A novel polyelectrolyte brush, its preparation method and application

Abstract

This invention provides a novel polyelectrolyte brush, its preparation method, and its application. A nanospherical polyelectrolyte brush with a brush-like structure is prepared by grafting polyelectrolyte chains with scale-inhibiting functional groups onto the surface of a photoinitiator HMEM core via photoemulsion polymerization. This spherical polyelectrolyte brush features a high graft density of polyelectrolyte chains, controllable size, good stability, and good dispersibility in water. It can effectively reduce membrane clogging caused by inorganic salt fouling during membrane water treatment, thus preventing decreased treatment efficiency and increased energy consumption.

Description

Technical Field

[0001] This invention belongs to the technical field of polymer preparation methods and their applications. Specifically, it relates to a novel polyelectrolyte brush, its preparation method, and its application. Background Technology

[0002] When charged polymer chains are densely distributed on the surface of a nanomatrix with one end fixed, the free ends of the polymer chains extend outward due to volume repulsion and electrostatic repulsion, forming a structure called a nanopolyelectrolyte brush. In 1999, the first inventor of this application first achieved the preparation of nanospherical polyelectrolyte brushes (hereinafter referred to as nanobrushes) by photoemulsion polymerization in Germany. This involved attaching a photoinitiator to the core surface and initiating in-situ polymerization of monomers under ultraviolet light to form spherical polyelectrolyte brushes. Using this method, spherical polyacrylic acid brushes and sodium polyvinylbenzenesulfonate brushes with sizes of 100-200 nanometers were synthesized (Macromolecules 1999, 32, 6043). In 2008, the applicant of this application developed a new thermal initiator, expanding the synthesis method of nanobrushes (publication numbers CN101381421A and CN101381435B). In 2011, the applicant used polybutadiene emulsion as a nano core and initiated the polymerization of polyelectrolyte monomers on the surface of the nano matrix to prepare a novel spherical polyelectrolyte brush with nanoscale dimensions (publication number CN102516463B).

[0003] To address the problem of water scarcity, reverse osmosis membrane treatment technology has developed rapidly. Membrane antiscalants are widely used in this field because they can slow down scaling on membrane modules and improve water purification efficiency. Common membrane antiscalants include phosphates, anionic polymers, cationic polymers, and green antiscalants. They are generally believed to inhibit or mitigate scale formation through chelation, dispersion, lattice distortion, or threshold effects. Dendritic polymer membrane antiscalants have excellent scale inhibition performance, and spherical polyelectrolyte brushes, with similar structures, are also emerging as brush-shaped polymer membrane antiscalants in the membrane treatment field. This invention provides a novel polyelectrolyte brush that can be used as a membrane antiscalant. Summary of the Invention

[0004] In view of the above problems, the present invention provides a novel polyelectrolyte brush, its preparation method and application, which realizes the preparation of polyelectrolyte brushes with excellent scale inhibition performance with fewer preparation steps.

[0005] To achieve the above objectives, the technical solution of the present invention is as follows:

[0006] A method for preparing a polyelectrolyte brush includes the following steps:

[0007] (1) Photoinitiator HMEM, water-soluble thermal initiator and surfactant are added to the reaction apparatus and polymerized at 60-80°C under nitrogen protection. After dialysis purification, PHMEM core emulsion is obtained.

[0008] (2) Take a certain amount of the PHMEM core emulsion and water-soluble monomer obtained in step (1) and add them to the photoreactor. Dilute with water and ensure that the photoreactor is an oxygen-free environment. Turn on the high-pressure ultraviolet mercury lamp and carry out the photoreaction at room temperature for 1.5 to 4 hours. After the reaction, the emulsion obtained is purified by dialysis to obtain the final product polyelectrolyte brush PHMEM-PSS SPB.

[0009] The photoinitiator HMEM is 2-[p-(2-hydroxy-2-methylphenylacetone)]-ethylene glycol-acrylate, and its structural formula is:

[0010]

[0011] The photoinitiator HMEM can be prepared in-house using the method disclosed in the published patent application CN101630555A.

[0012] The present invention is further configured such that, in step (1), the water-soluble thermal initiator is selected from at least one of potassium persulfate (KPS) and 2,2-azo(2-methylpropylamidine) dihydrochloride ((AIBA)).

[0013] The present invention is further configured such that, in step (1), the surfactant is selected from at least one of sodium dodecyl sulfate, sodium dodecylbenzene sulfonate, and Triton X-100.

[0014] The present invention is further configured such that, in step (1), the mass ratio of the water-soluble thermal initiator to the surfactant is 1:(2-4), and the total mass of the water-soluble thermal initiator and the surfactant accounts for 4% to 10% of the total mass of the photoinitiator, the water-soluble thermal initiator and the surfactant.

[0015] The present invention is further configured such that, in step (1), the polymerization reaction time is 0.5 to 3.5 h.

[0016] The present invention is further configured such that, in step (2), the water-soluble monomer is acrylic acid.

[0017] The present invention is further configured such that, in step (2), the water-soluble monomer is added at a molar ratio of 1:(1-3) of the PHMEM core emulsion and the water-soluble monomer, wherein the molar mass of the PHMEM core is expressed as the molar mass of HMEM. It should be noted that, since the amount of water-soluble initiator and surfactant added during the preparation of the PHMEM core is much lower than the amount of HMEM, the proportion of polyelectrolyte chains grafted onto the surface of the obtained PHMEM core is relatively small. Therefore, when subsequently estimating the amount of water-soluble monomer added, the molar mass of the PHMEM core is expressed as the molar mass of HMEM.

[0018] The present invention is further configured such that the dialysis purification in steps (1) and (2) is carried out using dialysis bags with a molecular weight cutoff of 8k-14k.

[0019] This invention provides a polyelectrolyte brush prepared using the above-described method.

[0020] The present invention is further configured such that the particle size of the polyelectrolyte brush is 100-250 nm.

[0021] The present invention is further configured such that the size of the PHMEM core of the polyelectrolyte brush is 20-70 nm.

[0022] The present invention is further configured such that the polyelectrolyte brush is monodisperse in aqueous solution and has a dispersibility index of less than 0.1.

[0023] The present invention also provides an application of the above-mentioned polyelectrolyte brush in a membrane antiscalant.

[0024] Compared with the prior art, the present invention has the following beneficial effects:

[0025] (1) The preparation method of the present invention significantly reduces the core size of the nanosphere polyelectrolyte brush, thereby reducing the overall size of the polyelectrolyte brush. This can avoid membrane blockage during actual membrane scale inhibition, and the size of the obtained polyelectrolyte brush is controllable.

[0026] (2) The polyelectrolyte brush prepared by the present invention has a significant effect on inhibiting calcium carbonate scale, and can change the morphology of calcium carbonate crystals and play a dispersing role. This discovery broadens the application prospects of nano-spherical polyelectrolyte brushes in the field of water treatment. Attached Figure Description

[0027] Figure 1 The turbidity titration curves are for the polyelectrolyte brushes prepared in Examples 1 and 2.

[0028] Figure 2 The XRD characterization results of the CaCO3 crystal form in the turbidity titration experiment of the polyelectrolyte brush prepared in Example 1, when the scale inhibitor concentration was 5 ppm.

[0029] Figure 3 This is a SEM image showing the changes in the morphology of CaCO3 crystals in the blank control group when no scale inhibitor was added.

[0030] Figure 4 The image shows the SEM image of the morphological changes of CaCO3 crystals when the scale inhibitor concentration is 5 ppm in the polyelectrolyte brush turbidity titration experiment in Example 1.

[0031] Figure 5 The turbidity titration curves are for the membrane antiscalants prepared in Example 1 and Comparative Example 1.

[0032] Figure 6 The following figures show the changes in the morphology of calcium carbonate crystals after adding 5 ppm of polyacrylic acid scale inhibitor, PWT-200 commercial scale inhibitor, PS-PAA (Comparative Example 1), and PHMEM-PSS (Comparative Example 2): (a) PAA, (b) PWT, (c) PS-PAA, (d) PHMEM-PSS.

[0033] Figure 7 The results of the stability test of the polyelectrolyte brush prepared in Example 2 under room temperature storage conditions are shown. The left vertical axis represents the particle size, and the right vertical axis represents the dispersibility index. Detailed Implementation

[0034] The present invention will now be described in detail with reference to specific embodiments and accompanying drawings. It should be understood that the described embodiments are only some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of the present invention.

[0035] In the technical solution of this invention, the photoinitiator HMEM used is obtained in-house and is prepared by the method disclosed in patent CN200910053204.0 (Method for preparing magnetic particles using nanospherical polyelectrolyte brushes as microreactors).

[0036] Example 1

[0037] A method for preparing a polyelectrolyte brush includes the following steps:

[0038] (1) Weigh 0.12 g of potassium persulfate (KPS) initiator and 0.48 g of sodium dodecyl sulfate surfactant, dissolve them in 20 mL of deionized water, and then add them to a 250 mL three-necked flask. Stir and pre-emulsify for 30 min at a stirring speed of 280 rad / min. Weigh 7.94 g of photoinitiator HMEM and add it to the three-necked flask, then add 35 mL of deionized water and mix. After purging the system with nitrogen 3-5 times, heat to 70 °C and carry out emulsion polymerization for 2 h.

[0039] The resulting emulsion was purified by dialysis in ultrapure water using a dialysis bag with a molecular weight cutoff of 8k–14k until the conductivity of the external ultrapure water remained constant, thus obtaining the purified PHMEM core emulsion. The solid content of the PHMEM core emulsion was measured to be 2.81%, and dynamic light scattering characterization revealed a particle size of 36 nm and a dispersibility of 0.031.

[0040] (2) Take 12g of the PHMEM core emulsion obtained in step (1) into a photoreactor, and add about 0.083g of acrylic acid (AA) at a molar ratio of 1:1 with the PHMEM core emulsion. Then add 55mL of deionized water and dilute the system to about 0.5% with deionized water. Then purge the system with nitrogen 3-5 times to ensure an oxygen-free environment. Turn on the high-pressure ultraviolet mercury lamp and carry out the photoreaction for 2 hours under gentle stirring with a magnetic stirrer and at room temperature. A yellow emulsion is obtained after the reaction is completed.

[0041] The yellow emulsion was then purified by dialysis in ultrapure water using a dialysis bag with a molecular weight cutoff of 8k–14k to obtain the final product, nanosphere polyelectrolyte brush PHMEM-PAA SPB. The particle size was measured to be 115nm and the dispersibility was 0.072 using dynamic light scattering.

[0042] The scale inhibition ability of the nano-spherical polyelectrolyte brush PHMEM-PAA SPB prepared in Example 1 as a scale inhibitor was investigated by turbidity titration. The steps are as follows:

[0043] S1. Prepare 0.009 mol / L CaCl2 solution and 0.30 mol / L NaHCO3 solution for later use;

[0044] S2. Quantitatively prepare scale inhibitor aqueous solutions with concentrations of 1 mg / mL, 5 mg / mL, and 10 mg / mL using the nanospherical polyelectrolyte brush obtained in Example 1.

[0045] S3. Take 149.25 mL of 0.009 mol / L CaCl2 solution and 0.75 mL of 1 mg / mL scale inhibitor aqueous solution, totaling 150 mL, into an Erlenmeyer flask to make the scale inhibitor concentration in the system 5 ppm; add NaHCO3 solution dropwise to the system and use a Brinkmann PC 950 colorimeter (420 nm filter, 2 cm optical probe) to detect the change in the transmittance T% of the system.

[0046] S4. Take 149.25 mL of 0.009 mol / L CaCl2 solution and 0.75 mL of 5 mg / mL scale inhibitor solution in an Erlenmeyer flask to make the scale inhibitor concentration in the system 10 ppm. Add NaHCO3 solution dropwise to the system and use a Brinkmann PC 950 colorimeter (420 nm filter, 2 cm optical probe) to detect the change in the transmittance T% of the system.

[0047] S5. Take 149.25 mL of 0.009 mol / L CaCl2 solution and 0.75 mL of 10 mg / mL scale inhibitor solution in an Erlenmeyer flask to make the scale inhibitor concentration in the system 20 ppm. Add NaHCO3 solution dropwise to the system and use a Brinkmann PC 950 colorimeter (420 nm filter, 2 cm optical probe) to detect the change in the transmittance T% of the system.

[0048] Steps S3 to S5 above respectively examine the scale inhibition effect of adding different concentrations of scale inhibitor to the system. The results show that when the scale inhibitor concentration in the system is 5 ppm in step S3, as... Figure 1 As shown, when the volume of NaHCO3 solution was increased to 19 mL, the transmittance exhibited a sudden change, demonstrating a significant scale inhibition ability compared to the blank control group. At this concentration, the maximum scale inhibition capacity of the scale inhibitor was 570 mg / L CaCO3. For a scale inhibitor concentration of 10 ppm, when the volume of NaHCO3 solution was increased to 25 mL, the transmittance exhibited a sudden change. At this concentration, the maximum scale inhibition capacity of the scale inhibitor was 750 mg / L CaCO3. For a scale inhibitor concentration of 20 ppm, when the volume of NaHCO3 solution was increased to 34 mL, the transmittance exhibited a sudden change. At this concentration, the maximum scale inhibition capacity of the scale inhibitor was 1020 mg / L CaCO3.

[0049] In the turbidity titration experiment with a scale inhibitor concentration of 5 ppm, scanning electron microscopy and XRD were used to observe the changes in the morphology of CaCO3 crystals before and after the addition of the scale inhibitor. Figures 2-4As can be seen, after adding PHMEM-PAA, calcium carbonate changes from calcite to aragonite, with a significantly reduced size and a smoother surface. This change in crystal shape is not conducive to the adsorption of fouling on the pipe wall, and the fouling is more easily washed away by the water flow, thus delaying scaling on the membrane surface. Therefore, the polyelectrolyte brush provided by this invention affects the nucleation and distortion of calcium carbonate crystals in the fouling, which is also a possible reason for delaying fouling formation.

[0050] In addition, the stability of the prepared polyelectrolyte brush samples was observed: the prepared spherical polyelectrolyte brush samples were placed in glass sample bottles and stored at room temperature. Samples were taken at different time intervals, and their size and dispersibility changes were measured by dynamic light scattering to monitor the stability of the samples. The polyelectrolyte brush samples prepared in this embodiment showed stable size and no significant change in dispersibility within 60 days of storage, indicating good stability.

[0051] Example 2

[0052] A method for preparing a polyelectrolyte brush includes the following steps:

[0053] (1) Weigh 0.12 g of potassium persulfate (KPS) initiator and 0.48 g of sodium dodecyl sulfate surfactant, dissolve them in 20 mL of deionized water, and then add them to a 250 mL three-necked flask. Stir and pre-emulsify for 30 min at a stirring speed of 280 rad / min. Weigh 7.94 g of photoinitiator HMEM and add it to the three-necked flask, then add 35 mL of deionized water and mix. After purging the system with nitrogen 3-5 times, heat to 70 °C and carry out emulsion polymerization for 2 h.

[0054] The resulting emulsion was purified by dialysis in ultrapure water using a dialysis bag with a molecular weight cutoff of 8k–14k until the conductivity of the external ultrapure water remained constant, thus obtaining the purified PHMEM core emulsion. The solid content of the PHMEM core emulsion was measured to be 2.81%, and dynamic light scattering characterization revealed a particle size of 36 nm and a dispersibility of 0.031.

[0055] (2) Take 12g of the PHMEM core emulsion obtained in step (1) into a photoreactor, and add 0.166g of acrylic acid according to the molar ratio of PHMEM core emulsion to acrylic acid of 1:2. Then add 55mL of deionized water and dilute the system to about 0.5% with deionized water. Then purge the system with nitrogen 3-5 times to ensure an oxygen-free environment. Turn on the high-pressure ultraviolet mercury lamp, and use the same magnetic stirrer as in Example 1 to gently stir and carry out the photoreaction at room temperature for 2 hours. After cooling, a yellow emulsion is obtained.

[0056] The yellow emulsion was then purified by dialysis in ultrapure water using a dialysis bag with a molecular weight cutoff of 8k–14k to obtain the final product, nanosphere polyelectrolyte brush PHMEM-PAA SPB. The particle size was measured to be 148nm and the dispersibility was 0.050 using dynamic light scattering.

[0057] The nanospherical polyelectrolyte brush prepared in Example 2 was subjected to the same turbidity titration experiment as in Example 1 to test its scale inhibition ability. The results are as follows: Figure 1 As shown, in the turbidity titration experiment, when the scale inhibitor concentration in the system is 5 ppm, V NaHCO3 At a density of 12.5 mL, the transmittance undergoes a sudden change.

[0058] The stability results of the polyelectrolyte brush prepared in this embodiment are as follows: Figure 7 As shown, under 60 days of room temperature storage conditions, the sample exhibited good stability, size stability, and no significant change in dispersibility.

[0059] Example 3

[0060] A method for preparing a polyelectrolyte brush includes the following steps:

[0061] (1) Weigh 0.12 g of potassium persulfate (KPS) initiator and 0.25 g of sodium dodecyl sulfate surfactant, dissolve them in 20 mL of deionized water, and then add them to a 250 mL three-necked flask. Stir and pre-emulsify for 30 min at a stirring speed of 280 rad / min. Weigh 7.94 g of photoinitiator HMEM and add it to the three-necked flask, then add 35 mL of deionized water and mix. After purging the system with nitrogen 3-5 times, heat to 70 °C and carry out emulsion polymerization for 2 h.

[0062] The resulting emulsion was purified by dialysis in ultrapure water using a dialysis bag with a molecular weight cutoff of 8k–14k until the conductivity of the external ultrapure water remained constant, thus obtaining the purified PHMEM core emulsion. The solid content of the PHMEM core emulsion was measured to be 2.64%, and dynamic light scattering characterization revealed a particle size of 50 nm and a dispersibility of 0.013.

[0063] (2) Take 12g of the PHMEM core emulsion obtained in step (1) into a photoreactor, and add about 0.156g of acrylic acid according to the molar ratio of PHMEM core emulsion to acrylic acid of 1:2. Then add 53mL of deionized water and dilute the system to about 0.5% with deionized water. Then purge the system with nitrogen 3-5 times to ensure an oxygen-free environment. Turn on the high-pressure ultraviolet mercury lamp, and use the same magnetic stirrer as in Example 1 to gently stir and carry out the photoreaction at room temperature for 2 hours. After cooling, a yellow emulsion is obtained.

[0064] The yellow emulsion was then purified by dialysis in ultrapure water using a dialysis bag with a molecular weight cutoff of 8k–14k to obtain the final product, nanosphere polyelectrolyte brush PHMEM-PAA SPB. The particle size was measured to be 134nm and the dispersibility was 0.089 using dynamic light scattering.

[0065] The nanospherical polyelectrolyte brush prepared in Example 3 was subjected to the same turbidity titration experiment as in Example 1 to test its scale inhibition ability. In the turbidity titration experiment, when the scale inhibitor concentration in the system was 5 ppm, the turbidity abrupt change point remained basically unchanged compared with Example 2, indicating that the scale inhibition performance did not change significantly. The nanospherical polyelectrolyte brush prepared in this example showed good stability. Under 60 days of room temperature storage conditions, the sample showed good stability, dimensional stability, and no significant change in dispersibility.

[0066] Example 4

[0067] A method for preparing a polyelectrolyte brush includes the following steps:

[0068] (1) Weigh 0.12 g of potassium persulfate (KPS) initiator and 0.36 g of sodium dodecyl sulfate surfactant, dissolve them in 20 mL of deionized water, and then add them to a 250 mL three-necked flask. Stir and pre-emulsify for 30 min at a stirring speed of 280 rad / min. Weigh 7.94 g of photoinitiator HMEM and add it to the three-necked flask, then add 35 mL of deionized water and mix. After purging the system with nitrogen 3-5 times, heat to 70 °C and carry out emulsion polymerization for 2 h.

[0069] The resulting emulsion was purified by dialysis in ultrapure water using a dialysis bag with a molecular weight cutoff of 8k–14k until the conductivity of the external ultrapure water remained constant, thus obtaining the purified PHMEM core emulsion. The solid content of the PHMEM core emulsion was measured to be 2.13%, and dynamic light scattering characterization revealed a particle size of 40 nm and a dispersibility of 0.025.

[0070] (2) Take 12g of the PHMEM core emulsion obtained in step (1) into a photoreactor, and add about 0.063g of acrylic acid (AA) at a molar ratio of 1:1 with the PHMEM core emulsion. Then add 40mL of deionized water and dilute the system to about 0.5% with deionized water. Then purge the system with nitrogen 3-5 times to ensure an oxygen-free environment. Turn on the high-pressure ultraviolet mercury lamp, and gently stir with the same magnetic stirrer as in Example 1 at room temperature for 2.5h. After cooling, a yellow emulsion is obtained.

[0071] The yellow emulsion was then purified by dialysis in ultrapure water using a dialysis bag with a molecular weight cutoff of 8k–14k to obtain the final product, nanosphere polyelectrolyte brush PHMEM-PAA SPB. The particle size was measured to be 167nm and the dispersibility was 0.154 using dynamic light scattering.

[0072] The scale inhibition ability of the nanospherical polyelectrolyte brush prepared in Example 4 was tested by the same turbidity titration experiment as in Example 1. In the turbidity titration experiment, when the scale inhibitor concentration in the system was 5 ppm, V NaHCO3 At 25 mL, the transmittance changes abruptly.

[0073] The nanosphere polyelectrolyte brushes prepared in this embodiment exhibit good stability. Under 60 days of room temperature storage conditions, the samples showed good stability, size stability, and no significant change in dispersibility.

[0074] Example 5

[0075] A method for preparing a polyelectrolyte brush includes the following steps:

[0076] (1) Weigh 0.12 g of potassium persulfate (KPS) initiator and 0.36 g of sodium dodecyl sulfate surfactant, dissolve them in 20 mL of deionized water, and then add them to a 250 mL three-necked flask. Stir and pre-emulsify for 30 min at a stirring speed of 280 rad / min. Weigh 7.94 g of photoinitiator HMEM and add it to the three-necked flask, then add 35 mL of deionized water and mix. After purging the system with nitrogen 3-5 times, heat it to 70 °C and carry out emulsion polymerization for 3 h.

[0077] The resulting emulsion was purified by dialysis in ultrapure water using a dialysis bag with a molecular weight cutoff of 8k–14k until the conductivity of the external ultrapure water remained constant, thus obtaining the purified PHMEM core emulsion. The solid content of the PHMEM core emulsion was measured to be 2.16%, and dynamic light scattering characterization revealed a particle size of 43 nm and a dispersibility of 0.026.

[0078] (2) Take 12g of the PHMEM core emulsion obtained in step (1) into a photoreactor, and add 0.128g of acrylic acid according to the molar ratio of PHMEM core emulsion to acrylic acid of 1:2. Then add 40mL of deionized water and dilute the system to about 0.5% with deionized water. Then purge the system with nitrogen 3-5 times to ensure an oxygen-free environment. Turn on the high-pressure ultraviolet mercury lamp, and use the same magnetic stirrer as in Example 1 to gently stir and carry out the photoreaction at room temperature for 2.5h. After cooling, a yellow emulsion is obtained.

[0079] The yellow emulsion was then purified by dialysis in ultrapure water using a dialysis bag with a molecular weight cutoff of 8k–14k to obtain the final product, nanosphere polyelectrolyte brush PHMEM-PAA SPB. The particle size was measured to be 204nm and the dispersibility was 0.110 using dynamic light scattering.

[0080] The scale inhibition ability of the nanospherical polyelectrolyte brush prepared in Example 5 was tested by the same turbidity titration experiment as in Example 1. In the turbidity titration experiment, when the scale inhibitor concentration in the system was 5 ppm, compared with Example 4, the turbidity mutation point shifted forward by V. NaHCO3 =16-17 mL, scale inhibition performance decreased. The nanospherical polyelectrolyte brush prepared in this example has good stability. Under 60 days of room temperature storage conditions, the sample has good stability, size stability and no significant change in dispersibility.

[0081] Example 6

[0082] A method for preparing a polyelectrolyte brush includes the following steps:

[0083] (1) Weigh 0.12 g of potassium persulfate (KPS) initiator and 0.36 g of sodium dodecyl sulfate surfactant, dissolve them in 20 mL of deionized water, and then add them to a 250 mL three-necked flask. Stir and pre-emulsify for 30 min at a stirring speed of 280 rad / min. Weigh 7.94 g of photoinitiator HMEM and add it to the three-necked flask, then add 35 mL of deionized water and mix. After purging the system with nitrogen 3-5 times, heat it to 70 °C and carry out emulsion polymerization for 2 h.

[0084] The resulting emulsion was purified by dialysis in ultrapure water using a dialysis bag with a molecular weight cutoff of 8k–14k until the conductivity of the external ultrapure water remained constant, thus obtaining the purified PHMEM core emulsion. The solid content of the PHMEM core emulsion was measured to be 2.13%, and dynamic light scattering characterization revealed a particle size of 40 nm and a dispersibility of 0.025.

[0085] (2) Take 12g of the PHMEM core emulsion obtained in step (1) into a photoreactor, and add about 0.158g of acrylic acid according to the molar ratio of PHMEM core emulsion to acrylic acid of 1:2.5. Then add 40mL of deionized water and dilute the system to about 0.5% with deionized water. Then purge the system with nitrogen 3-5 times to ensure an oxygen-free environment. Turn on the high-pressure ultraviolet mercury lamp, and use the same magnetic stirrer as in Example 1 to gently stir and carry out the photoreaction at room temperature for 2.0h. After cooling, a yellow emulsion is obtained.

[0086] The yellow emulsion was then purified by dialysis in ultrapure water using a dialysis bag with a molecular weight cutoff of 8k–14k to obtain the final product, nanosphere polyelectrolyte brush PHMEM-PAA SPB. The particle size was measured to be 220.1 nm and the dispersibility was 0.068 using dynamic light scattering.

[0087] The scale inhibition ability of the nanospherical polyelectrolyte brush prepared in Example 7 was tested by the same turbidity titration experiment as in Example 1. In the turbidity titration experiment, when the scale inhibitor concentration in the system was 5 ppm, the turbidity abruptly changed at V NaHCO3 =16.5~17.5mL. The nanosphere polyelectrolyte brushes prepared in this example have good stability. Under 60 days of room temperature storage conditions, the samples showed good stability, size stability, and no significant change in dispersibility.

[0088] Example 7

[0089] A method for preparing a polyelectrolyte brush includes the following steps:

[0090] (1) Weigh 0.12 g of potassium persulfate (KPS) initiator and 0.36 g of sodium dodecyl sulfate surfactant, dissolve them in 20 mL of deionized water, and then add them to a 250 mL three-necked flask. Stir and pre-emulsify for 30 min at a stirring speed of 280 rad / min. Weigh 7.94 g of photoinitiator HMEM and add it to the three-necked flask, then add 35 mL of deionized water and mix. After purging the system with nitrogen 3-5 times, heat it to 70 °C and carry out emulsion polymerization for 2 h.

[0091] The resulting emulsion was purified by dialysis in ultrapure water using a dialysis bag with a molecular weight cutoff of 8k–14k until the conductivity of the external ultrapure water remained constant, thus obtaining the purified PHMEM core emulsion. The solid content of the PHMEM core emulsion was measured to be 2.13%, and dynamic light scattering characterization revealed a particle size of 40 nm and a dispersibility of 0.025.

[0092] (2) Take 12g of the PHMEM core emulsion obtained in step (1) into a photoreactor, and add 0.189g of acrylic acid according to the molar ratio of PHMEM core emulsion to acrylic acid of 1:3. Then add 40mL of deionized water and dilute the system to about 0.5% with deionized water. Then purge the system with nitrogen 3-5 times to ensure an oxygen-free environment. Turn on the high-pressure ultraviolet mercury lamp, and use the same magnetic stirrer as in Example 1 to gently stir and carry out the photoreaction at room temperature for 2.0h. After cooling, a yellow emulsion is obtained.

[0093] The yellow emulsion was then purified by dialysis in ultrapure water using a dialysis bag with a molecular weight cutoff of 8k–14k to obtain the final product, nanosphere polyelectrolyte brush PHMEM-PAA SPB. The particle size was measured to be 252.4 nm and the dispersibility was 0.125 using dynamic light scattering.

[0094] The scale inhibition ability of the nanospherical polyelectrolyte brush prepared in Example 8 was tested by the same turbidity titration experiment as in Example 1. In the turbidity titration experiment, when the scale inhibitor concentration in the system was 5 ppm, the turbidity abrupt change point shifted later, V NaHCO3 Approximately 18 mL.

[0095] The nanospherical polyelectrolyte brush prepared in this embodiment produced a significant amount of precipitation after 30 days of storage at room temperature. The sample exhibited relatively poor stability.

[0096] Comparative Example 1

[0097] A method for preparing a polyelectrolyte brush includes the following steps:

[0098] (1) Weigh 0.6 g of potassium persulfate (KPS) initiator and 0.36 g of sodium dodecyl sulfate surfactant, dissolve them in 20 mL of deionized water, and then add them to a 250 mL three-necked flask. Stir and pre-emulsify for 30 min at a stirring speed of 300 rad / min. Weigh 8 g of styrene (St) and add it to the three-necked flask (MSt = 104.15 g / mol), then add 150 mL of deionized water and mix. After purging the system with nitrogen 3-5 times, raise the temperature to 80 °C in three stages for emulsion polymerization for 1.5 h. After cooling to 70 °C, weigh 0.8 g of photoinitiator HMEM and slowly add it dropwise to the reaction system through a constant pressure dropping funnel at a rate of 6-7 s / d. After the addition is completed, continue the reaction for 1 h.

[0099] The emulsion obtained after the reaction was purified by dialysis in ultrapure water using a dialysis bag with a molecular weight cutoff of 8k–14k. The purification was continued until the conductivity of the external ultrapure water remained constant, yielding a purified white emulsion. The solid content of the emulsion was measured to be 3.25%, and dynamic light scattering characterization revealed a particle size of 94 nm and a dispersibility of 0.024.

[0100] (2) Take 12g of the emulsion obtained in step (1) into a photoreactor, and add about 0.270g of acrylic acid (AA) at a molar ratio of 1:1 to the emulsion. The molar mass of the emulsion is calculated based on styrene. Then add 66mL of deionized water and dilute the system to about 0.5% with deionized water. Then purge the system with nitrogen 3-5 times to ensure an oxygen-free environment. Turn on the high-pressure ultraviolet mercury lamp, and use the same magnetic stirrer as in Example 1 to gently stir and carry out the photoreaction at room temperature for 2.0h. After cooling, a white emulsion is obtained.

[0101] The yellow emulsion was then purified by dialysis in ultrapure water using a dialysis bag with a molecular weight cutoff of 8k–14k to obtain the final product, nanosphere polyelectrolyte brush PS-PAA SPB. The particle size was measured to be 206nm and the dispersibility was 0.032 using dynamic light scattering.

[0102] The scale inhibition ability of the nano-spherical polyelectrolyte brush PS-PAA prepared in Comparative Example 1 was tested by the same turbidity titration experiment as described above. Figure 5 As shown, in the turbidity titration experiment, when the scale inhibitor concentration in the system is 5 ppm, V NaHCO3 At a concentration of 15 mL, the transmittance undergoes a sudden change. At this concentration, the morphology of calcium carbonate crystals is as follows: Figure 6 As shown in (c), PS-PAA as a scale inhibitor can cause the square crystals of calcium carbonate to deform, but calcite is still the main component.

[0103] Comparative Example 2

[0104] A method for preparing a polyelectrolyte brush includes the following steps:

[0105] (1) Weigh 0.12 g of potassium persulfate (KPS) initiator and 0.48 g of sodium dodecyl sulfate surfactant, dissolve them in 20 mL of deionized water, and then add them to a 250 mL three-necked flask. Stir and pre-emulsify for 30 min at a stirring speed of 280 rad / min. Weigh 7.94 g of photoinitiator HMEM and add it to the three-necked flask, then add 35 mL of deionized water and mix. After purging the system with nitrogen 3-5 times, heat to 70 °C and carry out emulsion polymerization for 2 h.

[0106] The resulting emulsion was purified by dialysis in ultrapure water using a dialysis bag with a molecular weight cutoff of 8k–14k until the conductivity of the external ultrapure water remained constant, thus obtaining the purified PHMEM core emulsion. The solid content of the PHMEM core emulsion was measured to be 2.13%, and dynamic light scattering characterization revealed a particle size of 40 nm and a dispersibility of 0.026.

[0107] (2) Take 12g of the PHMEM core emulsion obtained in step (1) into the photoreactor, and add 0.18g of sodium p-styrene sulfonate (SS, M) at a molar ratio of 1:1 with the PHMEM core emulsion. SS =206.19 g / mol), then add 40 mL of deionized water to dilute the system to about 0.5%; then purge the system with nitrogen 3-5 times to ensure an oxygen-free environment, turn on the high-pressure ultraviolet mercury lamp, and gently stir with the same magnetic stirrer as in Example 1 at room temperature for 2.0 h. After cooling, a yellow emulsion is obtained.

[0108] The yellow emulsion was then purified by dialysis in ultrapure water using a dialysis bag with a molecular weight cutoff of 8k–14k to obtain the final product, nanosphere polyelectrolyte brush PHMEM-PSS SPB. The particle size was measured to be 148nm and the dispersibility was 0.062 using dynamic light scattering.

[0109] The scale inhibition ability of the nanospherical polyelectrolyte brush prepared in Comparative Example 2 was tested by the same turbidity titration experiment as described above. In the turbidity titration experiment, when the scale inhibitor concentration in the system was 5 ppm, adding about 6-7 mL of sodium bicarbonate caused precipitation to occur in the system. At this concentration, the morphology of calcium carbonate crystals was as follows. Figure 6 As shown in (d), when PHMEM-PSS is used as a scale inhibitor, the crystal morphology of calcium carbonate remains basically unchanged.

[0110] Comparative Example 3

[0111] A method for preparing a polyelectrolyte brush includes the following steps:

[0112] (1) Weigh 0.12 g of potassium persulfate (KPS) initiator and 0.48 g of sodium dodecyl sulfate surfactant, dissolve them in 20 mL of deionized water, and then add them to a 250 mL three-necked flask. Stir and pre-emulsify for 30 min at a stirring speed of 280 rad / min. Weigh 7.94 g of photoinitiator HMEM and add it to the three-necked flask, then add 35 mL of deionized water and mix. After purging the system with nitrogen 3-5 times, heat to 70 °C and carry out emulsion polymerization for 2 h.

[0113] The resulting emulsion was purified by dialysis in ultrapure water using a dialysis bag with a molecular weight cutoff of 8k–14k until the conductivity of the external ultrapure water remained constant, thus obtaining the purified PHMEM core emulsion. The solid content of the PHMEM core emulsion was measured to be 2.13%, and dynamic light scattering characterization revealed a particle size of 40 nm and a dispersibility of 0.026.

[0114] (2) Take 12g of the PHMEM core emulsion obtained in step (1) into a photoreactor, and add 0.36g of sodium p-styrene sulfonate according to the molar ratio of PHMEM core emulsion to sodium p-styrene sulfonate of 1:2. Then add 40mL of deionized water and dilute the system to about 0.5% with deionized water. Then purge the system with nitrogen 3-5 times to ensure an oxygen-free environment. Turn on the high-pressure ultraviolet mercury lamp, and use the same magnetic stirrer as in Example 1 to gently stir and carry out the photoreaction at room temperature for 2.0h. After cooling, a yellow emulsion is obtained.

[0115] The yellow emulsion was then purified by dialysis in ultrapure water using a dialysis bag with a molecular weight cutoff of 8k–14k to obtain the final product, nanosphere polyelectrolyte brush PHMEM-PAA SPB. The particle size was measured to be 208nm and the dispersibility was 0.054 using dynamic light scattering.

[0116] The same turbidity titration experiment was performed on the nanosphere polyelectrolyte brush prepared in Comparative Example 3 to test its scale inhibition ability. In the turbidity titration experiment, when the scale inhibitor concentration in the system was 5 ppm, about 7 mL of sodium bicarbonate was added and a precipitate was generated in the system.

[0117] control group

[0118] The scale inhibition capabilities of commonly used polyacrylic acid scale inhibitors (PAA) and commercially available PWT-200 scale inhibitors were investigated using the same turbidity titration experiment. After adding scale inhibitors at a concentration of 5 ppm, the morphologies of calcium carbonate crystals were as follows: Figure 6 As shown in (a) and (b), Figure 6 The results showed that the change in the crystal morphology of calcium carbonate was not significant after using PAA and PWT scale inhibitors.

[0119] The above embodiments are only for illustrating the technical concept and features of the present invention, and are intended to enable those skilled in the art to understand the content of the present invention and implement it accordingly. They should not be construed as limiting the scope of protection of the present invention. All equivalent transformations or modifications made in accordance with the spirit and essence of the present invention should be covered within the scope of protection of the present invention.

Claims

1. A method for preparing a polyelectrolyte brush, characterized in that, Includes the following steps: (1) Photoinitiator HMEM, water-soluble thermal initiator and surfactant are added to the reaction apparatus and polymerized at 60-80°C under nitrogen protection. After dialysis purification, PHMEM core emulsion is obtained. (2) Take a certain amount of the PHMEM core emulsion and water-soluble monomer obtained in step (1) and add them to the photoreactor. Dilute with water and ensure that the photoreactor is an oxygen-free environment. Turn on the high-pressure ultraviolet mercury lamp and carry out the photoreaction at room temperature for 1.5 to 4 hours. After the reaction, the emulsion obtained is purified by dialysis to obtain the final product polyelectrolyte brush PHMEM-PSS SPB.

2. The method for preparing a polyelectrolyte brush according to claim 1, characterized in that, In step (1), the water-soluble thermal initiator is selected from at least one of potassium persulfate and 2,2-azo(2-methylpropylamidine) dihydrochloride; the surfactant is selected from at least one of sodium dodecyl sulfate, sodium dodecylbenzene sulfonate, and Triton X-100.

3. The method for preparing a polyelectrolyte brush according to claim 1, characterized in that, In step (1), the mass ratio of the water-soluble thermal initiator to the surfactant is 1:(2-4), and the total mass of the water-soluble thermal initiator and the surfactant accounts for 4% to 10% of the total mass of the photoinitiator, the water-soluble thermal initiator and the surfactant.

4. The method for preparing a polyelectrolyte brush according to claim 1, characterized in that, In step (1), the polymerization reaction time is 0.5 to 3.5 h.

5. The method for preparing a polyelectrolyte brush according to claim 1, characterized in that, In step (2), the water-soluble monomer is acrylic acid.

6. The method for preparing a polyelectrolyte brush according to claim 1, characterized in that, In step (2), the water-soluble monomer is added at a molar ratio of 1:(1-3) of the PHMEM core emulsion and the water-soluble monomer, wherein the molar mass of the PHMEM core is expressed as the molar mass of HMEM.

7. The method for preparing a polyelectrolyte brush according to claim 1, characterized in that, In steps (1) and (2), dialysis purification was performed using dialysis bags with a molecular weight cutoff of 8k-14k.

8. A polyelectrolyte brush prepared by the preparation method according to any one of claims 1 to 7.

9. The polyelectrolyte brush according to claim 8, characterized in that, The polyelectrolyte brush has a particle size of 100–250 nm.

10. An application of the polyelectrolyte brush as described in claim 8 or 9, characterized in that, Used as a membrane scale inhibitor.

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