Pore size effect on diffusion coefficient of rhodamine B in PNIPA gel

We report that the reduction of the diffusion coefficient of rhodamine B mo lecules in a poly(N-isopropylacrylamide) gel is well explained by the pore size effect of a gel network. The diffusion coefficient was calculated from the time development of the concentration profile at different temperature . The coefficient decreased with decreasing the shrink ratio that is a func tion of temperature. Assuming the gel network is homogeneous, the average v alue of the pore size could be estimated as a function of the shrink ratio. The pore size effect on the diffusion coefficient via the apparent viscosi ty was well evaluated based on the probability of which a rhodamine B molec ule passes through a pore. (C) 1999 Published by Elsevier Science B.V. All rights reserved.