【作者】 陈涛；

【导师】 朱美芳；

【作者基本信息】 东华大学 ， 材料学， 2021， 博士

【摘要】 人体神经与肌细胞等均表现为细长的纤维状形态,具有优异的信号传输、环境传感、防御保护等生理功能。经体内天然纤维启发,构筑结构、功能仿生的新型智能纤维材料,是当前的研究热点。水凝胶纤维即是一类优异的仿生材料,其可兼具水凝胶高含水、软弹等类组织功能特性,以及纤维高长径比、各向异性等结构优势,因而在组织工程、生物医药、柔性传感与智能驱动等领域具有广泛的应用前景。然而,大部分水凝胶纤维力学强度仍较低、溶胀不可控,难以匹配天然人体组织在多变应力场及复杂温湿环境中的力学及长效服役要求。为此,本研究围绕纳米复合水凝胶纤维的仿生构筑,以纳米粘土为物理交联点,以寡聚乙二醇甲醚甲基丙烯酸酯和丙烯酰胺类单体为共聚单元,通过类蜘蛛吐丝的“动态聚合拉伸”成纤技术构筑具有取向结构的高强纳米复合水凝胶纤维,并进一步通过原位氧化聚合与多级机械加捻等化学与物理改性手段,构筑系列具有导光、导电、多环境稳定的高力学性能纳米复合水凝胶纤维,并研究了其在柔性应变传感、阻尼及水汽驱动等领域的应用。本论文的主要研究内容和结论如下:1.采用“动态聚合拉伸”成纤技术,构筑了具有取向结构的高强纳米复合水凝胶光导纤维,分析了凝聚态取向结构演变与凝胶纤维光导及力学性能的相关性,探索了基于应变-光信号转换的传感应用。以纳米粘土/寡聚乙二醇甲醚甲基丙烯酸酯（OEGMA）/丙烯酰胺（AM）预聚液作为凝胶纺丝液,通过分析其凝胶化过程中的流变行为变化,确定成纤加工窗口,通过类蜘蛛吐丝的“动态聚合成纤”技术制备具有取向结构的粘土/P（OEGMA-co-AM）纳米复合水凝胶纤维。分析表明,在纤维成形过程中,拉伸力场诱导纳米粘土-聚合物微区沿纤维轴向取向排列,拉伸强度、韧性与光导性能分别提高至9.76 MPa,10.37 MJ·m^-3与0.26 dB·cm^-1。同时,溶剂中的甘油与水分子间的氢键相互作用,能够有效抑制水分子的结晶与蒸发,纤维在-20°C低温下仍表现出柔韧性能,且在25°C或50°C空气环境放置5天后,其力学/光学性能仍保持稳定。进一步利用该纤维构建应变-光信号传感器件,实现应变（0-100%）及应力（0.02～25 k Pa）的宽域、低阈值实时监测,在可穿戴或植入式应变传感器件领域具有广阔的应用前景。2.在高强纳米复合水凝胶纤维基础上,采用原位氧化聚合策略,在其内部构建聚苯胺二级网络,赋予凝胶纤维高力学、导电、耐溶胀等功能特性,探索了凝胶纤维在水环境中稳定服役的应变传感能力。以纳米粘土为物理交联点,以2-甲基-2-丙烯酸-2-（2-甲氧基乙氧基）乙酯（MEO₂MA）、OEGMA与N-异丙基丙烯酰胺（NIPAM）为共聚单体,利用“动态聚合拉伸”成纤技术制备了亲水性较上一章弱的纳米复合水凝胶纤维。进一步借鉴人体神经纤维的蛋白质异质组分结构,通过单体吸附及原位氧化聚合策略在凝胶纤维内部构建聚苯胺异质网络,得到杂化凝胶纤维。聚苯胺网络可在凝胶纤维基体中均匀分布,且可与粘土及聚合物链形成大量的非共价相互作用,与凝胶纤维的取向结构协同提高其力学性能,使杂化凝胶纤维的拉伸强度达7.21MPa,韧性达17.2 MJ·m^-3。此外,聚苯胺异质网络的引入有利于电子与离子在杂化凝胶纤维中的传输,杂化凝胶纤维电导性能可达87.99S·m^-1。同时,杂化凝胶纤维的机电信号滞后率低至4.5%,在5%的低应变下传感灵敏度为2.85,在180%的高应变下传感灵敏度为17.89,能够用于肢体运动及细微动作的灵敏快速监测。此外,基于聚苯胺分子引入后的杂化凝胶纤维的致密网络与其表面的微纳结构,该纤维表现出优异的抗溶胀性能,其平衡溶胀率小于100%,且在水环境中可保持稳定的电阻和应变传感性能,为柔性电子器件在多变温湿环境下的应用提供了基础。3.在高强纳米复合水凝胶纤维基础上,利用机械加捻技术,构筑多级仿生螺旋结构的凝胶纤维束,揭示了多级螺旋结构对凝胶纤维束机械性能的调控规律,探索了其在水汽传感等仿生器件领域的应用。在粘土、OEGMA、NIPAM凝胶预聚液中引入N,N-二甲基丙烯酰胺（DMAA）作为共聚单体,赋予纳米复合水凝胶纤维吸湿、高弹等性能,进一步借鉴动植物的宏观多级螺旋结构（如蜘蛛丝横丝、牵牛花藤蔓等）,利用多级加捻工艺构筑高韧性、阻尼及湿度响应的多级螺旋结构粘土/P（OEGMA-co-NIPAM-co-DMAA）纳米复合水凝胶纤维束。结果表明,随着捻度从0 TPM（捻每米）提升至450 TPM,单根凝胶纤维的力学强度可由19.46 MPa提高至23.14 MPa,但其伸长率由99.27%降至47.25%;双股凝胶纤维的最优捻度为250 TPM,其拉伸强度及韧性分别可达19.12 MPa和13.22 MJ·m^-3。进一步将双股加捻纤维作为基本单元,分别通过多级正向（+）与反向（-）加捻,构筑多级螺旋结构凝胶纤维束H-4（±）与H-8（±）。结果表明,多级螺旋加捻对纤维韧性提高起到了明显作用,H-8（+）与H-8（-）凝胶纤维韧性分别可达21.67 MJ·m^-3与18.96 MJ·m^-3,是单根凝胶纤维的2.9与2.6倍。并且,随着加捻层级的增加,凝胶纤维的取向度由单根凝胶纤维的0.71降低至H-8（+）的0.38。同时,H-8（+）凝胶纤维束具有优异的能量损耗性能以及吸湿致动性能,其机械能输出功率密度为5.6×10^-8W·kg^-1。该多级螺旋结构凝胶纤维在阻尼、弹性形状记忆以及水汽传感致动等领域展现了应用的潜力。更多还原

【Abstract】 Human nerve and muscle cells are fibrous morphology,and they exhibit excellent signal transmission,motion transmission,defense and other physiological functions.Inspired by such natural fiber structure,the construction of a new type of intelligent fiber material with bionic structure and function is one of current research hotspots.Hydrogel fiber is a kind of excellent biomimetic materials,which possesses tissue like characteristics of hydrogels such as high-water content,soft and elastic properties,as well as structural advantages of fibers such as high aspect ratio and anisotropy.Therefore,they have a wide application prospect in tissue engineering,biomedicine,flexible sensing and intelligent actuators.However,most hydrogel fibers still display low mechanical strength and uncontrollable swelling,which is difficult to match the mechanical and long-term service of natural human tissue in the variable stress field and complex temperature/humidity environment.Therefore,this dissertation is based on the bioinspired construction of nanocomposite hydrogel fiber,with clay nanoplatelets as physical cross-linkers,poly（ethylene glycol）methyl ether methacrylate and acrylamide as co-monomer.Such bioinspired nanocomposite hydrogel fibers were constructed by spider silk like“dynamic polymerization drawing”process,and were modified by in-situ oxidation polymerization and hierarchical twisting.Such fibers possessed high mechanical properties,light propagation properties,conductivity and multi-environment stability,displaying further applications in fields of flexible strain sensing,damping and intelligent actuators.The specific research contents and main results are as follows:1.Design and construction of nanocomposite gel fiber as light guide,as well as investigation of condensed structure evolution and strain sensing capability of such gel fibers.Taking advantages of clay based nanocomposite hydrogel precursor polymerization process,the glycerol-introduced nanocomposite hydrogel fibers（GN-Fibers）were prepared by“dynamic polymerization drawing”process inspired from spider silk spinning.Among them,Oligo（ethylene glycol）methacrylate（OEGMA）and acrylamide（AM）were selected as comonomer.The results showed that the drawing process during the fabrication endowed GN-Fibers with aligned polymer-clay microdomains,resulting in enhanced tensile strength（9.76 MPa）,toughness(10.37 MJ·m^-3)and optical propagation properties(0.26 dB·cm^-1).Moreover,due to the strong hydrogen-bonding between glycerol and water,such GN-Fibers showed good antifreezing properties（-20°C）and long-term stability（>5 days）at room temperature or high temperature.In addition,stable,reliable,and repeatable GN-Fiber based strain sensors were assembled for quantitative detection of large strains（100%）,subtle human motions（finger bending）and pressure（0.02-25 k Pa）in real time through the strain-optical signal attenuation mechanism.Such tough and flexible GN-Fibers displayed a broad application prospect in the fields of wearable sensing or artificial intelligence.2.Design and construction of conductive gel fiber with heterogeneous network structure,as well as investigation of strain sensing and stability of liquid environment of such gel fibers.On the basis of the high strength nanocomposite hydrogel fibers,the hybrid hydrogel fibers with heterogeneous networks,conductivity,and stable strain sensing performance were prepared by constructing polyaniline conductive network inside the nanocomposite hydrogel matrix.The results showed that the hybrid hydrogel fiber has excellent tensile strength（7.21 MPa）and fracture toughness(17.2 MJ·m^-3)due to the abundant non-covalent intermolecular interactions and uniform distribution of flexible and rigid polymer chains after introduction of polyaniline networks.Moreover,the hybrid gel fibers had dual-channel of ion and electron,which made it have excellent conductivity(87.99 S·m^-1),extremely low electro-mechanical signal delay（4.5%）,strain sensing sensitivity（GF=2.85～17.89）,and accurate human motion sensing performance.In addition,the hybrid gel fibers were immune to interference from versatile environments,contributing to stable and sensitive monitoring of human motions under air or liquid conditions.Such hybrid gel fibers would function well as wearable and implantable sensors in the fields of health monitoring and human-machine interactions.3.Design and construction of bioinspired nanocomposite gel fiber with hierarchical helical structure,as well as investigation of its mechanical properties and applications.On the basis of the“dynamic polymerization drawing”process,N,N-dimethyl acrylamide（DMAA）monomer with hygroscopicity and elasticity was introduced into the precursor to fabricate high strength and hygroscopicity nanocomposite hydrogel fibers.Further inspired by widely existed hierarchical helical structure in nature（spider silk,morning glories,etc.）,hierarchical helical nanocomposite gel fiber bundles with high toughness,good damping capacity,and response properties were constructed by wet twisting and drying processes.The results showed that with the increase of twist degree from 0 TPM（twist per meter）to 450 TPM,the mechanical strength of single gel fiber increased from 19.46 MPa to 23.14 MPa,but the elongation decreased from 99.27%to47.25%.The optimal twist of double-stranded gel fiber was 250 TPM,which could achieve the maximum tensile strength of 19.12 MPa and the fracture toughness of 13.22 MJ·m^-3.The toughness of hierarchical helical nanocomposite gel fibers is greatly improved from 7.37 MJ·m^-3 of single gel fiber to 21.67 MJ·m^-3 of H-8（+）and 18.96 MJ·m^-3 of H-8（-）.In addition,the H-8（+）gel fiber performed excellent kinetic energy dissipation,damping capacity,and good hygroscopic actuating properties(output power density is 5.6×10^-8 W·kg^-1).Therefore,the hierarchical helical nanocomposite gel fibers showed potential applications in diverse fields,such as damping,elastic shape memory and water vapor actuators.更多还原