Influence of graphene reinforcement in conductive polymer: Synthesis and characterization

Lightweight conductive polymers are considered for lightning strike mitigation in composites by synthesizing intrinsically conductive polymers (ICPs) and by the inclusion of conductive fillers in insulating matrices. Conductive films based on polyaniline (PANI) and graphene have been developed to improve through‐thickness conductivity of polymer composites. The result shows that the conductivity of PANI enhanced by blending polyvinylpyrrolidone (PVP) and PANI in 3:1 ratio. Conductive composite thin films are prepared by dispersing graphene in PANI. The conductivity of composite films was found to increase by 40× at 20 wt% of graphene inclusion compared with PVP and PANI blend. Fourier‐transform‐infrared (FTIR) spectra confirmed in situ polymerization of the polymer blend. The inclusion of graphene also exhibits an increase in Tg by 21°C. Graphene additions also showed an increase in thermal stability by approximately 148°C in the composite films. The mechanical result obtained from DMA shows that inclusion of graphene increases the tensile strength by 48% at 20 wt% of graphene reinforcement. A thin, highly conductive surface that is compatible with a composite resin system can enhance the surface conductivity of composites, improving its lightning strike mitigation capabilities.     

New polyaniline/chitosan composite systems: Synthesis,structure, and functional properties

Electroconductive and mechanically strength composite systems based on polyaniline and chitosan on the polyethylene porous substrate were obtained. A method to synthesize the conductive form of polyaniline in the solution of chitosan was developed. Molecular characteristics of chitosan in the solutions of acetic and hydrochloric acids and in their mixtures have been investigated. Optimal composition of solvent for the synthesis of polyaniline in a chitosan solution was determined. Electrical conductivity and mechanical characteristics of polyaniline/chitosan composite systems on porous polyethylene film were measured.     

Multifunctional Thermally Conductive Composite Films Based on Fungal Tree-like Heterostructured Silver Nanowires@Boron Nitride Nanosheets and Aramid Nanofibers

Thermal conduction for electronic equipment has grown in importance in light of the burgeoning of 5G communication. It is imperatively desired to design highly thermally conductive fillers and polymer composite films with prominent Joule heating characteristics and extensive mechanical properties. In this work, “solvothermal & in situ growth” method is carried out to prepare “Fungal tree”-like hetero-structured silver nanowires@boron nitride nanosheet (AgNWs@BNNS) thermally conductive fillers. The thermally conductive AgNWs@BNNS/ANF composite films are obtained by the method of “suction filtration self-assembly and hot-pressing”. When the mass fraction of AgNWs@BNNS is 50 wt%, AgNWs@BNNS/ANF composite film presents the optimal thermal conductivity coefficient of 9.44 W/(m ⋅ K) and excellent tensile strength of 136.6 MPa, good temperature-voltage response characteristics, superior electrical stability and reliability, which promise a wide application potential in 5G electronic devices.     

A biocompatible nanocomposite based on allyl chitosan and vinyltriethoxysilane for tissue engineering

The synthesis, structure, and electrophysical properties of a polymer-inorganic biocompatible composite based on unsaturated chitosan ether, namely, allyl chitosan, and vinyltriethoxysilane are studied. During composite synthesis, allyl chitosan forms an individual nanophase with vinyltriethoxysilane and its condensation products in the polymer matrix of allyl chitosan. The size of nanoparticles embedded in a polymer matrix increases from 50 to 1000 nm as the fraction of the added vinyltriethoxysilane grows. Under exposure to UV radiation, both homopolycondensation and heteropolycondensation occur in the composite films via crosslinking according to the radical mechanism and the composite becomes insoluble in water. It has been shown that the resulting composites feature ionic conductivity under application of both direct current and high-frequency electric fields to the sample. Conductivity is provided by a proton–electron ensemble that concentrates at the nanoparticle/polymer matrix interface.     

Metallized nanotube polymer composites via supercritical fluid impregnation

Although many metal decorated nanotubes and nanowires appear in the literature, well‐dispersed metal decorated nanotube polymer composites have rarely been reported because of the excessive density mismatch between the decorated nanotubes and polymer matrix. Here, we report a novel method to prepare well‐dispersed, highly functional, metallized nanotube polymer composites (MNPCs) that possess remarkably improved electrical conductivity and mechanical toughness. The MNPCs are prepared by supercritical fluid impregnation of an organometal compound into a premade well‐dispersed single wall carbon nanotube‐polymer composite film. The infused precursor preferentially migrates towards the nanotubes to undergo spontaneous reduction and form nanometer‐scale metal particles leading to an increase in the conductivity of the MNPC films. The environmentally friendly supercritical fluid impregnation process significantly improved the toughness of the composite films, regardless of the presence of metal. Additional functionality can be imparted into the resulting MNPC by infusing other precursors such as magnetic and catalytic metal compounds. © 2011 Wiley Periodicals, Inc.* J Polym Sci Part B: Polym Phys, 2012     

Columnar nanostructured polymer films containing ionic liquids in supramolecular one-dimensional nanochannels

Ionic liquids have attracted a considerable attention as the next generation electrolytes for energy devices. We have developed new free-standing and nanostructured polymer films in which ionic liquids are confined into one-dimensionally ordered nanochannels. These polymer films have been obtained by photopolymerization of hydrogen-bonded supramolecular columnar liquid-crystalline self-assemblies of an imidazolium-based ionic liquid and a wedge-shaped diol compound containing polymerizable groups. The macroscopically parallel alignment of the columnar structures on a glass substrate has been achieved by the application of mechanical shearing, and subsequently fixed into polymer films by UV irradiation. This ionic liquid-containing polymer film exhibits higher ionic conductivity than that of the previously reported one-dimensional polymer film obtained by in situ photopolymerization of a covalent-type columnar liquid-crystalline imidazolium salt. The noncovalent supramolecular approach to one-dimensionally ion-conductive polymer films has led to improvement on conductive properties. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 366–371     

Optical band gap and conductivity measurements of polypyrrole-chitosan composite thin films

Electrical conductivity and optical properties of polypyrrole-chitosan（PPy-CHI） conducting polymer composites have been investigated to determine the optical transition characteristics and energy band gap of composite films.The two electrode method and I-V characteristic technique were used to measure the conductivity of the PPy-CHI thin films,and the optical band gap was obtained from their ultraviolet absorption edges.Depending upon experimental parameter,the optical band gap（E_g） was found within 1.30-2.32 eV as estimated from optical absorption data.The band gap of the composite films decreased as the CHI content increased.The room temperature electrical conductivity of PPy-CHI thin films was found in the range of 5.84×10^-7-15.25×10^-7 S·cm^-1 depending on the chitosan content.The thermogravimetry analysis（TGA） showed that the CHI can improve the thermal stability of PPy-CHI composite films.     

Electric-Field-Induced Alignment of Functionalized Carbon Nanotubes Inside Thermally Conductive Liquid Crystalline Polyimide Composite Films

The positive liquid crystals, 4′-heptyl-4-biphenylcarbonitrile (7CB), are used to functionalize carbon nanotubes (LC-CNT), which can be aligned in the liquid crystalline polyimide (LC-PI) matrix under an alternating electric field to fabricate the thermally conductive LC-CNT/LC-PI composite films. The efficient establishment of thermal conduction pathways in thermally conductive LC-CNT/LC-PI composite films with a low amount of LC-CNT is achieved through the oriented alignment of LC-CNT within the LC-PI matrix. When the mass fraction of LC-CNT is 15 wt %, the in-plane thermal conductivity coefficient (λ_∥) and the through-plane thermal conductivity coefficient (λ_⊥) of the LC-CNT/LC-PI composite films reach 4.02 W/(m ⋅ K) and 0.55 W/(m⋅K), which are 90.5 % and 71.9 % higher than those of the intrinsically thermally conductive LC-PI films respectively, also 28.8 % and 5.8 % higher than those of the CNT/LC-PI composite films respectively. Meanwhile, the thermally conductive LC-CNT/LC-PI composite films also possess excellent mechanical and heat resistance properties. The Young's modulus and the heat resistance index are 2.3 GPa and 297.7 °C, respectively, which are higher than the intrinsically thermally conductive LC-PI films and the thermally conductive CNT/LC-PI composite films under the same amount of CNT.     

Investigation of Nanocomposite Polymer Electrolytes for Lithium Ion Batteries

Composite polymer electrolytes based on polyvinyl alcohol: polyvinylidine fluoride: lithium triflate doped with different concentration of nanosilica have been prepared by the solution casting technique. The prepared films are transparent and mechanically stable. Interaction of SiO₂ nanoparticles with the host polymer in the composite polymer electrolyte has been confirmed using X-ray diffraction, Fourier transform infrared spectroscopy, and photoluminescence spectra. Dispersion of nanofiller in the polymer matrix help to increase the free volume of the system and thus increases amorphous nature. The optimal composition of composite polymer electrolytes was found possessing high conductivity, thermal, mechanical and electrochemical stability, which will be well suited for lithium ion battery applications.     

Electrically conductive composite prepared by template polymerization of pyrrole into a complexed polymer

Electrically conducting polymer composite films have been synthesized by the exposure of poly(4-vinylpyridine) complexed with cupric ions to pyrrole and water vapor. To immobilize a stoichiometric amount of the oxidant inside the polymer matrix, the ratio of poly(4-vinylpyridine)/cupric ion = 1.8 was chosen. Polypyrrole was formed in this tailored structure by a template polymerization process. Opaque polymer composite films with electrical conductivity up to 60 (Ω cm)^?1 have been obtained by this method, However, slightly colored transparent composite thin films with a conductivity as high as 50 (Ω cm)^?1 were also produced. The electrically conducting polymer composite films and the metal-polymer complex have been characterized by XPS and IR spectroscopy, elemental analysis, EDX, and scanning electron microscopy. The polymerization process was also followed by use of a quartz crystal microbalance. © 1994 John Wiley & Sons, Inc.     

导电高分子在神经界面电极中的应用

神经界面电极作为人体和外部器件间信息融合的媒介, 为人们进一步探究神经系统高级功能的机制提供了有效工具. 传统的神经电极多以金属和半导体材料为主, 这两类材料因具有惰性材料的特性及优越的 导电性能而成为早期神经电极的主要制备材料, 但由于其刚性过大和光滑表面导致的机械失配及与生物组织间过高的电化学阻抗限制了神经电极的进一步发展. 导电高分子作为一种有机导电材料, 同时具备柔软性 (杨氏模量约在0.01~10 GPa)和导电性(高掺杂度的导电高分子的电导率在金属范围, 10⁰~10⁵ S/cm)的特征, 是制备神经电极的有效材料. 近年来, 人们利用导电高分子材料对传统电极材料进行改性甚至替代, 以提高电极比表面积、 减小界面阻抗, 并提高电极检测的灵敏性; 同时减小电极与组织间的应变失配, 减少炎症反应, 并进一步在导电高分子中引入功能性生物大分子, 减少生物组织对电极的排异反应, 增加电极在体内长期植入的稳定性. 本文讨论和总结了导电高分子材料在神经电极中的应用, 分别对导电高分子作为涂层修饰神经电极、 全导电高分子材料神经电极及导电高分子复合材料神经电极等展开讨论, 分析了导电高分子在神经界面电极中的应用前景及存在的问题, 以期对神经界面电极在脑科学和生物电子医疗等前沿领域的进一步发展提供参考.     

Preparation and characterization of electrostrictive polyurethane films with conductive polymer electrodes

All-polymer electrostrictive soft films were developed for the first time by depositing conductive polymer (polypyrrole) directly on both sides of solution-cast electrostrictive polyurethane elastomer films. The final composite films are flexible with strong adhesion between the polyurethane film and the conductive polymer electrode. The conductivity (sheet resistivity ∼1000 Ω/□), of the polymer electrode is appropriate for its intended use. The compatible interface between the polypyrrole electrode polymer and the electrostrictive polyurethane significantly improves the acoustic and optical transparency of these composite films, compared with using a metal electrode film. The all-polymer films also exhibit comparable dielectric properties to gold-electroded polyurethane films in the temperature range from −40^°C to +80^°C. The temperature range covers the soft segment glass transition temperature of the polyurethane elastomers, which is about −20^°C. The films also show large electric field induced strain responses which are dependent on film thickness and measurement frequency. The electrostrictive characteristics in the all-polymer films show similarities to those of the films with gold electrodes under identical measurement conditions. © 1998 John Wiley & Sons, Ltd.     

The influence of UV irradiation on the properties of chitosan films containing keratin

The mechanical, thermal and surface properties of chitosan and chitosan containing keratin hydrolysates have been studied and the influence of UV irradiation on these properties has been compared. The surface properties of chitosan films containing 5%, 15% and 30% of keratin hydrolysate before and after UV irradiation (λ = 254 nm) were investigated by means of contact angle measurements allowing the calculation of surface free energy. The chemical and structural changes during UV irradiation were studied by UV-vis and FTIR-ATR spectroscopy.The changes in mechanical properties such as breaking strength, percentage elongation and Young’s modulus have been investigated. The results have shown that the mechanical properties of the chitosan/keratin films were greatly affected by UV irradiation, but the level of the changes of these properties was smaller in the blend than in pure chitosan and strongly dependent on the time of irradiation and composition of the samples. The contact angle and the surface free energy were altered by UV irradiation, which indicates photooxidation and an increase of polarity of specimens. The range of these changes point to greater susceptibility of chitosan to photooxidation in the presence of keratin.     

An experimental investigation of the effect of strain on the electrical conductivity of a shape memory polymer

A thermally triggered shape memory polymer (SMP) was prepared by blending electrically conductive carbon black (CB) into the resin prior to curing. The CB filled composite can then be activated through resistive heating. With the aim of using such SMPs in reconfigurable structures and/or actuators, the effect of strain on the conductive nature of the SMP composite was investigated. The study has specifically focused on changes to conductivity in, i) the transverse direction during tensile elongation to assess the impact of the Poisson effect, and ii) in samples deformed in compression. The dynamic response characteristics of the electrically activated SMP were also tested to assess the feasibility of using the composite in tunable vibration damping applications. Findings have shown that the pattern of changes in the transverse conductivity, which is marked by an increase-decrease-increase sequence, resembles that seen in the axial direction. SEM imaging of the samples was performed along the axial and transverse axes of deformation and shows no anisotropy in the CB filler distribution. To demonstrate potential uses of a conductive SMP in the sub-T_g temperature range, a discussion of a vibration damping application has been included.     

Swift heavy ion induced modification in dielectric and microhardness properties of polymer composites

Polymer composites with different concentrations of organometallics (ferric oxalate) dispersed PMMA were prepared. PMMA was synthesized by solution polymerization technique. These films were irradiated with 120 MeV Ni¹⁰⁺ ions in the fluence range 10¹¹-5 × 10¹² ions/cm². The radiation induced modifications in dielectric properties, microhardness, structural changes and surface morphology of polymer composite films have been investigated at different concentrations of filler and ion-fluences. It was observed that electrical conductivity and hardness of the films increase with the concentration of the filler and also with the fluence. The dielectric constant (?) obeys the Universal law given by ?αfⁿ⁻¹. The dielectric constant/loss is observed to change significantly due to irradiation. This suggests that ion beam irradiation promotes the metal to polymer bonding and convert polymeric structure into hydrogen depleted carbon network. This makes the composites more conductive and harder. Surface morphology of the films has been studied using atomic force microscopy (AFM) and scanning electron microscopy (SEM). The average surface roughness is observed to increase after irradiation as revealed by AFM studies. The SEM images show the blisters type of phenomenon on the surface due to ion beam irradiation.     

The effect of magnetic field on conductive films

Conductive paints consisting of nickel powder (conductive material), solvent, and binder polymer were treated in a magnetic field. The efficiency of magnetic treatments on conductivity of coating films was evaluated. The effect of the following factors on conductivity of composite films by magnetic treatment was studied: metal powder concentration, magnetic flow density, time difference between film preparation and magnetic treatment, drying time of paint films, and effect of distance between terminals. Results showed that the volume resistivity of paint films treated magnetically was lower than that for untreated films at each nickel content. Magnetic treatment provided high conductivity even at low magnetic flow density, and conductivity increased with magnetic flow density.     

Conductive macroporous composite chitosan-carbon nanotube scaffolds

Multiwalled carbon nanotubes (MWCNTs) were used as doping material for three-dimensional chitosan scaffolds to develop a highly conductive, porous, and biocompatible composite material. The porous and interconnected structures were formed by the process of thermally induced phase separation followed by freeze-drying applied to an aqueous solution of 1 wt % chitosan acetic acid. The porosity was characterized to be 97% by both mercury intrusion porosimetry measurements and SEM image analysis. When MWCNTs were used as a filler to introduce conductive pathways throughout the chitosan skeleton, the solubilizing hydrophobic and hydrophilic properties of chitosan established stable polymer/MWCNT solutions that yielded a homogeneous distribution of nanotubes throughout the final composite matrix. A percolation theory threshold of approximately 2.5 wt % MWCNTs was determined by measurement of the conductivity as a function of chitosan/MWCNT ratios. The powder resistivity of completely compressed scaffolds also was measured and was found to be similar for all MWCNT concentrations (0.7-0.15 Omega cm powder resistivity for MWCNTs of 0.8-5 wt %) and almost five times lower than the 20 k Omega cm value found for pure chitosan scaffolds.     

Ultrathin anisotropic films assembled from individual single-walled carbon nanotubes and amine polymers

Oxidized individual single-walled carbon nanotubes and amine polymers have been assembled into 11-32-nm-thick well-ordered conductive films. The films show highly anisotropic electrical conductivity, which is dominated by the nanotubes in the horizontal plane and by polymer-mediated tunneling in the vertical direction. The ratio of the "along" to "across" conductivity is approximately 10(3). The subnanometer thick polymer layers interleaved with monolayers of nanotubes show conductivity several orders of magnitude higher than films of pristine polymers.     

Graft polymerization of acrylamide on chitosan: Copolymer structure and properties

Graft copolymers have been prepared through the free-radical polymerization of acrylamide in water-acetic acid solutions of chitosan in the presence of ammonium persulfate as an initiator. The effect of temperature, pH of a medium, and concentrations of initiator, chitosan, and acrylamide on the grafting kinetics and efficiency has been established. The local concentration of acrylamide in the reaction zone increases due to intermolecular hydrogen bonding between polysaccharide and monomer molecules. Copolymer films are characterized by better mechanical properties compared to those of polysaccharide. Hydrogels with good viscoelastic properties have been obtained when grafting was performed in the presence of N,N-methylenebisacrylamide as a crosslinking agent.     

多功能性聚吡咯复合膜

聚吡咯具有较高的电导率与良好的环境稳定性,被视为继聚苯胺之后最有工业化应用前景的导电高分子材料之一。聚吡咯与常规聚合物基体如聚乙烯醇、聚氯乙烯等形成的复合膜不仅可以综合聚吡咯奇异的多功能性与常规聚合物的易成膜性和低成本性于一体,而且可望发挥两者的协同效应,从而大大拓宽其应用领域。该研究已经成为导电聚合物研究领域中的又一新热点。作者系统论述了制备这类功能复合膜的两种典型制备方法,并在分析各自特点的基础上提出了改进与发展方向,指出聚吡咯复合膜具有广泛可调的电导率、快速的电学响应性以及稳定的电致变色性等多种功能,在透明导电膜、化学传感器、生物分离膜、电致变色膜领域具有诱人的应用前景。