【作者】 陈清；

【导师】 张利东；

【作者基本信息】 华东师范大学 ， 高分子化学与物理， 2022， 博士

【摘要】 凝胶管是一类具有中空管状结构的水凝胶,在仿生血管,仿生支架,仿生驱动,细胞负载等领域具有广阔的应用前景。目前有多种方法可以制备具有中空结构的凝胶管,但构筑的凝胶管存在维度受限、功能单一等问题。因此,开发一种简单且高效的方法来构筑多维度中空凝胶管,成为当前最大的挑战。本文提出了化学“一步法”制备多维度中空凝胶管的策略,该制备策略无需苛刻的条件和模具,通过水溶液中的化学反应即可实现薄膜到中空凝胶管的转变。论文重点研究了薄膜至多维度凝胶管的成管机制及其转化模型,并将该机制应用于其他材料体系,探究了化学“一步法”策略的普适性。此外,通过功能化修饰手段,制备了具有各向异性结构的中空水凝胶管驱动器;借助溶剂置换法制备了具有更优异的抗冻/耐热性能的凝胶管。现阶段工作简单介绍如下:（1）提出了硫酸铜-过氧化氢/三羟甲基氨基甲烷-盐酸（Cu SO₄-H₂O₂/Tris（hydroxymethyl）aminomethane-HCl,Tris-HCl）溶液反应体系,采用“一步法”将海藻酸钠（Sodium alginate,SA）薄膜转化成中空凝胶管。通过控制反应条件,实现了凝胶管管壁及管径的可控调节;对薄膜进行图案化刻蚀,构建了多支化凝胶管;借助分子扩散机制制备了立体的薄膜组装体,从而构建了三维（Three-dimensional,3D）凝胶管。这种无需特殊模具的制备方法,能构筑不同尺寸、多重维度的高分子凝胶中空结构,有利于拓宽中空结构在仿生领域的应用前景。（2）探究了海藻酸钠薄膜在Cu SO₄-H₂O₂/Tris-HCl溶液体系中转化为中空凝胶管的机理。其转化机制概述为:SA薄膜置于Cu SO₄-H₂O₂/Tris-HCl溶液体系中,薄膜外层首先接触溶液,其中SA分子的-COO^-与溶液中的Cu²⁺交联形成不溶的凝胶层,随着浸泡时间的延长,水分子扩散而使得薄膜内层溶胀,Cu²⁺逐步向薄膜内层扩散并发生交联,从而形成沿薄膜外层向内层交联度逐渐降低的梯度交联。体系中H₂O₂进入溶胀的薄膜内层后,可降解低交联度区域,而Cu²⁺催化H₂O₂分解产生的气体将进一步加速中空结构的形成。（3）基于化学“一步法”策略,制备了温敏中空凝胶管驱动器,研究了其响应动力学机制。首次制备了厚度梯度上含不同温敏成分的聚N-异丙基丙烯酰胺（Poly（N-isopropyl acrylamide）,PNIPAM）的双层薄膜。通过水相中化学“一步法”反应,成功制备了具有各向异性结构的中空水凝胶管。温度或盐浓度引发PNIPAM相变,可诱导凝胶管的不对称收缩,从而赋予凝胶管高度可控的动力学行为。通过对双层薄膜的图案化修饰,可制备具有更复杂结构的凝胶管驱动器。（4）探究了化学“一步法”策略制备水凝胶中空管的普适性。以Ca²⁺交联SA薄膜转化为中空凝胶管为研究对象,成功将上述Cu SO₄-H₂O₂/Tris-HCl溶液体系拓展至Ca CO₃/Na HCO₃/Ca Cl₂/HCl溶液成管体系,大大拓宽了水体系中薄膜经化学反应转化为中空凝胶管的适用性。同时,通过丙三醇溶剂和聚乙二醇溶剂置换,显著提高了凝胶管在低温/高温环境下的抗冻/耐热性能,使其在-70-120℃温度范围内保持较好的管状结构与机械性能,拓宽了应用前景。更多还原

【Abstract】 The hydrogel tubes mean a kind of hydrogel with special hollow structures,which can be applicated in various fields,including artificial blood vessels,bionic scaffolds and cell adhesion devices.Various methods have been reported for the preparation of hydrogel hollow tubes,but most approaches have limitations to prepare with one-dimensional tubes.Thus,developing a facile and efficient method to achieving multi-dimensional hollow hydrogel tubes is still a challenge.In this paper,a chemical“one-step”project about the synthesis of multi-dimensional hollow hydrogel tubes in aqueous solution is reported.This simple and effective method is capable of preparing multi-dimensional hollow hydrogel tubes without requiring special conditions or molds.Molecular modification on the hydrogel tubes allows to give rise to tubular actuators that can enable controlled shape deformation owing to the anisotropic structures.Such the chemical“one-step”protocol can be further expanded to other systems to prepare performance-optimal hydrogel tubes.The molecular exchange with glycerin enables hydrogel tubes to have more promising performance for application in a wide temperature range from-70-120°C.Herein,The project is briefly described as follows.（1）The paper reports a new method for rapid conversion of sodium alginate（SA）films to multibranched hollow hydrogel tubes in‘‘one-pot’’reaction of buffered aqueous solution containing Cu SO₄,H₂O₂ and Tris-HCl elements.This method allows tunable the dimensions and thicknesses of the tube by changing reaction conditions accurately.The highly branched hollow tubes with various geometries could be prepared by directly cutting from the dried SA film.The three-dimensional（3D）hollow tubes are chemically prepared by the SA film of the 3D structure which is formed by molecular diffusion.This protocol requiring no special reaction conditions or molds endows facile fabrication of hollow structures with arbitrary sizes and dimensions of hydrogel or other materials,which may greatly expand the application fields of hollow hydrogels.（2）This chapter,for the first time,gives insights into the evolutionary mechanism of solid-to-hollow hydrogel in Cu SO₄-H₂O₂/Tris-HCl aqueous solution systems.The formation mechanism of the hollow tube is as follows:Firstly,when the film is immersed in aqueous solution containing Cu SO₄-H₂O₂/Tris-HCl elements,the Cu²⁺-induced crosslinking reaction with carboxyl groups（-COO^-）led to the gelatinization of the outer layer of the film,while the molecules in the film’s inner cavity are highly swelling.With the increasing of reaction time,the crosslinking reaction proceeded from the surface to inner core gradually to give a hydrogel material with crosslinking degree gradient across the section.Finally,the less-crosslinked inner core is degradable in the presence of H₂O₂ and abundant gas bubbles,that given a hollow structure hydrogel tube.（3）Based on the chemical“one-step”protocol,temperature-sensitive hollow hydrogel tube actuators are prepared and its kinetic mechanism is studied.The chapter firstly reports an anisotropic hollow hydrogel tube that is prepared from the bilayer film formed with the gradient distribution of the NIPAM element along the thickness direction by the chemical“one-step”reaction in an aqueous solution.The composite hydrogel tube induced shape-programmed deformation according to the asymmetric expansion or contraction of PNIPAM induced by the phase transition at diverse temperature and salt concentration.Through the patterned modification of the bilayer film,actuators with more complex structure are further prepared.（4）The study is universal for the synthesis of hollow hydrogel tubes in aqueous solution by chemical“one-step”protocol.Based on the crosslinking reaction between Ca²⁺and-COO^-in SA,we achieved hollow structure hydrogel tubes in the reaction system containing Ca CO₃,Na HCO₃,Ca Cl₂ and HCl elements,which broadened the universality of the protocol converting film into hollow tubes by chemical reaction in aqueous solution systems.Meanwhile,the hydrogel tubes could be functionalized by a solvent replacement method introducing glycerol and polyethylene glycol,which enables the tubes to keep flexibility and hollow structures from-70-120°C.The new method for the preparation of the antifreeze-resistance and heat-resistance of hollow hydrogel tubes that may greatly expand the applications in various extreme temperature environments in biomedical fields.更多还原