聚合物/无机纳米复合材料中界面层性质梯度变化规律及其影响因素研究

The interface between the polymer matrix and inorganic particles in the polymer/inorganic nanocomposites is one of key issues determing the properties of the nanocomposites, and the study on this issue have been attracting the significant attentions from both industrial and scientific communities for decades. However, the size of the interface between the nanoparticle and the polymer matrix is extremely small, which make it difficult to be characterized and investigated. To solve this problem,we propose using the system containing a polymer thin film and a substrate in which the polymer thin film and substrate are used to mimic the polymer matrix and nanoparticle surface, respectively, as a model. For this system, the surface properties,such as glass transition temperature and physical aging of the polymer thin films with different thickness will be characterized by Sum Frequency Generation Spectroscopy（SFG）, from which the property gradient profile of the polymer thin film caused by the substrate surface can be obtained. Associating these gradient profiles with the dispersion state and corresponding properties of the counterpart nanocomposites. The relationship between the polymer thin film and the interface in nanocomposites will be investigated, so the gradient profiles of the interfacial properties in nanocomposite can be achieved. In addition, an association model between interfacial properties and the entire properties of the nanocomposites can also be established. The study of this proposed project will supply a new methodology to investigate the interaction between polymer matrix and inorganic suface, and moreover, a further insight into the reinforment of inorganic nanoparticles on polymer and its mechanism can be achieved. Therefore, this project has some scientific values and can provide some theoretical guide and experimental basis for the nanoparticle surface modification and the preparation, structure design, and property tuning of polymer/inorganic nanocomposites.

聚合物/无机纳米复合材料中界面层性质是决定材料性能的关键因素之一，对其研究一直是材料科学界的热点和难点。针对聚合物/无机纳米复合材料中界面层尺寸微小，结构和性能表征困难等问题，本项目提出以聚合物/无机基材纳米支持膜体系为模型（聚合物薄膜模拟界面层聚合物，无机基材模拟纳米粒子）,采用和频共振光谱表征不同厚度聚合物薄膜的表面性质（如玻璃化转变温度、玻璃态物理老化等），考察聚合物薄膜性质在无机基材作用下梯度变化规律；将聚合物薄膜性质的梯度变化规律与纳米复合材料的分散状态及相关性质相关联，研究聚合物薄膜与纳米复合材料中界面层在某些性质上的相关性，实现界面层性质梯度变化规律的研究，同时建立界面层性质与纳米复合材料宏观性质关联模型。本项目的研究将提供一种深入研究纳米复合材料中界面层性质的方法，揭示无机纳米粒子的补强作用机理，为无机纳米粒子表面改性以及纳米复合材料结构与性能调控提供理论指导及实验依据。

深入了解聚合物/无机纳米复合材料中界面层的性质对纳米复合材料的设计、制备和性能优化具有重要的科学意义。本项目通过旋转涂膜和表面引发活性聚合在不同基材表面构建了纳米支持膜和聚合物刷两种界面层，利用和频共振光谱（SFG）、纳米金颗粒沉降、纳米孔洞愈合等方法对界面层玻璃化转变温度（Tg）、模量等性质及其梯度变化进行了表征，建立了梯度变化方程，揭示了聚合物与基材之间的相互作用对界面层性质的影响规律。研究发现，当存在强相互作用（氢键、π-π）时，界面层Tg和模量均高于本体聚合物的Tg和模量，且界面处最高，沿厚度方向呈梯度变化；当界面相互作用弱甚至相斥时，界面层Tg和模量低于本体聚合物，也呈梯度变化，表面改性能改善界面相互作用，提高界面层性质。此外，不同界面相互作用的作用范围也不同。对于聚合物刷界面层，其一端固定，一端自由的结构使其性质的梯度变化更加明显。对于界面层梯度变化规律的应用：1）与复合材料性质进行关联，实现了某些性质的预测模型；2）制备了泡孔结构梯度变化的薄膜微孔发泡材料；3）采用含有离子液体链段的梳状、嵌段共聚物为相容剂制备了聚苯乙烯/石墨烯纳米复合材料，利用离子液体嵌段中的咪唑盐结构与石墨烯的π-π、π-阳离子相互作用实现界面层性质以及复合材料Tg的调控。此外，围绕SFG技术，项目对聚合物刷的水合性质、构象等界面层性质进行了研究，揭示了亲水性聚合物刷抗生物污染的机理和关键因素，并在此基础上开发了一种具有反聚电解质效应的聚合物刷体系，建立了链段构象与界面摩擦、蛋白质吸附/脱附等界面性质之间的关系。本项目验证了利用基材表面界面层作为模型研究纳米复合材料中界面层性质的可行性，建立了界面层Tg和模量及其梯度变化规律的测定方法，实现了界面层性质与纳米复合材料性能的关联，为高性能聚合物无机纳米复合材料界面层调控提供了理论指导和实验基础。