DIRECT ENERGY-TRANSFER STUDIES OF THE DOMAIN-BOUNDARY INTERFACE IN POLYISOPRENE-POLY(METHYL METHACRYLATE) BLOCK-COPOLYMER FILMS

Direct nonradiative energy transfer (DET) experiments were carried out on five polyisoprene-poly(methyl methacrylate) diblock copolymers wit h polyisoprene volume fractions ranging from 0.07 to 0.5 (polyisoprene microdomains dispersed in a poly(methyl methaerylate) matrix). These experiments yield the ratio R/delta of the microdomain size R to the t hickness of the domain-boundary interface delta as a function of the b lock copolymer overall chain length N. A plot of ln(R/delta) vs ln N i ndicates that the microdomain size varies as N-0.65, close to the N-2/ 3 predicted by theory, while the interfacial thickness delta (26 Angst rom) is independent of the degree of polymerization covered in this wo rk. In addition, the Flory-Huggins interaction parameter chi for PI-PM MA was determined from the DET data (0.077). We conclude from these ex periments that PI-PMMA belongs to the class of strongly segregated sys tems.