Reduced Crystallinity and Mobility of Nylon-6 Confined near the Organic–Inorganic Interface in a Phosphate Glass-Rich Nanocomposite Detected by 1H–13C NMR

Abstract

The effects of confinement of solid polyamide 6 in a nanocomposite with a rigid inorganic glass, a hybrid organic–inorganic material with potential applications in optoelectronics, gas/liquid barrier membranes, and heterogeneous catalysis, have been investigated by 13C, 1H–13C, and 1H–1H solid-state nuclear magnetic resonance (NMR) spectroscopy. The material is synthesized by melt blending 90 vol % of a low-Tg tin fluorophosphate glass (Pglass) with 10 vol % polyamide 6 (PA6). 13C NMR with selective spectroscopy of rigid and mobile segments shows a 2-fold suppression of the average crystallinity of PA6 in the composite. The reduction in crystallinity, to ca. 5%, is even more pronounced for PA6 near the interface with Pglass, as seen in selective 13C spectra of PA6 near the organic–inorganic interface obtained by two-dimensional 1H–13C correlation NMR. The spectrum after a 13C T1 filter indicates a reduced mobility of the interfacial PA6 polymer, which is in ∼5 nm thick domains according to 1H spin-diffusion experiments. The spectra prove that about half of the PA6 is in the nanocomposite, while the rest is bulklike in large domains. The presence of large domains is also deduced from incomplete 1H spin exchange between PA6 and Pglass in the 1H spin-diffusion experiments.