ENERGY-TRANSFER STUDIES OF THE BOUNDARY-LAYER INTERPHASE IN POLYSTYRENE POLY(METHYL METHACRYLATE) BLOCK-COPOLYMER FILMS

Six pairs of polystyrene-poly(methyl methacrylate) (PS-PMMA) diblock c opolymers were prepared with a single fluorescent dye attached to the junction point. One partner contains phenanthrene (the donor), and the other, anthracene (the acceptor). Films were prepared, and nonradiati ve energy transfer measurements were carried out on these films. Analy sis of these data yielded the local concentration of dyes within the i nterphase. This gives the volume fraction of the interphase in the sys tem, from which we can calculate the ratio R/delta, where delta is the thickness of the interphase and R is the length of the minor phase in the periodic structure of the system. Further analysis of the data in terms of the theory of Ohta and Kawasaki [Macromolecules 1986, 19, 26 21] indicates that R/delta varies as N0.70 (predicted, N2/3) and delta is about 51 angstrom. This value is remarkably close to that (50 +/- 5 angstrom) reported by Russell [J. Chem. Phys. 1990, 92, 5677; Macrom olecules 1991, 24, 5721] from specular neutron reflectivity experiment s on similar PS-PMMA diblock copolymers.