UNS:Relaxation Dynamics of Particles and Polymers in Soft Glassy Suspensions

1512297（Archer）提议的研究目标是研究所谓软玻璃材料中的粒子动力学和弛豫。这些材料是用于增材制造的可打印功能油墨、用于电池和燃料电池的液体以及药物配方。这项研究的成功完成可能会导致制造出具有特定工程应用特性的新型流体。我们建议建立一个总体框架来理解堵塞悬浮液中的粒子动力学（聚合物中的纳米粒子）如何影响从扩散动力学到超扩散动力学的转变。最近关于软玻璃末端弛豫的报告发现，它们总是令人惊讶地呈超扩散。事实上，超扩散弛豫现在被认为是软玻璃态的一个特征，反映了材料对内应力的非平衡响应，内应力要么是在玻璃化转变时形成的，要么是由于各种原因而形成的。PI和他的团队最近发现了一类由毛状纳米颗粒组成的软玻璃，它们表现出一系列相互矛盾的特征：(1)它们被卡住了，呈玻璃状；（ii）它们表现出可接近的牛顿流态，并能够达到平衡；（iii）几乎没有老化的迹象；(4)它们在长长度和时间尺度上表现出超扩散弛豫。然而，有人认为，矛盾行为只是表面的，系统的动力学可以揭示导致这些特征的基本行为。他们计划使用毛状纳米颗粒作为模型系统，并进行一系列实验（光子相关光谱、小角度x射线散射、机械流变学、介电弛豫）和理论，以阐明软玻璃中超扩散弛豫的基本起源。这项工作令人兴奋的是，它追求软玻璃动力学的一般模型，也就是说，它看起来将在有限时间尺度上进行的实验结果与扩展时间尺度上的软玻璃动力学联系起来。除了研究生教育，还计划向K-12学生和他们的老师伸出援手。

1512297(Archer)The goal of the proposed research is to study particle dynamics and relaxation in so-called soft glassy materials. Such materials are printable functional inks for additive manufacturing, fluids for batteries and fuel cells, and pharmaceutical formulations. Successful completion of this study could lead to the manufacturing of new types of fluids with properties tailored to specific engineering applications.It is proposed to develop a general framework for understanding how particle dynamics in jammed suspensions (nanoparticles in polymers) impact the transition from diffusive to hyperdiffusive dynamics. Recent reports on terminal relaxations in soft glasses have found that they are invariably and surprisingly hyperdiffusive. Hyperdiffusive relaxations are in fact now thought to be a characteristic of the soft glassy state and to reflect a material's out-of-equilibrium response to internal stresses, which are either built in at the glass transition or build up due to a variety of reasons. The PI and his group have recently discovered a class of soft glasses comprised of hairy nanoparticles that manifest a series of contradictory traits: (i) they are jammed and glassy; (ii) they manifest an accessible Newtonian flow regime and are able to reach equilibrium; (iii) they show little signs of aging; and (iv) they exhibit hyperdiffusive relaxations on long length and time scales. However, it is argued that the contradictory behavior is only superficial, and the dynamics of the system can reveal the fundamental behavior leading to these traits. They plan to use hairy nanoparticles as model systems, and a battery of experiments (photon correlation spectroscopies, small-angle X-ray scattering, mechanical rheometry, dielectric relaxation) and theory to shed light on the fundamental origins of hyperdiffusive relaxations in soft glasses. What makes this work exciting is that it goes after general models for dynamics of soft glasses, i.e., it looks to relate findings from experiments performed on limited time scales to dynamics in soft glasses on extended timescales. In addition to graduate education, plans to reach out to K-12 students and their teachers are laid out.