Spin diffusion with C-13 selection and detection for the characterization of morphology in labeled polymer blends with MAS NMR

A pulse sequence has been implemented for the determination of domain sizes in C-13 enriched organic materials with two-dimensional high-resolution ma gic angle spinning (MAS) NMR correlation spectroscopy. The method integrate s the high resolution of C-13 MAS for selection and detection with an effic ient polarization transfer across domain boundaries via strong H-1 dipolar interactions. A one-dimensional version with spectral editing allows fdr im proved efficiency with respect to measurement time. With this MAS NMR and l abeling approach heterogeneity at length scales from 1 to 100 nm can be det ermined for systems without long-range order. As an example, proton spin di ffusion times up to 500 ms were used to study the morphology of a phase-sep arated semi-interpenetrating network of poly(styrene-co-acrylonitrile) and cross-linked poly(styrene-co-maleic anhydride). From the spin diffusion beh avior a characteristic domain diameter d = 63 +/- 4 nm was calculated.