Probing miscibility and intermolecular interactions in solid polymer blends using the nuclear Overhauser effect

A new strategy is discussed for probing polymer-polymer miscibility and detecting specific intermolecular interactions in polymer blends by exploiting nuclear Overhauser effects (NOE) in 13 C magic-angle spinning (MAS) NMR spectra of solid blends. In the comparison of deuterated polystyrene (PS)/poly(vinyl methyl ether) (PVME) blends cast from toluene versus chloroform, steady-state equilibrium NOE enhancements of the PS signals were observed for the toluene-cast films but not for the chloroform-cast films. Since cross-relaxation of the PS carbons may occur only through dipolar interactions with PVME protons (which have an inverse sixth power dependence on the internuclear distances), this demonstrates molecular level miscibility for the blends cast from toluene only