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 copolymers 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 nonradiative energy transfer measurements were carried out on these films. Analysis of these data yielded the local concentration of dyes within the interphase. This gives the volume fraction of the interphase in the system, 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, 2621] 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; Macromolecules 1991, 24, 5721] from specular neutron reflectivity experiments on similar PS-PMMA diblock copolymers.