Cross-polarization experiment polymer blends

Solid state nuclear magnetic resonance spectroscopy (NMR), e.g. [107-109]. This technique is sensitive to the local environment of certain nuclei, their mobility and orientation [108]. It provides information about the heterogeneity of polymer blends to c. 5 nm or less (spin diffusion experiments) or c. 0.3 nm in cross-polarization experiments, from which the direct (averaged) distance between two types of nuclei in a sample can be determined [107,108]. Motions of moleuclar groups in a polymer chain can be analyzed and correlations with dispersion areas in the mechanical spectra may be possible [109]. Solid state NMR is not a standard technique at the present time but it is becoming increasingly important. 

Deuteration of one polymer component, either one homopolymer in a blend, or one block of a copolymer, can also be utilized to study phase separation. In cross-polarized experiments, such as CPMAS/DD or the deuterated species will not appear in the spectrum for heterogeneous samples, or will be observed but with the relaxation time of the protonated component for homogeneous samples. 

The cross-polarization experiment for the study of polymer blends... 

The CP experiments on polymer blend systems, using a mixture of two polymers in which one is deuterated and another is protonated, have been carried out in order to elucidate their miscibility. This information is given by whether protons in the protonated polymer are cross-polarized to deute-rons of the other deuterated polymer or not. These studies show that effective CP transfer may be limited to about 10 A. In the... 

If one of the component polymers has a third spin other than and H, several cross-relaxation experiments become possible. Since spin diffusion occurs a few 10 nm before the polarization decays, only a small amount of the spins near the interface must be detected for immiscible blends. Section... 

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