Host Polymer Matrix Research Articles

A novel approach on poly(ionic liquid)-based poly(vinyl alcohol) as a hydrophilic/hydrophobic conductive polymer electrolytes

Conducting polymer electrolytes based on poly(vinyl alcohol) (PVA) as a host polymer matrix and polyionic liquid (PIL) hydrophilic/hydrophobic were prepared by solution casting technique and characterized by FTIR, scanning electron microscope (SEM), mechanical, conductivity, dielectric spectroscopy and thermogravimetric analysis. It was found that the presence of PIL affected positively both mechanical and electrical properties of the polymer electrolytes. Polymer electrolytes with PIL-dispersion give the best tensile strength compared to those with PIL-solid. From the results of mechanical properties, it is concluded that PIL-dispersion can act as a plasticizer, whereas PIL-solid can act as traditional filler. The addition of PIL-dispersion significantly increased the permittivity e′ and dielectric loss e″ and improved the ionic conductivity of the polymer electrolytes compared to PIL-solid. The ionic conductivity of these polymer electrolytes is greatly increased with doping of PIL-dispersion owing to their strong plasticizing effect. The data of electric modulus M″ are analyzed in terms of Havriliak–Negami function through three relaxation mechanisms. In the temperature range from 50 to 150 °C, three distinct relaxation processes, namely α, αβ and β relaxations were detected in all samples. Polymer electrolytes based on hydrophilic PIL showing ionic conductivities in the range of 10−9–10−5 S/cm are good candidates in construction of electrochemical cells, whereas those based on hydrophobic PIL are suitable for use in liquid membranes.

Mechanical and Electrical Properties of Elastomer Nanocomposites Based on Different Carbon Nanomaterials

Carbon nanostructures including carbon black, carbon nanotubes, graphite or graphene have attracted a tremendous interest as fillers for elastomeric compounds. The preparation methods of nanocomposites that have a strong impact on the state of filler dispersion and thus on the properties of the resulting composites, are briefly described. At a same filler loading, considerable improvement in stiffness is imparted to the host polymeric matrix by the carbon nanomaterials with regard to that provided by the conventional carbon black particles. It is mainly attributed to the high aspect ratio of the nanostructures rather than to strong polymer-filler interactions. The orienting capability of the anisotropic fillers under strain as well the formation of a filler network, have to be taken into account to explain the high level of reinforcements. A comparison of the efficiency of the different carbon nanostructures is carried out through their mechanical and electrical properties but no clear picture can be obtained since the composite properties are strongly affected by the state of filler dispersion.

Polymer electrolytes for lithium ion batteries: a critical study

Polymer electrolytes (PEs) are an essential component being used in most energy storage/conversion devices. The present review article on a brief history, advantage, and their brief application of polymer electrolyte systems. It consists of a glimpse on liquid, gel, and solid polymer electrolyte and a contrast comparison concerning benefits/disadvantages among the three. The article started with a brief introduction of polymer electrolytes followed by their varieties and extreme uses. The role of host polymer matrix by taking numerous examples of polymer electrolyte published by the different renowned group of the concerned field has been explored. The criteria for selection of appropriate host polymer, salt, inorganic filler/clay, and aprotic solvents to be used in polymer electrolyte have been discussed in detail. The mostly used polymer, salt, solvents, and inorganic filler/clay list has been prepared in order to keep the data bank at one place for new researchers. This article comprises different methodologies for the preparation of polymer electrolyte films. The different self-proposed mechanisms (like VTF, WLF, free volume theory, dispersed/intercalated mechanisms, etc.) have been discussed in order to explain the lithium ion conduction in polymer electrolyte systems. A numerous characterization techniques and their resulting analysis have been summarized from the different published reports at one place for better awareness of the scientific community/reader of the area.

Plasticized polymer electrolyte membranes based on PEO/PVdF-HFP for use as an effective electrolyte in lithium-ion batteries

Plasticized polymer electrolytes were prepared using poly(ethylene oxide) (PEO)/poly(vinylidene fluoride-hexafluoro propylene) (PVdF-HFP) with lithium perchlorate (LiClO4) and different plasticizers. XRD and FTIR spectroscopic techniques were used to characterize the structure and the complexation of plasticizer with the host polymer matrix. The role of interaction between polymer hosts and plasticizer on conductivity is discussed using the results of alternating current (a.c.) impedance studies. TG-DTA and SEM were used for thermal and physical characterizations. Maximum ionic conductivity (3.26 × 10−4 S·cm−1) has been observed for ethylene carbonate (EC)-based polymer electrolytes. Electrochemical performance of the plasticized polymer electrolyte is evaluated in LiFePO4/plasticized polymer electrolytes (PPEs)/Li coin cell. Good performance with low capacity fading on charge discharge cycling is demonstrated.

Increasing the horizontal orientation of transition dipole moments in solution processed small molecular emitters.

The efficiency of organic light emitting diodes (OLEDs) can be improved by controlling the orientation of the transition dipole moment of the emitters. Currently, no effective methods exist for orienting the transition dipole moments in solution processed active layers for OLEDs. We investigate the orientation of the transition dipole moment of small molecular emitters in a host matrix of poly(9,9-dioctylfluorene) (PFO) by means of angle dependent luminescence intensity measurements. The polymer chains of the host orient predominantly in the plane of the film. Fluorescent p-phenylenevinylene oligomers with 6 and 7 repeat units (OPV6, OPV7) are found to also orient preferentially horizontally. The orientation of the emitters can be improved by thermal annealing with up to 90% of transition dipole moments oriented in the plane of the film. The phosphorescent emitter Ir(MDQ)2(acac) shows a degree of horizontal orientation in the polymeric host matrix lower than that which is observed for oligomers, but as high as is observed for the same emitter in evaporated layers. A carbazole derivative capable of thermally activated delayed fluorescence shows a small preference for vertical orientation within the polymer host. The strong orientation of OPV6 and OPV7 in the oriented polymer host is rationalized in terms of their high aspect ratios. The use of PFO as host material in host/guest systems allows achieving horizontal orientation of transition dipole moments in solution processed oligomers and small molecular emitters.

Optical response of heterogeneous layer containing silver nanospheres and nanoprisms

This study focuses on the control of the light matter phenomenon in the visible wavelength range. In order to absorb the incoming light, silver nanospheres and nanoprisms are chemically synthesized and embedded in a non-absorbing and transparent polymer host matrix. By combining nanospheres and nanoprisms in the same thin film layer, the plasmonic absorption peaks of nanospheres and nanoprisms are combined. Aggregates of nanospheres and nanoprisms lead to a redshift and broaden the absorbance peak, as expected by finite difference time domain simulations.

Preparation and properties of polyamide 6 nanocomposites covalently linked with amide functional graphene oxide

Chemically engineered polyamide 6 (PA6)/graphene oxide (GO) nanocomposites were produced via the functionalization of GO with an amide (CONH2) functional group, in order to produce amide-GO with improved interfacial bonding and dispersion in the host polymer matrix. In situ polymerization of ε-caprolactam was carried out in the presence of amide-GO to create PA6/amide-GO nanocomposites. The nanomaterial (pre- and post-polymerization) and the composites were characterized using transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC) and tensile testing. The single-layer nature of GO was attested by TEM. FTIR, XPS, XRD and thermal analysis techniques confirmed the successful amide modification of GO. The expected attachment of PA6 to the surface of GO is demonstrated, along with the reduction of GO during polymerization. Some reduction of GO during the chemical functionalization process was also observed. The thermal stability of the nanocomposites was confirmed, while promotion of α-phase crystallite formation and a molecular weight change of attached PA6 are observed. A linear improvement in stiffness and yield strength was observed as functionalized GO content increased from 0.1 wt% to 0.75 wt%. A levelling off of mechanical properties ensued once the GO content reached 1 wt%, and a decrease was seen at 2 wt%.

The Orange Side of Disperse Red 1: Humidity-Driven Color Switching in Supramolecular Azo-Polymer Materials Based on Reversible Dye Aggregation.

Humidity detection, and the quest for low-cost facile humidity-sensitive indicator materials is of great interest for many fields, including semi-conductor processing, food transport and storage, and pharmaceuticals. Ideal humidity-detection materials for a these applications might be based on simple clear optical readout with no power supply, i.e.: a clear color change observed by the naked eye of any untrained observer, since it doesn't require any extra instrumentation or interpretation. Here, the introduction of a synthesis-free one-step procedure, based on physical mixing of easily available commercial materials, for producing a humidity memory material which can be easily painted onto a wide variety of surfaces and undergoes a remarkable color change (approximately 100 nm blue-shift of λMAX ) upon exposure to various thresholds of levels of ambient humidity is reported. This strong color change, easily visible to as a red-to-orange color switch, is locked in until inspection, but can then be restored reversibly if desired, after moderate heating. By taking advantage of spontaneously-forming reversible 'soft' supramolecular bonds between a red-colored azo dye and a host polymer matrix, a reversible dye 'migration' aggregation appearing orange, and dis-aggregation back to red can be achieved, to function as the sensor.

Effect of silicon powder on the optical characterization of Poly(methyl methacrylate) polymer composites

The polymer composite films of Poly(methyl methacrylate) (PMMA) doped with different wt% of Silicon powder (Si) were prepared using solution casting technique, to investigate the effect of Si content on the optical characterization of PMMA matrix. It is found that the fundamental optical absorption edge of PMMA is shifting toward lower energy with the increase of the Si content, resulting the decreases in the optical band gap of PMMA monotonously. The optical constants of PMMA:Si composite, such as the optical absorption coefficient, refractive index, extinction coefficient and complex dielectric constant, are greater than those of pure PMMA. The energy dispersion parameters of PMMA:Si composite versus Si wt% have been determined and explained using Wemple-DiDomenico single oscillator model. The linear relationship between the static refractive index and Si volume fraction reveal the well-dispersed Si powder in the PMMA host polymer matrix. The SEM micrographs also revealed the uniform dispersion of Si powder in PMMA matrix. The observed improve in the optical properties of PMMA:Si films denote that this composite could be used in UV-blocking contact lenses and optoelectronic devices.

Efficient coloration and decoloration reactions of fast photochromic 3H–naphthopyrans in PMMA-b-PBA block copolymer

Fast photochromic molecules have attractive potential to apply to the ophthalmic lenses and real-time dynamic holography. However, the thermal decoloration reaction rate and the photoconversion efficiency of the photochromic molecules largely depend on their surrounding medium. Herein, we investigated the thermal decoloration behavior of fast photochromic 3H–naphthopyrans in poly(methyl methacrylate)-b-poly(n-butylacrylate) (PMMA-b-PBA) block copolymer. The rapid photoswitching properties of the fast photochromic molecules were achieved by using the block copolymer as a host polymer matrix.

Advanced Compositional Analysis of Nanoparticle-polymer Composites Using Direct Fluorescence Imaging.

The fabrication of polymer-nanoparticle composites is extremely important in the development of many functional materials. Identifying the precise composition of these materials is essential, especially in the design of surface catalysts, where the surface concentration of the active component determines the activity of the material. Antimicrobial materials which utilize nanoparticles are a particular focus of this technology. Recently swell encapsulation has emerged as a technique for inserting antimicrobial nanoparticles into a host polymer matrix. Swell encapsulation provides the advantage of localizing the incorporation to the external surfaces of materials, which act as the active sites of these materials. However, quantification of this nanoparticle uptake is challenging. Previous studies explore the link between antimicrobial activity and surface concentration of the active component, but this is not directly visualized. Here we show a reliable method to monitor the incorporation of nanoparticles into a polymer host matrix via swell encapsulation. We show that the surface concentration of CdSe/ZnS nanoparticles can be accurately visualized through cross-sectional fluorescence imaging. Using this method, we can quantify the uptake of nanoparticles via swell encapsulation and measure the surface concentration of encapsulated particles, which is key in optimizing the activity of functional materials.

High-Permittivity and Low-Loss Electromagnetic Composites Based on Co-fired Ba0.55Sr0.45TiO3 or MgCaTiO2 Microfillers for Additive Manufacturing and Their Application to 3-D Printed K-Band Antennas

Six types of high-permittivity and low-loss electromagnetic (EM) composites based on a polydimethylsiloxane (PDMS) or cyclo-olefin polymer (COP) host matrix, reinforced by Ba0.55Sr0.45TiO3 or MgCaTiO2 microparticle fillers with volume loading concentration up to 49 vol. %, have been prepared and characterized up to 20 GHz using cavity resonators. These high dielectric permittivity (high-k) ceramic powders were sintered at temperatures up to 1,500°C to further enhance their dielectric properties. The 49 vol. % loaded PDMS-Ba0.55Sr0.45TiO3 composites with 1,340°C sintered fillers have a relative permittivity (ɛr) of 23.51 and a loss tangent (tanδd) <0.047 at frequencies up to 20 GHz. Meanwhile, the 39 vol. % loaded PDMS-Ba0.55Sr0.45TiO3 composites with 1,340°C sintered fillers have a ɛr of 15.02 and a tanδd <0.042 at frequencies up to 16 GHz. On the other hand, the 37 vol. % loaded PDMS-MgCaTiO2 composites with 1,100°C sintered fillers have an ɛr of 12.19 and a tanδd <0.021 at frequencies up to 20 GHz. The 49 vol. % loaded PDMS-MgCaTiO2 composite specimen has a measured ɛr of 16.33 and tanδd <0.021 between 0.4 and 20 GHz. In addition, thin-sheet specimens made of 25 vol. % COP-MgCaTiO2 prepared by fused deposition modeling have a ɛr of 4.74 and a tanδd <0.0018 up to 17 GHz. Similarly, 25 vol. % COP-Ba0.55Sr0.45TiO3 samples have a ɛr of 4.92 and a tanδd <0.0115 at frequencies up to 17 GHz. For demonstration of a device prototype, a 19.6-GHz microstrip patch antenna was printed by employing a molded PDMS-MgCaTiO2 composite substrate and microdispensed silver ink (CB028) to form the conductive layer, achieving a 20-dB return loss and ~10% bandwidth. Evidently, these newly developed polymer-ceramic composites are well suited for applications up to the K-band and are amenable to be adopted by 3-D printing technologies.

High-performance light diffuser films by hierarchical buckling-based surface texturing combined with internal pores generated from physical gelation induced phase separation of binary polymer solution

Abstract A simple and low-cost process has been demonstrated for the fabrication of high-performance light diffuser films. Instead of polymer composites with light diffusing micro/nanoparticles as in typical approaches, low refractive-index (RI) air pockets or pores have been included inside the diffuser film, which has large RI contrast to host polymer matrix. The generation of such pores has been enabled by elastomeric polydimethylsiloxane (PDMS) assisted fast drying of binary polymer solution, where physical gelation induced phase separation generates pores inside the dried film. To further increase the light scattering and thus the optical haze of such diffuser films, hierarchical buckling of PDMS surface by oxygen plasma treatment has been applied. The buckled PDMS could be directly integrated into the PDMS-assisted drying process, thereby enables one to fabricate high-performance diffuser films having both surface-relief patterns and internal pores at the same time. This unique combination of surface and volume scatterings has yielded high-performance light diffusing films with high transmittance and haze simultaneously.

Ac Conductivity and Dielectric Studies of Polypyrrole Copper Zinc Iron Oxide Nanocomposites

Polypyrrole and polypyrrole/copper zinc iron oxide (CuZnFe2O4) nanocomposites are synthesized by in-situ polymerisation in different weight percentages using oxidation method. Dielectric and conductivity behaviours of Polymer nanocomposites of various composition were investigated using impedance spectroscopy at different temperatures and frequencies (100 Hz-5 MHz). The dielectric properties of host polymer matrix have been improved by the addition of nanoparticles and are found to be highly temperature dependent. Both Dielectric constant and Dielectric loss decreased with increase in frequency for all composites, indicating a normal behaviour of dielectrics. Increase in dielectric constant and dielectric loss was observed with respect to temperature, which is attributed to increase in number of dipoles due to thermal energy. Dielectric relaxation is observed at low frequency range, relaxation time is calculated from the dielectric loss peaks. The highest conductivity was observed at 373K for all nanocomposites. The significant increase in dielectric constant makes them a potential candidate for dielectrics in capacitors used for decoupling, timing, filtering, and many other functions.

Synergistic Effect of Functionalized Nanokaolin Decorated MWCNTs on the Performance of Cellulose Acetate (CA) Membranes Spectacular

In order to enhance salt rejection level and high pressure mechanical integrity, functionalized nanokaolin decorated multiwall carbon nanotubes (FNKM, 0–5 wt % loading) were incorporated into a cellulose acetate (CA) matrix using high temperature solution mixing methodology. Scanning electron microscopy (SEM), X-ray diffraction technique (XRD), thermo-gravimetric analyzer (TGA) and Fourier transform infrared spectrometer (FTIR) were used to characterize the prepared membranes. The obtained results revealed that with increasing FNKM concentration in the host polymeric matrix, composite membrane’s structural, functional, thermal, water permeation/flux and salt rejection characteristics were also modified accordingly. Percent enhancement in salt rejection was increased around threefold by adding 5 wt % FNKM in CA.

Insertion behavior of sodium and potassium ions into thin CVD‐SiOx layers by means of a triangular voltage sweep method

The behavior of Na+ and K+ migration upon insertion from a polymeric host matrix into different SiOx layers deposited by chemical vapor deposition is investigated via triangular voltage sweep (TVS) measurements. It is indicated that the quality of the oxide, covering a highly doped silicon substrate, has a major influence on the applied bias for transferring ions into and through the insulator. The investigations show the impeding effect of ion insertion as a result of different SiOx qualities. Comparison of the calculated ion dose from TVS and time of flight secondary ion mass spectrometry depth profiling data reveals quantitative capture of the inserted ion species at the SiOx/Si interface. Furthermore, insight into the ion mobility and the reversibility of the migration effect is given by the inversion of the sweep polarity during TVS. Copyright © 2016 John Wiley & Sons, Ltd.

Nanocomposites of Hydrophobized Cellulose Nanocrystals and Polypropylene

Cellulose nanocrystals (CNCs) are high-strength sustainable nanomaterials, the incorporation of which to a host polymer matrix can potentially lead to nanocomposites with superior mechanical properties. However, the mismatch in surface energy of CNCs and common structural polymers is a challenge that needs to be overcome to prevent the aggregation of CNCs and ensure the robust integration of CNCs into a polymer matrix. Herein, we report an approach involving the functionalization of CNCs with maleated-anhydride polypropylene (MAPP) through diethylenetriamine (DETA) linkers to significantly enhance the compatibility between CNCs and polypropylene. Polypropylene/modified CNC nanocomposites displayed 74% and 76% increase in elastic modulus in comparison to neat polypropylene and polypropylene/untreated CNC nanocomposites, respectively. The tensile strength was also higher for nanocomposites withmodified CNC than neat polypropylene, as well as nanocomposites with untreated CNCs. The tensile strength at 5.5% strain of polypropylene/modified CNCnanocomposites was 32% and 28% larger that of polypropylene and polypropylene/untreated CNC nanocomposites, respectively. Finally, such CNC-based nanocomposites have a lower density than many competitive systems resulting in opportunities to propagate this environmentally-responsible technology to nanocomposites used in additive manufacturing, automotive applications, construction materials and consumer products.

Electrochemical and structural properties of a polymer electrolyte system based on the effect of CeO2 nanofiller with PVDF-co-HFP for energy storage devices

In the present work, a series of five different nanocomposite polymer electrolytes (NCPEs) have been reported with varying contents of ceria, CeO2 nanofiller suitably incorporated within an optimized composition having 75:25 wt% ratio of poly(vinylidenefluoride-co-hexafluoropropylene) [(PVDF-co-HFP)] and zinc trifluoromethanesulfonate (ZnTf) in the form of films obtained by mean of solution casting technique with a general formula [75 wt% PVDF-co-HFP:25 wt% ZnTf]-x wt% CeO2 where x = 1, 3, 5, 7, and 10, respectively. The chosen NCPE system is found to exhibit the maximum electrical conductivity of 3 × 10−4 S cm−1 for 5 wt% loading of CeO2 nanofiller at ambient temperature. The observed conductivity enhancement has been attributed to the occurrence of an increase in the amorphous content as confirmed by X-ray diffraction (XRD) analysis. Detailed Fourier transform infrared (FTIR) spectral analysis has indicated the feasibility of complexation of the host polymer matrix with ZnTf salt and CeO2 nanofiller. The incorporation of CeO2 nanofiller has further increased the decomposition voltage of the polymer electrolyte from 2.4 to 2.7 V as revealed from the voltammetric studies performed on such NCPEs, thereby suggesting the suitability of these NCPE films with an enhanced electrical conductivity as new electrolytes in order to design and fabricate eco-friendly zinc rechargeable batteries and other electrochemical devices.

Temperature dependent dielectric and conductivity studies of polyvinyl alcohol-ZnO nanocomposite films by impedance spectroscopy

Dielectric and conductivity behaviors of nano ZnO doped polyvinyl alcohol (PVA) composites for various concentrations of dopant were investigated using impedance spectroscopy for a wide range of temperatures (303 K–423 K) and frequencies (5 Hz–30 MHZ). The dielectric properties of host polymer matrix have been improved by the addition of nano ZnO and are found to be highly temperature dependent. Anomalous dielectric behavior was observed in the frequency range of 2.5 MHz–5 MHz. Increase in dielectric permittivity and dielectric loss was observed with respect to temperature. The Cole-Cole plot could be modeled by low resistance regions in a high resistance matrix and the lowest resistance was observed for the 10 mol. % films. The imaginary part of the electric modulus showed asymmetric peaks with the relaxation following Debye nature below and non-Debye nature above the peaks. The ac conductivity is found to obey Jonscher's power law, whereas the variation of dc conductivity with temperature was found to follow Arrhenius behavior. Two different activation energy values were obtained from Arrhenius plot indicating that two conduction mechanisms are involved in the composite films. Fitting the ac conductivity data to Jonscher's law indicates that large polaron assisted tunneling is the most likely conduction mechanism in the composites. Maximum conductivity is observed at 423 K for all the samples and it is optimum for 10 mol. % ZnO doped PVA composite film. Significant increase in dc and ac conductivities in these composite films makes them a potential candidate for application in electronic devices.

Electrical and mechanical properties of graphene/carbon nanotube hybrid nanocomposites

Polymer nanocomposites with improved electrical and mechanical properties can be formulated by proper dispersion of conductive high aspect ratio nanofiller within the host polymer matrix. In this work, the microstructure, processing behavior, electrical and mechanical properties of melt-mixed graphene nanoplatelets (GNP)/polypropylene (PP) nanocomposites were investigated. In addition, the influence of processing conditions on the electrical properties of GNP/PP nanocomposites was evaluated. Moreover, GNP: carbon nanotube (CNT)/PP hybrids were prepared aiming at formulating nanostructured material with synergistic properties. The electrical percolation threshold of GNP/PP nanocomposite was found to be ∼4vol%. However, upon the introduction of only 1wt% (0.52vol%) CNT, significant improvement in the electrical properties was obtained. The CNT was found to bridge the distance between the GNP particles. At constant overall nanofiller concentration, GNP:CNT/PP hybrids exhibited improved properties with the increase in CNT volume fraction due to the better dispersion of nanotubes and strong adhesion at the nanotube/PP interface.