Rheology of Polymer Melts with Designed Hairy Nanoparticles

许多基本产品，如玻璃、纸、塑料和橡胶，都是由聚合物制成的。聚合物由于其多功能性、低成本和可加工性而具有很高的吸引力，但其功能是有限的。为了提高聚合物的功能和强度，建议加入纳米颗粒。然而，大多数纳米颗粒往往与聚合物基体不相容，导致团聚和力学性能恶化。为了控制纳米颗粒在聚合物基体中的分散，提出了在纳米颗粒表面化学接枝聚合物，即毛状纳米颗粒。该奖项旨在了解毛状纳米颗粒如何影响聚合物的功能和特性。通过在不同形状的纳米颗粒上控制接枝聚合物链的长度、密度和化学性质，该研究可以影响聚合物的制造、加工和许多工程应用。拟议的研究还伴随着一系列教育和推广工作，如让本科生研究人员参与，为教师提供教育计划，发布开源代码，以扩大其影响。含有毛状纳米颗粒的聚合物基质的流变性不能用已知的理论来解释，例如爱因斯坦的理论或巴学士的理论，这些理论低估了相对粘度超过1000万倍。因此，该奖项的目的是：(1)通过实验研究不同形状的毛状纳米颗粒的纳米复合材料的流变性；(2)开发并验证模拟此类悬架的计算工具；(3)研究其偏离理论的主要原因，从而为改进理论/简化模型以满足先进制造的需求铺平道路。本研究拟制备由不同链长和接枝密度的聚甲基丙烯酸甲酯或其他可混相分子接枝的设计的0D、1D和2D纳米颗粒，用于分散在聚甲基丙烯酸甲酯基质中。粒子解析模拟将通过使用锐利界面浸入边界方法处理移动粒子来执行，该方法能够模拟任意形状的粒子与流体的相互作用。颗粒上的毛状接枝将被模拟为实验得出的相互作用区内的多孔介质。模拟和实验将提供足够的相关性来测试几何参数对流变学影响的几个假设，从而使基于这些参数的经验公式得以发展。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Many essential products, e.g., glass, paper, plastics, and rubbers, are made of polymers. Polymers are highly attractive due to their versatility, low-cost and processability, but their functionality is limited. To enhance the functionality and strength of polymers, it is proposed to incorporate nanoparticles. However, most nanoparticles are often incompatible with polymer matrices, resulting in agglomeration and deterioration in mechanical properties. To control the dispersion of nanoparticles in polymer matrices, chemically grafted polymers on the surface of nanoparticles, known as hairy nanoparticles, is proposed. This award seeks to understand how hairy nanoparticles affect the functionality and properties of the polymers. By controlling the grafted polymer chain length, density, and chemical nature on well-dispersed nanoparticles of different shapes, the research can impact how polymers are manufactured, processed, and utilized for many engineering applications. The proposed research is accompanied by a series of educational and outreach efforts such as involving undergraduate researchers, educational programs for teachers, and releasing open-source codes, to broaden its impact. The rheology of polymer matrices containing hairy nanoparticles cannot be explained by known theories, e.g., Einstein’s or Bachelor’s, which underestimates the relative viscosity by over 10 million folds. The objective of this award, therefore, is to (1) experimentally investigate the rheology of nanocomposites with different shapes of hairy nanoparticles; (2) develop and validate computational tools to simulate such suspensions; and (3) investigate the main reasons for their deviation from the theory, thereby pave the way to improve theoretical/simplified models for advanced manufacturing needs. The proposed study intends to prepare designed 0D,1D, and 2D nanoparticles grafted by poly(methylmethacrylate) or other miscible molecules with different chain lengths and graft densities for dispersion in poly(methylmethacrylate) matrix. Particle-resolved simulations will be performed by handling the moving particles using a sharp-interface immersed boundary method, capable of simulating arbitrary-shaped particles interacting with the fluid. The hairy grafts on the particles will be modeled as a porous medium over the interaction zone derived from experiments. The simulations and experiments will provide sufficient correlation to test several hypotheses on the effect of geometric parameters on rheology, thereby enabling the development of empirical formulas based on these parameters.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.