Cellulose graft polymer hydrogel with multiple stimulation responsiveness and preparation method thereof
By preparing cellulose-grafted polymer hydrogels, a synergistic response to triple stimulation of temperature, pH, and ultraviolet light was achieved, solving the problem of synergistic response to multiple signals in existing technologies, broadening the application range of hydrogels and improving their environmental friendliness.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2026-01-14
- Publication Date
- 2026-04-07
AI Technical Summary
Existing technologies struggle to achieve hydrogels that respond synergistically to multiple signals, especially to temperature, pH, and UV light stimulation.
A cellulose graft polymer hydrogel with triple responses to temperature, pH and ultraviolet light was prepared by initiating polymerization of hydroxypropyl methylcellulose acetoacetate (HPMCAA), 7-acrylamido-4-methylcoumarin (AAMC), acrylamide (Am) and N,N'-methylenebisacrylamide (MBA) in an initiation system.
A hydrogel with a synergistic response to triple stimulation of temperature, pH and ultraviolet light was successfully prepared, which broadened the application range of hydrogels and overcame the shortcomings of traditional hydrogel materials such as being difficult to degrade and environmentally unfriendly.
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Abstract
Description
Technical Field
[0001] This invention relates to a cellulose grafted polymer hydrogel with multiple stimuli responsiveness and its preparation method, belonging to the technical field of modified polysaccharide grafted polymer hydrogels. Background Technology
[0002] Data encryption and protection are of great significance in military and economic fields, and stimulus-responsive hydrogels are among the most promising materials for information storage and encryption. Stimulus-responsive hydrogels can undergo physicochemical property changes in response to changes in external stimuli (such as pH, temperature, light, magnetic fields, pressure, ions, etc.). To meet complex functional requirements and diverse application scenarios, these responsive materials are developing towards smart materials that can respond to multiple stimuli. Multi-responsive hydrogels, which can respond to two or more environmental stimuli, are a typical example of this advanced smart material.
[0003] Among numerous stimulus-response mechanisms, photoresponse has broad application prospects due to its simplicity and ease of control. Taking photochromism as an example, hydrogels change color under specific light irradiation. In recent years, photoinstantaneous covalent bonds (such as disulfide bonds with dynamic exchange reactions, trithiocarbonates undergoing rearrangement reactions, and anthracene participating in reversible cycloaddition reactions) have attracted widespread attention. Among these photoinstantaneous groups, coumarins and their derivatives have become research hotspots due to their photoluminescent properties, efficient dimerization and cleavage reactions (without photosensitizers or catalysts), excellent bioactivity, and biocompatibility.
[0004] Specifically, coumarin undergoes a dimerization reaction under 365nm light irradiation, forming a four-membered ring structure through [2+2] cycloaddition; this four-membered ring structure breaks down under 254nm light irradiation, reverting to the original coumarin structure. Based on this property, introducing coumarin units into the gel matrix can theoretically achieve spatial control of the gel network structure by reversibly forming additional cross-linking points. Temperature response is an essential activity in our daily lives. Currently, researchers have conducted extensive studies on hydrogels with temperature sensing functions. Some thermosensitive hydrogels exhibit temperature-responsive changes in transparency or color, which can be directly observed with the naked eye. Using these properties, it is possible to determine whether the ambient temperature is higher or lower than the phase transition temperature (i.e., thermochromic temperature) of the hydrogel.
[0005] Hydroxypropyl methylcellulose (HPMC) is a cellulose ether obtained by reacting cellulose with chloromethane and epichlorohydrin, resulting in the partial methylation and hydroxypropylation of hydroxyl groups. It has wide applications in this field. It is a white or pale yellow, odorless and tasteless powdery solid with hygroscopic and swelling properties. Due to the presence of hydrophobic methoxy groups in its molecular structure, HPMC exhibits temperature responsiveness and thermotropic gelation characteristics. Furthermore, its molecular chain contains a large number of active hydroxyl groups, making it easy to undergo etherification, esterification modification, and graft copolymerization. This invention proposes a multi-responsive hydrogel prepared by esterifying HPMC with ethyl acetoacetate and then crosslinking it with fluorescent monomers and acrylamide, achieving a synergistic response to temperature, pH, and ultraviolet light signals, which has developmental value. Summary of the Invention
[0006] To address the shortcomings of existing technologies, especially the challenge of synergistic response to multiple signals, this invention provides a cellulose grafted polymer hydrogel with multiple stimulus responses and its preparation method. The hydrogel of this invention exhibits triple responses to temperature, pH, and ultraviolet light.
[0007] The specific technical solution adopted in this invention is as follows:
[0008] A cellulose graft polymer hydrogel with multiple stimuli responsiveness is obtained by initiating polymerization of hydroxypropyl methylcellulose acetoacetate (HPMCAA), 7-acrylamido-4-methylcoumarin (AAMC), acrylamide (Am), and N,N'-methylenebisacrylamide (MBA) in an initiation system.
[0009] According to a preferred embodiment of the present invention, the mass ratio of hydroxypropyl methylcellulose acetoacetate (HPMCAA), 7-acrylamido-4-methylcoumarin (AAMC), N,N'-methylenebisacrylamide (MBA) to acrylamide (Am) is (1~10):(0.1~2):(0.1~1):100.
[0010] According to a preferred embodiment of the present invention, the initiator used in the initiation system is potassium persulfate, and the mass ratio of the initiator to acrylamide is (0.2~5):100, more preferably (1~2):100.
[0011] According to a preferred embodiment of the present invention, the hydroxypropyl methylcellulose acetoacetate (HPMCAA) is prepared by the following method:
[0012] (1) Esterification: Hydroxypropyl methylcellulose was dried thoroughly in an oven, then dissolved in N-N'-dimethylformamide by stirring, and then tert-butyl acetoacetate was added to carry out the reaction.
[0013] (2) Purification: After the reaction is completed, the reaction solution is added to anhydrous ethanol to precipitate, and then filtered, washed and dried to obtain hydroxypropyl methylcellulose acetoacetate (HPMCAA).
[0014] According to a preferred embodiment of the present invention, in step (1), the degree of substitution of the hydroxypropyl methylcellulose (HPMC) is methoxy: 28-30%; hydroxypropyl: 7.0-12%.
[0015] According to a preferred embodiment of the present invention, in step (1), the viscosity of the 2wt% aqueous solution of hydroxypropyl methylcellulose is 3~100 mPa·s.
[0016] According to a preferred embodiment of the present invention, in step (1), the drying temperature of hydroxypropyl methylcellulose is 60~100℃ and the drying time is 1~5h.
[0017] According to a preferred embodiment of the present invention, in step (1), the mass ratio of the hydroxypropyl methylcellulose to the volume ratio of N-N'-dimethylformamide is 1 g: (3~7) mL.
[0018] According to a preferred embodiment of the present invention, in step (1), the temperature of stirring and dissolving is 60~120℃, and the stirring and dissolving time is 1~2h.
[0019] According to a preferred embodiment of the present invention, in step (1), the mass ratio of the hydroxypropyl methylcellulose to the volume ratio of tert-butyl acetoacetate is 1 g: (0.5-3) mL.
[0020] According to a preferred embodiment of the present invention, in step (1), the reaction temperature is 80~120℃ and the reaction time is 3~7h.
[0021] According to a preferred embodiment of the present invention, in step (2), the volume ratio of the reaction solution to the anhydrous ethanol used for precipitation is 1:10~20.
[0022] According to a preferred embodiment of the present invention, in step (2), the washing is performed by stirring and washing with anhydrous ethanol 3-6 times, the drying temperature is 40-80℃, and the drying time is 6-12h.
[0023] According to a preferred embodiment of the present invention, the specific preparation method of the fluorescent monomer 7-acrylamido-4-methylcoumarin (AAMC) is as follows:
[0024] 1) Acylation: 7-amino-4-methylcoumarin was added to tetrahydrofuran (THF), stirred and dispersed thoroughly, and then acryloyl chloride and triethylamine were added to carry out the reaction;
[0025] 2) Purification: After the reaction is completed, THF is removed by rotary evaporation. The product is washed, filtered and dried in anhydrous ethanol to obtain 7-acrylamido-4-methylcoumarin (AAMC).
[0026] According to a preferred embodiment of the present invention, in step 1), the molar ratio of 7-amino-4-methylcoumarin, acryloyl chloride, and triethylamine is 1:(1.1-1.5):(1.1-1.5).
[0027] According to a preferred embodiment of the present invention, in step 1), the molar amount of 7-amino-4-methylcoumarin to the volume ratio of tetrahydrofuran is 4-10 mmol: 40-100 mL.
[0028] According to a preferred embodiment of the present invention, in step 1), the reaction temperature is -5 to 5°C and the reaction time is 6 to 24 hours.
[0029] According to a preferred embodiment of the present invention, in step 2), the washing is performed by stirring and washing with anhydrous ethanol 3-6 times, the drying temperature is 40-80℃, and the drying time is 6-12h.
[0030] The preparation method of the above-mentioned cellulose grafted polymer hydrogel with multiple stimulus responsiveness includes the following steps:
[0031] Acrylamide (Aam), hydroxypropyl methylcellulose acetoacetate (HPMCAA), 7-acrylamido-4-methylcoumarin (AAMC), and N,N'-methylenebisacrylamide (MBA) were added to deionized water and ultrasonically dispersed to obtain a homogeneous solution. An initiator was then added, and polymerization was initiated by heating to obtain a multi-stimulus responsive cellulose graft polymer hydrogel.
[0032] According to a preferred embodiment of the present invention, the mass ratio of acrylamide to deionized water is 1 g: (3~10) mL.
[0033] According to a preferred embodiment of the present invention, the mass ratio of hydroxypropyl methylcellulose acetoacetate (HPMCAA) to acrylamide is (0.01-0.1):1.
[0034] According to a preferred embodiment of the present invention, the mass ratio of 7-acrylamido-4-methylcoumarin (AAMC) to acrylamide is (0.001-0.02):1.
[0035] According to a preferred embodiment of the present invention, the mass ratio of N,N'-methylenebisacrylamide (MBA) to acrylamide is (0.001-0.01):1.
[0036] According to a preferred embodiment of the present invention, the polymerization reaction temperature is 60~80°C, and the polymerization reaction time is 2~6h, more preferably 4h.
[0037] The technical features and advantages of this invention are as follows:
[0038] 1. In the multi-responsive hydrogel of this invention, hydroxypropyl methylcellulose acetoacetate (HPMCAA) serves as a physical cross-linking network, forming intramolecular and intermolecular hydrogen bonds that enhance the hydrogel's strength and cohesion. Furthermore, in addition to direct polymerization with monomers, the initiated free radicals can steal hydrogen from cellulose, thereby generating cellulose macromolecular free radicals that graft polymerize with monomers. Through the dual effects of physical and chemical cross-linking, cellulose endows the hydrogel with a dense network.
[0039] 2. The multi-responsive hydrogel of this invention introduces the temperature-sensitive compound HPMCAA and the fluorescence-responsive coumarin unit. At the same time, the fluorescence performance of the coumarin unit can be controlled by pH and ultraviolet light, which solves the shortcomings of the multi-stimulus response of fluorescent responsive materials. A hydrogel with synergistic response to temperature, pH and ultraviolet light triple stimulation is successfully prepared, which broadens the application range of hydrogels.
[0040] 3. The manufacturing process of this invention is simple to operate and highly practical. It introduces biocompatible and biodegradable cellulose, and the prepared hydrogel not only has stimuli responsiveness, but also overcomes the shortcomings of traditional hydrogel raw materials that are difficult to degrade and environmentally unfriendly. Attached Figure Description
[0041] Figure 1 The infrared spectra of hydroxypropyl methylcellulose acetoacetate (HPMCAA) prepared in Example 1 and raw material hydroxypropyl methylcellulose (HPMC) are shown.
[0042] Figure 2 The hydroxypropyl methylcellulose acetoacetate (HPMCAA) prepared in Example 1 and the raw material hydroxypropyl methylcellulose (HPMC) 1 H NMR spectrum.
[0043] Figure 3 Fluorescence image of the multi-responsive hydrogel based on hydroxypropyl methylcellulose acetoacetate prepared in Example 5 under 365 nm ultraviolet light.
[0044] Figure 4 The effect of changes in HPMCAA concentration on phase transition temperature during the preparation process of Examples 1-4.
[0045] Figure 5 The effect of changes in the concentration of 7-acrylamido-4-methylcoumarin (AAMC) on fluorescence intensity during the preparation process of Examples 5-7.
[0046] Figure 6 The effect of pH changes on fluorescence intensity. Detailed Implementation
[0047] The following preferred embodiments are further illustrations of the present invention, but should not be considered as limitations on the present invention. Various changes made based on the present invention without departing from its spirit should also fall within the protection scope of the present invention.
[0048] A 2% aqueous solution of hydroxypropyl methylcellulose acetoacetate (HPMCAA) has a viscosity of 15 mPa·s and is available from Shanghai Maclean Biochemical Technology Co., Ltd.
[0049] 7-Amino-4-methylcoumarin is available from Shanghai Maclean Biochemical Technology Co., Ltd.
[0050] tert-butyl acetoacetate is available from Bailingwei Technology Co., Ltd.
[0051] Existing equipment includes a UV-Vis spectrophotometer and a high-sensitivity integrated fluorescence spectrophotometer (FM-4).
[0052] Example 1
[0053] The preparation method of cellulose grafted polymer hydrogel with multiple stimulus responsiveness includes the following steps:
[0054] (1) Preparation of hydroxypropyl methylcellulose acetoacetate (HPMCAA)
[0055] Hydroxypropyl methylcellulose (HPMC) was dried in a forced-air drying oven at 85°C for 2 hours. 10 g of the dried product was added to a 250 mL round-bottom flask, followed by 40 mL of N-N'-dimethylformamide. The mixture was heated to 85°C and stirred to dissolve for 1 hour. Then, 5 mL of tert-butyl acetoacetate was added sequentially, and the mixture was heated to 110°C and reacted for 3 hours. After the reaction was complete, the original solution was added dropwise to 600 mL of anhydrous ethanol with rapid stirring. The mixture was then crushed using a crusher and washed three times in anhydrous ethanol at room temperature. The product was dried in a 60°C oven for 12 hours to obtain a pale yellow solid product, hydroxypropyl methylcellulose acetoacetate (HPMCAA), with a yield of 90%.
[0056] The infrared spectrum of the prepared hydroxypropyl methylcellulose acetoacetate (HPMCAA) is shown in the figure. Figure 1 , 1 H NMR spectrum see Figure 2 This demonstrates that the present invention successfully synthesized hydroxypropyl methylcellulose acetoacetate (HPMCAA).
[0057] (2) Preparation of 7-acrylamido-4-methylcoumarin (AAMC)
[0058] 1.044 g (6 mmol) of 7-amino-4-methylcoumarin was weighed and transferred to a 100 mL three-necked flask. 50 mL of tetrahydrofuran and 0.912 g (9 mmol) of triethylamine were added. The mixture was stirred in an ice-water bath for 30 min and then cooled. Subsequently, 0.815 g (9 mmol) of acryloyl chloride was added dropwise. The mixture was stirred vigorously in an ice-water bath for 2 h, and then the reaction was allowed to proceed at room temperature for 10 h. After the reaction was complete, THF was removed by rotary evaporation. The solid product was washed three times with anhydrous ethanol, filtered, and the filter cake was dried in a 60°C oven for 12 h. A off-white solid powder of 7-acrylamido-4-methylcoumarin (AAMC) was obtained, with a yield of 90.15%.
[0059] (3) Preparation of hydrogels
[0060] First, 2g of acrylamide (Am) and 4mg of 7-acrylamido-4-methylcoumarin (AAMC) were added to 10mL of deionized water and ultrasonically dispersed for 20min to obtain a homogeneous solution. Then, 30mg of hydroxypropyl methylcellulose acetoacetate (HPMCAA) was added to the solution and stirred to dissolve, resulting in a uniformly dispersed solution. Next, 20mg of initiator KPS (1wt%Am) and 2mg of crosslinking agent MBA (0.1wt%Am) were added to the solution and stirred to dissolve. The solution was then transferred to a polytetrafluoroethylene mold. Finally, the mold was placed in a 70°C constant temperature incubator for thermally initiated polymerization for 12h. After the reaction, the mixture was cooled to room temperature to obtain a hydrogel sample. The mass ratio of acrylamide (Aam), N,N'-methylenebisacrylamide (MBA), hydroxypropyl methylcellulose acetoacetate (HPMCAA), 7-acrylamido-4-methylcoumarin (AAMC), and potassium persulfate (KPS) was 100:0.1:1.5:0.2:1.
[0061] Example 2
[0062] The preparation method of cellulose grafted polymer hydrogel with multiple stimulus responsiveness includes the following steps:
[0063] (1) The preparation of hydroxypropyl methylcellulose acetoacetate (HPMCAA) is the same as in Example 1;
[0064] (2) The preparation of 7-acrylamido-4-methylcoumarin (AAMC) was the same as in Example 1;
[0065] (3) Preparation of hydrogels
[0066] First, 2g of acrylamide (Am) and 4mg of 7-acrylamido-4-methylcoumarin (AAMC) were added to 10mL of deionized water and ultrasonically dispersed for 20min to obtain a homogeneous solution. Then, 60mg of hydroxypropyl methylcellulose acetoacetate (HPMCAA) was added to the solution and stirred to dissolve, resulting in a uniformly dispersed solution. Next, 20mg of KPS (1wt%Am) as an initiator and 2mg of MBA (0.1wt%Am) as a crosslinking agent were added to the solution and stirred to dissolve. The solution was then transferred to a polytetrafluoroethylene mold. Finally, the mold was placed in a 70°C constant temperature incubator for thermally initiated polymerization for 12h. After the reaction, the mixture was cooled to room temperature to obtain a hydrogel sample. The mass ratio of acrylamide (Aam), N,N'-methylenebisacrylamide (MBA), hydroxypropyl methylcellulose acetoacetate (HPMCAA), 7-acrylamido-4-methylcoumarin (AAMC), and potassium persulfate (KPS) was 100:0.1:3:0.2:1.
[0067] Example 3
[0068] The preparation method of cellulose grafted polymer hydrogel with multiple stimulus responsiveness includes the following steps:
[0069] (1) The preparation of hydroxypropyl methylcellulose acetoacetate (HPMCAA) is the same as in Example 1;
[0070] (2) The preparation of 7-acrylamido-4-methylcoumarin (AAMC) was the same as in Example 1;
[0071] (3) Preparation of hydrogels
[0072] First, 2g of acrylamide (Am) and 4mg of 7-acrylamido-4-methylcoumarin (AAMC) were added to 10mL of deionized water and ultrasonically dispersed for 20 min to obtain a homogeneous solution. Then, 90mg of hydroxypropyl methylcellulose acetoacetate (HPMCAA) was added to the solution and stirred to dissolve, resulting in a uniformly dispersed solution. Next, 20mg of KPS (1wt%Am) as an initiator and 2mg of MBA (0.1wt%Am) as a crosslinking agent were added to the solution and stirred to dissolve. The solution was then transferred to a polytetrafluoroethylene mold. Finally, the mold was placed in a 70°C constant temperature incubator for thermally initiated polymerization for 12h. After the reaction, the mixture was cooled to room temperature to obtain a hydrogel sample. The mass ratio of acrylamide (Aam), N,N'-methylenebisacrylamide (MBA), hydroxypropyl methylcellulose acetoacetate (HPMCAA), 7-acrylamido-4-methylcoumarin (AAMC), and potassium persulfate (KPS) was 100:0.1:4.5:0.2:1.
[0073] Example 4
[0074] The preparation method of cellulose grafted polymer hydrogel with multiple stimulus responsiveness includes the following steps:
[0075] (1) The preparation of hydroxypropyl methylcellulose acetoacetate (HPMCAA) is the same as in Example 1;
[0076] (2) The preparation of 7-acrylamido-4-methylcoumarin (AAMC) was the same as in Example 1;
[0077] (3) Preparation of hydrogels
[0078] First, 2g of acrylamide (Am) and 4mg of 7-acrylamido-4-methylcoumarin (AAMC) were added to 10mL of deionized water and ultrasonically dispersed for 20min to obtain a homogeneous solution. Then, 120mg of hydroxypropyl methylcellulose acetoacetate (HPMCAA) was added to the solution and stirred to dissolve, resulting in a uniformly dispersed solution. Next, 20mg of KPS (1wt%Am) as an initiator and 2mg of MBA (0.1wt%Am) as a crosslinking agent were added to the solution and stirred to dissolve. The solution was then transferred to a polytetrafluoroethylene mold. Finally, the mold was placed in a 70°C constant temperature incubator for thermally initiated polymerization for 12h. After the reaction, the mixture was cooled to room temperature to obtain a hydrogel sample. The mass ratio of acrylamide (Aam), N,N'-methylenebisacrylamide (MBA), hydroxypropyl methylcellulose acetoacetate (HPMCAA), 7-acrylamido-4-methylcoumarin (AAMC), and potassium persulfate (KPS) was 100:0.1:6:0.2:1.
[0079] Example 5
[0080] The preparation method of cellulose grafted polymer hydrogel with multiple stimulus responsiveness includes the following steps:
[0081] (1) The preparation of hydroxypropyl methylcellulose acetoacetate (HPMCAA) is the same as in Example 1;
[0082] (2) The preparation of 7-acrylamido-4-methylcoumarin (AAMC) was the same as in Example 1;
[0083] (3) Preparation of hydrogels
[0084] First, 2g of acrylamide (Am) and 2mg of 7-acrylamido-4-methylcoumarin (AAMC) were added to 10mL of deionized water and ultrasonically dispersed for 20min to obtain a homogeneous solution. Then, 60mg of hydroxypropyl methylcellulose acetoacetate (HPMCAA) was added to the solution and stirred to dissolve, resulting in a uniformly dispersed solution. Next, 20mg of initiator KPS (1wt%Am) and 2mg of crosslinking agent MBA (0.1wt%Am) were added to the solution and stirred to dissolve. The solution was then transferred to a polytetrafluoroethylene mold. Finally, the mold was placed in a 70°C constant temperature incubator for thermally initiated polymerization for 12h. After the reaction, the mixture was cooled to room temperature to obtain a hydrogel sample. The mass ratio of acrylamide (Aam), N,N'-methylenebisacrylamide (MBA), hydroxypropyl methylcellulose acetoacetate (HPMCAA), 7-acrylamido-4-methylcoumarin (AAMC), and potassium persulfate (KPS) was 100:0.1:3:0.1:1.
[0085] Example 6
[0086] The preparation method of cellulose grafted polymer hydrogel with multiple stimulus responsiveness includes the following steps:
[0087] (1) The preparation of hydroxypropyl methylcellulose acetoacetate (HPMCAA) is the same as in Example 1;
[0088] (2) The preparation of 7-acrylamido-4-methylcoumarin (AAMC) was the same as in Example 1;
[0089] (3) Preparation of hydrogels
[0090] First, 2g of acrylamide (Am) and 6mg of 7-acrylamido-4-methylcoumarin (AAMC) were added to 10mL of deionized water and ultrasonically dispersed for 20min to obtain a homogeneous solution. Then, 60mg of hydroxypropyl methylcellulose acetoacetate (HPMCAA) was added to the solution and stirred to dissolve, resulting in a uniformly dispersed solution. Next, 20mg of initiator KPS (1wt%Am) and 2mg of crosslinking agent MBA (0.1wt%Am) were added to the solution and stirred to dissolve. The solution was then transferred to a polytetrafluoroethylene mold. Finally, the mold was placed in a 70°C constant temperature incubator for thermally initiated polymerization for 12h. After the reaction, the mixture was cooled to room temperature to obtain a hydrogel sample. The mass ratio of acrylamide (Aam), N,N'-methylenebisacrylamide (MBA), hydroxypropyl methylcellulose acetoacetate (HPMCAA), 7-acrylamido-4-methylcoumarin (AAMC), and potassium persulfate (KPS) was 100:0.1:3:0.3:1.
[0091] Example 7
[0092] The preparation method of cellulose grafted polymer hydrogel with multiple stimulus responsiveness includes the following steps:
[0093] (1) The preparation of hydroxypropyl methylcellulose acetoacetate (HPMCAA) is the same as in Example 1;
[0094] (2) The preparation of 7-acrylamido-4-methylcoumarin (AAMC) was the same as in Example 1;
[0095] (3) Preparation of hydrogels
[0096] First, 2g of acrylamide (Am) and 8mg of 7-acrylamido-4-methylcoumarin (AAMC) were added to 10mL of deionized water and ultrasonically dispersed for 20min to obtain a homogeneous solution. Then, 60mg of hydroxypropyl methylcellulose acetoacetate (HPMCAA) was added to the solution and stirred to dissolve, resulting in a uniformly dispersed solution. Next, 20mg of initiator KPS (1wt%Am) and 2mg of crosslinking agent MBA (0.1wt%Am) were added to the solution and stirred to dissolve. The solution was then transferred to a polytetrafluoroethylene mold. Finally, the mold was placed in a 70°C constant temperature incubator for thermally initiated polymerization for 12h. After the reaction, the mixture was cooled to room temperature to obtain a hydrogel sample. The mass ratio of acrylamide (Aam), N,N'-methylenebisacrylamide (MBA), hydroxypropyl methylcellulose acetoacetate (HPMCAA), 7-acrylamido-4-methylcoumarin (AAMC), and potassium persulfate (KPS) was 100:0.1:3:0.4:1.
[0097] Example 8
[0098] The preparation method of cellulose grafted polymer hydrogel with multiple stimulus responsiveness includes the following steps:
[0099] (1) The preparation of hydroxypropyl methylcellulose acetoacetate (HPMCAA) is the same as in Example 1;
[0100] (2) The preparation of 7-acrylamido-4-methylcoumarin (AAMC) was the same as in Example 1;
[0101] (3) Preparation of hydrogels
[0102] First, 2g of acrylamide (Am) and 6mg of 7-acrylamido-4-methylcoumarin (AAMC) were added to 10mL of deionized water and ultrasonically dispersed for 20 min to obtain a homogeneous solution. Then, 60mg of hydroxypropyl methylcellulose acetoacetate (HPMCAA) was added to the solution and stirred to dissolve, resulting in a uniformly dispersed solution. The pH of the solution was adjusted to 12. Next, 20mg of initiator KPS (1wt%Am) and 2mg of crosslinking agent MBA (0.1wt%Am) were added to the solution and stirred to dissolve. The solution was then transferred to a polytetrafluoroethylene mold. Finally, the mold was placed in a 70°C constant temperature incubator for thermally initiated polymerization for 12h. After the reaction, the mixture was cooled to room temperature to obtain a hydrogel sample. The mass ratio of acrylamide (Aam), N,N'-methylenebisacrylamide (MBA), hydroxypropyl methylcellulose acetoacetate (HPMCAA), 7-acrylamido-4-methylcoumarin (AAMC), and potassium persulfate (KPS) was 100:0.1:3:0.4:1.
[0103] Comparative Example 1
[0104] The preparation method is the same as that described in Example 1, except that step (1) is not performed and hydroxypropyl methylcellulose acetoacetate (HPMCAA) is not added in step (3).
[0105] Comparative Example 2
[0106] The preparation method is the same as described in Example 1, except that step (2) is not performed and 7-acrylamido-4-methylcoumarin (AAMC) is not added in step (3).
[0107] Experimental Example 1
[0108] The tensile properties test method of hydrogel: The prepared hydrogel was cut into dumbbell-shaped strips with a length of 20 mm, a width of 3 mm, and a thickness of 2 mm. The tensile test was carried out using a universal testing machine (INSTRON model 3344) at a tensile speed of 100 mm / min.
[0109] Method for testing the transmittance of hydrogels: The prepared hydrogels were cut into strips with a thickness of 10 mm. The transmittance of the hydrogels was measured using a UV-Vis spectrophotometer (U-3900H, Hitachi, Japan). The test wavelength was 400 nm and the test temperature range was 20-80°C. The temperature corresponding to a transmittance of 50% was defined as the phase transition temperature.
[0110] Fluorescence property testing method for hydrogels: The prepared hydrogels were cut into strips with a thickness of 10 mm, and the fluorescence emission spectrum of the gels was obtained using a high-sensitivity integrated fluorescence spectrophotometer (FM-4). The excitation wavelength range was 339-648 nm, and the test temperature was room temperature (25°C). The test results of elastic modulus, toughness, phase transition temperature, and fluorescence intensity of samples from Examples 1-8 and Comparisons 1-2 are shown in Table 1.
[0111] Table 1
[0112]
[0113] Combining Comparative Example 1 and Examples 1-4, it can be seen that with increasing HPMCAA concentration, the elastic modulus increases, while the toughness initially increases and then decreases. This is because the introduction of rigid polysaccharide polymers increases the physical entanglement between polymer chains, thus increasing the elastic modulus. However, excessive HPMCAA weakens the hydrogen bonding interactions between acrylamide chains, leading to a decrease in toughness. Furthermore, it can be seen that hydroxypropyl methylcellulose acetoacetate is the only factor imparting thermosensitivity to the hydrogel; with increasing HPMCAA concentration, the phase transition temperature decreases (see...). Figure 4 The reason is that as the concentration of HPMCAA increases, the intermolecular distance decreases, making it easier for them to aggregate and precipitate at lower temperatures.
[0114] As can be seen from Comparative Example 2 and Examples 5-7, the fluorescence intensity of the gel gradually increases with increasing coumarin concentration (see Comparative Example 2). Figure 5 Although the elastic modulus, toughness, and tensile strength of the gel decreased, it is speculated that the introduction of this monomer weakened the hydrogen bonding interactions between acrylamides, resulting in a decrease in mechanical properties, but did not affect other properties of the gel.
[0115] Combining Comparative Example 2 and Examples 6 and 8, it can be seen that the fluorescent monomer coumarin has a characteristic absorption at 330 nm, and the absorbance gradually decreases with increasing pH (see Comparative Example 2). Figure 6 Furthermore, the fluorescence emission intensity of the hydrogel gradually decreases at 390 nm and a new emission peak appears at approximately 470 nm. This is because, under alkaline conditions, the ester carbonyl group of the coumarin unit undergoes an enol tautomerization, leading to a change in fluorescence behavior.
[0116] In summary, the hydrogel prepared by this invention exhibits a synergistic response to triple stimulation from temperature, pH, and ultraviolet light.
Claims
1. A cellulose graft polymer hydrogel with multiple stimuli responsiveness, the hydrogel being obtained by initiating polymerization of hydroxypropyl methylcellulose acetoacetate (HPMCAA), 7-acrylamido-4-methylcoumarin (AAMC), acrylamide (Am), and N,N'-methylenebisacrylamide (MBA) under a thermal initiation system.
2. The cellulose grafted polymer hydrogel with multi-stimulus responsiveness according to claim 1, characterized in that, The mass ratio of hydroxypropyl methylcellulose acetoacetate (HPMCAA), 7-acrylamido-4-methylcoumarin (AAMC), N,N'-methylenebisacrylamide (MBA) to acrylamide (Am) is (1~10):(0.1~2):(0.1~1):
100.
3. The cellulose grafted polymer hydrogel with multi-stimulus responsiveness according to claim 1, characterized in that, The initiator used in the initiation system is potassium persulfate, and the mass ratio of initiator to acrylamide is (0.2~5):
100.
4. The cellulose grafted polymer hydrogel with multi-stimulus responsiveness according to claim 1, characterized in that, The hydroxypropyl methylcellulose acetoacetate (HPMCAA) is prepared by the following method: (1) Esterification: Hydroxypropyl methylcellulose was dried thoroughly in an oven, then dissolved in N-N'-dimethylformamide by stirring, and then tert-butyl acetoacetate was added to carry out the reaction. (2) Purification: After the reaction is completed, the reaction solution is added to anhydrous ethanol to precipitate, and then filtered, washed and dried to obtain hydroxypropyl methylcellulose acetoacetate (HPMCAA).
5. The cellulose grafted polymer hydrogel with multi-stimulus responsiveness according to claim 4, characterized in that, In step (1), the degree of substitution of the hydroxypropyl methylcellulose (HPMC) is methoxy: 28-30%; hydroxypropyl: 7.0-12%, the viscosity of the 2wt% aqueous solution of the hydroxypropyl methylcellulose is 3-100 mPa·s, the drying temperature of the hydroxypropyl methylcellulose is 60-100℃, the drying time is 1-5h, the mass ratio of the hydroxypropyl methylcellulose to the volume of N-N'-dimethylformamide is 1g:(3-7)mL, the stirring and dissolving temperature is 60-120℃, the stirring and dissolving time is 1-2h, the mass ratio of the hydroxypropyl methylcellulose to the volume of tert-butyl acetoacetate is 1g:(0.5-3)mL, the reaction temperature is 80-120℃, and the reaction time is 3-7h.
6. The cellulose grafted polymer hydrogel with multi-stimulus responsiveness according to claim 4, characterized in that, In step (2), the volume ratio of the reaction solution to the anhydrous ethanol used for precipitation is 1:10~20, the washing is performed by stirring and washing with anhydrous ethanol 3-6 times, the drying temperature is 40-80℃, and the drying time is 6-12h.
7. The cellulose grafted polymer hydrogel with multi-stimulus responsiveness according to claim 1, characterized in that, The specific preparation method of the fluorescent monomer 7-acrylamido-4-methylcoumarin (AAMC) is as follows: 1) Acylation: 7-amino-4-methylcoumarin was added to tetrahydrofuran (THF), stirred and dispersed thoroughly, and then acryloyl chloride and triethylamine were added to carry out the reaction; 2) Purification: After the reaction is completed, THF is removed by rotary evaporation. The product is washed, filtered and dried in anhydrous ethanol to obtain 7-acrylamido-4-methylcoumarin (AAMC).
8. The cellulose grafted polymer hydrogel with multi-stimulus responsiveness according to claim 7, characterized in that, In step 1), the molar ratio of 7-amino-4-methylcoumarin, acryloyl chloride, and triethylamine is 1:(1.1-1.5):(1.1-1.5). In step 1), the molar amount of 7-amino-4-methylcoumarin to the volume ratio of tetrahydrofuran is 4-10 mmol:40-100 mL. In step 1), the reaction temperature is -5 to 5°C, and the reaction time is 6 to 24 h. In step 2), the washing is performed by stirring with anhydrous ethanol 3-6 times. The drying temperature is 40-80°C, and the drying time is 6-12 h.
9. The method for preparing the cellulose grafted polymer hydrogel with multi-stimulus responsiveness according to claim 1, comprising the following steps: Acrylamide (Aam), hydroxypropyl methylcellulose acetoacetate (HPMCAA), 7-acrylamido-4-methylcoumarin (AAMC), and N,N'-methylenebisacrylamide (MBA) were added to deionized water and ultrasonically dispersed to obtain a homogeneous solution. Then, a thermal initiator was added, and polymerization was initiated by heating to obtain a multi-stimulus responsive cellulose graft polymer hydrogel.
10. The preparation method according to claim 9, characterized in that, The mass ratio of acrylamide to deionized water is 1 g: (3~10) mL, the mass ratio of hydroxypropyl methylcellulose acetoacetate (HPMCAA) to acrylamide is (0.0-0.1):1, the mass ratio of 7-acrylamido-4-methylcoumarin (AAMC) to acrylamide is (0.001-0.02):1, the mass ratio of N,N'-methylenebisacrylamide (MBA) to acrylamide is (0.001-0.01):1, the polymerization reaction temperature is 60~80℃, and the polymerization reaction time is 2~6 h.