Ionic Polymer Nanowires with Cross-Linked Structures, Preparation Methods Thereof, and Applications

Abstract

The present disclosure provides an ionic polymer nanowire with a cross-linked structure, a preparation method thereof, and applications thereof. Among them, the method includes: adding a solventophilic polymer segment P, a monomer for forming a solventophobic segment, an initiator, and a cross-linking agent into a solvent, and performing in-situ cross-linking polymerization-induced self-assembly to prepare an ionic polymer nanowire with a cross-linked structure, wherein the solventophilic polymer segment P contains at least a part of an ionic polymer. The cross-linked ionic polymer nanowire provided by the present disclosure has excellent structural stability and does not disintegrate in an organic solvent. At the same time, it has excellent colloidal stability and can still stably exist in the presence of a large amount of surfactant. The cross-linked ionic polymer nanowire provided by the present disclosure has excellent wastewater flocculation effect, and a thin film prepared by using the cross-linked ionic polymer nanowire provided by the present disclosure has excellent pollutant nanofiltration effect.

Description

Technical Field

[0001] The present disclosure belongs to the field of water treatment, and particularly relates to an ionic polymer nanowire with a crosslinked structure, a preparation method thereof, and an application thereof. Background Art

[0002] Different from traditional solution self-assembly, the synthesis and self-assembly of block copolymers occur simultaneously in polymerization-induced self-assembly (PISA), which effectively simplifies the preparation process of nanomaterials. Moreover, PISA can prepare polymer nanomaterials at high concentrations, making PISA a very simple and efficient method for preparing polymer nanomaterials and laying a foundation for the commercial application of polymer nanomaterials. Polymer nanowires are one-dimensional linear nanomaterials that exhibit many special properties due to their anisotropic morphological structure and have great application prospects in rheological modification, high-efficiency Pickering emulsifiers, wastewater treatment, etc. Although polymerization-induced self-assembly (PISA) can easily prepare polymer nanowires at high concentrations, the morphological phase regions of polymer nanowires are often very narrow, resulting in poor repeatability in the preparation of polymer nanowires and being unfavorable for their large-scale production and application. Moreover, since the hydrophobic core of polymer nanowires is a non-crosslinked structure, their morphological structure stability is poor. Especially in some complex application environments, such as organic solvents and surfactants in wastewater, it is difficult to maintain their original morphological structure, affecting their application effects.

[0003] In wastewater purification, flocculation is a common means, which is convenient and feasible. Flocculation is generally achieved through electrostatic interaction, bridging, adsorption, etc. Existing commercial water-soluble polymer flocculants have poor flocculation effects on relatively large (such as 1 μm) suspended solids in aqueous solutions due to their small size, and will adsorb on the surface of these particles to make them more stable and not precipitate. The length of polymer nanowires can reach several micrometers to dozens of micrometers, and the diameter is generally dozens of nanometers, and it is expected to be used as a super flocculant to make up for the deficiencies of existing commercial flocculants. Water polluted by dyes can cause serious environmental and health problems. Microfiltration, nanofiltration, ultrafiltration, and reverse osmosis are relatively common membrane treatment technologies. Among them, nanofiltration is a relatively practical method for solving industrial dye wastewater problems, and it can effectively remove organic compounds with low molecular weights (200 - 1000 g / mol); at the same time, nanofiltration membranes also have many applications in the pharmaceutical field, food field, and chemical field. How to form a nano-scale pore structure is the key to preparing a nanofiltration membrane. The membrane material directly cast using polymer nanowires (with a length of several micrometers to dozens of micrometers and a diameter generally of dozens of nanometers) naturally has nano-scale pores and thus is expected to become a reliable material for preparing nanofiltration membranes.

[0004] In summary, the efficient preparation of polymer nanowires with a stable cross-linked structure is a major challenge at present. Cross-linked polymer nanowires are expected to become a reliable material for wastewater treatment, such as flocculation and nanofiltration. Summary of the Invention

[0005] In view of the above technical problems, the present disclosure provides an ionic polymer nanowire with a cross-linked structure, a preparation method thereof, and an application thereof, in order to at least partially solve the above technical problems.

[0006] As one aspect of the present disclosure, a preparation method of an ionic polymer nanowire with a cross-linked structure is provided, including:

[0007] In a solvent, a pro-solvent polymer segment P, a monomer for forming a non-solvent segment, an initiator, and a cross-linking agent are added, and in-situ cross-linking polymerization-induced self-assembly is carried out to prepare an ionic polymer nanowire with a cross-linked structure.

[0008] In one embodiment, the solvent includes: water or alcohol.

[0009] In one embodiment, the number of types of the pro-solvent polymer segment P is 1-20, and at least includes a pro-solvent polymer segment P1 with a charged surface, and optionally further includes a pro-solvent polymer segment P2 with an uncharged surface;

[0010] The charge in the pro-solvent polymer segment P1 with a charged surface is a positive charge or a negative charge;

[0011] The proportion of the charged pro-solvent polymer segment P1 in the pro-solvent polymer segment P is 0-1;

[0012] The negatively charged group is selected from one or more of carboxylate, phosphate, and sulfonate;

[0013] The positively charged group is selected from one or more of primary, secondary, and quaternary amine groups.

[0014] In one embodiment, the pro-solvent polymer segment P is obtained by polymerizing a pro-solvent segment monomer, and the pro-solvent segment monomer needs to carry a positive charge or a negative charge, wherein the charge is imparted to the pro-solvent segment by protonation or deprotonation.

[0015] In one embodiment, the pro-solvent segment monomer contains one or more of carboxylic acid (salt), phosphoric acid (salt), sulfonic acid (salt), primary amine, secondary amine, and quaternary amine;

[0016] The pro-solvent segment monomer includes at least one of (meth)acrylic acid monomers, (meth)acrylic acid sulfonate monomers, and (meth)acrylamide monomers.

[0017] The lyophobic segment monomers are selected from monomers containing polymerizable functional groups such as double bonds, including: (meth)acrylamide monomers, (meth)acrylate monomers.

[0018] In one embodiment, the crosslinking agent containing polymerizable functional groups with double bonds includes any one of N,N - methylenebisacrylamide, 2 - hydroxypropane - 1,3 - dipropionamide, and N,N - hexamethylenebisacrylamide;

[0019] The initiator includes: azobis(2 - amidinopropane) hydrochloride.

[0020] In one embodiment, the parameters for in - situ cross - linked polymerization - induced self - assembly include:

[0021] The polymerization temperature is - 80 to 200 °C;

[0022] The polymerization time is 1 min - 72 h.

[0023] As another aspect of the present disclosure, there is provided an ionic polymer nanowire with a cross - linked structure, which is obtained by the preparation method of the ionic polymer nanowire with a cross - linked structure in the above - mentioned embodiment. Among them, the surface of the ionic polymer nanowire with a cross - linked structure is charged.

[0024] As another aspect of the present disclosure, there is also provided an application of the ionic polymer nanowire with a cross - linked structure in water treatment, where the application includes one or more of wastewater flocculation and pollutant nanofiltration.

[0025] In one embodiment, the wastewater flocculation application includes:

[0026] According to the positive or negative nature of the charge carried on the surface of the ionic polymer nanowire with a cross - linked structure, bridging ions are added to the wastewater to bridge the ionic polymer nanowire with a cross - linked structure and the pollutants in the wastewater.

[0027] In one embodiment, the pollutant nanofiltration application includes:

[0028] The ionic polymer nanowire with a cross - linked structure is dispersed on a support membrane to form a nanofiltration composite membrane, and the pollutants are subjected to nanofiltration treatment.

[0029] In one embodiment, the method for forming the nanofiltration composite membrane includes at least one of the following:

[0030] Screen printing method, inkjet printing method, spin - coating method, casting molding method, pressure - driven deposition method, and spray pyrolysis method.

[0031] In one embodiment, the method for forming the nanofiltration composite membrane is the pressure - driven deposition method.

[0032] Based on the above technical solutions, an ionic polymer nanowire with a crosslinked structure, its preparation method and application provided by the present disclosure include one of the following beneficial effects:

[0033] (1) In the embodiments of the present disclosure, a pro-solvent polymer segment P, a monomer for forming a non-solvent segment, a crosslinking agent, and an initiator are added to a solvent. Through the method of in-situ crosslinked polymerization-induced self-assembly, the copolymerization, crosslinking, and self-assembly steps are carried out simultaneously, and an ionic polymer nanowire with a crosslinked structure is prepared in one step under relatively mild conditions. Through the method of in-situ crosslinked polymerization-induced self-assembly, the phase region of the polymer nanowire is expanded, the repeatability of preparing an ionic polymer nanowire with a crosslinked structure is improved, which is beneficial to the large-scale production of the ionic polymer nanowire with a crosslinked structure, and solves the problems of narrow phase region, poor repeatability, and unfavorable large-scale preparation and application of the nanowire prepared by the traditional polymerization-induced self-assembly technology through polymerization first and then crosslinking.

[0034] (2) The structure of the ionic polymer nanowire with a crosslinked structure prepared by the method provided by the present disclosure is relatively stable and can resist the dissolution of organic solvents; at the same time, the surface of the prepared polymer nanowire is charged, so that the nanowire is not easy to aggregate during storage and has a long storage period.

[0035] (3) The surface of the ionic polymer nanowire with a crosslinked structure prepared by the method provided by the present disclosure is charged. Through electrostatic interaction and the bridging effect with solid particles, the flocculation of solid particles in wastewater can be realized, the flocculation effect is improved, and the problem that the existing water-soluble polymer flocculant has a poor removal effect on larger solid particles in water is solved.

[0036] (4) The ionic polymer nanowire with a crosslinked structure provided by the present disclosure can also be used as a nanofiltration membrane to perform nanofiltration on dyes with different molecular weights, can realize the selective separation of dye-containing wastewater, and also has the characteristics of high flux and long life. Description of the Drawings

[0037] Figure 1 It is a comparative schematic diagram of the phase regions of nanowires prepared by traditional polymerization-induced self-assembly and in-situ crosslinked polymerization-induced self-assembly;

[0038] Figure 2 It is a transmission electron microscope image of the nanomaterial obtained when the crosslinking agent BIS = 0 in Comparative Example 1 of the present disclosure at different degrees of polymerization of the non-solvent segment;

[0039] Figure 3 It is a transmission electron microscope image of the nanomaterial obtained when the crosslinking agent BIS = 0 in Comparative Example 2 of the present disclosure at different degrees of polymerization of the non-solvent segment;

[0040] Figure 4It is the transmission electron microscopy image of the nanomaterials obtained from the lyophobic segments with different degrees of polymerization when the crosslinking agent BIS = 2 in Example 1 of the present disclosure;

[0041] Figure 5 It is the transmission electron microscopy image of the nanomaterials obtained from the lyophobic segments with different degrees of polymerization when the crosslinking agent BIS = 3 in Example 1 of the present disclosure;

[0042] Figure 6 It is the transmission electron microscopy image of the nanomaterials obtained from the lyophobic segments with different degrees of polymerization when the crosslinking agent BIS = 2 in Example 2 of the present disclosure;

[0043] Figures 7A - 7C It is the morphology phase diagram of the prepared nanomaterials when BIS = 0, 2, 3 in Examples 1 and 2 and Comparative Examples 1 and 2 of the present disclosure (where S represents spherical micelles, W represents polymer nanowires, V represents vesicles, and gel represents chemically crosslinked gels);

[0044] Figure 8 It is the transmission electron microscopy image of the repeatability experiment for preparing crosslinked polymer nanowires by the in-situ crosslinking polymerization-induced self-assembly method in Example 3 of the present disclosure;

[0045] Figure 9 It is the transmission electron microscopy image of the repeatability experiment for preparing uncrosslinked polymer nanowires by the traditional polymerization-induced self-assembly technique in Comparative Example 3 of the present disclosure;

[0046] Figure 10 It is the schematic diagram of the flocculation experiment of crosslinked polymer nanowires applied to kaolin-containing wastewater in Example 4 of the present disclosure;

[0047] Figure 11 It is the flocculation effect of crosslinked polymer nanowires and uncrosslinked polymer nanowires in Comparative Example 4-1 on kaolin-containing wastewater in Example 4 of the present disclosure;

[0048] Figure 12 It is the flocculation effect of commercial flocculants polyacrylamide, polyvinylpyrrolidone, and polydiallyldimethylammonium chloride on kaolin-containing wastewater in Comparative Example 4-2 of the present disclosure;

[0049] Figure 13 It is the schematic diagram of the application of crosslinked polymer nanowires to nanofiltration of organic dye wastewater in Examples 5 and 6 of the present disclosure;

[0050] Figure 14 It is the removal effect diagram of methylene blue dye in aqueous solution by nanofiltration composite membranes with different contents of crosslinked polymer nanowires in Example 5 of the present disclosure;

[0051] Figure 15It is a diagram showing the flux of a nanofiltration composite membrane with cross-linked polymer nanowires of different contents in Example 5 of the present disclosure for nanofiltration of methylene blue dye wastewater;

[0052] Figure 16 It is an effect diagram showing the removal of methylene blue dye by a nanofiltration composite membrane of uncross-linked polymer nanowires and a nanofiltration composite membrane of cross-linked polymer nanowires after being treated with dimethylformamide in Comparative Example 5 and Example 6 of the present disclosure;

[0053] Figure 17 It is a comparative transmission electron microscope image of uncross-linked nanowires (W-BIS0) and cross-linked nanowires (W-BIS2) in Example 7 of the present disclosure before and after being treated with N,N-dimethylformamide (DMF) and sodium dodecyl sulfate (SDS). Detailed implementation manners

[0054] To make the objectives, technical solutions, and advantages of the present disclosure clearer and more understandable, the present disclosure will be further described in detail below with reference to specific embodiments and the accompanying drawings.

[0055] Block copolymer nanomaterials prepared by traditional PISA are likely to disintegrate in the presence of surfactants or good solvents, and the pH value or temperature of the solvent will also affect the stability of the block copolymer nanomaterials. This structural instability will have an adverse impact on the performance of the nanomaterials, greatly limiting their practical application scope.

[0056] Based on this, the present disclosure provides a preparation method of ionic polymer nanowires with a cross-linked structure. By using in-situ cross-linking polymerization-induced self-assembly technology to expand the nanowire phase region, ionic polymer nanowires with a cross-linked structure (abbreviated as cross-linked polymer nanowires) with high repeatability, stable structure, long storage period, and surface charges can be prepared. The cross-linked polymer nanowires can be used in fields such as wastewater flocculation and nanofiltration for dye removal.

[0057] According to an embodiment of the present disclosure, a preparation method of ionic polymer nanowires with a cross-linked structure includes: adding a pro-solvent polymer segment P, a monomer for forming a poor-solvent segment, an initiator, and a cross-linking agent in a solvent, and performing in-situ cross-linking polymerization-induced self-assembly to prepare ionic polymer nanowires with a cross-linked structure.

[0058] Specifically, two kinds of pro-solvent polymer segments (one of which is a charged segment), monomers forming a lyophobic segment, an initiator, and a crosslinking agent are added to water (solvent), and the mixture is pretreated to remove oxygen to obtain a mixed solution; the mixed solution is polymerized under vacuum conditions (or in a nitrogen atmosphere) and at a predetermined temperature. After in-situ crosslinked polymerization-induced self-assembly, an ionic polymer nanowire with a crosslinked structure (i.e., a polymer nanowire with a crosslinked structure) is obtained. Among them, the pro-solvent polymer segment contains at least a part of an ionic polymer.

[0059] In an embodiment of the present disclosure, a pro-solvent polymer segment P, monomers forming a lyophobic segment, an initiator, and a crosslinking agent are added to a solvent. By means of in-situ crosslinking, the steps of copolymerization, crosslinking, and self-assembly are carried out simultaneously, and an ionic polymer nanowire with a crosslinked structure is prepared in one step under relatively mild conditions. By means of in-situ crosslinked polymerization-induced self-assembly, the phase region of the ionic polymer nanowire with a crosslinked structure is enlarged, the repeatability of preparing the ionic polymer nanowire with a crosslinked structure is improved, which is beneficial to the large-scale production of nanowires, and solves the complex process of post-polymerization crosslinking method by first polymerizing and then crosslinking, as well as problems such as the narrow phase region of the nanowires prepared by polymerization-induced self-assembly, poor colloidal stability, and difficulty in large-scale preparation and application.

[0060] According to an embodiment of the present disclosure, the solvent includes: water or alcohol.

[0061] In an embodiment of the present disclosure, water is preferably used as the solvent because water as a solvent has the characteristics of environmental friendliness and low cost. In addition, water is used as the solvent both in the preparation of the ionic polymer nanowire with a crosslinked structure and in its application process. The surface of the nanowire is charged in water, and the charges on the surface of the nanowire repel each other and are not easily aggregated and precipitated, so that the prepared crosslinked polymer nanowire can take into account both structural stability and colloidal stability.

[0062] According to an embodiment of the present disclosure, the number of types of the pro-solvent polymer segment P is 1-20, and at least includes a pro-solvent polymer segment P1 with a charged surface, and optionally further includes a pro-solvent polymer segment P2 with an uncharged surface. Among them, the pro-solvent polymer segment P is obtained by polymerizing pro-solvent segment monomers, and the pro-solvent segment monomer units need to carry a positive charge or a negative charge, and the charge can be imparted to the pro-solvent segment by protonation or deprotonation, for example, it can be adjusted by adding an external salt or by means of pH, etc. In the embodiment of the present disclosure, the charged pro-solvent segment monomers contain one or more of carboxylic acid (salt), phosphoric acid (salt), sulfonic acid (salt), primary amine, secondary amine, and quaternary amine. In the embodiment of the present disclosure, the pro-solvent polymer segment P is preferably acrylic acid monomer.

[0063] According to an embodiment of the present disclosure, the proportion of the charged pro-solvent polymer segment P1 in the pro-solvent polymer segment P is 0-1, and can be optionally 0.2, 0.3, 0.5, 0.7, 1.0, etc.

[0064] In an embodiment of the present disclosure, the charge carried by the pro-solvent polymer segment P1 determines the charge carried on the surface of the corresponding cross-linked polymer nanowires, and different water treatment scenarios can be applied according to the electrostatic interaction between the cross-linked polymer nanowires and the pollutant particles.

[0065] According to an embodiment of the present disclosure, the molar ratio of the cross-linking agent to the pro-solvent polymer segment P is (1-20):1, and can be optionally: 1:1, 2:1, 3:1, 4:1, 6:1, 8:1, 10:1, 12:1, 15:1, 20:1, etc., among which, (1-3):1 is more preferred.

[0066] In an embodiment of the present disclosure, if the content of the cross-linking agent is too large (exceeding 20:1), it will cause the formation of a reticular cross-linked structure earlier, and at the same time, it may cause the cross-linking between the formed particles, restricting the transformation of the particle morphology, and a complete nanowire morphology cannot be obtained, and the obtained may be a nanomaterial with an irregular morphology.

[0067] In an embodiment of the present disclosure, the main principle of the expansion of the cross-linked polymer nanowire phase region is: in the early stage of the reaction, the polymer will form a branched structure, thereby promoting the transformation from spherical micelles to nanowires. In the later stage of polymerization, after the cross-linking agent has basically completed the reaction, the polymer segments will form a cross-linked network structure, inhibiting the transformation of nanowires into vesicles, and thus expanding the phase region of the cross-linked polymer nanowires.

[0068] According to an embodiment of the present disclosure, the cross-linking agent contains polymerizable functional groups such as double bonds.

[0069] According to an embodiment of the present disclosure, the cross-linking agent used includes any one of N,N-methylenebisacrylamide, 2-hydroxypropane-1,3-dipropionamide, and N,N-hexamethylenebisacrylamide.

[0070] According to an embodiment of the present disclosure, the in-situ cross-linking polymerization-induced self-assembly polymerization method of the pro-solvent polymer segment P and the monomer forming the lyophobic segment includes: reversible addition-fragmentation chain transfer polymerization, stable free radical polymerization, atom transfer radical polymerization, anionic polymerization, cationic polymerization, ring-opening polymerization, coordination polymerization, or ring-opening metathesis polymerization, etc. The temperature for in-situ cross-linking polymerization-induced self-assembly is -80°C - 200°C, and the polymerization time is 1 min - 72 h.

[0071] According to an embodiment of the present disclosure, the monomer forming the lyophobic segment includes diacetone acrylamide.

[0072] According to an embodiment of the present disclosure, by using the method for preparing cross-linked polymer nanowires in the above embodiment, an ionic polymer nanowire with a cross-linked structure (hereinafter referred to as cross-linked polymer nanowire) can be obtained. The surface of the cross-linked polymer nanowire is charged. Considering the significant differences in factors such as the length of the solventophilic chain segment and the solventophobicity of the nucleating block monomer, the degree of polymerization of the solventophobic chain segment in the cross-linked polymer nanowire can be 5 - 5000, and can be selected from 5, 10, 40, 50, 60, 70, 80, 90, 100, 500, 1000, 2500, 5000, etc. Among them, the degree of polymerization of the solventophobic chain segment in the cross-linked polymer nanowire is preferably 30 - 300.

[0073] In the embodiment of the present disclosure, the degree of polymerization of the solventophobic chain segment represents the number of monomer units contained in the solventophobic chain segment in the cross-linked polymer nanowire.

[0074] According to an embodiment of the present disclosure, there is also provided an application of the cross-linked polymer nanowire in water treatment, wherein the application includes one or more of wastewater flocculation and pollutant nanofiltration.

[0075] Among them, the sources of wastewater in wastewater flocculation include: kaolin wastewater, oily wastewater, organic dye wastewater, pesticide wastewater, building material wastewater, urban domestic wastewater, hospital wastewater, petrochemical wastewater, pharmaceutical wastewater, paper-making wastewater, etc.; pollutant nanofiltration includes: organic dye pollutant nanofiltration, heavy metal removal nanofiltration, etc.

[0076] According to an embodiment of the present disclosure, the method for applying the cross-linked polymer nanowire to kaolin wastewater flocculation includes: adding kaolin to water and stirring to simulate wastewater containing solid particles (kaolin), and then dispersing the cross-linked polymer nanowire and bridging cations into the wastewater containing solid particles (kaolin) and stirring, so that the cross-linked polymer nanowire can be used to flocculate the solid particles (kaolin particles) in the wastewater and precipitate them at the bottom of the water.

[0077] According to an embodiment of the present disclosure, the concentration of kaolin wastewater is 0.01 - 100 g / mL.

[0078] According to an embodiment of the present disclosure, the introduced bridging ions include divalent or polyvalent bridging cations. The bridging ions are used to bridge the cross-linked polymer nanowire and the solid particle pollutants (such as kaolin) in the wastewater, and then under the electrostatic action, the solid particle pollutants in the wastewater are flocculated and precipitated; among them, the bridging cations can be selected from one or more of aluminum, magnesium, calcium, barium, and strontium ions, and calcium ion is preferably used as the bridging cation.

[0079] In the embodiment of the present disclosure, the concentration range of the bridging cations is 0.1 μg / mL to 1 g / mL, and preferably 50 mg / mL.

[0080] According to an embodiment of the present disclosure, the stirring rate during the flocculation process is 10 - 8000 rpm, preferably 500 rpm; the flocculation stirring time is 1 min - 48 h. Among them, the stirring time before flocculation is 2 h, that is, the wastewater containing kaolin is stirred for 2 h without adding cross-linked polymer nanowires to uniformly disperse the kaolin solid particles in the water; the stirring time during the flocculation process is 0.5 h to enable the cross-linked polymer nanowires to fully contact, mix with the kaolin particles in the wastewater, and flocculate and precipitate.

[0081] According to an embodiment of the present disclosure, the method of using cross-linked polymer nanowires for pollutant nanofiltration includes: dispersing the cross-linked polymer nanowires on a support membrane to form a composite membrane with the support membrane, and then performing nanofiltration treatment on organic pollutants under pressure driving.

[0082] According to an embodiment of the present disclosure, the method of forming a nanofiltration composite membrane on a support membrane is not limited to the pressure driving method, and may also include screen printing, inkjet printing, spin coating, casting molding, spray pyrolysis, etc.

[0083] In the embodiment of the present disclosure, the pressure driving method is selected to prepare a nanofiltration composite membrane from nanowires on a support membrane. Among them, the pressure range selected for the nanofiltration membrane and the nanofiltration experiment is 0.01 - 2 MPa, preferably 0.098 MPa.

[0084] According to an embodiment of the present disclosure, the support membrane can be selected from any one of mixed cellulose membranes, cellulose acetate membranes, polyethersulfone membranes, polytetrafluoroethylene membranes, polyvinylidene fluoride membranes, nylon membranes, polypropylene membranes, or glass fiber membranes. In the embodiment of the present disclosure, the support membrane is preferably a mixed cellulose membrane or a polytetrafluoroethylene membrane. It should be noted that the selected membrane in the present disclosure has almost no nanofiltration effect on organic pollutants.

[0085] According to an embodiment of the present disclosure, the dye concentration range for the nanofiltration experiment is 10 -6 ~10 -3 mol / L, preferably the dye concentration range is 5×10 -5 mol / L or 1×10 -5 mol / L; the dye in the embodiment of the present disclosure can be at least one of positively charged or negatively charged dyes, such as: the positively charged methylene blue dye is selected.

[0086] The technical solution of the present disclosure will be further elaborated and illustrated below through specific embodiments in combination with the drawings. It should be noted that the following specific embodiments are only for illustration, and the protection scope of the present disclosure is not limited thereto. The chemical drugs and raw materials used in the following embodiments are all obtained commercially or prepared by recognized preparation methods.

[0087] Comparative Example 1

[0088] When the solid content is 20%, the typical protocol for the synthesis of non-crosslinked polymer nanowires by traditional polymerization-induced self-assembly is as follows: The hydrophilic segment poly(N,N-dimethylacrylamide) (PDMA 31 , 25.6 mg, 8.0 μmol), the charged hydrophilic segment poly(acrylic acid) (PAA 32 , 5.4 mg, 2.0 μmol), the initiator 2,2'-azobis(2-methylpropionamidine) dihydrochloride (V-50, 0.27 mg, 1.0 μmol), the monomer for forming the solventophobic segment diacetone acrylamide (DAAm, 169 mg, 1.0 mmol) and water (0.80 g) are added to a test tube. After three freeze-pump-thaw cycles, the test tube is sealed under vacuum. Then, polymerization is carried out in an oil bath at 70 °C for 5 h. Finally, the polymerization is quenched by rapidly cooling to room temperature and exposing to air. The synthesis route of Comparative Example 1 is as Figure 1 shown. By changing the target degree of polymerization (DP = 30 - 100) of the PDAAm block, a series of non-crosslinked polymer nanomaterials were synthesized. The transmission electron microscopy (TEM) images of the corresponding polymer nanomaterials at different degrees of polymerization are as Figure 2 shown; and the morphology phase diagram shown in Figure 7A is drawn accordingly.

[0089] Comparative Example 2

[0090] When the solid content is 25%, the typical protocol for the synthesis of non-crosslinked polymer nanowires by traditional polymerization-induced self-assembly is as follows: PDMA 31 (25.6 mg, 8.0 μmol), PAA 32 (5.4 mg, 2.0 μmol), V-50 (0.27 mg, 1.0 μmol), the monomer for forming the solventophobic segment diacetone acrylamide (DAAm, 169 mg, 1.0 mmol) and water (0.60 g) are added to a test tube. After three freeze-pump-thaw cycles, the test tube is sealed under vacuum. Then, polymerization is carried out in an oil bath at 70 °C for 5 h. Finally, the polymerization is quenched by rapidly cooling to room temperature and exposing to air. A series of non-crosslinked polymer nanomaterials were synthesized by changing the degree of polymerization (DP = 30 - 100) of the PDAAm segment. The TEM images of the corresponding polymer nanomaterials at different degrees of polymerization are as Figure 3 shown; and the morphology phase diagram shown in Figure 7A is drawn accordingly.

[0091] Example 1

[0092] When the solid content is 20%, the typical protocol for the synthesis of crosslinked polymer nanowires by in-situ crosslinked polymerization-induced self-assembly is as follows: PDMA 31 (25.6 mg, 8.0 μmol), PAA 32(5.4 mg, 2.0 μmol), N,N-methylenebisacrylamide (BIS) (3.16 mg, 20 μmol), initiator 2,2'-azobis(2-methylpropionamidine) dihydrochloride V-50 (0.27 mg, 1.0 μmol), monomer diacetone acrylamide (DAAm, 169 mg, 1.0 mmol) for forming the lyophobic segment, and water (0.81 g) were added to a test tube. After three freeze-pump-thaw cycles, the test tube was sealed under vacuum. Then, polymerization was carried out in an oil bath at 70 °C with stirring for 5 h. Finally, the polymerization was quenched by rapid cooling to room temperature and exposure to air. The specific synthesis route is as Figure 1 shown. In the case of BIS / P = 2 or 3 (BIS / P = 2 or 3 represents the molar ratio of the crosslinking agent to the lyophilic polymer segment P of 2:1 or 3:1), it is in-situ crosslinking polymerization-induced self-assembly. A series of crosslinked polymer nanomaterials were synthesized by changing the degree of polymerization (DP = 30 - 100) of the PDAAm segment. The TEM images of the corresponding polymer nanomaterials at different degrees of polymerization are as Figures 4 - 5 shown; and the morphology phase diagrams shown in Figure 7B and 7C were plotted accordingly.

[0093] Example 2

[0094] When the solid content was 25%, a typical protocol for in-situ crosslinking polymerization-induced self-assembly to synthesize crosslinked polymer nanowires was as follows: PDMA 31 (25.6 mg, 8.0 μmol), PAA 32 (5.4 mg, 2.0 μmol), N,N-methylenebisacrylamide (BIS) (3.16 mg, 20 μmol), initiator 2,2'-azobis(2-methylpropionamidine) dihydrochloride V-50 (0.27 mg, 1.0 μmol), diacetone acrylamide (DAAm, 169 mg, 1.0 mmol), and water (0.61 g) were added to a test tube. After three freeze-pump-thaw cycles, the test tube was sealed under vacuum. Then, polymerization was carried out in an oil bath at 70 °C with stirring for 5 h. Finally, the polymerization was quenched by rapid cooling to room temperature and exposure to air. In the case of BIS / P = 2 or 3 (BIS / P = 2 or 3 represents the molar ratio of the crosslinking agent to the lyophilic polymer segment P of 2:1 or 3:1), it is in-situ crosslinking polymerization-induced self-assembly. A series of crosslinked polymer nanomaterials were synthesized by changing the degree of polymerization (DP = 30 - 100) of the PDAAm segment. The TEM images of the corresponding polymer nanomaterials at different degrees of polymerization are as Figure 6 shown; and the morphology phase diagrams shown in Figure 7B and 7C were plotted accordingly.

[0095] Figures 7A - 7CIt is the morphology phase diagram of the nanomaterials prepared at BIS / P = 0, 2, and 3 in Examples 1 and 2 and Comparative Examples 1 and 2 of the present disclosure. When no cross-linking agent is used (conventional polymerization-induced self-assembly, BIS / P = 0), Figure 7A it shows that the range of the morphology phase region of the obtained non-crosslinked polymer nanowires is relatively narrow (corresponding to Figures 2 - 3 ); while when BIS = 2, Figure 7B it shows that the range of the morphology phase region of the crosslinked polymer nanowires prepared by in-situ crosslinked polymerization-induced self-assembly is relatively wide (corresponding to Figure 4 , 6 ), indicating that in-situ crosslinked polymer-induced self-assembly can significantly expand the morphology phase region of polymer nanowires.

[0096] In the examples of the present disclosure, relevant experiments were also carried out on the repeatability of preparing crosslinked polymer nanowires by in-situ crosslinked polymerization-induced self-assembly provided by the present disclosure and non-crosslinked nanowires by the traditional PISA method. The specific experimental procedures are as in Example 3 and Comparative Example 3.

[0097] Example 3

[0098] In-situ crosslinked polymer-induced self-assembly was used to synthesize 10 batches of crosslinked polymer nanowires. The typical experimental protocol is as follows: Select the experimental conditions at the midpoint of the region of polymer nanowires in the morphology phase Figure 7B for the repeatability experiment. The solid content is 22.5%, PDMA 31 (25.6 mg, 8.0 μmol), PAA 32 (5.4 mg, 2.0 μmol), N,N-methylenebisacrylamide (BIS) (3.16 mg, 20 μmol), V-50 (0.27 mg, 1.0 μmol), diacetone acrylamide (DAAm, 109.9 mg, 0.65 mmol) and water (0.497 g) were added to a test tube. After three freeze-pump-thaw cycles, the test tube was sealed under vacuum. Then, polymerization was carried out in an oil bath at 70 °C for 5 h. Finally, the polymerization was quenched by rapidly cooling to room temperature and exposing to air. The above experiment was repeated 10 times under the same feeding and conditions. The morphology of the obtained nanomaterials is as Figure 8 shown, and the repetition rate of preparing crosslinked polymer nanowires by in-situ crosslinked polymerization-induced self-assembly technology is about 70%.

[0099] Comparative Example 3

[0100] Traditional polymer-induced self-assembly was used to synthesize 10 batches of non-crosslinked polymer nanowires. The typical experimental protocol is as follows: Select the experimental conditions at the midpoint of the region of polymer nanowires in the morphology phase Figure 7A for the repeatability experiment. The solid content is 22.5%, PDMA 31(25.6 mg, 8.0 μmol), PAA 32 (5.4 mg, 2.0 μmol), V - 50 (0.27 mg, 1.0 μmol), diacetone acrylamide (DAAm, 110 mg, 0.65 mmol) and water (0.49 g) were added into a test tube. After three freeze - vacuum - thaw cycles, the test tube was sealed under vacuum and then polymerized in an oil bath at 70 °C for 5 h. Finally, the polymerization was quenched by rapid cooling to room temperature and exposure to air. The above experiment was repeated 10 times under the same feeding and conditions, and the morphology of the obtained nanomaterials is as Figure 9 shown. The repetition rate of preparing polymer nanowires by the traditional polymerization - induced self - assembly technique is only about 10%.

[0101] It can be seen from Example 3 and Comparative Example 3 that the in - situ cross - linked polymerization - induced self - assembly technique provided by the present disclosure for preparing cross - linked polymer nanowires has high repeatability, which is beneficial to the large - scale preparation and application of cross - linked polymer nanowires.

[0102] The prepared cross - linked polymer nanowires were applied to the field of water treatment, and the specific application fields and operation processes involved are shown in Examples 4 - 7.

[0103] Example 4

[0104] Kaolin (150 mg, 20 mg / mL) was added to water (7.5 mL) to simulate wastewater containing solid particles, and then anhydrous CaCl2 (0.75 mg, 0.1 mg / mL) was added, and the dispersion was stirred at 700 rpm for 1 h. The cross - linked polymer nanowires prepared by in - situ cross - linked polymerization - induced self - assembly (0.5% w / w) were added to the above wastewater containing kaolin and stirred for 30 minutes ( Figure 10 ). After stopping stirring for 2 h, the transmittance of the water treated with cross - linked polymer nanowires was tested, and the specific flocculation effect is as Figure 11 shown. Using cross - linked polymer nanowires as a flocculant, the best flocculation effect reached 95.9%.

[0105] Comparative Example 4 - 1

[0106] Kaolin (150 mg, 20 mg / mL) was added to water (7.5 mL) to simulate wastewater containing solid particles, and then anhydrous CaCl2 (0.75 mg, 0.1 mg / mL) was added, and the dispersion was stirred at 700 rpm for 1 h. The non - cross - linked polymer nanowires prepared by the traditional polymerization - induced self - assembly method (0.5% w / w) were added to the above wastewater containing kaolin and stirred for 30 minutes. After stopping stirring for 2 h, the transmittance of the water treated with non - cross - linked polymer nanowires was tested, and the specific flocculation effect is as Figure 11As shown, an uncrosslinked polymer nanowire was selected as the flocculant, and its best flocculation effect was only 28.7%. This is mainly because the morphology and structure of the uncrosslinked polymer nanowire are unstable, resulting in poor flocculation effect.

[0107] Comparative Example 4-2

[0108] Kaolin (150 mg, 20 mg / mL) was added to water (7.5 mL) to simulate wastewater containing solid particles, and then anhydrous CaCl2 (0.75 mg, 0.1 mg / mL) was added as a bridging cation, and the dispersion was stirred at 700 rpm for 1 h. Different commercial polymers (polyacrylamide, polyvinylpyrrolidone, and polydiallyldimethylammonium chloride) (0.5% w / w) were respectively added to the above wastewater containing kaolin and stirred for 30 minutes. After stopping stirring for 2 h, the transmittance of the water treated with different polymers was tested, and the specific flocculation effects are as Figure 12 shown. The best flocculation effects of each commercial flocculant are as follows: polyacrylamide PAM (76.0%), polyvinylpyrrolidone PVP (70.2%), polydiallyldimethylammonium chloride PDADMAC (64.5%). It can be seen that the flocculation effects of common flocculants on the market are not as good as those of the crosslinked polymer nanowires prepared in the present disclosure. This is mainly due to the mismatch between the small size of the commercial polymer flocculant and the large particle size in the wastewater.

[0109] Example 5

[0110] At 0.098 MPa, a certain amount of crosslinked polymer nanowires was dispersed on a commercial mixed cellulose (MCE) support membrane (pore size 0.22 μm) to prepare a composite membrane with the support membrane. The obtained nanofiltration composite membrane was used to conduct a nanofiltration experiment on an aqueous solution of methylene blue (MB) (10 -5 mol / L), and the pressure of the nanofiltration experiment was set at 0.098 MPa. The schematic diagram of the nanofiltration experiment is as Figure 13 . The removal effect of the nanofiltration membrane on the dye and the nanofiltration flux are respectively as Figure 14 and Figure 15 shown. It can be seen from Figures 14 - 15 that when the content of the crosslinked polymer nanowires in the composite membrane is 3.96 mg / cm 2 , the effect is the best: the flux reaches 17.5 L / (m 2 hbar), and after nanofiltration for 12 h, the removal efficiency of the composite membrane for methylene blue is still as high as 99.5%.

[0111] Example 6

[0112] At 0.098 MPa, a certain amount of cross-linked polymer nanowires was dispersed on a commercial polytetrafluoroethylene (PTFE) support membrane (pore size 0.22 μm), and the content of cross-linked nanowires in the composite membrane was 3.96 mg / cm 2 . The obtained nanofiltration composite membrane was first treated with 2 mL of dimethylformamide (DMF), and then a nanofiltration experiment was carried out on an aqueous solution of methylene blue (MB) (10 -5 mol / L). The pressure of the nanofiltration experiment was set at 0.098 MPa, and its removal effect on the dye is as Figure 16 shown. The nanofiltration composite membrane prepared from cross-linked polymer nanowires still had a removal efficiency of up to 97.8% for methylene blue even after 8 h of nanofiltration. This is mainly because the structure of the cross-linked polymer nanowires is very stable, and the treatment with DMF will not cause the destruction of its morphological structure ( Figure 17 ).

[0113] Comparative Example 5

[0114] At 0.098 MPa, a certain amount of non-cross-linked polymer nanowires was dispersed on a commercial polytetrafluoroethylene (PTFE) support membrane (pore size 0.22 μm), and the content of non-cross-linked nanowires in the composite membrane was 3.96 mg / cm 2 . The obtained nanofiltration composite membrane was first treated with 2 mL of dimethylformamide (DMF), and then a nanofiltration experiment was carried out on an aqueous solution of methylene blue (MB) (10 -5 mol / L). The pressure of the nanofiltration experiment was set at 0.098 MPa, and its removal effect on the dye is as Figure 16 shown. The non-cross-linked polymer nanowires could not resist the dissolution of DMF ( Figure 17 ), and the nanofiltration membrane disappeared, making it impossible to effectively remove the dye.

[0115] Example 7

[0116] Explore the colloidal stability and structural stability of the prepared non-cross-linked polymer nanowires and cross-linked polymer nanowires. After storing the two in an aqueous solution of sodium dodecyl sulfate (SDS) (1% w / v) for 24 h or in a DMF solution for 1 h respectively, the morphological changes of the nanowires were tested by TEM, and the results are as Figure 17 shown. It was found that in the SDS solution, both had good colloidal stability because the nanowires had charges on their surfaces and could resist the destruction of the nanowire morphology by SDS. However, the non-cross-linked nanowires had poor structural stability and could not resist the dissolution of the organic solvent DMF, and their morphology disintegrated. The cross-linked polymer nanowires still maintained the nanowire morphology structure after being treated with DMF. The above experimental results show that the ionic polymer nanowires with a cross-linked structure prepared by in-situ cross-linking polymerization-induced self-assembly have both good colloidal stability and structural stability.

[0117] The specific embodiments described above further elaborate on the objectives, technical solutions, and beneficial effects of the present disclosure. It should be understood that the above are only specific embodiments of the present disclosure and are not intended to limit the present disclosure. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present disclosure shall be included within the protection scope of the present disclosure.

Claims

1. Application of an ionic polymer nanowire with a crosslinked structure in water treatment, including: According to the positive or negative charge carried on the surface of the ionic polymer nanowire with a crosslinked structure, bridging ions are added to the wastewater to bridge the ionic polymer nanowire with the crosslinked structure and the pollutants in the wastewater, so as to achieve the flocculation and precipitation of solid particles in the wastewater; or Disperse the ionic polymer nanowire with the crosslinked structure on a support membrane and form a nanofiltration composite membrane therewith to perform nanofiltration treatment on the pollutants; Among them, the ionic polymer nanowire with the crosslinked structure is obtained by in-situ crosslinked polymerization-induced self-assembly of a pro-solvent polymer segment P, a monomer forming a lyophobic segment, an initiator, and a crosslinking agent in a solvent, and the surface of the ionic polymer nanowire with the crosslinked structure carries a charge; The solvent is water or alcohol; the crosslinking agent is selected from crosslinking agents containing polymerizable functional groups with double bonds; The pro-solvent polymer segment P at least includes a pro-solvent polymer segment P1 with a charged surface.

2. The application according to claim 1, wherein The crosslinking agent includes any one of N,N-methylenebisacrylamide and N,N-hexamethylenebisacrylamide; The initiator includes: azodiisobutyramidine hydrochloride.

3. The application according to claim 1, wherein, The number of types of the pro-solvent polymer segment P is 1-20, and the charge in the pro-solvent polymer segment P1 with a charged surface is positive or negative; The negatively charged group is selected from one or more of carboxylates, phosphates, and sulfonates; The positively charged group is selected from quaternary amino groups.

4. According to the application described in claim 3, the pro-solvent polymer segment P further includes a pro-solvent polymer segment P2 with an uncharged surface; The molar ratio of the charged pro-solvent polymer segment P1 to the pro-solvent polymer segment P is 0-1.

5. The application according to claim 3, wherein, The negatively charged pro-solvent polymer segment P1 is polyacrylic acid.

6. The application according to claim 1, wherein The in-situ crosslinked polymerization-induced self-assembly is carried out: The polymerization temperature is -80~200 °C; The polymerization time is 1 min - 72 h.

7. The application according to claim 1, wherein, The method for forming the nanofiltration composite membrane includes at least one of the following: Screen printing method, inkjet printing method, spin coating method, casting molding method, pressure-driven deposition method, spray pyrolysis method.

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