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The synthesis of aromatic polyethers by aromatic nucleophilic substitution

Clough, Robert Steven
http://rave.ohiolink.edu/etdc/view?acc_num=case1057072167

Abstract Details

1993, Doctor of Philosophy, Case Western Reserve University, Macromolecular Science.
The objective of this work was to develop an understanding of the processes which limit the molecular weight obtainable in the polyetherifications of sulfones and ketones involving bis(aryl chloride)s that are activated by the carbonyl group, and then to develop strategies to obtain high molecular weight polymers. This work demonstrates that reductive dehalogenation of the bis(aryl halide) or aryl halide chain end of the polymer can compete with aromatic nucleophilic substitution of the halide by the phenolate. In the synthesis of aromatic poly(ether ketone)s and poly(ether sulfone)s, reductive dehalogenation results in benzophenone and diphenylsulfone chain ends, respectively. These chain ends are unreactive and consequently, terminate the polymerization. The occurrence of reductive dehalogenation is dependent on the chemical structures of the bis(aryl halide) and bisphenolate, and the reaction conditions. This work shows that the balance between aromatic nucleophilic substitution and reductive dehalogenation is determined by the electron density at the aromatic carbon that is bonded to the halogen nucleofuge, the reduction potential of the bis(aryl halide), and the oxidation potential of the bisphenolate in terms of one electron redox processes. As the electron density at the aromatic carbon that is bonded to the nucleofuge decreas es, the balance shifts towards aromatic nucleophilic substitution. As the reduction potential of the bis(aryl halide) becomes less negative (i.e., the bis(aryl halide) becomes easier to reduce) and the oxidation potential of the bisphenolate becomes more negative (i.e., the bisphenolate becomes easier to oxidize), the balance shifts toward reductive dehalogenation. These results strongly suggest that reductive dehalogenation is due to single electron transfer from the bisphenolate to the aryl halide chain end and bis(aryl halide). Therefore, these polyetherifications involve a competition between polar and single electron transfer (SET) pathways. The aromatic nucleophilic substitution reaction constitutes the polar pathway, whereas the reductive dehalogenation reaction constitutes the SET pathway. The SET pathway has a higher activation energy than the polar pathway, therefore as the polymerization temperature is increased, the amount of reductive dehalogenation relative to aromatic nucleophilic substitution increases. This work demonstrates that with the proper choice of bisphenolate and reaction conditions, high molecular weight poly(ether ketone)s can be synthesized from bis(aryl chloride)s. (Abstract shortened by UMI.
Virgil Percec (Advisor)
188 p.
Chemistry, Polymer
aromatic polyethers; nucleophilic substitution

Recommended Citations

Citations

  • Clough, R. S. (1993). The synthesis of aromatic polyethers by aromatic nucleophilic substitution [Doctoral dissertation, Case Western Reserve University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=case1057072167

    APA Style (7th edition)

  • Clough, Robert. The synthesis of aromatic polyethers by aromatic nucleophilic substitution. 1993. Case Western Reserve University, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=case1057072167.

    MLA Style (8th edition)

  • Clough, Robert. "The synthesis of aromatic polyethers by aromatic nucleophilic substitution." Doctoral dissertation, Case Western Reserve University, 1993. http://rave.ohiolink.edu/etdc/view?acc_num=case1057072167

    Chicago Manual of Style (17th edition)

case1057072167
718
© 1993, all rights reserved.
This open access ETD is published by Case Western Reserve University School of Graduate Studies and OhioLINK.