Inorganic matrices, relaxation dispersion

Considering, for instance, a system containing 1 nm thick plates, Ipm in diameter, the distance between plates would approach 10 nm at only 7 vol% of plates [217]. The behavior of PNCs can be rationalized as follows. The proliferation of internal inorganic-polymer interfaces means the majority of polymer chains reside near an inorganic surface. Since an interface restricts the conformations that polymer molecules can adopt, and since in PNCs with only a few volume percent of dispersed nanoparticles the entire matrix polymer may be considered as nanoscopically confined interfacial polymer, the restrictions in chain conformations will alter molecular mobility, relaxation behavior, and the consequent thermal transitions such as glass transition temperature of the composites [217]. 

The improvement in mechanical properties by inorganic fillers is considerably reduced if there is a nonuniform dispersion of particles in the polymer matrix by formation of agglomerates. NMRI can produce visual pictures of the spatial variation of the organic phase distribution. This is accomplished by observing the proton images of the elastomers as a function of proton density and spin-spin, T2, relaxation times. These NMR parameters provide a measure of the molecular mobility, which in turn is related to the spatial variation of the polymer and the filler in the sample. 

Gels and related system. When polymers dispersed in a liquid are cross-linked, gels are formed. I review here the works dealing with relaxation/dynamics of the liquid component in gels (the matrix components are usually studied using the solid state techniques). One paper has dealt with an inorganic gel (calcium-silica hydrate, C-S-H), important in the context of cement-based materials. The authors used MD simulations and Cl NMR studies to characterize the transport properties. 

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