About the Lorentz correction used in the interpretation of small angle X-ray scattering data of semicrystalline polymers

Lorentz correction is used to correct the intensities of X-ray scattering o f single crystal diffractometry in order to recalculate intensities to obta in structure factors. This correction reduces the intensities to zero at ze ro diffraction angle. Small angle scattering is used to study the dimension s of heterogeneities in polymeric materials. The scattering intensities nea r to zero scattering angle originate partly from periodic systems (reciproc al lattice) and partly from dispersed particle systems. Periodic systems sh ould result in individual Gaussian or Lorentzian peaks with the position of a peak maximum depending on the length of the periodicity. Particle scatte ring results in a Gaussian peak centred at zero scattering angle. The effec t of the Lorentz correction on the interpretation of small angle X-ray scat tering data is shown in the case of some semicrystalline polyethylenes (hig h density, linear low density, and low molecular weight waxy polyethylenes) . The data are compared with those for amorphous block copolymers (styrene/ butadiene) in which there is a periodic system with homogeneous lamellar th ickness. Lorentz correction destroys the characteristics of the particle sc attering and can be applied only for periodic systems. It should not be use d to produce a peak on scattering data which does not show periodicity (pea ks) without correction. (C) 2001 John Wiley & Sons, Inc.