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Title: Molecular anisotropy effects in carbon K-edge scattering: depolarized diffuse scattering and optical anisotropy

Some polymer properties, such as conductivity, are very sensitive to short- and intermediate-range orientational and positional ordering of anisotropic molecular functional groups, and yet means to characterize orientational order in disordered systems are very limited. We demonstrate that resonant scattering at the carbon K-edge is uniquely sensitive to short-range orientation correlations in polymers through depolarized scattering at high momentum transfers, using atactic polystyrene as a well-characterized test system. Depolarized scattering is found to coexist with unpolarized fluorescence, and to exhibit pronounced anisotropy. We also quantify the spatially averaged optical anisotropy from low-angle reflectivity measurements, finding anisotropy consistent with prior visible, x-ray absorption, and theoretical studies. The average anisotropy is much smaller than that in the depolarized scattering and the two have different character. Both measurements exhibit clear spectral signatures from the phenyl rings and the polyethylene-like backbone. Discussion focuses on analysis considerations and prospects for using this depolarized scattering for studies of disorder in soft condensed matter.
Publication Date:
OSTI Identifier:
Report Number(s):
DOE Contract Number:
Resource Type:
Journal Article
Resource Relation:
Journal Name: Physical Review B
Research Org:
Ernest Orlando Lawrence Berkeley National Laboratory, Berkeley, CA (US)
Sponsoring Org:
Advanced Light Source Division; Materials Sciences Division
Country of Publication:
United States
74 ATOMIC AND MOLECULAR PHYSICS; 25 ENERGY STORAGE; 37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY; 36 MATERIALS SCIENCE molecular anisotropy effects, resonant x-ray absorption, resonant x-ray scattering, polymers