Microstructural characterization of lysophosphatidylcholine micellar aggregates: the structural basis for their use as biomembrane mimics.

Lysophosphatidylcholines are widely used as biomembrane mimics. In order to furnish a structural basis for this application, in this work the self-aggregation behaviour of n-acyl-lysophosphatidylcholines (C(n)lysoPC, n=6,8,10,12), in aqueous solution has been investigated by the PGSTE-NMR and spin probing EPR techniques at 25 degrees C. The experimental data show that C(n)lysoPCs behave as zwitterionic surfactants, and permit evaluation of the influence of the acyl chain length on the phospholipid micellization.

Interaction between pentaethylene glycol n-octyl ether and poly(acrylic acid): effect of the polymer molecular weight.

The effect of the polymer molecular weight on the interaction between pentaethylene glycol n-octyl ether (C(8)E(5)) and poly(acrylic acid) (PAA) has been investigated by a combined experimental strategy including tensiometry, potentiometry, calorimetry, fluorescence quenching and intradiffusion (pulsed gradient spin echo-NMR) measurements. PAA samples with an average molecular weight varying in a wide range (M (w)=2000, 100,000, 250,000, and 450,000) have been considered. The measurements have been performed at constant polymer concentration (0.

Interaction between cationic, anionic, and non-ionic surfactants with ABA block copolymer Pluronic PE6200 and with BAB reverse block copolymer Pluronic 25R4.

The interaction in aqueous solution between either the normal block copolymer poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide): Pluronic PE6200 [(EO)(11)-(PO)(28)-(EO)(11)], or the reverse block copolymer poly(propylene oxide)-poly(ethylene oxide)-poly(propylene oxide): Pluronic 25R4 [(PO)(19)-(EO)(33)-(PO)(19)] and the surfactants sodium decylsulfate, C(10)OS, decyltrimethyl ammonium bromide, C(10)TAB, and pentaethylene glycol monodecyl ether, C(10)E(5), was investigated and the aggregation behavior of these surfactants with Pluronics was compared. Surface tension measurements show that Pluronics in their non-aggregated state better interact with the anionic surfactant C(10)OS than with cationic and non-ionic ones. The presence of the two Pluronics induces the same lowering of the aggregation number of C(10)OS as shown by fluorescence quenching measurements.

Effect of glycerol on micelle formation by ionic and nonionic surfactants at 25 degrees C.

The effect of glycerol on the micellization of the cationic surfactant cetyltrimethylammonium bromide (CTAB) and of the ethoxylated nonionic surfactant Brij 58 has been investigated by various experimental techniques. For both surfactants the critical micellar concentration (cmc), determined by surface tension measurements, is almost unaffected by the presence of glycerol in the mixture; only at high glycerol concentrations (>/=20% w/w) does the cmc significantly increase. The area per surfactant molecule at the air-solution interface, A, increases with increasing glycerol weight percentage, w(g).

Interaction between pentaethylene glycol n-octyl ether and low-molecular-weight poly(acrylic acid).

The interaction between pentaethylene glycol n-octyl ether (C8E5) and low-molecular-weight poly(acrylic acid) (PAA, M(w)=2000) in aqueous solution has been investigated by various experimental techniques at constant polymer concentration (0.1% w/w) with varying surfactant molality. Spectrofluorimetry, using pyrene as molecular probe, shows (i) the formation of surfactant-polymer aggregates at a surfactant molality (T(1)) lower than the critical micelle concentration (cmc) of C8E5 in water and (ii) the formation of free micelles at a surfactant molality (T(2)) slightly higher than the cmc.