Adsorption behavior of surface-chemically pure N-alkyl-N-(2-hydroxyethyl)aldonamides at the air/water interface

Synthesis, Characterization and Surface Activity of Trioctyl Hydroxyethyl Ammonium Chloride

Trioctyl hydroxyethyl ammonium chloride was synthesized from trioctylamine, hydrochloric acid and ethylene oxide by a two-step process. The structure of the quaternary ammonium salt was characterized by FTIR and 1H NMR. The surface tension at the critical micelle concentration was measured to investigate the surface activity of it.

Carbohydrate-modified siloxane surfactants and their adsorption and aggregation behavior in aqueous solution

Four carbohydrate-modified siloxane surfactants, Si(n)N-GA and Si(n)N-LA (n = 3, 4), were designed and synthesized. Their surface activities, adsorption, and aggregation behavior in aqueous solution were investigated by surface tension measurements, dynamic light scattering (DLS) and transmission electron microscopy (TEM). Due to the bulky siloxane moiety at the end of hydrophobic chains, the surfactant solutions displayed low critical aggregation concentration (cac) and low surface tension. Surface tension measurement for all three surfactants are under 22 mN x m(-1), much lower than those of ordinary hydrocarbon surfactants. Due to its poor solubility in water, surface tension of Si(4)N-GA could not be measured. DLS and TEM analysis of Si(3)N-GA, Si(3)N-LA, and Si(4)N-LA aqueous solutions revealed self-assembled spherical vesicles, indicating potential applications as microsphere drug delivery systems and as models of biomembranes.

Re-evaluating the Gibbs analysis of surface tension at the air/water interface

Molecular areas of soluble films at the air/water interface have traditionally been calculated by applying the Gibbs equation to the steep linear decline in surface tension as the bulk concentration increases. This approach presupposes that the interface is saturated in the "Gibbs region," thereby allowing a single unique area to be calculated. We show that the areas derived by the Gibbs equation (typically 50-60 A(2)/molecule) are much too large to account for the abrupt surface tension decline. Moreover, a surface tension/concentration plot was observed for a system where micelle formation does not interfere with the Gibbs region. Nonetheless, the surface tension plot leveled off, ostensibly owing to saturation, when the Gibbs approach predicted a continued linear decline, proving that the interface in the Gibbs region is not saturated as generally assumed. This conclusion means that the hundreds of published molecular areas obtained by the Gibbs approach should be reconsidered.

Preparation and antitubercular activities of alkylated amino alcohols and their glycosylated derivatives

A series of N- and C-alkylated amino alcohols and of their protected galactopyranosyl derivatives was synthesized and evaluated for antitubercular activity. Five of these compounds displayed good activity, with a MIC below 12.5mug/mL. The presence of the carbohydrate slightly affected the antibacterial activity.

Investigations on foamability of surface-chemically pure aqueous solutions of functionalized alkylaldonamides

The foamability of the aqueous solutions of functionalized, surface-chemically pure surfactants of the nonionic saccharide-type: N,N-di-n-alkylaldonamides, N-alkyl-N-(2-hydroxyethyl)aldonamides, and N-cycloalkylaldonamides, derivatives of D-glucono-1,5-lactone and/or D-glucoheptono-1,4-lactone, were investigated. The approach of Lunkenheimer and Małysa for the characterization of the foamability and foam stability of these surfactant solutions was applied for these investigations. Using standard parameters related to the different physical stages of the foaming process, foam stability can be described in a simple and easy manner. In general, the investigated alkylaldonamides form foams of medium stability. However, for some homologues a transition from unstable to stable foam systems is observed with increasing concentration. Modifications of the molecular structure of the alkylaldonamides are distinctly reflected in their foam properties. This fact concerns not only changes of the hydrophobic moiety and its functionalization but also slight variations of the saccharide residue. Each homologous series reveals an exceptional foam behavior. In the case of the N,N-di-n-alkylaldonamides the increase of the n-alkyl chain length is accompanied by an increase of the foam stability. The aqueous solutions of the N-alkyl-N-(2-hydroxyethyl)aldonamides reveal most favorable foaming properties for homologues with average alkyl chain lengths. Moreover, it was found that the occurrence of a phase transition in the adsorption layers of the N-cyclooctylgluconamides previously observed by surface tension and surface potential measurements is also remarkably reflected in their foam stability.

Adsorption behavior of surface chemically pure N-cycloalkylaldonamides at the air/water interface

Equilibrium surface tension (sigma(e)) and electric surface potential (DeltaV(e)) versus concentration isotherms of the homologous series of N-cycloalkylaldonamides synthesized from cycloalkylamines (from cyclopentyl- to cyclododecylamine) and D-glucono-1,5-lactone (c-C(n)GA) or D-glucoheptono-1,4-lactone (c-C(n)GHA) (c-n(C) = 5-12) were investigated at the air/water interface. The measurements were performed with aqueous, surface chemically pure surfactant solutions. Equilibrium surface tension vs concentration isotherms were evaluated to get the adsorption parameters, i.e., standard free energy of adsorption, DeltaG degrees (ads), saturation surface concentration, Gamma(infinity), minimum surface area demand per molecule adsorbed, A(min), and interaction parameter, H(s). Increasing the size of the cycloalkyl moiety leads to a significant increase of the minimum surface area demand per molecule adsorbed. This fact, together with a decrease of the intermolecular interaction parameter suggests that the introduction of a more bulky cycloalkyl ring (c-n(C) = 7 and 8) causes an attenuation of the hydrogen-bond network. This goes in line with the exceptional finding that the higher homologues revealed improved solubility in water. In addition, surface tension investigations suggest occurrence of a phase transition for the N-cyclooctylaldonamides at relatively small surface coverage. This observation is well supported by the surface potential measurements, for which the effect of possible changes in the molecules' surface orientation is even more pronounced. Moreover, the concentration intervals of N-cyclooctylaldonamide in which the change in orientation is observed for either the surface tension or the surface potential isotherms are in very good agreement.