Zirconium ion-crosslinked thermosensitive hydrogel with environment-responsive adhesion and preparation method thereof

Abstract

The present invention provides an environmentally responsive adhesive zirconium ion-crosslinked thermosensitive hydrogel and a preparation method thereof, which can significantly improve the adhesion performance of the hydrogel, form strong adhesion with the substrate surface, and can realize a cyclic reversible process of strong adhesion and de-adhesion by changing environmental conditions. The preparation method provided by the present invention includes: Step 1, stirring and dissolving sodium poly(2-acrylamido-2-methylpropanesulfonate) PNaAMPS, N-isopropylacrylamide NIPAm, acrylamide AAm, a crosslinking agent, an initiator and deionized water under light-shielding conditions to obtain a uniform mixed solution, and obtaining a PNaAMPS / P(NIPAM-co-AAm) double-network thermosensitive hydrogel TDN after ultraviolet light polymerization; Step 2, putting the TDN obtained in Step 1 into a zirconium ion solution, and then into a high-temperature deionized water solution, and obtaining an environmentally responsive adhesive zirconium ion-crosslinked thermosensitive hydrogel TDN-Zr after swelling equilibrium.

Description

Technical Field

[0001] The present invention belongs to the technical field of gel materials, and particularly relates to a zirconium ion cross-linked thermosensitive hydrogel with environmental-responsive adhesion and a preparation method thereof. Background Art

[0002] Hydrogels are a widely used soft and wet material, which have characteristics such as high deformability, similarity to biological tissue structures, and great potential for functionalization, and are widely used in fields such as tissue adhesives and wound dressings. Traditional hydrogel materials used for adhesives have a hydration layer on their surface due to their high water content, which prevents their adhesion to the substrate surface, and often has a poor adhesion effect, and it is even more difficult to achieve an effective reversible adhesion effect. Therefore, designing a hydrogel adhesive material with repeated reversible strong adhesion performance has application prospects in biomedical tissue adhesion gels.

[0003] Han et al. [Han L, Wang M, Prieto-Lopez L O, et al. Self-hydrophobization ina dynamic hydrogel for creating nonspecific repeatable underwater adhesion[J]. Advanced Functional Materials, 2020, 30(7):1907064.] passed Fe 3+A dynamic self-hydrophobic surface was induced to prepare a dynamic hydrogel that can be repeatedly and stably adhered to various dry / wet substrates underwater for a long time. The hydrogel with a hydrophilic surface was immersed in an iron ion solution to induce the rearrangement of supramolecular functional groups on the surface, so that the hydrogel formed a hydrophobic surface. When the hydrogel contacted the substrate surface underwater, the hydrophobic functional groups could exclude the water molecules on the substrate surface to achieve full contact, and the hydrogel could adhere quickly and reversibly underwater through hydrogen bonds, hydrophobic interactions, etc. However, the adhesion strength of this type of hydrogel is not high, and it is difficult to achieve effective reversible adhesion with the surface of dry substrates. Peng et al. [Peng Zhiping, Zhu Hekang, Yang Yue, Wang Ji, Fang Qian. Preparation method of a temperature-responsive adhesive injectable hydrogel [P]. CN108929412B, 2020-10-23.] designed a preparation method of a temperature-responsive adhesive injectable hydrogel. Using dopamine methacrylamide (DMA) as an adhesive monomer, 2-(2-methoxyethoxy)ethyl methacrylate (MEO2MA) and oligo(ethylene glycol) methyl ether methacrylate (OEGMA) as thermosensitive monomers, temperature-responsive hydrogels with different dopamine contents were synthesized. The prepared hydrogel is based on its temperature-responsive adhesion property that the adhesion strength increases with the increase of temperature, and can be applied to fields such as tissue adhesives. However, only the change of adhesion strength in a higher temperature environment was discussed and the adhesion strength was low. Therefore, the currently reported temperature-responsive adhesive hydrogels are difficult to achieve high adhesion strength and effective reversible adhesion in a high-temperature environment in practical applications. Summary of the Invention

[0004] The present invention is made to solve the above problems, and aims to provide a zirconium ion-crosslinked thermosensitive hydrogel with a simple process, easy operation, readily available raw materials, low cost and excellent environmentally responsive reversible strong adhesion, and a preparation method thereof.

[0005] In order to achieve the above object, the present invention adopts the following scheme:

[0006] <Method>

[0007] The present invention provides a preparation method of an environmentally responsive adhesive zirconium ion-crosslinked thermosensitive hydrogel, which is characterized by including:

[0008] Step 1: Dissolve sodium poly(2-acrylamido-2-methylpropanesulfonate) PNaAMPS, N-isopropylacrylamide NIPAm, acrylamide AAm, a crosslinking agent, an initiator and deionized water under light-shielding conditions by stirring to obtain a uniform mixed solution, and obtain a PNaAMPS / P(NIPAM-co-AAm) double-network thermosensitive hydrogel TDN after ultraviolet polymerization;

[0009] Step 2: Put the double-network thermosensitive hydrogel TDN obtained in Step 1 into a zirconium ion solution, and then into a high-temperature deionized aqueous solution. After swelling equilibrium, a zirconium ion-crosslinked thermosensitive hydrogel TDN-Zr with environmentally responsive adhesion is obtained.

[0010] Preferably, the method for preparing the zirconium ion-crosslinked thermosensitive hydrogel with environmentally responsive adhesion provided by the present invention may further have the following characteristics: In Step 1, PNaAMPS is obtained by dissolving 2-acrylamido-2-methylpropanesulfonic acid AMPS, sodium hydroxide NaOH, a crosslinking agent, and an initiator in deionized water, stirring in the dark to obtain a uniform mixed solution, pouring it into a parallel-plate glass mold, and subjecting it to ultraviolet light polymerization to obtain a poly(2-acrylamido-2-methylpropanesulfonic acid sodium) PNaAMPS hydrogel. After drying to a constant weight in a vacuum drying oven, it is ground with a high-speed ball mill and sieved to obtain PNaAMPS microgel powder with a particle size of 10-200 μm; wherein, the AMPS concentration is 3.98-4.02 mol / L -1 ; the concentration of the NaOH solution is 1 mol / L -1 ; the crosslinking agent is N,N'-methylenebisacrylamide MBAA, and the percentage of the crosslinking agent in the total molar amount of the monomers is 0.4%; the photoinitiator is 2-ketoglutaric acid KA, and the percentage of the photoinitiator in the total molar amount of the monomers is 0.1%.

[0011] Preferably, the method for preparing the zirconium ion-crosslinked thermosensitive hydrogel with environmentally responsive adhesion provided by the present invention may further have the following characteristics: In the mixed solution of Step 1, the NIPAm concentration is 3.48-3.52 mol / L -1 , the AAm concentration is 0.48-0.52 mol / L -1 , the crosslinking agent is N,N'-methylenebisacrylamide MBAA, and the percentage of the crosslinking agent in the total molar amount of the monomers is 0.1%; the photoinitiator is 2-ketoglutaric acid KA, and the percentage of the photoinitiator in the total molar amount of the monomers is 0.01%.

[0012] Preferably, the method for preparing the zirconium ion-crosslinked thermosensitive hydrogel with environmentally responsive adhesion provided by the present invention may further have the following characteristics: In Step 1, the temperature during stirring is room temperature, and the stirring time is 30-40 min.

[0013] Preferably, the zirconium ion-crosslinked thermosensitive hydrogel with environmentally responsive adhesion provided by the present invention may further have the following characteristics: In Step 1, the conditions for illumination under ultraviolet light are: illumination for 8-10 h under an ultraviolet lamp with a wavelength of 365 nm and a power of 15 W.

[0014] Preferably, the method for preparing the zirconium ion-crosslinked thermosensitive hydrogel with environmentally responsive adhesion provided by the present invention may further have the following characteristics: The double-network thermosensitive hydrogel TDN in Step 1 is soaked in deionized water to remove unreacted monomers, and then enters Step 2.

[0015] Preferably, the method for preparing the environmentally responsive adhesive zirconium ion cross-linked thermosensitive hydrogel provided by the present invention may further have the following characteristics: in step 2, the concentration of the zirconium ion solution is 0.1 to 0.5 mol / L -1 , and the soaking time in the zirconium ion solution is 24 h.

[0016] Preferably, the method for preparing the environmentally responsive adhesive zirconium ion cross-linked thermosensitive hydrogel provided by the present invention may further have the following characteristics: in step 2, the high temperature refers to above 70 °C, and the soaking time in the high-temperature deionized water is 48 h.

[0017] <gel>

[0018] Furthermore, the present invention also provides an environmentally responsive adhesive zirconium ion cross-linked thermosensitive hydrogel prepared by the above <method>.

[0019] Preferably, the method for preparing the environmentally responsive adhesive zirconium ion cross-linked thermosensitive hydrogel provided by the present invention may further have the following characteristics: after the zirconium ion cross-linked thermosensitive hydrogel TDN-Zr is soaked in water in a high-temperature environment, it strongly adheres to the surface of the substrate at room temperature, can be debonded from the surface of the substrate after soaking in water at room temperature, and strongly adheres to the substrate again at room temperature after soaking in water in a high-temperature environment, and the environmentally responsive cycle reversibly repeats the above-mentioned strong adhesion and debonding processes.

[0020] Preferably, in the above <method> and <gel>, the room temperature refers to 10 °C to 32 °C, more preferably 25 to 30 °C, and the high temperature refers to 70 °C to 90 °C.

[0021] As Figure 1 and 2 shown, the environmentally responsive adhesive zirconium ion cross-linked thermosensitive hydrogel TDN-Zr prepared by the present invention is obtained by soaking the PNaAMPS / P(NIPAm-co-AAm) double-network thermosensitive hydrogel TDN in a zirconium ion solution. Among them, the NIPAm unit contains a hydrophilic amide group and a hydrophobic isopropyl group, and with the change of the environmental temperature between room temperature and high temperature, the internal molecules of the hydrogel will undergo hydrophilic association and hydrophobic phase separation transformation. Among them, zirconium ions with high ionization energy react with the sulfonate group -SO3 on PNaAMPS -The groups, namely the amide group -CONH2 and imide group -CONH- on P(NIPAm-co-AAm), have strong coordination synergy to form a special bonding network. With the change of environmental temperature between room temperature and high temperature, the coordination of zirconium ions will enhance hydrophilicity and cause hydrophobic phase separation and fixation. When adhesion is required, the hydrogel TDN-Zr is treated by soaking in water at high temperature. The zirconium ions crosslink the thermosensitive hydrogel TDN-Zr, and the hydrophobic phase separation arrangement occurs. The number of hydrophobic association domains on the hydrogel surface increases, resulting in an increase in the hydrophobic interaction binding sites on the hydrogel surface and being fixed by zirconium ions. The self-hydrophobic effect is significantly enhanced, which helps to destroy the hydration layer on the hydrogel surface and is conducive to the formation of strong interactions between interfaces. After taking out the hydrogel and attaching it to the surface of a substrate (such as glass) at room temperature, the hydrogel can closely adhere to the substrate surface. On the one hand, chemical interactions such as hydrogen bonds and ionic bonds are formed between the hydrogel surface and the substrate surface. On the other hand, the surface hardening layer of the hydrogel adhering to the substrate and the adhered substrate both protect the loss of moisture inside the gel, while the moisture in the hydrophobic association domain on the gel surface in contact with air quickly volatilizes, and the hydrogel surface hardens, fitting and fixing the relatively rough part of the substrate surface (there are some convex and concave regions on the substrate surface at the microscale), forming a physical topological interlock between the adhesion interface with the substrate, so that the hydrogel TDN-Zr can be locked on the substrate surface. The chemical interaction and the physical interface topological interlock cooperate together, greatly improving the adhesion performance of the hydrogel TDN-Zr and forming effective strong adhesion. When debonding is required, soak it in water at room temperature. Due to the hydration of zirconium ions and the existence of hydrophilic association domains inside the hydrogel, the hydrogel TDN-Zr quickly absorbs water and swells, and the arrangement of hydrophobic and hydrophilic association domains changes again. The number of hydrophobic association domains on the surface of the hydrogel TDN-Zr rapidly decreases, the hydrophobic interaction binding sites decrease, and the soft water film lubricating layer on the surface is re-formed, enabling the hydrogel to quickly debond from the substrate surface. When adhesion is required again, soak the hydrogel TDN-Zr in water at high temperature again, and its surface shows hydrophobic characteristics again. The hydrophobic and hydrophilic association domains are rearranged again, and the hydrophobic binding sites on the surface increase again. Fix it on the substrate surface at room temperature again, and strong interactions are formed again between the surface of the hydrogel TDN-Zr and the substrate, forming a stable interface topological interlock, thus realizing a reversible process of secondary strong adhesion with temperature increase for fixation. And the aforementioned strong adhesion and debonding processes can be carried out reversibly in multiple cycles, and the reversible strong adhesion performance is stable and controllable.

[0022] The environmentally responsive adhesive zirconium ion crosslinked thermosensitive hydrogel prepared by the present invention has a simple and easy-to-control preparation process. The prepared hydrogel has a uniform structure and stable performance. The zirconium ions and the sulfonate group -SO3 on PNaAMPS -The special bonding network formed by the strong coordination and synergistic action of the groups, the amide group -CONH2 and the imide group -CONH- on P(NIPAm-co-AAm) can promote the formation of chemical interactions and physical topological interlocks between the hydrogel surface and the substrate surface when adhesion is required, thus greatly improving the adhesion performance between the hydrogel and the substrate to achieve strong adhesion. When de-adhesion is required, the hydrophilic association domains present inside the hydrogel achieve de-adhesion through water absorption at room temperature, and the aforementioned adhesion and de-adhesion processes can be repeatedly carried out according to environmental changes as a controllable cyclic reversible process, which will become a general method for preparing environmentally responsive adhesive composites from metal ion cross-linked thermosensitive hydrogels.

[0023] Compared with the prior art, the present invention has the following advantages and remarkable progress:

[0024] 1) The preparation process of the present invention is simple, with a short production cycle, simple process conditions, easily available raw materials, and low production costs.

[0025] 2) The special bonding network formed by the zirconium ion cross-linking method adopted in the present invention significantly improves the adhesion performance of the hydrogel, forms strong adhesion with the substrate, and can realize the cyclic reversible process of strong adhesion and de-adhesion by changing environmental conditions, having broad application prospects in the field of environmentally responsive adhesive materials. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 It is a schematic diagram of the principle for the preparation of the environmentally responsive adhesive zirconium ion cross-linked thermosensitive hydrogel TDN-Zr involved in the present invention; among them, the tadpole-like structure is divided into two parts, the first half (including the head and half of the wavy tail) is light-colored representing hydrophilic groups, and the second half is dark-colored representing isopropyl hydrophobic groups;

[0027] Figure 2 It is a schematic diagram of the change in the network structure of TDN-Zr involved in the present invention before and after soaking in water at high temperature. DETAILED DESCRIPTION OF THE INVENTION

[0028] The following will describe in detail the specific implementation embodiments of the present invention with reference to the accompanying drawings.

[0029] Example 1

[0030] Step 1: Weigh 0.30 g of PNaAMPS, 3.9606 g of NIPAm (3.5 mol L -1 ), 0.3554 g of AAm (0.5 mol L -1)、0.0154 g of MBAA (0.1 mol%), 0.0015 g of KA (0.01 mol%) and 10 mL of deionized water were stirred and dissolved under light-shielded conditions to obtain a homogeneous mixed solution; ultraviolet light was used for photopolymerization for 8 h to obtain the PNaAMPS / P(NIPAm-co-AAm) double-network thermosensitive hydrogel TDN, which was soaked in deionized water for 48 h to balance and remove unreacted monomers;

[0031] Step 2: Prepare a 0.1 mol / L -1 zirconium ion solution. The double-network thermosensitive hydrogel TDN with balanced water soaking obtained in Step 1 was immersed in the 0.1 mol / L -1 zirconium ion solution for 24 h, and then immersed in deionized water at 90 °C for 48 h to reach swelling equilibrium to obtain the zirconium ion-crosslinked thermosensitive hydrogel TDN-Zr with environmentally responsive adhesion.

[0032] Example 2

[0033] Step 1: Weigh 0.30 g of PNaAMPS, 3.9493 g of NIPAm (3.49 mol / L -1 ), 0.3625 g of AAm (0.51 mol / L -1 ), 0.0154 g of MBAA (0.1 mol%), 0.0015 g of KA (0.01 mol%) and 10 mL of deionized water were stirred and dissolved under light-shielded conditions to obtain a homogeneous mixed solution; ultraviolet light was used for photopolymerization for 8 h to obtain the PNaAMPS / P(NIPAm-co-AAm) double-network thermosensitive hydrogel TDN, which was soaked in deionized water for 48 h to balance and remove unreacted monomers;

[0034] Step 2: Prepare a 0.3 mol / L -1 zirconium ion solution. The double-network thermosensitive hydrogel TDN with balanced water soaking obtained in Step 1 was immersed in the 0.3 mol / L -1 zirconium ion solution for 24 h, and then immersed in deionized water at 90 °C for 48 h to reach swelling equilibrium to obtain the zirconium ion-crosslinked thermosensitive hydrogel TDN-Zr with environmentally responsive adhesion.

[0035] Example 3

[0036] Step 1: Weigh 0.30 g of PNaAMPS, 3.9719 g of NIPAm (3.51 mol / L -1 ), 0.3483 g of AAm (0.49 mol / L -1)、0.0154 g of MBAA (0.1 mol%)、0.0015 g of KA (0.01 mol%) and 10 mL of deionized water were stirred and dissolved under light-shielding conditions to obtain a homogeneous mixed solution; ultraviolet light was used for photopolymerization for 8 h to obtain the PNaAMPS / P(NIPAm-co-AAm) double-network thermosensitive hydrogel TDN, which was soaked in deionized water for 48 h to balance the water level and remove unreacted monomers;

[0037] Step 2: Prepare a 0.5 mol / L -1 zirconium ion solution. The double-network thermosensitive hydrogel TDN with balanced water level obtained in Step 1 was immersed in the 0.5 mol / L -1 zirconium ion solution for 24 h, and then immersed in deionized water at 90 °C for 48 h. After swelling to equilibrium, the zirconium ion-crosslinked thermosensitive hydrogel TDN-Zr with environmental-responsive adhesion was obtained.

[0038] Example 4

[0039] Step 1: Weigh 0.30 g of PNaAMPS, 3.9606 g of NIPAm (3.5 mol / L -1 ), 0.3554 g of AAm (0.5 mol / L -1 ), 0.0154 g of MBAA (0.1 mol%), 0.0015 g of KA (0.01 mol%) and 10 mL of deionized water were stirred and dissolved under light-shielding conditions to obtain a homogeneous mixed solution; ultraviolet light was used for photopolymerization for 8 h to obtain the PNaAMPS / P(NIPAm-co-AAm) double-network thermosensitive hydrogel TDN, which was soaked in deionized water for 48 h to balance the water level and remove unreacted monomers;

[0040] Step 2: Prepare a 0.3 mol / L -1 zirconium ion solution. The double-network thermosensitive hydrogel TDN with balanced water level obtained in Step 1 was immersed in the 0.3 mol / L -1 zirconium ion solution for 24 h, and then immersed in deionized water at 70 °C for 48 h. After swelling to equilibrium, the zirconium ion-crosslinked thermosensitive hydrogel TDN-Zr with environmental-responsive adhesion was obtained.

[0041] Example 5

[0042] Step 1: Weigh 0.30 g of PNaAMPS, 3.9832 g of NIPAm (3.52 mol / L -1 ), 0.3412 g of AAm (0.48 mol / L -1)、0.0154 g of MBAA (0.1 mol%), 0.0015 g of KA (0.01 mol%) and 10 mL of deionized water were stirred and dissolved under light-shielded conditions to obtain a homogeneous mixed solution; ultraviolet light was irradiated for 8 h to obtain the PNaAMPS / P(NIPAm-co-AAm) double-network thermosensitive hydrogel TDN, which was soaked in deionized water for 48 h to balance the water level and remove unreacted monomers;

[0043] Step 2: Prepare a 0.3 mol L -1 zirconium ion solution. The double-network thermosensitive hydrogel TDN with balanced water level obtained in step 1) was immersed in the 0.3 mol L -1 zirconium ion solution for 24 h, and then immersed in deionized water at 80 °C for 48 h. After swelling equilibrium, the zirconium ion-crosslinked thermosensitive hydrogel TDN-Zr with environmental-responsive adhesion was obtained.

[0044] Comparative Example 1

[0045] Step 1: Weigh 0.30 g of PNaAMPS, 3.9606 g of NIPAm (3.5 mol L -1 ), 0.3554 g of AAm (0.5 mol L -1 ), 0.0154 g of MBAA (0.1 mol%), 0.0015 g of KA (0.01 mol%) and 10 mL of deionized water were stirred and dissolved under light-shielded conditions to obtain a homogeneous mixed solution; ultraviolet light was irradiated for 8 h to obtain the PNaAMPS / P(NIPAm-co-AAm) double-network thermosensitive hydrogel TDN, which was immersed in deionized water at 90 °C for 48 h, and the thermosensitive hydrogel TDN was obtained after swelling equilibrium.

[0046] Comparative Example 2

[0047] Step 1: Weigh 0.30 g of PNaAMPS, 3.9380 g of NIPAm (3.48 mol L -1 ), 0.3696 g of AAm (0.52 mol L -1 ), 0.0154 g of MBAA (0.1 mol%), 0.0015 g of KA (0.01 mol%) and 10 mL of deionized water were stirred and dissolved under light-shielded conditions to obtain a homogeneous mixed solution; ultraviolet light was irradiated for 8 h to obtain the PNaAMPS / P(NIPAm-co-AAm) double-network thermosensitive hydrogel TDN, which was soaked in deionized water for 48 h to balance the water level and remove unreacted monomers;

[0048] Step 2: Prepare a 0.3 mol L -1 zirconium ion solution. The double-network thermosensitive hydrogel TDN with balanced water level obtained in step 1 was put into 0.3 mol L-1 Immerse it in a zirconium ion solution for 24 h, and then put it into deionized water at 20 °C for 48 h to obtain the zirconium ion-crosslinked thermosensitive hydrogel TDN*Zr by swelling equilibrium.

[0049] Adhesion performance test:

[0050] Step 1: Cut the hydrogel strips soaked in deionized water at different temperatures for 24 h into specimens with a specification of 20 mm in length and 15 mm in width.

[0051] Step 2: After drying the moisture on the surface of the specimens obtained in Step 1, quickly stick them between two smooth glass slides treated by an ultraviolet ozone cleaner at room temperature, and apply a constant pressure of 16.67 kPa to the adhesion area with a 500 g weight for 10 min.

[0052] Step 3: Clamp both ends of the two glass slides with a universal testing machine, and perform a lap shear test on the adhesion sample between the hydrogel and the glass at a rate of 50 mm / min -1 until the hydrogel debonds to obtain a force-displacement curve.

[0053] Step 4: Immerse the debonded hydrogel in Step 3 in deionized water at the same temperature for 24 h again. After drying the surface moisture, quickly stick it between two smooth glass slides treated by an ultraviolet ozone cleaner at room temperature, and apply a constant pressure of 16.67 kPa to the adhesion area with a 500 g weight for 10 min.

[0054] Step 5: Clamp both ends of the two glass slides with a universal testing machine, and perform a lap shear test on the adhesion sample between the hydrogel and the glass at a rate of 50 mm / min -1 until the hydrogel debonds for the second time to obtain the second force-displacement curve.

[0055] Step 6: Calculate the adhesion strength L of the sample by the ratio of the maximum force during the shear process to the contact area between the sample and the glass substrate. The calculation formula is as follows:

[0056]

[0057] In the formula, F is the maximum shear force during the tensile process, with the unit of N; l is the overlapping length of the hydrogel sample and the glass substrate, with the unit of mm; b is the overlapping width of the hydrogel sample and the glass substrate, with the unit of mm.

[0058] The adhesion strengths of the zirconium ion-crosslinked thermosensitive hydrogels obtained in the above examples and comparative examples are shown in Table 1 below:

[0059] Table 1: Adhesion strength of zirconium ion-crosslinked thermosensitive hydrogel

[0060]

[0061] Examples 1 to 3 are zirconium ion cross-linked thermosensitive hydrogels prepared by changing the concentration of zirconium ion solution at an environmental temperature of 90 °C. Examples 4 and 5 are zirconium ion cross-linked thermosensitive hydrogels TDN-Zr prepared at environmental temperatures of 70 °C and 80 °C respectively with a zirconium ion solution concentration of 0.3 mol L -1 For the preparation. Comparative Example 1 is a thermosensitive hydrogel TDN prepared without zirconium ion cross-linking at an environmental temperature of 90 °C. Comparative Example 2 is a zirconium ion cross-linked thermosensitive hydrogel TDN*Zr prepared at an environmental temperature of 20 °C with a zirconium ion solution concentration of 0.3 mol L -1 For the preparation.

[0062] According to the data in Table 1:

[0063] As can be seen from Examples 1 to 3, with the increase in the concentration of zirconium ion solution, the adhesion strength of thermosensitive hydrogels TDN-Zr crosslinked with zirconium ions at different concentrations first increases and then decreases at 90°C. In Examples 2, 4, and 5, under the condition of changing the environmental temperature, the adhesion strength increases with the increase in temperature. In Comparative Example 1, there is no zirconium ion crosslinking. Compared with Examples 1 to 3, in Examples 1 to 3, there is a strong ionic coordination crosslinking between zirconium ions and the sulfonic acid groups of the first PNaAMPS network and the amide and imide groups of the second P(NIPAm-co-AAm) network in the thermosensitive hydrogel. At high temperature, the volume of the hydrophobic association domain centered on zirconium ions decreases, and the hydrophobic and hydrophilic association domains are rearranged uniformly. The number of tiny hydrophobic association domains distributed on the gel surface will gradually increase, resulting in an increase in the hydrophobic interaction binding sites on the hydrogel surface. At room temperature, when adhering to the glass substrate surface, the hydrophobic association domains centered on zirconium ions are uniformly arranged on the hydrogel surface. While the hydrogel surface rapidly loses water and hardens, the interior of the hydrogel remains hydrophilic, which helps to form hydrogen bonds, ionic bonds and other interactions with the negatively charged glass substrate, and form a macroscopic topological interlock with the substrate surface. Therefore, zirconium ion crosslinking significantly improves the adhesion strength of the thermosensitive hydrogel. In Comparative Example 2, after soaking in the zirconium ion solution, the swelling equilibrium in water at 20°C is carried out, and the adhesion performance of the obtained TDN*Zr is extremely poor. While in Examples 1 to 5, after soaking in the zirconium ion solution, the swelling equilibrium in water is carried out at high temperatures (70°C, 80°C, and 90°C), indicating that only after the swelling equilibrium in a high-temperature environment, the self-hydrophobic effect on the hydrogel surface can be sharply enhanced, thereby greatly improving the adhesion performance between the zirconium ion crosslinked thermosensitive hydrogel TDN-Zr and the glass substrate at room temperature. The hydrogel surface not only forms chemical interactions such as hydrogen bonds and ionic bonds with the substrate surface, but also the hydrogel surface rapidly loses water and hardens, forming a physical topological interlock with the substrate surface. After the zirconium ion crosslinked thermosensitive hydrogels in Examples 1 to 5 are de-adhered in water at room temperature, by soaking again in a high-temperature environment, secondary adhesion with the substrate can be achieved at room temperature and the adhesion strength is basically the same. And the aforementioned strong adhesion and de-adhesion can be carried out repeatedly for many times, and TDN-Zr shows excellent environmentally responsive reversible strong adhesion performance.

[0064] The above examples are only illustrative of the technical solutions of the present invention. The zirconium ion crosslinked thermosensitive hydrogel with environmentally responsive adhesion and its preparation method involved in the present invention are not limited only to the content described in the above examples, but are subject to the scope defined by the claims. Any modification, supplement or equivalent replacement made by those skilled in the art to the present invention on the basis of this example is within the scope protected by the claims of the present invention.

Claims

1. Preparation method of zirconium ion-crosslinked thermosensitive hydrogel with environment-responsive adhesion, characterized in that Including: Step 1: Sodium poly(2-acrylamido-2-methylpropanesulfonate) PNaAMPS, N-isopropylacrylamide NIPAm, acrylamide AAm, crosslinker, initiator and deionized water are stirred and dissolved under light-shielding conditions to obtain a homogeneous mixed solution, and after ultraviolet polymerization, PNaAMPS / P(NIPAM- co -AAm) double-network thermosensitive hydrogel TDN is obtained; Step 2: Put the double-network thermosensitive hydrogel TDN obtained in Step 1 into a zirconium ion solution, and then into a high-temperature deionized water solution. After swelling equilibrium, a zirconium ion-crosslinked thermosensitive hydrogel TDN-Zr with environmentally responsive adhesion is obtained. Among them, in Step 1, PNaAMPS is obtained by dissolving 2-acrylamido-2-methylpropanesulfonic acid AMPS, sodium hydroxide NaOH, a crosslinking agent, and an initiator in deionized water, stirring in the dark to obtain a uniform mixed solution, pouring it into a parallel-plate glass mold, and subjecting it to ultraviolet light polymerization to obtain a poly(2-acrylamido-2-methylpropanesulfonic acid sodium) PNaAMPS hydrogel. After drying to constant weight in a vacuum drying oven, it is ground with a high-speed ball mill and sieved to obtain PNaAMPS microgel powder with a particle size of 10-200 μm. The concentration of AMPS is 3.98 - 4.02 mol / L -1 ; the concentration of the NaOH solution is 1 mol / L -1 ; the crosslinking agent is N,N'-methylenebisacrylamide (MBAA), and the percentage of MBAA in the total molar amount of monomers is 0.4%; the photoinitiator is 2-ketoglutaric acid (KA), and the percentage of KA in the total molar amount of monomers is 0.1%; In Step 1, the dosage of PNaAMPS is 0.3 g. In the mixed solution of Step 1, the concentration of NIPAm is 3.48 - 3.52 mol / L -1 , the concentration of AAm is 0.48 - 0.52 mol / L -1 , the crosslinking agent is N,N'-methylenebisacrylamide MBAA, accounting for 0.1% of the total molar amount of monomers; the photoinitiator is 2-ketoglutaric acid KA, accounting for 0.01% of the total molar amount of monomers; In step 2, the concentration of the zirconium ion solution is 0.1 - 0.5 mol / L -1 , the soaking time in the zirconium ion solution is 24 h, and the soaking time in high-temperature deionized water is 48 h. The high temperature refers to 70°C - 90°C.

2. The preparation method of zirconium ion-crosslinked thermosensitive hydrogel with environment-responsive adhesion according to claim 1, characterized in that: Wherein, In Step 1, the temperature during stirring is room temperature, and the stirring time is 30-40 min.

3. The preparation method of zirconium ion-crosslinked thermosensitive hydrogel with environment-responsive adhesion according to claim 1, characterized in that: Wherein, In Step 1, the conditions for illumination under ultraviolet light are: illuminating for 8-10 h under an ultraviolet lamp with a wavelength of 365 nm and a power of 15 W.

4. The preparation method of zirconium ion-crosslinked thermosensitive hydrogel with environment-responsive adhesion according to claim 2, characterized in that: Wherein, Room temperature refers to 10°C to 32°C.

5. Zirconium ion-crosslinked thermosensitive hydrogel with environment-responsive adhesion, characterized in that: Prepared by the preparation method of the zirconium ion-crosslinked thermosensitive hydrogel with environmentally responsive adhesion described in any one of Claims 1 to 4.

6. The zirconium ion-crosslinked thermosensitive hydrogel with environment-responsive adhesion according to claim 5, characterized in that: Wherein, The zirconium ion-crosslinked thermosensitive hydrogel TDN-Zr after soaking in water at a high temperature strongly adheres to the substrate surface at room temperature, can be detached from the substrate surface after soaking in water at room temperature, and strongly adheres to the substrate again at room temperature after soaking in water at a high temperature. The environmentally responsive cycle reversibly repeats the aforementioned strong adhesion and detachment processes.

7. The zirconium ion-crosslinked thermosensitive hydrogel with environment-responsive adhesion according to claim 6, characterized in that: Wherein, Room temperature refers to 10°C to 32°C.

Images