【作者】 徐颖；

【导师】 刘国栋； 薛融；

【作者基本信息】 陕西科技大学 ， 轻工技术与工程， 2023， 硕士

【摘要】 水凝胶由于其对环境刺激的良好响应性和生物相容性,在驱动器领域受到了大量的研究与关注。其中,聚(N-异丙基丙烯酰胺)(PNIPAM)由于能够在接近人体体温的低临界溶液温度下发生相变从而产生体积变化,因而在驱动器领域受到了广泛的关注。但是常规的PNIPAM水凝胶由于响应速度较慢、机械性能较差等原因,使得它的应用受到了很大程度的影响。本文利用金属配位、氢键增强水凝胶等方法制备了具有良好刺激响应性能和机械性能的Nipam基软体水凝胶驱动器,具体工作内容如下:(1)PNIPAM/Fe3+/羧基化纳米纤维素(CNF-c)温度敏感型水凝胶的制备。将Fe3+和羧基化纳米纤维素的络合物作为纳米填料引入Nipam前驱体溶液中,在重力场作用下并经过自由基聚合形成了具有不对称结构的水凝胶驱动器。结果表明:相比于PNIPAM水凝胶,PNIPAM/Fe3+/CNF-c水凝胶具有更好的温度敏感性能。当Fe3+浓度为0.055 mol/L时,复合水凝胶的驱动速度最快,在23秒内可以弯曲180°,并且具有良好的可重复驱动性。更重要的是Fe3+和羧基化纳米纤维素中的羧基的配位作用使得水凝胶的机械性能有了很大的提高,所制备的复合水凝胶可以被制备成抓手,用来夹取、运输和释放物体。该制备方法具有简单的工艺流程且具有快速的驱动响应速度,这为水凝胶驱动器的制备提供了一种全新的思路。(2)PNIPAM/PEDOT:PSS/XLG(PNIPAM/聚(3,4-乙烯二氧噻吩/聚苯乙烯磺酸盐)/纳米粘土)光响应型软体驱动器的制备。本章中以纳米粘土为物理交联剂,将PEDOT:PSS作为光热转换材料掺杂进Nipam水凝胶内,制备了双层结构光响应型水凝胶。结果表明:纳米粘土及PEDOT:PSS与Nipam之间的氢键作用可以有效增强水凝胶的机械性能。当XLG的浓度为0.05 mol/L时,水凝胶的拉伸强度由9KPa上升到64 KPa,提升了 6.1倍,断裂伸长率从221%提升到1479%,提升了 5.69倍。且随着PEDOT:PSS浓度增加,光热转换性能增强。在移去红外光后,水凝胶在30 s内恢复到原来水平,有良好的可循环驱动性。此外,本章中也初步探索了复合水凝胶在柔性传感器领域应用的可能性。(3)PNIPAM/Fe3+/单宁酸(PNIPAM/Fe3+/TA)光响应型软体驱动器的制备。以Fe3+/TA作为光热转换材料使用梯度渗透法制备了具有各向异性结构的光响应型水凝胶。结果表明:TA与PNIPAM的氢键作用及Fe3+/TA的配位作用使得水凝胶具有更好的力学性能,PNIPAM/Fe3+/TA水凝胶在808 nm处吸光度可以达到77%,使用红外光照射时,水凝胶在30秒内弯曲了70°,而撤去红外光后在15 min内回复到了20°。且Fe3+可以局部渗透进水凝胶内,实现了 PNIPAM水凝胶的局部增强。为水凝胶驱动器在4D打印等领域的潜在应用提供了新的启示。本文以NIPAM作为水凝胶驱动器基材,制备了多种NIPAM基水凝胶驱动器,研究了驱动机理,并通过多种方法调节驱动器的结构,提高了驱动器的驱动性能,对于探索高性能NIPAM基水凝胶驱动器有着重要意义。更多还原

【Abstract】 Due to their excellent responsiveness to environmental stimuli and biocompatibility,hydrogels have attracted significant research and attention in the field of actuators.Among them,poly(N-isopropylacrylamide)(PNIPAM)has received widespread attention because it exhibits a volume change through a phase transition close to the human body temperature.However,conventional PNIPAM hydrogels suffer from slow response rates and poor mechanical properties,sabotaging their potential for use in actuators,and significantly limiting their applications.In this work,NIPAM-based soft hydrogel actuators were developed with improved stimuli-responsiveness and mechanical performance,using techniques including metal coordination and hydrogen bonding.The details of this work are outlined below:(1)Preparation of PNIPAM/Fe3+/carboxylated nanocellulose(CNF-c)temperature-sensitive hydrogel:The complex of Fe3+ and carboxylated nanocellulose was added as a nanofiller into the NIPAM precursor solution.Under the influence of gravity and subsequent free radical polymerization,an asymmetrically structured hydrogel actuator was formed.The results indicated that compared with PNIPAM hydrogels,PNIPAM/Fe3+/CNF-c hydrogels exhibited superior temperature sensitivity.The composite hydrogel with a Fe3+concentration of 0.055 mol/L showed the fastest actuation speed,achieving a 180°bending within 23 seconds while maintaining excellent repeatability.Moreover,the coordination between Fe3+ and carboxyl groups in the carboxylated nanocellulose significantly enhanced the mechanical properties of the hydrogel.The prepared composite hydrogel can be fabricated into grippers for object manipulation,transportation,and release.The proposed strategy providing a novel approach for fabricating hydrogel actuators with high performance.(2)Preparation of PNIPAM/PEDOT:PSS/XLG(PNIPAM/poly(3,4ethylenedioxythiophene):poly(styrene sulfonate)/nanoclay)photo-responsive soft actuators.In this chapter,a dual-layered photo-responsive hydrogel was prepared using nanoclay as a physical crosslinker and PEDOT:PSS as a photo-thermal conversion material incorporated into the NIPAM hydrogel.The results demonstrated that the hydrogen bonding interaction between nanoclay and PEDOT:PSS effectively enhanced the mechanical properties of the hydrogel.When the concentration of XLG was 0.05 mol/L,the tensile strength of the hydrogel increased from 9 KPa to 64 KPa,representing a 6.1 times improvement.The fracture elongation increased from 221%to 1479%,indicating a 5.69 times enhancement.Additionally,the photo-thermal conversion performance improved with an increase in PEDOT:PSS concentration.The hydrogel exhibited rapid recovery to its original state within 30 seconds after the removal of infrared light,demonstrating excellent cyclic actuation capability.Furthermore,this chapter also explored the potential application of the NIPAM/PEDOT:PSS/XLG composite hydrogel in the field of flexible sensors.(3)Preparation of PNIPAM/Fe3+/tannic acid(PNIPAM/Fe3+/TA)photoresponsive soft actuators.A gradient permeation method was employed utilizing Fe3+/TA as the photo-thermal conversion material to fabricate photo-responsive hydrogels with anisotropic structures.The results indicated that the hydrogen bonding interaction between TA and PNIPAM,as well as the coordination interaction between Fe3+ and TA,contribute to the improved mechanical properties of the hydrogel.The PNIPAM/Fe3+/TA hydrogel exhibited a maximum absorbance of 77%at 808 nm.Upon exposure to infrared light,the hydrogel undergoes a bending angle of 70° within 30 seconds,and it recovers to 20° within 15 minutes after the removal of infrared light.Furthermore,Fe3+ can selectively permeate into the hydrogel,enabling localized reinforcement of the PNIPAM hydrogel.These findings provide new insights for the potential applications of hydrogel actuators in fileds like 4D printing and so on.This thesis focuses on utilizing NIPAM as the matrix for fabricating hydrogel actuators and prepared various hydrogel actuators.The driving mechanism is investigated,and the structure of the actuators is modulated through multiple approaches to enhance their actuation performance.These efforts hold significant importance in exploring high-performance NIPAM-based hydrogel actuators.更多还原