Ionogels of a Sugar Surfactant in Ionic Liquids

Green and environmentally friendly ionogels formed by a sugar surfactant were prepared in two kinds of imidazolium‐based ionic liquids. The phase transition from ribbon structures to lamellar structures induced by temperature and the transition mechanism were investigated in detail by means of freeze‐fracture TEM and field‐emission SEM observations, as well as small‐angle X‐ray scattering measurements. The rheological properties and tribological properties of two kinds of ionogels were systematically investigated. The difference in the lubricating properties and antiwear capability can be explained well by the mechanical and viscoelastic properties, as well as the different microstructures of samples destroyed by shear forces. This work provides a better understanding of the relationship between the structures, rheological properties, and tribological properties of ionogels.     

Synthesis and photophysical properties of a new amino acid possessing a BODIPY moiety

The synthesis of a new amino acid possessing a BODIPY fluorophore, which is of use in peptide synthesis, is described. The influence of the amino acid as well as of benzoxazole moieties on the BODIPY spectral and photophysical properties is discussed. The photophysical properties of this fluorophore were modified only to a small extent compared to those of the parent compound.     

Combustion-generated nanoparticles produced in a benzene flame: a multiscale approach

This paper details the multiscale methodology developed to analyze the formation of nanoparticles in a manner that makes it possible to follow the evolution of the structures in a chemically specific way. The atomistic model for particle inception code that combines the strengths of kinetic Monte Carlo and molecular dynamics is used to study the chemical and physical properties of nanoparticles generated in a premixed fuel-rich benzene flame, providing atomistic scale structures (bonds, bond angles, dihedral angles) as soot precursors evolve into a three-dimensional structure. Morphology, density, porosity, and other physical properties are computed. Two heights corresponding to two different times in the benzene flame, experimentally studied by Bittner and Howard [Proc. Combust. Inst. 18, 1105 (1981)], were chosen to examine the influence of different environments on structural properties of the particles formed.     

Up-converted emission in a series of phenylazomethine dendrimers with a porphyrin core

The nonlinear optical and time-resolved properties of a series of phenylazomethine-porphyrin dendrimers are reported. The linear optical properties were also investigated, and the efficiency of the energy transfer process was obtained. Measurements were also carried out with the basic building-block molecules. The process of frequency up-converted emission was observed in these porphyrin dendrimers. The mechanism for this effect is investigated and related to the process of "hot-band" absorption in the phenylazomethine-porphyrin system. Time-resolved measurements also suggested efficient intramolecular vibrational energy redistribution in these systems. These properties suggest that the porphyrin dendrimers may also have applications in light harvesting of low-frequency photons, as well as in sensors.     

Functionalization as a way to enhance dispersion of carbon nanotubes in matrices: a review

The past 3 decades of thorough scientific scrutiny of carbon nanotubes (CNTs) revealed that, in spite of their remarkable properties, some technological applications are adversely affected by certain difficulties in handling the CNTs, along with their tendencies, arising out of their graphitic structure, to form agglomerates and exhibit limited interaction with other materials. These issues play a crucial role when CNTs are applied as nanofillers inside matrices, in particular polar ones. In this case, unless several preliminary steps are taken, an efficient and uniform dispersion of the CNTs becomes impossible, thus the nanocomposite cannot exhibit the expected final properties. Unfortunately, a universal procedure does not exist since the problem of the dispersion of CNTs is very complex, and its solution requires an advanced understanding of the properties of the CNTs (e.g. whether the CNTs are single- or multiwalled, size, length, lattice defects etc.) as well as of the matrices used. This review aims to help the reader to select the appropriate dispersion procedure by acquiring fundamental knowledge regarding: (1) the synthesis and properties of pristine CNTs; (2) methods of chemical functionalization and properties of functionalized CNTs; and (3) methodologies for the mechanical dispersion of CNTs. A brief overview regarding chemo-physical characterization techniques is also given to enable a better evaluation of the properties of the CNTs, both before and after functionalization.     

2-Sulfanylhydroquinone Dimer as a Switchable Fluorescent Dye

A new dye was developed, the photoluminescence properties of which are controlled by a chemical reaction. The fluorescence properties of 2-sulfanylhydroquinone dimers depend on the number of hydroxyl groups that are acylated. Unprotected or monoacylated 2-sulfanylhydroquinone dimers displayed good fluorescence properties, whereas diacylated and tetraacylated 2-sulfanylhydroquinone dimers showed dramatically decreased fluorescence. A monomesylated derivative was devised, which shows good fluorescence characteristics as a switching fluorescence dye through a chemical reaction.     

A study of the influence of a new promoter on the adhesion of rubber to a metal cord

A promoter of adhesion of a rubber to a metal cord based on precipitated silica modified by cobalt was developed. The analysis of its qualitative and quantitative composition was carried out. The effect of the obtained compounds on the technological and physico-mechanical properties of filled elastomeric compositions based on synthetic polyisoprene rubber and on the properties of metal cord–rubber systems was studied. It was shown that application of modified precipitated silica allows both making elastomeric compositions cheaper and improving their adhesive properties.     

Physicochemical properties of a microelement fertilizer with amino acids

The physicochemical properties of the initial components and products were studied with the aim of production of a microelement fertilizer with an amino acid concentrate. The physicochemical properties of the amino acid concentrate and its influence on the stability and sorption properties of fertilizers enriched in microelements were studied.     

Mechanical unfolding revisited through a simple but realistic model

Single-molecule experiments and their application to probe the mechanical resistance and related properties of proteins provide a new dimension in our knowledge of these important and complex biological molecules. Single-molecule techniques may not have yet overridden solution experiments as a method of choice to characterize biophysical and biological properties of proteins, but have stimulated a debate and contributed considerably to bridge theory and experiment. Here we demonstrate this latter contribution by illustrating the reach of some theoretical findings using a solvable but nontrivial molecular model whose properties are analogous to those of the corresponding experimental systems. In particular, we show the relationship between the thermodynamic and the mechanical properties of a protein. The simulations presented here also illustrate how forced and spontaneous unfolding occur through different pathways and that folding and unfolding rates at equilibrium cannot in general be obtained from forced unfolding experiments or simulations. We also study the relationship between the energy surface and the mechanical resistance of a protein and show how a simple analysis of the native state can predict much of the mechanical properties of a protein.     

Conformational and electronic properties of a microperoxidase in aqueous solution: a computational study.

A theoretical study of the conformational properties of a small heme peptide in aqueous solution is carried out by classical, long-timescale molecular dynamics simulations. The electronic properties of this species, that is, the relative energies of its excited electronic states and the redox potential, are reproduced and related to the conformational behavior using the perturbed matrix method and basic statistical mechanics. Our results show an interesting coupling between the conformational transitions and the electronic properties. These investigations, beyond the biophysically relevant results addressing the long-standing question of the actual role of the enzyme structure on the enzyme activity, are also of some methodological interest since they offer a further computational perspective for including the electronic degrees of freedom into the modeling of rather complex molecular systems.     

(+)-Usnic Acid as a Promising Candidate for a Safe and Stable Topical Photoprotective Agent

The study aimed to examine whether usnic acid—a lichen compound with UV-absorbing properties—can be considered as a prospective photoprotective agent in cosmetic products. Moreover, a comparison of two usnic acid enantiomers was performed to preselect the more effective compound. To meet this aim, an in vitro model was created, comprising the determination of skin-penetrating properties via skin-PAMPA assay, safety assessment to normal human skin cells (keratinocytes, melanocytes, fibroblasts), and examination of photostability and photoprotective properties. Both enantiomers revealed comparable good skin-penetrating properties. Left-handed usnic acid was slightly more toxic to keratinocytes (IC₅₀ 80.82 and 40.12 µg/mL, after 48 and 72 h, respectively) than its right-handed counterpart. The latter enantiomer, in a cosmetic formulation, was characterized by good photoprotective properties and photostability, comparable to the UV filter octocrylene. Perhaps most interestingly, (+)-usnic acid combined with octocrylene in one formulation revealed enhanced photoprotection and photostability. Thus, the strategy can be considered for the potential use of (+)-usnic acid as a UV filter in cosmetic products. Moreover, the proposed model may be useful for the evaluation of candidates for UV filters.     

Characterization of a new chiral antiferroelectric liquid crystal with a lateral bromo substituent

In this paper we present the characterization of a new chiral mesogen with a lateral bromo substituent. The identification of the various smectic phases is achieved by texture observation, miscibility studies and DSC. The optic and electro-optic properties are also investigated. The real part of the complex dielectric permittivity as a function of the temperature was also measured in the planar geometry for thin samples. The dielectric behaviour will be qualitatively discussed on the simple assumption of different anchorings. These results point out the importance of anchoring conditions in relation to the macroscopic properties observed in very thin cells of antiferroelectric liquid crystals.     

Characterization of a new chiral antiferroelectric liquid crystal with a lateral bromo substituent

In this paper we present the characterization of a new chiral mesogen with a lateral bromo substituent. The identification of the various smectic phases is achieved by texture observation, miscibility studies and DSC. The optic and electro-optic properties are also investigated. The real part of the complex dielectric permittivity as a function of the temperature was also measured in the planar geometry for thin samples. The dielectric behaviour will be qualitatively discussed on the simple assumption of different anchorings. These results point out the importance of anchoring conditions in relation to the macroscopic properties observed in very thin cells of antiferroelectric liquid crystals.     

Nose-Hoover dynamics in a shaker

We introduce a new class of systems based on the Nose-Hoover equations. We show that we can add time-dependent terms without destroying the measure and energy conservation properties of the initial system. These "shakers" are typically pseudoperiodic in time, i.e., depend on a collection of harmonic oscillators. We show by numerical examples that it strengthens the sampling properties of the initial system with respect to the Gibbs measure and helps the computation of averages in the canonical ensemble.     

Chemical modification of a polyacrylamide: Enhanced decontamination of soils and surfaces after a nuclear accident

This contribution concerns the decontamination of soils and surfaces polluted by cesium and strontium after a nuclear accident. The decontamination rate by means of an industrial polyacrylamide previously selected for its mechanical covering properties is studied. The characteristics of the polymer and its cation-exchange capacity (CEC) are specified. The chemical modification of the polymer, involving a crosslinking path and functional grafting, affords an improvement of its decontaminating properties.     

A dendronized polymer is a single-molecule glass

The molecular architecture of dendronized polymers can be tuned to obtain nanoscale objects with desired properties. In this paper, we bring together experiments and computer simulations to study the thermodynamic and dynamic properties of a single dendronized polymer chain. We find that, upon changing certain architectural features, dynamic correlations characterizing backbone conformational fluctuations of a dendronized polymer exhibit dynamics akin to glass-forming bulk liquids. Thus, a dendronized polymer chain is a novel macromolecule that is a single-molecule glass. Over a range of conditions that lead to glassy dynamics, there does not appear to be any thermodynamic singularities. We discuss how a dendronized polymer is a molecular system that can directly test different models of glassy dynamics. We also show that defect densities characteristic of typical synthesis conditions do not alter the material properties of dendronized polymers.     

Conjugating a cyanine dye to a polymer surface. In search of a monomeric dye in apolar media

Solution and solid-phase syntheses of a cyanine dye conjugated to polystyrene beads (desired for potentially interesting electronic properties) are described.     

Molecular-dynamics simulation of a ceramide bilayer

Ceramide is the simplest lipid in the biologically important class of glycosphingolipids. Ceramide is an important signaling molecule and a major component of the strateum corneum layer in the skin. In order to begin to understand the biophysical properties of ceramide, we have carried out a molecular-dynamics simulation of a hydrated 16:0 ceramide lipid bilayer at 368 K (5 degrees above the main phase transition). In this paper we describe the simulation and present the resulting properties of the bilayer. We compare the properties of the simulated ceramide bilayer to an earlier simulation of 18:0 sphingomyelin, and we discuss the results as they relate to experimental data for ceramide and other sphingolipids. The most significant differences arise at the lipid/water interface, where the lack of a large ceramide polar group leads to a different electron density and a different electrostatic potential but, surprisingly, not a different overall "dipole potential," when ceramide is compared to sphingomyelin.