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

The miscibility of poly(epichlorohydrin) (PECH)/poly(vinyl acetate) (PVAc) blends were investigated by differential scanning calorimeter and C-13 cros s 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 t he miscibility of the system on the scale below 10 nm, high-resolution soli d-state C-13 nuclear magnetic resonance experiment was carried out. The mea surement of cross polarization rate between proton and C-13 carbon nuclei ( T-CH) showed that intermolecular cross polarization was slightly enhanced w ith increase of PECH composition. Single effective H-1 spin-lattice relaxat ion (T-1) time was found for PECH/PVAc. This observation suggests that inte rdomain 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) e xperiment, however, the blends displayed two-component exponential relaxati on behavior, implying that interdomain spin-spin communications among all t he 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 Scie nce Ltd. All rights reserved.