Miscibility of poly(ethyl oxazoline)/poly(4-vinylphenol) blends as investigated by the high-resolution solid-state 13C NMR

The miscibility of poly(ethyl oxazoline) (PEOx) and poly(4-vinylphenol) (PVPh) blends were investigated by differential scanning calorimeter (DSC), Fourier-transform infrared spectroscopy (FTIR), and high-resolution solid-state nuclear magnetic resonance (NMR) spectroscopy. It was found that PEOx was miscible with PVPh as shown by the existence of single composition-dependent glass transition temperature (T-g) in the whole composition range. FTIR results revealed strong hydrogen bonding between the carbonyl groups of PEOx and the hydroxyl groups of PVPh. C-13 cross-polarization (CP)/magic angle spinning (MAS)/dipolar decoupling (DD) spectra of the blends showed significant chemical shift changes, which support the FTIR results. The proton spin-lattice relaxation times in both the laboratory frame, T-1(H), and the rotating Frame, T-1 rho(H), were studied as a function of blend composition, and blends gave values longer than pure polymers. The T-1(H) results are in good agreement with the thermal analysis; i.e. the blends are completely homogenous on the scale of 30-40 nm. The T-1 rho(H) results further indicate that the blends were homogenous on the scale of 2-3 nm. (C) 2000 Elsevier Science Ltd. All rights reserved.