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Synchrotron WAXS

Procedure

Wide-angle x-ray diffraction experiments were carried out at the μSpot beamline at BESSY II (Berliner Elektronenspeicherring-Gesellschaft für Synchrotronstrahlung, Helmholtz-Zentrum Berlin, Germany). The energy was 15 keV using a silicon 111 monochromator and a beam size of 100 μm. Samples were clamped in a sample holder unit to the positioning of the samples perpendicular to the beam path. Five positions along the length of the fibers were measured. After subtraction of dark current and background scattering from the diffractograms, azimuthal intensity profiles at the (004) reflection were extracted by sector-wise integration after masking the diffractogram to show only the (004) diffraction peak. The Hermans orientation parameter was calculated according to Eqs. 1 and 2 (39) in which, for an axially oriented system, it can be defined as$S=32〈cos2Φ〉−12$(1)

The factor in broken brackets represents the mean square cosine, which was calculated from the scattering intensity I(Φ) by integrating over the azimuthal angle(2)

For a perfectly oriented anisotropic system in the vertical direction, S = 1; for an isotropic system, S = 0; and for a perfectly oriented anisotropic system in the horizontal direction, S = −1/2.

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