Aqueous dispersions of single-wall and multiwall carbon nanotubes with designed amphiphilic polycations

Poor solubility of single-walled and multiwalled carbon nanotubes (NTs) in water and organic solvents presents a considerable challenge for their purification and applications. Macromolecules can be convenient solubilizing agents for NTs and a structural element of composite materials for them. Several block copolymers with different chemical functionalities of the side groups were tested for the preparation of aqueous NT dispersions. Poly(N-cetyl-4-vinylpyridinium bromide-co-N-ethyl-4-vinylpyridinium bromide-co-4-vinylpyridine) was found to form exceptionally stable NT dispersions. It is suggested that the efficiency of macromolecular dispersion agents for NT solubilization correlates with the topological and electronic similarity of polymer-NT and NT-NT interactions in the nanotube bundles. Raman spectroscopy and atomic force and transmission electron microcopies data indicate that the polycations are wrapped around NTs forming a uniform coating 1.0-1.5 nm thick. The ability to wind around the NT originates in the hydrophobic attraction of the polymer backbone to the graphene surface and topological matching. Tetraalkylammonium functional groups in the side chains of the macromolecule create a cloud of positive charge around NTs, which makes them hydrophilic. The prepared dispersions could facilitate the processing of the nanotubes into composites with high nanotube loading for electronic materials and sensing. Positive charge on their surface is particularly important for biological and biomedical applications because it strengthens interactions with negatively charged cell membranes. A high degree of spontaneous bundle separation afforded by the polymer coating can also be beneficial for NT sorting.     

Synthesis and Inhibitory Activity Against Epstein-Barr Virus of Some New 1,2,3,4-Tetrahydropyrimidine-2-thiones

1,2,3,4-Tetrahydropyrimidine-2-thiones 4a–n were synthesized through the reaction of aromatic aldehydes 1a–n , ethyl acetoacetate (2) and thiourea ( 3) . The structures of all newly synthesized heterocyclic compounds elucidated by the use of IR, ¹H NMR, mass spectra, and elemental analyses. The inhibitory activity against the Epstein-Barr Virus early antigen (EBA-VA) of all newly synthesized heterocyclic compounds were evaluated.     

Synthesis and antioxidant activity of some thiazolidin-4-one derivatives

Abstract  4-Fluorobenzaldehyde was used for the preparation of 2-(4-fluorophenyl)thiazolidin-4-one derivatives which were allowed to react with chloroacetonitrile and acrylonitrile to produce 3-(2-(4-fluorophenyl)-4-oxothiazolidine3-yl)acetonitrile and 3-(2-(4-fluorophenyl)-4-oxothiazoledine-3-yl)propanenitrile. Biological evaluation of some of the compounds showed that many had promising antioxidant activity. Graphical Abstract        

Rewritable Optical Storage with a Spiropyran Doped Liquid Crystal Polymer Film

Rewritable optical storage has been obtained in a spiropyran doped liquid crystal polymer films. Pictures can be recorded on films upon irradiation with UV light passing through a grayscale mask and they can be rapidly erased using visible light. Films present improved photosensitivity and optical contrast, good resistance to photofatigue, and high spatial resolution. These photochromic films work as a multifunctional, dynamic photosensitive material with a real‐time image recording feature.

     

Theoretical and numerical study of Couette-Taylor flow with an axial flow using lattice Boltzmann method

In this study, the numerical models for swirling flows developed by Li et al and Zhou for lattice Boltzmann method (LBM) are chosen. These models were firstly validated using the Couette-Taylor flow between two concentric cylinders simulations. Numerical results showed the efficiency of the Zhou's model. Numerical simulation results using LBM are in good agreement for the steady and unsteady regimes compared to the literature review. In a second step, the Zhou model was then adopted to our study to determine the Couette-Taylor instabilities with an axial flow. Two protocols are tested. The first one (direct protocol) starts with an azimuthal flow without any axial flow (Re = 0). Once the regime is established, an axial flow is then superposed to the Couette-Taylor flow (with a sudden or a progressive manner). The second protocol (inverse protocol) starts with an axial flow at a given Reynolds number (Poiseuille flow). Once the regime is established, an azimuthal flow is the executed (with a sudden or a progressive manner). The effect of various parameters controlling the physical situation is also discussed. The increase of the azimuthal velocity mainly led to the emergence and development of Taylor vortices. Its influence decreases when the axial Reynolds number increases. The relevant result for this study is the change of the critical axial Reynolds number Re_c (total disappearance of instabilities) with both protocols and both manners.     

Synthesis and Anti-Inflammatory Activities of Some Novel S-Pyridyl Glycosides Derivatives

A series of some new acetylated S-glycosides of pyridine-2-thione derivatives, including D-glucose, D-galactose, D-xylose and L-arabinose derivatives were synthesized. Oxidation of some formed S-glycosides derivatives with H₂O₂ afforded the corresponding sulfones. S-Alkylation of pyridine-2-thione derivatives was performed to furnish the S-acyclo deazauridine derivatives. The entire tested compound showed potent anti-inflammatory activity were potent against edema and in the same time inhibited the prostaglandine formation. It is work mention that all the tested compounds showed high safety margin. The structures of the new synthesized compounds have been proved by IR, ¹ HNMR, mass spectra and elemental analysis.