FORCED RAYLEIGH-SCATTERING STUDY OF DIFFUSION OF BLOCK COPOLYMERS .2. SELF-DIFFUSION OF BLOCK COPOLYMER CHAINS IN LAMELLAR MICRODOMAINS AND DISORDERED MELTS

Forced Rayleigh scattering (FRS) has been used to measure the diffusion coefficients D of a dye-labeled lamella polystyrene (PS)-polyisoprene (PI) block copolymer (M(n) = 2.1 X 10(4), PS content 42 wt %) in the bulk state. The FRS measurements lead to double-exponential signal decays, the decay constants being grossly proportional to the square of the fringe spacing. We suggest interpreting the signals as originating from a Rouse-like diffusion parallel to the lamella interfaces in lamellae tilted at different angles against the measuring direction. Over the temperature range covered (90 < T < 208 -degrees-C), no drastic change in the behavior of the diffusion coefficient could be observed on crossing the order-disorder transition (ODT) temperature at about 190 -degrees-C.