Molecular Architecture of Multi‐Block Polymer Synthesized in a Dual‐Catalyst Single CSTR

This work aims at deriving analytical solutions for the molecular architecture of multi‐block polymer synthesized in a dual‐catalyst single CSTR. While the relevant equations are developed for homopolymerization, they can easily be extended to copolymerization. Special emphasis is placed on the quantities associated with each catalyst rather than the overall ones. However, if all rate parameters are available, the expressions can be used to calculate the properties of the material made by each catalyst as well as the overall ones under various process conditions. Given the reasonable assumption of large residence time, the solutions are simplified to elucidate the kinetics of chain‐shuttling involving two catalysts. It is shown that systems with low chain‐shuttling ability, if DP^P_n,0 ≠ DP^Q_n,0, may exhibit significant deviation from Flory's most probable distribution. Furthermore, systems with high chain‐shuttling ability produce macromolecules with more uniform architecture and polydispersity index close to 2.

     

Cu(II) complexes with 4-amino-3,5-dimethyl isoxazole and substituted aromatic aldehyde Schiff bases: synthesis,crystal structure,antimicrobial activity,DNA binding and cleavage studies

Three isoxazole Schiff bases 2-((E)-(3,5-dimethylisoxazol-4-ylimino)methyl)-6-methoxyphenol (L¹), 2-((E)-(3,5-dimethylisoxazol-4-ylimino)methyl)-4,6-diiodophenol (L²), 2-((E)-(3,5-dimethylisoxazol-4-ylimino)methyl)-6-bromo-4-chlorophenol (L³), and their Cu(II) complexes [Cu(L¹)₂] (1), [Cu(L²)₂] (2) and [Cu(L³)₂] (3) were synthesized. All the complexes have been characterized by elemental analysis, FT-IR, ESI mass, UV-Visible, ESR, TGA, magnetic moments, and single-crystal X-ray diffraction analysis. Based on analytical data, a square planar geometry is assigned to the Cu(II) complexes with N₂O₂ donors from the Schiff base ligands. The single-crystal X-ray diffraction measurements of 1 and 2 confirmed the square planar geometry. DNA binding studies from electronic absorption titrations, viscosity measurements, and fluorescence quenching studies indicated an intercalation mode of binding of Cu(II) complexes with CT-DNA. DNA cleavage experiments of Cu(II) complexes with supercoiled plasmid pBR322 DNA have also been investigated by agarose gel electrophoresis in the presence of H₂O₂ (oxidative cleavage) and UV light (photolytic cleavage). The synthesized compounds were screened for antibacterial (Escherichia coli, Pseudomonas putida, Klebsiella pneumoniae, Bacillus subtillis and Staphylococcus aureus) and antifungal (Candida albicans and Aspergillus niger) activities by the paper disk method. The Cu(II) complexes showed better activity than corresponding Schiff bases.     

High-Affinity Hybridization of Complementary Aromatic Oligoamide Strands in Water

We prepared a series of water-soluble aromatic oligoamide sequences all composed of a segment prone to form a single helix and a segment prone to dimerize into a double helix. These sequences exclusively assemble as antiparallel duplexes. The modification of the duplex inner rim by varying the nature of the substituents borne by the aromatic monomers allowed us to identify sequences that can hybridize by combining two chemically different strands, with high affinity and complete selectivity in water. X-ray crystallography confirmed the expected antiparallel configuration of the duplexes whereas NMR spectroscopy and mass spectrometry allowed us to assess precisely the extent of the hybridization. The hybridization kinetics of the aromatic strands was shown to depend on both the nature of the substituents responsible for strand complementarity and the length of the aromatic strand. These results highlight the great potential of aromatic hetero-duplex as a tool to construct non-symmetrical dynamic supramolecular assemblies.     

An unusual one step synthesis of acetylenes

Substituted nitrostyrenes on reaction with H₂O₂/NEt₃ give 1,2 diaryl acetylenes in ~ 30 % yield.     

Flow of a viscous incompressible fluid between two parallel plates,one in uniform motion and the other at rest with uniform suction at the stationary plate

In the present paper an exact solution of the Navier-Stoke’s equations reduced to third and second order non-linear differential equations with appropriate boundary conditions is obtained. The longitudinal and transverse velocity profiles for λ=0·1, 1 and R=100 are drawn. It is noted that for large values of\(\bar x\), an adverse pressure gradient is developed which causes a back flow. There is increase in pressure even for very small fluid suction along the stationary plate. The skin friction and the flow coefficient decrease with reference to the suction velocity and the distance along the stationary plate. For λ=0, the results transform to the known results for plane couette flow without suction.