ИСТИНА

Motivated by recent advances in the design of new materials with controlled microgeometry, we analyze diffusion of a solute in a periodic porous medium formed of cavities connected by narrow tubes. The specific feature of the particle migration in such a medium is that the process consists of strongly pronounced stages due to high entropic barriers impeding transitions of diffusing particles from one structure element to another. Each stage (stay in a void, passagethrough a channel, hit a dead space, etc.) can be treated in terms of the theory of diffusion controlled reactions with spatial restrictions. As a result, the effective diffusion coefficient can be expressed via the geometrical parameters of the medium and the solute diffusion coefficient in the bulk. This approach formulated is used to consider the diffusion in a channel with branches (comb-like structure). The results are tested bу Brownian dynamics simulation.