TITLE:
Counterion Binding in Aqueous Solutions of Poly(vinylpyridines) as Assessed by Potentiometric Titration
AUTHORS:
Jim D. Roach, Mandy M. Bondaruk, Abdulaziz Al-Abdulghani, Zaid Shahrori
KEYWORDS:
Poly(vinylpyridine), Counterion Binding, Potentiometric Titration, Perchlorate
JOURNAL NAME:
Advances in Materials Physics and Chemistry,
Vol.6 No.9,
September
6,
2016
ABSTRACT: The extent to which counterions bind to
polyelectrolytes influences a variety of polymer-based applications, including
polyelectrolyte enhanced ultrafiltration and forward osmosis using
polyelectrolytes as draw agents. Potentiometric titrations of poly (2-vinylpyridine)
(P2VP), poly (3-vinylpyridine) (P3VP), and poly (4-vinylpydine) (P4VP) were
performed using HBr, HCl, HNO3, and HClO4 in both the
presence and absence of added NaCl. Because of the systematic differences among
the three polyelectrolytes, titration results provide insight into the role of
polymer structure in the relative extents to which various counterions bind.
Titration data reveal that ionization properties vary as functions of polymer
investigated, titrant used, degree of protonation, and added salt
concentration. Acid dissociation constants of the pyridinium moieties were
found to generally increase with increasing degree of protonation, though appreciable
differences were exhibited among the three polymers investigated. For all three
polymers, Cl- demonstrated the lowest affinity for the charged
pyridinium residues, while the affinities associated with Br- and NO-3 were nearly
identical to each other. The relative extent of binding for CIO-4 varied across
the polymers investigated, and was greatest for P4VP.