In this talk I will focus on the light scattering techniques which involve the elastic (and quasi-elastic) scattering of a photon by the scattering particle. Broadly speaking, the methods can be separated into static light scattering (SLS) and dynamic light scatering (DLS), where in the former one measures the intensity of the scattered light, I(q), as a function of the scattering angle (or the scattering wavevector q) and in the latter one measures the decay of the intensity fluctuations via the intensity auto-correlation function, G(q,t). Static light scattering has been used to measure the equilibrium structure factor, the particle form factor, the molecular weight, and thermodynamic quantities such as the second virial coefficients in polymer solutions. Recently very small angle static light scattering with video or CCD camera detection is being applied in a time-resolved manner to follow the kinetics of phase separation in polymeric systems. Dynamic light scattering provides a convenient way to measure diffusion coefficients of macromolecules in dilute solutions and the dynamics of polymers in solutions of varying concentration. In particular the functional form of the correlation function is a sensitive indicator of the state of aggregation and even gelation in macromolecular systems. I will illustrate these abilities of light scattering techniques by results on a molecule called mucin. The same ideas apply to small angle x-ray scattering, except that light scattering probes length scales from 100nm to microns whereas x-rays probe smaller length scales from 0.1 nm to 10 nm.

Some general references on light scattering:

Laser Light Scattering--Ben Chu, Acad. Univ. Press 1991 (2nd Edition).

Dyanmic Light Scattering The Method and Some Applications by Wun Brown, Oxford Univ. Press 1993.