Because of the sensitivity of the fine structure of the fluorescence emission spectrum of the monomer of pyrene (Py) to its microenvironment and the dependence of the excimer formation on the visicosity of the medium and the distance between the probe molecules, pyrene was employed as a fluorescence probe to monitor the chitosan (CS) gel formation process and the gel swelling properties. It was shown that the changes in the fine structures (I~3/I~1) of its fluorescence spectrum and/or its excimer formation efficiency (I~E/I~M) was well related to the gelation process and the gel swelling degrees. The conformational change of the PNIPAM trapped in the CS gel could also be monitored by the probe technique. The present results may be taken as the basis for the design of an opticfibe method, which may be used to monitor gel formation and swelling processes.

Key words: FLUORESCENCE PROBE, PYRENE, CHITOSAN, HYDROGEL