PVDF-Based Nanocomposite Solid Polymer Electrolytes; the Effect of Affinity Between PVDF and Filler on Ionic Conductivity

Nanocomposite solid polymer electrolytes (NSPEs) based on poly(vinylidene fluoride) (PVDF) were prepared by dispersing two kinds of organoclay (Cloisite^® 30B, Cloisite^® 15A) consisting of silicate layers in the polymer matrix. The effect of affinity between PVDF and organoclay as the filler on ionic conductivity was investigated in relation to its content, dispersed condition of organoclay, and structural changes of nanocomposites. The characterizations of PVDF-based nanocomposites with various organoclay contents were carried out by XRD, TEM, DSC, and DMA. In order to confirm the ion conduction properties of NSPEs with LiCF₃SO₃ at room temperature, ac impedance analyzer and FT-IR spectrometer were used. As a result, a higher ionic conductivity appeared in the case of NSPE with C15A than that with C30B and the maximum conductivity was 1.04 × 10^–3 S/cm for the NSPE containing 5 wt% of C15A and 40 wt% of LiCF₃SO₃.     

Silver ion beam irradiation effects on poly(lactide-co-glycolide) (PLGA)/clay nanocomposites

Swift heavy ions induced modification of thin films of blends of poly(lactide-co-glycolide) (PLGA) (50:50) with organically modified nanoclay (Cloisite^® 30B) has been studied, using optical, structural and surface morphological analysis. Presence of nanoclay is found to enhance the properties of this degradable copolymer by reducing the rate of degradation even at high irradiation fluence. Optical and structural analysis of the polymer nanocomposites suggests that both the cross-linking and chain scission phenomenon are caused by swift heavy ion irradiation. XRD measurements show intercalation of PLGA in the clay galleries. Surface morphology of a nanocomposite indicates significant changes after irradiation at various fluences.     

Synthesis and Characterization of Novel Poly(1‐Naphthylamine)‐Montmorillonite Nanocomposites Intercalated by Emulsion Polymerization

Nanocomposites of montmorillonite (MMT) with poly(1‐naphthylamine) (PNA) is investigated for the first time by emulsion polymerization using three different oxidants. Polymerization of PNA was confirmed by Fourier transformation infrared (FT‐IR) as well as UV‐visible spectra. The in situ intercalative polymerization of PNA within MMT layers was confirmed by FT‐IR, X‐ray diffraction, conductivity; scanning electron microscopy (SEM) as well as transmission electron microscopy studies. X‐ray diffraction revealed intercalated as well as exfoliated structures of PNA/MMT nanocomposites, which were compared with the reported polyaniline‐MMT nanocomposites. It was found that the increase in the concentration of PNA in the interlayer galleries of MMT led to destruction of the layered clay structure resulting in exfoliation of the nanocomposite. Conductivity of the nanocomposites was found to be in the range of 10^?3 to 10^?2 S cm^?1 which was found to be higher than the ones reported for polyaniline‐clay nanocomposites as well as PEOA‐OMMT nanocomposites at similar concentrations of intercalated species. The morphology of PNA/MMT nanocomposites was found to be governed by the nature of the oxidant used.     

Morphology and Properties of Poly(vinyl alcohol)/MMT Nanocomposite Prepared by Solid-state Shear Milling (S3M)

Poly(vinyl alcohol) (PVA)/montmorillonite (MMT) nanocomposites were prepared by combining solid-state shear milling (S³M) technology with melt intercalation. Compared with the composite obtained by simple melt intercalation, more MMT layers were exfoliated and apparently oriented along the injection molding direction in the nanocomposite prepared by combining S³M technology and melt intercalation, which greatly increased the orientation degree of MMT, resulting in the greater interactions between PVA and MMT layers. Simultaneously, this also promoted the orientation of PVA molecules and produced effective nucleation of the crystallization of PVA. Consequently, the thermal stability and mechanical properties of PVA were obviously improved. For instance, when the MMT content was 3 wt%, the tensile strength and modulus of the nanocomposite with MMT prepared by S³M were 98.9 MPa and 3.1 GPa, respectively, increasing by 52% and 63.2% compared with PVA.     

Effect of surface treatment of nanoclay on the mechanical properties of epoxy/glass fiber/clay nanocomposites

A new method of silane treatment of nanoclays is reported where in the clay is nanodispersed in hydrolyzed silanes. The surface functionalization of Cloisite^® 15A nanoclay has been carried out using two different silane coupling agents: 3-aminopropyltriethoxy silane and 3-glycidyloxypropyltrimethoxy silane using varied amounts of silane coupling agents, e.g. 10, 50, 200, and 400 wt% of clay. The surface modification of Cloisite^® 15A has been confirmed by Fourier transform infrared spectroscopy. The modified clays were then dispersed in epoxy resin, and glass fiber-reinforced epoxy clay laminates were manufactured using vacuum bagging technique. The fiber-reinforced epoxy clay nanocomposites containing silane modified clays have been characterized using small angle X-ray scattering, transmission electron spectroscopy and differential scanning calorimetry. The results indicate that the silane treatment of nanoclay aided the exfoliation of nanoclay and also led to an increase in mechanical properties. The optimized amount of silane coupling agents was 200 wt%. The nanocomposites containing clay modified in 200 wt% of silanes exhibited an exfoliated morphology, improved tensile strength, flexural modulus, and flexural strength. The improved interfacial bonding between silane modified nanoclays and epoxy matrix was also evident from significant increase in elongation at break.     

Nonisothermal Crystallization Kinetics of Poly(ϵ-Caprolactone)/Montmorillonite Nanocomposites

Montmorillonites modified by hydroxyethylhexadecyldimethyl ammonium bromine were used to prepare poly(?-caprolactone) (PCL)/montmorillonite (MMT) nanocomposites by in situ ring-opening polymerization of ?-caprolactone. Wide-angle X-ray diffraction (WAXD) analysis illustrated that an exfoliated structure of PCL/MMT nanocomposite was obtained. The nonisothermal crystallization kinetics of poly(?-caprolactone) and PCL/MMT nanocomposite was investigated by differential scanning calorimetry (DSC) at various cooling rates. The values of half-time of crystallization (t_1/2) and crystallization rate constant (Z_c) showed that crystallization rate increased with the increase of cooling rates for both PCL and PCL/MMT nanocomposite; however, the crystallization rate of PCL/MMT nanocomposite was faster than that of PCL at a given cooling rate.     

Silicon/carbon nanocomposites used as anode materials for lithium-ion batteries

Silicon/carbon nanocomposites are prepared by dispersing nano-sized silicon in mesophase pitch and a subsequent pyrolysis process. In the nanocomposites, silicon nanoparticles are homogeneously distributed in the carbon networks derived from the mesophase pitch. The silicon/carbon nanocomposite delivers a high reversible capacity of 841 mAh g^?1 at the current density of 100 mA g^?1 at the first cycle, high capacity retention of 98 % over 30 cycles, and good rate performance. The superior electrochemical performance of nanocomposite is attributed to the carbon networks with turbostratic structure, which enhance the conductivity and alleviate the volume change of silicon.     

Polymer Dynamics in Polyurethane/clay Nanocomposites Studied by Dielectric and Thermal Techniques

Differential scanning calorimetry (DSC), broadband dielectric relaxation spectroscopy (DRS), and thermally stimulated depolarization current (TSDC) techniques were employed to investigate glass transition and polymer dynamics in nanocomposites of polyurethane (PU) and organically modified montmorillonite (MMT) (weight fraction 0%–15%) prepared by solution casting. The PU matrix was obtained from oligo(oxytetramethylene glycol) of molar mass 1000 g/mol, 4,4′-diphenylmethane diisocyanate and 1,1-dimethylhydrazine as chain extender. Wide-angle X-ray scattering confirmed the formation of partly exfoliated structures at low MMT content. DSC, DRS, and TSDC show, in agreement with each other, that a fraction of polymer makes no contribution to the glass transition and to the corresponding α relaxation, whereas the rest exhibits similar glass transition dynamics as the pure matrix. This fraction of immobilized polymer reaches a maximum at about 5 wt% MMT. Effects of MMT on the microphase-separated structure of PU are negligible, as indicated by the study of glass transition and interfacial dielectric polarization/relaxation. No effects of MMT on the local, secondary γ and β relaxations were observed. Mechanical properties show a maximum improvement at about 5 wt% MMT, in good correlation with morphology and dynamics.     

Synthesis and characterization of polyurethane/SiO2 nanocomposites

In order to achieve good dispersion of nano-SiO₂ and increase the interactions between nano-SiO₂ and PU matrix, nano-SiO₂ was firstly modified with poly(propylene glycol) phosphate ester (PPG-P) which was a new polymeric surfactant synthesized through the esterification of poly(propylene glycol) (PPG) and polyphosphoric acid (PPA). Then a series of polyurethane (PU)/SiO₂ nanocomposites were prepared via in situ polymerization. The surface modification of nano-SiO₂, the microstructure and the properties of nanocomposites were investigated by FTIR, SEM, XRD and TGA. It was found that good dispersion of nano-SiO₂ achieved in PU/SiO₂ nanocomposite after the modification with PPG-P. The segmented structures of PU were not interfered by the presence of nano-SiO₂ in these nanocomposites.     

In Situ Synthesis and Characterization of Polypyrrole/Graphene Conductive Nanocomposites via Electrochemical Polymerization and Chemical Reduction

Polypyrrole/graphene sheets (PPy/GNs) nanocomposite electrodes were in- situ synthesized via electrochemical polymerization and chemical reduction from pyrrole (Py) and graphene oxide (GO). The surface morphologies of the nanocomposites were observed by scanning electron microscopy (SEM). The SEM results showed graphene sheets (GNs) scattered on the surface of the polypyrrole (PPy), and the morphologies of PPy/GNs nanocomposites manufactured by pulse current (PC-PPy/GNs) or direct current (DC-PPy/GNs) were smoother than that of PC-PPy. The electrochemical capacitance properties of the nanocomposite films were measured by cyclic voltammetry (CV), galvanostatic charge and discharge (GC), and electrochemical impedance spectroscopy (EIS) techniques in 3 mol·L^?1 KCl aqueous solutions. The results indicated that the specific capacitance of the DC-PPy/GNs nanocomposite was 13.5% higher than that of a PC-PPy electrode. Comparison of the electrochemical performance of the nanocomposites indicated that the PC-PPy/GNs nanocomposite had higher specific capacitance and better charging/discharging capability than that of the DC-PPy/GNs nanocomposite. The specific capacitance of the PC-PPy/GNs nanocomposite could reach to 280 F·g^?1 at a scanning rate of 100 mV·s^?1.     

Preparation and Characterization of Silicon-containing Polyarylacetylene/montmorilloite Nanocomposites

Dimethylphenylpropargyl ammonium bromide (DMPPAB) was synthesized and used to modify pristine montmorillonite (MMT) by a cation exchange process. The organically modified montmorillonite (OMMT) was verified and used to mix with a silicon-containing polyarylacetylene (PSA) as well as MMT. The PSA/MMT and PSA/OMMT nanocomposites were prepared by solution under sonication and melting intercalation processes, respectively, and then cured by a step heating process. The thermal and flexural properties of the cured PSA and nanocomposites were studied by thermogravimetric and dynamic mechanical analysis. The results showed that the intercalation of DMPPAB into the MMT galleries made the d-spacing enlarge. During PSA curing, the cure heat of PSA caused the MMT and OMMT to delaminate and exfoliate in the PSA matrix. The glass transition temperature of the cured PSA and nanocomposites were higher than 500?°C. The inner acetylenic groups in the PSA resin could further crosslink above 300?°C. The temperature at 5% mass loss of the cured PSA decreased by 4.6% with 3% mass fraction of OMMT loading, and the char yield of the cured PSA changed only slightly. The flexural strength of the cured PSA was augmented with addition of MMT or OMMT, but the flexural modulus of the cured PSA decreased slightly. The flexural strength of the cured nanocomposite increased from 20.1?MPa to 30.1?MPa when 3% mass fraction of OMMT was added into the PSA matrix.     

Polycyanurate–Organically Modified Montmorillonite Nanocomposites: Structure–Dynamics–Properties Relationships

Polycyanurate‐modified montmorrilonite (PCN‐MMT) nanocomposites were synthesized by polymerization of dicyanate ester of bisphenol A in the presence of MMT dispersed by ultrasound. Techniques of IR spectroscopy, WAXD, and TEM were applied to study polymerization kinetics and structure of the nanocomposites prepared, whereas their dynamics and thermal/mechanical properties over the ?30 to 420°C range were studied by using DSC, laser‐interferometric creep rate spectroscopy (CRS), and dielectric relaxation spectroscopy (DRS) techniques. It was shown that a small amount of MMT additive acts as a catalyst of polymerization and results in the formation of complicated intercalated/exfoliated structures, as well as strongly modifies the dynamics in the PCN network. Pronounced dynamic heterogeneity was observed for PCN/MMT nanocomposites. Along with the main PCN glass transition, two new glass transitions, at much higher and much lower temperatures, were revealed as a consequence of constrained dynamics in matrix interfacial nanolayers and due to incomplete local cross‐linking in the PCN matrix, respectively. In addition, increased sub‐T _g mobility was observed in these nanocomposites. A two‐fold rise of modulus of elasticity as well as increasing thermal stability and arising microplasticity at low temperatures, promoting, obviously, improved crack resistance in a brittle PCN network, were found for the PCN‐MMT nanocomposites.     

The preparation of vanadium-doped TiO2-montmorillonite nanocomposites and the photodegradation of sulforhodamine B under visible light irradiation

The photodegradation of sulforhodamine B on vanadium-doped TiO₂-montmorillonite (TiO₂-MMT) nanocomposites was investigated under visible light irradiation. V-TiO₂-MMT nanocomposites with different amounts of MMT were prepared by a sol-gel process. The microstructure and properties of V-TiO₂-MMT were characterized by XRD, TEM, XPS, DRS, nitrogen adsorption isotherms, and FTIR. These analytic results indicated that the different Ti/MMT ratios exerted a great influence on their microstructures and their photocatalytic activities. The average sizes of V-TiO₂-MMT were smaller than those of pure TiO₂ and V-TiO₂. And the layered structure of MMT was completely destroyed in the V-TiO₂-MMT with the relatively high ratio of Ti/MMT (240, 120, 80, 60 mmol/g), but it retained the partial MMT layered structure and had an enlargement of some basal space of MMT in V-TiO₂-MMT with the relatively low ratio of Ti/MMT (30, 24 mmol/g). V-TiO₂-MMT/120 (120 denotes the ratio of Ti/MMT is 120 mmol/g. The names of other catalysts followed the same convention.) and V-TiO₂-MMT/30 had relatively higher photocatalytic activity in comparison to the others. Besides, in the preparation process, we selected V-TiO₂-MMT/120 using different washing media to examine the effect of washing medium on the photocatalytic activity. The result indicated that it was critical to choose a proper washing medium to obtain an optimal photocatalytic activity.     

Actuation behavior of waterborne polyurethane/conductive filler nanocomposite electrode

This study dealt with the Maxwell stress effect of waterborne polyurethane (WPU)/conductive filler nanocomposite, which was a promising candidate for a material to be used in a dielectric elastomer actuator electrode. Conductive nanocomposites were produced by using three types of conductive filler: carbon black (CB), vapor grown carbon fiber (VGCF), and silver powder (Ag). Among them, conductive nanocomposite containing VGCF exhibited the lowest threshold concentration; and the mixture of CB and VGCF (CB/VGCF) filler had a synergistic effect to electrical conductivity. Actuation test revealed that CB/VGCF nanocomposite electrode had the largest displacement. Then it could be stated that the improvement of the displacement in CB/VGCF nanocomposite electrode originated from the increase in relative dielectric constant. In addition, a unique feature for the hysteresis of bending deformation was observed. This feature is that the prior application of an electric field significantly improves the bending speed in the successive application. Also, the effect of electrode thickness on the displacement and breakdown strength was examined.     

Fabrication of rare-earth/quantum-dot nanocomposites for color-tunable sensing applications

We developed a new fluorescent nanocomposite by using a layer-by-layer approach to link NaYF₄:Ce,Tb rare-earth (RE) nanocrystals and CdSe/ZnSe semiconductor quantum dots (QDs) with opposite charges. Under ultraviolet light excitation, the nanocomposites exhibited both the green Tb emission centered at 550 nm, and the red QD emission at 650 nm. Sensing applications showed that the red QD emission was quenched by trace amount of Cu²⁺ (or Ag⁺) ions due to the ion displacement mechanism, while the green RE emission kept constant. Thus, the nanocomposites with the decreased QD/RE emission intensity ratio and changed fluorescence output color provided a visible “indicator” to detect metal ions quantificationally. In comparison with single emission materials, the dual emission nanocomposites can be a more reliable probe for various sensing applications.     

Electrical Impedance Spectroscopic Study of CNT/Ethylene-alt-CO/Propylene-alt-CO Polyketones Nanocomposite

Impedance spectroscopy was utilized to investigate the dielectric properties, ac conductivity and charge transport mechanisms in propylene-alt-CO/ethylene-alt-CO (EPEC) random terpolymer filled with multi-walled carbon nanotubes (MWCNT) as a function of nanofiller content, frequency, and temperature. Equivalent resistor-capacitor (RC) circuit models were proposed to describe the impedance characteristics of the unfilled terpolymer and the nanocomposite at different temperatures. For the nanocomposites, the ac conductivity tended to be frequency independent at low frequencies. At high frequencies, the ac conductivity increased with frequency. The dc conductivity (i.e., plateau of the ac conductivity at low frequencies) at room temperature increased from 10^?9 (Ω·m)^?1 for the unfilled polymer to l0^?3 (Ω·m)^?1 for the 6 wt% MWCNT/EPEC nanocomposite. At low temperatures, the equivalent RC model for EPEC-0 and EPEC-2 was found to consist of a parallel RC circuit. However, for 6 wt% MWCNT/EPEC nanocomposite, an RC model consisting of an R/constant phase element (CPE) circuit and a resistor in series was required to describe the impedance behavior of the nanocomposite.     

ZnO nanoparticles anchored on nitrogen and sulfur co-doped graphene sheets for lithium-ion batteries applications

Herein, we demonstrate a facile one-step hydrothermal synthesis route to anchor ZnO nanoparticles on nitrogen and sulfur co-doped graphene sheets. The detailed material and electrochemical characterization have been carried out to demonstrate the potential of novel ZnO/NSG nanocomposite in Li-ion battery (LIBs) applications. The structure and morphology of nanocomposite were assessed by X-ray diffraction (XRD), Fourier transform infrared (FTIR), thermogravimetric analysis (TGA), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The as-synthesized ZnO/NSG nanocomposite has been studied as anode material in LIBs and delivered a high initial discharge capacity of 1723 mAh g^?1, at the current density of 200 mA g^?1. After 100 cycles, the ZnO/NSG nanocomposites demonstrated a high reversible capacity of 720 mAh g^?1 and coulombic efficiency of 99.8%, which can be attributed to the porous three-dimensional network, constructed by ZnO nanoparticles and nitrogen and sulfur co-doped graphene. Moreover, the designed nanocomposite has shown excellent rate capability and lower charge transfer resistance. These results are promising and encourage further research in the area of ZnO-based anodes for next-generation LIBs.     

Structure and optical properties of Ag/CeO2 nanocomposites

Silver/ceria (Ag/CeO₂) nanocomposites were prepared from Ce(NO₃)₃?6H₂O, AgNO₃, and NH₄OH with different molar ratios through a hydrothermal process, and then were completed by carrying out the precursors calcining at 750 °C for 2 h under air atmosphere. Below 1 % of Ag concentration in Ag/CeO₂ nanocomposites, the Ag crystalline structure does not appear. XRD and TEM results show evidence of two different effects (the agglomeration and the barrier effects) governing the process of crystal growth. HR-TEM image and EDX elemental analysis of the Ag/CeO₂ nanocomposite confirmed that isolated Ag nanocrystals are dispersed in the CeO₂ matrix. The red shifts are attributed to the quantum confinement effect and the valence change of the Ce⁺ ions. Ag nanoparticles can help to improve the absorption of visible light, enhancing the absorption intensity of Ag/CeO₂ nanocomposite. These results are of great significance for the control of microstructure, crystallinity, and applications for the development of nanocomposite materials.     

Ionic transport studies in hyperbranched polyurethane/clay nanocomposite gel polymer electrolytes

In the present work, we report a novel nanocomposite gel electrolytes based on intercalation of hyperbranched polyurethane (HBPU) into organically modified montmorillonite for application in Li-ion batteries. The nanocomposites have been prepared by solution intercalation technique with varying clay loading. The formation of partially exfoliated nanocomposites has been confirmed by X-ray diffraction. Nanocomposites were soaked with 1 M LiCO₄ in 1:1 (v/v) solution of propylene carbonate and diethyl carbonate to get the required gel electrolytes. AC impedance analysis shows that ionic conductivity increases with the increase of clay loading and attains the highest value of 8.3?×?10^?3 S/cm for 5 wt.% clay concentration. Surface morphology of the nanocomposite electrolytes has been examined by SEM analysis. Improvement of electrochemical properties, viz., electrochemical potential window and interfacial stability, is also observed in the clay-loaded HBPU samples.     

Effect of clay silylation on curing and mechanical and thermal properties of unsaturated polyester/montmorillonite nanocomposites

This work focuses on the chemical modification of montmorillonite (MMT) (Cloisite® Na) with compatible silanes, vinyltriethoxysilane (CVTES) and γ-methacryloxypropyltrimethoxysilane (CMPS) in order to prevent agglomeration and to improve montmorillonite interaction with an unsaturated polyester resin matrix seeking to achieve a multifunctional composite. Clays were dispersed in the resin by mechanical stirring and sonication and the nanocomposites were prepared by resin transfer into a mold. The mechanical, morphological, thermal and flammability properties of the obtained composites were compared with those prepared using commercial Cloisite® 30B (C30B) and Cloisite® 15A (C15A) clays. Advantages of using silane-modified clays (CVTES and CMPS) as compared with organic-modified clays (C30B and C15A) can be summarized as similar flexural strength and linear burning rate but higher storage modulus and improved adhesion to the polyester resin with consequent higher thermal deflection temperature and reinforcement effectiveness at higher temperatures. However, organic modified clays showed better dispersion (tendency to exfoliate) and consequently delayed thermal volatilization due to the clay barrier effect.