核能的可持续发展对于我国“双碳”减排目标具有重要意义。由于陆地铀资源的可用储量有限，研究海水提铀这一非常规铀资源开发途径具有重要意义。基于偕胺肟聚合物（PAO）材料进行海水中铀的吸附分离，被认为是最有前景的海水提铀方法。然而，由于对介观尺度上聚合物链段构象与其吸附行为的关系缺乏系统研究，无法有效调控并优化铀酰离子传质及络合过程，导致现有报道的PAO吸附材料官能团利用率极低，吸附容量亟待提升。为此，本论文立足于高分子溶液物理理论与经典吸附模型推导出聚合物链段构象与其吸附性能之间的定量构效关系式，并将多尺度模拟与光控自由基聚合方法相耦合，建立了一种海水提铀聚合物材料优化设计与可控合成的一体化方案。本论文的创新性成果包括：第一，将高分子溶液物理理论与经典Langmuir吸附模型结合，论证了介观尺度下聚合物链段空间构象对其吸附行为的显著影响，并推导出吸附量与聚合物链段均方旋转半径之间的定量幂律关系式。第二，基于耗散粒子动力学（DPD）与分子动力学（MD）建立了一种多尺度计算机模拟研究聚合物吸附行为及构效关系的方法，实现了对偕胺肟嵌段共聚物（BCP）的动态链段构象与对铀酰离子吸附过程的模拟，并预测了可获得最佳吸附性能的材料组成。第三，建立了一种可控合成聚丙烯腈及其嵌段聚合物、且具备耐氧性的光致能量转移-可逆加成断裂链转移（PET-RAFT）聚合方法，精确合成出计算机模拟设计的偕胺肟嵌段共聚物前驱体。第四，基于高分子亚浓溶液理论推导出了聚合物纺丝可加工性的半经验公式，实现了对不同组成嵌段共聚物的静电纺丝，制备出形貌规整、尺寸均匀的纳米纤维膜吸附材料。第五，吸附实验证实了设计合成的材料表现出与DPD模拟完全一致的铀吸附行为，并在28天真实海水提铀测试中获得了11.4±1.2 mg/g的高吸附容量。本论文的研究为聚合物吸附金属离子提供了一个新的研究视角，以介观尺度上链段的空间构象特性为桥梁，衔接了分子水平上特定金属-配体络合相互作用与宏观尺度上材料的吸附性能。所建立多尺度计算机模拟耦合光控自由基聚合的研究范式可适用于更多功能导向的新型聚合物材料的设计及可控合成。
The sustainable development of nuclear energy acts as a significant role in achieving carbon peaking and carbon neutrality goals. Due to the limited availability of terrestrial uranium resources, it is highly valued to research the exploitation of unconventional uranium resources by harvesting uranium from seawater. The separation of uranium from seawater by using amidoxime (AO) functionalized polymer adsorbents, is recognized as the most promising method for uranium extraction from seawater. However, due to the lack of systematic research on the relationship between the polymer conformation and the adsorption behavior of the polymer adsorbents at the mesoscopic level, it has been unachievable to regulate while optimizing the mass transfer and coordination behaviors of uranyl ions in the adsorption process. This resulted in the extremely low utilization of AO ligands in the reported PAO adsorbents, leaving significant room to raise the adsorption capacity. To this end, this dissertation derived the mathematical relationship between the adsorption performance and chain conformations of polymer adsorbents based on the polymer solution theory and solid-liquid adsorption model. By integrating multi-scale computational simulation with photo-controlled macromolecular synthesis, this dissertation presented a new paradigm for smart design and controlled synthesis of polymeric adsorbents for uranium harvesting from seawater. Innovative achievements of this dissertation are summarized as follow:Firstly, the significant influence of spatial conformation of polymers on their adsorption behaviors was demonstrated through the combination of polymer solution physical theory and the classical Langmuir adsorption model, and a quantitative scaling relationship between the adsorption capacity and the mean-square radius of gyration (Rg) was derived. Secondly, a dissipative particle dynamics (DPD) approach, combined with a molecular dynamics (MD) study, was performed to simulate the conformational dynamics and the adsorption process of amidoxime functionalized block copolymer (BCP), and the chain structure of the BCP adsorption with the maximum adsorption capacity was achieved. Thirdly, a photo-induced energy transfer-reversible addition-fragmentation chain transfer (PET-RAFT) polymerization method for the synthesized of polyacrylonitrile (PAN) was established. This polymerization method owns oxygen tolerance and the computer-designed BCP precursors were then synthesized precisely. Fourthly, a semi-empirical equation for the spinnability of BCP solutions was derived according to the semi-dilute polymer solution theory, and the synthesized BCPs with different block ratios were fabricated into uniform nanofiber membranes (ENMs) by electro-spinning. Fifthly, the BCP adsorbents exhibited predicted uranium adsorption behaviors in conformity with the DPD simulation. Specifically, a record high adsorption capacity of uranium (11.4±1.2 mg/g) in real seawater was achieved within 28 days.This study offers a new research perspective to study the adsorption of metal ions by polymers, bridging the specific metal-ligand interactions at the molecular level and their adsorption properties at the macroscopic level with the spatial conformational properties at the mesoscopic level. The established protocol integrating multi-scale modeling with photo-controlled radical polymerization is generally adaptable for target-oriented design and controlled synthesis of more advanced polymers materials.
