POMA/PMMA blends modified by dye: Spectroscopic and morphological properties

Poly(o‐methoxyaniline) (POMA), a conductive polymer (CP) well known, was used to prepare blends with poly(methyl methacrylate) (PMMA). Conducting polymer keeps absorbance strength within the PMMA matrix. POMA/PMMA blends presented absorption bands regarding the conducting polymer with different intensities and the main band red shifting. However, POMA/PMMA blends showed no photoluminescence (PL) emission. After the hybridization process of the CP with a photoluminescent dye, 2,1,3‐benzothiadiazole, POMA/PMMA blends showed new optical properties. PL spectra revealed an emission in the range of 500–550 nm, indicating interaction between the dye and the conducting polymer. The presence of the dye modified the morphological properties of the POMA/PMMA blends. New features have appeared on the surface of the blends prepared with higher concentration of hybridized CP. Blends with lower concentrations of hybridized CP showed their surfaces with POMA globules being covered by PMMA. This morphology replaced the globules and “crystals” on the surface of the blends prepared without the dye. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Novel composites of copper nanowire/PVDF with superior dielectric properties

Novel copper nanowires (CuNWs)/poly(vinylidene fluoride) (PVDF) nanocomposites with high dielectric permittivity (ε′) and low dielectric loss (ε″) were prepared by a precipitation technique followed by melt compression. Their dielectric properties over the broadband frequency range, i.e. 10¹–10⁶ Hz, were compared with multi-walled carbon nanotubes (MWCNT)/PVDF nanocomposites prepared by the same technique. It was observed that the CuNWs/PVDF nanocomposites had higher dielectric permittivity, lower dielectric loss and thus significantly lower dissipation factor (tan δ) than the MWCNT/PVDF nanocomposites at room temperature. This behavior was ascribed to a higher conductivity of the fresh core of the CuNWs relative to the MWCNT, which provided the composites with a higher amount of mobile charge carriers participating in the interfacial polarization. Moreover, the presence of oxide layers on the CuNWs surfaces diminished the conductive network formation leading to a low dielectric loss.     

Dielectric relaxation and Poole–Frenkel conduction in poly(vinyl chloride) blends with bisphenol A/Egyptian corncob resin

The dielectric constant (ε′), dielectric loss index (ε″), direct-current conductivity, and current–voltage (I–V) characteristics of pure poly(vinyl chloride) (PVC) and blends of PVC and bisphenol A/Egyptian corncobs (BCC) were investigated at different temperatures. The relaxation processes for PVC and its blends revealed that PVC and BCC had an incompatible phase. PVC blends with 5 wt % BCC exhibited a peculiar I–V behavior. Both ε′ and ε″ were used to study miscibility and phase behavior in blends of PVC. The activation energies of all PVC samples were calculated. At higher voltages, the conduction mechanism could be identified as the Poole–Frenkel type. In addition, the ionic groups of BCC could enhance the PVC conductivity. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Tailored ferroelectric responses and enhanced energy density in PVDF‐based homopolymer/terpolymer blends

Blend of polymers is an effective way to tailor the ferroelectric responses and improve the energy storage properties of polymers. In this work, the microstructure and dielectric responses of the blends of poly(vinylidene fluoride) (PVDF) and poly(vinylidene fluoride‐trifluoroethylene‐chlorofluoroethylene) [P(VDF‐TrFE‐CFE)] have been studied. It is found that the addition of PVDF disturbs the crystallization process of P(VDF‐TrFE‐CFE), leading to lower crystallinity and smaller crystalline size. The aforementioned microstructure changes result in tailored ferroelectric responses. Dielectric responses show that the blend with 10 wt % PVDF achieves larger polarization response under high electric field (above 300 MV/m) due to the interfacial polarization. Because of the tailoring effect and the interfacial polarization, the blend with 10 wt % PVDF exhibits higher energy density and efficiency. Moreover, the breakdown strength (E_b) is also improved by adding a small amount of PVDF into the terpolymer. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40994.     

Conductive polyaniline–polychloroprene blends

The electrical conductivity of polychloroprene (CR)/polyaniline (Pani) blends prepared by bulk and solution processes were investigated. Pani doped with HCl (Pani · HCl) and p-toluenesulfonic acid (Pani · TSA) were employed in vulcanized blends obtained by the bulk process. These blends showed an increase in the conductivity only for blend composition of CR/Pani = 50:50 wt %. At this composition, blends with Pani · HCl and Pani · pTSA presented conductivity values of 10⁻⁹ and 10⁻¹⁰ S · cm⁻¹, respectively. CR/Pani · HCl blend films prepared by the solution process displayed surface conductivity values of 10⁻⁴ S · cm⁻¹ with as low as 10–15 wt % of PAni · HCl. Surface analysis of these blends by X-ray photoelectron spectroscopy indicated no traces of the conductive additive. The surface composition was found to be exclusively constituted of CR. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 70: 1543–1549, 1998     

Miscibility of poly(methoxymethyl methacrylate) and poly(methylthiomethyl methacrylate) with poly(vinylidene fluoride)

Summary The miscibility behaviour of poly(methoxymethyl methacrylate) (PMOMA) and poly(methylthiomethyl methacrylate) (PMTMA) with poly(vinylidene fluoride) (PVDF) was examined by differential scanning calorimetry. PMOMA/PVDF blend system was judged to be miscible on the bases of the presence of a single, composition-dependent glass transition for the blend and a pronounced melting point depression of the PVDF component. Furthermore, lower critical solution temperature (LCST) behaviour was observed for all PMOMA/PVDF blends. PMTMA/PVDF blends were found to be immiscible. Based on the melting point depression of PVDF in PMOMA/PVDF blends, the interaction parameter B was found to be -14.5 J/cm³.     

Preparation of electrospun electroactive POMA fiber mats

A neat electroactive freestanding non‐woven mat was first prepared from poly(o‐methoxyaniline) (POMA) using an electrospinning technique without blending or grafting. Results showed that a continuous fibre structure was obtained for high weight‐average molecular weight M?_w of POMA, i.e. POMA forced to become more soluble when synthesized in the presence of CaCl₂ and an alkoxyl‐ring‐substituted structure. By performing gel permeation chromatography and viscosity tests, we found that M?_w ≈ 69 000 g mol^?1 and concentrations were critical to the formation of beads or fibres. The electrospinning parameters that cause morphological changes were found by scanning electron microscopy. By comparing these with governing parameters such as viscosity, feeding rate, collector distance and applied voltage, uniform POMA fibres were produced from 5 wt% POMA solution at 20 kV with a feeding rate of 0.02 mL min^?1 and nozzle‐to‐collector distance of 12 cm. In addition, the electroactivity and mechanical strength of the neat electrospun non‐woven mats were studied by electrochemical cyclic voltammogram and dynamic mechanical analysis, respectively. Copyright © 2011 Society of Chemical Industry     

Microwave absorbing properties of carbon black/silicone rubber blend

In the frequency range of 2–18 GHz, the microwave absorbing properties of a carbon black/silicone rubber blend were investigated by changing the carbon black content and the thickness. The real part (ε′) and the imaginary part (ε″) of permittivity of the blends were calculated from the S‐parameters measured by a network analyzer. The reflection loss was simulated by using ε′ and ε″. The reflection loss less than ?10 dB could be obtained in the frequency range of 9.6ε13.5 GHz from the sample with 10 wt% of carbon black at 1.9 mm of thickness.     

Fabrication of high‐k poly(vinylidene fluoride)/Nylon 6/carbon nanotube nanocomposites through selective localization of carbon nanotubes in blends

The morphology as well as the distribution of conductive fillers in conductive filler/polymer nanocomposites have a decisive effect on the dielectric properties of blend composites. In this study, the relationship between morphology and properties was carefully investigated and the underlying mechanism is discussed based on the microcapacitor model. Multiwalled carbon nanotubes (CNTs) were introduced into an immiscible poly(vinylidene fluoride) (PVDF)/polyamide 6 (Nylon 6) blend and the morphologies of PVDF/Nylon 6 were tailored by changing the weight ratio of PVDF to Nylon 6, varying from sea‐island morphology to co‐continuous morphology. Interestingly, the CNTs are selectively localized in the Nylon 6 phase in both sea‐island and co‐continuous morphological blends, which is due to the finer interaction between Nylon 6 and CNTs. In the sea‐island morphological blend only, a strong increase of the dielectric permittivity can be found when the content of CNTs is increased. It is surprising that no effects of CNTs on the dielectric properties can be found in the co‐continuous morphological blend. The CNT filled Nylon 6 domains in the sea‐island morphological blend act as a microcapacitor with improved charge accumulation and interfacial polarization, resulting in a marked increase in dielectric permittivity. © 2016 Society of Chemical Industry     

Preparation and characterization of castor oil‐based polyurethane/poly(o‐methoxyaniline) blend film

Blends made up of castor oil‐based polyurethane (PU) and poly(o‐methoxyaniline) (POMA) were obtained in the form of films by casting and characterized by FTIR, UV‐Vis‐NIR spectroscopy, and electrical conductivity measurements. Doping was carried out by immersing the films in 1.0M HCl aqueous solution. Chemical bonds between NCO group of PU and NH group of POMA were observed by means of FTIR spectra. The UV‐Vis‐NIR spectra indicated that the presence of the PU in the blend does not affect doping and formation of the POMA phase. The electrical conductivity research was in the range of 10^?3 S/cm. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Phase behavior of poly(ε-caprolactone)/ poly (vinylidene fluoride) blends

The miscibility of blends of poly (ε-caprolactone) (PCL)/poly(vinylidene fluoride) (PVDF) was studied by measuring the cloud point, melting point depression and crystallization kinetics. Lower critical solution temperature (LCST) behavior was observed at PCL-rich compositions, whilst it was not observed at high compositions of PVDF. However it is possible that an LCST could exist below the melting point of PVDF. From analysis of the melting point depression, the Flory interaction parameter x₁₂, was calculated from the Nishi-Wang equation and the value was found to be-1.5. The crystallization rate of PCL increased with increasing amount of PVDF in the blend. The spinodal curve for PCL/PVDF blends was simulated by using the lattice-fluid theory.     

Electrical and Mechanical Properties of Some Butadiene Rubber Composites in the Vicinity of the Percolation Threshold

The electrical and mechanical properties of NBR/SBR blends with different compositions were studied before the addition of carbon black. The increase in permittivity ε′ and dielectric loss ε″ noticed by increasing NBR content is due to the increase in C ≡ N dipoles. The mechanical properties which include tensile and elongation at yield and rupture are also found to be increased. This work also includes the compatibility study, which was carried out using different tools and techniques (Heat of mixing, dielectric and scanning electron microscope). This study led to a conclusion that both blends are incompatible.

The electrical as well as the mechanical properties were carried out on NBR, SBR and NBR/SBR blend (50/50) to be loaded with different concentrations of high abrasion furnace black (HAF) in order to find out the percolation thresholds in relation to the net work formation.

The electrical conductivity of carbon-black-filled composites is increased from pure polymer to that of pure carbon, through the change in the different composites. Up till certain concentration of HAF (30 phr for both NBR and SBR) and 20 phr for NBR/SBR blends the conductivities of the composites are approximately the same and closed to that of the pure, electrically insulating polymer matrix. These concentrations are called percolation thresholds. Above such concentrations, the conductivity increases many orders of magnitude with very little increase in the filler amount. With this increase the tendency of conductivity chain formation increases through the aggregation of the carbon black particles network. The change in conductivity beyond the percolation threshold is expressed according to the percolation theory with straight line when plotted graphically versus P-P_c; P_c is the volume fraction of carbon black at the percolation threshold.

In addition to the conductivity term, the data of permittivity ε′ and dielectric loss ε″ given at different frequencies from 100 Hz up to 100 kHz show an abrupt increase at 30 phr HAF for NBR & SBR and 20 phr HAF for NBR/SBR. More over, the relaxation times obtained from the analyses of these data using Fröhlich and Havriliak-Nagami functions, which ascribe the orientation of the large aggregates caused by the movement of the main chain also show an abrupt increase at the same concentration of HAF.

The mechanical properties, which investigated through the measurements of tensile and elongation at yield and rupture indicate an abrupt increase at the same concentration of HAF found in the case of electrical measurements. This result gives evidence to the good applicability between both mechanical and electrical investigations through the network formations.

Any how, the percolation threshold found in case of NBR/SBR blend is less than that for NBR itself. This result is attributed to the uneven distribution of the filler in the incompatible blend matrix.     

Electrical Conductivity and Dielectric Behavior of Some Poly(Alkyl Methacrylate)s/Polyvinylpyrrolidone Blends

A systematic dielectric study over a frequency range of 100 Hz up to 100 k Hz was carried out on some poly(alkyl methacrylate)s: poly(methyl methacrylate) (PMMA), poly(ethyl methacrylate) (PEMA), and poly(butyl methacrylate) (PBMA) blended with polyvinylpyrrolidone (PVP). The compatibility investigation, which was tested by using the dielectric method and confirmed by viscosity technique, led to a conclusion that both PMMA/PVP and PEMA/PVP blends are incompatible while PBMA/PVP blends are compatible. Tetrachlorophthalic anhydride (TCPA) was chosen to be added in increasing quantities (0%–30% by weight) to the investigated blends. Ten percent of such anhydride was found to solve the problem of phase separation between both incompatible blends. Moreover, the electrical conductivity of the investigated blends was found to increase linearly, in the semilogarithmic scale, by increasing TCPA content (10^?12 to 10^?5 S^?1 cm^?1). After subtraction of the losses due to dc conductivity, the dielectric data reveal a lower frequency absorption region, which is found to be unchanged by increasing either the blend ratio or the content of TCPA. This region ascribes the Maxwell-Wagner effect due to the difference in the permittivity and conductivities in polymeric materials. The higher values of ?″ in the higher frequency range for all the blends indicates a higher frequency absorption region with maximum frequency out of the available range of frequencies. The addition of TCPA shifts this maximum towards lower frequencies. This shift indicates an increase in the molar volume of the rotating units and consequently an increase in the relaxation time.     

Effect of the compatibility on dielectric performance and breakdown strength of poly(vinylidene fluoride)/low‐density polyethylene blends

Immiscible polymer blends with high dielectric constant (ε) and improved breakdown strength (E_b) performance were obtained by composing poly(vinylidene fluoride) (PVDF) with low‐density polyethylene (LDPE) or the LDPE grafted with maleic anhydride (LDPE‐g‐MAH) through melt‐blending way. The dielectric properties of these blends were emphasized for considering the compatibility effect on the energy storage application. Interface morphology, co‐continuity behavior, and grafted ratio were simultaneously investigated to detect the compatibility enhancement after introducing MAH. Results showed that the MAH positively improved the dielectric properties. Both the measured E_b of PVDF/LDPE and PVDF/LDPE‐g‐MAH blends showed a minimum value at v^PVDF = 50 vol % because of the worst compatibility; meanwhile, higher E_b of PVDF/LDPE‐g‐MAH than that of PVDF/LDPE blend was observed owing to the better compatibility. For considering the effect interface morphology on the dielectric performance, layer‐structure films composing with pure PVDF and LDPE layers were further constructed and studied. It was revealed that the layered structure could be treated as a helpful way to improve ε and E_b for immiscible polymer blends. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42507.     

Conductive poly(vinylidene fluoride)/polyethylene/graphene blend‐nanocomposites: Relationship between rheology,morphology, and electrical conductivity

Relationship between rheology, morphology, and electrical conductivity of the poly(vinylidene fluoride)/polyethylene/graphene nano‐platelets ternary system (PVDF/PE/GnP) were investigated. All the blend nanocomposites were prepared via a two‐step melt mixing method. GnP (0.75 and 1.5 wt %) was first compounded with PVDF and then the resulted premixtuers were melt mixed with PE to achieve the desired compositions. The corresponding reference nanocomposites and filler‐less blends were also prepared. Effect of an interfacial agent (PEMA; maleic anhydride grafted polyethylene) was also studied in this work. The results of rheological analysis in conjunction with the Raman spectroscopy experiments revealed that GnP had higher affinity to PVDF than PE, which in turn led to creation of conductive networks of GnP (1.5 wt %) in PVDF matrix exhibiting the electrical conductivity of about 10^?2 (S/cm). Double percolated micro‐structure was predicted for the PE/PVDF 40/60 (wt/wt) blend containing low GnP content (0.9 wt %) and confirmed via direct electron microscopy and conductivity analysis. Using 5 wt % of the PEMA reduced the conductivity to 10^?5 (S/cm) and further increase in PEMA content to 10 wt % led to non‐conductive characteristics. The latter was attributed to the migration of GnP from the PVDF phase to PE/PEMA phase and hence disturbance of double percolated micro‐structure. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46333.     

Effect of ionic liquid segments of copolymer on compatibilization process and dielectric behavior of polylactide/polyvinylidene fluoride blends

Biodegradable polylactide (PLA) and polyvinylidene fluoride (PVDF) blends containing the copolymer of PEGMA and 1-vinyl-3-ethylimidazolium bromide (PMI) were prepared, and the effects of ionic liquid segments of PMI on the compatibility of PLA and PVDF were investigated by dielectric relaxation spectroscopy (DRS). PMI can obviously improve the compatibility of PLA and PVDF, compared with the copolymer of PEGMA and vinyl imidazole (PMV). DRS showed that the compatibility of PLA and PVDF was related to the relaxation behavior of the blends, which was identified with Maxwell-Wagner-Sillars (MWS) interfacial polarization. The ε' of PLA/PVDF/PMI blends was much higher than that of PLA/PVDF/PMV blends in the same temperature, resulting from the stimulation of MWS interfacial polarization by the ion mobility of PMI.     

Influence of LiClO4 on the thermal,mechanical, and morphological properties of P(DMS‐co‐EO)/ P(EPI‐co‐EO) blends

The UV‐vis absorption, thermal analysis, ionic conductivity, mechanical properties, and morphology of a blend of poly(dimethylsiloxane‐co‐ethylene oxide) [P(DMS‐co‐EO)] and poly(epichlorohydrin‐co‐ethylene oxide) [P(EPI‐co‐EO)] (P(DMS‐co‐EO)/P(EPI‐co‐EO) ratio of 15/85 wt %) with different concentrations of LiClO₄ were studied. The maximum ionic conductivity (σ = 1.2 × 10^?4 S cm^?1) for the blend was obtained in the presence of 6% wt LiClO₄. The crystalline phase of the blend disappeared with increasing salt concentration, whereas the glass transition temperature (T_g) progressively increased. UV‐vis absorption spectra for the blends with LiClO₄ showed a transparent polymer electrolyte in the visible region. The addition of lithium salt decreased the tensile strength and elongation at break and increased Young's modulus of the blends. Scanning electron microscopy showed separation of the phases between P(DMS‐co‐EO) and P(EPI‐co‐EO), and the presence of LiClO₄ made the blends more susceptible to cracking. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 1230–1235, 2004     

Studies on SLS doped polyaniline and its blend with PC

Electrically conductive polyaniline (PANI) and its blend with polycarbonate (PC) was prepared by one-step emulsion polymerization technique in which sodium lauryl sulfate (SLS) acts as surfactant and as a protonating agent for the resulting polymer. The prepared PANI and its blends were characterized by density, percentage of water absorption, and electrical conductivity. PANI–PC blend exhibits a conductivity value of 4.70 × 10⁻² S/cm (PANI–PC1) and 5.68 × 10⁻⁵ S/cm (PANI–PC3) with a change in dopant from p-toluene sulfonic acid (TSA) to SLS, respectively. By using a more general method, which takes into account the presence of disorder of the second kind in polymers proposed by Hosemann, crystal size (〈N〉) and lattice strain (g in %) values were estimated. The variation of conductivity in doped PANI and PANI–PC blend has been explained on the basis of these microcrystalline parameters. TGA thermograms of PANI and PANI-PC blend show three-step degradation behavior. Thermal stability of PANI was improved after blending with PC. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 383–388, 2001     

Weak interaction,marginal miscibility,and ring‐band spherulites in blends of poly(vinylidene fluoride) with polyesters

Fourier transform infrared (FTIR) spectroscopy, optical microscopy (OM), and differential scanning calorimetry (DSC) techniques were used to probe phase behavior and interactions in blends of poly(vinylidene fluoride) (PVDF) and polyesters [poly(trimethylene adipate) (PTA) and poly(pentamethylene adipate) (PPA)] of relatively low crystallizability. DSC thermal analysis and OM characterization proved that PVDF was miscible with PTA and PPA with a low lower critical solution temperature. Small negative values of the interaction parameters (χ₁₂ = ?0.13 for a PVDF/PPA blend) were obtained with the melting‐point depression method. FTIR spectroscopy results revealed that interactions between ? CF₂ of PVDF and the ? C?O group of the polyester were weak, in agreement with the thermal analysis results. An increase in the coarseness and/or ring‐band spacing further provided supportive evidence that miscibility did exist between the polyester and PVDF constituents in the blends. Pattern changes in ring‐band spherulites of the miscible blends further substantiated the favorable, though weak, interactions between the PVDF and polyester constituents. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Non-isothermal crystallization behavior of poly(vinylidene fluoride)/ethylene–vinyl acetate copolymer blends

Non-isothermal crystallization behavior of poly(vinylidene fluoride) (PVDF) and ethylene–vinyl acetate (EVA) copolymer and their binary blends with different blending ratios were investigated by the use of differential scanning calorimetry (DSC). With the increasing cooling rates, PVDF, EVA and their binary blends showed wide crystallization temperature range and high crystalline enthalpy. Jeziorny and Mo’s models were applied to calculate non-isothermal crystallization kinetics parameters of neat PVDF, EVA and their binary blends. By Jeziorny method, the crystallization process of neat PVDF, EVA and PVDF/EVA = 7/3 blend can be divided into two parts: primary and secondary crystallization processes. The Avrami exponent n ₁ indicated that the primary crystallization process was a mixture model of three-dimensional and two-dimensional space extensions. In comparison, PVDF/EVA = 5/5 and PVDF/EVA = 3/7 blends showed a single crystallization process. Through Mo’s analysis, faster cooling rate was demanded to reach higher relative crystallinity. Crystallization rate coefficient (CRC) was used to describe the effect of crystallization rates on the interaction between PVDF and EVA. CRC reached a maximum value when the mass ratio of PVDF and EVA was 7/3. The maximum CRC values of PVDF system and EVA system were 98.1 and 179.9 h^?1, respectively. The activation energy was closely related to the extent of conversion and the neat samples had a maximum value of crystallization activation energy. This was consistent with the observation for the parameters from Jeziorny analysis and could be correlated to the heterogeneous nucleation.