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|Title:||Characterization of Poly(ethyleneimines) by Electrohydrodynamic Ionization Mass Spectrometry and Investigations of the Mechanism of Surfactant-Sensitization of Metal-Chrome Azurol S Complexes (Sampling, Transport, Spectroscopy, Micelle)|
|Author(s):||Callahan, John Harold|
|Department / Program:||Chemistry|
|Degree Granting Institution:||University of Illinois at Urbana-Champaign|
|Abstract:||Molecular weight distributions of poly(ethyleneimines) (PEIs) were characterized by Electrohydrodynamic Ionization (EH) Mass Spectrometry to determine the effect of both the chemical structure and the solution chemistry of the polymer on its sampling behavior from glycerol.
Ionic series corresponding to PEI+H ('+), PEI+Na ('+), PEI+ 2H ('2+), PEI+2Na ('2+), and PEI+H+Na ('2+) were detected. Number average molecular weights ((')Mn) calculated from EH spectra were lower than the nominal values. Independent measurements of (')Mn suggested that EH results were low due to a sampling bias against higher molecular weight oligomers.
The sampling bias is partly charge-based. The addition of excess acid decreased (')Mn and did not result in multiply charged ions in greater abundance than singly charged ions. Addition of transition metals also reduced (')Mn and caused the disappearance of polymer ions from the spectrum. Only singly charged PEI-transition metal complexes were observed. Ion-solvent interactions may prevent efficient sampling of multiply charged species.
The sampling bias is also dependent on chain length. Sampling of heavier oligomers is probably controlled by cumulative polymer-solvent (hydrogen bonding) interactions. The addition of water to the glycerol matrix resulted in increases in (')Mn, possibly due to differences in the strength of the hydrogen bonds causing the bias.
Studies with the tetramethylammonium ion also showed that some EH signals decrease with time. Modelling suggests that convection-diffusion mass transport controls the surface concentration of some species, introducing another species-dependent factor (the diffusion coefficient) into sampling.
Glycerol-induced solution reduction also affects sampling and was confirmed for m-phenylenebistrimethylammonium iodide (by NMR) and Ru(2,2'-bipyridine)(,3)('3+) (visible spectroscopy). The reduc- tion of Cu(II)-PEI and Ag(I)-PEI (Ag('o) precipitated) was observed in EH studies.
The mechanism of surfactant-induced changes (sensitization) in the visible spectroscopy of metal-Chrome Azurol S (CAS) complexes was also studied. Changes in metal:CAS stoichiometry, 40-100 nm red shifts in absorption maxima, and 10-fold increases in molar absorptivity are typical. The formation of ternary complexes in cat- ionic surfactant (hexadecyltrimethylammonium bromide) solutions and interactions with micelles in anionic (sodium dodecyl sulfate-- only with excess electrolyte) and nonionic surfactant (Triton X-100) solutions causes sensitization. Sensitization varies with the metal ion species.
Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 1986.
|Date Available in IDEALS:||2014-12-15|