Investigation of the interactions of polyvinylpyrrolidone with mixtures of anionic and nonionic surfactants or anionic and zwitterionic surfactants by pulsed field gradient NMR

The interaction of polyvinylpyrrolidone (PVP) with an anionic surfactant (sodium dodecyl sulfate, SDS), a nonionic surfactant (pentaethylene glycol monodecyl ether, C(10)E(5)), and a zwitterionic surfactant (lauryl amido propyl betaine, LAPB) has been investigated by means of pulsed gradient spin-echo NMR (FT-PGSE NMR), allowing self-diffusion coefficients to be determined. The results confirm the strong interaction prevailing in the PVP/SDS system, whereas no association has been observed in the PVP/C(10)E(5) and PVP/LAPB systems. Mixing PVP with two surfactants, namely SDS and C(10)E(5) or SDS and LAPB, results in the formation of ternary aggregates between the polymer and the mixed micelles

Adsorption of Poly(vinylpyrrolidone)/Surfactant(s) mixtures at the silica/water interface: a calorimetric investigation

peer reviewedThe adsorption of binary mixtures of poly(vinylpyrrolidone) (PVP) and sodium dodecyl sulfate (SDS) and of ternary mixture of PVP, SDS, and pentaethylene glycol monodecyl ether (C10E5) onto silica has been studied by the measurements of the adsorbed amount of PVP and the heat of adsorption. The amount of PVP adsorbed from the binary mixtures decreases as the SDS concentration is increased, whereas the enthalpy change passes through a maximum at SDS concentration of ca. 4 g/L. The chain conformation of PVP adsorbed on silica has been estimated from the adsorption data in relation to the surfactant concentration. It changes from loops and tails to trains upon increasing SDS concentration. At SDS concentrations higher than 4 g/L, a comblike conformation is observed. The adsorption of PVP/SDS/C10E5 ternary mixtures depends on the polymer concentration regime

Adsorption of an aqueous mixture of surfactants on silica

The behavior of mixtures of a nonionic surfactant, pentaethylene glycol monodecyl ether (C10E5), and an anionic surfactant, sodium dodecyl sulfate (SDS), was studied at the water−silica interface. In contrast to the C10E5 surfactant, which is adsorbed at the silica−water interface at pH 6, the adsorption of the anionic surfactant is not observed. In the presence of SDS, the adsorption of C10E5 is severely restricted as result of the formation of mixed micelles in solution. This behavior is consistent with the adsorption free energy, ΔGads, of C10E5 and the free energy of mixed micellization, ΔGmix.mic, of SDS and C10E5. Flow microcalorimetry (FMC) results showed that the addition of C10E5/SDS mixtures to silica precoated with C10E5 resulted in the release of the preadsorbed nonionic surfactant; the whole phenomenon is exothermic. Combination of calorimetric data (FMC and isothermal titration calorimetry), self-diffusion coefficients, and the regular solution theory led to the conclusion that the main driving force for the C10E5 desorption was the formation of mixed micelles by unimeric SDS and the released nonionic surfactant

Le bien être du personnel infirmier et la qualité des soins

À partir d’une synthèse de plusieurs travaux de recherche portant sur l’environnement de travail, le bien-être professionnel et la perception de la qualité des soins par les infirmiers dans huit hôpitaux belges, les auteurs situent ces éléments dans un contexte plus large des évolutions et tendances actuelles et futures au sein des organisations hospitalières. Les résultats forment un plaidoyer pour l’élaboration d’un cadre normatif pour les établissements de soins de santé. Ce cadre devrait fournir une réponse aux nombreux défis posés aux soins de santé, confrontés aux exigences liés à la performance. En outre, s’il est appliqué, il devrait permettre une approche davantage centrée sur le patient et sa famille, en tant que partenaires de soins et de santé

Mixed micelles of anionic-nonionic and anionic-zwitterionic surfactants analyzed by pulsed field gradient NMR

The micellar composition of two binary surfactant systems, that is, sodium dodecyl sulfate (SDS)/pentaethylene glycol monodecyl ether (C10E5) and SDS/lauryl amido propyl betaine (LAPB), has been analyzed by pulsed gradient spin−echo NMR (FT-PGSE NMR). The experimental data have been compared to theoretical predictions based on the regular solution theory that takes into account the nonideal mixing of the surfactant pairs. Although good agreement between experiment and theory is observed for the SDS/C10E5 pair, some discrepancy is noted for the LAPB/SDS system, particularly at a high molar fraction of SDS

Mixed self-assembly of poly(ethylene oxide)-b-poly(epsilon-caprolactone) copolymers and sodium dodecyl sulfate in aqueous solution

peer reviewedInteraction of amphiphilic poly(ethylene oxide)-b-poly(epsilon-caprolactone) copolymers with anionic sodium dodecyl sulfate (SDS) has been investigated in aqueous solution. Formation of mixed micelles has been confirmed by surface tension measurements, whereas the influence of the surfactant on the copolymer self-assembling has been studied by measurement of the 1H NMR self-diffusion coefficients and by small-angle neutron scattering. As a rule, the surfactant decreases the heterogeneity of the micellar structures formed by the copolymer in water. Moreover, increasing the content of SDS results in the increasingly more important extension of the poly(ethylene oxide) (PEO) corona chains and the copolymer micelle deaggregation. The stability of the micelles against SDS increases with the length of the hydrophobic block. Preliminary two-dimensional NMR measurements with nuclear Overhauser enhancement have confirmed the spatial vicinity between SDS and the constitutive blocks of the copolymer