![]() Monodisperse solutions of flexible coils present new complications not seen in earlier discussions of light scattering spectroscopy. Dynamic light scattering (DLS) is used to characterize particle size distributions and hydrodynamic sizes of particles and molecules ranging from 0.3 nm to 10. An analysis of experimental data is made for polymethylene as an example. The immediately prior chapter included light scattering spectra of colloidal systems, in which the underlying forces (hydrodynamic, volume exclusion) are much the same as in polymer solutions. 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. Chapters address multicomponent mixtures, polyelectrolytes, dense polymer systems, gels. The mean‐square optical anisotropy determined from the depolarized component is also evaluated as a function of chain length. the widely varying fields in which the technique finds application. 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. A procedure for determining accurately the isotropic scattering function from observed scattered components is proposed on the basis of the numerical results. Dynamic light scattering (DLS) is a valued sizing technique for proteins, colloids and dispersions, which comfortably extends to the sub 1 nm region. 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. 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. Rather detailed numerical results are presented. Purpose: to measure polymer dimensions using dynamic light scattering (DLS) and to relate the particle size to the number of monomers. Dynamic Light Scattering (DLS) is an efficient method of measurement employed for calculating the hydrodynamic size of common nanomaterials consisting of nanoparticles, colloids, polymers and proteins. 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. The four independent components of the scattered intensity are evaluated as functions of scattering angle. 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.
0 Comments
Leave a Reply. |