Study on structure and molecular dynamics of starch/poly(sodium acrylate)-grafted superabsorbent by 13C solid state NMR

Abstract

The domain-structure of samples containing a series of starch/poly(sodium acrylate)-grafted superabsorbents, pure starch, pure poly(sodium acrylate), and blend of starch/poly(sodium acrylate) has been studied by high-resolution solid-state 13C NMR spectroscopy at room temperature. The result shows that the crystallinity of starch decreases greatly in the grafted and blended samples. The values of 1H spin-lattice relaxation time in rotating frame T1ρ and 1H spin-lattice relaxation time T1 shows that starch and poly(sodium acrylate) components in both grafted and blended samples have good compatibility in nanometer scale. In the 13C cross-polarization/magic-angle-spinning (CP/MAS) spectra, the chemical shift of the carbonyl group of poly(sodium acrylate) depends on the composition of the grafting samples, which indicates that the starch and the poly(sodium acrylate) components of the grafting samples exhibit better compatibility with each other than that of blended samples at molecular level.