Investigation at the chain segmental level of the miscibility of poly(vinyl chloride)/atactic poly(methyl methacrylate) blends

We employed high-resolution C-13 cross-polarization/magic-angle-spinning/ dipolar-decoupling NMR spectroscopy to investigate the miscibility and phase behavior of poly(vinyl chloride) (PVC)/poly(methyl methaerylate) (PMMA) blends. The spin-lattice relaxation times of protons in both the laboratory and rotating frames [T-1 rho(H) and T-1 rho(H), respectively] were indirectly measured through C-13 resonances. The T-1 rho(H) results indicate that the blends are homogeneous, at least on a scale of 200-300 Angstrom, confirming the miscibility of the system from a differential scanning calorimetry study in terms of the replacement of the glass-transition-temperature feature. The single decay and composition-dependent T-1 rho(H) values for each blend further demonstrate that the spin diffusion among all protons in the blends averages out the whole relaxation process; therefore, the blends are homogeneous on a scale of 18-20 Angstrom. The microcrystallinity of PVC disappears upon blending with PMMA, indicating intimate mixing of the two polymers. (C) 2001 John Wiley & Sons, Inc.