多重刺激响应自愈性纳米复合智能水凝胶的流变学与电学性能研究

Graphene and its derivatives graphene oxide (GO) and reduced graphene oxide (RGO) offer exciting possibilities for new applications in Soft Matter science. Due to the large surface of nanosheet-like materials (e.g. GO), small amounts of nanofillers have a significant effect on properties. Tailoring the unusual rheological properties of polymers-graphene composite hydrogels in combination with optimizing the electric and dielectric behavior will lead to a class of materials, which can be used for various applications from sensors to actuators to controlled drug delivery. .The aim of the project is to synthesize copolymers of NIPAM and catechol derivatives in the presence of GO or RGO. A key point of the project is the synthesis of 3-hydroxy-4-pyridinone methacrylamine (HOPOMA), which promises a higher stability against oxidation in comparison to the dopamine methacrylamide (DMA), which will be used as the standard catecholic comonomer. The resulting polymer solutions or gels (depending on concentration of polymer and nanofiller) can be supramolecularly crosslinked by addition of a base and suitable multivalent cations. The homogeneity of nanofiller dispersion (to prevent agglomeration), grafted polymer chains on the surface acting as a soft spacer will be employed which will be achieved, when synthesizing the polymer in situ, i.e. in the presence of GO/RGO. The resulting systems will be characterized by a combination of GPC, NMR,FTIR, and so on. Rheological and electrical properties are the key techniques used in this project, thus, allowing for a deep insight into the structure of the materials. The rheological and electrical properties will be determined at the same time using a rheometer with the possibility to measure the dielectric properties online. This allows for determining exactly how a deformation pulse disturbs the structure by checking damage to and recovery of electrical and rheological properties in parallel..When having gained a good understanding of interactions between functional groups in polymers making covalent or supramolecular bonds with carbon based fillers, the findings shall be used for determining design rules for effective use of carbon nanofillers in polymer solutions and gels. When being able to tailor mechanical and electrical properties, it is possible to use these developed gels for actuator applications. This outlook for potential applications as well as the importance for the basic understanding of electrical and rheological properties in parallel on hydrogel systems makes the proposal very important for the future of soft matter science and engineering..The complete research chain from comonomer and nanofiller synthesis to polymer gel production to a complete characterization by members of the research team allows for maximum flexibility of the composition of the systems used.

本课题将在含有GO/RGO的溶液中合成基于多巴胺（DMA）或3-羟基-4吡啶酮甲基丙烯酰胺（HOPOMA）与N-异丙基酰胺（NIPAM）的无规共聚物；通过添加适当的多价离子，制备兼具pH值、温度、离子多重刺激响应性和快速形变自愈性的石墨烯复合智能超分子水凝胶/溶液。研究反应条件对复合材料中聚合物含量的影响，实现对材料组分结构的可控性。探索流变性能与电性能、形态变化的实时同步测试方法；研究复合材料中聚合物基体与碳材料之间、各分子链之间存在相互作用力对材料性能的影响；研究材料形变量对其结构破坏程度以及材料流变性能与电性能的自愈能力的影响。本课题的工作将为我们今后提升碳基填料在复合材料中的效用、设计新结构的聚合物水凝胶/溶液智能材料提供重要理论基础；并通过实现对水凝胶智能材料力学性能和电性能的可调控性，推动智能水凝胶在传动器方面的应用，拓宽水凝胶在软材料科学与工程领域的发展前景。

由于N-异丙基丙烯酰胺多巴胺（DMA）共聚物（NIDO）的理化性质和流动性特征一直是关注重点，首先合成N-异丙基丙烯酰胺多巴胺（DMA）共聚物（NIDO），并对其进行特征描述。由于端基和多巴胺的疏水性质，该共聚物的热性质不仅与多巴胺含量有关，还与该共聚物分子量有关。该共聚物在强氧化剂的存在下，通过氢键键合在非质子溶剂中超分子连接，在水溶液中形成共价凝胶，这也显著影响自修复性能。而且，如果还原的氧化石墨烯（RGO）在体系中，则该共聚物形成更强的凝胶，但是，它更脆。此外，还发现含硼聚合物离子与该共聚物结合可产生比该共聚物与一般硼离子结合更强的凝胶。同时，与N-异丙基丙烯酰胺多巴胺（DMA）共聚物（NIDO）结合的一般阳离子类型决定了凝胶的强度。合成了水溶性较差的NIPAM与HOPOMA的功能性共聚物，并对其进行了如下改性：用亲水性更强的共聚单体NEAM补偿HOPOMA的疏水性，制备了一系列NIPAM-NEAM共聚物，并对其热性能进行了详细研究。为了更好地理解网络结构，建立了一个中尺度网络仿真模型，随机生成功能高分子网络，并从网络连通性和非连通网络孤岛的角度对其进行分析。这些结构还具有“空间分辨流变学”的特征——机械AFM测量，这使我们能够证明，不含填料的超分子凝胶不包含AFM可观察到的任何结构，从而使凝胶足够均匀，可以按原样使用开发的网络模型，而对于在cononsolvency条件下合成的凝胶（在SEM下干燥状态下具有明显的多孔性）结构是可见的，这解释了它们与普通凝胶相比明显的改性行为。这让我们能够证明NIDO凝胶的均匀性。在相关侧线上，还对聚合物熔体的热流变复杂性和非线性（非线性）大振幅振荡剪切进行了测试，并将其与超分子凝胶进行了比较，例如，研究在聚合物熔体中使用石墨填料与在超分子聚合物凝胶中使用石墨填料之间的行为差异。此外，还研究了海藻酸钠（一种天然的离子吸附聚合物）和NIDO在与含硼聚合物NIBA相互作用方面的流变行为差异。