Energy Transfer Studies of Binary Block Copolymer Blends. 1. Effect of Composition on the Interface Area per Chain and the Lamellar Size

Abstract

Binary blends of polyisoprene−poly(methyl methacrylate) PI−PMMA diblock copolymers with a common PMMA length and different lengths of polyisoprene blocks were prepared from samples containing a single fluorescent dye, either phenanthrene (donor) or anthracene (acceptor), at the junction point. The two pure block copolymers and their mixtures were studied by the direct energy transfer (DET) technique. All experiments point to intimate mixing of the samples over the entire composition range. These DET experiments yield the interphase volume per junction vj and/or the ratio R/δ of the microdomain size R to the interphase thickness δ, as a function of the composition of the block copolymer mixture. Since, for these strongly segregated chains, the interface thickness is invariant with chain length and should also be constant for this set of mixtures, we can calculate from vj and R/δ the interface area per chain and the period spacing R. Here we find that addition of up to 25 mol % of the second polymer has no ...