Effect of Configuration on Diffusion of Residue Model Compounds through Polycarbonate Membranes

The diffusion behavior of residue model compounds with different configurations through polycarbonate membranes was investigated by using a diaphragm cell. The results show that the molecular and pore sizes are two main factors determining diffusivities of compounds with similar configurations, in which the hindered degree of diffusion increases with the increase of relative molecular mass. Different diffusivities between fullerene C84 and hexa-(2-ethylhexyl)-hexa-peri-hexabenzocoronene (HEHHBC) indicate that the configuration has a significant effect on their transport through fine pores. A comparison of the results reveals that diffusion data from fullerenes provided a definitive confirmation of hydrodynamic theory, while the diffusion of other compounds is hindered more severely. By further comparison, it shows that HEHHBC receives the largest diffusion resistance with the same solute-to-pore-size ratio, followed by 2,8-di(4-pentylphenyl)dibenzothiophene (DPPDBT) and then metal porphyrins. It implies that the larger the deviation of the configuration from the spherical structure, the greater the degree of diffusion is hindered.