In situ steady state fluorescence (SSF) technique to study drying of PAAm hydrogels made of various cross-linker contents

Drying experiments of polyacrylamide (PAAm) gels were performed using steady-state fluorescence (SSF) spectrometer. Pyranine (P) was introduced as a fluorescence probe and intensity of P from various cross-linker content gel samples was monitored. It was observed that the intensity of P increased during the in situ drying processes. Gravimetrical and volumetric experiments were also performed. An empirical model was derived and introduced to determine the desorption coefficient, D of water molecules from the drying PAAm gels. It is observed that D increased as the cross-linker content was increased.