Structural compatibility in composite hydrogels III. An NMR study

Most useful polymeric materials are in the form of blends of two or more ho mopolymers. Their performance depends critically on the degree of mixing ac hieved in the blend. This paper discusses NMR spin lattice relaxation in tw o commercially important composite hydrogels and exploits the effects of sp in diffusion to assess the scale of spatial homogeneity in the two samples. The NMR data confirm spatial homogeneity on a dimensional scale of the ord er of 20-25 nm in both materials. As part of the overall analysis. an expre ssion for the intrinsic spin lattice relaxation time for a rotating methyl group is presented. (C) 2000 Elsevier Science Ltd. All rights reserved.