Charge transport mechanism of graphite‐nanosheet‐loaded rubber nanocomposites

Nitrile butadiene rubber loaded with different concentrations of thin graphite nanosheets have been successfully prepared by using a two‐roll mill. The percolation concentration of the nanocomposites was 0.5 phr. The I–V characteristic curves showed that the nanocomposites exhibited ohmic behaviour at a certain voltage and then non‐linear behaviour. The Richardson–Schottky and Poole–Frenkel models were used to investigate the reason for the space charge. The experimental data fit the Schottky model well. The conductivity as a function of temperature was also studied and the data were fitted by using the Mott relation. The Mott relation showed that as the concentration of graphite nanosheets in the rubber composite increases, the hopping distance between the graphite nanosheet layers decreases, which enhances the conductivity of the nanocomposite at low concentrations. Copyright © 2011 Society of Chemical Industry     

Investigation of electrical conduction mechanism in double‐layered polymeric system

The electrical conduction in solution‐grown polymethylmethacrylate (PMMA), polyvinylidenefluoride (PVDF) and PMMA‐PVDF double‐layered samples in the sandwich configuration (metal‐polymer‐metal) was investigated at different fields in the range 100–120 kV/cm as a function of temperature in the range 293–423 K for samples of constant thickness of about 50 μm. Certain effects which lead to a large burst of current immediately after the application of field were observed in double‐layered samples. An attempt was made to identify the nature of the current by comparing the observed dependence on electric field, electrode material and temperature with the respective characteristic features of the existing theories on electrical conduction. The observed linear I‐V characteristics show that the electrical conduction follows Pool‐Frenkel mechanism in PMMA and PVDF samples. Whereas, the non‐linear behavior of current‐voltage measurements in PMMA‐PVDF double‐layered samples have been interpreted on the basis of space charge limited conduction (SCLC) mechanism. The conductivity of the polymer films increased on formation of their double‐layer laminates. The polymer‐polymer interface act as charge carrier trapping centres and provides links between the polymer molecules in the amorphous region. The interfacial phenomenon in polymer‐polymer heterogeneous system has been interpreted in terms of Maxwell‐Wagner model. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Design of holographic polymer‐dispersed liquid crystals based on solubility parameters

BACKGROUND: A slight change of polymer structure leads to a significantly different solubility parameter (SP), which is related to incompatibility and interface anchoring energy between a polymer and a liquid crystal (LC). RESULTS: Holographic gratings in polymer‐dispersed liquid crystals have been fabricated based on various urethane acrylate oligomer sizes and type of reactive diluent at two LC loadings. A large SP gap, using N‐vinylpyrrolidone as reactive diluent, gave much faster saturation of diffraction efficiency at higher level, but the grating failed to operate. On the contrary, films having a small SP gap, using 2‐ethylhexyl acrylate, operated under 20 V with a response time of about 10 ms, although their saturation of diffraction efficiency was relatively low. The results were interpreted in terms of morphology (determined using scanning electron microscopy), anchoring energy and resin elasticity. CONCLUSION: Low driving voltage and high diffraction efficiency are obtained by controlling the SP gap between LC and polymer. Copyright © 2007 Society of Chemical Industry     

Time dependences of conduction and self‐heating in acetylene carbon black‐filled high‐density polyethylene composites

The time dependences of electrical conduction and self‐heating behaviors in high‐density polyethylene filled with acetylene carbon black of 0.082 in volume fraction are studied in relation to voltage and ambient temperature. The characteristic decay current constant τ_i, and the exponential growth time constant for self‐heating τ_g are determined for the samples under voltages U above the critical value U_c for the onset of self‐heating. The influences of voltage and ambient temperature on τ_i and τ_g as well as the amplitude of the low‐resistance to high‐resistance switching are discussed on the basis of the random resistor network (RRN) model and the relationship between U_c and the intrinsic resistivity. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 99: 1124–1131, 2006     

Relative strength of H‐bonding groups on biodegradable polymer‐based blends in solution

The intermolecular hydrogen bonding interactions between poly(3‐hydroxybutyrate) and poly(styrene‐co‐vinyl phenol) copolymers with mutual solvent epichlorohydrin were thoroughly investigated by steady‐state fluorescence and viscosity techniques. Fluorescence spectroscopy along with viscosity technique was used to asses the intermolecular hydrogen bonding between poly‐(3‐hydroxybutyrate) and its blends with five copolymer samples of styrene–vinyl phenol, containing different proportions of vinyl phenol but similar average molecular weight and polydispersity index. In the case of very low OH contents (2–4 mol %), as expected, both components of poly(3‐hydroxybutyrate) and poly(styrene‐co‐4‐vinylphenol) chains are well separated and remain so independently of the mixed polymer ratio and overall polymer concentration as well. Conversely, when the OH content reaches 5.8 mol % or more, a significant decrease of the intrinsic fluorescence intensity emitted by the copolymer is detected upon addition of aliquots of poly(3‐hydroxybutyrate). In these cases, an average value for the interassociation equilibrium constant, K_A = 8.7, was obtained using a binding model formalism. A good agreement of these results with those obtained from complementary viscosity measurements, through the interaction parameter, Δb, was found. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 900–910, 2006     

Influence of oxygen ion implantation on the free volume parameters and electrical conductivity of a polymer‐based bakelite RPC detector material

We have investigated the effect of ion implantation on structural modification and the electrical conductivity of Bakelite‐resistive plate chamber (RPC) detector material used in high energy physics experiments. Samples of Bakelite polymer were exposed to 100 keV and 150 keV oxygen ions in the fluence of 10¹² to 10¹⁵ ions cm^?2. Ion implantation induced microstructural changes have been studied using positron annihilation lifetime spectroscopy, X‐ray diffraction and Fourier transform infrared techniques. Positron lifetime parameters viz., o ‐Ps lifetime and its intensity showed formation of radicals, secondary ions due to the creation of interior tracks by high‐energy ions followed by chain scission at lower fluence of 100 keV implantation. The decreased free volume size at 150 keV ion implantation is an indication of crosslinking and filling up of interior tracks by the implanted ions. Variation of ac conductivity with frequency obeys Jonscher power law at 100 keV and the conduction mechanism is explained by barrier hopping model. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134 , 44962.     

Probe dependency of polymer‐plasticizer and polymer‐polymer interaction parameters in inverse gas chromatography

Inverse gas chromatography has been widely used to determine the Flory–Huggins parameter, χ, between a plasticizer and a polymer, or between two polymers. Many studies showed that interaction parameters may be probe dependent. In a recent study it was proposed that, when a specific interaction occurred between two polymers, the probes had less interaction with the polymers, leading to a lower solubility parameter for polymer blends than the volume average of the components. An equation was derived to relate the probe dependency to the deviation of solubility parameter of polymer mixtures. Here this approach is applied to plasticized poly(vinyl chloride) (PVC) and a copolymer, and to poly(vinylidene fluoride)–poly(ethyl methacrylate) blends. For a PVC and epoxidized oil system the relative deviation of specific retention volume showed two trends, with saturated hydrocarbons as one group, and polar and aromatic probes as another group. For the poly(vinylidene fluoride)/poly(ethyl methacrylate) system the plot of retention volume deviation versus solubility parameter of probes also showed separate trends for n‐alkanes, esters, and alcohols. But the plot of ?₂?₃RT(χ₂₃/V₂) versus solubility parameter had better linearity for the systems studied. The slope of this plot was used as an indicator for miscibility. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007     

Dielectric properties of new fully conjugated 2H‐ and metal‐pyrazinoporphyrazine network polymers

2,7‐Di‐tert‐butylpyrene was oxidized to 2,7‐di‐tert‐butylpyrene‐4,5,9,10‐tetraone. The latter through condensation reaction with vicinal diamine such as diaminomaleodinitrile afforded heterocyclic monomer, 2,7‐di‐tert‐butyl pyrene[4,5][9,10]bis(2,3‐pyrazine‐5,6‐dinitrile), which was cyclotetramerized to the corresponding 2H‐ and metal‐pyrazinoporphyrazine‐based network polymers (2H‐PyzPz and M‐PyzPz, M = Co, Ni, Zn, or Cu). Elemental analytical results, Infrared, and NMR spectral data of the new prepared molecules are consistent with their assigned formulations. Molecular masses and metal contents of the synthesized polymers proved to be of high molecular masses, which confirm the efficiency of tetramerization polymerization and complexation reactions. Dielectric permittivity, ε′, loss tangent, tan δ, and ac conductivity, σac(ω), of 2H‐PyzPz and M‐PyzPz films were studied as a function of temperature and frequency. It was found that dielectric permittivity, ε′, decreases with the increase of frequency and increases with the increase in temperature. Ac conductivity, σac(ω), is found to vary as Bωs and the frequency exponent, s, is less than unity around room temperature indicating a dominant hopping process. On the other hand, σac(T) of all samples is thermally activated with low activation energies. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011.     

Pyrrole‐based narrow‐band‐gap copolymers for red light‐emitting diodes and bulk heterojunction photovoltaic cells

A series of narrow‐band‐gap conjugated copolymers (PFO‐DPT) derived from pyrrole, benzothiadiazole, and 9,9‐dioctylfluorene (DOF) is prepared by the palladium‐catalyzed Suzuki coupling reaction with the molar feed ratio of 4,7‐bis(N‐methylpyrrol‐2‐yl)‐2,1,3‐benzothiadiazole (DPT) around 1, 5, 15, 30, and 50%. The obtained polymers are readily soluble in common organic solvents. The solutions and the thin solid films of the copolymers absorb light from 300 nm to 600 nm with two absorbance peaks at around 380 nm and 505 nm. The PL emission consists mainly of DPT unit emission at around 624–686 nm depending on the DPT content in solid film. The EL emission peaks are red‐shifted from 630 nm for PFO‐DPT1 to 660 nm for PFO‐DPT50. Bulk heterojunction photovoltaic cells fabricated from composite films of copolymer and [6,6]‐phenyl C₆₁ butyric acid methyl ester (PCBM) as electron donor and electron acceptor, respectively, in device configuration: ITO/PEDOT : PSS/PFO‐DPT : PCBM/Ba/Al shows power conversion efficiencies 0.15% with open‐circuit voltage (V_oc) of 0.60 V and short‐circuit current density (J_sc) of 0.73 mA/cm² under AM1.5 solar simulator (100 mW/cm²). © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Influence of irradiation crosslinking on time dependences of conduction and self‐heating in acetylene carbon black filled high‐density polyethylene composites

The time dependences of electrical conduction and self‐heating in high‐density polyethylene/acetylene carbon black composites crosslinked with electron beam irradiation at three different dosages are studied in relation to voltage and ambient temperature. The characteristic decay current constant (τ_i) and the exponential growth time constant for self‐heating (τ_g) are determined for the samples under voltages (U) above the onset voltage (U_c) of self‐heating. The influence of crosslinking on the current decay dynamics, self‐heating process, and amplitude of the resistance switching under field action are discussed. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 4418–4422, 2006     

Fabrication of polymer‐dispersed liquid crystals with low driving voltage based on the thiol‐ene click reaction

Polymer‐dispersed liquid crystals (PDLCs ) with a well‐defined polymer matrix were successfully fabricated by the thiol‐ene click reaction based on poly(ethylene glycol) diacrylate (PEGDA ) and trimethylolpropanetris‐(3‐mercaptopropionate) (TMTP ). UV ?visible spectrophotometry, Fourier transform IR spectroscopy, SEM and polarized optical microscopy were employed to explore the PDLC films obtained. Electro‐optical properties were studied with a UV ?visible spectrophotometer. It was found that the PDLC films with optimal thiol content fabricated by the thiol‐ene click reaction showed high transmittance, low driving voltage and a low memory effect. It was concluded that the driving voltage change of PDLCs with different thiol concentrations was caused by the polymerization rate and the structure of the polymer matrix. © 2017 Society of Chemical Industry     

Layer‐by‐layer films based on charge transfer interaction of ϕ‐conjugated poly(dithiafulvene) and incorporation of gold nanoparticles into the films

Layer‐by‐layer (LBL) self‐assembled ultrathin films were prepared via consecutively alternating immersion of substrates into solutions of electron donor, poly(dithiafulvene) (PDF), and electron acceptor, poly(hexanyl viologen) (6‐VP). The charge transfer (CT) interaction formed at solid–liquid interfaces between the backbones of the electron acceptor and donor polymers was the driving force of the alternative deposition. The sandwich heterostructure of the LBL film led to electrical anisotropy in the directions parallel and perpendicular to the film surfaces. Incorporation of gold nanoparticles into the LBL films was investigated by reducing gold ions with the PDF layers already deposited on the film surfaces, or depositing PDF‐protected gold colloidal solution as the electron donor layers directly. The influence of the gold nanoparticles on the electrical anisotropy of the LBL films was also illustrated in this research. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 1608–1615, 2007     

Structure and mechanical properties of fluorine‐containing glycidyl azide polymer‐based energetic binders

A novel energetic polymer, fluorine‐containing glycidyl azide polymer (FGAP ), was developed via an initial cationic copolymerization of epichlorohydrin and 1,1,1‐trifluoro‐2,3‐epoxypropane, followed by azidation. The structure of FGAP was confirmed using Fourier transform infrared, ¹H NMR and ¹³C NMR spectroscopies. The molecular weight and the thermal behavior of FGAP were characterized using gel permeation chromatography, differential scanning calorimetry and thermogravimetric analysis. FGAP had a molecular weight of 2845 g mol^?1, and the glass transition temperature and decomposition temperature were found to be ?47.8 and 253 °C, respectively. FGAP ‐based polyurethane networks were further prepared using triphenylmethane‐4,4,4‐triisocyanate as the crosslinking agent. In comparison with GAP , FGAP ‐based polyurethane networks exhibited better mechanical behaviors (a tensile strength of 1.5 MPa and an elongation at break of 81.6%). The results demonstrated that FGAP might be a promising polymeric binder for future propellant formulations. © 2017 Society of Chemical Industry     

Study on the extraction of dyes into a room‐temperature ionic liquid and their mechanisms

The investigation of liquid–liquid extraction of dyes is carried out by using ionic liquid—1‐butyl‐3‐methylimidazolium hexafluorophosphate ([BMIM][PF₆])—as extraction phase. The effects of its process parameters are studied in detail, such as extraction phase ratio, pH of the aqueous phase, and concentration of dicyclohexyl‐18‐crown‐6 (DCH‐18C6) in the organic phase. Important results are obtained as follows: acid dyes can be extracted with [BMIM][PF₆] quantitatively; the removal of reactive dyes is low; however, it can be greatly increased by the addition of DCH‐18C6. The pH value has a great impact on the removal of the acid dye and the reactive dye. However, it does not influence the extraction of the weak acid dye. It is found that the extraction process of acid dyes adopts the form of anion exchange and the soluble part of the ionic liquid plays an important role as counter‐ions. Copyright © 2007 Society of Chemical Industry     

Effect of the tie‐layer thickness on the delamination and tensile properties of polypropylene/tie‐layer/nylon 6 multilayers

This study examined the effect of the tie‐layer thickness on the delamination behavior of polypropylene/tie‐layer/nylon 6 multilayers. Various maleated polypropylene resins were compared for their effectiveness as tie‐layers. Delamination failure occurred cohesively in all the multilayer systems. Two adhesion regimes were defined according to the change in the slope of the linear relationship between the delamination toughness and the tie‐layer thickness. The measured delamination toughness of the various tie‐layers was quantitatively correlated to the length of the damage zone that formed at the crack tip. In addition, the effect of the tie‐layer thickness on the multilayer tensile properties was correlated with the delamination behavior. The fracture strain of the multilayers decreased with decreasing tie‐layer thickness. An examination of the prefracture damage mechanism of the stretched multilayers revealed a good correlation with the delamination toughness of the tie‐layers. In thick tie‐layers (>2 μm), the delamination toughness was great enough to prevent the delamination of the multilayers when they were stretched. In thin tie‐layers (<2 μm), the delamination toughness of all the tie‐layers was low; consequently, delamination led to premature fracture in the stretched multilayers. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Transient and steady‐state conduction in ethyl cellulose (EC)–poly(methyl methacrylate) (PMMA) blends

Transient discharging currents and steady‐state conduction in solution‐grown ethyl cellulose (EC)–poly(methyl methacrylate) (PMMA) blends measured as a function of temperature (30–80 °C) and field strength (10–100 kV cm⁻¹) are reported. Transient currents are found to follow the Curie–VonSchweidler law, characterized by different slopes in short‐ and long‐time regions, having different decay constant values lying between 0.75–0.99, and 1.68–1.95. The corresponding activation energies are found to increase with time of measurement of discharge current. Isochronal characteristics (ie current versus temperature plots at constant times) constructed from the data seem to reveal a broad peak observed at 60 °C. The dependence of dark current at different temperatures (30–80 °C) in a metal (1)–EC–PMMA blend–metal (1)/(2) system on the applied voltage in the range 10–100 kV cm⁻¹ has also been studied; the current is found to be strongly temperature dependent. Dipole polarization and space charge resulting from trapping of injected charge carriers in energetically distributed traps and induced dipoles created because of the piling up of charge carriers at the phase boundary of the heterogeneous components of the blend are considered to account for the observed transient currents. The results of current–voltage measurement on blends are interpreted to show that the low‐field steady‐state conduction is ohmic in nature, and in high fields the charge carriers are generated by field‐assisted lowering of coulombic barriers at the traps and are conducted through the bulk of the material by a hopping process between the localized states by a Jonscher–Ansari Poole–Frenkel mechanism. The modified P–F barrier is calculated to be 1.89 × 10⁻¹⁹ J (1.18 eV), 1.92 × 10⁻¹⁹ J (1.20 eV) and 1.95 × 10⁻¹⁹ J (1.22 eV) for P₁, P₂ and P₃ blends, respectively. © 2000 Society of Chemical Industry     

Investigations of the electrical conduction mechanisms of polyaniline‐DBSA/poly(acrylonitrile‐butadiene styrene) blends

The electrical properties of Al/PANI‐DBSA/ABS/Au blend with PANI (5%) w/w have been investigated by using of current‐voltage (I‐V) measurements, in a temperature range of 100–313 K. The analysis of I‐V characteristics in the forward direction was based on thermionic emission mechanism for applied electrical field till ～3 × 10² V/cm. The thickness dependence of the current‐voltage relationship, clearly demonstrates that the electrical current for larger fields is space charge limited current (SCLC). Temperature dependences of the ideality factor, barrier height, and series resistance have been calculated. The mobility of carriers which is temperature dependent was calculated using the trap free SCLC as 1.53 × 10^?4 cm² V^?1 s^?1 at room temperature. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40688.     

Development of soft‐sphere contact models for thermal heat conduction in granular flows

Conductive heat transfer to flowing particles occurs when two particles (or a particle and wall) come into contact. The direct conduction between the two bodies depends on the collision dynamics, namely the size of the contact area and the duration of contact. For soft‐sphere discrete‐particle simulations, it is computationally expensive to resolve the true collision time because doing so would require a restrictively small numerical time step. To improve the computational speed, it is common to increase the “softness” of the material to artificially increase the collision time, but doing so affects the heat transfer. In this work, two physically‐based correction terms are derived to compensate for the increased contact area and time stemming from artificial particle softening. By including both correction terms, the impact that artificial softening has on the conductive heat transfer is removed, thus enabling simulations at greatly reduced computational times without sacrificing physical accuracy. © 2016 American Institute of Chemical Engineers AIChE J, 62: 4526–4535, 2016     

Dual electroluminescence from a single‐component light‐emitting electrochemical cell,based on water‐soluble conjugated polymer

Poly [[2‐methoxy‐5‐(3‐sulfonatopropoxy)‐1, 4‐phenylene]‐1, 2‐ethenediyl] (MPS‐PPV) was an anionic water‐soluble conjugated polymer. A novel single‐component light‐emitting electrochemical cell (LEC) with an indium tin oxide/MPS‐PPV/aluminum sandwich structure has been successfully fabricated. MPS‐PPV serves as both luminescent material and ionic conductor in the active layer. Electroluminescence can be observed under both forward and reverse bias with emission maxima at about 520 nm (green light). In particular, the device has a low turn‐on voltage of about +3V and ?4V, and can sustain long‐term operations without much loss of efficiency at ambient conditions. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 2930–2936, 2006