Molecular Dynamics, Structure, and Phase Transitions in Liquid-Crystalline Media: Electron-Spin Resonance (ESR) Studies

用现代电子自旋共振(ESR)技术研究液晶的动态分子结构。计划对分子重定向运动进行进一步的研究，包括局部和远程协作性。利用观察到的自旋松弛的临界发散类型，在分子水平上研究液晶相变的动力学将继续进行。这些研究是用不同大小和形状的自旋探针进行的。新的二维傅里叶变换ESR方法将被用来获得更准确和更详细的驰豫数据，从中推断分子的长时间和短时间运动。二维电子自旋回波和新的高场ESR方法将使人们能够从有序、构型和动力学的角度研究较大的探测器在较低温度阶段的慢运动行为。通过在分子水平(通过自旋交换)和在宏观水平(通过ESR成像)研究探针的平移扩散，将加强对液晶中分子运动的描述。特别强调解释向列相-近晶相变和近晶相内的分子转动和平移耦合运动的结果，我们强大的计算方法将允许对运动动力学进行更复杂的建模，以解释这些结果。这些研究将包括热致性、定向溶致向列型和定向聚合物液晶。

Studies on the dynamic molecular structure of liquid crystals utilizing modern electron-spin resonance (ESR) techniques. Further studies are planned on molecular reorientational motions including both local and long-range cooperativity. Studies at a molecular level of the dynamics of the liquid crystalline phase transitions utilizing observed critical types of divergences of the spin-relaxation are to be continued. The studies are performed with spin probes of varying size and shape. New Two- Dimensional Fourier Transform ESR methods will be used to obtain more accurate and detailed relaxation data from which to infer both the long-time and short-time molecular motions. Two- dimensional electron-spin-echoes and new high-field ESR methods will enable the study of slow-motional behavior of larger probes in lower temperature phases in terms of their ordering, configuration, and dynamics. The description of molecular motions in liquid crystals will be enhanced by studies of translational diffusion of the probes both at the molecular level (by spin-exchange) and at the macroscopic level (by ESR- imaging). Special emphasis is to be placed upon interpreting results at nematic-smectic phase transitions and within smectic phases in terms of coupled rotational and translational molecular motions, Our powerful computational methods will permit more sophisticated modeling of the motional dynamics as required to interpret these results. These studies will include thermotropics, oriented lyotropic nematics, and oriented polymeric liquid crystals.