Diffusion coefficients of saccharides and amino acids were measured in cross-linked polymers such as dextran gels, polyacrylamide gels and photo-crosslinkable resins of different gel concentrations or various degrees of crosslinkage. Comparison of diffusion coefficients in gels with those in polymer solutions indicated that the diffusional velocity in gels was restricted not only by the interaction between diffusing substances and gel components but also by the steric hindrance of gel matrix. The diffusion coefficients in dextran gels and polyacrylamide gels were appreciably lower than those in polymer solutions, and the degree of lowering depended on both the gel concentration and the size of diffusing substances. The photo-crosslinkable resins basically composed of polyethylene glycol showed a higher permeability than dextran and polyacrylamide gels on account of a weak interaction between diffusing substances and resin component. Furthermore, an attempt was made to correlate the decrease of diffusion coefficients in gels with the diffusion coefficients in polymer solutions and the distribution coefficient of the diffusing substances.

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