【作者】 杨晨；

【导师】 施晓文；

【作者基本信息】 武汉大学 ， 环境科学， 2023， 博士

【摘要】 壳聚糖是甲壳素经脱乙酰化处理后的产物,其在自然界中储量丰富、天然可再生。合理利用大量甲壳类动物和软体动物废弃物中的甲壳素资源,将其转化为高附加值产品,对可再生资源替代化石资源、缓解全球能源危机和解决环境污染问题具有重要意义。水凝胶具有与生物组织相似的软湿特性并且具有良好的生物相容性和柔性,采用水凝胶材料作为信息存储介质并调控其超分子结构,能实现信息的高效存储并响应外界刺激,这对于发展类生物组织的智能凝胶材料意义重大。目前水凝胶信息存储已取得了诸多研究进展,开发壳聚糖基水凝胶信息存储介质,有利于拓展废弃生物质资源的高值化利用途径。传统的信息存储介质大多为干态的硬质材料,其平衡体系中存储的静态信息无法响应外界刺激,而生物体的信息储存和分析为动态的非平衡过程,且信息存储在软湿介质中。壳聚糖作为一种天然高分子聚合物,其分子链上含有大量的活性基团（羟基、乙酰氨基和氨基）,通过物理、化学、生物等方法对其进行改性,可获得多功能的壳聚糖基材料。电化学交联是一种新兴的壳聚糖改性方式,与通常采用的传统化学交联方式相比,具有稳定、精确、可控、反应条件温和、能耗低以及环境友好等优势。本论文采用电化学方法,通过电信号诱导壳聚糖水凝胶的交联反应,实现了对水凝胶结构和性能的精确调控。此外,本论文充分利用电信号的可编程性及水凝胶的扩散性,构建了智能响应的壳聚糖基信息存储介质,实现了从2D到3D信息的精确存储和读取。主要研究内容及结论如下:（1）研究了电化学方法诱导壳聚糖和环氧氯丙烷共价交联的机理,并对共价交联壳聚糖水凝胶进行表征。通过循环伏安法（CV）探究了环氧氯丙烷（ECH）的电化学开环过程,结果表明,电化学方法诱导环氧氯丙烷的开环反应中不存在与电极的直接电子转移,ECH的电化学开环是亲核反应。电流密度越大,ECH开环越快,随着电化学反应的进行,ECH开环趋于平衡。通过AFM、FT-IR、¹³C NMR、XPS、偏光显微镜、SAXS测试及溶胀实验等对共价交联壳聚糖水凝胶进行了表征,结果表明,电化学交联过程中,电场作用使环氧氯丙烷交联壳聚糖链在电极表面平行排列,形成各向异性的结构,而且电化学方法制备的壳聚糖和环氧氯丙烷共价交联水凝胶的性质（交联密度、厚度、形貌等）可通过电信号调控。（2）研究了电化学交联壳聚糖凝胶的性质,及其在眼科治疗中的应用潜力。结果表明,可以简单地通过电极模板改变电沉积壳聚糖水凝胶的几何形状,且可通过电沉积诱导壳聚糖和环氧氯丙烷的共价交联进一步提高水凝胶透明度及力学性能,透光率从75%～89%提高到84%～96%,杨氏模量从0.82±0.04MPa提高到1.30±0.11 MPa。电沉积水凝胶的高含水率（>80%）使壳聚糖隐形眼镜具有良好的氧气透过率。电沉积水凝胶具有优良的光学性能、力学性能和生物相容性,其抗细菌粘附性能接近商用隐形眼镜,是水凝胶隐形眼镜的优良材料。（3）研究了阴极电书写对壳聚糖水凝胶共价交联区域的调控能力及其多维信息存储能力。通过电书写可实现对壳聚糖水凝胶上交联区域的精确调控,构建图案化共价交联的水凝胶。SEM、FT-IR、XRD、三维拉曼空间成像、溶胀测试等结果表明,水凝胶上书写区和非书写区的物理化学性质存在明显差异,可以通过三种不同的光学途径读取存储在壳聚糖水凝胶中的多维（2D/3D）结构信息,包括染料吸附、壳聚糖质子化和酸溶解。还可通过3D扫描建立三维模型,对三维结构信息进行精确读取。（4）研究了阳极/阴极电书写对壳聚糖水凝胶动态超分子网络的调控能力及可逆信息存储能力。通过SEM、TEM、FT-IR、XRD、EDS及显微拉曼光谱等手段对壳聚糖水凝胶超分子结构的变化进行了表征,结果表明,壳聚糖基动态响应信息存储介质可将电信号输入转换为水凝胶超分子结构响应,并可通过阳极和阴极对调,实现两种超分子结构（[（Chit）+（SDS）]和[（Chit-H⁺-SDS）]）的可逆转换。因此,电书写构建的图案化静电交联水凝胶上的2D及3D信息存储是可逆的,阳极书写的信息可被阴极擦除,并可通过阳极书写重新写入,以实现对信息的存储和更新。还可利用十二烷基硫酸钠（SDS）超分子结构的可逆转变,通过两种不同的方式（即模糊和消失）对信息进行隐藏和读取。（5）研究了阴极电书写对壳聚糖水凝胶上单、双交联区的调控能力及多维信息存储能力。通过电书写,可对同一壳聚糖水凝胶上的单交联和双交联区进行精确调控。拉力测试结果表明,所制备的单/双交联壳聚糖水凝胶的力学性能随交联图案和离子响应性的改变而改变。基于单/双交联水凝胶的离子响应性,还可设计具有良好形状记忆性能的仿生离子响应型水凝胶致动器,其弯曲角度可通过交联图案来调节。弯曲测试结果表明,水凝胶表面构建的褶皱结构可显著提高其抗疲劳性能。利用单/双交联水凝胶在酸性SDS溶液中透明度的变化和形变行为,实现了水凝胶中2D光学信息和3D形变信息的存储和读取。更多还原

【Abstract】 Chitosan is the product of deacetylation of chitin,which is abundant and renewable in nature.The rational utilization of chitin resources in a large amount of crustacean and mollusk wastes and its conversion into high value-added products is of great significance for replacing fossil resources with renewable resources,alleviating global energy crisis and solving environmental pollution problems.Hydrogels have soft and wet properties similar to biological tissues and have good biocompatibility and flexibility.Taking hydrogels as information storage media and regulating its supramolecular structure can realize efficient information storage and respond to external stimuli,which is of great significance for the development of intelligent hydrogel materials imitating biological tissues.At present,great progress has been made in hydrogel information storage.The development of chitosan-based hydrogel information storage media is conducive to expanding the high-value utilization of waste biomass resources.The traditional information storage media are mostly dry hard materials,and the static information stored in the equilibrium system cannot respond to external stimuli.While the information storage and analysis of organisms is a dynamic non-equilibrium process,and the information is stored in soft and wet media.Chitosan,as a natural polymer,contains a large number of active groups（hydroxyl group,acetyl group and amino group）on its molecular chain.It can be modified by physical,chemical and biological methods to obtain multi-functional chitosan based materials.Electrochemical crosslinking is a novel chitosan modification method.Compared with the traditional chemical crosslinking method,it has the advantages of stability,accuracy,controllability,mild reaction conditions,low energy consumption and environmental friendliness.In this paper,an electrochemical method was used to induce the crosslinking reaction of chitosan hydrogels by electrical signals,which realized the precise regulation of the structure and properties of hydrogels.In addition,this paper takes full advantage of the programmability of electrical signals and the dispersibility of hydrogels to construct the intelligent responsive chitosan-based information storage medium,and realizes the accurate storage and reading of information from 2D to 3D.The main research contents and conclusions are as follows:（1）The mechanism of covalent crosslinking of chitosan and epichlorohydrin induced by electrochemical method was studied and the covalent crosslinked chitosan hydrogels were characterized.Cyclic voltammetry（CV）was used to investigate the electrochemical ring-opening process of epiclorohydrin（ECH）.The results show that there is no direct electron transfer to the electrode in the ring-opening reaction of ECH induced by electrochemical method,and the electrochemical ring-opening of ECH is a nucleophilic reaction.And the higher the current density,the faster the ECH ring-opening.With the electrochemical reaction,the ECH ring-opening tends to be balanced.The covalent crosslinked chitosan hydrogels were characterized by AFM,FT-IR,¹³C NMR,XPS,polarizing microscope,SAXS and swelling experiment.The results show that during electrochemical crosslinking,the chitosan chains crosslinked with epichlorohydrin are arranged in parallel on the electrode surface by the action of electric field,forming a highly anisotropic structure.Moreover,the properties（crosslinking density,thickness,morphology,etc.）of chitosan and epichlorohydrin covalently crosslinked hydrogels prepared by electrochemical method can be regulated by electrical signals.（2）The properties of electrochemical crosslinked chitosan hydrogel and its potential application in ophthalmic treatment were studied.The results show that the geometry of electrodeposited chitosan hydrogel can be manipulated simply by electrode template,and the transparency and mechanical properties of hydrogel can be further improved by electrodeposition induced covalent crosslinking of chitosan and epichlorohydrin.Its transmittance increases from 75%～89%to 84%～96%,and Young’s modulus increases from 0.82±0.04 MPa to 1.30±0.11 MPa.The high water content of the electrodeposited hydrogel（>80%）gives chitosan contact lenses good oxygen permeability.Electrodeposited hydrogel has extraordinary optical properties,mechanical properties and biocompatibility,and its antibacterial adhesion is close to that of commercial contact lenses,making it a favourable material for hydrogel contact lenses.（3）The regulation of cathodic electrical writing on the covalent crosslinking region of chitosan hydrogel and its multidimensional information storage ability were studied.Electrical writing can be used to accurately regulate the crosslinking region of chitosan hydrogels and construct the patterned covalent crosslinking hydrogels.The results of SEM,FT-IR,XRD,3D Raman spatial imaging and swelling test show that physical and chemical properties of the written and unwritten regions on the hydrogels are significantly different.The multidimensional（2D/3D）structural information stored in the chitosan hydrogels can be read by three different optical accesses,including dye adsorption,chitosan protonation and acid dissolution.The 3D model can also be established by 3D scanning,and the 3D structural information can be accurately identified.（4）The regulation of the dynamic supramolecular network of chitosan hydrogel by anodic/cathodic electrical writing and its reversible information storage ability were studied.The supramolecular structure of chitosan hydrogels was characterized by SEM,TEM,FT-IR,XRD,EDS,micro-Raman spectroscopy and et al.The results show that the chitosan based dynamic response information storage medium can convert electrical signal input into hydrogel supramolecular structure response,and the two supramolecular structures（[（Chit）+（SDS）]and[（Chit-H⁺-SDS）]）can be reversed by anode and cathode switching.Therefore,2D and 3D information storage on the patterned electrostatic crosslinked hydrogel constructed by electrical writing is reversible.The information written by the anode can be erased by the cathode and rewritten by the anodic writing to realize the storage and update of information.The reversible transition of sodium dodecyl sulfate（SDS）supramolecular structure can also be used to conceal and reveal information in two different ways,namely obscure and evanescence.（5）The regulation of single and double crosslinking regions on chitosan hydrogels by cathodic electrical writing and its multidimensional information storage ability were studied.The single and double crosslinking regions on the same chitosan hydrogel can be precisely regulated by electrical writing.The tensile test results show that the mechanical properties of single/double crosslinking chitosan hydrogel change with the crosslinking pattern and ionic responsiveness.Based on the ionic responsiveness of single/double crosslinking hydrogel,a bionic ion-responsive hydrogel actuator with good shape memory performance can be designed.Its bending angle can be manipulated by the crosslinking pattern.And the bending test results show that the wrinkled structure constructed on the surface of the hydrogel can significantly improve its fatigue resistance.The 2D optical information and 3D deformation information in hydrogels can be stored and read by the change of transparency and deformation behavior of single/double crosslinking hydrogels in acidic SDS solution.更多还原