基于P(NIPAM-AA)的多刺激响应智能水凝胶的设计及其应用研究

智能响应水凝胶能够对多种外界刺激（如温度、压力、pH值、光照和磁场）产生基础物性的变化（亲疏水性、光透过率、力学性能、体积），因而被广泛应用于组织工程修复、仿生柔性传感器件和生物医用领域。近年来，凭借其优异的柔韧性、导电性及对刺激的响应驱动能力，智能响应水凝胶在智能化器件领域的应用得到了进一步拓展。然而，传统响应性水凝胶刺激响应性通常较为单一，其响应机制不够明确且响应的重复性较差，逐渐无法满足复杂场景的应用需求。因此，开发一种能够响应多种刺激兼具优异力学性能的水凝胶，对拓宽其应用场景具有重要的研究意义和研究挑战。本论文以聚（N-异丙基丙烯酰胺）（PNIPAM）复合水凝胶为研究目标，提出了光引发的共聚合方法，实现系列不同响应复合水凝胶的制备。取得的主要研究结果如下：

1. 发展了一种简易高效的光固化方法，通过引入丙烯酸（AA）单体，制备得到兼具热和pH双重响应的光谱调控P(NIPAM-AA)水凝胶。该水凝胶在较宽的温度范围下展现出良好的近红外隔绝率，在20℃和40℃之间的可见光调制效率为56.5%。同时该凝胶在环境从碱性变化到酸性时，可调制颜色从透明到模糊。

2．发展了掺杂壳聚糖（CS）策略，制备了CS/P(NIPAM-AA)复合水凝胶，实现力学性能的增强。研究结果表明掺杂复合水凝胶的拉伸强度提升了13.5倍，断裂拉伸应变提升了2倍，且其保湿性能、抗冻性能、响应性能得到增强。此外，基于CS/P(NIPAM-AA)复合水凝胶构筑的智能窗器件展现出优异的红外光谱调节特性，即在阳光充足时具有4-6℃的智能降温效果，且在阴天时则几乎不对温度做出调节，

3. 发展了原位还原法制备多组分AgNPs/CS/P(NIPAM-AA)复合水凝胶。研究结果表明，该复合水凝胶在0-600%拉伸应变下的灵敏度系数GF为5.06，R²=0.97。同时其在20℃和50℃温度变化下有着稳定且灵敏的温度变化，响应时间为0.69 s。基于该水凝胶构筑的传感器件在力学传感、温度传感、指关节运动监测的应用中都展现出了良好的应用前景。

Intelligent responsive hydrogels can change in basic physical properties (hydrophilicity, hydrophobicity, light transmittance, mechanical properties, and volume) in response to a variety of external stimuli (such as temperature, pressure, pH, light, and magnetic field). Therefore, intelligent responsive hydrogels are widely used in tissue engineering repair, biomimetic flexible sensor devices, and biomedical fields. In recent years, the application of smart responsive hydrogels in intelligent devices has been further expanded due to their excellent flexibility, electrical conductivity, and ability to respond to stimuli. However, the stimulus responsiveness of traditional responsive hydrogels is usually single, and their response mechanism is not clear and the repeatability of response is poor, which gradually cannot meet the application needs of complex scenarios. Therefore, it is of great research significance and research challenge to develop a hydrogel that can respond to a variety of stimuli and has excellent mechanical properties to broaden its application scenarios.

In this thesis, poly (N-isopropyl acrylamide) (PNIPAM) composite hydrogels were studied, and a photoinitiated copolymerization method was proposed to fabricate a series of composite hydrogels with different responses. Key findings were as follows:

1. A simple and efficient light-curing method was developed to prepare spectrally regulated P(NIPAM-AA) hydrogel with both thermal and pH response by introducing acrylic acid monomer. The hydrogel exhibited excellent NIR isolation over a wide temperature range, with a visible light modulation efficiency of 56.5% between 20 ℃ and 40 ℃. At the same time, the color of the gel can be modulated from transparent to fuzzy when the environment changes from alkaline to acidic.

2. The strategy of doped chitosan was developed and CS/P(NIPAM-AA) composite hydrogel was prepared to achieve enhanced mechanical properties. The results show that the tensile strength of the doped composite hydrogel is increased by 13.5 times, the tensile strain is increased by 2 times, and its moisture retention, freezing resistance, and response properties are enhanced. In addition, the smart window device based on CS/P(NIPAM-AA) composite hydrogel shows excellent infrared spectral adjustment characteristics, it has an intelligent cooling effect of 4-6 ℃ in sunny days, and almost no temperature adjustment in cloudy days.

3. In situ reduction method was developed to prepare multi-component AgNPs/CS/P(NIPAM-AA) composite hydrogel. The results showed that the sensitivity coefficient of the composite hydrogel under 0-600% tensile strain was 5.06, and R²=0.97. At the same time, it has a stable and sensitive temperature change under the temperature change of 20℃ and 50℃, and the response time is 0.69 s. The sensor based on the hydrogel has shown good application prospects in mechanical sensing, temperature sensing, and finger joint motion monitoring.

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