Search results for "surface tension"

Pulmonary surfactant protein C containing lipid films at the air-water interface as a model for the surface of lung alveoli.

1995

The pulmonary surfactant lines as a complex monolayer of lipids and proteins the alveolar epithelial surface. The monolayer dynamically adapts the surface tension of this interface to the varying surface areas during inhalation and exhalation. Its presence in the alveoli is thus a prerequisite for a proper lung function. The lipid moiety represents about 90% of the surfactant and contains mainly dipalmitoylphosphatidylcholine (DPPC) and phosphatidylglycerol (PG). The surfactant proteins involved in the surface tension adaption are called SP-A, SP-B and SP-C. The aim of the present investigation is to analyse the properties of monolayer films made from pure SP-C and from mixtures of DPPC, DP…

Phase behaviour and interfacial tension of polysiloxane blends

1998

Abstract The cloud point curve for blends of poly(dimethyisiloxane) (PDMS, M w = 2.5kg mol −1 ) and poly(hexylmethylsiloxane) (PHMS, M w = 113kg mol − ] was determined turbidimetrically. The system demixes upon cooling and the UCST amounts to 36°C. The interfacial tension γ was determined at the critical composition for three temperatures by means of a spinning drop tensiometer. The dependence of γ on the reduced critical temperature can be described within experimental error by both the mean field theory and the Ising-3D theory.

Interfacial Assembly and Jamming Behavior of Polymeric Janus Particles at Liquid Interfaces

2017

The self-assembly and interfacial jamming of spherical Janus nanoparticles (JNPs) at the water/oil interface were investigated. Polymeric JNPs, made by cross-linking polystyrene-block-polybutadiene-block-poly(methyl methacrylate) (PS-PB-PMMA), with a high interfacial activity assemble at the water/oil interface. During the self-assembly at the interface, the interfacial energy was reduced and a dynamic interlayer was observed that is responsive to the pH of the aqueous phase. Unlike hard particles, the JNPs are composed of polymer chains that can spread at the liquid-liquid interface to maximize coverage at relatively low areal densities. In a pendant drop geometry, the interfacial area of …

Interfacial energy effects within the framework of strain gradient plasticity

2009

AbstractIn the framework of strain gradient plasticity, a solid body with boundary surface playing the role of a dissipative boundary layer endowed with surface tension and surface energy, is addressed. Using the so-called residual-based gradient plasticity theory, the state equations and the higher order boundary conditions are derived quite naturally for both the bulk material and the boundary layer. A phenomenological constitutive model is envisioned, in which the bulk material and the boundary layer obey (rate independent associative) coupled plasticity evolution laws, with kinematic hardening laws of differential nature for the bulk material, but of nondifferential nature for the layer…

Effects of KL4-Type Peptides on the Surface Activity and Stability of Pulmonary Surfactant Films as Evaluated in the Captive Bubble Surfactometer

2012

Although SP-B is the most critical protein in lung surfactant, recombinant or synthetic forms of SP-B as a basis for the development of therapeutic surfactants are still not available. An alternative is the design and production of peptides mimicking the structure and general properties of essential motifs in SP-B.In the present study the surface activity of different KL4-derived peptides, as sequence variations of the original peptide designed to replicate a general amphipathic motif of SP-B [1], has been assessed in the captive bubble surfactometer. The peptides were reconstituted in a surfactant lipid matrix: DPPC/POPC/POPG (50:25:15, w/w/w). This mixture was selected because it offers a…

Interfacial tension of demixed polymer solutions: augmentation by polymer additives

1997

The interfacial tension between phase separated polymer solutions increases pronouncedly upon the addition of asmall amounts of incompatible polymers. This feature is demonstrated by means of measurements with solutions of polystyrene in cyclohexane and the folloowing additives: poly(styrene-block-dimethylsiloxane), polyisobutylene and polydimethylsiloxane. Theoretical considerations based on a correlation between the lenth of the tie lines and the corresponding interfacial tension corroborates this finding

Interfacial tension between polymer-containing liquids - Predictability and influences of additives

1999

The first part of the contribution deals with the interfacial tension, σ, of phase-separated polymer solutions in single or mixed solvents and of binary polymer blends as a function of the relative distance to the critical temperature of the system, special attention being paid to the possibilities of theoretical prediction. Two methods are discussed in more detail. One is based on a realistic description of the Gibbs energy of mixing as a function of composition, the second correlates σ with the length of the measured tie line. The second part is devoted to another aspect, namely the effects of additives on the interfacial tension between the coexisting phases of demixed polymer solutions …

2003

Polymer brushes in solvents of variable quality: Molecular dynamics simulations using explicit solvent

2007

The structure and thermodynamic properties of a system of end-grafted flexible polymer chains grafted to a flat substrate and exposed to a solvent of variable quality are studied by molecular dynamics methods. The macromolecules are described by a coarse-grained bead-spring model, and the solvent molecules by pointlike particles, assuming Lennard-Jones-type interactions between pairs of monomers (epsilon(pp)), solvent molecules (epsilon(ss)), and solvent monomer (epsilon(ps)), respectively. Varying the grafting density sigma(g) and some of these energy parameters, we obtain density profiles of solvent particles and monomers, study structural properties of the chain (gyration radius componen…

Effects of organic aerosol constituents on extinction and absorption coefficients and liquid water contents of fogs and clouds

1978

We have speculated on the influence of organic material on extinction and absorption coefficients and liquid water content of fogs and of clouds immediately after their condensational stage. It results therefore, that the reduction of the speed of growth from fog to cloud droplets due to the presence of organic films largely reduces the properties mentioned. Compared to that their increase coming from the surface tension reduction due to organic material being dissolved or building up films is expected to be less effective.