Formation Mechanism and its Control of Organic / Inorganic Network in Nanocomposite Gel

控制聚合物凝胶的网络结构不仅对了解聚合物凝胶的高性能的来源特别重要，而且对于设计更新类型的凝胶也是特别重要的。本课题对聚N-异丙基丙烯酰胺(PNIPA)和无机粘土(Hittorite)组成的纳米复合型水凝胶(NC Gel)进行了一系列的结构、力学和功能研究。(1)首次合成了不同粘土浓度的纳米凝胶(C&lt；Clay&gt；)，并通过粘度、透光率、X射线衍射率和力学性能的变化，研究了原位自由基聚合过程中形成独特的有机/无机网络结构的机理。然后，我们提出了独特的网络形成机理，包括粘土刷子颗粒的形成。此外，(2)我们发现NC凝胶的力学性能(模数和强度)可以在很大范围内变化，而不会牺牲超高的ELON…断裂时的磨损率更高(1000%)，这取决于C_&lt；粘土&>。特别是，研究发现，纳米凝胶具有极高的断裂能(最高可达常规化学交联水凝胶的3000倍)，经后续的拉伸处理后，其强度可达3 Mpa。此外，我们还发现了纳米凝胶的一些重要性质，如(3)在临界温度以上，纳米凝胶中出现了光学各向异性。(4)由于温度循环通过较低的临界溶液温度而导致PNIPA链从线团到球体转变而产生可逆力，(5)通过加入粘土纳米颗粒来完全控制从线团到球体的转变，(6)在冻干状态下形成具有三层结构的独特的多孔形貌，(7)NC凝胶表面的滑动摩擦行为，(8)包括植入和抗血栓形成等在内的生物相容性。较少

Control of the network structure of polymer gel is of particular importance not only in understanding of the origin of the advanced properties of the polymer gels, but also for designing even newer types of gels. In this project, we carried out a series of structural, mechanical and functional investigations for nanocomposite type hydrogel (NC gel) consisting of poly(N-isopropylacrylamide) (PNIPA) and inorganic clay (hectorite). (1) We firstly synthesized NC gels with various clay concentrations (C_<clay>), and studied the mechanism of forming unique organic / inorganic network structure during in-situ free-radical polymerization through changes in viscosity, optical transmittance, X-ray diffraction and mechanical properties. Then, we proposed the unique network formation mechanism, including the formation of clay-brush particles. Also, (2) we revealed that the mechanical properties (modulus and strength) of NC gels can be varied in a wide range, without sacrificing the ultra-high elon … More gation at break (1000%), depending on the C_<clay>. In particular, it was found that NC gels exhibit the extraordinarily high fracture energy (up to 3000 times that of conventional chemically-crosslinked hydrogel), and that the strength reached to 3 MPa by subsequent elongation treatment. Furthermore, we found a number of important properties of NC gels, such as (3) appearance of optical anisotropy in NC gels at above critical C_<clay>, (4) reversible force generation as a result of the coil-to-globule transition of PNIPA chains in response to cycling the temperature across the lower critical solution temperature, (5) total control of the coil-to-globule transition by incorporation of clay nano-particles, (6) the formation of unique porous morphologies with a three-layered structure in the freeze-dried state, (7) the characteristic sliding frictional behaviors with remarkable changes in the coefficient of friction at the surface of NC gels, (8) biocompatibility including implantation and antithrombogenicity, etc. Thus, many interesting and important characteristics of NC gels are clarified through this project. Less