Physical and conductivity properties of poly (vinyl chloride) ionomers

Poly (vinyl chloride)(PVC) is a cheapest plastic. Importance of PVC based ionomer has been gradually being popularizing due to compatibility of PVC with a number of salts to replace polyethylene oxide based ionomer. Under present investigation few of chloride group of PVC chain have been replaced by basic thiouronium group and these thiouronium groups are further oxidized to sulfonate group. Introduction of thiouronium group in PVC is confirmed through FTIR and further its oxidation to sulfonate group is also confirmed by FTIR. Conductivity in different stoichiometric ratio of PVCTU and PVCSO₃H was studied and found that PVCTU: PVCSO₃H in 1:1 ratio has conductivity near to pure PVC (10⁻⁹ Ohm-1 cm⁻¹) and increases with proportion of PVCSO₃Na in the mixture (10⁻⁶ Ohm⁻¹ cm⁻¹) for pure PVC, PVCTU has less conductivity not much significant.     

Asymmetric metal-insulator transition in disordered ferromagnetic films

We present experimental data and a theoretical interpretation of the conductance near the metal-insulator transition in thin ferromagnetic Gd films of thickness b ≈ 2-10 nm. A large phase relaxation rate caused by scattering of quasiparticles off spin-wave excitations renders the dephasing length L(?) ? b in the range of sheet resistances considered, so that the effective dimension is d = 3. The conductivity data at different stages of disorder obey a fractional power-law temperature dependence and collapse onto two scaling curves for the metallic and insulating regimes, indicating an asymmetric metal-insulator transition with two distinctly different critical exponents; the best fit is obtained for a dynamical exponent z ≈ 2.5 and a correlation (localization) length critical exponent ν- ≈ 1.4 (ν+ ≈ 0.8) on the metallic (insulating) side.     

Why is less cationic lipid required to prepare lipoplexes from plasmid DNA than linear DNA in gene therapy?

The most important objective of the present study was to explain why cationic lipid (CL)-mediated delivery of plasmid DNA (pDNA) is better than that of linear DNA in gene therapy, a question that, until now, has remained unanswered. Herein for the first time we experimentally show that for different types of CLs, pDNA, in contrast to linear DNA, is compacted with a large amount of its counterions, yielding a lower effective negative charge. This feature has been confirmed through a number of physicochemical and biochemical investigations. This is significant for both in vitro and in vivo transfection studies. For an effective DNA transfection, the lower the amount of the CL, the lower is the cytotoxicity. The study also points out that it is absolutely necessary to consider both effective charge ratios between CL and pDNA and effective pDNA charges, which can be determined from physicochemical experiments.     

Beyond Charge Balance: Counter‐Cations in Polyoxometalate Chemistry

Polyoxometalates (POMs) are molecular metal‐oxide anions applied in energy conversion and storage, manipulation of biomolecules, catalysis, as well as materials design and assembly. Although often overlooked, the interplay of intrinsically anionic POMs with organic and inorganic cations is crucial to control POM self‐assembly, stabilization, solubility, and function. Beyond simple alkali metals and ammonium, chemically diverse cations including dendrimers, polyvalent metals, metal complexes, amphiphiles, and alkaloids allow tailoring properties for known applications, and those yet to be discovered. This review provides an overview of fundamental POM–cation interactions in solution, the resulting solid‐state compounds, and behavior and properties that emerge from these POM–cation interactions. We will explore how application‐inspired research has exploited cation‐controlled design to discover new POM materials, which in turn has led to the quest for fundamental understanding of POM–cation interactions.     

Foldamers to Nanotubes: Influence of Amino Acid Side Chains in the Hierarchical Assembly of α,γ4‐Hybrid Peptide Helices

Supramolecular assembly of various artificially folded 12‐helical architectures composed of γ⁴‐Val, γ⁴‐Leu and γ⁴‐Phe residues is investigated. In contrast to the 12‐helices composed of γ⁴‐Val and γ⁴‐Leu residues, the helices with γ⁴‐Phe residues displayed unique elongated nanotubular architectures. The elongated nanotube assembly was further explored as a template for biomineralization of silver ions to silver nanowires. A comparative study using an analogous α‐peptide helix reveals the importance of the spatial arrangement of aromatic side chains along the helical cylinder in a 12‐helix. These results suggested that the proteolytically and structurally stable α,γ⁴‐hybrid peptide 12‐helices may serve as a new generation of potential templates in the design of functional biomaterials.     

Synthesis of the Immunodominant Trisaccharide Related to the Antigen From E. COLI O 126

The trisaccharide derivative methyl 2-O-[4,6-di-O-acetyl-3-O-(2,3,4,6-tetra-O-benzyl-α-D-gal-actopyranosyl)-2-deoxy-2-phthalimido-β-D-gluco-pyranosyl]-4,6-O-benzylidene-β-D-mannopyranoside (12) was obtained when 3-O-(2,3,4,6-tetra-O-benzyl-α-D-galactopyranosyl)-4,6-di-Oacetyl-2-deoxy-2-phtha-limido-β-D-glucopyranosyl trichloroacetimidate (8) was allowed to react with methyl 3-O-benzyl-4,6-O-benzylidene-β-D-mannopyranoside (11) in presence of trimethylsilyl triflate. Removal of protecting groups then gave the desired trisaccharide.     

Surface-functionalization of spherical silver nanoparticles with macrocyclic polyammonium cations and their potential for sensing phosphates

The synthesis of aqueous dispersion of spherical, underivatized silver nanoparticles (Ag-NPs) stabilized by macrocyclic polyammonium chlorides (MCPAC), [28]ane-(NH₂ ⁺)₆O₂·6Cl⁻ (28-MCPAC) and [32]ane-(NH₂ ⁺)₈·8Cl⁻ (32-MCPAC), which are evidently anion receptors, is reported. As-synthesized Ag-NPs are characterized by UV-vis spectroscopy and transmission electron microscopy (TEM). The 28/32-MCPAC-stabilized Ag-NPs show the surface plasmon band around 400 nm. The TEM-images show that the particles are spherical and well-dispersed. By tuning the 28/32-MCPAC:Ag-OAc (silver acetate) ratio, nanoparticles with different core diameters ranging from 13 to 8 nm for 28-MCPAC and from 10 to 6 nm for 32-MCPAC can be obtained. The advantage of using MCPAC as stabilizers is that they make the particles functionalized for sensing anions. Thus, the potential of the as-synthesized Ag-NPs for sensing phosphates: H₂PO₄ ⁻ (monobasic phosphate, MBP), HPO₄ ²⁻ (dibasic phosphate, DBP) and PO₄ ³⁻ (tribasic phosphate, TBP) is investigated spectroscopically. Interaction of phosphate ions with macrocyclic polyammonium cations makes the Ag-NPs bare, leading agglomeration. The phosphate-assisted agglomeration of 32-MCPAC-Ag-NPs follow the order TBP > DBP ≫ MBP. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Temperature effect on the adsorption and desorption processes in retinoic acid crystals: An electrical conductivity study

Using electrical conductivity as a probe, the effect of crystal temperature on the process of adsorption and desorption of some chemical vapours on retinoic acid semiconductor has been investigated. It has been observed that a three-stage adsorption process in a sample at low temperature changes over to a two-stage process at higher temperature. Measures of activation energies of adsorption and desorption at different stages have been estimated from kinetic data analysis by using a modified Roginsky-Zeldovich equation.