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Master's Dissertation
DOI
10.11606/D.46.1992.tde-08052012-103744
Document
Author
Full name
Mauricio da Silva Baptista
E-mail
Institute/School/College
Knowledge Area
Date of Defense
Published
São Paulo, 1992
Supervisor
Committee
Politi, Mario Jose (President)
Neumann, Miguel Guillermo
Quina, Frank Herbert
Title in Portuguese
Ligação e troca iônica em interfaces zwitteriônicas
Keywords in Portuguese
Adsorção
Bicamadas
Dipolo interfacial
Físico-química orgânica
Micelas
Vesiculas
Abstract in Portuguese
Investigou-se o efeito do "caráter iônico" de interfaces zwitteriônicas, formalmente neutras, representadas por micelas e vesículas obtidas de monômeros com cabeça hidrofílica dipolar, nas propriedades de acumulação e troca de espécies iônicas. Os sistemas estudados incluíram, micelas de 1-(N-hexadecil-N,N-dimetilamônio) propanossulfonato (HPS), Hexadecil fosforil colina (C16PN), 3-hexadecil glicerofostidil colina (lisoPC) e vesículas de fosfatidil colina (PC). O estudo da ligação e troca iônica nestas interfaces foi monitorado a partir de efeitos sobre reações prototrópicas de sondas como a 8-hidroxi-1,3,6-pirenotrisulfonato de sódio (piranina). Observou-se a ligação crescente da piranina na seguinte ordem lisoPC < C16PN < HPS e troca iônica com sais adicionados (função do ânion) na ordem inversa, isto é, lisoPC > C16PN > HPS. Estudos de reprotonação de 1 e 2 naftóis incluídos nestes agregados, via salto de pH induzido por laser, revelaram um perfil de concentração de prótons inverso àquele das cargas do dipolo, isto é, concentração nos polos negativos e exclusão nos positivos. Este resultados foram ainda reforçados por estudos de excitação de volume, via espalhamento de luz, com micelas de HPS em função de sal adicionado. A partir destes resultados propôs-se um modelo de capacitor esférico imerso em meio eletrolítico para estas interfaces, o qual se mostrou bastante versátil na análise e previsão de resultados experimentais. Em suma, estabeleceu-se no presente trabalho a visão de que interfaces dipolares são geradoras de assimetria iônica na circunvizinhança da interface, assimetria esta de polaridade invertida àquela do dipolo radialmente disposto à interface. A generalidade deste modelo pode ser extrapolado para outras interfaces e colaborar na compreensão de diversos processos que dependem da acumulação e troca iônica.
Title in English
Ion Binding and Exchange in zwitterionic interfaces
Keywords in English
Adsorption
Bilayers
Interfacial dipole
Micelles
Organic physico-chemical
Vesicles
Abstract in English
The effect of ionic domains of formally neutral zwitterionic interfaces, represented by micelles and vesicles obtained with dipolar headgroups amphiphiles, on the binding and exchange of ionic species were investigated. The systems studied included: aqueous micelles of 1-(N-hexadecyl-N,N-dimethylammonio) Propane Sulfonate (HPS), Hexadecyl Phosphoryl Choline (C16PN), and 1-hexadecylglycerophostidyl Choline (lisoPC) and vesicles of Phosphatidylcholine (PC). Binding and ion-exchange processes were assessed from the effect of these agreggates on prototropic reactions of probes such as 8-hydroxy-1,3,6-pyrenetrisulfonate pyranine). Binding of pyranine increased in the following order lisoPC < C16PN < HPS. The effectiveness of anion dependent salt displacement of the probe from the aggregates was opposite to that of affinities, i.e. lisoPC > C16PN > HPS. Laser pH jump studies with 1 and 2 naphtols incorporated in these aggregates revealed a proton concentration profile inverse to that of the charged dipole, that is, accumulation in the region vicinal to the negatively charged group and exclusion from the positive end of the dipole. This finding were substantiated by HPS micelle excluded volume data, obtained from light scattering studies as function of added salt. A model of a spherical capacitor immersed in an electrolyte media for these interfaces was proposed. This model accounts for satisfactorily the observed characteristics of these interfaces. The model establishes that dipolar interfaces generate ionic asymmetries in the neighborhood of the interface that opposes the radially extended monomer dipole. The generality of the model can be very helpful in the analysis and understanding of several processes occurring in/at zwitterionic interfaces.
 
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Publishing Date
2012-05-08
 
WARNING: The material described below relates to works resulting from this thesis or dissertation. The contents of these works are the author's responsibility.
  • BAPTISTA, Mauricio S., et al. Electrostatic Properties of Zwitterionic Micelles [doi:10.1021/j100194a063]. The Journal of Physical Chemistry [online], 1992, vol. 96, p. 6442-6449.
  • BAPTISTA, Mauricio S., and POLITI, Mario J. Dipole Oriented Anion Binding and Exchange in Zwitterionic Micelles [doi:10.1021/j100168a042]. The Journal of Physical Chemistry [online], 1991, vol. 95, n. 15, p. 5936-5942.
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