirane;

[0035] The macromolecular chain transfer agent is mixed with a second monomer, a second initiator and water to perform polymerization-induced self-assembly, so as to obtain the thermoresponsive micelles; the second monomer comprises N-isopropyl acrylamide.

[0036] In the present application, the raw materials involved are all commercially available products well known in the art, unless otherwise specified.

[0037] The macromolecular chain transfer agent is obtained by mixing a thio carbonic ester chain transfer agent, a first monomer, a first initiator and an organic solvent to perform RAFT polymerization.

[0038] In the present application, the thio carbonic ester chain transfer agent comprises 2-cyano-2-propyl dithiobenzoate and / or 4-cyano-4-thiobenzoyl valeric acid, preferably 2-cyano-2-propyl dithiobenzoate (CPDB). In the present application, the first monomer comprises one or more of glyceryl methacrylate (GMA), 2-hydroxyethyl methacrylate and polyethylene oxide (PEO), preferably glyceryl methacrylate (GMA); the first monomer is a hydrophilic monomer. In the present application, the first initiator preferably comprises one or more of 4,4'-azobis(4-cyanopentanoic acid) (ACVA), 2,2'-azobis(2-(2-imidazolin-2-yl)propane) dihydrochloride and 2,2'-azobis(2-methylpropionamidine) dihydrochloride, more preferably 4,4'-azobis(4-cyanopentanoic acid) (ACVA); the first initiator is a thermal initiator. In the present application, the molar ratio of the thio carbonic ester chain transfer agent, the first monomer and the first initiator is preferably 1:(20-40):0.2, which can be 1:20:0.2, 1:25:0.2, 1:30:0.2, 1:32:0.2, 1:35:0.2 or 1:40:0.2. In the present application, the organic solvent is preferably an alcohol solvent, which is preferably anhydrous ethanol. In the present application, the solid content of the mixture obtained by mixing the thio carbonic ester chain transfer agent, the first monomer, the first initiator and the organic solvent is preferably 40wt%.

[0039] In the present application, the temperature of the RAFT polymerization (i.e. reversible addition-fragmentation chain transfer polymerization) is preferably 50-70℃, which can be 50℃, 60℃ or 70℃, and the time is preferably 10-15h, which can be 10h, 11h, 12h, 13h, 14h or 15h. In the present application, the RAFT polymerization is preferably performed under the conditions of no oxygen, oil bath and stirring, and the no oxygen is specifically removed by argon purging.

[0040] The present application adopts the RAFT polymerization technology, which is one of the active radical polymerization, has a wide range of reaction conditions and monomer selection, and can obtain a polymer with a narrow molecular weight distribution and good dispersity.

[0041] After the RAFT polymerization is completed, the present application preferably drops the obtained reaction solution into n-hexane to precipitate the solid, and dries the solid to obtain the macromolecular chain transfer agent. In the embodiments of the present application, the temperature of the drying is preferably 40℃, and the time is preferably 12h, and the drying is preferably vacuum drying.

[0042] After obtaining the macromolecular chain transfer agent, the present application mixes the macromolecular chain transfer agent with a second monomer, a second initiator and water to perform polymerization-induced self-assembly to obtain the thermoresponsive micelles.

[0043] In the present application, the second monomer includes N-isopropyl acrylamide (NIPAM); the second monomer serves as a hydrophobic monomer. In the present application, the second initiator preferably includes one or more of 4,4'-azobis(4-cyanopentanoic acid) (ACVA), 2,2'-azobis(2-(2-imidazolin-2-yl)propane) dihydrochloride and 2,2'-azobis(2-methylpropyrimidamide) dihydrochloride, and more preferably 4,4'-azobis(4-cyanopentanoic acid) (ACVA). In the present application, the molar ratio of the macromolecular chain transfer agent, the second monomer and the second initiator is preferably 1:(50-110):1.1, and can be 1:50:1.1, 1:60:1.1, 1:70:1.1, 1:80:1.1, 1:90:1.1, 1:100:1.1 or 1:110:1.1. In the present application, the water is preferably deionized water, and the solid content of the mixture obtained by mixing the macromolecular chain transfer agent with the second monomer, the second initiator and water is preferably 5-15wt%, and more preferably 10wt%; the solid content range is advantageous to maintaining the morphology of the self-assembled body. Because the morphology formed by polymerization-induced self-assembly is affected by the polymerization degree of the hydrophilic block and the hydrophobic block, the present application controls the ratio of the first monomer and the second monomer to obtain micelles with spherical morphology, and the size of the micelles is different, but the performance is basically unchanged, thereby making the synthesized micelles have self-adaptability.

[0044] In the present application, the temperature of the polymerization-induced self-assembly is preferably 60-80℃, and can be 60℃, 70℃ or 80℃, and the time is preferably 15-24h, and can be 15h, 20h or 24h. In the present application, the polymerization-induced self-assembly is preferably performed under the conditions of no oxygen, oil bath and stirring, and the no oxygen is specifically removing oxygen by argon purging. In the process of the polymerization-induced self-assembly, the macromolecular chain transfer agent and the second monomer first form a diblock copolymer through RAFT polymerization under the action of the second initiator, and when the polymer chain reaches a certain degree, self-assembly will be performed, so it is a process of polymerization and self-assembly at the same time in the reaction. After the polymerization-induced self-assembly, spherical micelles with a certain polymerization degree are obtained.

[0045] With the first monomer being glyceryl methacrylate (GMA), the thio carbonic acid chain transfer agent being 2-cyano-2-propyl dithio-benzoate (CPDB), and the second monomer being N-isopropyl acrylamide (NIPAM) as examples, the reaction involved in preparing the thermoresponsive micelles by the embodiments of the present application is shown in Figure 1 .

[0046] The present application adopts the polymerization-induced self-assembly technology (PISA) to synthesize spherical nanomicelle particles in water, compared with the traditional self-assembly technology, the spherical micelle particles with uniform structure can be in-situ synthesized in the same aqueous solution in a wide concentration range (5-15%) and can be self-assembled in the solution while polymerizing, which is simple to operate.

[0047] The present application provides the thermoresponsive micelles prepared by the preparation method.

[0048] In the present application, the number average molecular weight of the thermoresponsive micelles is greater than or equal to 16000. In the present application, the thermoresponsive micelles have thermoresponsive property due to the temperature responsiveness of the poly-N-isopropyl acrylamide (PNIPAM) therein. In the present application, the LCST temperature (i.e. the lower critical solution temperature) of the thermoresponsive micelles is approximately 31℃. Since the self-assembly process is a physical process, when the temperature is higher than the LCST temperature, the PNIPAM block is hydrophobic, and the hydrophobic interaction drives the polymer to self-assemble into spherical micelles in the solution. When the temperature is lower than the LCST temperature, the PNIPAM polymer is hydrophilic, the hydrophobic interaction disappears, and the self-assembly structure is destroyed. The present application subsequently crosslinks by adding a crosslinking agent to keep the spherical morphology at room temperature.

[0049] The present application provides a crosslinked micelle obtained by crosslinking the thermoresponsive micelles with borate ions.

[0050] In the present application, the molar ratio of the hydroxyl groups (from the first monomer segment) in the thermoresponsive micelles to the boron ions in the borate ions is preferably 1:(0.052-0.2), which can be 1:0.052, 1:0.08, 1:0.12, 1:0.16 or 1:0.2. The borate ions are preferably provided by sodium borate, and in the embodiments of the present application, the sodium borate is specifically sodium tetraborate decahydrate (Na2B4O7·10H2O). In the present application, the borate ions act as a crosslinking agent. The present application preferably adds a sodium tetraborate aqueous solution to the micelle-containing reaction solution obtained by the above polymerization-induced self-assembly to perform a crosslinking reaction, and the concentration of the sodium tetraborate aqueous solution is preferably 0.084 mol / L. In the present application, the temperature of the crosslinking is preferably 60-80℃, which can be 60℃, 70℃ or 80℃, and the time is preferably 8-10h, which can be 8h, 9h or 10h.

[0051] Figure 2Schematic diagram of the principle of cross-linked micelles for the embodiments of the present application. Take the heat-responsive micelles synthesized by glyceryl methacrylate (GMA) as the first monomer as an example, introduce borate ions as the cross-linking agent, cross-link the micelle shell by forming B-O bonds between the -OH groups on the polymethyl glyceryl methacrylate (PGMA) to stabilize the micelles and prevent the micelles from collapsing during the inevitable cooling (room temperature < LCST), Figure 2 The middle blue line represents the polymethyl glyceryl methacrylate segment, the red line represents the poly-N-isopropyl acrylamide (PNIPAM) segment, and the green line represents the B-O bond.

[0052] The cross-linked micelles provided by the present application still have good temperature responsiveness. When the temperature rises, the PNIPAM segment in the cross-linked micelles is insoluble in water, and the inner layer becomes compact in the form of loosely cross-linked polymer chains, so that the size of the overall spherical micelles becomes smaller.

[0053] The present application provides the application of the heat-responsive micelles or the cross-linked micelles as described in the above technical solutions as water-based lubricant additives. Compared with pure water, the heat-responsive micelles and the cross-linked micelles provided by the present application have obvious lubricating effect as water-based lubricant additives. The heat-responsive micelles have self-adaptive lubricating performance, and the friction coefficient remains unchanged at room temperature (25℃) although the self-assembly structure is destroyed. The cross-linked micelles have the same friction coefficient as the non-cross-linked micelles when lubricating. In the embodiments of the present application, the macromolecular chain transfer agent is mixed with the second monomer, the second initiator and water to perform polymerization and induce self-assembly, and further cross-linking with borate ions is performed without any post-treatment. The obtained water solution containing heat-responsive micelles or cross-linked micelles is directly used as a water-based lubricant, and the heat-responsive micelles or cross-linked micelles therein are water-based lubricant additives.

[0054] In order to further illustrate the present application, the heat-responsive micelles and the cross-linked micelles provided by the present application, the preparation method and the application thereof are described in detail in conjunction with examples below, but they should not be understood as limiting the scope of protection of the present application.

[0055] In each embodiment, glyceryl methacrylate (GMA) and 4,4'-azobis (4-cyanopentanoic acid) (ACVA) are purchased from Anhui Zesheng Science and Technology Co., Ltd., and 2-cyano-2-propyl dithiobenzoate (CPDB) is purchased from National Pharmaceutical Group Chemical Reagent Co., Ltd.

[0056] Example 1

[0057] The preparation of the heat-responsive micelles involves the reaction as shown in Figure 1 The preparation steps are as follows:

[0058] (1) Preparation of polymethyl glyceryl methacrylate (PGMA) macromolecular chain transfer agent:

[0059] In a 50 mL Schlenk flask was added chain transfer agent PGMA (1 mmol), GMA (32 mmol), ACVA (0.2 mmol) and absolute ethanol (10.27 mL) in a molar ratio [PGMA-CTA]:[GMA]:[ACVA] = 1 :32:0.2, the mixture was mixed (40% w / w solid content) and purged with argon for 30 min to remove oxygen, the sealed flask was stirred in an oil bath at 60 °C for 11 h. The solution after reaction was dropped into n-hexane to precipitate the solid, which was dried in a vacuum oven at 40 °C for 12 h to obtain the macromolecular chain transfer agent with a polymerization degree DP = 32, the sample was named PGMA 32 -CTA.

[0060] (2) Preparation of thermoresponsive micelles (PGMA 32 -PNIPAM 100 diblock copolymer):

[0061] In a 50 mL Schlenk flask was added macromolecular chain transfer agent PGMA 32 -CTA (0.1 mmol), NIPAM (N-isopropyl acrylamide, 11 mmol), ACVA (0.11 mmol) and H2O (16.3 mL) in a molar ratio [PGMA-CTA]:[NIPAM]:[ACVA] = 1 :110:1.1, purged with argon for 30 min to remove oxygen, then stirred in an oil bath at 70 °C for 20 h, the obtained polymer micelles were represented by PGMA 32 -PNIPAM 32 -PNIPAM 100 denoted by G 32 -N 100 with a polymerization degree DP = 100 of NIPAM.

[0062] Example 2

[0063] In example 1, the molar ratio was changed to: [PGMA-CTA]:[NIPAM]:[ACVA] = 1 :68:1.1, the rest was the same as example 1, the obtained polymer was represented by PGMA 32 -PNIPAM 32 -PNIPAM 62 denoted by G 32 -N 62 .

[0064] Example 3

[0065] Preparation of crosslinked micelles (denoted by PGMA 32 -PNIPAM 100 -B).

[0066] G was synthesized from step (2) of Example 1. 32 -N 100 After micelle formation, a crosslinking reaction was initiated by adding a sodium tetraborate decahydrate aqueous solution (0.084 mol / L, 1 mL) to the reaction solution at a molar ratio of [-OH]:[Na2B4O7·10H2O] = 1:0.013. The reaction was carried out under sealed conditions at 70℃ for 8 h to obtain crosslinked micelles, i.e., PGMA. 32 -PNIPAM 100 -B, abbreviated as G 32 -N 100 -B.

[0067] The micelles prepared in the examples and the cross-linked micelles prepared in the examples were tested, as follows:

[0068] (1) Polymer G synthesized in Example 1 32 -N 100 Transmission electron microscopy (TEM) was performed at 36°C after dilution with deionized water. The results are as follows: Figure 3 As shown, this demonstrates that the self-assembled structure has a spherical morphology. The cross-linked micelles G synthesized in Example 3... 32 -N 100 -B samples were prepared by dilution at room temperature and then subjected to TEM testing. The results are as follows: Figure 4 As shown, a spherical morphology was observed, proving successful cross-linking.

[0069] (2) Regarding the macromolecular chain transfer agent PGMA in Example 1 32 -CTA and polymer micelles G 32 -N 100 GPC (gel permeation chromatography) was performed, and the results are as follows: Figure 5 As shown, this demonstrates that the polymer has a uniform molecular weight distribution.

[0070] (3) The micelles G synthesized in Example 1 32 -N 100 Dynamic light scattering (DLS) was performed, and the results are as follows: Figure 6 As shown, Figure 6 In the figure, (a) shows the change in micelle size at different temperatures, and (b) shows the change in micelle size with temperature when the temperatures of 25℃ and 36℃ are alternated.

[0071] The size of the synthesized spherical micelles was measured by dynamic light scattering after the solution was diluted. Figure 6 (a) shows that the particle size is small in the solution at low temperatures. When the temperature is above LCST, the diameter of the particles in the solution suddenly increases and then remains constant, proving that the synthesized micelles have temperature responsiveness. The change in micelle size with temperature was measured alternately at two temperatures (36℃ and 25℃), as shown in Figure (a).Figure 6 As shown in (b), the particle size can change cyclically with temperature multiple times, proving that the synthesized spherical micelles have temperature reversibility.

[0072] (4) Measuring micelle G using an ultraviolet spectrophotometer 32 -N 100 The transmittance change with temperature was measured at different wavelengths from 200 to 800 nm within a temperature range of 25 to 45 °C. The test results are as follows: Figure 7 As shown. By Figure 7 It can be seen that the solution has high transparency below the LCST temperature, but the transmittance of the solution suddenly decreases when the temperature is above the LCST temperature, proving that the synthesized polymer has temperature responsiveness.

[0073] Micelle G was measured using a UV spectrophotometer under the same conditions. 32 -N 100 The change in transmittance of -B with temperature is shown in the test results. Figure 8 As shown. By Figure 8 It can be seen that the cross-linked spherical micelles still exhibit good temperature response. (Note: Figure 7 and Figure 8 The focus is on the change in transmittance around the LCST temperature, primarily distinguishing between the changes in the blue and red lines. Figure 7 For example, micelles form above 32°C, the solution becomes insoluble, and the solution as a whole becomes opaque. Therefore, the temperature curves above 32°C overlap and overlap. However, below LCST, the solution is transparent, and the curves overlap.

[0074] (5) Polymer micelles G 32 -N 100 Appearance that changes with temperature

[0075] Figure 9 For polymer micelles G 32 -N 100 The appearance changes with temperature; due to its temperature responsiveness, above the LCST, the polymer self-assembles into micelles, and the solution changes from transparent to opaque. Polymer micelles G 32 -N 62 Appearance changes with temperature and Figure 9 Maintain consistency.

[0076] (6) The tribological behavior of the micelles was studied using a friction and wear tester in a ball-on-disc reciprocating mode. The friction tests were carried out at two characteristic temperatures, 25°C and 36°C, which correspond to the thermal expansion of the micelles. The test frequency was 25 Hz, the amplitude was 1 mm, the loads were 20 N, 50 N and 70 N, respectively, and the friction pair was steel holder and steel ball, each for 20 minutes. To ensure the reliability of the results, three repeated tests were carried out for each sample under each condition, and the average values were statistically significant.

[0077] Figure 10 and Figure 11 H2O, uncrosslinked spherical micelles G 32 -N 100 and crosslinked spherical micelles G 32 -N 100 The friction coefficients of the micelles G 32 -N 100 at 25°C and 36°C as a function of load. The friction tests prove that the spherical micelles G 32 -N 100 lubricated with the crosslinked micelles G 32 -N 100 have a constant friction coefficient (≤ 0.2), proving that the self-assembly process of the polymer does not affect the friction coefficient.

[0078] Figure 12 G 32 -N 100 The wear volume of the steel holder surface when the micelles are used as lubricating additives at 25°C and 36°C under different load test conditions, Figure 12 (a) at 25°C under different load test conditions, and (b) at 36°C under different load test conditions. The corresponding data are listed in Table 1. As Figure 12 and shown in Table 1, the wear volume of the steel holder surface when the micelles G 32 -N 100 are used as lubricating additives is significantly reduced at a load of 20-70 N. This is in line with the fact that Figure 10 the friction coefficient is also significantly reduced, indicating that the micelles have good lubricating properties and have self-adaptive lubricating properties.

[0079] Figure 13 G 32 -N 100 The wear volume of the steel holder surface when the micelles G Figure 13The wear volume of the steel counter surface under different load test conditions at 25°C for (a) and at 36°C for (b). The corresponding data are listed in Table 1. From Figure 13 As can be seen from the results in Table 1, compared with the uncrosslinked micelles, the G 32 -N 100 The wear volume of the G-B micelles as a lubricating additive remained basically unchanged, indicating that during the lubrication process, with the increase of temperature, the self-assembly process of the polymer did not affect the lubricating performance.

[0080] Table 1 Wear volume of the G 32 -N 100 and G 32 -N 100 The wear volume of the G-B micelles as a lubricating additive on the steel counter surface under different load test conditions at 25°C and 36°C

[0081]

[0082] The above only describes the preferred embodiments of the present application, and does not limit the present application in any form. It should be noted that for those skilled in the art, without departing from the principles of the present application, a number of improvements and refinements can be made, and these improvements and refinements should also be considered as the protection scope of the present application.

Claims

1. A crosslinked micelle, characterized in that, The crosslinked micelles are obtained by crosslinking of the thermoresponsive micelles with borate ions, and the preparation method of the thermoresponsive micelles comprises the following steps: The macromolecular chain transfer agent is obtained by mixing a thiocarbonic chain transfer agent, a first monomer, a first initiator and an organic solvent for RAFT polymerization; the thiocarbonic chain transfer agent comprises 2-cyano-2-propyl dithiobenzoate and / or 4-cyano-4-thiobenzoyl valeric acid; and the first monomer comprises one or more of glyceryl methacrylate and 2-hydroxyethyl methacrylate. The macromolecular chain transfer agent is mixed with a second monomer, a second initiator and water for polymerization-induced self-assembly to obtain the thermoresponsive micelles; and the second monomer comprises N-isopropyl acrylamide.

2. The crosslinked micelle of claim 1, wherein, The first initiator and the second initiator independently comprise one or more of 4,4'-azobis(4-cyanopentanoic acid), 2,2'-azobis(2-(2-imidazolin-2-yl)propane) dihydrochloride and 2,2'-azobis(2-methylpropyramidine) dihydrochloride.

3. The crosslinked micelle according to claim 1 or 2, characterized in that, The molar ratio of the thiocarbonic chain transfer agent, the first monomer and the first initiator is 1:(20-40):0.

2.

4. The crosslinked micelle of claim 1, wherein, The temperature of the RAFT polymerization is 50-70℃, and the time is 10-15h.

5. The crosslinked micelle according to claim 1 or 2, wherein The molar ratio of the macromolecular chain transfer agent, the second monomer and the second initiator is 1:(50-110):1.

1.

6. The crosslinked micelle of claim 1, wherein, The temperature of the polymerization-induced self-assembly is 60-80℃, and the time is 15-24h.

7. The crosslinked micelle of claim 1, wherein, The molar ratio of the hydroxyl groups in the thermoresponsive micelles to the boron ions in the borate ions is 1:(0.052-0.2); and the crosslinking temperature is 60-80℃, and the time is 8-10h.

8. Use of the crosslinked micelles of any one of claims 1-6 or the thermoresponsive micelles of any one of claims 1-7 as an additive for a water-based lubricant.

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