Spatially resolved electron diffraction and the determination of orientational order parameters in thermotropic liquid crystalline polymer

A low-dose, high-resolution, electron-diffraction technique has been used to calculate local orientational order parameters from thermotropic liquid crystal polymer (TLCP) fibers. Diffracted intensities are extracted from digital electron diffraction patterns for the orientational order parameter calculation, in a manner similar to that used with X-ray diffraction data. The resolution of local orientation is made possible by electron diffraction as opposed to other methods because of the ability to sample regions as small as 100 nm in diameter. Working within the critical radiative dose for structural damage constrains the ultimate spatial resolution. The signal-to-noise ratio (SNR) of the diffraction data collected at high spatial resolution is low due to the small volume sampled. This work demonstrates the dependence of the orientational order parameter on signal-to-noise effects and the convergence of the incoming electron beam.