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Dynamical scattering and electron diffraction from thin polymer lamellar crystals - poly(tert-butylethylene sulfide)
1Electron Diffraction Department, Hauptman-Woodward Medical Research Institute, 73 High Street, Buffalo, NY 14203-1196, USA. dorset@hwi.buffalo.edu
Summary
Electron diffraction of poly(tert-butylethylene sulfide) reveals strong Friedel symmetry violations. Multislice dynamical scattering calculations explain these deviations, allowing crystal structure determination despite perturbations.
Area of Science:
- Materials Science
- Crystallography
- Polymer Science
Background:
- Lamellar crystals of poly(tert-butylethylene sulfide) were studied using electron diffraction.
- Observed Friedel symmetry violations in hk0 patterns at 120 kV indicated complex scattering phenomena.
Purpose of the Study:
- To investigate and explain the strong violations of Friedel symmetry in electron diffraction patterns.
- To determine the crystal structure of poly(tert-butylethylene sulfide) despite scattering complexities.
Main Methods:
- Utilized 120 kV electron diffraction on lamellar poly(tert-butylethylene sulfide) crystals.
- Performed multislice dynamical scattering calculations to model observed diffraction patterns.
- Employed direct methods and Fourier refinement for crystal structure determination.
Main Results:
- Strong Friedel symmetry violations were observed and largely explained by dynamical scattering.
- A secondary scattering component improved model accuracy, suggesting crystallite thickness is less than lamellar thickness.
- Frustrated chain packing was successfully determined despite multiple-scattering perturbations.
Conclusions:
- Multislice dynamical scattering is crucial for interpreting electron diffraction from these crystals.
- Averaging Friedel-related intensities is necessary for accurate normalized structure factor calculations.
- The crystal structure and frustrated chain packing of poly(tert-butylethylene sulfide) were elucidated.