Simultaneous static and dynamic light scattering: application to polymer structure analysis

Abstract Light scattering is one of the most widely applied methods for the determination of molecular weights. Moreover, the light scattered by a polymer solution contains information about the static and the dynamic properties of the molecules, all of which are important for polymer characterization. In the elastic or static scattering experiment the excess scattering intensity of the solution compared with that of the pure solvent is measured. Here we assume that the scattered light exhibits the same wavelength as the primary light source and accordingly, only static or time-averaged quantities are measured. In reality the scattering particles move randomly in solution, owing to Brownian motion. Since they can be regarded as local transmitters, the scattered light exhibits a Doppler shift, the magnitude of which depends on the velocity and on the direction of motion of the individual particle. A typical scattering volume contains many of these particles, moving with different velocities in different directions. Consequently the observed pectrum of the scattered light is symmetrically broadened. This spectrum S(ω) is principally measured by inelastic or dynamic light scattering, which leads to the dynamical properties of the molecules in solution, such as the translational diffusion coefficient.