Supramolecular complexes formed by the association of poly(ethyleneimine) (PEI), sodium cholate (NaC) and sodium dodecyl sulfate (SDS)

Abstract

A formação de complexos supramoleculares em solução aquosa pela associação do polieletrólito poli(etilenoimina) (PEI) com misturas do biossurfactante colato de sódio (NaC) e o surfactante aniônico dodecil sulfato de sódio (SDS) foi aqui investigado usando as técnicas de condutivimetria, tensiometria, fluorimetria, espalhamento de raios X a baixos ângulos (SAXS) e medidas de pH. Os resultados de fluorimetria, condutivimetria e medidas de pH levaram à conclusão de que os monômeros de NaC e SDS ligam-se primeiramente em sítios específicos das cadeias do polieletrólito PEI via interação eletrostática e posteriormente através de associação cooperativa. A interação do NaC com o PEI é mais fraca do que a interação do SDS com o PEI, porém, a adição de SDS ao sistema NaC-PEI levou à formação de micelas mistas SDS-NaC que interagiram fortemente com o polieletrólito PEI. Os resultados de SAXS sugeriram que o complexo supramolecular possui característica elipsoidal e essa forma não depende da concentração de surfactante nem da χ NaC .The formation of supramolecular complexes produced by association of poly(ethyleneimine) (PEI) and mixtures of sodium cholate (NaC) and sodium dodecyl sulfate (SDS) was investigated by pH, electrical conductivity, fluorescence spectroscopy and small angle X-ray scattering (SAXS) measurements. The fluorescence linked to previously measured values of pH and conductivity led to the conclusion that NaC and SDS molecules firstly bind to specific sites of the PEI chains via electrostatic interaction and secondly undergo self-assembly through regular cooperative association. The interaction of NaC with the polyelectrolyte PEI is weaker than that of SDS and the addition of SDS to the NaC-PEI system led to the formation of mixed NaC-SDS micelles which stronger interact with PEI. The SAXS results suggested that the micellar aggregates have a considerably ellipsoidal characteristic and the micellar shape is not affected by the surfactant concentration nor by χ NaC .Keywords: sodium cholate, sodium dodecyl sulfate, poly(ethyleneimine), polymer-surfactants interaction IntroductionBile salts are naturally-occurring amphiphilic molecules. They are physiologically important in the solubilization and transport of fats and lipids. The structure of bile salts in water has been extensively investigated. Although they are comparable to common surfactants, the general conclusion is that biosurfactants self-assemble in a different way than the standard surfactants. [1][2][3][4][5][6][7][8][9][10][11][12][13] Poly(ethyleneimine) (PEI) is a member of a large family of water-soluble polyamines having different molecular weights (M w ) and polymer architectures. Polyamines are weak bases and exhibit a cationic character depending on the degree of protonation. PEI has been extensively studied (particularly the branched form) due to its intense use in the formulation of drugs, thickeners, flocculating agents, personal care products, food products, detergents and adhesives. It has also been used for biological proposes to p...

Polyethylenimines as Homogeneous and Heterogeneous Catalysts for Glucose Isomerization

“…The protonation of amine in water can in situ generate hydroxide ions, which acts as a base catalyst for the isomerization reaction. However, the addition of a neutral salt can greatly influence the protonation of amine in water. − Specifically, the salt can promote the protonation of amine through changing the activity coefficients of all ionic species in the solution, and the protonation constant of amine is a function of the ionic strength. , Upon the addition of salt, the protonated amine can form a complex with the anion of salt through electrostatic interaction, and the stability of the complex increases with increasing the protonation. The salt ions can influence differently the water dissociation and hence shift the acid–base equilibrium and increase the pH value of the amine aqueous solution.…”

“…The salt ions can influence differently the water dissociation and hence shift the acid–base equilibrium and increase the pH value of the amine aqueous solution. Previous research has shown that the addition of salts such as sodium chloride and lithium chloride created conformational changes and increased the pH value of a PEI aqueous solution from 7.0 to around 9.0. , The PEIs in this study were positively charged weak polyelectrolytes due to the protonation of the primary, secondary, and tertiary amines, as indicated by the observed positive zeta potentials shown in Figure S7. The positively charged PEIs can specifically bind with anions of salts through electrostatic interactions.…”

Influence of stabilising agents and pH on the size of SnO2 nanoparticles

“…At this point, all of the active groups of the polymer are already occupied by individual particles or micelles from the surfactant and any excess forms free micelles, unrelated to the polymer chain ( Fig. 6 ) [ 26 – 27 ]. All of these processes affect the kinetics of the precipitation reaction of tin dioxide nanoparticles and cause a change in their size.…”

Estudo das dispersões aquosas de nanotubos de carbono utilizando diferentes surfactantes

“…29,31,36 No entanto, esta técnica pode interferir na obtenção de valores de cmc e cac, pela possível perturbação da estrutura micelar, decorrente da baixa solubilidade do pireno, formando agregados pré-micelares. …”