Low percolation threshold conductive device derived from a five-component polymer blend

In this work we report on the preparation of a solid, 3D, low percolation threshold conductive device prepared through the control of multiple encapsulation and multiple percolation effects in a 5 component polymer blend system through melt processing. Conductive polyaniline (PANI) is situated in the core of the 5 component continuous system comprised of high-density polyethylene (HDPE), polystyrene (PS), poly(methyl methacrylate)(PMMA) and poly(vinylidene fluoride)(PVDF). In this fashion, its percolation threshold can be reduced to below 5 vol%. The approach used here is thermodynamically controlled and is described by Harkins spreading theory. In this work the detailed morphology and continuity diagrams of binary, ternary, quaternary and finally quinary systems are progressively studied in order to systematically demonstrate the concentration regimes resulting in the formation of these novel multiple-encapsulated morphological structures. Initially, onion-type dispersed phase structures are prepared and it is shown that through the control of the composition of the inner and outer layers the morphology can be transformed to a hierarchical-self-assembled, multi-percolated structure. The influence of a copolymer on selected pairs in the encapsulated structure is also examined. The conductivity of the quinary blend system can be increased from 10⁻¹⁵ S cm⁻¹ (pure HDPE) to 10⁻⁵ S cm⁻¹ at 5 vol% PANI and up to 10⁻³ S cm⁻¹ for 10 vol% PANI. These are the highest conductivity values ever reported for these PANI concentrations in melt processed systems.     

A three-dimensional Monte Carlo model for electrically conductive polymer matrix composites filled with curved fibers

A three-dimensional (3-D) Monte Carlo model is developed for predicting electrical conductivity of polymer matrix composites filled with conductive curved fibers. The conductive fillers are modeled as a 3-D network of finite sites that are randomly positioned. The percolation behavior of the network is studied using the Monte Carlo method, which leads to the determination of the critical fiber volume fraction (or the percolation threshold). The effect of fiber curliness on the percolation behavior is incorporated in the current model by using 3-D arm-shaped fibers, each of which needs five independent geometrical parameters (i.e., three coordinates for its vertex and two orientation angles) for its identification. There are three controlling parameters for such fibers, namely the fiber arm length, the fiber aspect ratio, and the fiber arm angle. The new model also considers the sample size and scaling effects. The simulation results reveal an exponential relationship between the fiber aspect ratio and the percolation threshold: the higher the aspect ratio, the lower the threshold. It is also found that the curliness largely influences the percolation threshold: the more curved the fiber, the higher the threshold. However, the effect of curliness diminishes with the increase of the fiber aspect ratio. With the percolation threshold obtained from the Monte Carlo model, the effective electrical conductivity of the composite is then determined by applying the theory of percolation. The numerical results indicate that the composite conductivity decreases as the fibers become more curved and as the fiber aspect ratio decreases. These predicted trends of the percolation threshold and composite conductivity are in good agreement with existing experimental and simulation results.     

Nanostructured polymer blend formed from poly(N-vinylpyrrolidone) and end-functional polystyrene

Phase structures of blends of poly(N-vinylpyrrolidone) (PVP) with SO₃H terminated polystyrene (PSS) were investigated. The PVP-PSS blends were macroscopically homogeneous, although the blends of PVP with polystyrene (PS) showed macroscopic phase separation. The PVP-PSS blends, however, showed two glass transitions indicating existence of two phases. Small-angle X-ray scattering measurements revealed the PVP-PSS blends formed mesomorphically ordered morphologies which change with variation of blend composition. The nano-organized phase separation in the PVP-PSS blends was caused due to hydrogen bonding of the PVP with the terminal SO₃H group of the PSS and repulsive interaction between PVP and main chain of the PSS.     

Characterisation of [(1−x)PMMA-xPVdF] polymer blend electrolyte with Li ion

The possible use of polymeric materials in thin-film solid electrolytes for battery systems, fuel cells, sensors and other electrochemical applications has stimulated worldwide interest in metal salt solvating macromolecules. Polymer electrolyte membranes comprising of poly(methyl methacrylate) (PMMA), poly(vinylidene fluoride) (PVdF) and lithium perchlorate are prepared using a solvent casting technique. Polymer blends have been characterised by FTIR and XRD studies to determine the molecular environment for the conducting ions. The role of interaction between polymer hosts on conductivity is discussed using the results of ac impedance studies. The ionic conductivity is presented as a function of temperature and PVdF content. Room temperature conductivity of 3.14×10⁻⁵ S cm⁻¹ has been obtained for the [0.25PMMA/0.75PVdF]-LiClO₄ polymer complex.     

Development of new ionomer blend membranes,their characterization,and their application in the perstractive separation of alkenes from alkene–alkane mixtures. I. Polymer modification,ionomer blend membrane preparation,and characterization

In this contribution, the synthesis and characterization of novel ion‐exchange blend membranes which contain the SO₃Ag group for the application in the perstractive separation of alkene–alkane mixtures, where the Ag⁺ ion serves as facilitated transport site for the alkene via formation of a pi complex with the alkene double bond, is presented. In this part of the article, the synthesis and characterization of following blend membrane types are described: (1) acid–base blend membranes of ortho‐sulfone‐sulfonated polysulfone (PSU) with ortho‐sulfone‐diaminated PSU; (2) blend membranes of ortho‐sulfone‐sulfonated PSU with unmodified PSU; (3) blend membranes of ortho‐sulfone‐sulfonated PSU with ortho‐sulfone disilylated PSU. The differently modified PSU types were characterized via ¹H nuclear magnetic resonance (¹H‐NMR). The acid–base blend membranes were characterized via Fourier transfer infrared (FTIR) spectroscopy. It could be indirectly proved that formation of PSU–SO₃ ⁺H₃N–PSU ionic crosslinks takes place. Transmission electron microscopy (TEM) investigations of (1) and (2) yielded the results that these blends are inhomogeneous at the microscopic scale. Mechanical stabilization of these blends is accomplished by physical entanglement of the different macromolecules. The blends (3) were macroscopically inhomogeneous due to the strong difference in hydrophilicity of the blend components. Only the blend 90% PSU–SO₃H 10% PSU[Si(CH₃)₃]₂ formed a blended membrane. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 428–438, 1999     

Advances in the science and technology of paints, inks and related coatings: 2005

Summary  This review summarises the developments in adhesion, VOC emissions, coatings, transparent conductive coatings, hybrid organic-inorganic coatings, UV curing, biocidal coatings, paints, weathering, wood coatings, surface treatment of concrete, metal corrosion, pigments, film formation, printing, modelling fluid flow in printing, dot gain and inkjet printing reported inSurface Coatings International Part B: Coatings Transactions,88, 2005.     

Development of new ionomer blend membranes,their characterization,and their application in the perstractive separation of alkenes from alkene–alkane mixtures. II. Electrical and facilitated transport properties

In this contribution, the synthesis and characterization of novel ion‐exchange blend membranes which contain the SO₃Ag group for the application in the perstractive separation of alkene–alkane mixtures, where the Ag⁺ ion serves as facilitated transport site for the alkene via formation of a pi complex with the alkene double bond, is presented. In this part of the article, the transport properties of the following blend membrane types are described: (1) acid–base blend membranes of ortho‐sulfone‐sulfonated polysulfone (PSU) with ortho‐sulfone‐diaminated PSU; (2) blend membranes of ortho‐sulfone‐sulfonated PSU with unmodified PSU; (3) blend membranes of ortho‐sulfone‐sulfonated PSU with ortho‐sulfone disilylated PSU. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 422–427, 1999     

Structural,electrical and optical properties of pure and NaLaF<Subscript>4</Subscript> doped PEO polymer electrolyte films

A Sodium ion conducting polymer electrolyte based on Polyethylene oxide (PEO) complexed with Sodium lanthanum tetra fluoride (NaLaF₄) was prepared using solution cast technique. The complexation of the salt with PEO was confirmed by X-ray diffraction (XRD) and Fourier Transform Infrared spectroscopic (FTIR) studies. Differential Scanning Calorimetry (DSC) is carried out to determine the melting temperature of these electrolyte films. Electrical conductivity was measured in the temperature range 300–370 K as a function of dopant concentration as well as temperature. Optical absorption studies were made in the wavelength range 200–600 nm on pure and NaLaF₄ doped PEO film. The absorption edge was observed at 4.62 eV for undoped PEO while it ranged from 3.16 to 3.5 eV for NaLaF₄ doped films. The direct band gaps for undoped and NaLaF₄ doped PEO films were found to be, respectively, 4.54 and 3.44, 3.24 and 3.12 eV while the indirect band gaps were 4.43 and 3.25, 3.05 and 2.9 eV, respectively. It was found that the energy gaps and band edge values shifted to lower energies on doping with NaLaF₄ salt.