Drying of PAAm hydrogels at various temperatures: A fluorescence study


Aktas D. , EVINGUR G. A. , PEKCAN O.

JOURNAL OF MACROMOLECULAR SCIENCE PART B-PHYSICS, cilt.46, ss.581-590, 2007 (SCI İndekslerine Giren Dergi) identifier identifier

  • Cilt numarası: 46 Konu: 3
  • Basım Tarihi: 2007
  • Doi Numarası: 10.1080/00222340701257950
  • Dergi Adı: JOURNAL OF MACROMOLECULAR SCIENCE PART B-PHYSICS
  • Sayfa Sayıları: ss.581-590

Özet

The steady-state fluorescence (SSF) technique was employed for studying the drying of polyacrylamide (PAAm) hydrogels. Disc-shaped hydrogels were prepared by free-radical crosslinking copolymerization of acrylamide (AAm) with N,N'-methylene bisacrylamide (BIS) as crosslinker in the presence of ammonium persulfate (APS) as an initiator. Pyranine (P) was introduced as a fluorescence probe and the intensity of pyranine was monitored during in situ drying at various temperatures. It was observed that the fluorescence intensity of pyranine increased during the drying process. A supporting, gravimetrical experiment was also performed. A phenomenological equation was introduced to determine the desorption coefficient, D, of water molecules from the drying hydrogels at various temperatures. The desorption activation energy, triangle E-d, values were measured for the drying processes and found to be 91.08 and 36.82 kJ mol(-1) by fluorescence and gravimetrical methods, respectively. This difference most probably originates from the origin of the techniques; the fluorescence technique measures the parameters at a molecular level, whereas the gravimetrical technique measures a parameter in the bulk.