Presidential Young Investigator Award

这项研究的目的是了解分子和微观结构动力学在决定聚合物的宏观材料性质方面的作用。在聚合物液体的情况下，他们正在结合实验和理论方法，以提高我们预测其流变性的能力。由于这些流体的复杂性质，为了获得适当的信息来检验理论，有必要观察多组分体系中单个组分的动力学，并遵循特定的松弛模式来响应宏观变形。为了获得这一水平的信息，这项研究将开发光谱和流变学相结合的方法来研究嵌段共聚物中的有序-无序转变、可混溶聚合物熔体的流变性以及刚性棒状聚合物液晶在流动中的取向有序性。分子运动在固体聚合物中也起着重要作用，其中一个方面是流动性的开始，这是可混溶聚合物共混物具有广泛玻璃化转变特征的原因。因此，将使用固态氘核磁共振来观察分子在共混物中每一组分中的运动速度作为玻璃化转变过程中温度的函数。这些观测将使我们对决定玻璃化转变温度和广度的因素有新的认识。

The goal of this research is to understand the role of molecular and microstructural dynamics in determing the macroscopic material properties of polymers. In the case of polymeric liquids, they are combining experimental and theoretical approaches in order to advance our ability to predict their rheological properties. Due to the complex nature of these fluids, and in order to obtain appropriate information to test theory, it is necessary to observe the dynamics of individual components in multicomponent systems and to follow specific modes of relaxation in response to macroscopic deformation. To access this level of information, this research will be developing combined spectroscopic and rheometric methods to study the order-disorder transition in block copolymers, the rheology of miscible polymer melts, and the orientational order of rigid-rod polymer liquid crystals under flow. Molecular motions play an important role in solid polymers as well, and one aspect is the onset of mobility that is responsible for the broad glass transition characteristic of miscible polymer blends. Therefore, will be used solid-state deuterium nuclear magnetic resonance to observe the rate of molecular motion in each component of the blend individually as a function of temperature through the glass transition. These observations will give new insight into the factors that determine the temperature and breadth of the glass transition.