Star-shaped temperature-sensitive photoinitiator, star-shaped branched viscosity-reducing type polycarboxylic acid water reducing agent and preparation method and application of star-shaped temperature-sensitive photoinitiator

Abstract

The invention discloses a star-shaped thermo-sensitive initiator, a star-shaped branched viscosity reduction type polycarboxylic acid water reducing agent and a preparation method and application of the star-shaped thermo-sensitive initiator and the star-shaped branched viscosity reduction type polycarboxylic acid water reducing agent. Firstly, a phytic acid-based initiator PA-Br6 is used for synthesizing a star-shaped thermo-sensitive photoinitiator, and a'thermo-sensitive polymer 'design concept is introduced into a concrete admixture molecular structure design; an unsaturated monomer and a polyether macromonomer are used as raw materials, under the condition of a temperature-sensitive macromolecular photoinitiator, a molecular weight regulator and deionized water are added, and the novel star-branched viscosity reduction type polycarboxylic acid water reducer with hydration thermal response is prepared through a photo-initiation polymerization reaction. The viscosity of a pore solution of the cement paste can be reduced, and rapid flowing is realized; meanwhile, a long hydrophobic chain on the arm and a phytic acid core containing six phosphate groups can provide relatively large steric hindrance for cement particles, so that the cement particles are uniformly dispersed and release a large amount of wrapped flocculated water, the viscosity is further reduced, and the fluidity and mechanical properties of cement paste are improved.

Description

Technical Field

[0001] The invention belongs to the technical field of building materials, and specifically relates to a star-shaped temperature-sensitive photoinitiator, a star-shaped branched viscosity-reducing polycarboxylate water-reducing agent, and a preparation method and application thereof. Background Art

[0002] With the increase of infrastructure construction in my country, high-grade concrete has become a necessity for high-rise buildings, prestressed structures, large-span roofs and buildings under special environments. High-grade concrete not only requires hardened concrete to have excellent compressive strength and good durability, but also requires fresh concrete to have good workability and pumpability. In order to meet these requirements, a lower water-cement ratio and a larger gel material are often used, but this will cause the fresh concrete to have a higher viscosity and a too slow flow rate, resulting in increased construction difficulty and frequent engineering construction. High viscosity has become a "stumbling block" on the road to the development of high-grade concrete.

[0003] Polymer viscosity reducers have rich branched structures and excellent adsorption properties, which make the polymer have a high adsorption density and a thick adsorption layer on the surface of cement particles. They can significantly reduce the yield stress and have a lubricating effect, thereby reducing the viscosity of concrete. Therefore, adding polymer viscosity reducers is the most effective way to solve the problems of high viscosity and slow flow rate of high-grade concrete in actual applications.

[0004] At present, the research on concrete viscosity reducers is mostly focused on the traditional comb-shaped viscosity-reducing polycarboxylic acid water-reducing agent, which has a single molecular structure and an unsatisfactory viscosity-reducing effect. There are still gaps and deficiencies in solving the workability problems of high-grade concrete such as fluidity and stability. Compared with traditional comb-shaped polymers, star-shaped polymers have the characteristics of high solubility, low crystallinity, small fluid mechanics volume, high-density functional group distribution, and easy surface modification and modification. They have shown advantages and application prospects that surpass linear polymers in the fields of medicine, rubber, petroleum industry, sewage treatment, etc. Another most notable feature of star-shaped polymers is that the viscosity of the bulk and solution is relatively low. Taking advantage of this, they have been used as rheological property improvers in coatings, oil and gas field mining, concrete, etc.

[0005] Previous related studies have found that the molecular structure of star-branched viscosity reducers has a small hydrodynamic radius, a thick adsorption layer, and low pore solution viscosity, which can effectively reduce the pore solution viscosity of cement paste and achieve rapid flow; temperature-sensitive viscosity adjusters can form a network structure in cement paste through hydration heat stimulation to achieve thixotropic stability. Therefore, innovating molecular structure design and optimizing process, and constructing a hydration heat-responsive thixotropic robust star-branched viscosity-reducing polycarboxylate water reducer is of great significance for the promotion and application of environmentally friendly and low-carbon high-grade concrete viscosity reducers. Summary of the invention

[0006] The purpose of this section is to summarize some aspects of embodiments of the present invention and briefly introduce some preferred embodiments. Some simplifications or omissions may be made in this section and the specification abstract and the invention title of this application to avoid blurring the purpose of this section, the specification abstract and the invention title, and such simplifications or omissions cannot be used to limit the scope of the present invention.

[0007] In view of the above problems and / or the problems existing in the prior art, the present invention is proposed.

[0008] Therefore, the object of the present invention is to overcome the deficiencies in the prior art and provide a star-shaped temperature-sensitive photoinitiator.

[0009] In order to solve the above technical problems, the present invention provides the following technical solution:

[0010] a. A repeating unit derived from a phytic acid-based initiator PA-Br6 having a structural formula as shown in formula (I);

[0011]

[0012] b. a repeating unit of a photoinitiated thermosensitive polymer chain connected to the C-Br group of the phytic acid-based initiator PA-Br6 shown in formula (I), having a structure as shown in formula (II), wherein m and n represent the number of repeating units, and m and n are non-zero integers;

[0013]

[0014] c. The photoinitiated thermosensitive polymer chain is obtained by polymerization of 4-acryloylhydroxybenzoic acid benzophenone and N-isopropylacrylamide as monomers and tris(2-dimethylaminoethyl)amine or tris(2-aminoethyl)amine as a ligand, wherein the molar ratio of 4-acryloylhydroxybenzoic acid benzophenone to N-isopropylacrylamide is 2 to 10:100;

[0015] d. The mass ratio of the monomer and ligand in the repeating unit phytic acid-based initiator PA-Br6 compared to the repeating unit photo-initiated thermosensitive polymer chain is 0.15-0.85:25~50:0.05~0.35.

[0016] Another object of the present invention is to provide a method for preparing a star-shaped temperature-sensitive photoinitiator.

[0017] In order to solve the above technical problems, the present invention provides the following technical solutions: comprising:

[0018] The monomer and solvent water are stirred and dissolved, and then a catalyst and a deactivator are added to obtain a mixed reactant I;

[0019] The mixed reactant I is placed in a constant temperature water bath at 15-30° C., an inert gas is passed through to remove oxygen in the reaction system, a ligand is added to react for 10-30 minutes, and then a phytic acid initiator PA-Br6 is added to initiate a polymerization reaction;

[0020] After the polymerization reaction occurs, the reaction is continued for 60 to 240 minutes under closed conditions. The product is passed through a neutral alumina column to remove the catalyst and the deactivator in the reaction system to obtain a filtrate, which is then post-treated to obtain a thermosensitive macromolecular photoinitiator.

[0021] As a preferred embodiment of the star-shaped temperature-sensitive photoinitiator of the present invention, wherein:

[0022] The post-treatment includes rotary evaporating the filtrate with a rotary evaporator, and finally precipitating the concentrated liquid with petroleum ether, and drying the obtained precipitate under vacuum conditions.

[0023] As a preferred embodiment of the star-shaped temperature-sensitive photoinitiator of the present invention, wherein: in the polymerization reaction system, the content of each raw material is, by mass percentage,

[0024] Monomer 25-50%, initiator PA-Br6 0.15-0.85%, catalyst 0.01-0.3%, ligand 0.05-0.35%, deactivator 0.001-0.02%, the balance is water;

[0025] Wherein, the monomers are 4-acryloylhydroxybenzoic acid benzophenone and N-isopropylacrylamide, and the molar ratio of 4-acryloylhydroxybenzoic acid benzophenone to N-isopropylacrylamide is 2 to 10:100;

[0026] The ligand includes one of tris(2-dimethylaminoethyl)amine or tris(2-aminoethyl)amine;

[0027] The catalyst is copper powder, and the deactivator is copper bromide.

[0028] Another object of the present invention is to provide a star-branched viscosity-reducing polycarboxylic acid water-reducing agent.

[0029] In order to solve the above technical problems, the present invention provides the following technical solution:

[0030] i. A repeating unit derived from the star-shaped thermosensitive macromolecular initiator according to claim 1;

[0031] ii. a repeating unit derived from at least one unsaturated monomer, wherein the unsaturated monomer is selected from one of acrylic acid or methacrylic acid;

[0032] iii. a repeating unit derived from at least one polyether macromonomer, wherein the polyether macromonomer is selected from one of allyl polyoxyethylene ether, isobutylene alcohol polyoxyethylene ether or isopentyl polyoxyethylene ether, and has a molecular weight of 1000 to 3000;

[0033] iv. The mass ratio of the repeating unit star-shaped thermosensitive macromolecular initiator to the repeating unit unsaturated monomer and the polyether macromonomer is 2-10:60-80:15-25.

[0034] Another object of the present invention is to provide a method for preparing a star-shaped temperature-sensitive macromolecular initiator.

[0035] In order to solve the above technical problems, the present invention provides the following technical solutions: comprising:

[0036] Unsaturated monomers, polyether macromonomers, thermosensitive macromolecular photoinitiators, molecular weight regulators and deionized water are put into a photoinitiator reactor and dissolved to obtain a transparent mixed solution I;

[0037] The transparent mixed solution is irradiated under a 350W high-pressure mercury lamp to obtain a star-branched polymer viscosity reducer with a hydrothermal response.

[0038] As a preferred embodiment of the star-branched viscosity-reducing polycarboxylate water-reducing agent of the present invention, wherein: in terms of the mass percentage of the mixed solution I, the content of each raw material is:

[0039] The polyether macromonomer is 15-25%, the unsaturated monomer is 60-80%, the temperature-sensitive macromolecular photoinitiator is 2-10%, the molecular weight regulator is 0.01-0.5%, and the balance is water.

[0040] As a preferred embodiment of the star-branched viscosity-reducing polycarboxylic acid water-reducing agent of the present invention, the molecular weight regulator comprises one of mercaptopropionic acid or thioglycolic acid.

[0041] As a preferred embodiment of the star-branched viscosity-reducing polycarboxylic acid water-reducing agent of the present invention, the treatment temperature of the irradiation treatment is 15 to 35° C., and the irradiation time is 2 to 4 hours.

[0042] Another object of the present invention is to provide a star-branched viscosity-reducing polycarboxylate water-reducing agent for use in preparing concrete.

[0043] Beneficial effects of the present invention:

[0044] (1) The present invention introduces the design concept of "thermosensitive polymer" into the molecular structure design of concrete admixtures, utilizes thermosensitive star-shaped macromolecular photoinitiators, and prepares a new type of star-shaped branched viscosity-reducing polycarboxylic acid water-reducing agent with hydration thermal response through a green and environmentally friendly photoinitiator polymer synthesis process, and achieves energy saving and low carbon goals through the whole process system design and control concept.

[0045] (2) The polymer viscosity reducer constructed in the present invention has a star-branched divergent structure. The molecular structure has a small hydrodynamic radius, a thick adsorption layer, and a low pore solution viscosity, which can reduce the pore solution viscosity of the cement slurry and achieve rapid flow; at the same time, the long hydrophobic chain contained in the arm and the phytic acid core containing 6 phosphate groups can provide a large steric hindrance for the cement particles, so that the cement particles are evenly dispersed and a large amount of flocculated water is released, thereby reducing the viscosity and improving the fluidity and mechanical properties of the cement slurry.

[0046] (3) The present invention utilizes the heat release of cement paste hydration to stimulate the thermosensitive polymer arms in the star-branched viscosity-reducing polycarboxylic acid water-reducing agent molecules to undergo hydrophobic association to form a network structure in the cement paste. When the system is subjected to shear force, the formed network structure is destroyed, the system restores fluidity, and the viscosity decreases; when the shear force stops, the system re-forms the network structure through hydrophobic association, and the viscosity increases, thereby achieving synergy between fluidity and stability. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for describing the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative labor. Among them:

[0048] Figure 1 This is a schematic diagram of the structure of the temperature-sensitive star-shaped photoinitiator prepared in Example 1 of the present invention.

[0049] Figure 2 Schematic diagram of the temperature sensitivity of the temperature-sensitive star-shaped photoinitiator prepared in Example 1 of the present invention. DETAILED DESCRIPTION

[0050] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the specific implementation methods of the present invention are described in detail below in conjunction with the embodiments of the specification.

[0051] In the following description, many specific details are set forth to facilitate a full understanding of the present invention, but the present invention may also be implemented in other ways different from those described herein, and those skilled in the art may make similar generalizations without violating the connotation of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0052] Secondly, the term "one embodiment" or "embodiment" as used herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The term "in one embodiment" that appears in different places in this specification does not necessarily refer to the same embodiment, nor does it refer to a separate or selective embodiment that is mutually exclusive with other embodiments.

[0053] Unless otherwise specified, the raw materials used in the present invention are all commercially available in the art.

[0054] The preparation method of the phytic acid-based initiator PA-Br6 shown in formula (I) used in the present invention is as follows:

[0055] Anhydrous phytic acid (33.00 g, 0.05 mol) and 100 mL of N,N-dimethylformamide (DMF) were added into a flask and stirred rapidly to mix evenly. Subsequently, 53 mL of DMF containing 2-bromoisobutyryl bromide (69.00 g, 0.3 mol) was slowly added dropwise into the phytic acid solution. The mixture was stirred in an ice-water bath for 2 h and reacted at room temperature for 24 h. The reaction mixture was precipitated with ether and centrifuged and freeze-dried to obtain a phytic acid-based initiator PA-Br6 having a structural formula as shown in formula (I).

[0056] Example 1

[0057] This embodiment provides a method for preparing a star-branched viscosity-reducing polycarboxylate water-reducing agent, specifically:

[0058] 1) Preparation of star-shaped temperature-sensitive photoinitiator:

[0059] 2.52 g of 4-acryloylhydroxybenzoic acid benzophenone (0.01 mol), 56.5 g of N-isopropylacrylamide (0.5 mol) and 137.713 g of water were placed in a reaction bottle equipped with a stirring device, and the reactor was placed in a constant temperature water bath (25±1°C). After stirring and dissolving, 0.0091 g of copper powder and 0.0134 g of copper bromide were added to the reaction bottle in sequence to obtain a mixed reactant I;

[0060] The mixture was evacuated by passing high-purity nitrogen gas, and 0.0692 g of ligand tris(2-dimethylaminoethyl)amine was transferred after 10 min. Then, 0.0936 g of initiator PA-Br6 was quickly added after 8 min to initiate the polymerization reaction.

[0061] After reacting for 3 hours under nitrogen protection under closed conditions, the reaction was stopped, the copper powder and copper bromide in the reaction system were removed through a neutral alumina column, and the filtrate was rotary evaporated using a rotary evaporator. Finally, the concentrated solution was precipitated with petroleum ether, and the obtained precipitate was dried under vacuum conditions to obtain a structure as shown in Figure 1 Star-shaped thermosensitive macroinitiator shown.

[0062] Figure 2This is a schematic diagram of the temperature sensitivity of the star-shaped thermosensitive macromolecular initiator prepared in this step. It can be seen that the transmittance of the aqueous solution of the star-shaped thermosensitive macromolecular initiator has a significant dependence on temperature. As the temperature increases, the transmittance of the solution gradually decreases and eventually turns into a milky white solution, which indicates that the star-shaped thermosensitive macromolecular initiator is temperature sensitive.

[0063] 2) preparing a star-branched polymer viscosity reducer;

[0064] At 25°C, 135g of water, 75g of polyether macromonomer allyl polyoxyethylene ether APEG (the molecular weight of APEG is 2400), 15g of acrylic acid, 0.55g of mercaptopropionic acid, and 1.35g of thermosensitive macromolecular photoinitiator are put into a photoinitiator reactor, stirred to dissolve, and mixed evenly to obtain a transparent mixed solution;

[0065] The mixed solution was irradiated under a 350W high-pressure mercury lamp for 3 hours to obtain the hydration thermal response thixotropic robust star-branched viscosity-reducing polycarboxylate water-reducing agent of this embodiment, with a mass concentration of 40%.

[0066] Example 2

[0067] The difference between this embodiment and embodiment 1 is that the polyether macromonomer APEG in step 3) is adjusted to isobutylene alcohol polyoxyethylene ether HPEG (the molecular weight of HPEG is 2400), and the remaining steps and processes are all referred to embodiment 1 to obtain the star-branched viscosity-reducing polycarboxylic acid water-reducing agent of this embodiment, and its mass concentration is 40%.

[0068] Example 3

[0069] The difference between this embodiment and embodiment 1 is that the polyether macromonomer APEG in step 3) is adjusted to isopentene polyoxyethylene ether TPEG (the molecular weight of TPEG is 2400), and the remaining steps and processes are all referred to embodiment 1 to obtain the star-branched viscosity-reducing polycarboxylic acid water-reducing agent of this embodiment, and its mass concentration is 40%.

[0070] Example 4

[0071] The difference between this embodiment and embodiment 1 is that the amount of the thermosensitive macromolecular photoinitiator in step 3) is adjusted to 0.9 g, and the remaining steps and processes are all referred to embodiment 1, to obtain the star-branched viscosity-reducing polycarboxylic acid water-reducing agent of this embodiment, and its mass concentration is 40%.

[0072] Application Testing

[0073] The star-branched viscosity-reducing polycarboxylate water-reducing agent prepared in each embodiment was used to prepare concrete. The viscosity of the obtained concrete was evaluated by flow time according to the standard GB8076-2008. The concrete mix ratio adopted the engineering C50 mix ratio, and the single material consumption was 450 kg / m3 、Fly ash 50kg / m 3 、Sand 682kg / m 3 、Stone 1113kg / m 3 , water 155kg / m 3 The water reducing agent dosage is 0.30% of the cementitious material dosage (in terms of solid content). The specific method is: invert the slump cone, cover the bottom, fill it with concrete and smooth it (generally fix the inverted slump cone on a bracket with the bottom 50cm above the ground), quickly slide the bottom cover open, and use a stopwatch to measure the time it takes for the concrete to flow out.

[0074] The thixotropic robust star-branched polymer viscosity reducer of the present invention and the conventional polycarboxylate water reducer were used to measure the flow of the slurry according to GB / T 8077-2012 "Test Method for Homogeneity of Concrete Admixtures" and the concrete mixture performance test was measured with reference to GB / T 50080-2002 "Standard for Test Method for Performance of Ordinary Concrete Mixtures", and the cement was used as the reference cement. The test results are shown in Table 1.

[0075] Table 1

[0076]

[0077] It can be seen from Table 1 that compared with commercially available water-reducing agents, the void time of concrete configured with the synthetic viscosity-reducing polycarboxylic acid water-reducing agent in the embodiments of this patent is less than 10s. The void time of the sample in Example 3 is only 7.46s, which is much lower than the void time of 10.25s of the commercially available polycarboxylic acid water-reducing agent product. The samples in the embodiments of this patent can significantly reduce the viscosity of high-strength grade concrete and improve the fluidity of concrete.

[0078] In summary, the present invention introduces the design concept of "thermosensitive polymer" into the molecular structure design of concrete admixtures, utilizes thermosensitive star-shaped macromolecular photoinitiators, and prepares a new type of star-shaped branched viscosity-reducing polycarboxylic acid water-reducing agent with hydration thermal response through a green and environmentally friendly photoinitiator polymer synthesis process, and achieves the goal of energy saving and low carbon through the whole process system design and control concept.

[0079] The polymer viscosity reducer constructed by the present invention has a star-branched divergent structure. The molecular structure has a small hydrodynamic radius, a thick adsorption layer, and a low pore solution viscosity, and can reduce the pore solution viscosity of the cement slurry to achieve rapid flow; at the same time, the long hydrophobic chain contained in the arm and the phytic acid core containing 6 phosphate groups can provide a large steric hindrance for the cement particles, so that the cement particles are evenly dispersed, and a large amount of flocculated water wrapped therein is released, thereby reducing the viscosity and improving the fluidity and mechanical properties of the cement slurry.

[0080] The present invention utilizes the heat release of cement paste hydration to stimulate the thermosensitive polymer arms in the star-branched viscosity-reducing polycarboxylate water-reducing agent molecules to undergo hydrophobic association to form a network structure in the cement paste. When the system is subjected to shear force, the formed network structure is destroyed, the system recovers fluidity, and the viscosity decreases. When the shear force stops, the system re-forms the network structure through hydrophobic association, and the viscosity increases, thereby achieving synergy between fluidity and stability.

[0081] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention may be modified or replaced by equivalents without departing from the spirit and scope of the technical solutions of the present invention, which should all be included in the scope of the claims of the present invention.

Claims

1. A star-shaped temperature-sensitive photoinitiator, characterized in that: It is composed of: a. A repeating unit derived from a phytic acid-based initiator PA-Br6 having a structural formula as shown in formula (I); b. a repeating unit of a photoinitiated thermosensitive polymer chain connected to the C-Br group of the phytic acid-based initiator PA-Br6 shown in formula (I), having a structure as shown in formula (II), wherein m and n represent the number of repeating units, and m and n are non-zero integers; c. The photoinitiated thermosensitive polymer chain is obtained by polymerization of 4-acryloylhydroxybenzoic acid benzophenone and N-isopropylacrylamide as monomers and tris(2-dimethylaminoethyl)amine or tris(2-aminoethyl)amine as a ligand, wherein the molar ratio of 4-acryloylhydroxybenzoic acid benzophenone to N-isopropylacrylamide is 2 to 10:100; d. The mass ratio of the monomer and ligand in the repeating unit phytic acid-based initiator PA-Br6 compared to the repeating unit photo-initiated thermosensitive polymer chain is 0.15-0.85:25~50:0.05~0.

35.

2. The method for preparing the star-shaped temperature-sensitive photoinitiator according to claim 1, characterized in that: include, The monomer and solvent water are stirred and dissolved, and then a catalyst and a deactivator are added to obtain a mixed reactant I; Mix the reactants I in a constant temperature water bath at 15-30° C., pass an inert gas to remove oxygen in the reaction system, add a ligand to react for 10-30 minutes, and then add a phytic acid initiator PA-Br6 to initiate a polymerization reaction; After the polymerization reaction occurs, the reaction is continued for 60 to 240 minutes under closed conditions. The product is passed through a neutral alumina column to remove the catalyst and the deactivator in the reaction system to obtain a filtrate, which is then post-treated to obtain a thermosensitive macromolecular photoinitiator.

3. The method for preparing the star-shaped temperature-sensitive photoinitiator according to claim 2, characterized in that: The post-treatment includes rotary evaporating the filtrate with a rotary evaporator, and finally precipitating the concentrated liquid with petroleum ether, and drying the obtained precipitate under vacuum conditions.

4. The method for preparing the star-shaped temperature-sensitive photoinitiator according to claim 2, characterized in that: In the polymerization reaction system, the content of each raw material is, by mass percentage, Monomer 25-50%, initiator PA-Br6 0.15-0.85%, catalyst 0.01-0.3%, ligand 0.05-0.35%, deactivator 0.001-0.02%, the balance is water; Wherein, the monomers are 4-acryloylhydroxybenzoic acid benzophenone and N-isopropylacrylamide, and the molar ratio of 4-acryloylhydroxybenzoic acid benzophenone to N-isopropylacrylamide is 2 to 10:100; The ligand includes one of tris(2-dimethylaminoethyl)amine or tris(2-aminoethyl)amine; The catalyst is copper powder, and the deactivator is copper bromide.

5. A star-branched viscosity-reducing polycarboxylate water-reducing agent, characterized in that: It is composed of: i. A repeating unit derived from the star-shaped temperature-sensitive initiator according to claim 1; ii. a repeating unit derived from at least one unsaturated monomer, wherein the unsaturated monomer is selected from one of acrylic acid or methacrylic acid; iii. a repeating unit derived from at least one polyether macromonomer, wherein the polyether macromonomer is selected from one of allyl polyoxyethylene ether, isobutylene alcohol polyoxyethylene ether or isopentyl polyoxyethylene ether, and has a molecular weight of 1000 to 3000; iv. The mass ratio of the repeating unit star-shaped thermosensitive macromolecular initiator to the repeating unit unsaturated monomer and the polyether macromonomer is 2-10:60-80:15-25.

6. The method for preparing the star-branched viscosity-reducing polycarboxylate water-reducing agent according to claim 5, characterized in that: include, Unsaturated monomers, polyether macromonomers, thermosensitive macromolecular photoinitiators, molecular weight regulators and deionized water are put into a photoinitiator reactor and dissolved to obtain a transparent mixed solution I; The transparent mixed solution is irradiated under a 350W high-pressure mercury lamp to obtain a star-branched polymer viscosity reducer with a hydrothermal response.

7. The method for preparing the star-branched viscosity-reducing polycarboxylate water-reducing agent according to claim 6, characterized in that: In terms of mass percentage of the mixed solution I, the content of each raw material is: The polyether macromonomer is 15-25%, the unsaturated monomer is 60-80%, the temperature-sensitive macromolecular photoinitiator is 2-10%, the molecular weight regulator is 0.01-0.5%, and the balance is water.

8. The method for preparing the star-branched viscosity-reducing polycarboxylate water-reducing agent according to claim 7, characterized in that: The molecular weight regulator includes one of mercaptopropionic acid or thioglycolic acid.

9. The method for preparing the star-branched viscosity-reducing polycarboxylate water-reducing agent according to claim 6, characterized in that: The treatment temperature of the irradiation treatment is 15-35° C., and the irradiation time is 2-4 hours.

10. Use of the star-branched viscosity-reducing polycarboxylate water-reducing agent according to claim 5 in preparing concrete.

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