DYNAMICS OF COMPOSITION FLUCTUATIONS IN STATISTICAL COPOLYMER SOLUTIONS

Dynamic properties of styrene-methyl methacrylate (MMA) statistical co polymer solutions in benzene, a solvent isorefractive with MMA, were s tudied by dynamic light-scattering spectroscopy (DLS) and by pulsed-he ld-gradient NMR (PFG-NMR). Two separate dynamic processes were found f rom the DLS results in the semidilute region. The fast process was rel ated to the cooperation diffusion mode. The slow diffusive process was attributed to the dynamics of composition fluctuations. The diffusion coefficient of the slow process has the magnitude similar to the self -diffusion coefficient determined by PFG-NMR. Dynamic property of the slow ''polydispersity'' mode were qualitatively interpreted in terms o f the theory developed for diblock copolymers.