Volume 42, Issue 3

Recent progress in the study of pulmonary surfactant is reviewed. The first half of this paper provides general background in both physiological and clinical perspectives. The second half focuses on the in vitro assessment of pulmonary surfactant using methods based on a drop shape technique, Axisymmetric Drop Shape Analysis (ADSA). Theories, experiments, and techniques of image analysis used in these ADSA methods are briefly described. Typical applications of these methods are discussed in detail. It is concluded that the accuracy, versatility, and simplicity of these ADSA methods render them suitable to the study of pulmonary surfactant.

The purpose of this study was to test the feasibility of contact angle measurement in evaluating soilability and cleanability of 11 different surfaces of flooring materials. The surface properties were examined using an expanding contact angle technique and the cleanability was evaluated colorimetrically. The values of advancing contact angles θ A were related to the soil residues on particle-soiled surfaces and oil-soiled surfaces. The results indicate the potential of contact angle measurements to evaluate cleanability of flooring materials.

The soiling and cleanability of eleven worn commercial plastic floor coverings were examined. The new and worn floor coverings appeared very similar in both visual and stereo microscopic inspection. However, wear had caused changes to both topography and cleanability parameters. Profilometer measurements provided information on the topography of new and worn floor coverings. According to the results new surfaces did not always clean better or become soiled more easily than worn coverings. Therefore, we cannot derive a general rule of relationship between wear, soiling and cleanability. The general premise that a rough surface will yield poor cleanability was not confirmed here for all materials.

Inhibitory action of hydroxylated cationic gemini surfactants on corrosion of mild steel [MS] in 1 M hydrochloric acid medium is studied by gravimetric, electrochemical polarization and electrochemical impedance spectroscopic (EIS) techniques. The results obtained reveal that these compounds are very efficient inhibitors. The inhibitory action of surfactants increases with the concentration and chain length. Concentration as low as 10 −5 M of 16–4–16 MEA could show 99% inhibition whereas 12–4–12 MEA showed 93% inhibition at 10 −4 M concentration. The inhibition efficiency versus concentration curves show an S-shape plot indicating adsorption of surfactants on metal surface as a three steps process. From Arrhenius plots corrosion rate of MS was observed to decrease at any given temperature with inhibitor concentration due to the increase in the degree of surface coverage. In contrast, at constant inhibitor concentration, the corrosion rate increases with temperature. EIS measurements show increase in the charge transfer resistance with the inhibitor concentration.

Industrial processes become faster and faster. The corresponding formulations have to keep pace with new technical solutions like spray coating in paper production or the substitution of isopropanol in fountain solutions for offset printing. Fast diffusion of amphiphiles to interfaces and the formation of interfacial films to lower the interfacial energy are the fundamental molecular mechanisms which have to be optimised for all high speed spraying and wetting processes. Our results show that the interfacial tension at water/air and at water/solid interfaces primarily depends on the concentration of free surfactants. Micelles act as depots for free surfactants which adjust the concentration in solution as soon as surfactants disappear by interface adsorption. By using synergistic mixtures it is possible to extend the application range of dynamic surfactants towards detergency by combining fast adsorption at interfaces with micellar properties.

The critical micelle concentration (cmc) of three dimeric surfactants of the alkanediyl- α ,ω-bis(dimethyldodecylammonium bromide) type, one trimeric surfactant and two conventional monomeric surfactants has been measured in the presence of increasing amounts of linear 1-alcohols (methanol to hexanol), using the electrical conductivity method. The results show little difference in the variations of cmc A /cmc W (cmc A and cmc W = cmc values in a water/alcohol mixture and in water) for the monomeric, dimeric and trimeric surfactant with the alcohol concentration for alcohols that are very soluble in water (methanol and ethanol) or hardly soluble in water (pentanol and hexanol). Significant differences are observed only for alcohols that are partitioned between water and micelles (mainly propanol and butanol). Large differences in the solubility of butanol in micellar solutions of the three dimeric surfactants observed at high surfactant concentration appear to be associated to differences in micelle shape. The ionization of dimeric surfactant micelles in ethanol/water mixtures increases nearly linearly with the ethanol content.

The self-assembly of a poly(ethylene oxide)- block -poly(propylene oxide)- block -poly(ethylene oxide) blockcopolymer (EO 13 PO 30 EO 13 ) in the presence of water was investigated. The phases have been studied with the mesoscopic simulation technique Dissipative Particle Dynamics (DPD). The micellar, hexagonal, lamellar, bicontinuous and inverse micellar phase have been identified with this method and showed remarkable agreement with the experimental phase behavior. This work showed that the Dissipative Particle Dynamics simulations are also suitable for complicated polymer systems such as the EO 13 PO 30 EO 13 triblock copolymer.