Photoresponsive brush-like macromolecular emulsifier and preparation method thereof

Abstract

The invention provides a photoresponsive brush-like macromolecular emulsifier and a preparation method thereof, and relates to the technical field of polymer synthesis, and the preparation method comprises the following steps: (a) adding a dehydrating agent and a catalyst into a mixture of 5-norbornene-2-exomethanol and a terminal carboxyl group modified hydrophilic polymer, and reacting to obtain a hydrophilic monomer; (b) reacting a chain transfer agent containing a norbornene unit, a methyl acrylate monomer containing a spiropyrane unit and a free radical polymerization initiator to obtain a hydrophobic monomer; and (c) reacting the hydrophilic monomer with the hydrophobic monomer to obtain the photoresponsive brush-like macromolecular emulsifier. According to the photoresponse type brush-like macromolecular emulsifier and the preparation method thereof provided by the invention, the use of a pH regulator or inorganic salt is avoided, impurities are not introduced into a system, and the obtained emulsifier can be reversibly assembled and disassembled on a water / oil interface, so that multiple circulation formation and controllable damage of an emulsion are realized.

Description

Technical Field

[0001] This invention relates to the field of polymer synthesis technology, and in particular to a photoresponsive brush-like macromolecular emulsifier and its preparation method. Background Technology

[0002] Amphiphilic compounds, possessing both hydrophilic and hydrophobic structures, are widely used as emulsifiers. Compared to small-molecule emulsifiers such as sodium dodecyl sulfate, macromolecular emulsifiers offer greater flexibility in controlling topology, molecular weight, and chemical composition, exhibiting stronger interfacial adsorption capabilities and significantly improving emulsion stability. Among these, amphiphilic block copolymers are the most widely used; while brush polymers, with their densely grafted amphiphilic side chains, offer greater contact area and stronger interaction with the oil-water interface, providing higher stability than linear block copolymers. Responsive emulsifiers can achieve reversible disruption and reconstruction of emulsions through external stimuli, making them suitable for rare resource separation scenarios such as crude oil recovery. While pH-responsive brush emulsifiers have been reported, repeatedly adjusting the pH value to disrupt and reconstruct the emulsion introduces large amounts of inorganic salts, which severely affect emulsion stability. Summary of the Invention

[0003] One of the objectives of this invention is to provide a photoresponsive brush-like macromolecular emulsifier to at least solve one of the technical problems existing in the prior art.

[0004] The second objective of this invention is to provide a method for preparing a photoresponsive brush-like macromolecular emulsifier.

[0005] In order to achieve the above-mentioned objectives of the present invention, the following technical solution is adopted: In a first aspect, the present invention provides a method for preparing a photoresponsive brush-like macromolecular emulsifier, comprising: (a) A dehydrating agent and a catalyst were added to a mixture of 5-norbornene-2-exo-methanol and a hydrophilic polymer modified with a carboxyl group to obtain a hydrophilic monomer. (b) A chain transfer agent containing norbornene units, a methyl acrylate monomer containing spiropyran units, and a free radical polymerization initiator are reacted to obtain a hydrophobic monomer; (c) The hydrophilic monomer and the hydrophobic monomer react to obtain the photoresponsive brush-like macromolecular emulsifier.

[0006] Furthermore, the molar ratio of the 5-norbornene-2-exogenous methanol to the carboxyl-terminated hydrophilic polymer is 10:0.5-1; Preferably, the carboxyl-terminated hydrophilic polymer includes at least one of carboxyl-modified polyethylene glycol and carboxyl-modified polyacrylamide; Preferably, the number-average molecular weight of the hydrophilic polymer modified with terminal carboxyl groups is 1000-5000; Preferably, the dehydrating agent comprises at least one of dicyclohexylcarbodiimide and 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride; Preferably, the catalyst comprises at least one of 4-dimethylaminopyridine and 4-pyrrolidinylpyridine; Preferably, the molar ratio of the dehydrating agent, the catalyst, the 5-norbornene-2-exogenous methanol, and the carboxyl-terminated hydrophilic polymer is 1.5-2:0.5-0.6:10:0.5-1; Preferably, the reaction in step (a) is carried out in the first solvent; Preferably, the first solvent includes at least one of dichloromethane, tetrahydrofuran, and chloroform.

[0007] Furthermore, the reaction temperature in step (a) is -10 to 0°C, and the reaction time is 8 to 28 hours.

[0008] Furthermore, the molar ratio of the chain transfer agent containing norbornene units, the methyl acrylate monomer containing spiropyran units, and the free radical polymerization initiator is 1:10-50:0.1; Preferably, the chain transfer agent containing norbornene units includes at least one of NB-DTPA and NB-CDTPA; Preferably, the methyl acrylate monomer containing a spiropyran unit includes at least one of SPMA and SPA; Preferably, the free radical polymerization initiator includes at least one of azobisisobutyronitrile and benzoyl peroxide; Preferably, the reaction in step (b) is carried out in the second solvent; Preferably, the second solvent includes at least one of toluene and chloroform.

[0009] Furthermore, the reaction temperature in step (b) is 60-80℃, and the reaction time is 2-3h.

[0010] Furthermore, a third-generation Grubb catalyst is added to the reaction in step (c); Preferably, the molar ratio of the hydrophilic monomer, the hydrophobic monomer, and the third-generation Grubb catalyst is 10-100:10-100:1.

[0011] Furthermore, the reaction temperature in step (c) is 0-25℃, and the reaction time is 0.5-2.5h.

[0012] Furthermore, it also includes step (d): dispersing the photoresponsive brush-like macromolecular emulsifier obtained in step (c) in a third solvent, and then mechanically dispersing it to obtain an oil-in-water emulsion; The oil-in-water emulsion is irradiated with ultraviolet light, and after the ultraviolet light is removed, it is mechanically dispersed to obtain an oil-in-water emulsion.

[0013] Furthermore, in step (d), the dispersion concentration of the photoresponsive brush-like macromolecular emulsifier in the third solvent is 0.05-0.2 wt%; Preferably, the third solvent is a mixture of toluene and water.

[0014] Secondly, the present invention provides a photoresponsive brush-like macromolecular emulsifier prepared by a method thereof.

[0015] Compared with the prior art, the present invention has the following beneficial effects: The photoresponsive brush-like macromolecular emulsifier provided by this invention is obtained by stepwise construction of bifunctional monomers and catalytic copolymerization to obtain a photoresponsive amphiphilic copolymer. Among them, the hydrophilic monomer provides hydrophilic brush arms with large steric hindrance and excellent water solubility, while the hydrophobic monomer introduces spiropyran units with light-controlled reversible conformational transformation. The two work together to endow the emulsifier with strong interfacial anchoring ability and responsiveness to exogenous stimuli. This preparation method avoids the use of pH adjusters or inorganic salts and does not introduce impurities into the system. The obtained emulsifier can be reversibly assembled and disassembled at the water / oil interface, thereby realizing multiple cycles of emulsion formation and controllable destruction. Attached Figure Description

[0016] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0017] Figure 1 A schematic diagram of the synthesis route of the photoresponsive brush-type macromolecular emulsifier provided by the present invention; Figure 2 This is a schematic diagram of the reconstruction-destruction process of a photoresponsive emulsion. Detailed Implementation

[0018] Unless otherwise defined herein, the scientific and technical terms used in conjunction with this invention shall have the meanings commonly understood by one of ordinary skill in the art. The meaning and scope of terms shall be clear; however, in any case of potential ambiguity, the definitions provided herein shall prevail over any dictionary or foreign definitions. In this application, unless otherwise stated, the use of "or" means "and / or". Furthermore, the use of the term "comprising" and other forms is non-limiting.

[0019] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0020] like Figure 1 As shown, the first aspect of the present invention provides a method for preparing a photoresponsive brush-like macromolecular emulsifier, comprising: (a) Add a dehydrating agent and a catalyst to a mixture of 5-norbornene-2-exogenous methanol and a hydrophilic polymer modified with a carboxyl group, and react to obtain a norbornene derivative with PEG units, denoted as hydrophilic macromonomer M1. (b) A chain transfer agent containing norbornene units, a methyl acrylate monomer containing spiropyran units, and a free radical polymerization initiator are reacted to obtain a hydrophobic macromonomer M2 with norbornene units at the end. (c) The hydrophilic monomer and the hydrophobic monomer react to obtain the photoresponsive brush-like macromolecular emulsifier.

[0021] To address the problems of low emulsion stability, non-recyclability of emulsifiers, and the need to introduce other impurities that easily damage emulsion stability in existing technologies, this invention proposes a photoresponsive brush-like macromolecular emulsifier. By applying and removing ultraviolet light, a reversible destruction-reconstruction process of the emulsion can be achieved. This exogenous stimulation does not change the composition of the emulsion itself and does not affect the stability of the subsequent emulsion.

[0022] This invention first synthesizes a macromonomer M1 containing a hydrophilic polymer chain PEG and a polymerizable norbornene unit through a simple esterification reaction. Then, a macromonomer M2 containing a photoresponsive spiropyran unit and a polymerizable norbornene unit is prepared via living radical polymerization. Upon exposure to ultraviolet light, the spiropyran unit in M2 undergoes a ring-opening reaction, and the entire polymer chain changes from hydrophobic to hydrophilic. Upon removal of ultraviolet light, it reverts to its original closed-ring hydrophobic structure. The copolymerization of macromonomers M1 and M2 is initiated using a third-generation Grubb catalyst to prepare a photoresponsive brush-type polymer. Compared to ordinary emulsifiers, this photoresponsive brush-type macromolecular emulsifier, with its large volume, provides higher stability to the emulsion. Furthermore, as a responsive emulsifier, it can be recycled multiple times and can achieve emulsion formation and destruction as needed. Finally, this photoresponsiveness does not introduce any impurities into the emulsion itself, thus ensuring the purity and stability of the emulsion components.

[0023] Figure 1This is a schematic diagram of the synthesis route of a photoresponsive brush-type macromolecular emulsifier. Optionally, x = 5~100, x is more preferably 10~100, y = 5~100, y is more preferably 10~100, m = 5~50, m is more preferably 10~50. The above values ​​can be controlled by the proportions during feeding.

[0024] Figure 2 Images of oil-in-water emulsions stabilized by this type of macromolecular emulsifier and a schematic diagram of photoresponsive demulsification-reconstruction are shown. Under normal conditions, the amphiphilic side chains of the macromolecule can be used to stabilize oil-in-water emulsions. When ultraviolet light is applied, the spiropyran unit undergoes a ring-opening reaction, changing from hydrophobic to hydrophilic. The entire macromolecule becomes completely hydrophilic and dissolves in water, at which point the emulsion is disrupted. When the ultraviolet light is removed, the spiropyran reverts to its closed-ring structure, allowing the macromolecule to return to its amphiphilic structure and continue to be used to stabilize oil-in-water emulsions. This intelligent responsive macromolecular emulsifier has broad application prospects in the field of rare resource extraction.

[0025] In some preferred embodiments, in step (a), the molar ratio of the 5-norbornene-2-exogenous methanol to the carboxyl-terminated hydrophilic polymer is 10:0.5-1.

[0026] Preferably, the carboxyl-terminated hydrophilic polymer includes at least one of carboxyl-modified polyethylene glycol and carboxyl-modified polyacrylamide.

[0027] Preferably, the number average molecular weight of the hydrophilic polymer modified with the terminal carboxyl group is 1000-5000.

[0028] Preferably, the dehydrating agent comprises at least one of dicyclohexylcarbodiimide and 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride.

[0029] Preferably, the catalyst comprises at least one of 4-dimethylaminopyridine and 4-pyrrolidinylpyridine.

[0030] Preferably, the molar ratio of the dehydrating agent, the catalyst, the 5-norbornene-2-exogenous methanol, and the carboxyl-terminated hydrophilic polymer is 1.5-2:0.5-0.6:10:0.5-1; wherein, "1.5-2" can be, for example, 1.5, 1.6, 1.7, 1.8, 1.9, 2, etc.; "0.5-0.6" can be, for example, 0.5, 0.55, 0.6, etc.; and "0.5-1" can be, for example, 0.5, 0.75, 1, etc.

[0031] Preferably, the reaction in step (a) is carried out in a first solvent; preferably, the first solvent includes at least one of dichloromethane, tetrahydrofuran, and chloroform.

[0032] In some preferred embodiments, the reaction temperature in step (a) is -10 to 0°C, for example, -10°C, -5°C, 0°C, etc.; the reaction time is 8 to 28 hours, for example, 8 hours, 18 hours, 28 hours, etc.

[0033] In some preferred embodiments, in step (b), the molar ratio of the chain transfer agent containing norbornene units, the methyl acrylate monomer containing spiropyran units, and the free radical polymerization initiator is 1:10-50:0.1; wherein, "10-50" can be, for example, 10, 20, 30, 40, 50, etc.

[0034] Preferably, the chain transfer agent containing norbornene units includes at least one of NB-DTPA and NB-CDTPA.

[0035] Preferably, the methyl acrylate monomer containing spiropyran units includes at least one of SPMA and SPA.

[0036] Preferably, the free radical polymerization initiator includes at least one of azobisisobutyronitrile and benzoyl peroxide.

[0037] Preferably, the reaction in step (b) is carried out in a second solvent; preferably, the second solvent includes at least one of toluene and chloroform.

[0038] In some preferred embodiments, the reaction temperature in step (b) is 60-80°C, for example, 60°C, 70°C, 80°C, etc.; the reaction time is 2-3 hours, for example, 2 hours, 2.5 hours, 3 hours, etc.

[0039] In some preferred embodiments, a third-generation Grubb catalyst is also added to the reaction in step (c); Preferably, the molar ratio of the hydrophilic monomer, the hydrophobic monomer, and the third-generation Grubb catalyst is 10-100:10-100:1; wherein "10-100" can be, for example, 10, 20, 30, 40, 50, 60, 70, 80, 90, 100, etc., and is more preferably 10-30:10-40:1.

[0040] In some preferred embodiments, the reaction temperature in step (c) is 0-25°C, for example, 0°C, 5°C, 10°C, 15°C, 20°C, 25°C, etc., and more preferably 5-25°C, and the reaction time is 0.5-2.5h, for example, 0.5h, 1h, 1.5h, 2h, 2.5h, etc.

[0041] In some preferred embodiments, to verify and impart the photoresponsive function to the brush-like macromolecular emulsifier, the method further includes the following functionalization post-processing step (d): dispersing the photoresponsive brush-like macromolecular emulsifier obtained in step (c) in a third solvent, and mechanically dispersing it to obtain an oil-in-water emulsion; the oil-in-water emulsion is irradiated with ultraviolet light, and after the ultraviolet light irradiation is removed, it is mechanically dispersed to obtain an oil-in-water emulsion.

[0042] In some preferred embodiments, in step (d), the dispersion concentration of the photoresponsive brush-like macromolecular emulsifier in the third solvent is 0.05-0.2 wt%, for example, it can be 0.05 wt%, 0.1 wt%, 0.15 wt%, 0.2 wt%, etc.

[0043] Preferably, the third solvent is a mixture of toluene and water.

[0044] A second aspect of the present invention provides a photoresponsive brush-like macromolecular emulsifier prepared by the above-described preparation method.

[0045] In a preferred embodiment of the present invention, the preparation method of the photoresponsive brush-like macromolecular emulsifier includes the following steps: Step a: 5-norbornene-2-exogenous methanol and carboxyl-modified polyethylene glycol (PEG) (molecular weight 2000) are placed in dichloromethane and stirred. The molar ratio of the two is 10:0.5~1. A certain amount of dicyclohexylcarbodiimide (DCC) is added as a dehydrating agent, and a certain amount of 4-dimethylaminopyridine (DMAP) is added as a catalyst. The molar ratio of these two to the reactants is 1.5~2:0.5~0.6:10:0.5~1. The reaction is carried out at a first set temperature (-10~0℃) for a first set time (8~28h) to obtain a norbornene derivative containing PEG units, denoted as hydrophilic macromonomer M1; Step b: Add the chain transfer agent NB-DTPA with norbornene units, the methyl acrylate monomer SPMA with spiropyran units, and the free radical polymerization initiator azobisisobutyronitrile (AIBN) to toluene, with a molar ratio of 1:10~50:0.1; react at a second set temperature (60~80℃) for a second set time (2~3h) to obtain the norbornene-terminated hydrophobic macromonomer M2; Step c: Mix macromonomers M1 and M2 with the third-generation Grubb catalyst in a molar ratio of 10~100:10~100:1 and dissolve them in dichloromethane. React at a third set temperature (0~25℃) for a third set time (0.5~2.5h) to obtain an amphiphilic brush polymer. Step d: Disperse the brush-type polymer at 0.1 wt% in a water / toluene = 1 / 1 (mass ratio) mixed solution. Vigorous dispersion can obtain an oil-in-water emulsion. This emulsion will demulsify after being irradiated with 365 nm ultraviolet light. After the ultraviolet light is removed, vigorous dispersion can be continued to obtain a stable oil-in-water emulsion. This process can be repeated more than 30 times.

[0046] The present invention will be further illustrated by the following examples. Unless otherwise specified, the materials in the examples are prepared according to existing methods or purchased directly from the market.

[0047] Example 1 This embodiment provides a method for preparing a photoresponsive brush-type macromolecular emulsifier, specifically including the following steps: Step 1: 20 g of 5-norbornene-2-exogenous methanol and 40 g of carboxyl-modified polyethylene glycol (PEG) (molecular weight 2000) were placed in 1 L of dichloromethane and stirred. The molar ratio of the two was 10:1. 25 g of dicyclohexylcarbodiimide (DCC) was added as a dehydrating agent, and 10 g of 4-dimethylaminopyridine (DMAP) was added as a catalyst. The molar ratio of the two to the reactants was 1.5:0.5:10:1. The reaction was carried out at 0 °C for a first set time of 8 h to obtain a norbornene derivative containing PEG units, denoted as the hydrophilic macromonomer M1 (Mn=2100). Step 2: Add 1g of chain transfer agent NB-DTPA with norbornene units, 20g of methyl acrylate monomer SPMA with spiropyran units, and 0.15g of free radical polymerization initiator azobisisobutyronitrile (AIBN) to toluene, with a molar ratio of 1:30:0.1; react at 80℃ for a second set time of 3h to obtain a hydrophobic macromonomer M2Mn=5200 with norbornene units at the end. Step 3: Mix macromonomers M1 (4g) and M2 (7g) with 0.4g of third-generation Grubb catalyst (dichloro-1,3-bis(2,4,6-trimethylphenyl)-2-imidazolidinedimethylbis(3-bromopyridine)ruthenium(II)) in dichloromethane at a molar ratio of 30:30:1, and react at 25°C for a third set time of 0.5 h to obtain an amphiphilic brush polymer (where m=24, x=11, y=12 in the amphiphilic brush polymer).

[0048] Example 2 This embodiment provides a method for preparing a photoresponsive brush-type macromolecular emulsifier, which differs from Example 1 in that: In step 1, the reaction temperature is -10℃ and the reaction time is 12h; In step 2, the reaction temperature is 60℃ and the reaction time is 3 hours. In step 3, macromonomers M1 (7g, Mn=2100) and M2 (4.7g, Mn=4200) were mixed with 0.4g of third-generation Grubb catalyst in a molar ratio of 30:10:1 and dissolved in dichloromethane. The reaction was carried out at 15°C for a set time of 1 h to obtain an amphiphilic brush polymer. (Where m=20, x=15, y=6 in the amphiphilic brush polymer).

[0049] Example 3 This embodiment provides a method for preparing a photoresponsive brush-type macromolecular emulsifier, which differs from Example 1 in that: In step 1, the reaction temperature is -5℃ and the reaction time is 24h; In step 2, the reaction temperature is 70℃ and the reaction time is 6 hours. In step 3, macromonomers M1 (2g, Mn=2100) and M2 (23.6g, Mn=6200) and 0.4g of third-generation Grubb catalyst were mixed and dissolved in dichloromethane at a molar ratio of 10:40:1. The reaction was carried out at 5°C for a third set time of 2 h to obtain an amphiphilic brush polymer (where m=28, x=8, y=35 in the amphiphilic brush polymer).

[0050] Example 4 This embodiment provides a method for preparing a photoresponsive brush-type macromolecular emulsifier, which differs from Example 1 in that: In step 1, 20 g of 5-norbornene-2-exogenous methanol and 20 g of carboxyl-modified polyethylene glycol (PEG) (molecular weight 2000) were placed in 1 L of dichloromethane and stirred. The molar ratio of the two was 10:0.5. The hydrophilic macromonomer M1 with Mn=2100 was obtained. In step 2, 1g of chain transfer agent NB-DTPA with norbornene unit, 7g of methyl acrylate monomer SPMA with spiropyran unit, and 0.15g of free radical polymerization initiator azobisisobutyronitrile (AIBN) are added to toluene in a molar ratio of 1:10:0.1 to obtain hydrophobic macromonomer M2 with Mn=1500.

[0051] The final amphiphilic brush polymer was prepared with m=8, x=7, and y=28.

[0052] Example 5 This embodiment provides a method for preparing a photoresponsive brush-type macromolecular emulsifier, which differs from Example 1 in that: In step 1, 20 g of 5-norbornene-2-exogenous methanol and 30 g of carboxyl-modified polyethylene glycol (PEG) (molecular weight 2000) were placed in 1 L of dichloromethane and stirred. The molar ratio of the two was 10:0.75. The hydrophilic macromonomer M1 with Mn=2100 was obtained. In step 2, 1g of chain transfer agent NB-DTPA with norbornene unit, 33g of methyl acrylate monomer SPMA with spiropyran unit, and 0.15g of free radical polymerization initiator azobisisobutyronitrile (AIBN) were added to toluene in a molar ratio of 1:50:0.1 to obtain hydrophobic macromonomer M2 with Mn=6400.

[0053] The final amphiphilic brush polymer was prepared with m=40, x=6, and y=33.

[0054] Example 6 This embodiment provides a method for preparing a photoresponsive brush-type macromolecular emulsifier, which differs from Example 1 in that: In step 1, the reaction temperature is -15℃ and the reaction time is 30h; a hydrophilic macromolecular monomer M1 with Mn=2100 is obtained. In step 2, the reaction temperature is 55℃ and the reaction time is 4h; hydrophobic macromolecular monomer M2 with Mn=3300 is obtained. In step 3, the reaction temperature is 0℃ and the reaction time is 3h.

[0055] The final amphiphilic brush polymer was prepared with m=22, x=8, and y=23.

[0056] Example 7 This embodiment provides a method for preparing a photoresponsive brush-type macromolecular emulsifier, which differs from Example 1 in that: In step 1, the reaction temperature is 5℃ and the reaction time is 6h; a hydrophilic macromolecular monomer M1 with Mn=2100 is obtained. In step 2, the reaction temperature is 85℃ and the reaction time is 1h; hydrophobic macromolecular monomer M2 with Mn=2000 is obtained. In step 3, the reaction temperature is 30℃ and the reaction time is 0.5h.

[0057] The final amphiphilic brush polymer was prepared with m=10, x=9, and y=38.

[0058] Comparative Example 1 This comparative example provides a method for preparing a macromolecular emulsifier, which differs from Example 1 in that: in step 1, sodium dodecyl sulfate (SDS) is used to replace carboxyl-modified polyethylene glycol as the hydrophilic component.

[0059] Comparative Example 2 This comparative example provides a method for preparing a macromolecular emulsifier, which differs from Example 1 in that: in step 2, ordinary methyl acrylate (MA) is used instead of methyl acrylate monomers with spiropyran units.

[0060] Test case The macromolecular emulsifiers prepared in Examples 1-7 and Comparative Examples 1-2 were used as samples for testing.

[0061] Test 1, Number of cycles for light-controlled emulsion: The sample was dispersed at 0.1 wt% in a water:toluene = 1:1 (mass ratio) mixture to obtain an oil-in-water emulsion. The emulsion was then subjected to the following cycling operation: (1) Irradiate under 365 nm ultraviolet light for 5 min; (2) Stop irradiation and let stand in the dark for 10 minutes; (3) Disperse vigorously again (using a vortex mixer at 6000 rpm for 1 min); After each cycle, the macroscopic state of the emulsion is captured using a camera.

[0062] Test 2: The stability and uniformity of the emulsion droplets were determined using an optical microscope.

[0063] The test results are shown in Table 1.

[0064] Table 1

[0065] As shown in Table 1, all examples exhibit significantly better photoresponsive emulsion cycling performance and interfacial stability than the comparative examples. Comparative Example 1 uses a small molecule surfactant to replace the hydrophilic macromolecular brush arm, resulting in weak interfacial anchoring and easy desorption; Comparative Example 2 lacks the spiropyran responsive motif, thus completely losing its photocontrolled conformational change capability and failing to achieve reversible demulsification-reconstruction. Both examples demonstrate the irreplaceable nature of this invention at the molecular design level.

[0066] Examples 1-5, using parameters within the preferred range defined by this invention, yielded emulsifiers that balanced the steric hindrance effect of the hydrophilic brush arms with the highly efficient photoresponsiveness of the spiropyran units in the hydrophobic side chains. While the parameters in Examples 6-7, deviating from the preferred range defined by this invention, still retained basic functionality, they exhibited some attenuation in cycle durability and interfacial behavior uniformity. It is evident that the macromolecular emulsifier prepared within the preferred range of process parameters defined by this invention demonstrates superior performance. This brush-like macromolecular emulsifier exhibits excellent photoresponsiveness, allowing for emulsion demulsification and recombination through the application and removal of light.

[0067] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing a photoresponsive brush-like macromolecular emulsifier, characterized in that, include: (a) A dehydrating agent and a catalyst were added to a mixture of 5-norbornene-2-exo-methanol and a hydrophilic polymer modified with a carboxyl group to obtain a hydrophilic monomer. (b) A chain transfer agent containing norbornene units, a methyl acrylate monomer containing spiropyran units, and a free radical polymerization initiator are reacted to obtain a hydrophobic monomer; (c) The hydrophilic monomer and the hydrophobic monomer react to obtain the photoresponsive brush-like macromolecular emulsifier.

2. The preparation method according to claim 1, characterized in that, The molar ratio of 5-norbornene-2-exogenous methanol to the carboxyl-terminated hydrophilic polymer is 10:0.5-1; Preferably, the carboxyl-terminated hydrophilic polymer includes at least one of carboxyl-modified polyethylene glycol and carboxyl-modified polyacrylamide; Preferably, the number-average molecular weight of the hydrophilic polymer modified with terminal carboxyl groups is 1000-5000; Preferably, the dehydrating agent comprises at least one of dicyclohexylcarbodiimide and 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride; Preferably, the catalyst comprises at least one of 4-dimethylaminopyridine and 4-pyrrolidinylpyridine; Preferably, the molar ratio of the dehydrating agent, the catalyst, the 5-norbornene-2-exogenous methanol, and the carboxyl-terminated hydrophilic polymer is 1.5-2:0.5-0.6:10:0.5-1; Preferably, the reaction in step (a) is carried out in the first solvent; Preferably, the first solvent includes at least one of dichloromethane, tetrahydrofuran, and chloroform.

3. The preparation method according to claim 1, characterized in that, The reaction temperature in step (a) is -10 to 0℃, and the reaction time is 8 to 28 hours.

4. The preparation method according to claim 1, characterized in that, The molar ratio of the chain transfer agent containing norbornene units, the methyl acrylate monomer containing spiropyran units, and the free radical polymerization initiator is 1:10-50:0.1; Preferably, the chain transfer agent containing norbornene units includes at least one of NB-DTPA and NB-CDTPA; Preferably, the methyl acrylate monomer containing a spiropyran unit includes at least one of SPMA and SPA; Preferably, the free radical polymerization initiator includes at least one of azobisisobutyronitrile and benzoyl peroxide; Preferably, the reaction in step (b) is carried out in the second solvent; Preferably, the second solvent includes at least one of toluene and chloroform.

5. The preparation method according to claim 1, characterized in that, The reaction temperature in step (b) is 60-80℃ and the reaction time is 2-3h.

6. The preparation method according to claim 1, characterized in that, A third-generation Grubb catalyst was also added to the reaction in step (c); Preferably, the molar ratio of the hydrophilic monomer, the hydrophobic monomer, and the third-generation Grubb catalyst is 10-100:10-100:

1.

7. The preparation method according to claim 1, characterized in that, The reaction temperature in step (c) is 0-25℃, and the reaction time is 0.5-2.5h.

8. The preparation method according to claim 1, characterized in that, It also includes step (d): dispersing the photoresponsive brush-like macromolecular emulsifier obtained in step (c) in a third solvent and then mechanically dispersing it to obtain an oil-in-water emulsion; The oil-in-water emulsion is irradiated with ultraviolet light, and after the ultraviolet light is removed, it is mechanically dispersed to obtain an oil-in-water emulsion.

9. The preparation method according to claim 8, characterized in that, In step (d), the dispersion concentration of the photoresponsive brush-like macromolecular emulsifier in the third solvent is 0.05-0.2 wt%; Preferably, the third solvent is a mixture of toluene and water.

10. The photoresponsive brush-like macromolecular emulsifier prepared by the preparation method according to any one of claims 1-9.

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