Abstract
The anisotropic light scattering by polymer molecules in dilute solution is studied on the basis of the helical wormlike chain on which optical polarizability tensors are arrayed with respect to its localized coordinate systems. The four independent components of the scattered intensity are evaluated as functions of scattering angle. It is facilitated by the use of irreducible (spherical) tensors with the expansion of the Green’s function in terms of the normalized Wigner functions. Rather detailed numerical results are presented. Evaluation is also carried out for the rigid rod, regular helix, random coil, and wormlike chain, which are the extreme cases of the helical wormlike chain. It is then noted that there are three possible types of anisotropic rods, and also of anisotropic wormlike chains, one of them being already well known as the one having cylindrically symmetric local polarizability tensors. A procedure for determining accurately the isotropic scattering function from observed scattered components is proposed on the basis of the numerical results. By a computer simulation, it is shown that the procedure does not involve an amplification of experimental errors in the individual components, except near the backward scattering angle. The mean-square optical anisotropy determined from the depolarized component is also evaluated as a function of chain length. The ratio of it to chain length is shown to exhibit a maximum for some helical wormlike chains, and damped oscillation for one of the three types of rods with certain polarizabilities. An analysis of experimental data is made for polymethylene as an example.
Published Version
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