Doctoral Dissertations

Date of Award

5-1997

Degree Type

Dissertation

Degree Name

Doctor of Philosophy

Major

Chemistry

Major Professor

Spiro D. Alexandratos

Committee Members

Kelsey D. Cook, Bernhard Wunderlich, Gajanan Bhat

Abstract

A series of new chelating styrene-based ketophosphonic acid resins viz., α, β, and y- keto phosphonates has been developed. The resins were synthesized from styrene/divinylbenzene and vinylbenzyl chloride/divinylbenzene copolymers at 2% and 5% cross-linking. In these resins, the geometry of the ligand anchored onto the polymer-support was systematically varied to yield resins of high ionic affinity. Also, phosphorylated polyvinylbenzyl chloride was included in the study for comparison. Intra-ligand cooperation between chelating sites was identified as an important factor responsible for the ionic affinity of these resins. Metal ion complexation studies of these resins with Eu(III), Cu(II), Pb(II), Co(II), Cd(II), and Ag(I) in acidic media (pH 0 to 2) at 24 h contact time indicate that a and β-ketophosphonic acids show a much higher uptake of metal ions than the other resins. This is due to the formation of stable five and six- membered chelate structures accompanied by relatively low loss of rotational entropy upon chelation in the case of and β-ketophosphonic acids respectively. Intra ligand cooperation in highly cross-linked resins (containing 40% divinylbenzene) having the same type of ligands was examined and similar conclusions as that for the 2% cross-linked resins were made.

Basicity of the chelating sites can affect intra-ligand cooperation, as was observed in diphosphonic, dicarboxylic, and phosphonoacetic acid resins at 2% cross-linking. Metal ion complexation studies of these resins with Fe(III) and Cd(II) in acidic media (pH 0 to1) show that the diphosphonic acid has a much higher ionic affinity than the other resins. This is due to the strongly coordinating basic phosphoryl oxygen of the diphosphonic acid.

A new method which involves bifunctionality and coupling of an access mechanism to a recognition mechanism, has been developed for the synthesis of high capacity polymer-supported reagents with enhanced selectivity and ion complexation kinetics. Partially sulphonating a phosphinated polystyrene matrix increases the Eu(III) distribution coefficient from 61.8 to 220.5 at a 30 min contact time in a 1N nitric acid solution.

Finally, new anion exchange resins based on poly(4-vinylpyridine) were developed and tested for the selective absorption of pertechnetate ions. The roles of the microevironment and ligand affinity for the absorption of pertechnetate were examined.

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