Polyelectrolytic Behavior of a Novel Fluorine-Containing Ionomer, PPFNA

Solution properties of a novel fluorine-containing ionomer PPFNA were studied by pH titration, conductivity, and viscosity measurements. This polymer is a poly(carboxylic acid) but dissociates strongly, resulting in a low pH value and a high specific conductance at low degrees of neutralization. When the solution was neutralized with NaOH, the conductance decreased sharply at first and then decreased gradually until full neutralization. This conductometric titration profile indicates that this polymer is a fairly strong polyelectrolyte but not a typical strong one such as poly(styrene sulfonic acid) or aliphatic ionenes. The pH measurement showed that this polymer is a strong polyacid, although the titration profile changed slightly upon the addition of salt. The reduced viscosity of the salt-free solution was well fitted to Fuoss' equation, specific to polyelectrolyte solutions. Upon the addition of salt, however, the viscosity−neutralization profile became rather similar to that of weak polyacid, and the concentration dependence of the reduced viscosity shifted gradually to that of nonionic polymer solutions. The corresponding monomer behaves like a completely strong acid, in contrast to the polymer, especially in conductometric titration.