Application of 129Xe NMR to polymer blends.
129Xe NMR expts. on two different polymer blends are described. The first system, a blend of isotactic polypropylene (PP) and a copolymer of polypropylene and polyethylene (EP), shows sep. domains of PP and EP. The latter phase forms rubbery domains in the PP matrix. The second system is the compatible blend of PVDF and PMMA. For the incompatible blend two Xe resonances are found, one for Xe absorbed in the matrix and one for Xe in the rubbery EP phase. The chem. shift of the Xe absorbed in the rubbery phase can be related to the polyethylene content of EP. The line widths and chem. shifts are affected by the polymer motions as a function of the temp. Although the system has two very different glass transition temps., it is striking to see that upon approaching the PP glass transition temp. the Xe resonance of Xe in the rubbery phase is also affected. Due to the dipolar interaction between Xe spins and polymer proton spins, cross-polarization expts. can be performed. This allows the measurement of correlated NMR spectra. The compatible blend shows only one line with a chem. shift proportional to the compn.
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