Structural compatibility in composite hydrogels: III. An NMR study

Most useful polymeric materials are in the form of blends of two or more homopolymers. Their performance depends critically on the degree of mixing achieved in the blend. This paper discusses NMR spin lattice relaxation in two commercially important composite hydrogels and exploits the effects of spin diffusion to assess the scale of spatial homogeneity in the two samples. The NMR data confirm spatial homogeneity on a dimensional scale of the order of 20–25 nm in both materials. As part of the overall analysis, an expression for the intrinsic spin lattice relaxation time for a rotating methyl group is presented.