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

1512297(阿彻)这项拟议研究的目标是研究所谓的软玻璃材料中的粒子动力学和弛豫。这些材料是用于添加剂制造、电池和燃料电池的流体以及药物配方的可打印功能油墨。这项研究的成功完成可能会导致制造具有特定工程应用特性的新型流体。建议开发一个通用框架，以了解堵塞悬浮液中的颗粒动力学(聚合物中的纳米颗粒)如何影响从扩散动力学到超扩散动力学的转变。最近关于软性眼镜终端松弛的报道发现，它们总是令人惊讶地过度扩散。事实上，超扩散弛豫现在被认为是软玻璃态的特征，反映了材料对内应力的不平衡反应，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多毛纳米颗粒组成的软玻璃，表现出一系列相互矛盾的特征：(I)它们被卡住，呈玻璃状；(Ii)它们表现出可接近的牛顿流动状态，并能够达到平衡；(Iii)它们几乎没有老化的迹象；(Iv)它们在长时间和长尺度上表现出超扩散弛豫。然而，有人认为，这种矛盾行为只是表面上的，系统的动力学可以揭示导致这些特征的根本行为。他们计划使用多毛纳米粒子作为模型系统，并进行一系列实验(光子相关光谱、小角X射线散射、机械流变学、介电松弛)和理论，以阐明软玻璃中超扩散弛豫的根本原因。这项工作令人兴奋的是，它追求的是软玻璃动力学的一般模型，即它似乎将有限时间尺度上进行的实验结果与软玻璃在延长时间尺度上的动力学联系起来。除了研究生教育，还制定了接触K-12学生和他们的老师的计划。

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.