A study of some equation‐of‐state parameters of poly(methylhydrosiloxane‐co‐dimethylsiloxane) with some solvents by gas chromatography

Trace amount of methyl acetate, ethyl acetate, tert‐butyl acetate, pentane, hexane, and heptane were passed through the chromatographic column loaded with poly(methylhydrosiloxane‐co‐dimethylsiloxane) coated on Chromosorb W. The retention diagrams of the solvents on the copolymer were plotted by means of specific retention volumes at temperatures between 40 and 80°C by inverse gas chromatography technique. In this study, some thermodynamic interaction parameters such as Flory–Huggins polymer–solvent interaction parameter, equation‐of‐state polymer–solvent interaction parameter, effective exchange energy parameter, and weight fraction activity coefficients at infinite dilution of the solvent were determined. Then, the exchange enthalpy parameter and entropy parameter were determined by using a relation for the enthalpy interaction parameter of the equation‐of‐state theory, which is arranged for the inverse gas chromatography conditions. Later, the partial molar heat of sorption and the partial molar heat of mixing were obtained. The solubility parameter of this copolymer was determined as 6.64 (cal/cm³)^1/2 at room temperature. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 1627–1631, 2007     

Scalable fabrication of high-performance graphene/polyamide 66 nanocomposites with controllable surface chemistry by melt compounding

Scalable and ease fabrication of high-performance graphene reinforced polyamide 66 (PA66) nanocomposites by melt-mixing were achieved by selecting ideal graphene reinforcement having high C/O ratio. In this study, single-layer amine functionalized reduced graphene oxide and multi-layer thermally exfoliated graphene oxide (TEGO) were used to investigate the influence of surface chemistry and dispersion state on crystallization behaviors, mechanical, and thermal properties of graphene reinforced PA66 nanocomposites. Both types of graphenes acted as nucleating agent but TEGO showed the better performance due to its intercalated structure formation mechanism and efficient viscous flow during melting. Mechanical results indicated that 0.5 wt% TEGO based PA66 nanocomposite showed the highest tensile properties by increasing tensile modulus and tensile strength up to 45% and 16.1%, respectively. In addition, TEGO reinforced nanocomposites showed more stable viscoelastic behavior by reaching a plateau at high temperatures and restraining long-range motion of polymer chains.     

Polymerization of pyrrole derivatives on polyacrylonitrile matrix,FTIR–ATR and dielectric spectroscopic characterization of composite thin films

Oxidative polymerization of acrylonitrile (AN) initiated by Ce(IV)–oxalic acid redox system in the aqueous medium was performed and polyacrylonitrile (PAN)/polypyrrole (PPy) composite thin films were prepared by polymerization of pyrrole on polyacrylonitrile matrix. Effect of concentration of pyrrole derivatives on the resulting polymeric film properties was investigated. The influence of the pyrrole derivative type and content on the dielectric permittivity, dielectric loss and electrical properties of the composite films were analyzed in the frequency range from 0.05 Hz to 10 MHz. For a selected concentration of 200 μl of composite films at 10⁷ Hz, the conductivity was found to be in the following order: PAN–PPy < PAN–PNMPy < PAN–PNPhPy. Dielectric constant increase of the composite films was more obvious when the quantity of n-phenyl pyrrole was increased. A linear relationship was observed between the absorbances (FTIR–ATR) and conductivities (dielectric spectroscopy).     

Effect of Applied Current Density on Morphological and Structural Properties of Electrodeposited Fe-Cu Films

A detailed study has been carried out to investigate the effect of applied current density on the composition, crystallographic structure, grain size, and surface morphology of Fe-Cu films. X-ray diffraction (XRD) results show that the films consist of a mixture of face-centered cubic (fcc) Cu and body centered cubic (bcc) α-Fe phases. The average crystalline size of both Fe and Cu particles decreases as the applied current density becomes more negative. Compositional analysis of Fe-Cu films indicates that the Fe content within the films increases with decreasing current density towards more negative values. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) have been used to investigate the surface morphology of Fe-Cu films. It is observed that the surface morphology of the films changes from dendritic structure to a cauliflower structure as the applied current density becomes more negative. The surface roughness and grain size of the Fe-Cu films decrease with decreasing applied current density towards more negative values.     

Monitoring IP multicast in the internet: recent advances and ongoing challenges

Multicast was one of the first "value-added" services to be developed and deployed in the Internet. In evaluating the success of multicast, if ubiquitous deployment has been the goal, multicast has not been successful. However, if widespread use of multicast as a bandwidth-saving technique has been the goal, multicast has indeed been successful. Upon closer investigation, one of the reasons for only partial success is a lack of support for service management. Multicast is particularly hard to manage interdomain where it has been less successful, but easier to manage within a domain where network administrators have more control and smaller networks to manage. In this article we survey some of the recent service management efforts, efforts that have been successful intradomain, but fall short for interdomain. In particular, we focus on important topics like monitoring multicast reachability between sources and receivers; understanding the different challenges and solutions between inter- and intradomain service management; and surveying existing solutions to determine whether multicast capability exists on an end-to-end path. Our investigation shows that while not much attention was initially given to multicast service management, more recent efforts have been successful at developing good solutions and tools.