Enhanced dielectric response in P(VDF‐TrFE) based all‐organic nanocomposites

A nanocomposite with enhanced dielectric response is developed using poly(vinylidene fluoride‐trifluoroethylene) [P(VDF‐TrFE)] as matrix and Chemically modified high dielectric constant organic semiconductor—copper phthalocyanine oligomer (CuPc)—as filler. Transmission electron microscope (TEM)‐observed morphologies reveal that in the nanocomposite the average size of CuPc particles is about 25 nm [1/24 of that of CuPc in physical blend of P(VDF‐TrFE) and CuPc]. The hot‐press nanocomposite film with 15 wt % CuPc can realize a dielectric constant of 540 at 100 Hz. The enhanced dielectric response in the nanocomposite demonstrates the significance of the interface effect in raising the material responses far beyond that expected by simple mixing rules when there is a large dielectric contrast between the polymer matrix and the dielectric filler in the composite. It is also interesting to note that at high frequencies (such as 100 MHz) the nanocomposite has a dielectric constant of ～100 and this value is comparable to those of current materials used in microwave applications. At 105 °C that is near the ferroelectric‐to‐paraelectric phase transition temperature of the P(VDF‐TrFE) ferroelectric, a much higher dielectric constant (about 1200 at 100 Hz) is obtained. © 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 48: 490–495, 2010     

Pressure‐temperature study of dielectric relaxation of a polyurethane elastomer

The effect of hydrostatic pressure up to 1,361 atms on the dielectric properties of a segmented polyurethane elastomer (Dow 2103‐80AE) is studied at temperatures from 0°C to 80°C. The experimental results show that the relaxation time for both the I–process, associated with the molecular motions in the hard segments, and the α–process, associated with the glass transition, increases with pressure, and this shift is more pronounced for the I–process. Besides the glass transition, it is found that the I–process can be described by the Vogel–Fulcher (V–F) and Williams–Landel–Ferry (WLF) relations. At atmospheric pressure, T_g and T₀ for the I–process are 235.9 K and 4.2 × 10³ K, respectively. Based on the V–F and WLF relations and experimental results, it is found that a parameter, C₁, in the WLF relation is independent of the pressure. Thus, a method is introduced to determine the values of both the characteristic transition temperature (T_g) and activation energy (T₀) for the processes at different pressures. As the pressure increases from atmospheric to 1,361 atms, the increase of T_g for the I–process is about 30°C. The results also show that, for both the I– and the α–processes, T₀ decreases with increasing pressure. © 1999 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 37: 983–990, 1999     

Probing the dielectric response of polyurethane/alumina nanocomposites

The dielectric properties of polyurethane (PUR) latex–boehmite alumina nanocomposites were investigated by means of broadband dielectric spectroscopy in the temperature range ?100 °C to 70 °C. The concentration of the filler (alumina) was kept constant at 10 phr for all specimens, whereas the mean particle diameter (namely 220, 90, and 25 nm) of the incorporated nanoparticles varied accordingly. For reasons of comparison, pure PUR was also examined. Four distinct relaxation modes were recorded in the spectra of all systems. They were attributed to interfacial polarization, glass transition (α‐relaxation), local motions of polar side groups, and chain segments (β‐relaxation and γ‐relaxation). All four relaxation processes exhibit a symmetric distribution of relaxation times, which in the case of interfacial polarization, becomes narrower. The intensity of interfacial polarization increases with the reduction of the mean particle diameter indicating enhanced interfacial area. © 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2010     

A simple approach toward low‐dielectric polyimide nanocomposites: Blending the polyimide precursor with a fluorinated polyhedral oligomeric silsesquioxane

This article describes a new and simple method for preparing polyimide nanocomposites that have very low dielectric constants and good thermal properties: simply through blending the polyimide precursor with a fluorinated polyhedral oligomeric silsesquioxane derivative, octakis(dimethylsiloxyhexafluoropropyl) silsesquioxane (OF). The low polarizability of OF is compatible with polyimide matrices, such that it can improve the dispersion and free volume of the resulting composites. Together, the higher free volume and lower polarizability of OF are responsible for the lower dielectric constants of the PI‐OF nanocomposites. This simple method for enhancing the properties of polyimides might have potential applicability in the electronics industry. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 6296–6304, 2008     

Synthesis of imidazolium‐functionalized ionic polyurethane and formation of CdTe quantum dot–polyurethane nanocomposites

A series of positively charged imidazolium‐functionalized ionic polyurethanes (IPUs) were prepared in one‐step polymerization process by polymerization of presynthesized short‐chain imidazolium‐based ionic diol, polyethylene glycols with different molecular weights as long‐chain diols, and toluylene‐2,4‐diisocyanate. The structures of IPUs are confirmed by ¹H NMR analysis, and the thermogravimetric analysis measurement indicates that the IPUs have high degradation temperature. Fluorescent nanocrystal–polymer composites CdTe–IPU can be prepared conveniently, by the electrostatic interaction between positively charged IPUs and the negatively charged aqueous CdTe quantum dots (QDs). UV–vis absorption and photoluminescence spectra indicate the photochemical stability and strong fluorescent emission of CdTe–IPU composites. The quantum yields (QYs) of the composites are high and basically restore the QYs of the pure QDs. In addition, the transmission electron microscopy photographs show that the QDs in composites are uniform (about 3 nm in diameter) and monodisperse. The obtained nanocomposites are powder or elastomers with good film building. The casted CdTe–IPU films are transparent under visible light, and the colors of the composites and their films are vivid under a UV lamp. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

Core–shell functionalized MWCNT/poly(m‐aminophenol) nanocomposite with large dielectric permittivity and low dielectric loss

Core–shell carboxyl‐functionalized multiwall carbon nanotube (c‐MWCNT)/poly(m‐aminophenol) (PmAP) nanocomposite were prepared through in‐situ polymerization of m‐aminophenol (m‐AP) in the presence of MWCNTs, and explicated as a dielectric material for electronic applications. The formation of thin PmAP layer on individual c‐MWCNT with excellent molecular level interactions at interfaces was confirmed by morphological and spectroscopic analyses. Here we conducted a comparative study of the dielectric performances of PmAP based nanocomposite films with pristine MWCNTs and c‐MWCNTs as fillers. Compared to PmAP/MWCNT nanocomposites, the PmAP/c‐MWCNT nanocomposites exhibited higher dielectric permittivity and lower dielectric loss. The well dispersed c‐MWCNTs in PmAP/c‐MWCNT nanocomposite produce huge interfacial area together with numerous active polarized centers (crystallographic defects), which in turn intensified the Maxwell‐Wagner‐Sillars (MWS) effect based on excellent molecular level interactions and thus, produce large dielectric permittivity (8810 at 1 kHz). The percolation threshold of PmAP/c‐MWCNT nanocomposites is found lower than that of the PmAP/MWCNT nanocomposites, which could be attributed to homogeneous distribution of c‐MWCNTs and strong c‐MWCNT//PmAP interfacial interactions in the nanocomposites. Copyright © 2016 John Wiley & Sons, Ltd.     

Effect of process variables on mechanical properties of polyurethane/clay nanocomposites

This paper addresses the effects of operating variables on mechanical properties of polyurethane/clay nanocomposites including tensile strength, abrasion resistance, and hardness. The variables were prepolymer type, clay cation, clay content, and prepolymer–clay mixing time. The experiments were carried out based on the design of experiments using Taguchi methods. The nanocomposites were synthesized via in situ polymerization starting from two different types of prepolymers (polyether‐ and polyester‐types of polyol reacted with toluene diisocyanate), and methylene‐bis‐ortho‐chloroanilline (MOCA) as a chain extender/hardener. Montmorillonite with three types of cation (Na⁺, alkyl ammonium ion, and MOCA) were examined. Among the parameters studied, prepolymer type and clay cation have the most significant effects on mechanical properties. Polyester nanocomposites showed larger improvements in mechanical properties compared to polyether materials due to higher shear forces exerted by polymer matrix on clay aggregates during polymer–clay mixing. The original MMT with Na⁺ cation results in weak improvements in mechanical properties compared to organoclays. It is observed that the stress and elongation at break, and abrasion resistance of the nanocomposite samples can be optimized with 1.5% of clay loading. The morphology and chemical structure of the optimum sample were examined by X‐ray diffraction and FT‐IR spectroscopy, respectively. Copyright © 2009 John Wiley & Sons, Ltd.     

Bio‐based hyperbranched polyurethane/clay nanocomposites: adhesive,mechanical, and thermal properties

The unison of vegetable oil‐based hyperbranched polymers with nanotechnology can unhook myriad of avant‐garde applications of such materials. Thus Mesua ferrea L. seed oil‐based hyperbranched polyurethane (HBPU)/clay nanocomposites and their performance, with special reference to adhesive strength, are reported for the first time. The nanocomposites of the hyperbranched polyurethane with organically modified nanoclay were obtained by ex situ solution technique and cured by bisphenol‐A‐based epoxy with poly(amido amine) hardener system. The partially exfoliated and well‐distributed structure of nanoclay was confirmed by XRD, SEM, and TEM studies. FTIR spectra indicate the presence of H‐bonding between nanoclay and the polymer matrix. Two times improvement in the adhesive strength and scratch hardness, 10 MPa increments in the tensile strength and 112°C more thermo‐stability have been observed without much affecting the impact resistance, bending, and elongation at break of the nanocomposites compared to the pristine epoxy modified HBPU system. Thus, the resulted nanocomposites are promising materials for different advanced applications including adhesive. Copyright © 2009 John Wiley & Sons, Ltd.     

Synthesis and characterization of waterborne polyurethane/polyhedral oligomeric silsesquioxane composites with low dielectric constants

A facile method was developed to synthesize a new type of polyhedral oligomeric silsesquioxane (POSS). It contained a single amine group and seven aliphatic moieties on its corners. FT‐IR, ¹H‐NMR, ¹³C‐NMR, ¹³C‐¹H COSY, and ¹H‐¹H COSY confirmed that cages with eight corners were the main part of the product. This new POSS was used to modify the structure of hexamethylene diisocyanate trimer and then copolymerized with hexamethylene diisocyanate and poly (tetramethylene glycol) to get a serious of waterborne polyurethane (WPU)/POSS hybrid materials with low dielectric constants for microelectronics applications. The results showed that POSS particles were uniformly dispersed in the WPU dispersions. The WPU/POSS films did not show any macrophase separation, even when the POSS content was as high as 16%. As the POSS content increased from 0% to 16%, the tensile strength was increased from 2.3 to 7.3 MPa, the dielectric constant was decreased from about 2.9 to 2.0, and the thermal stability of the WPU/POSS was also improved.     

Effect of polyol structure on the properties of the resultant magnetic polyurethane elastomer nanocomposites

In this study, two types of magnetic polyurethane (PU) elastomer nanocomposites using polycaprolactone (PCL) and polytetramethylene glycol (PTMG) as polyols were synthesized by incorporating thiodiglycolic acid surface modified Fe₃O₄ nanoparticles (TSM‐Fe₃O₄) into PU matrices through in situ polymerization method. TSM‐Fe₃O₄ nanoparticles were prepared using in situ coprecipitation method in alkali media and were characterized by X‐ray diffraction, Fourier Transform Infrared Spectrophotometer, Transmission Electron Microscopy, and Vibrating Sample Magnetometer. The effects of PCL and PTMG polyols on the properties of the resultant PUs were studied. The morphology and dispersion of the nanoparticles in the magnetic nanocomposites were studied by Scanning Electron Microscope. It was observed that dispersion of nanoparticles in PTMG‐based magnetic nanocomposite was better than PCL‐based magnetic nanocomposite. Furthermore, the effect of polyol structure on thermal and mechanical properties of nanocomposite was investigated by Thermogravimetric Analysis and Dynamic Mechanical Thermal Analysis. A decrease in the thermal stability of magnetic nanocomposites was found compared to pure PUs. Furthermore, DMTA results showed that increase in glass transition temperature of PTMG‐based magnetic nanocomposite is higher than PCL‐based magnetic nanocomposite, which is attributed to better dispersion of TSM‐Fe₃O₄ nanoparticles in PTMG‐based PU matrix. Additionally, magnetic nanocomposites exhibited a lower level of hydrophilicity compared to pure PUs. These observations were attributed to the hydrophobic behavior of TSM‐Fe₃O₄ nanoparticles. Moreover, study of fibroblast cells interaction with magnetic nanocomposites showed that the products can be a good candidate for biomedical application. Copyright © 2013 John Wiley & Sons, Ltd.     

Physical and dielectric properties of poly(vinylidene fluoride)/polybenzimidazole functionalized graphene nanocomposites

Polymer‐based nanocomposites with good dielectric behavior have engrossed research devotion because of their distinctive benefits in electronic applications. An in situ synthetic process for the polybenzimidazole functionalized graphene oxide (GBI) and its nanocomposite with poly(vinylidene fluoride) (PVDF) is described. GBI shows good dispersion in the bulk PVDF matrix implying a strong interaction of polybenzimidazole with PVDF as evident from morphological and FTIR studies. A gradual increment of GBI in PVDF increases its piezoelectric β‐polymorph formation with a maximum of 73% for 10 wt % GBI in PVDF (GBF10) which also exhibits highest thermal stability. An exhaustive study of frequency dependent electrical properties of GBF10 indicates significantly higher dielectric constant (61), low dielectric loss (0.42), and low AC conductivity value of 1.17 × 10^?10 S/cm at 100 Hz which are the key properties of a suitable capacitor. GBF10 also shows hydrophobic behavior (water uptake 2.89%) and low swelling ratio (1.143), providing an opportunity to use the composite film in fuel cell application. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2019 , 57, 189–201     

Effect of a post‐annealing process on microstructure and mechanical properties of high‐density polyethylene/silica nanocomposites

High‐density polyethylene (HDPE) and nanosilica nanocomposites were prepared for SiO₂ content up to 15 wt%. Microstructural characterization evidenced a homogenous distribution of silica aggregates with a mean size increasing with the filler content finally resulting in a rheological percolation between 7.5 and 10 wt%. Nanoparticles did not induce any significant impact on the matrix crystallinity but led to a real improvement on elastic properties accompanied with a large embrittlement above the percolation threshold. The effect of annealing near HDPE melting temperature was studied. Differential scanning calorimetry, X‐ray diffraction, and small‐angle X‐ray scattering analyses showed a significant change in the HDPE microstructure after annealing at 125°C. A large increase in the crystallinity (from 68 to 76%) and a clear improvement of Young's modulus (by 55%) were observed prior to polymer degradation. A valuable impact of silica particles on thermal stability was also obvious regarding the evolution of elastic properties for extended exposure times (850–1,200 h). © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2019 , 57, 535–546     

Bio‐based nanocomposites from functionalized plant oils and layered silicate

Some discovery work was done on the synthesis of clay nanocomposites based on renewable plant oils. Functionalized triglycerides, such as acrylated epoxidized soybean oil, maleinized acrylated epoxidized soybean oil, and soybean oil pentaerythritol maleates, combined with styrene were used as the polymer matrix. The miscibility of these monomers and clay organomodifier was assessed by solubility parameters. The formation of nanocomposites was confirmed by both X‐ray data and transmission electron microscopy. The morphology showed a mix of intercalated and partially exfoliated sheets. The flexural modulus increased 30% at only 4 vol % clay content, but there was no significant effect on flexural strength, glass‐transition temperature, and thermal stability. Property enhancement was related to the degree of exfoliation that depends on both the polarity and flexibility of the monomers. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 1441–1450, 2004     

Synthesis and structural characterizations of [chromophore]+‐saponite/polyurethane nanocomposites

In this study, three chromophores—p‐nitroaniline, 4‐(4‐nitrophenylazo)aniline, and 4‐[(E)‐2‐{4‐[(E)‐2‐(4‐nitrophenyl)‐1‐diazenyl]phenyl}‐1‐diazenyl]aniline—were intercalated into layered aluminosilicate saponite and then dispersed into the polyurethanes matrix. The intercalated chromophore/saponite complexes were examined by inductively coupled plasma emission and element analysis technologies. The molecular orbital package computation simulation and X‐ray diffraction (XRD) analysis showed that possible configurations of chromophore ions on the gallery surfaces of saponite suggest that the chromophore molecules lie parallel to the basal planes of silicate as an inclined paraffin structure or as pseudo‐multilayers. The XRD and transmission electron microscopy analysis indicated that the delamination of organoclay in the polyurethanes matrix exhibited nanolayers, exfoliated structure, or both. In particular, even at high doping levels up to 15 wt % of organoclay, the [chromophore]⁺‐saponite/polyurethanes film did not display a macroscopic aggregation of layered silicates and showed high transparency. The thermal stability of chromophore was significantly enhanced as intercalated into the layered aluminosilicate saponite, and the glass‐transition temperature of [chromophore]⁺‐saponite/polyurethanes nanocomposites proportionally increased with increased clay content. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 1690–1703, 2002     

Synthesis and characterization of novel fluorinated polyurethane elastomers based on 2,2‐bis[4‐(4‐amino‐2‐trifluoromehyloxyphenyl) phenyl]propane

2,2‐Bis[4‐(4‐amino‐2‐trifluoromehyloxyphenyl) phenyl]propane (BAFPP) was synthesized based on 2‐chlorobenzotrifluoride and bisphenol A and characterized by Fourier transform infrared spectroscopy and nuclear magnetic resonance. BAFPP was used as a chain extender to prepare a series of fluorine‐containing polyurethane elastomers (FPUEs) with different fluorine contents by changing the soft segments and isocyanate index (R). The FPUEs were investigated by water absorption, contact angle, X‐ray photoelectron spectroscopy, thermogravimetric analysis, and microscale combustion calorimetry. The results show that the FPUEs prepared from BAFPP were elastomers that have low surface tension, low water absorption, and good thermal stability. Furthermore, FPUEs also exhibit good flame resistance, and the peak heat release rate of FPUE based on BAFPP (282.9 W/g) is much lower than that of polyurethane elastomer without the F element (537.2 W/g). Copyright © 2011 John Wiley & Sons, Ltd.     

Measuring true electromechanical strain of electroactive thermoplastic elastomer gels using synchrotron SAXS

The true electric actuation thickness strain of poly (styrene‐b‐ethylbutylene‐b‐styrene) (SEBS) gel was measured using an in situ synchrotron SAXS. The thermoplastic elastomer SEBS gel was microphase‐separated to form a disordered styrene micelle nanostructure in an oil‐swollen ethylbutylene matrix. The SEBS gel showed reversible cyclic load–unload compression behavior without permanent residual strain. The electromechanical strain of the SEBS gel with carbon paste electrodes could be evaluated by means of a nanostructure dimensional change traced by using the in situ synchrotron SAXS during actuation. The strain measured with SAXS was compared with the strain measured using conventional laser displacement sensor systems. The optical laser sensor method was likely to overestimate the thickness strain due to the bending movement of the dielectric elastomer. To our knowledge, the thickness strain value measured by the synchrotron SAXS is the closest to the true strain ever measured in the field of dielectric elastomer studies, because the nanostructure dimensional change depends on the thickness dimension change, not on the translational movement like the bending motion. © 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2010     

Enhanced dielectric performance of a block copolymer‐polythiophene nanocomposite

Dielectric elastomer actuators (DEAs) transform electrical energy into mechanical work. However, despite displaying exceptional features, the low permittivity of elastomers restricts their application. Hence, to overcome this limitation, DEAs are fabricated by dispersing poly(3‐methylthiophene acetate) (P3TMA), a polarizable conducting polymer, into poly[styrene‐b‐(ethylene‐co‐butylene)‐b‐styrene] (SEBS), a thermoplastic elastomer with excellent mechanical properties. Although high‐quality SEBS:P3TMA films are obtained for all compositions (between 0.5 and 20 wt % P3TMA), their thickness and surface roughness increase with the nano‐sized filler content. Moreover, the conducting particles are well integrated into the SEBS network with no evidence of aggregation or significant change in the mechanical properties of the composites. P3TMA, which forms encapsulated conductive domains within the polymeric matrix, improves the dielectric behavior of SEBS:P3TMA by increasing their dielectric constant with low dielectric losses and no current leakage. Thus, indicating the potential future application of these nanocomposites as elastomer actuators or high energy density capacitors. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2016 , 54, 1896–1905     

Microstructure and properties of styrene‐butadiene rubber based nanocomposites prepared from an aminosilane modified synthetic lamellar nanofiller

In this work, a novel nanocomposite series based on styrene‐butadiene rubber (SBR latex) and alpha‐zirconium phosphate(α‐ZrP) lamellar nanofillers is successfully prepared. The α‐ZrP lamellar filler is modified at the cation exchange capacity by γ‐aminopropyltrimethoxysilane and the filler surface modification is first discussed. A significant improvement of the mechanical properties is obtained by using the surface modified nanofillers. However, no modification of the gas barrier properties is observed. The impact of addition of bis(triethoxysilylpropyl)tetrasulfide (TESPT) as coupling agent in the system is discussed on the nanofiller dispersion state and on the filler–matrix interfacial bonding. Simultaneous use of modified nanofillers and TESPT coupling agent is found out with extraordinary reinforcing effects on both mechanical and gas barrier properties and the key factors at the origin of the improvement of these properties are identified. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2013 , 51, 1051–1059     

Preparation of waterborne polyurethane nanocomposites: Polymerization from functionalized hydroxyapatite

We report the preparation and characterization of waterborne polyurethane (WBPU)/hydroxyapatite (HAp) nanocomposites through in situ polymerization from functionalized HAp. The HAp nanoparticles (HAp NPs) were urethanated with 3-isocyanatemethyl-3,5,5-trimethyl-cyclohexylisocyanate (isophorone diisocyanate) to obtain grafted HAp NPs containing isocyanate groups (HAp-g-NCO) as crosslinkers and then the HAp-g-NCO is further polymerized with WBPU monomers to form the WBPU/HAp nanocomposites. The HAp NPs were homogeneously dispersed in the polyurethane matrix at low loading levels (?2.0 wt%), thus the mechanical strength and the elongation at break of the WBPU/HAp nanocomposites were significantly improved. Thermal stability and water resistance of the WBPU/HAp nanocomposites are also enhanced. These results suggest that the WBPU/HAp nanocomposites prepared by in situ polymerization hold the potential as new materials with improved mechanical properties, thermal stability and water resistance.     

Synthesis of aniline‐terminated polyethers and resulting polyurethane/polyurea elastomers

Functionalization of polyols with aromatic amines offers a potential route to modify properties of polyurethanes, polyamides, and epoxies. Additionally, aniline termination of polyether backbones provides the opportunity to speed up reactions with isocyanates relative to hydroxyl functionalization and slow down epoxy reactions compared to reactions with primary and secondary amines. In this article, the synthesis, characterization, and physical properties of aniline‐terminated polyols with varying molecular weight, monomer type, and functionality is described. Numerous analytical techniques are employed to track the chemical modification kinetics and the resulting aniline functionalized polyol properties. In addition, synthesis and properties of poly(urethane‐urea) elastomers from several of the modified polyols are presented. The effect of hard segment composition and process temperature on tensile properties, dynamic mechanical properties, phase morphology, and chemical resistance is explored. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2018 , 56, 1730–1742