Characterization of the interface of heterogeneous blends of polycarbonate and polyfluorostyrene by C-13-F-19 REDOR NMR

Blends of one part of carbonyl-C-13, ring-C-13, or methyl-C-13-labeled polycarbonate with nine parts of poly(p-fluorostyrene) or poly(o-fluorostyrene) have been examined by C-13-F-19 rotational-echo double-resonance NMR. The immiscible blends were formed by precipitation from choloroform solution into methanol. After being annealed at 180 degrees C, the blends consist of domains of polycarbonate (average diameter of 36 nm) dispersed in a matrix of polyfluorostyrene. There are no kinetically trapped polycarbonate chains. The interface is tightly packed, with an average polycarbonate-polyfluorostyrene nearest-neighbor separation of labels of less than 4 Angstrom. The interface is also partially ordered, with the F-19 distances to the polycarbonate isopropylidene moiety greater than to the carbonate group. Despite the tight packing at the inter face, polycarbonate ring dynamics in chains nearest to polyfluorostyrene are indistinguishable from those in bulk polycarbonate.