Synthesis, characterization, and mechanistic studies of novel dual mechanism bifunctional polymers for ionic and molecular recognition

Author

Paul Timothy Kaiser

Date of Award

8-1990

Degree Type

Dissertation

Degree Name

Doctor of Philosophy

Major

Chemistry

Major Professor

Spiro D. Alexandratos

Committee Members

J. E. Bartmess, J. D. Kovac, L. C. Wadsworth

Abstract

lon-exchange/redox resins of the phosphinic acid and phosphonic acid types have been synthesized using various Friedel-Crafts catalysts. The results of these syntheses show that AICI₃ under forcing conditions forms bifunctional resins containing primary and secondary phosphinic acid groups, while FeCl₃ yields bifunctional resins containing primary phosphonic acid and secondary phosphinic acid groups. ZnCl₂ and SnCl₄ give only very low levels of functionalization. The order of catalyst activity was shown to be AlCl₃gt;FeCl₃> >ZnCl₂>SnCl₄~no catalyst. Subsequent work with the phosphinic acid resins has shown that the kinetics of the ion-exchange/redox reaction with mercury is most likely diffusion-limited, while silver displays reaction-limited ion-exchange/redox kinetics, and that removal of both metals from the resin by HNO₃ is diffusion-limited. Reduction back to a phosphinic acid resin subsequent to mercury or silver oxidation has been shown to be quantitative with a mixture of LAH/CeCl₃ in dioxane. After esterification of the metal oxidized phosphinic acid resin with ethanol and dicyclohexylcarbodiimide, a trichlorosilane/N,N-dimethylaniline mixture was also shown to be effective for the reduction. Molecular recognition was investigated using a linear free energy relationship. These investigations were carried out using carboxylic acid, sulfonic acid, phosphinic acid, phosphonic acid, phosphonate mono and diethyl ester, dimethylamine, trimethylamine, PEG, PEI, and PEG/phosphonic acid resins with a series of anilines, phenols, and benzole acids in water, methanol, water/methanol mixtures, and dioxane. It has been determined that selectivity of ion-exchange resins for organic compounds with ionizable groups from methanol is a direct consequence of the strength of the interaction between the target compound and the resin functional groups, and reaches a maximum when the acid and base strength of the two groups are fairly well matched, with selectivity decreasing rapidly with an increase in the difference in interaction strength. If the interactions are very strong or very weak, selectivity is not observed under non-competitive conditions. Under competitive conditions, selectivity is observed even for compounds which interact strongly with the resin. In water a hydrophobic effect was also observed, which decreased the selectivity of the resin, but caused a large increase in the overall amount of the target compounds absorbed. A solvent effect was also observed by carrying out the absorptions in dioxane, which caused a marked decrease in the amount of the compounds absorbed due to limited accessibility of the functional groups on the resins.

Recommended Citation

Kaiser, Paul Timothy, "Synthesis, characterization, and mechanistic studies of novel dual mechanism bifunctional polymers for ionic and molecular recognition. " PhD diss., University of Tennessee, 1990.
https://trace.tennessee.edu/utk_graddiss/11431