Search results for "Facta"

Effective recovery of perfluoropolyether surfactants from PVDF and PTFE by supercritical carbon dioxide extraction

2007

Abstract The extraction of ammonium carboxylate perfluoropolyether surfactants from poly(vinylidenefluoride) (PVDF) and poly(tetrafluoroethylene) (PTFE) was performed with supercritical carbon dioxide. When proper conditions in terms of temperature, pressure and flow rate were used, extraction recoveries higher than 90% were obtained. For PVDF (with a concentration of surfactant of 5% w/w), at low pressure (12 MPa) and 40 °C, more than 100 min are necessary to have a quantitative extraction. On the other hand, at higher pressure (20 MPa) a quantitative recovery was obtained after few minutes. A strong influence of the temperature on the extraction recovery was also found. In the case of PTF…

Dispersion Copolymerization of Vinyl Monomers in Supercritical Carbon Dioxide.

2003

The thermally initiated free-radical dispersion copolymerization of methyl methacrylate (MMA) and N,N-dimethylacrylamide (DMA) in supercritical carbon dioxide has been studied in the presence of polysiloxane surfactants. The formation of a stable latex seems to be related to the presence of at least one reactive end group in the surfactant macromolecule, thus suggesting that anchoring of the stabilizer to the surface of the growing polymer particles occurs through chemical grafting. In the case of a molar ratio of DMA to MMA lower than 0.40, microspherical copolymer particles with yields ranging from 81 to 97% were collected from batch polymerizations carried out at 65 °C and 23-28 MPa usin…

Surface Characteristics Control the Attachment and Functionality of (Chimeric) Avidin

2018

The physical adsorption (physisorption) of proteins to surfaces is an important but incompletely understood factor in many biological processes and is of increasing significance in bionanotechnology as well. Avidin is an important protein because of strong avidin–biotin binding, which has been exploited in numerous applications. We have undertaken thorough experimentation on the physisorption of avidin, to chemically different flat surfaces of Si and graphite and also to the curved version of the latter, on multiwalled carbon nanotubes (MWNTs) of different diameters. The difference in the behavior of avidin on Si versus graphite is drastic; on Si, avidin deposits as single globular tetramer…

2D dynamical arrest transition in a mixed nanoparticle-phospholipid layer studied in real and momentum spaces

2015

AbstractWe investigate the interfacial dynamics of a 2D self-organized mixed layer made of silica nanoparticles interacting with phospholipid (DPPC) monolayers at the air/water interface. This system has biological relevance, allowing investigation of toxicological effects of nanoparticles on model membranes and lung surfactants. It might also provide bio-inspired technological solutions, exploiting the self-organization of DPPC to produce a non-trivial 2D structuration of nanoparticles. The characterization of interfacial dynamics yields information on the effects of NPs on the mechanical properties, important to improve performances of systems such as colloidosomes, foams, creams. For thi…

Different Dissolution Media Lead to Different Crystal Structures of Talinolol with Impact on Its Dissolution and Solubility

2003

During the performance of dissolution tests with immediate and controlled-release talinolol tablets it was detected that the type of the buffer used as dissolution medium had a strong influence on the solubility and the dissolution behavior of the drug. It was proven that talinolol appeared in different crystal structures with strongly differing solubilities when pure water, acetate, or phosphate buffers were employed as dissolution media. The resulting crystal structures were characterized by means of light microscopy, differential scanning calorimetry, and X-ray powder diffraction. All methods were adjuvant to detect changes in talinolol crystal structures. The different solubility and di…

Theoretical and experimental evaluation of decypolyglucoside vesicles as potential drug delivery systems

2006

The aim of this work was to ascertain the capability of a commercial mixture of decylpolyglucoside (Orami.x NS10) to form vesicle structures in water, either alone or in association with cholesterol. To this purpose, we compared results obtained from a theoretical model with those acquired from the experimental characterization of different Orami.x NS10/cliolesterol mixtures. The germen vesicular formation theory was used to predict the formation process of vesicular structures. To this purpose, the energy balance involved in the vesicle formation was calculated using critical concentration for vesicle formation (ccf), surface tension and molecular area of decylpolyglucoside. The ccf was me…

Surface Activity of Humic Substances Within Peat Profile

2012

Humic substances are able to reduce the surface tension of their solutions and thus can act as surface-active substances in natural environment and possibly also for industrial applications. The ability to influence the surface tension of humic substance solutions depends on their origin. The objective of this study is a comparison of the ability of humic substances from peat profile to influence the surface tension of their solutions and identification of the structural characteristics of peat humic acids, determining their surfactant properties. Humic acids isolated from peat demonstrated significant impact of the surface tension of their solutions – they act as weak surfactants. The surf…

Surfactant self-assembling in gas phase: positively monocharged sodium alkanesulfonate clusters

2009

Highly recyclable surfactant-based supramolecular eutectogels for iodine removal

2022

In this work, we screened several surfactants for their ability to harden Eutectic Mixtures. We found cetyldiethanolamine-N-oxide as the best candidate, which was able to form eutectogel in four eutectic mixtures. Characterization of the gels obtained in terms of thermal stability, rheology and gelation kinetics, showed a prominent influence of the nature of the hydrogen bonding accepting and donating components for the first two parameter and the other one, respectively. Then, we assessed the eutectogels for their ability to adsorb I2, as a model for its radioactive nuclides, from apolar solvent solutions. The best performing gel allowed fast and thorough removal of I2, over a broad range …

Size influences the effect of hydrophobic nanoparticles on lung surfactant model systems

2013

Item does not contain fulltext The alveolar lung surfactant (LS) is a complex lipid protein mixture that forms an interfacial monolayer reducing the surface tension to near zero values and thus preventing the lungs from collapse. Due to the expanding field of nanotechnology and the corresponding unavoidable exposure of human beings from the air, it is crucial to study the potential effects of nanoparticles (NPs) on the structural organization of the lung surfactant system. In the present study, we investigated both, the domain structure in pure DPPC monolayers as well as in lung surfactant model systems. In the pure lipid system we found that two different sized hydrophobic polymeric nanopa…