05/18/2023
By Kwok Fan Chow

The Kennedy College of Science, Department of Chemistry, invites you to attend a Ph.D. Dissertation defense by Priyanka Biswas entitled “Design and Synthesis of Novel Materials for Applications in Chemical Warfare Protection.”

Degree: Doctoral
Location: Olney Hall, Room 518
Date: Wednesday, May 31, 2023
Time: 1 p.m.

Committee Members:

  • Committee Chair Prof. James F. Reuther, Department of Chemistry, University of Massachusetts Lowell
  • Prof. Marina Ruths, Department of Chemistry, University of Massachusetts Lowell
  • Prof. Mingdi Yan, Department of Chemistry, University of Massachusetts Lowell
  • Prof. James Whitten, Department of Chemistry, University of Massachusetts Lowell

Abstract:
Organophosphorous-based nerve agents remain one of the most toxic and accessible chemical warfare agents known to man. Herein, we report the development of novel, oxime-functionalized activated carbon fibers (Ox-ACF), super pulverized activated carbon (Ox-SPAC) and poly(4-vinylpyridine) (P4VP-Ox) materials as inexpensive, scalable polymeric substrates capable of rapid decontamination of nerve agents, as demonstrated using one nerve agent simulant, dimethyl-4- nitrophenyl phosphate (DMNP). Controlled Friedel-Crafts acylation with 4-aminobenzoic acid (ABAc) in polyphosphoric acid/phosphorous pentoxide (PPA/P2O5) was successfully accomplished onto defect and edge sp2 C-H surface sites of ACF and SPAC. Functionalization was investigated using thermogravimetric analysis (TGA), infrared spectroscopy (IR) and X-ray Photoelectron Spectroscopy (XPS), indicating covalent attachment of ABAc onto ACF and SPAC. Hydroxylamine condensation was then performed on the resultant ketone functionalized activated carbon substrates to decorate their surfaces with oxime moieties. Furthermore, the ability of carefully designed Ox-ACF and Ox-SPAC was implemented for the degradation of DMNP. Ox-ACF and Ox-SPAC exhibit promising performance in detoxifying DMNP, providing complete detoxification using 20 equivalents of Ox-ACF in 48 hours.

To improve the efficiency of degradation of DMNP, P4VP-Ox materials were developed. The incorporated oximes adjacent to positively charged pyridinium salts remain deprotonated at neutral to slightly basic pH, providing super-nucleophilic materials to deactivate nerve agents and their simulants rapidly and irreversibly. These materials were electrospun to form nanofabrics, providing increased surface area and enhanced reactivity for degradation of DMNP. Nanofibers obtained from P4VP functionalized at 20 mol % pendants with ortho-pyridinium oximes moieties (P4VP-OOx20%) provided the fastest reaction kinetics. This substrate provided complete decomposition of DMNP within 1.5 h and calculated t1/2 = 14.4 min. The P4VP-Ox substrates were also found to be recyclable, allowing for quantitative DMNP degradation within 8 h over the course of four reaction cycles. Furthermore, to mimic real-life scenarios, we attempted solid-state DMNP degradation via applying small drops of DMNP directly on the nanofabric substrates and extracting with water for 31P NMR analysis. Overall, the P4VP-OOx20% substrate was found to retain its reactivity in the solid state, with the as-prepared nanofabric displaying >95% DMNP degradation after 6 h. When performed in different environments (i.e., 100% humidity, hexanes-rich atmosphere), the reactivity diminished slightly but still displayed >95% degradation after 24 h of reaction, establishing these materials for applications as reactive, economical, and easily scalable Chem-Bio protective materials.

All interested students and faculty members are invited to attend.