Thermosensitive composite PNIPAAm hydrogel as well as preparation method and application thereof

Abstract

The preparation method comprises the following steps: mixing a first monomer, a second monomer, a cross-linking agent, a photoinitiator and a solvent according to a ratio, carrying out water bath heating and stirring until complete dissolution so as to obtain a precursor solution, pouring the precursor solution into a PTFE round mold, and carrying out photocuring molding under an illumination condition so as to obtain the temperature-sensitive composite PNIPAAm hydrogel. The composite PNIPAAm hydrogel is placed in deionized water to be fully swelled, unreacted raw materials are removed, and the composite PNIPAAm hydrogel is obtained. According to the invention, NIPAAm is taken as a first monomer, and a second monomer AM or BA is coupled to regulate and control the critical solution temperature of PNIPAAm hydrogel, so that the thermochromic temperature test patch prepared from the PNIPAAm hydrogel has the characteristics of excellent flexibility, remarkable reversible color change and adjustable response temperature range; the temperature sensor is widely applicable to body temperature testing of special crowds, such as a flexible developing thermometer and wearable equipment for rapid body temperature monitoring, and can be normally used in strong electromagnetic and humid environments.

Description

Technical Field

[0001] The present invention belongs to the technical field of temperature measurement, and in particular relates to a temperature-sensitive composite PNIPAAm hydrogel and a preparation method and application thereof. Background Art

[0002] Body temperature, as the most intuitive vital sign of the human body, can reflect a person's health status to a certain extent. Body temperature monitoring is an important part of medical care and family health management. Accurate and timely measurement of body temperature can provide the monitored person with relevant health risk warnings. At present, the mainstream mercury thermometers on the market are inconvenient to use. They need to be clamped tightly in the armpit and cannot be returned to their original position immediately after use. Mercury, as a toxic substance, also poses many safety hazards to the monitored person. In recent years, the emerging electronic thermometers on the market are relatively safe, but they still need to keep the contact position fixed, are easily affected by environmental interference, and are relatively expensive. In addition, common liquid crystal thermochromic materials have problems such as being unfriendly to the human body, complex preparation processes, and weak mechanical and chemical stability.

[0003] In the existing technology, thermochromic temperature test patches have been widely used due to their intuitive color changes and risk warning advantages, involving important fields such as electronic and electrical equipment, chemical and energy, food safety, and healthcare. Hydrogel, as a biologically favorable thermochromic material, has the advantages of simple preparation, stable physical and chemical properties, no biological toxicity, and controllability. Its unique compliance allows thermosensitive hydrogels to better contact the human body, while receiving the temperature transmitted by the human body and undergoing a significant color change, providing the monitored person with an intuitive temperature display and signal warning. Therefore, it is very necessary to develop a thermochromic temperature test patch that is easy to use, accurate in measurement, intuitive in signal, and inexpensive. Summary of the Invention

[0004] In order to achieve the goal of effective and intuitive detection of human body temperature, the main purpose of the present invention is to provide a thermosensitive composite PNIPAAm hydrogel, which has temperature responsiveness and thermochromic ability, and can be used for passive continuous, high-precision, wide temperature span and high visualization temperature measurement.

[0005] Another object of the present invention is to provide a method for preparing the thermosensitive composite PNIPAAm hydrogel, which has a simple process and is easy to operate.

[0006] Another object of the present invention is to provide an application of the thermosensitive composite PNIPAAm hydrogel in the preparation of a thermochromic temperature test patch, utilizing the temperature response characteristics and thermochromic ability of the thermosensitive composite PNIPAAm hydrogel to accurately monitor the body temperature of the person being measured.

[0007] To achieve the above object, the present invention adopts the following technical solutions:

[0008] In a first aspect of the present invention, a method for preparing a thermosensitive composite PNIPAAm hydrogel is provided, comprising the following steps:

[0009] S1. Preparing a composite PNIPAAm hydrogel precursor solution, the process comprising: mixing a first monomer, a second monomer, a crosslinker, a photoinitiator, and a solvent in proportion, heating and stirring in a water bath until completely dissolved, to obtain a clear and transparent composite PNIPAAm hydrogel precursor solution; wherein:

[0010] The first monomer is N-isopropylacrylamide (NIPAAm);

[0011] The second monomer is acrylamide (AM) and / or butyl acrylate (BA);

[0012] The cross-linking agent is N,N-methylenebisacrylamide (BIS) or polyethylene glycol diacrylate (PEGDA);

[0013] The photoinitiator is 2-hydroxy-2-methylphenylpropionone (Darocur 1173) or 2-hydroxy-4'-(2-hydroxyethoxy)-2-methylphenylpropionone (Irgacure 2959);

[0014] The solvent is N-methylformamide (NMF);

[0015] S2, photocuring molding of composite PNIPAAm hydrogel, the process comprising: pouring the composite PNIPAAm hydrogel precursor solution into a PTFE circular mold, and performing photocuring molding under ultraviolet light or visible light to obtain a composite PNIPAAm hydrogel;

[0016] S3, post-treatment of the composite PNIPAAm hydrogel, the process comprising: placing the composite PNIPAAm hydrogel in deionized water to fully swell, removing unreacted monomers and cross-linking agents, and storing in a cool and dry environment.

[0017] Preferably, in step S1, the first monomer accounts for 20%-75% of the total mass of the precursor solution, the cross-linking agent accounts for 0.1%-5% of the total mass of the precursor solution, the photoinitiator accounts for 0.05%-3% of the total mass of the precursor solution, the second monomer accounts for 1%-50% of the total mass of the precursor solution, and the remainder is NMF.

[0018] Preferably, in step S1, the water bath temperature is 60° C. and the stirring time is 6 h.

[0019] Preferably, in step S2, the illumination conditions of the ultraviolet light include: the wavelength of the ultraviolet light is 365-405 nm, the illumination power is 60 W, and the illumination time is 10-60 s.

[0020] Preferably, in step S3, the step of placing the composite PNIPAAm hydrogel in deionized water to fully swell is repeated to obtain a transparent and colorless temperature-sensitive composite PNIPAAm hydrogel.

[0021] In a second aspect, the present invention provides a thermosensitive composite PNIPAAm hydrogel, which is obtained by the aforementioned method for preparing the thermosensitive composite PNIPAAm hydrogel.

[0022] The third aspect of the present invention provides the use of the temperature-sensitive composite PNIPAAm hydrogel in the preparation of a thermochromic temperature test patch.

[0023] In a fourth aspect, the present invention provides a thermochromic temperature test patch, comprising the temperature-sensitive composite PNIPAAm hydrogel and a substrate, wherein the substrate is selected from one or more of polydimethylsiloxane (PDMS), polyurethane, and polycaprolactone.

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

[0025] 1. The thermosensitive composite PNIPAAm hydrogel of the present invention uses NIPAAm as a monomer and couples AM or BA to regulate the critical solution temperature (LCST) of the composite PNIPAAm hydrogel to achieve effective temperature display in specific scenarios.

[0026] Second, the present invention introduces a crosslinker, BIS, into the precursor solution to achieve hydrogel curing through chemical crosslinking, regulating the density of the hydrogel crosslinked network and further achieving suitable mechanical strength. Simultaneously, the photoinitiator, Darocur 1173, is introduced into the precursor solution to achieve rapid photocuring through ultraviolet or visible light-induced free radical polymerization.

[0027] Third, the present invention achieves adjustable color change behavior at 30-40°C by introducing AM or BA into the material system to regulate the phase change response temperature of the hydrogel. At the same time, the softness, lightness, and strong stability of the thermosensitive composite PNIPAAm hydrogel are fully utilized to prepare a thermochromic temperature test patch with excellent flexibility, significant reversible color change, and adjustable response temperature range. It is comfortable to wear and has strong applicability in special scenarios. It can be used normally in strong electromagnetic and humid environments. It is widely applicable to temperature testing near the temperature of the human body (infants, the elderly, and patients), flexible color thermometers, and wearable devices for rapid body temperature monitoring.

[0028] Fourth, the thermochromic temperature test patch of this invention is safe. The composite PNIPAAm hydrogel and substrate are both certified biocompatible and free of heavy metals and electronic waste. This temperature test patch requires no battery power and operates passively. By regulating the LCST to achieve a sudden change in the thermal threshold, it significantly improves response speed, offers high visualization, and offers the potential for reusability and significant cost advantages. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 Schematic diagram of the temperature test patch model of the PNIPAAm hydrogel in the embodiment.

[0030] Figure 2 This is the DSC spectrum of the PNIPAAm hydrogel in the example.

[0031] Figure 3 This is a picture demonstrating the temperature-optical phase transition process of PNIPAAm hydrogel in the embodiment.

[0032] Figure 4 The microscopic voids of the composite PNIPAAm hydrogel prepared in the dimethyl sulfoxide (DMSO) system were tested using a scanning electron microscope (SEM) in the examples.

[0033] Figure 5 The microscopic voids of the composite PNIPAAm hydrogel prepared by the NMF system were tested using SEM in the examples. DETAILED DESCRIPTION

[0034] In order to more fully understand and demonstrate the technical solutions, objectives, and advantages of the present invention, the following is a further detailed and complete description of the technical effects produced by the present invention in conjunction with the accompanying drawings and specific embodiments. Obviously, the described embodiments are only some of the embodiments of the present invention, and not all of them. It should be pointed out that for those skilled in the art, other embodiments obtained without departing from the concept of the present invention are all within the scope of protection of the present invention.

[0035] like Figure 1 As shown, a thermochromic temperature test patch is exemplarily described, including a temperature-sensitive composite PNIPAAm hydrogel layer 1, a PDMS encapsulation film 2 and a PDMS encapsulation film 3.

[0036] Example 1

[0037] In this example, a thermosensitive composite PNIPAAm hydrogel was prepared by the following steps:

[0038] S1: Preparation of composite PNIPAAm hydrogel precursor solution

[0039] NIPAAm, BIS, Darocur 1173, AM and NMF were mixed in a certain proportion, heated in a water bath and stirred until completely dissolved to obtain a composite PNIPAAm hydrogel precursor solution; the amount of NIPAAm was 20wt%, the amount of BIS was 0.5wt%, the amount of Darocur 1173 was 0.05wt%, the amount of AM was 10wt%, and the balance was NMF. The water bath heating temperature was 60°C and the stirring time was 6h.

[0040] S2: Photocuring of composite PNIPAAm hydrogels

[0041] The composite PNIPAAm hydrogel precursor solution was poured into a PTFE circular mold and placed under an ultraviolet lamp with a wavelength of 365-405 nm for photocuring and polymerization for 10-60 seconds to obtain a composite PNIPAAm hydrogel.

[0042] S3: Post-treatment of composite PNIPAAm hydrogels

[0043] The composite PNIPAAm hydrogel was placed in deionized water to fully swell, and unreacted monomers, cross-linking agents and solvents were removed to obtain a thermosensitive composite PNIPAAm hydrogel, which was then stored in a cool and dry environment.

[0044] Example 2

[0045] In this example, a thermosensitive composite PNIPAAm hydrogel was prepared by the following steps:

[0046] S1: Preparation of composite PNIPAAm hydrogel precursor solution

[0047] NIPAAm, BIS, Darocur 1173, BA and NMF were mixed in a certain proportion, heated in a water bath and stirred until completely dissolved to obtain a composite PNIPAAm hydrogel precursor solution; wherein the amount of NIPAAm was 20wt%, the amount of BIS was 0.5wt%, the amount of Darocur 1173 was 0.05wt%, the amount of BA was 10wt%, and the balance was NMF. The water bath heating temperature was 60°C and the stirring time was 6h.

[0048] S2: Photocuring of composite PNIPAAm hydrogels

[0049] The composite PNIPAAm hydrogel precursor solution was poured into a PTFE circular mold and placed under an ultraviolet lamp with a wavelength of 365-405 nm for photocuring and polymerization for 10-60 seconds to obtain a composite PNIPAAm hydrogel.

[0050] S3: Post-treatment of composite PNIPAAm hydrogels

[0051] The composite PNIPAAm hydrogel was placed in deionized water to fully swell, and unreacted monomers, cross-linking agents and solvents were removed to obtain a thermosensitive composite PNIPAAm hydrogel, which was then stored in a cool and dry environment.

[0052] Example 3

[0053] In this example, a thermosensitive composite PNIPAAm hydrogel was prepared by the following steps:

[0054] S1: Preparation of composite PNIPAAm hydrogel precursor solution

[0055] NIPAAm, BIS, Darocur 1173, AM, and DMSO were mixed in a specific ratio and stirred in a water bath until completely dissolved to obtain a composite PNIPAAm hydrogel precursor solution. The NIPAAm content was 40 wt%, BIS was 0.5 wt%, Darocur 1173 was 0.5 vol%, AM was 5 wt%, and the balance was DMSO. The water bath temperature was 60°C and the stirring time was 6 hours.

[0056] S2: Photocuring of composite PNIPAAm hydrogels

[0057] The composite PNIPAAm hydrogel precursor solution was poured into a PTFE circular mold and placed under an ultraviolet lamp with a wavelength of 365-405 nm for photocuring and polymerization for 10-60 seconds to obtain a composite PNIPAAm hydrogel.

[0058] S3: Post-treatment of composite PNIPAAm hydrogels

[0059] The composite PNIPAAm hydrogel was placed in deionized water to fully swell, and unreacted monomers, cross-linking agents and solvents were removed to obtain a thermosensitive composite PNIPAAm hydrogel, which was then stored in a cool and dry environment.

[0060] Example 4

[0061] In this embodiment, a composite PNIPAAm hydrogel is prepared by the following steps:

[0062] S1: Preparation of composite PNIPAAm hydrogel precursor solution

[0063] NIPAAm, BIS, Darocur 1173, BA, and DMSO were mixed in a specific ratio and stirred in a water bath until completely dissolved to obtain a composite PNIPAAm hydrogel precursor solution. The NIPAAm content was 40 wt%, BIS was 0.5 wt%, Darocur 1173 was 0.5 vol%, BA was 5 wt%, and the balance was DMSO. The water bath temperature was 60°C and the stirring time was 6 hours.

[0064] S2: Photocuring of composite PNIPAAm hydrogels

[0065] The composite PNIPAAm hydrogel precursor solution was poured into a PTFE circular mold and placed under an ultraviolet lamp with a wavelength of 365-405 nm for photocuring and polymerization for 10-60 seconds to obtain a composite PNIPAAm hydrogel.

[0066] S3: Post-treatment of composite PNIPAAm hydrogels

[0067] The composite PNIPAAm hydrogel was placed in deionized water to fully swell, and unreacted monomers, cross-linking agents and solvents were removed to obtain a thermosensitive composite PNIPAAm hydrogel, which was then stored in a cool and dry environment.

[0068] Example 5

[0069] In this embodiment, a composite PNIPAAm hydrogel is prepared by the following steps:

[0070] S1: Preparation of composite PNIPAAm hydrogel precursor solution

[0071] NIPAAm, BIS, ammonium persulfate (APS), AM, tetramethylethylenediamine (TEMED), and deionized water were mixed in a certain proportion to obtain a transparent precursor solution. The amount of NIPAAm was 20wt%, BIS was 0.05wt%, APS was 0.1wt%, AM was 5wt%, TEMED was 0.05wt%, and the balance was deionized water.

[0072] S2: Photocuring of composite PNIPAAm hydrogels

[0073] The precursor solution was poured into a PTFE circular mold and placed at room temperature for 12-24 h to obtain a composite PNIPAAm hydrogel.

[0074] S3: Post-treatment of composite PNIPAAm hydrogels

[0075] The composite PNIPAAm hydrogel was placed in deionized water to fully swell, and unreacted monomers, cross-linking agents and solvents were removed to obtain the composite PNIPAAm hydrogel, which was then stored in a cool and dry environment.

[0076] Example 6

[0077] The process of preparing the composite PNIPAAm hydrogel in this example was the same as that in Example 5 except that BA was replaced by AM.

[0078] Example 7

[0079] In the process of preparing the composite PNIPAAm hydrogel in this example, except that Darocur 1173 was replaced with 2-hydroxy-4'-(2-hydroxyethoxy)-2-methylpropiophenone (Irgacure 2959), other processes were the same as those in Example 1.

[0080] Example 8

[0081] The process of preparing the composite PNIPAAm hydrogel in this example was the same as that in Example 1 except that BIS was replaced by polyethylene glycol diacrylate (PEGDA).

[0082] The LCST of the composite PNIPAAm hydrogel was tested by differential scanning calorimetry (DSC) to obtain the distribution of the LCST of the hydrogel. Figure 2 When the temperature test patch containing the composite PNIPAAm hydrogel exceeds the LCST, it rapidly responds to temperature, as shown in Figure 3 As shown, it changes from a transparent state to white, which directly reflects the temperature information. The microscopic voids of the composite PNIPAAm hydrogel were tested using a scanning electron microscope (SEM). The PNIPAAm hydrogel prepared by the DMSO system has larger microscopic voids ( Figure 4 ), the PNIPAAm hydrogel prepared by NMF system has a larger pore density and a smaller pore radius ( Figure 5 ).

[0083] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Those skilled in the art will readily appreciate that various modifications and variations of the present invention are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention are intended to be within the scope of protection of the present invention.

Claims

1. A method for preparing a thermosensitive composite PNIPAAm hydrogel, characterized in that: The following steps are involved: S1. Preparing a composite PNIPAAm hydrogel precursor solution, the process comprising: mixing a first monomer, a second monomer, a crosslinker, a photoinitiator, and a solvent in proportion, heating and stirring in a water bath until completely dissolved, to obtain a composite PNIPAAm hydrogel precursor solution; wherein: The first monomer is N-isopropylacrylamide; The second monomer is acrylamide and / or butyl acrylate; The cross-linking agent is N,N-methylenebisacrylamide or polyethylene glycol diacrylate; The photoinitiator is 2-hydroxy-2-methylphenylpropiophenone or 2-hydroxy-4'-(2-hydroxyethoxy)-2-methylphenylpropiophenone; The solvent is N-methylformamide; S2, photocuring molding of composite PNIPAAm hydrogel, the process comprising: pouring the composite PNIPAAm hydrogel precursor solution into a PTFE circular mold, and performing photocuring molding under ultraviolet light or visible light to obtain a composite PNIPAAm hydrogel; S3, post-treatment of the composite PNIPAAm hydrogel, the process comprising: placing the composite PNIPAAm hydrogel in deionized water to fully swell, and removing unreacted monomers, cross-linking agents, photoinitiators and solvents to obtain the composite PNIPAAm hydrogel.

2. The method for preparing the thermosensitive composite PNIPAAm hydrogel according to claim 1, characterized in that: In step S1, the first monomer accounts for 20%-75% of the total mass of the precursor solution, the cross-linking agent accounts for 0.1%-5% of the total mass of the precursor solution, the photoinitiator accounts for 0.05%-3% of the total mass of the precursor solution, the second monomer accounts for 1%-50% of the total mass of the precursor solution, and the remainder is solvent.

3. The method for preparing the thermosensitive composite PNIPAAm hydrogel according to claim 1, wherein: In step S1, the water bath heating temperature is 60° C. and the stirring time is 6 h.

4. The method for preparing the thermosensitive composite PNIPAAm hydrogel according to claim 1, wherein: In step S2, the illumination conditions of the ultraviolet light include: the wavelength of the ultraviolet light is 365-405 nm, the illumination power is 60 W, and the illumination time is 10-60 s.

5. The method for preparing the thermosensitive composite PNIPAAm hydrogel according to claim 1, wherein: In step S3, the step of placing the composite PNIPAAm hydrogel in deionized water to fully swell is repeated to obtain a transparent and colorless temperature-sensitive composite PNIPAAm hydrogel.

6. A thermosensitive composite PNIPAAm hydrogel, characterized in that: The thermosensitive composite PNIPAAm hydrogel is obtained by the preparation method of any one of claims 1 to 5.

7. Use of the thermosensitive composite PNIPAAm hydrogel according to claim 6 in the preparation of a thermochromic temperature test patch.

8. A thermochromic temperature test patch, characterized in that: The thermosensitive composite PNIPAAm hydrogel according to claim 6 also includes a substrate.

9. The thermochromic temperature test patch according to claim 8, characterized in that: The substrate is selected from one or more of polydimethylsiloxane, polyurethane, and polycaprolactone.

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