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Über dieses Buch

This volume includes 35 contributions to the 24th Conference of the European Colloid and Interface Society which took place in September 2010 in Prague. The contributions from leading scientists cover a broad spectrum of the following topics: • Self-assembling, Stimuli-responsive and Hierarchically Organized Systems • Colloid, Polymer and Polyelectrolyte Solutions; Concentrated Systems and Gels • Thin Films, Interfaces and Surfaces; Wetting Phenomena • Novel Nano-to-Mesostructured Functional Materials • Biologically Important and Bioinspired Systems; Pharmaceutical and Medical Applications

Inhaltsverzeichnis

Frontmatter

Swelling of a Sponge Lipid Phase via Incorporation of a Nonionic Amphiphile: SANS and SAXS Studies

Small-angle X-ray scattering (SAXS) is employed to establish the structure of a self-assembled lipid/water system formed in excess aqueous phase by pharmaceutical-grade glycerol monooleate (GMO). A nonionic guest component (octyl glucoside) is incorporated with the purpose to study the swelling of the structure under full hydration. Small-angle neutron scattering (SANS) is used for characterization of the micellar properties of the octyl glucoside amphiphile and glycerol monooleate. The obtained SAXS and SANS patterns indicate a sponge-type supramolecular organization of the investigated lipid material. Their analysis allows determination of the average cell-cell distances in the bicontinuous bilayer sponge that are essential for the encapsulation of biomolecules and drugs. In the presence of the guest octyl glucoside (OG) the average size of the sponge cells is increased by about 14%. This would be an advantageous feature for the application of sponge-type liquid crystalline carriers as protein drug delivery vehicles, nanostructured bioreactors, and peptide-encapsulating fluid nanomaterials.

Angelina Angelova, Borislav Angelov, Rada Mutafchieva, Vasil M. Garamus, Sylviane Lesieur, Sérgio S. Funari, Regine Willumeit, Patrick Couvreur

pH Induced Desaggregation Of Highly Hydrophilic Amphiphilic Diblock Copolymers

P(

n

BA

20%

-

stat

-AA

80%

)

100

-

b

-PAA

95

, an amphiphilic diblock copolymer consisting of a pure hydrophilic poly(acrylic acid) (PAA) block and a weakly hydrophobic statistical copolymer of

n

-butyl acrylate (

n

BA) and acrylic acid (AA) was prepared by ATRP. Kinetic studies revealed that the polymerization was well controlled, leading to a perfectly defined diblock copolymer both in terms of chemical composition and block lengths. This polymer was characterized in aqueous solution by means of light and neutron scattering experiments. In spite of its weak hydrophobic nature, P(

n

BA

20%

-

stat

-AA

80%

)

100

-

b

-PAA

95

self-assembles in aqueous solution provided the ionization degree of the AA units is kept as low as α = 0-10%. Moreover, the relatively large aggregates (N

agg

= 100, R

h

= 18nm) formed at α = 0% molecularly dissolve at α > 20%. This pH sensitivity is in strong contrast with the behavior of the more hydrophobic P

n

BA

90

-

b

-PAA

100

which forms frozen aggregates insensitive to external stimuli in aqueous solution.

Elise Lejeune, Christophe Chassenieux, Olivier Colombani

The Interaction Parameter in Binary Surfactant Mixtures of a Chelating Surfactant and a Foaming Agent

The micellisation in binary mixed surfactant systems of a chelating surfactant and a foaming agent has been studied by surface tension measurements in order to calculate the interaction parameter (β). 2-dodecyldiethylenetriamine pentaacetic acid, 4-C

12

-DTPA, is an amphoteric chelating surfactant applicable for removing disturbing metal ions from industrial processes, or for heavy metal decontamination of soil or leachate. 4-C

12

-DTPA contains multiple donor atoms and forms very stable coordination complexes with metal ions. The metal complexes can easily be recovered from water by flotation, if the foaming is enhanced by a foaming agent with strong interactions to the chelating surfactant. Two foaming agents were examined, one cationic and one anionic. As expected, strong interactions were found between the negatively charged 4-C

12

-DTPA and the cationic dodecyltrimethylammonium chloride, DTAC. The influence of metal ion chelation, as well as pH, on the interaction parameter was also investigated.

Ida Högberg, Fredrik Andersson, Erik Hedenström, Magnus Norgren, Håkan Edlund

Magnetorheological Elastomer Composites

Smart composites based on carbonyl iron powder, micro and nano size Fe

3

O

4

in ethylene – propylene and acrylonitrile – butadiene rubber were manufactured and studied. Elastomer samples with various volume fractions of magnetic particles were tested. To improve dispersion of applied fillers in polymer matrix, ionic liquids were added during the process of composites preparation. To align particles in elastomer, cross-linking process took place in magnetic field.

Marian Zaborski, Marcin Masłowski

Salt-Induced Behavior of Internally Self-Assembled Nanodrops: Understanding Stabilization by Charged Colloids

We explored the structural effects induced by the addition of salt on lipid-based liquid crystalline drops stabilized in aqueous media by charged sphere-like colloids. This allows us to distinguish two different stabilization regimes. In one case, the internal liquid crystalline phase has the ability to reorganize upon the coalescence of the drops and in the other not. This in turn depends mainly on the contact angle and the internal phase viscosity.

François Muller, Anniina Salonen, Martin Dulle, Otto Glatter

Distribution of Tert-Butylhydroquinone in a Corn Oil/C12E6/Water Based Emulsion. Application of the Pseudophase Kinetic Model

We have determined the distribution of the antioxidant tert-butylhydroquinone, TBHQ, between the oil and interfacial regions of an emulsion composed of stripped corn oil, acidic water and hexaethyleneglycol monododecyl ether, C

12

E

6

, by employing a kinetic method based on the reaction between the hydrophobic 16-hexadecylbenzenediazonium ions, 16-ArN

2

+

, and TBHQ. The kinetic data are interpreted under the light of the pseudophase kinetic model and provide estimates of the partition constant, and hence the distribution, of TBHQ between the oil and the interfacial region of the emulsion. Our results show that more than 80% of TBHQ is located in the interfacial region even at low emulsifier volume fractions, and the fraction of TBHQ in that region increases upon increasing [C

12

E

6

].

María-José Pastoriza-Gallego, Verónica Sánchez-Paz, Laurence S. Romsted, Carlos Bravo-Díaz

Kinetic Studies of Gold Nanoparticles Formation in the Batch and in the Flow Microreactor System

In this study, synthesis of gold nanoparticles (Au NP’s) in the batch and flow reacting systems was carried out either in the presence or in the absence of PVA (polyvinyl alcohol) used as stabilizing agent. As the reductant of gold(III) chloride complex ions, the ascorbic acid was used. To determine the rate equation of the reduction process, the kinetic measurments based on spectrophotometry UV-Vis and DLS were carried out. Consequently, the rate equations of gold(III) complex ions reduction and Au NP’s formation were determined. To synthesize gold nanoparticles in the flow microreactor system the cartridge with T–type geometry of microchannels was used. Next, to calculate the parameters of the flow which enable precipitation of the gold clusters, obtained kinetic equations were applied. This type of microreactor, as well as different reagents flow rates, gave us the chance to inject Au NP’s stabilizer (PVA) at the proper instant of time. It was found that applied method is promising one for the preparation of gold nanoparticles with well defined shape (spheres) and with narrow size distribution (98 % of the Au NP’s with diameter ranged from 1 to 3 nm). Morphology of obtained Au NP’s was characterized using DLS and TEM.

M. Luty-Blocho, K. Pacławski, W. Jaworski, B. Streszewski, K. Fitzner

Influence of the Counterions on the Behaviour of Polyelectrolytes

The influence of the counterions on the hydrodynamic size and the effective charge of poly(styrene sulfonate) has been investigated applying a combination of pulsed-field gradient (PFG) NMR and electrophoresis NMR. From the diffusion coefficient, determined by PFG NMR the hydrodynamic radius as a measure of the size is inferred. Electrophresis NMR yields the electrophoretic mobility and thus the effective charge of the macromolecule. An increased ionic strength of the solution results in a more coiled conformation of the polyelectrolyte, an effect which is more pronounced for bivalent ions. If the dielectric constant of the solution is lowered, the effective charge is reduced as well. The effect on the overall conformation strongly depends on the kind of the counterion. While a small effect is observed for the acid form, the most drastic effect is found for sodium as a counterion.

Ute Böhme, Brigitte Hänel, Ulrich Scheler

Liposome Deformation by Imbalance of pH and Ionic Strength Across the Membrane

The deformation of giant dioleoylphosphatidylcholine (DOPC) liposomes in solution and the properties of DOPC monolayers were investigated by florescence microscopy and surface pressure-area (π-A) isotherm measurements, respectively. These measurements were taken as functions of pH and ionic strength. When the ionic strength was changed from 0.001 to 0.6 at constant pH of 5.6, the coverage of the DOPC monolayer expanded by 10%, and the liposomes formed small protrusions. When the pH was changed from 5.6 to 3.5 at a constant ionic strength of 0.001, the monolayer coverage shrank by 10 %. During this process the external liposome morphology remained the same, but new, smaller vesicles appeared within the interior of the liposomes. Simultaneously changing the pH and the ionic strength to their final values (3.5 and 0.6, respectively), resulted in an expanded monolayer and produced long, protruded liposomes. Our results suggest that the deformation of liposomes is not only driven by osmotic pressure but also the condensed states in each monolayers composing liposome membrane.

Osami Kuroda, Hiroshige Seto, Takayuki Narita, Michio Yamanaka, Yushi Oishi

Surface Charge and Conductance in Dispersions of Titania in Nonaqueous and Mixed Solvents

The nature and speciation of ions, and their affinities to mineral surfaces are well-known for aqueous solutions, and less well-known for mixed water-organic and nonaqueous solutions. Weak acids show strong preferential adsorption of anions on titania, and support a high negative surface charge on titania particles in organic solvents in spite of the very low degree of dissociation of these acids. The interaction between solutions of weak acids in organic solvents and titania particles results in enhanced electrical conductance with respect to the original solutions (in the absence of titania). This phenomenon is explained in terms of surface-induced electrolytic dissociation of weak acids. In mixed water-organic solvents the conductance behavior gradually shifts from water-like behavior (titania depresses the conductance) to opposite behavior (titania enhances the conductance). A quantitative model was proposed to explain the complex effect of the electrolyte and titania concentration on the conductance of the dispersion and zeta potential of the particles.

M. Kosmulski, P. Dahlsten, P. Próchniak, J. B. Rosenholm

Self-Assembled Structures of Disc-Like Colloidal Particles

Self-assembly is an important phenomenon that leads to formation of interesting and novel structures in colloidal dispersions. We present experimental evidence for the existence of a ‘cubatic’ phase in a colloidal dispersion of disc-like particles of nickel hydroxide colloidal dispersions. In this structure, disc-like particles self-assemble as domains of a few parallel discs and the orientation tends to be orthogonal in adjacent domains. This phase has been predicted previously by computer simulations. The domains are approximately equiaxial and are predicted to exist only within a limited range of aspect ratios and volume fractions. We have used the real space technique of cryo-transmission electron microscopy in our studies as this locally ordered structure could not be identified readily using scattering techniques, since the patterns are expected to be similar to those of isotropic liquid phases.

S. Junaid S. Qazi, Göran Karlsson, Adrian R. Rennie

Multi-Bridging Polymers. Synthesis and Behaviour in Aqueous Solution

We synthesized novel hydrophobically end-capped poly(N,N-dimethylacrylamide) (PDMA) star polymers of variable functionality by the RAFT procedure. The properties of these polymers in aqueous solutions were characterised by means of DLS, SANS, and rheology measurements. It was observed that they form interconnected aggregates with a correspondingly increased viscosity. Although the static structure of these systems does not depend to a larger extent on the number of hydrophobic stickers per polymer, the dynamic properties and in particular the rheological properties vary substantially with the number of arms. An increase of non-diffusive relaxation with increasing number of arms is observed by DLS and this complex dynamic behaviour is correlated to an increase of the elastic properties of the formed aggregate networks.

P. Malo de Molina, C. Herfurth, A. Laschewsky, M. Gradzielski

Analysis and Prediction of Cluster Formation

An experimental and theoretical analysis of the interaction of titanium dioxide particles during coagulation was performed, using laser light dynamic scattering (LDS) and both von Smoluchowski and reversible coagulation approaches. For cluster formation, different initial particle numbers and different shear rates were investigated and the experimental data were fitted to a mathematical model based on aggregation and disaggregation processes. The primary particle size was less than 1 micrometre, but in all cases the LDS information showed that primary clusters of 3.5 micrometres were rapidly formed, which then went on to cluster further to provide larger aggregates. Hence, the modelling approach was one of cluster-cluster aggregation and disaggregation, rather than primary particle aggregation.

B. A. Di Giovanni, R. G. Holdich, V. M. Starov

Superhydrophobicity of Self-Assembled PFDTS Nanostructures

The self-assembled formation of PFDTS features on mono- and multilayered silica sphere arrays is studied. The multiscaled roughness induced by PFDTS nanostructures on multilayer arrays gives rise to superhydrophobic behaviour. In contrast to previous work, the role of PFDTS is two-fold: it lowers the surface energy and simultaneously provides the essential roughness to achieve superhydrophobicity. The importance of water in the formation of the nanostructured surfaces is discussed.

M. A. Raza, E. S. Kooij, A. van Silfhout, B. Poelsema

A Facile Colloidal Route for Superhydrophobic Films with Hierarchical Roughness

We present a simple bottom-up colloidal route towards the manufacture of hierarchical substrates. Owing to the double length scale roughness, these super-structure arrays exhibit superhydrophobic wetting behaviour, characterized by large contact angles, limited hysteresis and small sliding angles. The assembly procedure of the nanocolloidal silica and gold particles is reviewed, as well as the chemical treatments required to obtain stable, reproducible substrates.

M. A. Raza, E. S. Kooij, A. van Silfhout, B. Poelsema

Enhanced Keratinocyte Cell Attachment to Atelocollagen Thin Films Through Air and Nitrogen Plasma Treatment

Collagen films (Atelocollagen from bovine Achilles tendon) were prepared in tissue culture dishes and their surfaces were modified by using air and nitrogen plasma treatment. The treated samples were characterised by surface probe techniques including attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR), scanning electron microscopy imaging (SEM) and X-ray photoelectron spectroscopy (XPS). In addition, human immortalised non-tumorigenic keratinocyte cell line (HaCaT) was seeded on the treated and untreated films and cell proliferation was measured by using MTT assay test. The characterisation results confirmed physical and chemical changes on the collagen surface, such as increase in the extent of surface oxidation and surface roughness as well as, the treated samples showed better cell growth than untreated ones, and therefore this approach may be taken into account in the development of promising materials for tissue regeneration applications.

Jorge López García, Jiří Pacherník, Marián Lehocký, Ita Junkar, Petr Humpolíček, Petr Sáha

Adsorption of Poly(Acrylic Acid)-Graft-Poly(Ethylene Glycol) on Polyelectrolyte Multilayers

Graft copolymers PAA-g-PEG with poly(acrylic acid) (PAA, 200 kDa) backbone and poly(ethylene glycol) (PEG, 5 kDa) side chains with grafting ratios g = 5, adsorbed on stainless steel surfaces, were studied using FTIR-ATR spectroscopy. The amount of adsorbed PAA-g-PEG could strongly be increased with a polyelectrolyte multilayer (PEM) as an interlayer. Two independent calibration methods were used to calculate PEG chain areal densities σ

PEG

or effective thickness values d = σ

PEG

·n

EG

/ ρ

EG

(n

EG

: number of EG units in the chain, ρ

EG

: assumed volume density of EG units) of the PEG component. With a suitable PEM interlayer a thickness of d = 34 nm, close to the theoretical length of a helical PEG chain with 114 EG units (32 nm), was obtained. In PEM-PEG coatings with appreciable contents of PEG, the dominance of vibrational bands with transition dipole moments parallel to the axis of helical PEG chains indicates that most PEG helices are oriented vertically on the substrate.

Claus-Peter Klages, Sven Hartwig, Hannah Schmolke

Phase Separation for Langmuir Monolayer in Binary System Based on a π-A Isotherm Measurement

The mixing behavior of binary monolayer of fatty acid was investigated on the basis of π-A isotherm measurements. The (palmitic acid(C

16

)/arachidic acid(C

20

)) and (C

20

/lignoceric acid(C

24

)) mixed monolayers were in a miscible state, whereas the (C

16

/C

24

) mixed monolayer was an immiscible state. The (C

16

/behenic acid(C

22

)) and (stearic acid(C

18

)/C

24

) mixed monolayers were in an incomplete miscible state. The dependence of mixing behavior on the difference in the number of methylene group between components in monolayer is probably due to an enthalpic contribution based on the difference in cohesive energy between the monolayer components.

Miyuki Kuramori, Takamasa Ishikawa, Takayuki Narita, Yushi Oishi

Rheological Behavior of Interfacial Layers Stabilized by Gelatin with Lecithin

The effect of lecithin (natural surfactant) addition to gelatin on the surface rheological properties of the water/heptane interfacial layer and emulsion films formed by these liquids was studied. It was found that the gelatin/lecithin mixtures form complexes in the aqueous phase. Self-assembly of these complexes leads to the formation of viscoelastic interfacial adsorption layers characterized by a yield stress and elastic modules that provide stability of the emulsion films and emulsion systems. The above mentioned parameters evolve in time, though the formation of equilibrium interfacial layers proceeds during several hours; emulsion bilayer films require only several minutes.

S. R. Derkach, S. M. Levachov, T. A. Dyakina, L. A. Petrova

Computer Simulations of Quasi-Steady Evaporation of Sessile Liquid Droplets

Instantaneous distribution of mass and thermal fluxes inside and outside of an evaporating sessile droplet is considered using computer simulations. The latter distribution is calculated in a self consistent way by considering an interconnected problem of vapour transfer in the vapour phase outside the droplet; heat transfer in vapour, liquid and solid substrate; and Marangoni convection inside the liquid droplet. The influence of thermal conductivity of the solid support on the evaporation process is evaluated. The deduced dependences of instantaneous fluxes can be applied for self-consistent calculations of time evolution of the evaporation processes of sessile droplets.

S. Semenov, V. Starov, R. G. Rubio, M. G. Velarde

FTIR ATR Study of Adsorption of Trisiloxanes and Hydrocarbon Surfactants at Hydrophobic Solids from Aqueous Solutions

Kinetics of the integrated absorbance in C−H stretch region for ethoxylated trisiloxane and alkyl polyethoxylate surfactants on low- and highly hydrophobic surfaces has been measured by Fourier-Transform Infrared spectroscopy (FTIR) in the attenuated total reflection (ATR) mode. It has been found that regardless of the surface energy of substrate the absorbance of trisiloxanes continuously increases during the experiment (characteristic time scale is ten minutes), while the absorbance of alkyl polyethoxylate surfactants reaches equilibrium for tens of seconds on low hydrophobic and for a few minutes on the highly hydrophobic surfaces. The continuous growth of absorbance with increasing bulk concentration of surfactants has been detected in the case of trisiloxanes on both substrates even at concentrations above critical wetting concentration; while hydrocarbon surfactants attained the constant values of absorbance at concentrations above critical aggregation concentration. The results for alkyl polyethoxylate surfactants obtained from FTIR-ATR spectra are consistent with the results obtained by other authors used neutron and optical reflectometry. Influence of the length of hydrophilic chains on the value of the absorbance of surfactants has been analyzed. In the case of alkyl polyethoxylate surfactants the absorbance decreases with increasing the length of hydrophilic ethoxy groups. However, in the case of trisiloxane surfactants studied the above trend cannot be clearly traced. Some aspects associated with the relationship between adsorption of trisiloxanes at hydrophobic solid/liquid interfaces and spreading kinetics are discussed.

Boris Bezuglyi, Natalia Ivanova, Victor Starov

Effectiveness of Polymer Sheet Layer to Protect Hydrogel Dressings

Two kinds of polymer sheet layers: breathable film (BF) and breathable laminate (BL) were chosen to cover hydrogel dressings (PVP-CMC and PVP-CMC-BA). The upper and lower surfaces of the polymer sheets were designated as BF (U) and BF (L) for BF and BL (U) and BL (L) for BL, respectively. Water vapor transmission (WVT) test reveals that both BL and BF have oxygen diffusion property, i.e. they are breathable. Microbial penetrability test shows that BF has more resistant property against microbial penetrability. Moisture retention capability proves that polymer sheets effectively reduce the tendency of rapid moisture loss from the hydrogels. According to all the results BF could be considered as more effective layer to protect the properties of hydrogel dressings.

Niladri Roy, Nabanita Saha, Takeshi Kitano, Eva Vitkova, Petr Saha

Membrane Affinity of New Antitubercular Drug Candidates Using a Phospholipid Langmuir Monolayer Model and LB Technique

Tuberculosis is a major problem throughout the world causing 1.9 million deaths annually, and induces a major global public health problem. The pathogen responsible for the disease is

Mycobacterium tuberculosis

. Drug candidates expected to be specific inhibitors of dUTPase an essential enzyme of

Mycobacterium tuberculosis

were identified

in silico

. A phospholipid Langmuir monolayer formed at the liquid/air interface as a simple but versatile model of the cell membrane was applied to assess the membrane affinity of the drug candidates. The interaction of three different potential drug molecules TB501, TB502, and TB505 with lipid monolayer was characterised by tensiometry, and atomic force microscopy at different temperatures. The degree of penetration of drug candidates into the lipid film and the structural variation of drug penetrated lipid films revealed by atomic force microscopic images were compared.

D. Schnöller, Cs. B. Pénzes, K. Horváti, Sz. Bősze, F. Hudecz, É. Kiss

Scattering from Dilute and Lamellar Phase Solutions of Aerosol-OT Simultaneous Probe of Surface Structures and Bulk

The benefits of simultaneous studies of adsorbed layers and bulk structures are shown for solutions of the surfactant Aerosol-OT. Above the critical micelle concentration, Aerosol-OT forms an aligned lamellar phase at the sapphire/solution interface which is in equilibrium with a bulk phase that consists of coexisting micellar solution and dispersed lamellar phase. Measurements of the aligned surface layers and the bulk scattering from a 2 % wt solution by grazing incidence and small-angle neutron scattering show that the bulk consist of lamellar structures with the same

d

-spacing as seen at the surface but without the surface induced alignment. The surface lamellar structure corresponds to a 10 % volume fraction for a 2 % wt bulk which implies that there must be coexistence of regions of different concentration. Scattering patterns measured in grazing incidence geometry clearly show the relative contributions from small-angle scattering and specular reflectivity.

Maja S. Hellsing, Adrian R. Rennie, Lionel Porcar, Carl-Johan Englund

The Effect of Chemical Modification on Mechanical Properties of Carbon Black Filled Elastomer

The aim of the work was to modify the acrylonitrile-butadiene rubber (NBR) in order to improve mechanical properties by enhancing filler-polymer interactions. Following compounds were used as the coupling agents: 2-isopropenyl-2-oxazoline (OKS), 1-allyl-3-methylimidazolium chloride (AMC), 1-vinyl-2-pyrrolidinone (NWP). Two types of carbon black were used as a reinforcing filler: pigment black FW200 and FEF N550. The fillers were characterized by dibutylphtalate (DBP) absorption analysis, aggregates size, rheological properties of filler suspensions and zeta potential analysis. The compounding was carried out in a laboratory rolling mill. Samples were prepared through the vulcanization process at 160°C. The vulcanization kinetics of rubber compounds, crosslink density and mechanical properties of vulcanizates were also measured.

Tomasz Pingot, Martyna Pingot, Marian Zaborski

Nanostructured Metal Oxide and Unsaturated Acid as a New Co-agent in Peroxide Cross-Linking of Hydrogenated Butadiene-Acrylonitrile Rubber

Blends of hydrogenated butadiene-acrylonitrile rubber (HNBR) with nanostructured metal oxides: magnesium oxide (MgO), calcium oxide (CaO), zinc oxide (ZnO) and unsaturated acids: monoallyl maleate (MM) or acrylic acid (AA), as co-agents, were prepared. Dicumyl peroxide (DCP) was used as a vulcanizing agent. The rheometrical properties of rubber mixes and cross-link density of vulcanizates were measured. Mechanical properties of the samples were investigated. Agglomeration degree of metal oxides in the elastomer matrix was also studied by SEM images. It was found that the addition of new co-agents improves the cross-link density and tensile strength of elastomer composites. The obtained elastomer networks consist of covalent bonds and ionic bonds. To conclude, we discovered new type of elastomeric material, cured with high efficiency by dicumyl peroxide and revealing good mechanical properties.

Martyna Pingot, Tomasz Pingot, Marian Zaborski

Effect of Ionic Liquids on the Mechanical Properties of Methylvinylsilicone Rubber

The influence of hydrophobic ionic liquids on cross-link density, mechanical properties, hysteresis and relaxation rates of the methylvinylsilicone rubber vulcanizates were investigated. Imidazolium salts with bromide, chloride and hexafluorophosphate groups were applied, resulting in shortening of the rubber vulcanization time, as well as decrease of the torque increment during cross-linking. Their presence reduced crosslinks decomposing under the influence of ammonia vapour. The most significant changes of methylvinylsilicone rubber properties were observed in a case of ionic liquid with 1-methyl-3-octylimidazolium cation and hexafluorophosphate anion.

Anna Strąkowska, Marian Zaborski

A Simulation Study on the Structure of Bimetallic Nanoparticles Synthesized in Microemulsions

Monte Carlo simulations were carried out to study the different structures showed by bimetallic nanoparticles synthesized in microemulsions. It is observed that the difference in reduction rates of both metals is not the only parameter to determine the metals segregation, playing the interdroplet channel size a relevant role. The reduction rates difference determines nanoparticle structure only in two extreme cases: when both reactions take place at the same rate a nanoalloy structure is always obtained; if both reactions have very different rates, the nanoparticle shows a core-shell structure. But in the large interval between both extreme cases, the nanoparticle structure is strongly dependent on the intermicellar exchange, which is mainly determined by the surfactant film flexibility, and on reactants concentration. This result is very promising for the preparation of bimetallic nanoparticles with a given structure.

M. de Dios, F. Barroso, C. Tojo

Preparation of Porous Magnetic Nanocomposite Materials Using Highly Concentrated Emulsions as Templates

Iron oxide nanoparticles (NPs) with a size of 3 and 10 nm were used to prepare porous hybrid magnetic nanocomposite materials via polymerization in highly concentrated water-in-oil (w/o) emulsions. The NPs were dispersed in a monomer mixture (styrene-divinylbenzene), which was then polymerized to obtain porous solid monoliths with embedded magnetic nanoparticles. The NPs were characterized using x-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The results showed that the nanocomposites contain a high pore volume fraction, with pores of size around 1-10 μm, surrounded by thin polymer walls containing homogeneously distributed nanoparticles. Porous nanocomposites can be attracted to a strong permanent magnet.

G. Ghosh, A. Vílchez, J. Esquena, C. Solans, C. Rodríguez-Abreu

2-Mercaptobenzothiazole as a Corrosion Inhibitor in Low Temperature Ionic Liquids

The corrosion of metals (copper, zinc, and plain carbon steel) in dialkylimidazolium tetrafluoroborates depends on the presence of traces of impurities in the ionic liquids. Water, chlorides, and especially simultaneous presence of the both impurities enhances the pitting corrosion of metals. The products of corrosion contain the metal of interest as well as nitrogen, boron, chlorine, fluorine, carbon, and oxygen. The rate of corrosion of metals in both pure and water- and/or chloride-containing tetrafluoroborates can be substantially reduced in the presence of 2-mercaptobenzothiazole. In 0.001 M 2-mercaptobenzothiazole the rate of corrosion drops by 70 % at 25 °C and by 60 % at 200 °C with respect to the corrosion rate in absence of corrosion inhibitor. We speculate that the other derivatives of azoles and thiazoles, which have been successful as corrosion inhibitors in aqueous media, can also be efficient in low temperature ionic liquids.

K. Marczewska-Boczkowska, M. Kosmulski

A Soft Method for Developing Nanostructured Organic Biomaterials

We study new methods for the elaboration of nanoporous biomaterials intended to deliver encapsulated molecules via diffusion. The strategy consists of casting a polylactide biopolymer around templating micelles strictly using soft preparation methods. The micelles are polyion complex micelles prepared from double hydrophilic block copolymers and hydrosoluble polyamines in aqueous solution. We show that when the aqueous solvent is switched to an organic one, the complexes remain stable, although dynamic light scattering measurements show a larger micellar size. The data is compatible with a much extended brush of the micelles in the organic solvent. The study is in progress with the aim to produce porous structures on a nanometric scale by casting biopolymer films around the micellar entities in chloroform.

M. Al Helou, M-A. Guedeau Boudeville, N. Sanson, C. Gérardin, A. Mourchid

Interfacial Tensiometry of Tracheal Aspirate from Infants with Neonatal Respiratory Distress Syndrome

The interfacial properties of tracheal aspirate from infants with untreated neonatal respiratory distress syndrome (NRDS), and NRDS infants after therapy with the exogenous surfactant

Curosurf®

were assessed. The interfacial characteristics of the aspirate (equilibrium surface tension, maximal and minimal surface tension during lateral compression-decompression cycles) were determined with the pendant drop method. Our results show that the tracheal aspirate of infants with untreated NRDS had high equilibrium, maximal and minimal surface tension values. In contrast, the samples from infants, treated with

Curosurf®

, showed lower surface tension values, suggesting that the application of

Curosurf®

improves the composition and the properties of the pulmonary surfactant in the infant lung.

A. Jordanova, A. Tsanova, G. As. Georgiev, D. Chakarov

Micellar and Solvent Effects on Electrochemical Behaviour of Antioxidants

We have carried out an electrochemical study of a number of relevant hydrophilic and hydrophobic antioxidants in the micellar sodium dodecyl sulphate, (SDS), solutions to determine the effects of solvent polarity, acidity and SDS concentration on their diffusion coefficients. Cyclic voltammograms show that both peak currents, i

p

, and peak potentials,

E

p

, are affected by SDS concentration reaching a plateau region where with the further increase in the surfactant concentration

i

p

and

E

p

remain unchanged which indicates the existence of the saturated surfactant adsorption layer on the GC electrode surface. For the hydrophilic antioxidants: ascorbic acid and propyl gallate the diffusion coefficients vary only by a factor of ~0.8-2.0 in the presence of SDS micelles related to their values in the buffer solution due to the fact that they did not associate with the anionic micelles. For their hydrophobic derivatives the diffusion coefficients in the SDS micellar aqueous solution are very low compared to their values in the mixed aqueous-organic solvents. It suggests that in the mixed solvents antioxidant molecules are in a singly dispersed state whereas in the aqueous SDS solution they are strongly incorporated into the micelles.

J. Narkiewicz-Michalek, M. Szymula, C. Bravo-Díaz

Human Erythrocyte Hemolysis Induced by Bioinspired Sugar Surfactants

Hemolytic activity of single-head single-tail nonionic saccharide – derived surfactants (i.e.,

N

-alkanoyl-

N

-methyllactitolamines and

N-

alkyl

-N-

methylaldonylamides) as well as dicephalic (i.e., (

N

-dodecyl-

N,N

-bis[(3-D-aldonylamido)propyl]amines; aldonyl = gluconyl and lactobionyl) and gemini structures (i.e.,

N,N’

-bisdodecyl-

N,N’

-bis[(3-aldonylamide)propyl]ethylenediamines; aldonyl = gluconyl and lactobionyl) were examined and discussed in relation to both their critical micelle concentration (CMC) values, and structural aspects. The red blood cells lysis is found to depend on the surfactants structure and the hydrophobic tail length, as well as to correlate well with the CMC magnitudes.

Kazimiera A. Wilk, Katarzyna Zielińska, Anna Jarzycka, Jadwiga Pietkiewicz

Microemulsions Stabilized by Gemini, Dicephalic and Single-Head Single-Tail Sugar Surfactants as Biologically Important Systems: Hemolytic Activity and Cytotoxic Studies

Influence of oil-in-water microemulsions stabilized by aldonamide – type surfactants on human erythrocytes integrity and human breast cancer MCF-7 cells survival has been investigated. Microemulsion regions were subsequently determined in pseudoternary phase diagrams. The smallest hemolytic and cytotoxic action was exhibited by microemulsions stabilized by gemini surfactants in comparison to their dicephalic and single-head single-tail equivalents.

Katarzyna Zielińska, Jadwiga Pietkiewicz, Jolanta Saczko, Kazimiera A. Wilk

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