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Characterization of Nafion solutions and films and observation of the casting process using basic dyes as optical probes
Author(s) -
Otsuki Soichi,
Adachi Kimihiro
Publication year - 1995
Publication title -
journal of applied polymer science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.575
H-Index - 166
eISSN - 1097-4628
pISSN - 0021-8995
DOI - 10.1002/app.1995.070560607
Subject(s) - nafion , solvent , malachite green , polymer , absorption spectroscopy , molecule , chemical engineering , absorption (acoustics) , casting , materials science , methylene blue , relative humidity , chemistry , analytical chemistry (journal) , photochemistry , polymer chemistry , organic chemistry , composite material , optics , catalysis , physics , adsorption , photocatalysis , electrochemistry , thermodynamics , engineering , electrode
Abstract The absorption spectrum of methylene blue and crystal violet (CV) in ethanol–water in the presence of Nafion exhibited metachromasy, but a little or no formation of the large aggregates of the dye was observed. This indicates that the dye molecules are bound to the surface of the miceller particles of the polymer, but the ability of Nafion to induce the aggregation of the dye is weak. The absorption spectrum of malachite green (MG) and CV was measured in a cast film of Nafion at varying ambient humidity. The spectral change with humidity indicates that the decrease in the water content of the film causes the increase of H + ‐ion concentration in the hydrophilic cluster of Nafion and, hence, leads to the protonation of the dyes. The absorption spectrum of a Nafion solution containing MG or CV was recorded in the process of casting. The dyes changed to the protonated form right after evaporation of most solvent from the solution. This suggests that the phase inversion occurs in the casting process. © 1995 John Wiley & Sons, Inc.