Specific effects of Ca(2+) ions and molecular structure of β-lactoglobulin interfacial layers that drive macroscopic foam stability.

β-Lactoglobulin (BLG) adsorption layers at air-water interfaces were studied in situ with vibrational sum-frequency generation (SFG), tensiometry, surface dilatational rheology and ellipsometry as a function of bulk Ca(2+) concentration. The relation between the interfacial molecular structure of adsorbed BLG and the interactions with the supporting electrolyte is additionally addressed on higher length scales along the foam hierarchy - from the ubiquitous air-water interface through thin foam films to macroscopic foam. For concentrations <1 mM, a strong decrease in SFG intensity from O-H stretching bands and a slight increase in layer thickness and surface pressure are observed.

Evaluation of therapeutic pulmonary surfactants by thin liquid film methods.

An example of the application of the Black Foam Film (BFF) Method and the Wetting Film Method, using the Microinterferomertric and the Pressure Balance Techniques, for characterization interfacial properties of the animal derived therapeutic pulmonary surfactant preparations (TSP), is presented. BFF thickness, probability of black film formation, and disjoining pressure for foam films from TSP aqueous solutions are measured as well as the wetting properties of TSP solutions on solid surfaces with different hydrophobicity have been studied. Interfacial characteristics such as minimal surfactant concentration to obtain black film (critical concentration) and concentration at which a black film is 100% obtained (threshold concentration) are determined.

Effect of surfactant adsorption time on the observation of Newton black film in foam film.

Observation of Newton black film (NBF) in foam film is possible only with a certain probability W which depends on the concentration C of surfactant in the solution and on the time t(a) during which adsorption of surfactant at the solution/air interface has taken place. In the paper, the W(C,t(a)) dependence is derived and used to analyze the effect of t(a) on the critical surfactant concentration C(c) below which NBF in foam film practically cannot be observed. An expression for the C(c)(t(a)) function is obtained which reveals that C(c) decreases substantially with increasing t(a).

Thin liquid films from aqueous solutions of non-ionic polymeric surfactants.

The conditions of formation and stability of foam, emulsion, and wetting films from aqueous solutions of non-ionic polymeric surfactants have been established. Two types of polymeric surfactants - PEO-PPO-PEO three-block copolymers (A-B-A type) and hydrophobically modified inulin graft polymer (AB(n) type) - have been explored. Information about surface forces and nanoscale phenomena in aqueous films containing polymeric surfactants was obtained using the micro-interferometric technique and the Thin Liquid Film-Pressure Balance Technique.

A pH-study of n-dodecyl-beta-D-maltoside foam films.

The influence the pH has on the properties of foam films stabilized by the nonionic surfactant n-dodecyl-beta-d-maltoside (beta-C12G2) was studied. Foam film measurements were carried out with the thin film pressure balance (TFPB) technique using two different film holders, namely, the Scheludko-Exerowa cell and the porous plate. With the former, the equilibrium film thickness h at a given capillary pressure Pc and, with the latter, complete disjoining pressure versus thickness curves (Pi-h curves) were measured.

Amphiphilic nanostructures in thin liquid films.

A survey on recent experimental investigations of microscopic foam films containing self-assembled amphiphilic nanostructures is presented. The film characteristics are investigated via microinterferometric method, which operates with the measuring cell of Scheludko-Exerowa. The results show the following: (1) Unstable black patterns (dots and spots) are observed; they have very short lifetimes and the films which contain them rupture quickly.

Rheological behavior and parameters of the in vitro model of lung surfactant systems: the role of the main phospholipid component.

The proposed in vitro model for studying the alveolar surface layer of the lungs enables one to investigate the surface intermolecular forces which influence the stability of the alveolus. The general role for the stability of the alveolus belongs to the phospholipids in the alveolar surfactant and predominantly to their main component dipalmitoylphosphatidylcholine (DPPC). The aim of the study was to investigate the rheological behavior of DPPC and exogenous surfactant preparations used in neonatal clinical practice.

Chain-melting phase transition and short-range molecular interactions in phospholipid foam bilayers.

Occurrence of two-dimensional chain melting phase transition in foam bilayers was established for the first time. Microscopic horizontal foam bilayers [Newton black films (NBF)] were investigated by the microinterferometric method of Scheludko-Exerowa. The foam bilayers were formed from water-ethanol solutions of dimyristoylphosphatidylcholine (DMPC) and dipalmitoylphosphatidylcholine (DPPC) and egg phosphatidylcholine (Egg PC) and samples of amniotic fluid (AF) at different temperatures.