Ion-sensitive hydrogel, preparation method and application thereof, and detection device for ion solution

Abstract

The present application belongs to the field of ion solution detection, and in particular relates to an ion-sensitive hydrogel, a preparation method and application thereof, and a detection device for ion solutions. The ion-sensitive hydrogel is formed by polymerization of electrolyte monomers and non-electrolyte monomers; the ion-sensitive hydrogel is determined by small-angle X-ray scattering to have a microphase separation structure with a structural characteristic size of 10-40 nm. The microphase separation structure inside the ion-sensitive hydrogel has an electrostatic repulsion effect and is sensitive to changes in the ionic strength in the environment; when stimulated by ions in the solution, the hydrogel can produce polarization and volume shrinkage properties. Therefore, the concentration of the ion solution can be detected by detecting the polarization phenomenon of the ion-sensitive hydrogel.

Description

Technical Field

[0001] The present application belongs to the field of ion solution detection, and in particular relates to an ion-sensitive hydrogel, a preparation method and application thereof, and an ion solution detection device. Background Art

[0002] In current research, ion-responsive hydrogels are becoming increasingly intelligent and versatile. However, with the development of people's demand for instant detection, most research results still have some problems in use: first, the response rate is slow; second, the threshold of the ion concentration of the response is high. The time from the gel feeling the salt stimulation to the response phenomenon is the response rate. The response rate determines the timeliness of the output response phenomenon of the hydrogel device. If the process is too slow, the user will not be able to obtain effective information immediately. The response rate of the current salt-responsive hydrogel is mostly between tens of seconds and hundreds of seconds, which is difficult to meet the needs of practical applications. In order to improve this problem, Zheng Siyu et al. prepared a hydrogel with a thickness of about 100 microns. Due to the reduction in size, the time required for salt to diffuse inside the hydrogel is reduced, so the response rate of the hydrogel is improved, and a response can occur in 38 seconds (Soft Matter, 2018, 14 (28): 5888-5897.), but the hysteresis of this response rate is still large. On the other hand, the response concentration threshold of hydrogel determines their application scenarios. If the response threshold concentration exceeds the solution concentration of the natural environment or physiological environment, the gel loses the possibility of application in these fields. For example, NIPAm salt response gel has a high salt concentration required for response, and the response property is affected by temperature, so the actual application potential is not great. The response threshold of electrolyte hydrogel can be as low as 0.01M (ACS Applied Materials and Interfaces, 2017, 9 (24): 20843-20851.), but because it relies on volume shrinkage to reflect response behavior, the gel response phenomenon under low salt concentration is weak and difficult to observe. Summary of the Invention

[0003] Based on the above technical problems, the present application provides an ion-stimulation-responsive hydrogel, which is polymerized from electrolyte monomers and non-electrolyte monomers. The hydrophobic groups in the non-electrolyte monomers can form a 10-40nm microphase separation structure within the hydrogel. The microphase separation structure within the ion-sensitive hydrogel has an electrostatic repulsion effect and is sensitive to changes in ionic strength in the environment. When stimulated by ions in the solution, the hydrogel can produce polarization and volume shrinkage.

[0004] In a first aspect, the present application provides an ion-sensitive hydrogel, wherein the ion-sensitive hydrogel is polymerized by electrolyte monomers and non-electrolyte monomers;

[0005] According to small-angle X-ray scattering, the ion-sensitive hydrogel has a microphase separation structure with a structural characteristic size of 10-40 nm.

[0006] Specifically, the microphase separation structure is formed by the hydrophobic groups in the non-electrolyte monomer.

[0007] More specifically, as determined by small-angle X-ray scattering, the characteristic size distribution range of the ion-sensitive hydrogel is between 15-35 nm.

[0008] In another embodiment, the ion-sensitive hydrogel undergoes a specific volume change under the stimulation of an ion solution with a specific concentration, resulting in optical birefringence within a specific corresponding time.

[0009] Specifically, the ion-sensitive hydrogel has an optical birefringence phenomenon in response to ion stimulation in the environment; the ion-sensitive hydrogel has an optical response characteristic in response to deformation.

[0010] In another embodiment, the concentration of the ionic solution is 0.001M-5M; the specific response time is no more than 1.5s;

[0011] The concentration of the ion solution is 0.001M-5M; and the specific response time is no more than 1.5s.

[0012] In another embodiment, the ion-sensitive hydrogel generates optical birefringence under a specific volume change, wherein the volume change is one or more of tensile strain, compressive strain and shear strain, and the volume change range of the volume change is 1%-1000%.

[0013] Specifically, the ion-sensitive hydrogel provided in the present application can produce polarization when the ionic strength in the solution is 0.01 M. More specifically, the ion-sensitive hydrogel exhibits polarization in NaCl solutions with ionic strengths of 0.01-5 M, and the duration of the polarization phenomenon increases with increasing salt concentration.

[0014] Specifically, the ion-sensitive hydrogel provided herein exhibits isotropic volume contraction in an ionic solution. The polarization phenomenon produced by the ion-sensitive hydrogel in response to salt is not caused by asynchronous changes in the length, width, and thickness of the gel during contraction.

[0015] In another embodiment, the ionic solution includes one or more of an acid, a base, a salt, and an organic amine. The ionic solution is an electrolyte solution.

[0016] Specifically, the acid includes one or more of HCl, H2CO3, H2PO3, CH3COOH, aluminum chloride, boron trifluoride, sulfur trioxide, ferric bromide, ferric chloride, niobium pentachloride, zinc chloride, sulfuric acid, nitric acid, iodic acid, sulfurous acid, pyruvic acid, nitrous acid, perchloric acid, hydroiodic acid, hydrobromic acid, lactic acid, benzoic acid, propionic acid, and hydrofluoric acid; the base is LiOH, NaOH, KOH, NH3H2O, Mg(OH)2, Ca(OH)2, Ba(OH)2, Zn(OH) 2. One or more of Sn(OH)2, caustic soda or compound alkali; the salt is LiCl, NaCl, KCl, NH4Cl, LiBr, NaBr, KBr, NH4Br, NaNO3, KNO3, K2SO4, K2CO3, BaCl2, CuCl2, CaCl2, MgCl2, FeCl3, AlCl3, MgSO4, Na2SO4, Na2CO3, NaHCO3, Na3PO4, Na4P2O7 and Na5P3O 10 One or more of; the organic amine is ethylamine, ethylenediamine, triethylamine, triethylenediamine, tetramethylethylenediamine, N-methylmorpholine, DIPEA, morpholine, DMAP and pyridine in one or more.

[0017] The hydrophobic groups in the non-electrolyte monomers in the ion-sensitive hydrogel of the present application can form a microphase-separated structure inside the hydrogel, and the distance between the phases is the characteristic size described in the process. Characterized by means of small-angle X-ray scattering (SAXS), the characteristic size structure of the ion-sensitive hydrogel is nanometer-level, and the diffusion time of salt between the two phases is much less than the diffusion time in the direction of the hydrogel bulk material, so the ion-sensitive hydrogel of the present application has a fast salt response characteristic. When the preferred hydrogel contains charged groups, the ion-sensitive hydrogel has an electrostatic repulsion effect inside, is sensitive to changes in the ion concentration intensity in the environment, and will produce local volume contraction or expansion after sensing the stimulation of external ions, thereby inducing the gel material to produce polarization.

[0018] In another embodiment, the ratio of the total molar number of the electrolyte monomers to the total molar number of the non-electrolyte monomers is (0.5:9.5) to (5:5).

[0019] Preferably, the ratio of the total molar number of the electrolyte monomers to the total molar number of the non-electrolyte monomers is 1:9, more preferably 2:8 or 3:7. Within the ratio range provided in this application, the hydrogel exhibits significant polarization, while beyond this range, the gel loses this property.

[0020] In another embodiment, the chemical structure of the ion-sensitive hydrogel has the structure shown in formula (I) or formula (II);

[0021]

[0022] Wherein, when R1 is selected as a cation, R1 includes quaternary ammonium ion, quaternary phosphonium ion, sulfonium ion, imidazolium ion, pyridinium ion, piperidinium ion and pyrrolium ion; when R1 is selected as an anion, R1 includes carboxylate ion, sulfonate ion, sulfinic acid ion and phosphate ion;

[0023] R2 is a C1-C20 alkyl group, a phenyl group, or a C1-C20 alkoxy group;

[0024] R3 is a phenyl group, a C0-C20 alkyl group, or a C0-C20 alkoxy group;

[0025] The R4 is phenyl, C0-C20 alkyl, C0-C20 alkoxy, 1≤c≤20, 1≤d≤20;

[0026] The polymer structure represented by the formula (I) does not contain R5 and / or R6; or the R5 and R6 are independently selected from an amide group, an ester group, a methylene group or a phenyl group;

[0027] The R7 and R8 are each independently selected from hydrogen or methyl;

[0028] Wherein, the R9 and the R 10 Each independently selected from methyl, ethyl or phenyl;

[0029] The polymer having the structure represented by the formula (I) does not include the copolymer of 2-phenoxyethyl acrylate or 2-phenoxyethyl methacrylate and 2-acryloyloxyethyltrimethylammonium chloride or 2-methacryloyloxyethyltrimethylammonium chloride.

[0030] Specifically, the charged R1 groups in the ion-sensitive hydrogel of the present application can serve as salt-responsive sites, making the ion-sensitive hydrogel sensitive to ions in an ionic solution. Under the stimulation of external ions, the hydrogel can produce polarization due to electrostatic shielding.

[0031] In another embodiment, the electrolyte monomer includes:

[0032] One of methacrylate ion, acrylate ion or phosphate ion; wherein, the R 11 Selected from -H, -CH3 or -CH2CH3;

[0033] The non-electrolyte monomer includes:

[0034] In the present application, the electrolyte monomer is most preferably one or more of acryloyloxyethyltrimethylammonium chloride, methacryloyloxyethyltrimethylammonium chloride and 2-acrylamido-2-methylpropanesulfonic acid.

[0035] The non-electrolyte monomer is most preferably one or more of methyl acrylate, ethyl acrylate, methyl methacrylate and ethyl methacrylate.

[0036] The hydrogel provided herein is formed by copolymerization of electrolyte monomers and non-electrolyte monomers. The hydrophobic groups in the non-electrolyte monomers provide a hydrophobic effect, allowing the formation of a microphase-separated structure within the ion-sensitive hydrogel. Furthermore, the charged R1 groups in the ion-sensitive hydrogel provided herein can produce a significant polarization response when stimulated by external ions.

[0037] More specifically, the characteristic size of the copolymerization hydrogel of ethyl acrylate and acryloyloxyethyltrimethylammonium chloride is 21.78 nm; the characteristic size of the copolymerization hydrogel of ethyl acrylate and methacryloyloxyethyltrimethylammonium chloride is 27.51 nm; the characteristic size of the copolymerization hydrogel of ethyl acrylate and (3-acrylamidopropyl)trimethylammonium chloride is 27.77 nm; the characteristic size of the copolymerization hydrogel of ethyl acrylate and methacrylamidopropyltrimethylammonium chloride is 19.04 nm; and the characteristic size of the copolymerization hydrogel of methyl acrylate and acryloyloxyethyltrimethylammonium chloride is 19.12 nm.

[0038] The ion-sensitive hydrogel provided in this application does not undergo macroscopic phase separation. In this state, the ion-sensitive hydrogel appears white. For example, a hydrogel copolymerized with butyl acrylate and acryloyloxyethyltrimethylammonium chloride and a hydrogel copolymerized with ethyl acrylate and dimethyldiallylammonium chloride are used.

[0039] The second aspect of the present application provides a method for preparing the ion-sensitive hydrogel, comprising the following steps:

[0040] Step 1: mixing an electrolyte monomer or a precursor of the electrolyte monomer with a non-electrolyte monomer, an initiator, a cross-linking agent and an organic solvent to obtain a pre-reaction solution;

[0041] Alternatively, a precursor of an electrolyte monomer is mixed with a non-electrolyte monomer, an initiator, a cross-linking agent, and an organic solvent to obtain a pre-reaction solution;

[0042] Step 2: The pre-reaction solution is subjected to polymerization reaction to obtain a hydrogel;

[0043] Step 3: Soaking the hydrogel in water or an aqueous solution to swell until equilibrium is reached, thereby obtaining the ion-sensitive hydrogel.

[0044] More specifically, during the preparation of the ion-sensitive hydrogel of the present application, the electrolyte monomer or its precursor and the non-electrolyte monomer undergo a polymerization reaction and a crosslinking reaction simultaneously to form the ion-sensitive hydrogel. In step 1, the crosslinking agent is a polyolefin compound, preferably a difunctional crosslinker, more preferably N,N-methylenebisacrylamide; the molar concentration of the crosslinking agent is 0.2%-5%, preferably 1%, of the total molar concentration of the electrolyte monomer or its precursor and the non-electrolyte monomer.

[0045] The third aspect of the present application provides the use of the ion-sensitive hydrogel or the ion-sensitive hydrogel prepared by the preparation method in detecting the concentration of ion solutions.

[0046] Specifically, the ion-sensitive hydrogel can be used for detection of physiological environments, salt concentration change detection and / or strain detection in the fields of sensor patches, fiber fabrics, implantable sensor devices, etc.

[0047] A fourth aspect of the present application provides a device for detecting an ion solution, comprising a polarization detection system, a container, and an ion-sensitive hydrogel;

[0048] The ion-sensitive hydrogel is the above-mentioned ion-sensitive hydrogel;

[0049] The container is provided with a solution inlet, and the container is fixed on the platform of the polarization detection system;

[0050] The polarization detection system includes a polarizer, a digital camera, and a data analysis module. The polarizer is connected to the digital camera, and the digital camera is connected to the data analysis module. The polarization detection system is used to receive the polarized image.

[0051] The ion-sensitive hydrogel is disposed in the container;

[0052] The digital camera is arranged on the polarization detection platform and is opposite to the light source of the polarization detection system. The digital camera is used to receive the optical image of the polarization microscope; the data analysis module receives the optical image data of the digital camera to calculate and analyze the polarization information.

[0053] Specifically, the polarization detection system used in the present application is an existing conventional device that can detect the polarization phenomenon of a sample, which can be a self-assembled device or a commercially available device.

[0054] More specifically, the calculation and analysis of polarization information includes: ① selecting a plurality of different standard ion solutions with gradient concentrations, using the ion solution detection device of the present application to detect the grayscale values ​​of these ion solutions, and drawing a standard curve; ② using the ion solution detection device of the present application to detect the optical image of the ion solution to be tested, graying each optical image, calculating the average grayscale respectively, substituting the average grayscale into the standard curve respectively, and obtaining information about the concentration and type of the ion solution to be tested.

[0055] Specifically, the ion-sensitive hydrogel is a block structure. The present application does not limit the thickness of the ion-sensitive hydrogel, but the preferred thickness is 0.5-2 mm, preferably 0.5 mm.

[0056] Specifically, the method for detecting the concentration of an ion solution using the ion solution detection device of the present application includes:

[0057] 1. Use the ion solution detection device of the present application to test the optical images of ion solutions of different types with gradient concentrations, calculate the average grayscale of each, and establish a preset standard curve of ion solutions of different types with gradient concentrations;

[0058] 2. Place the ion-sensitive hydrogel in a container so that the light source of the polarizing microscope is aligned with the ion-sensitive hydrogel;

[0059] 3. Add the ion solution to be tested from the solution inlet, and then measure the optical image of the ion-sensitive hydrogel after being stimulated by the ion solution to be tested. Grayscale each optical image during the reaction time, calculate the average grayscale, and substitute the average grayscale into the preset standard curve to obtain information about the concentration and type of the ion solution to be tested.

[0060] The ion-sensitive hydrogel provided herein can produce significant polarization under the influence of ions in the environment. When stimulated by ions, the ion-sensitive hydrogel exhibits significant polarization on its surface and within its interior, as observed using a polarizing microscope. This polarization phenomenon gradually weakens and disappears over time.

[0061] The present application provides an ion-sensitive hydrogel, which is copolymerized by electrolyte monomers and non-electrolyte monomers. Wherein, the hydrophobic group in the non-electrolyte monomer can provide a hydrophobic effect so that the inside of the ion-sensitive hydrogel has a microphase separation structure, which is characterized by means of small-angle X-ray scattering (SAXS). The characteristic size structure of the hydrogel is nanometer level, and the diffusion time of salt between the two phases is much less than the diffusion time in the direction of the gel bulk material, so this type of gel material has a fast salt response characteristic. When the charged group in the polymer monomer of the preferred hydrogel is used, the inside of the ion-sensitive hydrogel has an electrostatic repulsion effect, which is sensitive to changes in ionic strength in the environment. When the stimulation of ions in the solution is felt, local volume contraction or expansion will occur after the stimulation of external ions is felt, thereby inducing the gel material to produce polarization phenomenon. BRIEF DESCRIPTION OF THE DRAWINGS

[0062] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art.

[0063] Figure 1 Schematic diagram of the preparation process of the ion-sensitive hydrogel provided in the examples of the present application;

[0064] Figure 2 The polarization phenomenon of the p(EA-co-DAC) ion-sensitive hydrogel in a salt solution provided in the embodiments of the present application;

[0065] Figure 3 Polarization phenomenon of different types of ion-sensitive hydrogels in saline solutions provided by the embodiments of the present application;

[0066] Figure 4 Polarization phenomenon of p(EA-co-DAC) ion-sensitive hydrogel in NaCl solutions with different ionic strengths provided in the embodiments of the present application;

[0067] Figure 5 Polarization phenomenon of the ion-sensitive hydrogel provided in the embodiments of the present application in different monovalent electrolyte solutions;

[0068] Figure 6 Polarization phenomenon of the ion-sensitive hydrogel provided in the embodiments of the present application in different multivalent salt solutions;

[0069] Figure 7 Data on the changes in length, width, and thickness of the ion-sensitive hydrogel provided in the examples of this application in a salt solution;

[0070] Figure 8 Polarizing microscope observation of the copolymerization gel of different hydrophobic monomers and acryloyloxyethyltrimethylammonium chloride in a salt solution provided in the examples of the present application;

[0071] Figure 9 Polarized microscope observation of the copolymerized gel of ethyl acrylate and different cationic monomers in a salt solution provided in the examples of the present application;

[0072] Figure 10 Polarizing microscope observation of the copolymerized gel of ethyl acrylate and different anionic monomers in a salt solution provided in the examples of the present application;

[0073] Figure 11 One-dimensional scattering curves of different copolymer gels provided in the examples of this application;

[0074] Figure 12 A summary of the characteristic dimensions of different copolymer gels provided in the examples of this application;

[0075] Figure 13 Polarized images of the p(EA-co-DAC) gel under different strains provided in the examples of this application. DETAILED DESCRIPTION

[0076] The present application provides an ion-sensitive hydrogel, a preparation method and application thereof, and an ion solution detection device, which are used to solve the technical defects of conventional hydrogels that are unable to detect the concentration of ion solutions due to their slow response rate to ion solutions and high ion concentration threshold.

[0077] The following is a clear and complete description of the technical solutions in the embodiments of this application. Obviously, the embodiments described are only part of the embodiments of this application, not all of them. Based on the embodiments of this application, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of this application.

[0078] The raw materials and reagents used in the following examples were all commercially available or homemade.

[0079] Example 1

[0080] This example provides the preparation of ion-sensitive hydrogels, see Figure 1 EA monomer (2M), DAC (electrolyte molar ratio of 10%), MBAA (cross-linking density molar ratio of 1% of monomer concentration) and photoinitiator were mixed to form ion-sensitive hydrogel by photoinitiation. The ion-sensitive hydrogel was then swelled in deionized water to prepare the ion-sensitive hydrogel. The specific preparation steps are as follows:

[0081] Step 1: Dissolve 1.820 g of ethyl acrylate EA, 0.484 g of acryloyloxyethyltrimethylammonium chloride DAC, 0.031 g of N,N-methylenebisacrylamide MBAA and 0.0030 g of α-ketoglutaric acid in DMSO and dilute to 10 mL to obtain a pre-reaction solution.

[0082] Step 2: Pour the pre-reaction solution into a glass mold, place the mold between two UV lamps, and irradiate with 365nm UV light for 8 hours to obtain an ion-sensitive hydrogel with a thickness of 0.5 mm. The ion-sensitive hydrogel has the structure shown in the following formula:

[0083]

[0084] Step 3: The ion-sensitive hydrogel from Step 2 was placed in 200 mL of deionized water and soaked until the ion-sensitive hydrogel reached swelling equilibrium. The ion-sensitive hydrogel (labeled as p(EA-co-DAC) gel) was then removed from the solution. The characteristic size of the microphase separation structure of p(EA-co-DAC) in this example was determined to be 21.78 nm using small-angle X-ray characterization.

[0085] Example 2

[0086] The preparation diagram of the ion-sensitive hydrogel in this embodiment is shown in FIG. Figure 1 As shown, the specific preparation steps are similar to those in Example 1, except that the ion-sensitive hydrogel raw material monomers use 1.5653 g methyl acrylate MA and 0.484 g acryloyloxyethyltrimethylammonium chloride DAC to prepare the ion-sensitive hydrogel (labeled as p(MA-co-DAC) gel).

[0087] The characteristic size of the microphase separation structure of p(MA-co-DAC) in this example was determined to be 19.12 nm by small-angle X-ray characterization.

[0088] Example 3

[0089] The preparation diagram of the ion-sensitive hydrogel in this embodiment is shown in FIG. Figure 1 As shown, the specific preparation steps are similar to those in Example 1, except that the ion-sensitive hydrogel raw material monomers use 1.5653 g methyl acrylate EA and 0.554 g methacryloyloxyethyltrimethylammonium chloride DMC to prepare ion-sensitive hydrogel (labeled as p(EA-co-DMC) gel).

[0090] The characteristic size of the microphase separation structure of p(EA-co-DMC) in this example was determined to be 27.51 nm by small-angle X-ray characterization.

[0091] Example 4

[0092] The preparation diagram of the ion-sensitive hydrogel in this embodiment is shown in FIG. Figure 1 As shown, the specific preparation steps are similar to those in Example 1, except that the ion-sensitive hydrogel raw material monomers use 1.5653 g methyl acrylate EA and 0.551 g (3-acrylamidopropyl)trimethylammonium chloride APTC to prepare ion-sensitive hydrogel (labeled as p(EA-co-APTC) gel).

[0093] The characteristic size of the microphase separation structure of p(EA-co-APTC) in this example was determined to be 27.68 nm by small-angle X-ray characterization.

[0094] Example 5

[0095] The preparation diagram of the ion-sensitive hydrogel in this embodiment is shown in FIG. Figure 1 As shown, the specific preparation steps are similar to those in Example 1, except that the ion-sensitive hydrogel raw material monomers use 1.5653 g methyl acrylate EA and 0.883 g propyltrimethylammonium chloride MPTC to prepare the ion-sensitive hydrogel (labeled as p(EA-co-MPTC) gel).

[0096] The characteristic size of the microphase separation structure of p(EA-co-MPTC) in this example was determined to be 21.16 nm by small-angle X-ray characterization.

[0097] Example 6

[0098] The preparation diagram of the ion-sensitive hydrogel in this embodiment is shown in FIG. Figure 1 As shown, the specific preparation steps are similar to those in Example 1, except that the ion-sensitive hydrogel raw material monomers use 1.5653 g methyl acrylate EA and 1.079 g ethyl dimethyl benzyl ammonium chloride DABC to prepare the ion-sensitive hydrogel (labeled as p(EA-co-DABC) gel).

[0099] Example 7

[0100] The preparation diagram of the ion-sensitive hydrogel in this embodiment is shown in FIG. Figure 1 As shown, the specific preparation steps are similar to those in Example 1, except that the ion-sensitive hydrogel raw material monomers use 2.3304 g butyl acrylate BA and 0.5191 g acryloyloxyethyltrimethylammonium chloride DAC to prepare the ion-sensitive hydrogel (labeled as p(BA-co-DAC) gel).

[0101] Example 8

[0102] The preparation diagram of the ion-sensitive hydrogel in this embodiment is shown in FIG. Figure 1As shown, the specific preparation steps are similar to those in Example 1, except that the ion-sensitive hydrogel raw material monomers use 1.5653 g methyl acrylate EA and 0.5179 g 2-acrylamide-2-methylpropanesulfonic acid AMPS to prepare ion-sensitive hydrogel (labeled as p(EA-co-AMPS) gel).

[0103] Example 9

[0104] The preparation diagram of the ion-sensitive hydrogel in this embodiment is shown in FIG. Figure 1 As shown, the specific preparation steps are similar to those in Example 1, except that the ion-sensitive hydrogel raw material monomers use 1.5653 g methyl acrylate EA and 0.5153 g sodium styrene sulfonate NaSS to prepare the ion-sensitive hydrogel (labeled as p(EA-co-NaSS) gel).

[0105] Example 10

[0106] The preparation diagram of the ion-sensitive hydrogel in this embodiment is shown in FIG. Figure 1 As shown, the specific preparation steps are similar to those in Example 1, except that the ion-sensitive hydrogel raw material monomers use 1.5653 g methyl acrylate EA and 0.942 g ethyl dimethyl benzyl ammonium chloride DABC to prepare the ion-sensitive hydrogel (labeled as p(EA-co-DABC) gel).

[0107] The characteristic size of the microphase separation structure of p(EA-co-DABC) in this example was determined to be 21 nm by small-angle X-ray characterization.

[0108] Comparative Example 1

[0109] The preparation diagram of the hydrogel in this comparative example is shown in FIG. Figure 1 As shown, the specific preparation steps are similar to those in Example 1, except that the hydrogel raw material monomers use 1.820 g methyl methacrylate MMA and 0.484 g acryloyloxyethyltrimethylammonium chloride DAC to prepare a hydrogel (labeled as p(MMA-co-DAC) gel).

[0110] The characteristic size of the microphase separation structure of the comparative example p(MMA-co-DAC) was determined to be 52.06 nm by small-angle X-ray characterization.

[0111] Comparative Example 2

[0112] This comparative example provides a hydrogel, and the specific preparation steps are as follows:

[0113] Step 1: Dissolve 2.02 g of ethyl acrylate EA, 0.031 g of N,N-methylenebisacrylamide, and 0.0030 g of α-ketoglutaric acid in DMSO and dilute to 10 mL to obtain a pre-reaction solution.

[0114] Step 2: Pour the pre-reaction solution into a glass mold, place the mold between two UV lamps, and irradiate with 365nm UV light for 8 hours to obtain a gel with a thickness of 0.5mm. The gel has the structure shown in the following formula:

[0115]

[0116] Step 3: Place the gel prepared in step 2 in 200 mL of anhydrous ethanol and soak until the gel reaches swelling equilibrium, then remove the gel from the solution.

[0117] Step 4: The gel from step 3 was transferred to 200 mL of deionized water for swelling to obtain a hydrogel (labeled as pEA gel). The characteristic dimensions of the microphase separation structure of the pEA gel in this example were characterized by small-angle X-ray diffraction, indicating that there was no obvious ordered characteristic structure inside the pEA gel.

[0118] Step 5. Prepare acrylamide pAAm gel according to the method of steps 1 to 4 above. The method for preparing pAAm gel is different from the above method in that acrylamide AAm is used instead of ethyl acrylate EA as the gel material monomer. Except for the amount of acrylamide used being 1.434 g, the other steps and parameters are the same as above to obtain a hydrogel (labeled as pAAm gel).

[0119] Step 6. Prepare acryloyloxyethyltrimethylammonium chloride pDAC gel according to the method of steps 1 to 4 above. The method for preparing pDAC gel is different from the above method in that acryloyloxyethyltrimethylammonium chloride DAC is used as the gel material monomer instead of N,N-methylenebisacrylamide MBA. Except that the amount of acryloyloxyethyltrimethylammonium chloride is 0.0039 g, the other steps and parameters are the same as above to obtain a hydrogel (labeled as pDAC gel).

[0120] Comparative Example 3

[0121] The preparation diagram of the hydrogel in this comparative example is shown in FIG. Figure 1 The specific preparation steps are similar to those of Example 1, except that the gel material monomers use 1.01g ethyl acrylate EA and 2.42g acryloyloxyethyl trimethyl ammonium chloride DAC. No photoinitiator is added and the photoinitiation reaction is performed to prepare the gel of Comparative Example 2.

[0122] The characteristic size of the microphase separation structure of the hydrogel in this comparative example has no obvious characteristic diffraction peak after being characterized by small-angle X-ray, that is, there is no obvious ordered characteristic structure inside the gel of comparative example 2.

[0123] Comparative Example 4

[0124] The preparation diagram of the hydrogel in this comparative example is shown in FIG. Figure 1As shown, the specific preparation steps are similar to those in Example 1, except that step 3 is omitted in the preparation process of the gel material, and the gel of Comparative Example 3 is prepared.

[0125] The characteristic size of the microphase separation structure of the hydrogel in this comparative example has no obvious characteristic diffraction peak after being characterized by small-angle X-ray, that is, there is no obvious ordered characteristic structure inside the gel of comparative example 3.

[0126] Comparative Example 5

[0127] The preparation diagram of the hydrogel in this comparative example is shown in FIG. Figure 1 As shown, the specific preparation steps are similar to those in Example 1, except that 2.0753 g of ethyl methacrylate EMA and 0.484 g of acryloyloxyethyltrimethylammonium chloride DAC are used as the hydrogel raw material monomers to prepare the hydrogel (labeled as p(EMA-co-DAC) gel).

[0128] Comparative Example 6

[0129] The preparation diagram of the hydrogel in this comparative example is shown in FIG. Figure 1 As shown, the specific preparation steps are similar to those in Example 1, except that 1.5653 g of methyl acrylate EA and 0.404 g of dimethyldiallyl ammonium chloride DADMAC are used as the hydrogel raw material monomers to prepare the hydrogel (labeled as p(EA-co-DADMAC) gel).

[0130] Comparative Example 7

[0131] The preparation diagram of the hydrogel in this comparative example is shown in FIG. Figure 1 As shown, the specific preparation steps are similar to those in Example 1, except that 1.5653 g of methyl acrylate EA and 0.180 g of acrylic acid AAc are used as the hydrogel raw material monomers to prepare the hydrogel (labeled as p(EA-co-AAc) gel).

[0132] Test Case

[0133] The properties of the hydrogels prepared in the above examples and comparative examples were tested, specifically including:

[0134] 1. Polarizing microscope test: The salt response of p(EA-co-DAC) gel in Example 1 of the present application to 0.1M NaCl was recorded and observed using a polarizing microscope, and the recording time points were 0min, 1min, 2min, 3min, 5min, 7min, 9min, 11min, 13min, 15min, and 20min. The observed sample size was uniformly 0.75mm in thickness, and the width was controlled at about 1mm. In order to prevent the influence of water loss on the gel before directly transferring to the salt solution environment, the gel was pre-soaked in a culture dish filled with 5mL of deionized water before adding the salt solution, and then the NaCl solution was added to start the timing test. Due to dilution, the ionic strength of the added NaCl solution should be twice the test ionic strength. The results are as follows Figure 2 shown.

[0135] Figure 2 This is the polarization phenomenon of p(EA-co-DAC) gel in NaCl solution. Figure 2 As shown, after the addition of the salt solution, the p(EA-co-DAC) gel exhibited significant polarization under a polarizing microscope. Observing the polarization phenomenon 20 minutes after the addition of the salt solution revealed that, under the stimulation of salt, the polymer chains within and on the surface of the p(EA-co-DAC) gel exhibited distinctly different arrangements, resulting in the p(EA-co-DAC) gel exhibiting different polarization colors in these two locations. Over time, at approximately 13 minutes, the structural differences between the surface and interior of the p(EA-co-DAC) gel gradually disappeared, and the overall p(EA-co-DAC) gel structure changed from an ordered molecular arrangement to a disordered state. Furthermore, because the p(EA-co-DAC) gel contains electrolyte components, the electrostatic shielding effect of NaCl causes the electrolyte chain segments to fold, resulting in the observed volume contraction of the p(EA-co-DAC) gel.

[0136] 2. According to step 1, the salt response of p(EA-co-DAC) gel, pEA gel, pDAC gel and pAAm gel in 0.1M NaCl was tested. The response process was recorded and observed using a polarizing microscope. The recording time points were 0min, 1min, 5min and 20min. The sample size was uniformly 0.75mm in thickness and about 1mm in width. The results are shown in Figure 2. Figure 3 shown.

[0137] Figure 3 This is the polarization phenomenon of different types of hydrogels in salt solutions. Figure 3As shown in the figure, it was found that only p(EA-co-DAC) gel showed optical salt response characteristics. Among them, pEA gel and pAAm gel are neutral and uncharged hydrogels, and pDAC gel is a positively charged hydrogel. When the gel is placed in a 0.1M NaCl solution, it can be seen that pAAm gel and pEA gel do not show polarization phenomenon, which indicates that the arrangement of their polymers has not changed in the salt solution environment. However, due to its charged characteristics, pDAC gel can be Figure 3 It can be found that the gel quickly shrank in volume after the addition of salt solution, but still did not show polarization phenomenon.

[0138] 3. According to step 1, the salt response of p(EA-co-DAC) gel in 0.001M NaCl, 0.01M NaCl, 0.05M NaCl, 0.1M NaCl, 0.5M NaCl, 1M NaCl and 2M NaCl was tested respectively. The response process was recorded and observed using a polarizing microscope. The recording time points were 0min, 1min, 9min and 20min. The sample size observed was uniformly 0.75mm in thickness and controlled at about 1mm in width. The results are as follows. Figure 4 shown.

[0139] Figure 4 This is the polarization phenomenon of p(EA-co-DAC) gel in NaCl solutions with different ionic strengths. Figure 4 As shown, the copolymer gel begins to exhibit polarization in a NaCl solution with an ionic strength of 0.01M, and when the ionic strength increases to 0.05M, the gel exhibits a distinct optical response. Compared to electrolyte gels, this polarization phenomenon makes the copolymer gel more sensitive to low salt concentrations. Furthermore, as the ionic strength increases, the gel's orientation behavior becomes more intense, the orientation color deepens, and the duration of polarization increases. It can be seen that the gel in a 2M salt solution still exhibits significant polarization after 20 minutes.

[0140] 4. According to step 1, the salt response of p(EA-co-DAC) gel to HCl, LiCl, NaCl, KCl and NH4Cl at the same concentration was tested respectively. The response process was recorded and observed using a polarizing microscope. The recording time points were 0min, 1min, 9min and 20min. The sample size was uniformly 0.75mm in thickness and about 1mm in width. The results are shown in Figure 4. Figure 5 shown.

[0141] Figure 5 Polarization phenomenon of p(EA-co-DAC) gel in different monovalent electrolyte solutions. Figure 5The polarization phenomena of the gel in five monovalent salt solutions were summarized. The gel showed almost the same behavior to all salts and there was no difference in the subsequent process.

[0142] 5. According to step 1, test the p(EA-co-DAC) gel in the presence of the same concentration of NaCl, CaCl2, Na2SO4, Na4P2O7 and Na5P3O 10 The salt response was recorded and observed using a polarizing microscope at 0 min, 1 min, 9 min, and 20 min. The sample size was uniformly 0.75 mm in thickness and about 1 mm in width. Figure 6 shown.

[0143] Figure 6 The polarization phenomenon of p(EA-co-DAC) hydrogel in different polyvalent salt solutions. The hydrogel exhibited some polarization in all salt solutions. Polarizing microscopic observations at 20 minutes revealed that the gel's interior and exterior had not yet reached equilibrium under the influence of the polyvalent anionic salts, resulting in a very strong optical response.

[0144] 6. Test the changes in length, width and thickness of p(EA-co-DAC) gel in salt solution. A batch of p(EA-co-DAC) gel was soaked in 0.1mol / LNaCl solution for swelling. A portion was taken out at different time points to measure the length, width and height. The results are as follows: Figure 7 shown.

[0145] Figure 7 is the data of the length, width and thickness changes of the hydrogel in salt solution. Figure 7 As shown in the figure, the swelling data show that the length, width, and thickness of the gel show almost the same change trend, and the shrinkage rate is at the same level at the final equilibrium. Based on the above experimental results, the p(EA-co-DAC) gel exhibits isotropic shrinkage properties in salt solution.

[0146] 7. According to step 1, the salt response of p(EA-co-DAC) gel, p(MA-co-DAC) gel, p(MMA-co-DAC) gel, p(BA-co-DAC) gel and p(EMA-co-DAC) gel in 0.1M NaCl was tested respectively. The response process was recorded and observed using a polarizing microscope. The recording time points were 0min, 1min, 9min and 20min. The sample size observed was uniformly 0.75mm in thickness and controlled at about 1mm in width. The results are as follows. Figure 8 shown.

[0147] Figure 8Polarizing microscopy observations of different hydrophobic monomers and acryloyloxyethyltrimethylammonium chloride (DAC) copolymer gels in saline solution. The hydrophobic monomers used in the experiment include methyl acrylate (MA), ethyl acrylate (EA), butyl acrylate (BA), methyl methacrylate (MMA), and ethyl methacrylate (EMA). Figure 8 The polarization phenomenon of different copolymer gels was demonstrated, and the results showed that only p(MA-co-DAC) gel and p(EA-co-DAC) gel exhibited optical salt response behavior. After preparation, p(BA-co-DAC) gel and p(EMA-co-DAC) gel were transferred to water and completely phase separated. The two gels did not show orientation behavior. In addition, p(MMA-co-DAC) gel underwent uneven phase separation and did not show polarization behavior in salt solution. The above results indicate that gels with macroscopic phase separation will lose the characteristics of optical salt response. It can be seen that the optical salt response characteristics have certain requirements on the size of the phase separation of the copolymer gel.

[0148] 8. According to step 1, the salt response of p(EA-co-DAC) gel, p(EA-co-DMC) gel, p(EA-co-APTC) gel, p(EA-co-MPTC) gel, p(EA-co-DABC) gel and p(EA-co-DADMAC) gel in 0.1M NaCl was tested respectively. The response process was recorded and observed using a polarizing microscope. The recording time points were 0min, 1min, 9min and 20min. The sample size observed was uniformly 0.75mm in thickness and controlled at about 1mm in width. The results are as follows. Figure 9 shown.

[0149] Figure 9 This is the polarizing microscope observation phenomenon of the copolymerized gel of ethyl acrylate EA and different cationic monomers in salt solution. The electrolyte monomers used include acryloyloxyethyl trimethyl ammonium chloride DAC, methacryloyloxyethyl trimethyl ammonium chloride DMC, (3-acrylamidopropyl) trimethyl ammonium chloride APTC, methacrylamidopropyl trimethyl ammonium chloride MPTC, acryloyloxyethyl dimethyl benzyl ammonium chloride DABC and dimethyl diallyl ammonium chloride DADMAC. Except for the macroscopic phase separation of p(EA-co-DADMAC), the prepared gels are all transparent, and the gel does not show polarization. The other copolymerized gels all show very obvious polarization, and it can be observed that the polarization phenomenon of p(EA-co-DABC) gel is maintained for a longer time.

[0150] 9. According to step 1, the salt response of p(EA-co-AMPS) gel, p(EA-co-NaSS) gel, and p(EA-co-AAc) gel in 0.1M NaCl was tested respectively. The response process was recorded and observed using a polarizing microscope. The recording time points were 0min, 1min, 9min, and 20min. The sample size observed was uniformly 0.75mm in thickness and controlled at about 1mm in width. The results are as follows. Figure 10 shown.

[0151] Figure 10 Polarizing microscopy observations of copolymerized gels of ethyl acrylate (EA) and different anionic monomers in a salt solution. The electrolyte monomers used included acrylic acid (AAc), sodium p-styrenesulfonate (NaSS), and 2-acrylamido-2-methylpropanesulfonic acid (AMPS). The p(EA-co-AAc) gel exhibited complete phase separation after preparation and therefore did not exhibit polarization. Both the p(EA-co-NaSS) gel and the p(EA-co-AMPS) gel exhibited significant polarization, but the polarization of the p(EA-co-NaSS) gel was weaker.

[0152] 10. The characteristic size of the microphase separation structure of the hydrogel prepared in the present embodiment was characterized by small angle X-ray scattering (SAXS). The small angle X-ray scattering (SAXS) test was carried out at the BL19U2 beamline of the Shanghai Synchrotron Radiation Facility. The wavelength of the beam during the test was The beam energy is 12 keV, and the distance from the sample to the detector is 5765.498731 mm.

[0153] Static sample testing uses a simple polyimide membrane loaded with gel samples. The test results are converted from two-dimensional images to one-dimensional curves using Fit2D for data analysis.

[0154] 11. The one-dimensional scattering curves of the hydrogels of the above examples (p(EA-co-DAC) gel, p(MA-co-DAC) gel, p(BA-co-DAC) gel, p(MMA-co-DAC) gel, p(EA-co-MPTC) gel, p(EA-co-APTC) gel, p(EA-co-DPTC) gel, p(EA-co-DMC) gel and p(EA-co-DADMAC) gel) were tested respectively by conventional means. The results are shown in the figure. Figure 11 shown.

[0155] Figure 11The following are the one-dimensional scattering curves for different copolymer gels. Copolymer gels that have undergone macroscopic phase separation generally exhibit higher scattering intensities within the scanning range. p(MMA-co-DAC) gel and p(EA-co-DADMAC) gel do not exhibit distinct scattering peaks. Despite complete phase separation, the p(BA-co-DAC) gel still exhibits characteristic peaks in its one-dimensional scattering curve, indicating that the gel still possesses a partially ordered structure.

[0156] 12. The microphase separation structure characteristic dimensions of the hydrogels of the above embodiments (respectively, p(EA-co-DAC) gel, p(EA-co-DMC) gel, p(MA-co-DAC) gel, p(BA-co-DAC) gel, p(MMA-co-DAC) gel, p(EA-co-MPTC) gel, p(EA-co-APTC) gel, p(EA-co-DPTC) gel and p(EA-co-DMC) gel) were tested by conventional small-angle X-ray scattering testing methods, and the phase structure dimensions of these hydrogels were calculated. The results are shown in FIG. Figure 12 shown.

[0157] Figure 12 The characteristic dimensions of different copolymer gels are summarized. Calculations indicate that the gel phase structure is mostly within the 15 to 30 nm range. Hydrophobic-electrolyte monomer copolymer gels prepared within this range generally exhibit optical salt-responsive properties, which can be used as a design strategy for optical salt-responsive gels.

[0158] 13. Test the polarization of p(EA-co-DAC) gel under different strains. Place the p(EA--co-DAC) gel under a polarizer and stretch it. The color change of the gel can be seen through the polarizer. The results are as follows: Figure 13 shown.

[0159] Figure 13 Polarized images of p(EA--co-DAC) gels at different strains. At 0% strain, the gel shows no obvious orientation color under circularly polarized light. At 5% strain, a light blue orientation color appears on the gel surface. As the strain increases, the gel's orientation gradually becomes more distinct.

[0160] The above is only a preferred embodiment of the present application. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present application. These improvements and modifications should also be regarded as the scope of protection of the present application.

Claims

1. An application of an ion-sensitive hydrogel in detecting the concentration of an ion solution, characterized in that: The ion-sensitive hydrogel is formed by polymerizing electrolyte monomers and non-electrolyte monomers; The ion-sensitive hydrogel is measured by small-angle X-ray scattering, and the microphase separation structure inside the hydrogel has a structural characteristic size of 10-30 nm; the structural characteristic size refers to the distance between phases of the microphase separation structure formed by the hydrophobic groups in the non-electrolyte monomers inside the hydrogel; The application utilizes the ion-sensitive hydrogel to produce local volume contraction or expansion after being stimulated by external ions, thereby inducing the polarization phenomenon generated by the gel material for detection; The chemical structure of the ion-sensitive hydrogel has a structure shown in formula (I) or formula (II); Formula (I); Formula (II); Wherein, when R1 is selected as a cation, R1 includes quaternary ammonium ion, quaternary phosphonium ion, sulfonium ion, imidazolium ion, pyridinium ion, piperidinium ion and pyrrolium ion; when R1 is selected as an anion, R1 includes carboxylate ion, sulfonate ion, sulfinic acid ion and phosphate ion; R2 is a C1~C20 alkyl group, a phenyl group or a C1~C20 alkoxy group; R3 is a phenyl group, a C0~C20 alkyl group, or a C0~C20 alkoxy group; The R4 is phenyl, C0~C20 alkyl, C0~C20 alkoxy, or ;1≤c≤20,1≤d≤20; The polymer structure represented by the formula (I) does not contain R5 and / or R6; or the R5 and R6 are independently selected from an amide group, an ester group, a methylene group or a phenyl group; The R7 and R8 are each independently selected from hydrogen or methyl; Wherein, the R9 and the R 10 Each independently selected from methyl, ethyl or phenyl; The polymer having the structure represented by the formula (I) does not include the copolymer of 2-phenoxyethyl acrylate or 2-phenoxyethyl methacrylate and 2-acryloyloxyethyltrimethylammonium chloride or 2-methacryloyloxyethyltrimethylammonium chloride.

2. The use according to claim 1, characterized in that The concentration of the ionic solution is 0.001 M-5 M.

3. The use according to claim 1, characterized in that The ionic solution includes one or more of an acid, a base, a salt and an organic amine.

4. The use according to claim 1, characterized in that The ratio of the total molar number of the electrolyte monomers to the total molar number of the non-electrolyte monomers is (0.5:9.5) to (5:5).

5. The use according to any one of claims 1 to 4, characterized in that The preparation method of the ion-sensitive hydrogel comprises the following steps: Step 1: mixing an electrolyte monomer or a precursor of the electrolyte monomer with a non-electrolyte monomer, an initiator, a cross-linking agent and an organic solvent to obtain a pre-reaction solution; Alternatively, a precursor of an electrolyte monomer is mixed with a non-electrolyte monomer, an initiator, a cross-linking agent, and an organic solvent to obtain a pre-reaction solution; Step 2: The pre-reaction solution is subjected to polymerization reaction to obtain a hydrogel; Step 3: Soaking the hydrogel in water or an aqueous solution to swell until equilibrium is reached, thereby obtaining the ion-sensitive hydrogel according to any one of claims 1 to 4.

6. A device for detecting an ion solution, characterized in that: including a polarized light detection system, a container, and an ion-sensitive hydrogel; The container is provided with a solution inlet, and the container is fixed on the platform of the polarization detection system; The polarization detection system includes a polarizer, a digital camera, and a data analysis module. The polarizer is connected to the digital camera, and the digital camera is connected to the data analysis module. The polarization detection system is used to receive the polarized image. The ion-sensitive hydrogel is disposed in the container; The digital camera is disposed on the polarization detection platform and opposite to the light source of the polarization detection system. The digital camera is used to receive the optical image of the polarization microscope. The data analysis module receives the optical image data of the digital camera to calculate and analyze the polarization information. The ion-sensitive hydrogel is formed by polymerizing electrolyte monomers and non-electrolyte monomers; The ion-sensitive hydrogel is measured by small-angle X-ray scattering, and the microphase separation structure inside the hydrogel has a structural characteristic size of 10-30 nm. The structural size characteristic refers to the distance between phases of the microphase separation structure formed by the hydrophobic groups in the non-electrolyte monomers inside the hydrogel; The chemical structure of the ion-sensitive hydrogel has a structure shown in formula (I) or formula (II); ； Wherein, when R1 is selected as a cation, R1 includes quaternary ammonium ion, quaternary phosphonium ion, sulfonium ion, imidazolium ion, pyridinium ion, piperidinium ion and pyrrolium ion; when R1 is selected as an anion, R1 includes carboxylate ion, sulfonate ion, sulfinic acid ion and phosphate ion; R2 is a C1-C20 alkyl group, a phenyl group, or a C1-C20 alkoxy group; R3 is a phenyl group, a C0-C20 alkyl group, or a C0-C20 alkoxy group; The R4 is phenyl, C0-C20 alkyl, C0-C20 alkoxy, 1≤c≤20, 1≤d≤20; The polymer structure represented by the formula (I) does not contain R5 and / or R6; or the R5 and R6 are independently selected from an amide group, an ester group, a methylene group or a phenyl group; The R7 and R8 are each independently selected from hydrogen or methyl; Wherein, the R9 and the R 10 Each independently selected from methyl, ethyl or phenyl; The polymer having the structure represented by the formula (I) does not include the copolymer of 2-phenoxyethyl acrylate or 2-phenoxyethyl methacrylate and 2-acryloyloxyethyltrimethylammonium chloride or 2-methacryloyloxyethyltrimethylammonium chloride.

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