Light Scattering of Stiff Chain Polymers

The angular distribution of scattered light (or the particle scattering factor) of the stiff chain polymers is calculated by assuming an appropriate Fourier transform of the distribution function of this polymer chain. For very small and very large scattering angles the result is respectively reduced to the forms of the Debye's scattering factor for random coil chain and to that for rigid rod molecule. By assuming that the polymer chain expansion by intramolecular forces is uniform, but the contour length is kept as constant the excluded volume effect on the angular distribution is calculated. The result shows that the transition point of scattering curve which gives a boundary between random coil- and rigid rod-scatterings is inversely proportional to the square of molecular expansion coefficient. This is in qualitative agreement with the recent experimental results by Wada and other. An approximate distribution function which gives the correct second and fourth moments of the chain end to end distance is also calculated.