Characterization of the Interface of Heterogeneous Blends of Polycarbonate and Polyfluorostyrene by ¹³C−¹⁹F REDOR NMR

Abstract

Blends of one part of carbonyl-13 C, ring-13 C, or methyl-13 C-labeled polycarbonate with nine parts of poly(p-fluorostyrene) or poly(o-fluorostyrene) have been examined by 13C−19F rotational-echo double-resonance NMR. The immiscible blends were formed by precipitation from choloroform solution into methanol. After being annealed at 180 °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 Å. The interface is also partially ordered, with the 19F distances to the polycarbonate isopropylidene moiety greater than to the carbonate group. Despite the tight packing at the interface, polycarbonate ring dynamics in chains nearest to polyfluorostyrene are indistinguishable from those in bulk polycarbonate.

Investigation of the Viability of Solid-State NMR Distance Determinations in Multiple Spin Systems of Unknown Structure

“…The rotational-echo double-resonance (REDOR) , and transferred-echo double-resonance (TEDOR) , techniques introduced recently by Schaefer and co-workers have been utilized in structural investigations of a diverse range of materials including peptides, − proteins, , polymers, , molecular sieves, − and inorganic materials. − For samples containing isolated IS spin pairs, it has been clearly demonstrated that reliable heteronuclear distances (which are in very good agreement with those determined from X-ray diffraction measurements) can be obtained using CP, REDOR, and TEDOR experiments. ,, …”

Location of Fluorotryptophan Sequestered in an Amphiphilic Nanoparticle by Rotational-Echo Double-Resonance NMR

“…2, top) has substantial contributions from carbons that are in the polystyrene core as well as from carbons in the poly-(acrylic acid)-polyacrylamide shell. Qualitatively, this result indicates that some of the fluorotryptophan must be near the core-shell interface (Tong and Schaefer, 1997). The radius of the SCK is 14 nm (Fig.…”