Search results for "Tension"

Nonionic Maleic Surfmers

2002

ABSTRACT A set of nonionic maleic surfactants have been prepared, all coming from the derivatization of maleic hemiesters with a long alkyl chain. They are either amidoesters or diester products. In the case of amidoesters, the acid group was first activated and then reacted with primary or secondary or tertiary ethanolamine compounds. In the case of diesters, the hemiester was reacted directly with glycidol, in acid or basic conditions. These surfactants were characterized for their structure by 1H NMR, and for their surface active properties, by surface tension measurements. They were also used in batch emulsion polymerisation of styrene, and seeded core-shell copolymerisation of a 1/1 mi…

Interfaces between coexisting phases in polymer mixtures: What can we learn from Monte Carlo simulations?

1999

Symmetric binary polymer mixtures are studied by Monte Carlo simulation of the bond fluctuation model, considering both interfaces between coexisting bulk phases and interfaces confined in thin films. It is found that the critical behavior of interfacial tension and width is compatible with that of the Ising model, as expected from the universality principle. In the strong segregation limit, only qualitative but not quantitative agreement with the self-consistent field (SCF) theory is found. It is argued that the SCF theory requires √ 6 X √D for short-range forces, in agreement with experiment.

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…

Monolayers of Bolaform Amphiphiles: Influence of Alkyl Chain Length and Counterions

1994

We have prepared self-assembled monolayers of novel cationic bolaform amphiphiles on negatively charged substrates. Most of these amphiphiles form smooth, defect-free monolayers which can be used to reverse the substrate surface charge and thus allow subsequent adsorption of anionic molecules and construction of multilayers. Atomic force microscopy, surface force measurement, and surface plasmon spectroscopy were combined to probe the molecular orientation and ordering, mechanical properties, and surface electrical properties of the monolayers. In addition, the amphiphile aggregation behavior at an air-water interface was studied by surface tension measurement, and lyotropic phase behavior …

1991

The polysoaps [CH 2 C(Me)(CO 2 R)] n (R=(CH 2 ) 11 N + Me 2 (CH 2 ) 3 SO 3 − , (CH 2 ) 11 N + Me 2 CH 2 CH 2 OH) are studied. Their aqueous solution properties are strongly influenced by added salts; the surface activity can be modified efficiently by an appropriate choice of ions. The interactions of salts and polyzwitterions observed in solution can be extended to the behaviour in bulk. It enables the preparation of uniform, non crystalline blends containing up to equivalent amounts of inorganic salt and polyzwitterions

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 coexisting polymer solutions in mixed solvents and its correlation with bulk thermodynamics: phase equilibria (liquid/gas…

2002

Abstract Vapor pressures, phase equilibria and interfacial tensions σ were measured for solutions of poly(dimethylsiloxane) (PDMS, M w [equals]75 kg/mol and M n [equals]50 kg/mol) in mixed solvents of toluene (TL) and ethanol (EtOH) at 30, 40, 50 and 60 °C. The experimental ternary phase diagrams can be modeled quantitatively from the determined concentration and temperature dependent binary interaction parameters χ ij if the experimentally inaccessible composition dependence of χ EtOH/PDMS is adjusted. The relations between σ and the equation of state of the system differ from that applying to single solvents. The exponents as well as the amplitude prefactors of the corresponding scaling l…

LARGE DEFORMATION CREEP BEHAVIOR OF A SOLID POLYMER.

1981

Abstract The effect of loading rate and strain on the creep behavior after sample yielding has been studied in previous communications (14–15) for Mylar in tension and for Lexan in compression. In this work the creep behavior of Lexan samples previously elongated is considered both in tension and in compression. A procedure which collects all the data independently of both loading rate and initial creep strain is proposed.

Acute prostaglandins and sympathetic activity changes due to amino acids load in essential hypertension

1995

From Food Map to FODMAP in Irritable Bowel Sindrome.

2016

Irritable bowel syndrome (IBS) is one of the most common gastrointestinal diseases in the general population, with a prevalence ranging from 12 % to 30 %, mainly affecting younger patients (i.e., <50 years of age) and women [1]. As in other chronic functional gastrointestinal disorders, abdominal discomfort or pain, abnormal bowel habits, and often bloating and abdominal distension are the main clinical features. Their diagnosis is based on symptom patterns (i.e., the Rome III criteria), which also allow categorization in diarrhea-predominant (D-IBS), constipation-predominant (C-IBS), mixed diarrhea and constipation (M-IBS), and unclassified (U-IBS) IBS [2]. Symptom severity ranges from tol…