Engineering of a Biomimetic Interface between a Native Dental Tissue and Restorative Composite and Its Study Using Synchrotron FTIR Microscopic Mapping

The aim of this work is to develop a biomimetic interface between the natural tooth tissue and the restorative composite and to study it on the basis of synchrotron micro-FTIR mapping and multidimensional processing of the spectral data array. Using hierarchical cluster analysis of 3D FTIR data revealed marked improvements in the formation of the dentine/adhesive/dental hybrid interface using a biomimetic approach. The use of a biomimetic strategy (application of an amino acid–modified primer, alkaline calcium and a nano-c-HAp–modified adhesive) allowed the formation of a matrix that can be structurally integrated with natural dentine and dental composite. The biomimetic hybrid layer was characterised by homogeneous chemical composition and a higher degree of conversion of the adhesive during polymerisation, which should provide optimal integration of the dental composite with the dentine.     

Detection of RDX traces at the surface with sonic aerosol flow desorption

The use of a high-speed aerosol flow is proposed for sampling RDX from the surface followed by chromatographic analysis. The aerosol is generated from different solvents by means of a coaxial nebulizer. The effect of the aerosol flow parameters (solvent flowrate, an angle of the nebulizer inclination with respect to the surface) and various solvents (water, acetone, and hexane) on the efficiency of the RDX desorption was investigated. The optimal angle of the nebulizer was found to be 30°, under these conditions, the desorption of RDX from the surfaces of different structure (metal, glass, leather, cotton fabric, and paper) has also been studied. It is shown that under the action of an aerosol created using water and acetone, desorption from a smooth surface occurs most efficiently (1.5 times higher than with hexane). In this case, the sample removes almost completely (about 80%) by the aerosol flow in a few seconds. A relationship between the desorption efficiency and the amount of the solvent sprayed (that is the amount of aerosol particles in desorbing flow) has a characteristic maximum which location depends on the properties of the solvent spray. This effect is associated with a rate of solvent evaporation. Under optimal conditions for desorption of RDX from a smooth surface using an aqueous aerosol, an LOD of ～10?ng can be achieved. For porous and rough surfaces, the efficiency of the analyte desorption decreases (three times for leather and cotton fabric). The results of the experiments conducted allow one to conclude that the RDX solubility in the solvent used does not affect considerably the efficiency of the RDX desorption. It is assumed that small aerosol drops are very active and can capture the particles of the target analyte. This promotes the desorption of RDX molecules from the surface.

© 2018 American Association for Aerosol Research     

Effects of equal‐channel,multiple‐angular extrusion on the physical and mechanical properties of glassy polymers

Through the examples of polycarbonate and poly(methyl acrylate), the evolution of the structure and properties of glassy polymers processed by equal‐channel multiple‐angular extrusion (ECMAE) were studied. It was demonstrated that ECMAE allowed the substantial improvement of the set of strain–strength characteristics of these materials, regardless of the direction of loading applied. With the use of the data from scanning electron microscopy, differential scanning calorimetry, and dilatometry, we found that the simultaneous growth in the strength, plasticity, and impact resistance was related to the formation of a net of biaxially oriented polymeric chains, the decrease in the free volume, and the reinforcement of intermolecular interaction. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42180.     

Analysis of weakly bonded oxygen in HfO<Subscript>2</Subscript>/SiO<Subscript>2</Subscript>/Si stacks by using HRBS and ARXPS

We have used transmission electron microscopy, high-resolution Rutherford backscattering spectrometry (HRBS), and angle-resolved X-ray photoelectron spectroscopy (ARXPS) to investigate the interfacial oxidized states of hafnium oxide/silicon oxide/Si gate oxide stacks. The atomic concentrations and profiles of HRBS analysis are similar before and after annealing; however, ARXPS shows a clear difference in bond status. These results imply that weakly bonded oxygen atoms existed in the stacks alongside the suboxides. In the as-deposited layers, dioxides are found at the interfaces and suboxides in the layers whereas after annealing suboxides are found at the interfaces and dioxides are found in the layers because of redistribution of bonds during annealing. The combination of HRBS and ARXPS analyses indicated that the main oxidized states transformed from the suboxides to the dioxides with no obvious quantitative difference in the content of oxygen atoms, suggesting that reactions of the weakly bonded oxygen atoms occurred with the suboxides within the layers.     

Charge Migration in Organic Materials: Can Propagating Charges Affect the Key Physical Quantities Controlling Their Motion?

Charge migration is a ubiquitous phenomenon with profound implications throughout many areas of chemistry, physics, biology, and materials science. The long-term vision of designing functional materials with tailored molecular-scale properties has triggered an increasing quest to identify prototypical systems where truly molecular conduction pathways play a fundamental role. Such pathways can be formed due to the molecular organization of various organic materials and are widely used to discuss electronic properties at the nanometer scale. Here, we present a computational methodology to study charge propagation in organic molecular stacks at nano and sub-nanoscales and exploit this methodology to demonstrate that moving charge carriers strongly affect the values of the physical quantities controlling their motion. The approach is also expected to find broad application in the field of charge migration in soft matter systems.     

Molecular Alignment Induced by Ultrashort Laser Pulses and Its Impact on Molecular Motion

Spectroscopy aims at extracting information about matter through its interaction with light. However, when performed on gas and liquid phases as well as solid phases lacking long-range order, the extracted spectroscopic features are in fact averaged over the molecular isotropic angular distributions. The reason is that light–matter processes depend on the angle between the transitional molecular dipole and the polarization of the light interacting with it. This understanding gave birth to the constantly expanding field of “laser-induced molecular alignment”. In this paper, we attempt to guide the readers through our involvement (both experimental and theoretical) in this field in the last few years. We start with the basic phenomenon of molecular alignment induced by a single pulse, continue with selective alignment of close molecular species and unidirectional molecular rotation induced by two time-delayed pulses, and lead up to novel schemes for manipulating the spatial distributions of molecular samples through rotationally controlled scattering off inhomogeneous fields and surfaces.     

Confinement effects on the kinetics of formation of sequential semi-interpenetrating polymer networks

Summary Peculiarities of formation kinetics of sequential semi-interpenetrating polymer networks based on crosslinked polyurethane with different cross-linking density and linear polystyrene and polybutylmethacrylate have been studied. Polyurethane networks were synthesized differing in molecular mass M_c of the chains between cross-links. Monomeric styrene and butyl methacrylate were introduced into these networks by swelling them in monomers up to equilibrium. The kinetics of polymerization of monomers in swollen networks was investigated. The experimental data show the dependence of the kinetic parameters of polymerization on M_c, this dependence being different for various monomers. Sharp discrepancy in molecular mass distribution of polymers formed in various matrices has been observed. The differences in dependencies of reaction kinetics and molecular mass distribution are supposed to be connected to various dependence of the chain growth and termination of various monomers on the density of network, i.e. on the confinements imposed by the intranetwork space.