Macromolecular architecture effects on block copolymer dynamics. II. A(2)Bsimple grafts

Photon correlation spectroscopy has been used to investigate the dynamics o f composition fluctuations in disordered semidilute solutions of (polyisopr ene)(2)(polystyrene) (I2S) graft copolymers in toluene. Four different rela xation mechanisms were identified with different concentration and wavevect or dependencies: Three are the well-known processes in diblock copolymer so lutions (cooperative diffusion, internal mode, and polydispersity diffusive mode), whereas the fourth is an extra process between the internal and the polydispersity modes that appears near the disorder-to-order transition. T he latter displays similar characteristics to a process recently observed f or inverse starblock copolymers also in the ordering region, and should be related to the macromolecular architecture. (C) 1999 John Wiley & Sons, Inc .