Effect of Acetonitrile and N,N-Dimethylformamide on the Formation of Poly(ethylene oxide)-Sodium Alkyl Sulfate Aggregates
AUTOR(ES)
Ferreira, Guilherme M. D., Ferreira, Gabriel M. D., Hespanhol, Maria C., Agudelo, Álvaro J. P., Rezende, Jaqueline P., Pires, Ana C. S., Silva, Luis H. M.
FONTE
J. Braz. Chem. Soc.
DATA DE PUBLICAÇÃO
2018-01
RESUMO
The effects of low contents of acetonitrile (AN) or N,N-dimethylformamide (DMF) on the aggregation of sodium alkyl sulfate surfactants, in the absence and presence of poly(ethylene oxide) (PEO), were investigated using conductivity and isothermal titration calorimetry. The cosolvents slightly changed the critical micellar concentrations and did not alter the critical aggregation concentrations of the surfactants sodium decyl sulfate (DSS) and sodium dodecyl sulfate (SDS) with PEO. However, AN and DMF turned the micellization of the surfactants and their binding to the polymer enthalpically more favorable. For instance, for SDS, the micellization enthalpy, ΔHomic, decreased from close to 0 kJ mol-1 in water to -14.3 kJ mol-1 in the presence of 2.50 mol% AN, and the integral enthalpy change for aggregate formation with the polymer, ΔHagg(int), decreased from -1.1 kJ mol-1 in water to -15.5 kJ mol-1 in the same AN concentration. This was attributed to the modification of the solvation shells of both SDS and PEO by the cosolvent molecules, which reduced the entropic contribution to formation of the aggregates. Consequently, when SDS was replaced with DSS, the AN affected ΔHomic to a lesser extent, with a decrease of 9.1 kJ mol-1, while the ΔHagg(int) values were not altered, highlighting the influence of hydrophobic interactions in the surfactant aggregation process.
Documentos Relacionados
- Construction of surfactant-membrane electrodes selective for sodium dodecyl sulfate in poly(ethylene oxide)-surfactant mixtures
- Chlorophyll Determination in Intact Tissues Using N,N-Dimethylformamide
- Poly(ethylene glycol) or Poly(ethylene oxide)?: Magnitude of end-group Contribution to the Partitioning of Ethylene Oxide Oligomers and Polymers between Water and Organic Phases
- Effect of polystyrene on poly(ethylene terephthalate) crystallization
- Formulae for Determination of Chlorophyllous Pigments Extracted with N,N-Dimethylformamide 1