| Texto completo | |
| Autor(es): |
Patino-Agudelo, Alvaro Javier
;
Keppeler, Nicolas
;
Quina, Frank H.
Número total de Autores: 3
|
| Tipo de documento: | Artigo Científico |
| Fonte: | COLLOIDS AND SURFACES A-PHYSICOCHEMICAL AND ENGINEERING ASPECTS; v. 725, p. 7-pg., 2025-11-20. |
| Resumo | |
Isothermal titration calorimetry was employed to elucidate the effects of the anions and cations of a series of inorganic salts on the critical micelle concentration (CMC) and the enthalpy of micellization of the zwitterionic sulfobetaine surfactant tetradecyldimethylammonium propanesulfonate (SB3-14) at 298.15 K. The anions studied were Cl-, Br-, I-, and ClO4- (sodium salts) and the cations Li+, Na+, K+, Cs+, Ca2+, and Al3+ (chloride salts). Although cations had little or no effect on the CMC or the enthalpy of micellization, increasing the concentration of the anions decreased both the CMC and the entropy of micellization and made the enthalpy of micellization more negative in proportion to the relative affinities of the anions for the micellar surface. Our data, together with literature data for the temperature dependence of anion binding to the dodecyl homologue (SB3-12) and to dodecyl phosphatidylcholine (DPC), were employed to develop a unified framework for analyzing the thermodynamic consequences of anion effects on zwitterionic surfactants at the CMC. Factoring out effects due to the structure-dependent contributions of the headgroup and hydrocarbon tail and differences in the temperature of the measurements results in values for the net enthalpic and entropic contributions arising from the interaction of the anions with the headgroup. For these three systems, i.e., SB3-14, SB3-12 and DPC, these net contributions exhibited a single linear enthalpy-entropy correlation in which both the net enthalpy and entropy of anion-head group interaction became progressively more negative as the extent and strength of anion binding increased, combined with the concomitant decrease in translational freedom of the anions at the micelle-water interface. The results provide a coherent picture of the thermodynamics of the interaction of anions with zwitterionic interfaces, from the standpoint of the anion, that unifies anion-zwitterion interactions for both possible relative orientations of the cationic and anionic charge centers within a single framewor (AU) | |
| Processo FAPESP: | 17/06394-1 - EMU concedido no processo 2014/22136-4: calorímetro de titulação isotérmica (ITC) para determinação dos parâmetros termodinâmicos de interações moleculares |
| Beneficiário: | Omar Abou El Seoud |
| Modalidade de apoio: | Auxílio à Pesquisa - Programa Equipamentos Multiusuários |
| Processo FAPESP: | 10/51219-4 - Interação entre macromoléculas e superfícies |
| Beneficiário: | Denise Freitas Siqueira Petri |
| Modalidade de apoio: | Auxílio à Pesquisa - Regular |