Functional cyclodextrin polyether macromonomer as well as preparation method and application thereof

Abstract

The invention discloses a functional cyclodextrin polyether macromonomer as well as a preparation method and application thereof, the functional cyclodextrin polyether macromonomer is prepared by condensing cyclodextrin and alkynyl polyethylene glycol siloxane to prepare alkynyl cyclodextrin, and then the alkynyl cyclodextrin and an azido compound are subjected to click chemistry to obtain the functional cyclodextrin polyether macromonomer. The azido compound is prepared from allyl chloride or methyl allyl chloride and sodium azide, and the polycarboxylic acid admixture is prepared based on the polyether macromonomer. The functional cyclodextrin polyether macromonomer with a novel structure is efficiently prepared on the basis of click chemistry for the first time, the polycarboxylic acid additive is prepared on the basis of the polyether macromonomer, the polycarboxylic acid additive effectively improves the workability of concrete under a current concrete raw material system, and the concrete with a high water-binder ratio or a large volume has a good application prospect. The hydration heat release can be effectively controlled, the hydration heat release temperature peak is inhibited, the internal temperature rise of the concrete is reduced, and the generation of temperature cracks is reduced.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of concrete admixtures, in particular, to a functional cyclodextrin polyether macromonomer, a preparation method and application thereof. BACKGROUND

[0002] With the continuous construction of national urbanization and major infrastructure, the concrete industry has been in rapid development, and the demand for concrete raw materials has been at a high level. In recent years, natural river sand, high-quality fly ash and other resources are becoming increasingly scarce, and artificial aggregates, coal gangue and desulfurization ash and other low-activity industrial waste residues have also begun to be gradually used in modern concrete, especially the mechanically produced sand (high in clay content, poor in gradation, and large in lithology difference), which leads to problems such as poor workability of low water-binder ratio concrete, low air content of concrete, bleeding or bleeding of concrete. At the same time, with the development of modern architecture, the demand for mass concrete is increasingly widespread, and the heat release of cement in high-strength concrete components causes rapid heating inside the concrete, and the temperature gradient between the inside and outside of the concrete easily produces large temperature stress, leading to temperature cracks. The temperature peak of mass concrete in high-temperature summer even exceeds 70℃, and this temperature difference is an important reason for the cracks of mass concrete.

[0003] In view of the above engineering problems, it is necessary to add water reducing agent to the concrete at the same time, and to add workability adjusting agent to adjust the workability of the concrete. Common concrete workability adjusting agents are cellulose ethers, gelatin, xanthan gum and polyacrylamide, etc. natural or synthetic ultra-high molecular weight compounds. Such compounds have obvious water absorption and water retention effect, which can avoid the andeity problems such as bleeding or bleeding of concrete, but there are compatibility, slurry viscosity and other problems between such andeity adjusting agents and water reducing agents, which need to use complex technical means to meet the requirements of transportation, storage and application. In order to solve the adverse effects of concrete hydration heat on concrete, engineering concrete generally adds hydration heat regulating materials based on degraded starch or uses cooling water pipes for physical cooling, and the addition of hydration heat regulating materials is more simple and effective. By chemical grafting or physical compounding of concrete hydration heat regulating materials and water reducing agent, the cement hydration process is adjusted while reducing water, the hydration heat release rate is reduced, and the temperature cracking is reduced. Common hydration heat regulating materials include starch dextrin polymers, inorganic salts and endothermic phase change materials. Dextrin, protein and other materials form a stable solvation water film around the cement particle surface by associating with water molecules, which hinders the cement hydration reaction. The physical reaction or chemical reaction of inorganic salt hydration temperature rise inhibitor with water is an endothermic reaction, which can absorb a large amount of heat released by cement hydration and inhibit cement hydration.

[0004] Starch molecules are polymerized from deoxyglucose units, and the glycosidic bond and hydroxyl group in the molecular structure are relatively active in chemical properties, and are prone to react with various functional groups (oxidation, esterification, etherification, alkylation, crosslinking, etc.), and have multifunctionality and molecular designability. The molecular chain structure has amphiphilicity, that is, the hydrophobicity of the hydrophobic chain and the hydrophilicity of the hydroxyl group (-OH) on the starch molecular chain, and the polyhydroxyl structure of the starch can also impart the starch water-reducing agent excellent water retention, which is beneficial to improve the wrapping and cohesive properties of the cement paste in the concrete mixture to the aggregate, improve the problems of bleeding, layering and segregation, and the starch, as the second largest natural polymer on earth, is cheap and easy to obtain, has the advantages of being renewable, widely sourced, large in yield, non-toxic and low in price, meets the green requirements of chemical raw material sources, and also meets the sustainable development concept.

[0005] Based on the molecular structure and action mechanism, the starch macromolecular structure and its hydrophilicity play a large steric hindrance effect to achieve high water reduction, and the polyhydroxyl structure has a strong complexation effect with the cations in the cement paste, which can control the hydration process and thus control the hydration heat temperature peak, solve the cracks caused by temperature difference in large volume, and thus improve the durability of concrete. Therefore, how to construct a polycarboxylic admixture based on starch or its derivative cyclodextrin is an important topic. SUMMARY

[0006] In view of the poor workability of concrete, the rapid internal temperature rise of concrete caused by hydration heat and the cracks generated thereby, the present application provides a functional cyclodextrin polyether macromonomer, a preparation method and application thereof. The functional cyclodextrin polyether macromonomer can be applied to a polycarboxylic admixture, effectively improving the workability of concrete under the current concrete raw material system, and can effectively control the hydration heat and reduce the generation of temperature cracks for high water-binder ratio or large volume concrete.

[0007] In order to achieve the above purpose, the present application provides a preparation method of a functional cyclodextrin polyether macromonomer, which reacts conventional cyclodextrin with alkyne polyethylene glycol siloxane to prepare alkyne cyclodextrin, reacts propenyl chloride or methacryl chloride with sodium azide to prepare an azide-containing compound, and then prepares the functional polyether macromonomer by click chemistry. Specifically, the following steps are included: S1, reacting cyclodextrin, alkyne polyethylene glycol siloxane and a catalyst in a polar aprotic solvent at 25-100 DEG C for 3-24 h to occur one-step condensation reaction, removing the by-product small molecule alcohol, i.e. ethanol or methanol, by vacuum, to prepare the intermediate alkyne cyclodextrin; S2, the allyl chloride compound and inorganic azide compound are reacted at 25-75°C for 3-5h to produce a nucleophilic substitution reaction, after the reaction, the product is extracted by a non-polar solvent (cyclohexane, etc.), the organic layer is washed with water, separated and concentrated and dried under vacuum (room temperature) to produce the allyl azide compound; S3, the alkynyl cyclodextrin obtained in step S1, the allyl azide compound obtained in step S2, a catalyst and a surfactant are reacted at 25-75°C for 3-5h to produce the functional cyclodextrin polyether macromonomer.

[0008] The alkynyl polyoxyethylene glycol siloxane is an industrial product, and has the following structure: a silane group (Silane, triethoxysilane-Si(OC2H5)3) or trimethoxysilane (-Si(OCH3)3), a polyethylene glycol (PEG, length adjustable, generally with a molecular weight of 200-4000) and an alkyne group (Alkyne, -C≡C), the three groups are connected by a covalent bond, wherein the polyethylene glycol is a connecting group, the silane group and the alkyne group are at both ends, and the middle contains an ether bond, a siloxane bond, an ester bond or an amide bond, and the overall molecular weight is 1000-5000.

[0009] Preferably, in step S1, the cyclodextrin is α-cyclodextrin, β-cyclodextrin or γ-cyclodextrin, the catalyst is p-toluenesulfonic acid, acrylic acid, acetic acid or a Lewis acid, the polar aprotic solvent is N,N-dimethylformamide, diethylene glycol dimethyl ether or diethylene glycol methyl ethyl ether, the molar ratio of the cyclodextrin and the alkynyl polyethylene glycol siloxane is 1.0: (1.0-1.5), and the amount of the catalyst is 0.1%-0.8% of the total mass of the cyclodextrin and the alkynyl polyethylene glycol siloxane.

[0010] Preferably, in step S2, the allyl chloride compound is allyl chloride or methyl allyl chloride, and the inorganic azide compound is sodium azide, and the molar ratio of the allyl chloride compound and the inorganic azide compound is 1.0: (1.0-2.0).

[0011] Preferably, in step S3, the catalyst is cuprous iodide, the surfactant is one or a mixture of two or more of tetrabutylammonium bromide, dodecyltrimethylammonium bromide, benzyltriethylammonium chloride and cocotrimethylammonium chloride, the molar ratio of the alkynyl cyclodextrin and the allyl azide compound is 1.0: (1.0-1.2), the molar amount of the catalyst is 0.1%-0.6% of the total molar amount of the alkynyl cyclodextrin and the allyl azide compound, and the molar amount of the surfactant is 0.1%-1.0% of the total molar amount of the alkynyl cyclodextrin and the allyl azide compound.

[0012] The second aspect of the present invention provides a functional cyclodextrin polyether macromonomer prepared by the above-described preparation method.

[0013] The third aspect of the present invention provides a method for preparing a polycarboxylic acid admixture, comprising the following steps: mixing the polyether macromonomer, oxidant and solvent as described in claim 5, and simultaneously adding an unsaturated organic acid containing anchoring groups, a chain transfer agent and a reducing agent at 40-55ºC, completing the addition within 2.5 hours, and continuing the reaction for 1-1.5 hours after the addition is completed to obtain the polycarboxylic acid admixture.

[0014] The linker arm of the polycarboxylic acid admixture is an alkynyl polyethylene glycol siloxane, in which the alkynyl group undergoes a click chemical reaction with the main chain containing an azide group to form 1,4-disubstituted (trans)-1,2,3-triazole, the siloxane group undergoes a condensation reaction with cyclodextrin to form the main chain, and then the functional polyether macromonomer grafted with cyclodextrin undergoes a free radical polymerization reaction with acrylic acid or methacrylic acid to form the main chain.

[0015] Preferably, the unsaturated organic acid containing the anchoring group is one or more of acrylic acid, methacrylic acid, maleic acid, itaconic acid, acrylamide, and 2-acrylamido-2-methylpropanesulfonic acid (AMPS); The oxidant is hydrogen peroxide, ammonium persulfate, potassium persulfate, or sodium persulfate; The reducing agent is ascorbic acid, sodium formaldehyde sulfoxylate, ferrous sulfate, or sodium bisulfite; The chain transfer agent is mercaptopropionic acid, mercaptoacetic acid, mercaptoethanol, or sodium hypophosphite.

[0016] Specifically, the molar ratio of the polyether macromonomer, the oxidant (an unsaturated organic acid with anchoring groups), the chain transfer agent, and the reducing agent is 1:(0.3-0.4):(3-5):(1-1.5):(0.15-0.2).

[0017] The fourth aspect of the present invention provides a polycarboxylate admixture prepared by the above-described preparation method, the structural formula of which is shown in formula (1), formula (2) or formula (3): (1), (2), (3), Wherein, molecular weight = 20000~80000, x is 3~60, y is 9~300, the molar ratio of x to y is 1.0:(3.0~5.0), and n is 20~100; R1 is CH3 or H, R2 is CH3, H, COOH or CH2COOH, and R3 is CH3 or CH2CH3.

[0018] This invention uses cyclodextrin, derived from biological sources, as the key raw material. It involves a condensation reaction with alkynyl polyethylene glycol silane, followed by a one-step classic click chemistry reaction with an allyl azide compound to prepare a key functional polyether macromonomer. This macromonomer then undergoes free radical polymerization with an organic acid containing anchoring groups under the action of oxidants, reducing agents, and chain transfer agents to obtain a cyclodextrin-based polycarboxylic acid admixture. Due to its strong steric hindrance, it enhances the water-reducing capacity of polycarboxylic acid. The polyhydroxyl-containing cyclodextrin structure has a retarding effect on cement-based concrete, reducing the hydration heat peak. Furthermore, the hydrophobic internal cavity of cyclodextrin enhances the air-entraining and foam-stabilizing ability of the polycarboxylic acid admixture molecules, improving the workability of low to medium water-cement ratio concrete, inhibiting bleeding and slurry seepage, resulting in concrete exhibiting high slurry content, high water retention, and high workability, demonstrating excellent application prospects.

[0019] The fifth aspect of the present invention provides the application of the above-mentioned polycarboxylate admixture in the preparation of concrete materials, wherein the admixture is added at a dosage of 0.05% to 0.5% of the total weight of cementitious materials, preferably 0.1% to 0.4%. If the dosage is too low, the initial dispersion effect on low water-cement ratio concrete will not be satisfactory. If the dosage is too high, it will delay the setting time, affect the strength, and also cause economic waste.

[0020] Through the above technical solution, the present invention achieves the following beneficial effects: This invention is the first to utilize click chemistry to efficiently prepare a novel functional cyclodextrin polyether macromonomer. Based on this polyether macromonomer, a polycarboxylate admixture was prepared. This admixture combines the functions of water reduction, setting retardation, and temperature peak reduction. The polycarboxylate admixture effectively improves the workability and slump retention of concrete under current concrete raw material systems. For high water-cement ratio or large-volume concrete, it can effectively control hydration heat release, suppress the hydration heat release temperature peak, reduce the internal temperature rise of concrete, and reduce the generation of temperature cracks. Detailed Implementation

[0021] The specific embodiments of the present invention will be described in detail below with reference to examples. It should be understood that the specific embodiments described herein are for illustration and explanation only and are not intended to limit the present invention.

[0022] In this embodiment of the invention, the molecular weight of all condensation polymers was determined using aqueous gel permeation chromatography (GPC) under the following experimental conditions: Gel column: Two Shodex SB806+803 columns connected in series; Mobile phase: 0.1M NaNO3 aqueous solution; Mobile phase rate: 1.01 ml / min; Injection: 20 μl of 0.5% aqueous solution; Detector: Shodex RI-71 differential refractive index detector; Standard: Polyethylene glycol GPC standard (Sigma-Aldrich, molecular weight 1,010,000, 478,000, 263,000, 118,000, 44,700, 18,600, 6,690, 1,960, 628, 232).

[0023] Example 1 (1) Methods for preparing functional cyclodextrin-based polyether macromonomers include: S1. In a three-necked flask heated in a constant temperature water bath, add 1 mol of α-cyclodextrin, 1.1 mol of 2000 molecular weight alkynyl polyethylene glycol siloxane, 4.5 mol of polar aprotic solvent N,N-dimethylformamide (DMF), and 2.0 g of catalyst p-toluenesulfonic acid in sequence. React at 100ºC for 3 h. During the reaction, remove the byproduct methanol or ethanol under vacuum. After the reaction is complete, cool down to obtain the intermediate alkynyl cyclodextrin. S2. In a three-necked flask heated in a constant temperature water bath, 2 mol of methylallyl chloride, 2.4 mol of sodium azide, and 6.0 mol of the polar aprotic solvent N,N-dimethylformamide (DMF) were added sequentially. The temperature was raised to 45°C and the reaction was maintained at this temperature for 4 hours. After the reaction was completed, a certain amount of water was added, and the mixture was extracted three times with cyclohexane. The cyclohexane solution containing the product was concentrated in a rotary evaporator under controlled vacuum and in a water bath at room temperature, with the water temperature not exceeding 40°C, to obtain the intermediate methylallyl azide compound. S3. To a three-necked flask heated in a constant-temperature water bath, 1.1 mol of methyl allyl azide, 1.0 mol of alkynyl cyclodextrin, 0.0042 mol of cuprous iodide catalyst, and 0.0084 mol of tetrabutylammonium bromide surfactant were added sequentially. Water was added in an amount equal to 0.67 times the mass of the materials. The temperature was raised to 35ºC and the reaction was maintained at this temperature for 4 hours. After cooling, the functional cyclodextrin polyether macromonomer was obtained. The yield and molecular weight of this functional cyclodextrin polyether macromonomer were tested, and the yield reached 90%, with a weight-average molecular weight Mw≈3000.

[0024] (2) Preparation of polycarboxylic acid admixtures using functional cyclodextrin-based polyether macromonomers, including: In a four-necked flask heated in a constant-temperature water bath, 1.0 mol of functional cyclodextrin polyether macromonomer, 0.32 mol of hydrogen peroxide, and 0.1 times the mass of water equal to the macromonomer were added sequentially. The mixture was stirred at 50ºC. Dropping solution A was prepared by adding 4 mol of acrylic acid and an equal mass of water; dropping solution B was prepared by dissolving 1.2 mol of mercaptopropionic acid in water to a 5 wt% aqueous solution; and dropping solution C was prepared by dissolving 0.2 mol of ascorbic acid in water to a 2 wt% aqueous solution. All three dropping solutions were added simultaneously, and the reaction was allowed to proceed for 2 hours. After the addition was complete, the reaction was allowed to continue for another hour. Once the reaction was complete, 32.5% liquid alkali was added to adjust the pH to 7, thus obtaining the polycarboxylate additive. The molecular weight of this polycarboxylate additive was determined, and the weight-average molecular weight Mw ≈ 31000.

[0025] Example 2 (1) Methods for preparing functional cyclodextrin-based polyether macromonomers include: S1. Add 1 mol of β-cyclodextrin, 1.2 mol of 3000 molecular weight alkynyl polyethylene glycol siloxane, 4.8 mol of polar aprotic solvent N,N-dimethylformamide (DMF), and 2.4 g of catalyst p-toluenesulfonic acid to a three-necked flask heated in a constant temperature water bath. React at 60ºC for 10 h. Remove the byproduct methanol or ethanol under vacuum during the reaction. After the reaction is complete, cool down to obtain the intermediate alkynyl cyclodextrin. S2. In a three-necked flask heated in a constant temperature water bath, 2 mol of allyl chloride, 2.1 mol of sodium azide, and 5.8 mol of the polar aprotic solvent N,N-dimethylformamide (DMF) were added sequentially. The temperature was raised to 60°C and the reaction was maintained at a constant temperature for 5 hours. After the reaction was completed, a certain amount of water was added, and the mixture was extracted three times with cyclohexane. The cyclohexane solution containing the product was concentrated in a rotary evaporator under controlled vacuum and in a water bath at room temperature, with the water temperature not exceeding 40°C, to obtain the intermediate allyl azide compound. S3. To a three-necked flask heated in a constant-temperature water bath, 1.2 mol of allyl azide compound, 1.0 mol of alkynyl cyclodextrin, 0.0050 mol of cuprous iodide catalyst, and 0.022 mol of dodecyltrimethylammonium bromide surfactant were added sequentially. Water was added in an amount equal to 0.67 times the mass of the materials. The temperature was raised to 25ºC, and the reaction was maintained at this temperature for 5 hours. After cooling, the functional cyclodextrin polyether macromonomer was obtained. The yield and molecular weight of this functional cyclodextrin polyether macromonomer were tested, and the yield reached 92%, with a weight-average molecular weight Mw≈4000.

[0026] (2) Preparation of polycarboxylic acid admixtures using functional cyclodextrin-based polyether macromonomers, including: In a four-necked flask heated in a constant-temperature water bath, 1.0 mol of functional cyclodextrin polyether macromonomer, 0.30 mol of hydrogen peroxide, and 0.1 times the mass of water equal to the macromonomer were added sequentially. The mixture was stirred at 50ºC. Dropping solution A was prepared by adding 3.0 mol of methacrylic acid and an equal mass of water; dropping solution B was prepared by dissolving 1.0 mol of mercaptopropionic acid in water to a 5 wt% aqueous solution; and dropping solution C was prepared by dissolving 0.2 mol of ascorbic acid in water to a 2% aqueous solution. All three dropping solutions were added simultaneously, and the reaction was allowed to proceed for 2 hours. After the additions were complete, the reaction was allowed to continue for another hour. Once the reaction was complete, 32.5% liquid alkali was added to adjust the pH to 7, thus obtaining the polycarboxylate additive. The molecular weight of this polycarboxylate additive was determined, and the weight-average molecular weight Mw ≈ 35000.

[0027] Example 3 (1) Methods for preparing functional cyclodextrin-based polyether macromonomers include: S1. Add 1 mol of γ-cyclodextrin, 1.5 mol of 4000 molecular weight alkynyl polyethylene glycol siloxane, 4.5 mol of polar aprotic solvent N,N-dimethylformamide (DMF), and 2.2 g of catalyst p-toluenesulfonic acid to a three-necked flask heated in a constant temperature water bath. React at 55ºC for 15 h. Remove the byproduct methanol or ethanol under vacuum during the reaction. After the reaction is complete, cool down to obtain the intermediate alkynyl cyclodextrin. S2. In a three-necked flask heated in a constant temperature water bath, 2 mol of methylallyl chloride, 4 mol of sodium azide, and 5.0 mol of the polar aprotic solvent N,N-dimethylformamide (DMF) were added sequentially. The temperature was raised to 75°C and the reaction was maintained at a constant temperature for 3 hours. After the reaction was completed, a certain amount of water was added, and the mixture was extracted three times with cyclohexane. The cyclohexane solution containing the product was concentrated in a rotary evaporator under controlled vacuum and in a water bath at room temperature, with the water temperature not exceeding 40°C, to obtain the intermediate methylallyl azide compound. S3. To a three-necked flask heated in a constant-temperature water bath, 1.15 mol of methyl allyl azide, 1.0 mol of alkynyl cyclodextrin, 0.034 mol of cuprous iodide catalyst, 0.0039 mol of benzyl triethyl ammonium chloride surfactant, and 0.0039 mol of cocoyl trimethyl ammonium chloride were added sequentially. Water was added in an amount equal to 0.67 times the mass of the materials. The temperature was raised to 45ºC and reacted at this temperature for 4.5 h. After cooling, the functional cyclodextrin polyether macromonomer was obtained. The yield and molecular weight of this functional cyclodextrin polyether macromonomer were tested, and the yield reached 88%, with a weight-average molecular weight Mw≈5000.

[0028] (2) Preparation of polycarboxylic acid admixtures using functional cyclodextrin-based polyether macromonomers, including: In a four-necked flask heated in a constant-temperature water bath, 1.0 mol of functional cyclodextrin polyether macromonomer, 0.32 mol of hydrogen peroxide, and 0.1 times the mass of water equal to the macromonomer were added sequentially. The mixture was stirred at 50ºC. Dropping solution A was prepared by adding 4.5 mol of maleic acid and an equal mass of water; dropping solution B was prepared by adding 1.2 mol of mercaptopropionic acid to a 5 wt% aqueous solution; and dropping solution C was prepared by adding 0.15 mol of ascorbic acid to a 2% aqueous solution. All three dropping solutions were added simultaneously, and the reaction was allowed to proceed for 2 hours. After the additions were complete, the reaction was allowed to continue for another hour. Once the reaction was complete, 32.5% liquid alkali was added to adjust the pH to 7, thus obtaining the polycarboxylate additive. The molecular weight of this polycarboxylate additive was determined, and the weight-average molecular weight Mw ≈ 60,000.

[0029] Example 4 (1) Methods for preparing functional cyclodextrin-based polyether macromonomers include: S1. Add 1 mol of β-cyclodextrin, 1.2 mol of 2000 molecular weight alkynyl polyethylene glycol siloxane, 4.4 mol of polar aprotic solvent N,N-dimethylformamide (DMF), and 2.1 g of catalyst acrylic acid to a three-necked flask heated in a constant temperature water bath. React at 65°C for 20 h. Remove the byproduct methanol or ethanol under vacuum during the reaction. After the reaction is complete, cool down to obtain the intermediate alkynyl cyclodextrin. S2. In a three-necked flask heated in a constant temperature water bath, 2 mol of allyl chloride, 2.16 mol of sodium azide, and 4.8 mol of the polar aprotic solvent N,N-dimethylformamide (DMF) were added sequentially. The temperature was raised to 40°C and the reaction was maintained at this temperature for 2.5 h. After the reaction was completed, a certain amount of water was added, and the mixture was extracted three times with cyclohexane. The cyclohexane solution containing the product was concentrated in a rotary evaporator under controlled vacuum and in a water bath at room temperature, with the water temperature not exceeding 40°C, to obtain the intermediate allyl azide compound. S3. To a three-necked flask heated in a constant-temperature water bath, 1.10 mol of allyl azide compound, 1.0 mol of alkynyl cyclodextrin, 0.0036 mol of cuprous iodide catalyst, and 0.0058 mol of tetrabutylammonium bromide surfactant were added sequentially. Water was added in an amount equal to 0.67 times the mass of the materials. The temperature was raised to 45ºC, and the reaction was maintained at this temperature for 3.5 h. After cooling, the functional cyclodextrin polyether macromonomer was obtained. The yield and molecular weight of this functional cyclodextrin polyether macromonomer were tested, and the yield reached 94%, with a weight-average molecular weight Mw≈3200.

[0030] (2) Preparation of polycarboxylic acid admixtures using functional cyclodextrin-based polyether macromonomers, including: In a four-necked flask heated in a constant-temperature water bath, 1.0 mol of functional cyclodextrin polyether macromonomer, 0.36 mol of ammonium persulfate, and 0.1 times the mass of the polyether macromonomer in water were added sequentially. The mixture was stirred at 45ºC to prepare dropwise solution A: 5 mol of itaconic acid and an equal mass of water; dropwise solution B: 1.4 mol of mercaptoacetic acid, diluted with water to a 5 wt% aqueous solution; and dropwise solution C: 0.20 mol of sodium formaldehyde sulfoxylate, diluted with water to a 2% aqueous solution. All three dropwise solutions were added simultaneously, and the reaction was allowed to proceed for 2 hours. After the additions were complete, the reaction was allowed to continue for another hour. Once the reaction was complete, 32.5% liquid alkali was added to adjust the pH to 7, thus obtaining the polycarboxylate additive. The molecular weight of this polycarboxylate additive was determined, and the weight-average molecular weight Mw ≈ 50,000.

[0031] Example 5 (1) Methods for preparing functional cyclodextrin-based polyether macromonomers include: S1. Add 1 mol of γ-cyclodextrin, 1.18 mol of 1000 molecular weight alkynyl polyethylene glycol siloxane, 4.0 mol of polar aprotic solvent N,N-dimethylformamide (DMF), and 1.8 g of catalyst acetic acid to a three-necked flask heated in a constant temperature water bath. React at 25ºC for 24 h. Remove the byproduct methanol or ethanol under vacuum during the reaction. After the reaction is complete, cool down to obtain the intermediate alkynyl cyclodextrin. S2. In a three-necked flask heated in a constant temperature water bath, 2 mol of methylallyl chloride, 2.18 mol of sodium azide, and 4.5 mol of the polar aprotic solvent N,N-dimethylformamide (DMF) were added sequentially. The temperature was raised to 45°C and the reaction was maintained at this temperature for 3.0 h. After the reaction was completed, a certain amount of water was added, and the mixture was extracted three times with cyclohexane. The cyclohexane solution containing the product was concentrated in a rotary evaporator under controlled vacuum and in a water bath at room temperature, with the water temperature not exceeding 40°C, to obtain the intermediate methylallyl azide compound. S3. To a three-necked flask heated in a constant-temperature water bath, 1.08 mol of methyl allyl azide compound, 1.0 mol of alkynyl cyclodextrin, 0.00208 mol of cuprous iodide catalyst, and 0.0040 mol of tetrabutylammonium bromide surfactant were added sequentially. Water was added in an amount equal to 0.67 times the mass of the materials. The temperature was raised to 75°C and reacted at this temperature for 3 hours. The mixture was then cooled to obtain a functional cyclodextrin polyether macromonomer. The yield and molecular weight of this functional cyclodextrin polyether macromonomer were tested, and the yield reached 90%, with a weight-average molecular weight Mw ≈ 2400.

[0032] (2) Preparation of polycarboxylic acid admixtures using functional cyclodextrin-based polyether macromonomers, including: In a four-necked flask heated in a constant-temperature water bath, 1.0 mol of functional cyclodextrin polyether macromonomer, 0.4 mol of potassium persulfate, and 0.1 times the mass of the polyether macromonomer in water were added sequentially. The mixture was stirred at 55ºC to prepare dropping solution A: 4.4 mol of acrylamide and an equal mass of water; dropping solution B: 1.2 mol of mercaptoethanol, diluted with water to a 5 wt% aqueous solution; and dropping solution C: 0.18 mol of ferrous sulfate, diluted with water to a 2% aqueous solution. All three dropping solutions were added simultaneously, and the reaction was allowed to proceed for 2 hours. After the additions were complete, the reaction was allowed to continue for another hour. Once the reaction was complete, 32.5% liquid alkali was added to adjust the pH to 7, thus obtaining the polycarboxylate additive. The molecular weight of this polycarboxylate additive was determined to be approximately 26000 (weight average molecular weight Mw).

[0033] Example 6 (1) Methods for preparing functional cyclodextrin-based polyether macromonomers include: S1. In a three-necked flask heated in a constant temperature water bath, add 1 mol of α-cyclodextrin, 1.0 mol of 2000 molecular weight alkynyl polyethylene glycol siloxane, 3.6 mol of polar aprotic solvent N,N-dimethylformamide (DMF), and 1.6 g of Lewis acid catalyst. React at 50ºC for 24 h. During the reaction, remove the byproduct methanol or ethanol under vacuum. After the reaction is complete, cool down to obtain the intermediate alkynyl cyclodextrin. S2. In a three-necked flask heated in a constant temperature water bath, 2 mol of methylallyl chloride, 2.06 mol of sodium azide, and 4.0 mol of the polar aprotic solvent N,N-dimethylformamide (DMF) were added sequentially. The temperature was raised to 25°C and the reaction was maintained at this temperature for 5.0 h. After the reaction was completed, a certain amount of water was added, and the mixture was extracted three times with cyclohexane. The cyclohexane solution containing the product was concentrated in a rotary evaporator under controlled vacuum and in a water bath at room temperature, with the water temperature not exceeding 40°C, to obtain the intermediate methylallyl azide compound. S3. To a three-necked flask heated in a constant-temperature water bath, 1.0 mol of methyl allyl azide compound, 1.0 mol of alkynyl cyclodextrin, 0.0034 mol of cuprous iodide catalyst, and 0.002 mol of tetrabutylammonium bromide surfactant were added sequentially. Water was added in an amount equal to 0.67 times the mass of the materials. The temperature was raised to 50ºC, and the reaction was maintained at this temperature for 4.0 h. After cooling, the functional cyclodextrin polyether macromonomer was obtained. The yield and molecular weight of this functional cyclodextrin polyether macromonomer were tested, and the yield reached 92%, with a weight-average molecular weight Mw≈3100.

[0034] (2) Preparation of polycarboxylic acid admixtures using functional cyclodextrin-based polyether macromonomers, including: In a four-necked flask heated in a constant-temperature water bath, 1.0 mol of functional cyclodextrin polyether macromonomer, 0.32 mol of sodium persulfate, and 0.1 times the mass of the polyether macromonomer in water were added sequentially. The mixture was stirred at 55ºC. Dropping solution A was prepared by adding 4.0 mol of 2-acrylamido-2-methylpropanesulfonic acid and an equal mass of water; dropping solution B was prepared by dissolving 1.5 mol of sodium hypophosphite in water to a 5 wt% aqueous solution; and dropping solution C was prepared by dissolving 0.19 mol of sodium bisulfite in water to a 2% aqueous solution. All three dropping solutions were added simultaneously, and the reaction was allowed to proceed for 2.5 hours. After the addition was complete, the reaction was allowed to continue for another 1.5 hours. Once the reaction was complete, 32.5% liquid alkali was added to adjust the pH to 7, thus obtaining the polycarboxylate additive. The molecular weight of this polycarboxylate additive was determined, and the weight-average molecular weight Mw ≈ 38000.

[0035] Comparative Example 1 Traditional ether-type polycarboxylic acid: 480g (0.2mol) of isopentenyl polyoxyethylene ether (Mw=2400) and 61g of water were mixed in a 1000mL three-necked flask and heated to 65℃. At the same time, 42.5g (70% concentration, 0.5mol) of methacrylic acid solution, 30.6g (30% concentration) of ammonium persulfate solution, and 10.3g of mercaptoacetic acid were slowly added dropwise over 2 hours. After the addition was completed, the reaction was continued for 3 hours to obtain the ether-type polycarboxylic acid mother liquor, which was a colorless and transparent solution. The monomer conversion rate was tested to be 88%, and the weight average molecular weight of the ether-type polycarboxylic acid was 36,000.

[0036] Comparative Example 2 Traditional ester-type polycarboxylic acid: 240g (0.2mol) of ester-type polyether macromonomer (Mw=1200) and 60g of water were mixed in a 1000mL three-necked flask and heated to 65℃. At the same time, 41.8g of acrylic acid solution (70% concentration, 0.5mol), 30.0g of ammonium persulfate solution (30% concentration), and 9.8g of mercaptoacetic acid were slowly added dropwise over 2 hours. After the addition was completed, the reaction was continued for 3 hours to obtain a colorless and transparent mother liquor of ester-type polycarboxylic acid. The monomer conversion rate was tested to be 90%, and the weight-average molecular weight of ester-type polycarboxylic acid was 32000.

[0037] Application performance testing The performance of the polycarboxylic acid admixture based on functional cyclodextrin polyether macromonomer prepared in this invention in concrete systems was tested, and the performance of the synthesized examples was compared with that of conventional ether-type or ester-type polycarboxylic acids.

[0038] The concrete mix used was Onoda 52.5RPII cement, medium sand with a fineness modulus of Mx=2.6, and continuously graded crushed stone with a particle size of 5-25mm. The concrete mix proportions were: cement 6.6kg, fly ash 1.6kg, sand 14.8kg, large aggregate 15.0kg, small aggregate 6.4kg, water 3.2kg, and the same dosage of 0.18% water-reducing agent. No other additives were added. The testing standards were in accordance with GB / T 8076-2008 "Concrete Admixtures".

[0039] The specific test results are as follows:

[0040] As shown in the table above, the polycarboxylate additive prepared by the functional cyclodextrin polyether macromonomer of this invention exhibits good water-reducing ability and excellent workability. It can effectively control the exothermic reaction of hydration and suppress the exothermic temperature peak. Traditional ether-type polycarboxylate shows the best water-reducing ability, but its workability is poor. Traditional ester-type polycarboxylate has weak water-reducing ability, but its workability is better. This is because cyclodextrin provides large volume steric hindrance, long side-chain polyethylene glycol connecting units enhance water-reducing ability, hydrophobic cavities have air-entraining and foam-stabilizing capabilities, improving workability, high acid-ether ratio, and the amide or ester groups in the side chains and the polyhydroxy structure in cyclodextrin can complex alkaline earth metal ions in cement concrete systems, regulate the hydration process, and reduce the peak temperature. Traditional ether-type polycarboxylic acids exhibit the best water-reducing ability due to their high molecular structure regularity and side chain length of up to 2400, but have poor workability. Traditional ester-type polycarboxylic acids, due to monomer preparation limitations, have a side chain length of only 1200, resulting in weaker water reduction but acceptable workability.

[0041] The polycarboxylate admixture prepared in this invention not only exhibits excellent workability, reducing bleeding, grouting, and bottoming phenomena in concrete under current material systems, but also significantly reduces the peak temperature due to the retarding effect of the polyhydroxy cyclodextrin structure. The peak temperature reduction rate is significantly improved compared with traditional ether-type or ester-type polycarboxylate admixtures, indicating that it is particularly suitable for large-volume, thin-walled concrete structures. It has a significant effect on reducing the peak temperature and inhibiting concrete cracks caused by temperature differences. Therefore, the polycarboxylate admixture prepared in this invention has potential application prospects for concrete with poor workability in medium and low water-cement ratios and for large-volume concrete with concentrated heat release during hydration leading to large internal and external temperature differences. It is of great significance for improving the construction performance of ready-mixed concrete, inhibiting temperature difference cracks, and improving concrete durability.

[0042] The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited to the specific details in the above embodiments. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solution of the present invention, and these simple modifications all fall within the protection scope of the present invention.

[0043] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, the present invention will not describe the various possible combinations separately.

[0044] Furthermore, various different embodiments of the present invention can be combined in any way, as long as they do not violate the spirit of the present invention, they should also be regarded as the content disclosed by the present invention.

Claims

1. A method for preparing a functional cyclodextrin polyether macromonomer, characterized in that, Includes the following steps: S1. Cyclodextrin, alkynyl polyethylene glycol siloxane and catalyst are reacted in a polar aprotic solvent at 25-100℃ for 3-24 h to obtain the intermediate alkynyl cyclodextrin. S2. Allyl chloride compound and inorganic azide compound are reacted at 25-75°C for 3-5 hours to obtain allyl azide compound; S3. The alkynyl cyclodextrin obtained in step S1, the allyl azide compound obtained in step S2, the catalyst and the surfactant are reacted at 25-75°C for 3-5 hours to obtain the functional cyclodextrin polyether macromonomer.

2. The preparation method according to claim 1, characterized in that, In step S1, the cyclodextrin is α-cyclodextrin, β-cyclodextrin, or γ-cyclodextrin; the catalyst is p-toluenesulfonic acid, acrylic acid, acetic acid, or a Lewis acid; the polar aprotic solvent is N,N-dimethylformamide, diethylene glycol dimethyl ether, or diethylene glycol methyl ethyl ether; the molar ratio of the cyclodextrin to the alkynyl polyethylene glycol siloxane is 1.0:(1.0–1.5); and the amount of catalyst used is 0.1%–0.8% of the total mass of the cyclodextrin and the alkynyl polyethylene glycol siloxane.

3. The preparation method according to claim 1, characterized in that, In step S2, the allyl chloride compound is allyl chloride or methyl allyl chloride, the inorganic azide compound is sodium azide, and the molar ratio of the allyl chloride compound to sodium azide is 1.0:(1.0~2.0).

4. The preparation method according to claim 1, characterized in that, In step S3, the catalyst is cuprous iodide, the surfactant is one or a mixture of two or more of tetrabutylammonium bromide, dodecyltrimethylammonium bromide, benzyltriethylammonium chloride, and cocoyltrimethylammonium chloride, the molar ratio of alkynylcyclodextrin to allyl azido group is 1.0:(1.0-1.2), the molar amount of the catalyst is 0.1% to 0.6% of the total molar amount of alkynylcyclodextrin and allyl azido group, and the molar amount of the surfactant is 0.1% to 1.0% of the total molar amount of alkynylcyclodextrin and allyl azido group.

5. The functional cyclodextrin polyether macromonomer prepared by any one of claims 1 to 4.

6. A method for preparing a polycarboxylate additive, characterized in that, The process includes the following steps: mixing the polyether macromonomer, oxidant, and solvent as described in claim 5, and simultaneously adding an unsaturated organic acid containing anchoring groups, a chain transfer agent, and a reducing agent at 40–55ºC. The addition is completed within 2.5 hours, and the reaction continues for 1–1.5 hours after the addition is completed to obtain a polycarboxylic acid additive.

7. The preparation method according to claim 6, characterized in that, The unsaturated organic acid containing the anchoring group is one or more of acrylic acid, methacrylic acid, maleic acid, itaconic acid, acrylamide, and 2-acrylamido-2-methylpropanesulfonic acid; The oxidant is hydrogen peroxide, ammonium persulfate, potassium persulfate, or sodium persulfate; The reducing agent is ascorbic acid, sodium formaldehyde sulfoxylate, ferrous sulfate, or sodium bisulfite; The chain transfer agent is mercaptopropionic acid, mercaptoacetic acid, mercaptoethanol, or sodium hypophosphite.

8. The preparation method according to claim 6, characterized in that, The molar ratio of the polyether macromonomer, the oxidant (an unsaturated organic acid with anchoring groups), the chain transfer agent, and the reducing agent is 1:(0.3-0.4):(3-5):(1-1.5):(0.15-0.2).

9. The polycarboxylate additive prepared by the method according to any one of claims 6 to 9, characterized in that, The structural formulas are shown in equation (1), equation (2), or equation (3): （1）， （2）， （3）， Wherein, molecular weight = 20000~80000, x is 3~60, y is 9~300, the molar ratio of x to y is 1.0:(3.0~5.0), and n is 20~100; R1 is CH3 or H, R2 is CH3, H, COOH or CH2COOH, and R3 is CH3 or CH2CH3.

10. The application of the polycarboxylate admixture according to claim 9 in the preparation of concrete materials, characterized in that, The amount of the admixture is 0.05% to 0.5% of the total weight of the cementitious material.

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