新型智能窗用纳米二氧化钒/PNIPAm复合微凝胶的协同相变研究

In order to overcome the shortage of smart windows using vanadium dioxide (VO2) or poly(N-isopropyl acrylamide) (PNIPAm) microgel alone, novel VO2/PNIPAm composite microgels with uniform size and dispersion stability which is beneficial to the synergistic phase transition between VO2 nanoparticles and PNIPAm microgels, will be prepared through careful design. In scheme one, nano-sized VO2/PNIPAm composite microgels with “York-shell” structure will be prepared by micro-emulsion polymerization and photo-emulsion polymerization. In scheme two, slightly crosslinked PNIPAm brushes will be prepared by atom transfer radical polymerization (ATRP) on the surface of a single VO2 nanoparticle. The rules of phase transistion of inorganic VO2 nanoparticles and organic PNIPAm microgels as well as the VO2/PNIPAm composite microgels will be studied by small angle and wide angle X-ray scattering device in Shanghai Synchrotron Radiation Facility. Based on the results, the phase transition temperature of VO2 will be tuned by doping, and the lower critical solution temperature (LCST) of PNIPAm microgels will be shifed by copolymeriation or changing the solvent composition. The target is to move the phase transition temperature of VO2/PNIPAm composite microgels close to the room temperature where people feel comfortable, to realize the synergistic phase transition between VO2 nanoparticles and PNIPAm microgels, to improve both the solar energy regulation efficiency Tsol and the visible light transmittance Tlum while keeping good optical properties, and to lay the foundation for the development of a new generation of high-performance smart window materials.

本项目针对单独采用无机二氧化钒（VO2）或有机聚N-异丙基丙烯酰胺（PNIPAm）水凝胶作为智能窗材料的不足，精心设计并制备大小均匀、分散稳定并有利于二者产生协同相变的纳米复合微凝胶。方案一采用微乳液聚合和光乳液聚合制备以多个VO2粒子为核的“蛋黄-壳”型复合微凝胶；方案二采用原子转移自由基聚合在单个VO2粒子表面原位生长微交联的球形PNIPAm刷，制备“核-壳”结构的纳米复合微凝胶。利用上海光源同步辐射中心小角/广角X射线散射等手段，系统研究复合微凝胶中VO2纳米粒子和PNIPAm微凝胶随温度变化的相变规律，通过掺杂调节VO2相变温度，利用共聚或改变溶剂组成控制PNIPAm微凝胶的低临界溶解温度（LCST），使二者均接近室温，实现无机VO2和有机PNIPAm凝胶的协同相变，从而达到同时提高太阳能调节效率和可见光透过率，并且保持良好光学性质的目的，为开发新一代高效智能窗奠定基础。

以聚（N-异丙基丙烯酰胺）等温敏性聚合物形成的水凝胶材料，除能应用于生物医药、柔性电子驱动、传感器等领域外，在智能窗领域也有巨大的应用前景。为了克服单独采用聚合物水凝胶制备的智能窗系统调光性能不足的问题，本项目通过引入无机二氧化钒等具有优异热致相变功能性纳米粒子，制备了多种具有优异调光性能的复合热致变色智能窗系统。.本项目利用聚（N-异丙基丙烯酰胺）、聚丙烯酸等高分子水凝胶材料自组装特性，通过与无机二氧化钒（VO2）等纳米粒子复合，制备了不同热致变色类型水凝胶体系，其相变和调光性能能够满足智能窗对隐私、保温、绿色、节能等方面的要求，为开发新一代高效智能窗材料奠定了基础。我们利用最低临界共溶温度（LCST）型和最高临界共溶温度（UCST）型热致变色水凝胶透光率在升温过程中呈现相反转变特性，建立了光-热信号转换器件，同时利用小角X射线散射、动态光散射、紫外光谱等多种仪器详细分析了不同类型热致变色水凝胶相变机理。项目还开发了绿色环保淀粉基热致变色水凝胶，将其与纳米VO2复合后封装入带有透明导热电极智能窗框中，解决了热致变色智能窗响应性差问题，实现材料相变的自主调节，制得复合型聚合物热致变色水凝胶智能窗系统。此外，以光-热信号转换器件构建为目标，通过在聚丙烯酸溶液中原位生成无定形碳酸钙纳米粒子，制备了具有不同热致变色性能聚丙烯酸/无定形碳酸钙水凝胶，系统研究了该可调相变类型形成机制及其在光热信号转换及智能窗领域的应用。.通过本项目的研究，共发表标注项目资助的SCI收录论文32篇，国内核心期刊2篇。