Miscibility of poly(epichlorohydrin)/poly(vinyl acetate) blends investigated with high-resolution solid-state 13C NMR

The miscibility of poly(epichlorohydrin) (PECH)/poly(vinyl acetate) (PVAc) blends were investigated by differential scanning calorimeter and C-13 cross polarization (CP) combined with magic angle spinning (MAS) spectroscopy. All the blends displayed single but increasing glass transition temperature with increased PVAc concentration. This indicates that the blend system is miscible on the scale of 10-30 nm for the entire composition. To examine the miscibility of the system on the scale below 10 nm, high-resolution solid-state C-13 nuclear magnetic resonance experiment was carried out. The measurement of cross polarization rate between proton and C-13 carbon nuclei (T-CH) showed that intermolecular cross polarization was slightly enhanced with increase of PECH composition. Single effective H-1 spin-lattice relaxation (T-1) time was found for PECH/PVAc. This observation suggests that interdomain spin-spin communications among all the protons in PECH/PVAc blends were possible on the scale of 10-30 nm, which is in good agreement with the DSC results. In the H-1 rotating-frame spin-lattice relaxation (T-1 rho) experiment, however, the blends displayed two-component exponential relaxation behavior, implying that interdomain spin-spin communications among all the protons were not possible within the time of H-1 T-1 rho. Therefore, the domain size is estimated to be 3-30 nm in diameter. (C) 1999 Elsevier Science Ltd. All rights reserved.