J. Denamganai et al., DESORPTION FOLLOWED WITH RADIOISOTOPES AND MEMBRANE-POTENTIALS IN PERFLUORINATED VINYL4PYRIDINE AND QUATERNARY AMMONIUM MEMBRANES, European Polymer Journal, 31(11), 1995, pp. 1067-1074
A radiotracer technique used to follow desorption and exchange process
es with vinyl4pyridine (V4P) and quaternary ammonium membranes (QAM) a
llowed one to compare the properties of these two types of membranes a
nd to point out the deprotonation process in V4P membranes. Exchange c
apacities obtained with this technique were compared with those obtain
ed by microanalysis titration of nitrogen from V4P exchange sites. The
deprotonation process enabled one to explain the important difference
s obtained with the two methods. With radiotracers we could set up a n
ew technique to determine the pK(a) of these membranes. This work was
completed by measuring swelling ratios and membrane potentials in uncr
oss-linked and cross-linked V4P and QAM membranes. These measurements
allowed one to study the cross-linking and hydration effects with NaCl
and HCl solutions and to point out the importance of the deprotonatio
n process in water and in NaCl solutions. Potential measurements show
for these two types of membranes an important loss of permselectivity
in concentrated HCl or NaCl solutions.