Diffusion and release of the guest molecules in supramolecular organogel

Bis(4-stearamidophenyl)methane (BSAPM) was used as a gelator for preparation of 1,1,2-trichloroethane (TCE) supramolecular organogels. The existence of salicylic acid and rhodamine B as the guest molecules led to the slight decrease of gel-sol phase transition temperatures (T-GS) of the organogels. The diffusion and release of the guest molecules in the organogels were investigated by using UV-vis spectroscopy. The results indicated that release ratios of the guest molecules decreased with the increase of the gelator concentration. Wherein, the release ratios of rhodamine B were less than those of salicylic acid, which could be attributed to the larger molecular size of rhodamine B. In addition, the diffusion coefficients of rhodamine B were also less than those of salicylic acid. This trend was clearer with the increase of BSAPM concentration. The investigation indicated that the diffusion and release behavior of the guest molecules in the self-assembled organogel followed the Higuchi equation and diffusion-controlled mechanism of Fickian model.