Thermal characterization and solid-state ¹³C-NMR investigation of blends of poly(N-phenyl-2-hydroxytrimethylene amine) and poly(N-vinyl pyrrolidone)

The miscibility and thermal properties of poly(N-phenyl-2-hydroxytrimethylene amine)/poly(N-vinyl pyrrolidone) (PHA/PVP) blends were examined by using differential scanning calorimetry (DSC), high-resolution solid-state nuclear magnetic resonance (NMR) techniques, and thermogravimetric analysis (TGA). It was found that PHA is miscible with PVP, as shown by the existence of a single composition-dependent glass transition temperature (T_g) in the whole composition range. The DSC results, together with the ¹³C crosspolarization (CP)/magic angle spinning (MAS)/high-power dipolar decoupling (DD) spectra of the blends, revealed that there exist rather strong intermolecular interactions between PHA and PVP. The increase in hydrogen bonding and in T_g of the blends was found to broaden the line width of CH - OH carbon resonance of PHA. The measurement of the relaxation time showed that the PHA/PVP blends are homogeneous at least on the scale of 1-2 nm. The proton spin-lattice relaxation in both the laboratory frame and the rotating frame were studied as a function of the blend composition, and it was found that blending did not appreciably affect the spectral densities of motion (sub-T_g relaxation) in the mid-MHz and mid-KHz frequency ranges. Thermogravimetric analysis showed that PHA has rather good thermal stability, and the thermal stability of the blend can be further improved with increasing PVP content.