A better understanding of the diffusional behavior of molecules in gels is required for fundamental research work on polymer gels as well as for practical work such as developments of drug delivery systems and separation membranes based on gels. The diffusion coefficient (D) obtained by pulse field gradient nuclear magnetic resonance (PFG NMR) is an effective means to elucidate the dynamics in gel systems. The measurements of D for probe molecules in gels reveal the mobility of the molecules and provide information about the gel network size. In the first section of this article

the self- diffusion phenomenon and the self-diffusion coefficient measurement techniques are briefly introduced. In the second section

we introduced the principle of self-diffusion coefficient measurement by PFG NMR. In the third section

the applications of PFG NMR technology in polysaccharide gel research are introduced.