Photon correlation spectroscopy in the polarized light scattering geom
etry can be employed to study the dynamics of composition fluctuations
in disordered diblock copolymer melts near the order-to-disorder tran
sition. The origin of a diffusive relaxation mode, very recently measu
red on a series of undiluted copolymers, can be rationalized in terms
of composition polydispersity effects rather than relaxation of equili
brium composition configurations of the fluctuation theory.