FRS STUDY OF DIFFUSIONAL PROCESSES IN BLOCK COPOLYMER HOMOPOLYMER BLENDS CONTAINING GLASSY SPHERICAL MICELLES/

Forced Rayleigh scattering (FRS) was used to study diffusional process es in block copolymer/homopolymer blend systems forming spherical micr odomains. Materials used were an asymmetric polystyrene-bloch-polyisop rene copolymer (M(n) = 74 000, 21 wt % polystyrene) labeled with photo sensitive dyes (o-nitrostilbene or fluorescein) at the end of polystyr ene block chains (b-PS) and two kinds of homopolyisoprene (HPI) (M(n) = 23 000, M(n) = 90 000). Using the lower molecular weight HPI for ble nding with the block copolymer, b-PS spheres with coronas of polyisopr ene block chains (b-PI) strongly swollen by the matrix HPI are obtaine d (wet-brush system), whereas the HPI matrix having higher M(n) yields much less swollen coronas of b-PI (dry-brush system). The differences between these two systems in structural and dynamical behavior were f ound by small-angle X-ray scattering and FRS studies, respectively. To exclude chain release from the spherical micelles during the measurem ents, diffusion has been studied close to the T-g of b-PS microdomains . Unexpectedly, FRS signals differed strongly if measured well below o r slightly above the T-g of PS microdomains in both intensity and corr esponding diffusional processes.