Co-reporter:Jin Chen, Xingyi Huang, Bin Sun, Yuxin Wang, Yingke Zhu, and Pingkai Jiang
ACS Applied Materials & Interfaces September 13, 2017 Volume 9(Issue 36) pp:30909-30909
Publication Date(Web):August 21, 2017
DOI:10.1021/acsami.7b08061
The continuous evolution toward semiconductor technology in the “more-than-Moore” era and rapidly increasing power density of modern electronic devices call for advanced thermal interface materials (TIMs). Here, we report a novel strategy to construct flexible polymer nanocomposite TIMs for advanced thermal management applications. First, aligned polyvinyl alcohol (PVA) supported and interconnected 2D boron nitride nanosheets (BNNSs) composite fiber membranes were fabricated by electrospinning. Then, the nanocomposite TIMs were constructed by rolling the PVA/BNNS composite fiber membranes to form cylinders and subsequently vacuum-assisted impregnation of polydimethylsiloxane (PDMS) into the porous cylinders. The nanocomposite TIMs not only exhibit a superhigh through-plane thermal conductivity enhancement of about 10 times at a low BNNS loading of 15.6 vol % in comparison with the pristine PDMS but also show excellent electrical insulating property (i.e., high volume electrical resistivity). The outstanding thermal management capability of the nanocomposite TIMs was practically confirmed by capturing the surface temperature variations of a working LED chip integrated with the nanocomposite TIMs.Keywords: boron nitride nanosheets; electrospun; nanocomposites; PDMS; thermal conductivity;
Co-reporter:Yingke Zhu, Pingkai Jiang, Zhicheng Zhang, Xingyi Huang
Chinese Chemical Letters 2017 Volume 28, Issue 11(Volume 28, Issue 11) pp:
Publication Date(Web):1 November 2017
DOI:10.1016/j.cclet.2017.08.053
Polymeric dielectrics have wide range of applications in the field of electrical energy storage because of their light weight and easy processing. However, the state-of-the-art polymer dielectrics, such as biaxially orientated polypropylene, could not meet the demand of minimization of electronic devices because of its low energy density. Recently, poly(vinylidene fluoride) (PVDF) based ferroelectric polymers have attracted considerable interests for energy storage applications because of their high permittivity and high breakdown strength. Unfortunately, the high dielectric loss and/or high remnant polarization of PVDF-based polymers seriously limits their practical applications for electrical energy storage. Since the discovery of relaxor ferroelectric behavior was firstly reported in irradiated poly(vinylidene fluoride-trifluoroethylene) (P(VDF-TrFE)) copolymer, many strategies have been developed to enhanced the electrical energy storage capability, including copolymerization, grafting, blending and fabricating of multilayer. How these methods affect the polymorphs, crystallinity, crystal size of PVDF-based polymers and the connection between these microstructures and their corresponding energy storage properties are discussed in detail.Download high-res image (124KB)Download full-size imageSince the discovery of relaxor ferroelectric behavior was firstly reported in irradiated poly(vinylidene fluoride-trifluoroethylene) (P(VDF-TrFE)) copolymer, many strategies have been developed to enhance the electrical energy storage capability, including copolymerization, grafting, blending and fabricating of multilayer. This review article mainly summarizes the recent progresses on these strategies and aims to motivate the development of novel PVDF-based polymers for electrical energy storage and dielectric applications.
Co-reporter:Yuxin Wang;Tao Li;Zhongwu Wang;Liqiang Li;Xiaojun Guo;Pingkai Jiang
Journal of Materials Chemistry A 2017 vol. 5(Issue 39) pp:20737-20746
Publication Date(Web):2017/10/10
DOI:10.1039/C7TA06005J
High-dielectric-constant (high-k) polymers are highly desirable for energy storage and dielectric applications in power systems and microelectronic devices because of their easy processing and flexibility. However, the enhancement of k is usually at the cost of other undesirable properties such as increase of dielectric loss and leakage currents and decrease of breakdown strength. Herein, using reversible-addition fragmentation chain transfer (RAFT) polymerization, we report a series of novel low-temperature crosslinkable high-k copolymers, poly(2-(methylsulfonyl)ethyl methacrylate-co-glycidyl methacrylate) (poly(MSEMA-co-GMA)), which exhibit k values about 9–12. The crosslinking significantly enhances the breakdown strength (Eb ≈ 500 MV m−1), suppresses the leakage currents and improves the solvent resistance. The excellent dielectric performance makes the copolymers have both high energy storage capability and high energy efficiency. The discharged energy density reached 12.5 J cm−3 at 500 MV m−1. Noticeably, an efficiency higher than 85% was maintained even at a high field of 400 MV m−1, which is much higher than those of poly(vinylidene fluoride) (PVDF) based ferroelectric polymers with comparable k. Furthermore, the poly(MSEMA-co-GMA) copolymers were successfully applied as dielectric layers for organic field-effect transistors (OFETs) to realize low-voltage operation.
Co-reporter:Guanyao Wang;Yanhui Huang;Yuxin Wang;Pingkai Jiang
Physical Chemistry Chemical Physics 2017 vol. 19(Issue 31) pp:21058-21068
Publication Date(Web):2017/08/09
DOI:10.1039/C7CP04096B
Dielectric polymer nanocomposites have received keen interest due to their potential application in energy storage. Nevertheless, the large contrast in dielectric constant between the polymer and nanofillers usually results in a significant decrease of breakdown strength of the nanocomposites, which is unfavorable for enhancing energy storage capability. Herein, BaTiO3 nanowires (NWs) encapsulated by TiO2 shells of variable thickness were utilized to fabricate dielectric polymer nanocomposites. Compared with nanocomposites with bare BaTiO3 NWs, significantly enhanced energy storage capability was achieved for nanocomposites with TiO2 encapsulated BaTiO3 NWs. For instance, an ultrahigh energy density of 9.53 J cm−3 at 440 MV m−1 could be obtained for nanocomposites comprising core–shell structured nanowires, much higher than that of nanocomposites with 5 wt% raw ones (5.60 J cm−3 at 360 MV m−1). The discharged energy density of the proposed nanocomposites with 5 wt% mTiO2@BaTiO3-1 NWs at 440 MV m−1 seems to rival or exceed those of some previously reported nanocomposites (mostly comprising core–shell structured nanofillers). More notably, this study revealed that the energy storage capability of the nanocomposites can be tailored by the TiO2 shell thickness. Finite element simulations were employed to analyze the electric field distribution in the nanocomposites. The enhanced energy storage capability should be mainly attributed to the smoother gradient of dielectric constant between the nanofillers and polymer matrix, which alleviated the electric field concentration and leakage current in the polymer matrix. The methods and results herein offer a feasible approach to construct high-energy-density polymer nanocomposites with core–shell structured nanowires.
Co-reporter:Guanyao WangXingyi Huang, Pingkai Jiang
ACS Applied Materials & Interfaces 2017 Volume 9(Issue 8) pp:
Publication Date(Web):February 2, 2017
DOI:10.1021/acsami.6b14454
Rapid evolution of energy storage devices expedites the development of high-energy-density materials with excellent flexibility and easy processing. The search for such materials has triggered the development of high-dielectric-constant (high-k) polymer nanocomposites. However, the enhancement of k usually suffers from sharp reduction of breakdown strength, which is detrimental to substantial increase of energy storage capability. Herein, the combination of bio-inspired fluoro-polydopamine functionalized BaTiO3 nanowires (NWs) and a fluoropolymer matrix offers a new thought to prepare polymer nanocomposites. The elaborate functionalization of BaTiO3 NWs with fluoro-polydopamine has guaranteed both the increase of k and the maintenance of breakdown strength, resulting in significantly enhanced energy storage capability. The nanocomposite with 5 vol % functionalized BaTiO3 NWs discharges an ultrahigh energy density of 12.87 J cm–3 at a relatively low electric field of 480 MV m–1, more than three and a half times that of biaxial-oriented polypropylene (BOPP, 3.56 J cm–3 at 600 MV m–1). This superior energy storage capability seems to rival or exceed some reported advanced nanoceramics-based materials at 500 MV m–1. This new strategy permits insights into the construction of polymer nanocomposites with high energy storage capability.Keywords: bio-inspired; dielectric constant; energy storage; nanocomposite; nanowire;
Co-reporter:Guanyao Wang;Pingkai Jiang
Journal of Materials Chemistry C 2017 vol. 5(Issue 12) pp:3112-3120
Publication Date(Web):2017/03/23
DOI:10.1039/C7TC00387K
The attractiveness of dielectric polymer nanocomposites stems from their potential applications in electrical insulation and energy storage devices. However, the inevitable electrical mismatch and incompatibility between nanofillers and polymer matrices usually give rise to undesirable dielectric properties and weak energy storage capability. Despite the progress achieved to date, there is still plenty of room for further improvement in terms of energy storage of polymer nanocomposites. Herein, anatase TiO2 nanowires (NWs) were utilized as dopants into a ferroelectric polymer since their moderate dielectric constant is beneficial for alleviating the electric field intensification in the polymer–filler system. Besides, inspired by the strong adhesion property of mussels, a brush-like long-chain tailed dopamine derivative (h-DOPA) is employed to improve the inclusion of TiO2 NWs into the polymer matrix, leading to remarkably reduced dielectric loss and leakage current densities in comparison with the nanocomposites with raw nanowires. Benefiting from the excellent compatibility between these two components, the breakdown strength of these proposed nanocomposites decreases gently from ca. 520 MV m−1 to ca. 350 MV m−1, accompanied by nanofiller loadings from 2.5 vol% to 15 vol%. Moreover, the nanocomposite with 2.5 vol% h-DOPA@TiO2 NWs discharges an ultrahigh energy storage density of 11.13 J cm−3 at 520 MV m−1, while that of the pure polymer can reach only up to 8.75 J cm−3 at 500 MV m−1. A strikingly high energy density of 8.57 J cm−3 is also achieved with the nanofiller volume fraction as high as 15% at a low electric field of 350 MV m−1, nearly double that of pure P(VDF-HFP) (4.76 J cm−3 at 360 MV m−1). The results and methods presented here provide deep insights into a facile and versatile approach to fabricate polymer nanocomposites with high energy storage capability.
Co-reporter:Yanhui Huang, Xingyi Huang, Linda S. Schadler, Jinliang He, and Pingkai Jiang
ACS Applied Materials & Interfaces 2016 Volume 8(Issue 38) pp:25496
Publication Date(Web):September 7, 2016
DOI:10.1021/acsami.6b06650
This work reports the advances of utilizing a core@double-shell nanostructure to enhance the electrical energy storage capability and suppress the dielectric loss of polymer nanocomposites. Two types of core@double-shell barium titanate (BaTiO3) matrix-free nanocomposites were prepared using a surface initiated atom transfer radical polymerization (ATRP) method to graft a poly(2-hydroxylethyle methacrylate)-block-poly(methyl methacrylate) and sodium polyacrylate-block-poly(2-hydroxylethyle methacrylate) block copolymer from BaTiO3 nanoparticles. The inner shell polymer is chosen to have either high dielectric constant or high electrical conductivity to provide large polarization, while the encapsulating outer shell polymer is chosen to be more insulating as to maintain a large resistivity and low loss. Finite element modeling was conducted to investigate the dielectric properties of the fabricated nanocomposites and the relaxation behavior of the grafted polymer. It demonstrates that confinement of the more conductive (lossy) phase in this multishell nanostructure is the key to achieving a high dielectric constant and maintaining a low loss. This promising multishell strategy could be generalized to a variety of polymers to develop novel nanocomposites.Keywords: ATRP; BaTiO3; core@double-shell; high dielectric constant; low loss; nanocomposites
Co-reporter:Jing Bu, Xingyi Huang, Shengtao Li, Pingkai Jiang
Carbon 2016 Volume 106() pp:218-227
Publication Date(Web):September 2016
DOI:10.1016/j.carbon.2016.05.020
This work reports the advance of utilizing antioxidant functionalized graphene oxide (GO) to enhance the thermal oxidative stability and retain the excellent electrical insulating properties of low density polyethylene. GO was first functionalized by a reactive antioxidant (AO) and then the AO functionalized GO (GO-AO) was coated with dopamine to avoid the adsorption of AO on the GO surface. The obtained products (i.e., polydopamine encapsulated GO-AO, RGO-AO) were used as filler to prepare low density polyethylene (LDPE) composites. The antioxidative efficiency of RGO-AO on LDPE was evaluated by oxidative induction time (OIT) of the composite samples. It was found that the addition of RGO-AO results in significantly prolonged OIT of the LDPE composites. For example, OIT of LDPE composite with 2.0 wt % RGO-AO increases to 19 min from 0.5 min of the pure LDPE. More importantly, the excellent electrical insulating properties of LDPE were retained in the RGO-AO/LDPE composites, which exhibit slightly enhanced dielectric constant, significantly suppressed dielectric loss tangent and decreased electrical conductivity when compared with the pure LDPE.
Co-reporter:Qingchao Jia
The Journal of Physical Chemistry C 2016 Volume 120(Issue 19) pp:10206-10214
Publication Date(Web):May 2, 2016
DOI:10.1021/acs.jpcc.6b02968
This work reports the advances of utilizing molybdenum disulfide (MoS2) nanosheet superstructures to enhance dielectric property and electrical energy storage capability of flexible ferroelectric polymer composites. Hydrangea-like flowers or clusters comprising MoS2 nanosheets were synthesized by hydrothermal methods and used as filler of ferroelectric polymer composites. Both MoS2 superstructure based composites show percolation-like electrical behavior. The composites with high loading of MoS2 superstructures exhibit significantly enhanced dielectric constant, whereas those with low loading of MoS2 superstructures can withstand high electric field and exhibit significantly enhanced electric polarization, resulting in significant improvement of electrical energy storage capability. The MoS2 flowers show strong potential to enhance the dielectric constant and electrical energy storage capability of the composites.
Co-reporter:Xingyi Huang;Pingkai Jiang
Advanced Materials 2015 Volume 27( Issue 3) pp:546-554
Publication Date(Web):
DOI:10.1002/adma.201401310
High-k polymer nanocomposites have considerable potential in energy storage and dielectric applications because of their ease of processing, flexibility, and low cost. Core–shell nanoarchitecture strategies are versatile and powerful tools for the design and synthesis of advanced high-k polymer nanocomposites. Recent and in-progress state-of-the-art advancements in the application of core–shell nanoarchitecture strategies to design and prepare high-k polymer nanocomposites are summarized. Special focus is directed to emphasizing their advantages over conventional melt-mixing and solution-mixing methods: first, homogeneous nanoparticle dispersion can be easily achieved even in highly loaded nanocomposites; second, the dielectric constant of the nanocomposites can be effectively enhanced and meanwhile the high breakdown strength can be well-preserved; third, for nanocomposites filled with electrically conductive nanoparticles, dielectric loss can be effectively surpressed, and meanwhile a high dielectric constant can be achieved. In addition, fundamental insights into the roles of the interfaces on the dielectric properties of the nanocomposites can be probed. The last part of the article is concluded with current problems and future perspectives of utilizing the core–shell nanoarchitecture strategies for the development of high-k polymer nanocomposites.
Co-reporter:Guanyao Wang, Xingyi Huang, and Pingkai Jiang
ACS Applied Materials & Interfaces 2015 Volume 7(Issue 32) pp:18017
Publication Date(Web):July 30, 2015
DOI:10.1021/acsami.5b06480
High dielectric constant (k) polymer nanocomposites have shown great potential in dielectric and energy storage applications in the past few decades. The introduction of high-k nanomaterials into ferroelectric polymers has proven to be a promising strategy for the fabrication of high-k nanocomposites. One-dimensional large-aspect-ratio nanowires exhibit superiority in enhancing k values and energy density of polymer nanocomposites in comparison to their spherical counterparts. However, the impact of their intrinsic properties on the dielectric properties of polymer nanocomposites has been seldom investigated. Herein, four kinds of nanowires (Na2Ti3O7, TiO2, BaTiO3, and SrTiO3) with different inherent characteristics are elaborately selected to fabricate high-k ferroelectric polymer nanocomposites. Dopamine functionalization facilitates the excellent dispersion of these nanowires in the ferroelectric polymer matrix because of the strong polymer/nanowire interfacial adhesion. A thorough comparative study on the dielectric properties and energy storage capability of the nanowires-based nanocomposites has been presented. The results reveal that, among the four types of nanowires, BaTiO3 NWs show the best potential in improving the energy storage capability of the proposed nanocomposites, resulting from the most signficant increase of k while retaining the rather low dielectric loss and leakage current.Keywords: breakdown strength; dielectric constant; energy storage; leakage current; nanocomposite; nanowire
Co-reporter:Lijun Fang, Wei Wu, Xingyi Huang, Jinliang He, Pingkai Jiang
Composites Science and Technology 2015 Volume 107() pp:67-74
Publication Date(Web):11 February 2015
DOI:10.1016/j.compscitech.2014.12.009
Polymer composites with high thermal conductivity and high dielectric constant are highly desirable in electronic and electric industry, and particularly, for power apparatus at high voltages. In this work, a novel hydrangea-like ZnO superstructure was prepared by a template-free solvothermal method. Polyvinylidene fluoride (PVDF) composites filled with the ZnO superstructure were prepared via a solution mixing method. The microstructure, thermal conductivity, thermal stability and dielectric properties of the composites were investigated. It was found that the hydrangea-like ZnO shows marginal influence on microstructure of the PVDF matrix, but has significant enhancement effects on thermal conductivity, thermal stability and dielectric constant of the composites. Compared with the commercial ZnO nanoparticles, the hydrangea-like ZnO superstructures result in much higher enhancement of thermal conductivity and dielectric constant and slightly lower breakdown strength of the composites. This has been ascribed to the formation of percolation-like structure in the hydrangea-like ZnO composites.
Co-reporter:Ke Yang;Jinliang He;Pingkai Jiang
Advanced Materials Interfaces 2015 Volume 2( Issue 17) pp:
Publication Date(Web):
DOI:10.1002/admi.201500361
Flexible nanocomposites comprising of polymer and high-dielectric-constant (high-k) ceramic nanoparticles are becoming increasingly attractive for dielectric and energy storage applications in modern electronic and electric industry. However, a huge challenge still remains. Namely, the increase of dielectric constant usually at the cost of significant decrease of breakdown strength of the nanocomposites because of the electric field distortion and concentration induced by the high-k filler. To address this long-standing problem, by using nano-Ag decorated core–shell polydopamine (PDA) coated BaTiO3 (BT) hybrid nanoparticles, a new strategy is developed to prepare high-k polymer nanocomposites with high breakdown strength. The strawberry-like BT-PDA-Ag based ferroelectric polymer [i.e., poly(vinylideneflyoride-co-hexafluroro propylene), P(VDF-HFP)] nanocomposites exhibit greatly enhanced energy density and significantly suppressed dielectric loss as well as leakage current density in comparison with the nanocomposites with the core–shell structured BT-PDA. Coulomb-blockade effect of super-small nano-Ag is used to explain the observed performance enhancement of the nanocomposites. The simplicity and scalability of the described approach provide a promising route to polymer nanocomposites for dielectric and energy storage applications.
Co-reporter:Yanyan Fan
The Journal of Physical Chemistry C 2015 Volume 119(Issue 49) pp:27330-27339
Publication Date(Web):November 12, 2015
DOI:10.1021/acs.jpcc.5b09619
Flexible high-dielectric-constant (high-κ) nanocomposite dielectrics comprising polymer matrix and ceramic nanoparticles have important applications in the fields of electrical insulation and energy storage. However, most of the flexible high-κ nanocomposites are fabricated by using nonbiodegradable polymers as matrixes, which may not meet the increasing demands of society for environmental sustainability. In this study, using biodegradable polylactic acid (PLA) as a matrix and core–shell structured BaTiO3 (BT) nanoparticles as high-κ filler, we report the preparation and structure–property relationship of environmentally friendly flexible high-κ polymer nanocomposites. Two types of core–shell structured high-κ nanoparticles [polydopamine-encapsulated BT (BT@PDA) and PLA-encapsulated BT@PDA (BT@PDA@PLA)] as well as as-prepared BT nanoparticles were used as filler of the PLA-based high-κ nanocomposites. It was found that, compared with the as-prepared BT nanocomposites, the core–shell nanoparticle-based composites show enhanced dielectric constant, suppressed dielectric loss tangent, and enhanced breakdown strength. In addition, the BT@PDA@PLA nanocomposites have much higher dielectric constant and energy density. The nanoparticle–PLA compatibility and its influence on the dielectric and energy storage properties of the nanocomposites were also investigated. Because the polymer matrix is environmentally friendly and the preparation process of the core–shell nanoparticles is facile and nontoxic, the nanocomposites reported here may be used in the next generation of environmentally friendly high-performance energy storage devices.
Co-reporter:Shen Wang
The Journal of Physical Chemistry C 2015 Volume 119(Issue 45) pp:25307-25318
Publication Date(Web):October 15, 2015
DOI:10.1021/acs.jpcc.5b09066
Co-reporter:Liyuan Xie, Xingyi Huang, Ke Yang, Shengtao Li and Pingkai Jiang
Journal of Materials Chemistry A 2014 vol. 2(Issue 15) pp:5244-5251
Publication Date(Web):21 Jan 2014
DOI:10.1039/C3TA15156E
The introduction of high dielectric constant ceramic nanoparticles into an insulating polymer is an important approach to prepare high dielectric constant nanocomposites for electric energy storage applications. A key to obtaining desirable properties is the homogeneous dispersion of the nanoparticles in the corresponding polymer. Conventional methods used to improve the nanoparticle dispersion enhance the physical interaction between the nanoparticle and the polymer matrix via nanoparticle surface modification. In this work, the covalent bonding between the nanoparticle and the polymer matrix was utilized to simultaneously enhance the nanoparticle dispersion and nanoparticle/polymer interaction by functionalizing both the polymer and the nanoparticles. The poly(vinylidene fluoride-co-hexafluoropropylene) [PVDF-HFP] was functionalized with glycidyl methacrylate (GMA) via atom transfer radical polymerization. The barium titanate (BaTiO3) nanoparticles were modified by amino-terminated silane molecules. Then the nanocomposites were prepared by a “grafting to” method. Namely, grafting GMA functionalized PVDF-HFP to the surfaces of the BaTiO3 nanoparticles. The introduction of GMA into the PVDF-HFP not only increases the dielectric constant, but also changes the dielectric response of PVDF-HFP. More importantly, this “grafting to” approach results in core–shell structured BaTiO3@PVDF-HFP-GMA and thus a homogeneous dispersion of BaTiO3 nanoparticles in the nanocomposites. The dielectric constant, electric energy density and thermal conductivity of the nanocomposites are significantly enhanced with the increase of BaTiO3, while the dielectric loss shows a slight decrease as the nanoparticle loading increases.
Co-reporter:Ke Yang, Xingyi Huang, Lijun Fang, Jinliang He and Pingkai Jiang
Nanoscale 2014 vol. 6(Issue 24) pp:14740-14753
Publication Date(Web):03 Oct 2014
DOI:10.1039/C4NR03957B
Flexible nanodielectric materials with high dielectric constant and low dielectric loss have huge potential applications in the modern electronic and electric industry. Graphene sheets (GS) and reduced-graphene oxide (RGO) are promising fillers for preparing flexible polymer-based nanodielectric materials because of their unique two-dimensional structure and excellent electrical and mechanical properties. However, the easy aggregation of GS/RGO significantly limits the potential of graphene in enhancing the dielectric constant of polymer composites. In addition, the poor filler/matrix nanoscale interfacial adhesion also causes difficulties in suppressing the dielectric loss of the composites. In this work, using a facile and environmentally friendly approach, polydopamine coated RGO (PDA-RGO) and fluoro-polymer functionalized RGO (PF-PDA-RGO) were prepared. Compared with the RGO prepared by the conventional methods [i.e. hydrazine reduced-graphene oxide (H-RGO)] and PDA-RGO, the resulting PF-PDA-RGO nanosheets exhibit excellent dispersion in the ferroelectric polymer matrix [i.e. poly(vinylidene fluoride-co-hexafluoro propylene), P(VDF-HFP)] and strong interfacial adhesion with the matrix, leading to a low percolation threshold (fc = 1.06 vol%) and excellent flexibility for the corresponding nanocomposites. Among the three nanocomposites, the P(VDF-HFP)/PF-PDA-RGO nanocomposites exhibited the optimum performance (i.e. simultaneously having high dielectric constant and low dielectric loss). For instance, at 1000 Hz, the P(VDF-HFP) nanocomposite sample with 1.0 vol% PF-PDA-RGO has a dielectric constant of 107.9 and a dielectric loss of 0.070, showing good potential for dielectric applications. Our strategy provides a new pathway to prepare high performance flexible nanodielectric materials.
Co-reporter:Ke Yang, Xingyi Huang, Ming Zhu, Liyuan Xie, Toshikatsu Tanaka, and Pingkai Jiang
ACS Applied Materials & Interfaces 2014 Volume 6(Issue 3) pp:1812
Publication Date(Web):January 7, 2014
DOI:10.1021/am4048267
Nanodielectric materials with high dielectric constant, low dielectric loss, and high energy storage capability are highly desirable in modern electric and electronics industries. It has been proved that the preparation of core–shell structured dielectric polymer nanocomposites via “grafting from” method is an effective approach to these materials. However, by using this approach, the deep understanding of the structure–dielectric property relationship of the core–shell structured nanodielectrics has been limited because of the lack of detailed information (e.g., molecular weight, grafting density) about the macromolecules grafted onto the nanoparticle surfaces. In this work, by the combination of reversible addition–fragmentation chain transfer (RAFT) polymerization and thiol–ene click reaction, two types of core–shell structured polymer@BaTiO3 (polymer@BT) nanocomposites with high dielectric constant and low dielectric loss were successfully prepared via a “grafting to” method. Compared with the “grafting from” method, this “grafting to” method has two merits: the molecular weight of the polymer chains in the shell layer can be easily controlled and the grafting density can be tailored by changing the molecular weight of the grafting polymer. Moreover, a clear insight into the relationship among the dielectric properties and energy storage capability of the core–shell structured polymer@BT nanocomposites, the molecular weight of the polymer chains, and the grafting density of the core–shell structured nanoparticles was achieved. The study provides new insights into the design and preparation of nanodielectric materials with desirable dielectric properties.Keywords: click reaction; core−shell structure; dielectric constant; dielectric loss; energy storage; nanocomposites; reversible addition−fragmentation chain transfer (RAFT) polymerization; thiol−ene;
Co-reporter:Ming Zhu, Xingyi Huang, Ke Yang, Xing Zhai, Jun Zhang, Jinliang He, and Pingkai Jiang
ACS Applied Materials & Interfaces 2014 Volume 6(Issue 22) pp:19644
Publication Date(Web):November 3, 2014
DOI:10.1021/am504428u
The interfacial region plays a critical role in determining the electrical properties and energy storage density of dielectric polymer nanocomposites. However, we still know a little about the effects of electrical properties of the interfacial regions on the electrical properties and energy storage of dielectric polymer nanocomposites. In this work, three types of core–shell structured polymer@BaTiO3 nanoparticles with polymer shells having different electrical properties were used as fillers to prepare ferroelectric polymer nanocomposites. All the polymer@BaTiO3 nanoparticles were prepared by surface-initiated reversible-addition–fragmentation chain transfer (RAFT) polymerization, and the polymer shells were controlled to have the same thickness. The morphology, crystal structure, frequency-dependent dielectric properties, breakdown strength, leakage currents, energy storage capability, and energy storage efficiency of the polymer nanocomposites were investigated. On the other hand, the pure polymers having the same molecular structure as the shells of polymer@BaTiO3 nanoparticles were also prepared by RAFT polymerization, and their electrical properties were provided. Our results show that, to achieve nanocomposites with high discharged energy density, the core–shell nanoparticle filler should simultaneously have high dielectric constant and low electrical conductivity. On the other hand, the breakdown strength of the polymer@BaTiO3-based nanocomposites is highly affected by the electrical properties of the polymer shells. It is believed that the electrical conductivity of the polymer shells should be as low as possible to achieve nanocomposites with high breakdown strength.Keywords: breakdown strength; core−shell nanoparticles; dielectric constants; energy storage; nanocomposite; poly(vinylidene fluoride); reversible-addition−fragmentation chain transfer (RAFT) polymerization
Co-reporter:Chao Wu, Lijun Fang, Xingyi Huang, and Pingkai Jiang
ACS Applied Materials & Interfaces 2014 Volume 6(Issue 23) pp:21026
Publication Date(Web):November 7, 2014
DOI:10.1021/am505908d
Graphene foams have showed huge application potentials owing to their unique 3D structure and superior properties. Thus, it is highly desired to develop a simple and effective pathway to fabricate high performance graphene-based foams. Here, we present a polymer template-assisted assembly strategy for fabricating a novel class of graphene/AgNW hybrid foams. The hybrid foams show 3D ordered microstructures, high thermal stability, and excellent electrical and mechanical properties, and demonstrate huge application potential in the fields of flexible and stretchable conductors. Importantly, the polymer-template assisted assembly technique is simple, scalable, and low-cost, providing a new synthesis protocol for various multifunctional graphene hybrid foam-based composites.Keywords: assembly; flexible conductors; graphene; hybrid foams; silver nanowires
Co-reporter:Chao Wu;Xinfeng Wu;Rong Qian;Pingkai Jiang
Advanced Materials 2013 Volume 25( Issue 39) pp:5658-5662
Publication Date(Web):
DOI:10.1002/adma.201302406
Co-reporter:Chao Wu;Genlin Wang;Libing Lv;Gan Chen;Guangyv Li ;Pingkai Jiang
Advanced Functional Materials 2013 Volume 23( Issue 4) pp:506-513
Publication Date(Web):
DOI:10.1002/adfm.201201231
Abstract
Polymer-based materials with high electrical conductivity are of considerable interest because of their wide range of applications. The construction of a 3D, compactly interconnected graphene network can offer a huge increase in the electrical conductivity of polymer composites. However, it is still a great challenge to achieve desirable 3D architectures in the polymer matrix. Here, highly conductive polymer nanocomposites with 3D compactly interconnected graphene networks are obtained using a self-assembly process. Polystyrene (PS) and ethylene vinyl acetate (EVA) are used as polymer matrixes. The obtained PS composite film with 4.8 vol% graphene shows a high electrical conductivity of 1083.3 S/m, which is superior to that of the graphene composite prepared by a solvent mixing method. The electrical conductivity of the composites is closely related to the compact contact between graphene sheets in the 3D structures and the high reduction level of graphene sheets. The obtained EVA composite films with the 3D graphene structure not only show high electrical conductivity but also exhibit high flexibility. Importantly, the method to fabricate 3D graphene structures in polymer matrix is facile, green, low-cost, and scalable, providing a universal route for the rational design and engineering of highly conductive polymer composites.
Co-reporter:Ke Yang, Xingyi Huang, Yanhui Huang, Liyuan Xie, and Pingkai Jiang
Chemistry of Materials 2013 Volume 25(Issue 11) pp:2327
Publication Date(Web):May 16, 2013
DOI:10.1021/cm4010486
Polymer nanocomposites with high energy density and low dielectric loss are highly desirable in electronic and electric industry. Achieving the ability to tailor the interface between polymer and nanoparticle is the key issue to realize desirable dielectric properties and high energy density in the nanocomposites. However, the understanding of the role of interface on the dielectric properties and energy density of polymer nanocomposites is still very poor. In this work, we report a novel strategy to improve the interface between the high dielectric constant nanoparticles (i.e., BaTiO3) and ferroelectric polymer [i.e., poly(vinylidene fluoride-co-hexafluoro propylene)]. Core–shell structured BaTiO3 nanoparticles either with different shell thickness or with different molecular structure of the shell were prepared by grafting two types of fluoroalkyl acrylate monomers via surface-initiated reversible addition–fragmentation chain transfer (RAFT) polymerization. The dielectric properties and energy storage capability of the corresponding nanocomposites were investigated by broadband dielectric spectroscopy and electric displacement-electric field loop measurement, respectively. The results show that high energy density and low dielectric loss are successfully realized in the nanocomposites. Moreover, the energy storage densities of the P(VDF-HFP)-based nanocomposites could be tailored by adjusting the structure and thickness of the fluoro-polymer shell. The approach described is applicable to a wide range of nanoparticles and polymer matrix, thereby providing a new route for preparing polymer-based nanocomposites used in electronic and electric industry.Keywords: dielectric loss; energy density; interface; polymer nanocomposites; RAFT polymerization;
Co-reporter:Chao Wu, Xingyi Huang, Xinfeng Wu, Liyuan Xie, Ke Yang and Pingkai Jiang
Nanoscale 2013 vol. 5(Issue 9) pp:3847-3855
Publication Date(Web):25 Mar 2013
DOI:10.1039/C3NR00625E
Polymer-based materials with a high dielectric constant show great potential for energy storage applications. Since the intrinsic dielectric constant of most polymers is very low, the integration of carbon nanotubes (CNTs) into the polymers provides an attractive and promising way to reach a high dielectric constant owing to their outstanding intrinsic physical performances. However, these CNT-based composites usually suffer from high dielectric loss, low breakdown strength and the difficulty to tailor the dielectric constant. Herein, we have designed and fabricated a new class of candidates composed of graphene oxide-encapsulated carbon nanotube (GO-e-CNT) hybrids. The obtained GO-e-CNT–polymer composites not only exhibit a high dielectric constant and low dielectric loss, but also have a highly enhanced breakdown strength and maximum energy storage density. Moreover, the dielectric constant of the composites can be tuned easily by tailoring the loading of GO-e-CNTs. It is believed that the GO shells around CNTs play an important role in realizing the high dielectric performances of the composites. GO shells can not only effectively improve the dispersion of CNTs, but also act as insulation barriers for suppressing leakage current and increasing breakdown strength. Our strategy provides a new pathway to achieve CNT-based polymer composites with high dielectric performances for energy storage applications.
Co-reporter:Liyuan Xie, Xingyi Huang, Yanhui Huang, Ke Yang, and Pingkai Jiang
ACS Applied Materials & Interfaces 2013 Volume 5(Issue 5) pp:1747
Publication Date(Web):February 4, 2013
DOI:10.1021/am302959n
Polymer nanocomposites with the dielectric constant comparable to that of percolative composites are successfully prepared by using core–shell structured hyperbranched aromatic polyamide grafted barium titanate (BT-HBP) hybrid nanofiller. Poly(vinylidene fluoride-trifluoroethylene-chlorofluoroethylene) (PVDF-TrFE-CFE) was used as the polymer matrix because of its high intrinsic dielectric constant and easy processability. The BT-HBP hybrid nanofiller were prepared by a solution polymerization of diaminobenzoic acid on the surface of amino-funcationalized BT nanoparticles. Nuclear magnetic resonance (1H NMR) and transmission electron microscopy (TEM) were used to verify the chemical structure of the hyperbranched aromatic polyamide and core-shell structure of the hybrid filler, respectively. It was found that the nanocomposite with 40 vol % BaTiO3–HBP had a dielectric constant of 1485.5 at 1000 Hz, whereas the corresponding nanocomposite sample with untreated BaTiO3 only showed a dielectric constant of 206.3. Compared with classic percolative composites, the advantage of the PVDF-TrFE-CFE/BaTiO3–HBP nanocomposites is that the composites show high enough breakdown strength and high dielectric constant simultaneously. An enhanced interfacial polarization mechanism between the BT-HBP and the polymer matrix was suggested for understanding the observed unusually high dielectric constant.Keywords: barium titanate nanoparticles; core−shell structure; high dielectric constant; interfacial polarization; poly (vinylidene fluoride-trifluoroethylene-chlorofluoroethylene);
Co-reporter:Liyuan Xie, Xingyi Huang, Bao-Wen Li, Chunyi Zhi, Toshikatsu Tanaka and Pingkai Jiang
Physical Chemistry Chemical Physics 2013 vol. 15(Issue 40) pp:17560-17569
Publication Date(Web):21 Aug 2013
DOI:10.1039/C3CP52799A
Dielectric polymer nanocomposites with high dielectric constant have wide applications in high energy density electronic devices. The introduction of high dielectric constant ceramic nanoparticles into a polymer represents an important route to fabricate nanocomposites with high dielectric constant. However, the nanocomposites prepared by this method generally suffer from relatively low breakdown strength and high dielectric loss, which limit the further increase of energy density and energy efficiency of the nanocomposites. In this contribution, by using core–satellite structured ultra-small silver (Ag) decorated barium titanate (BT) nanoassemblies, we successfully fabricated high dielectric constant polymer nanocomposites with enhanced breakdown strength and lower dielectric loss in comparison with conventional polymer–ceramic particulate nanocomposites. The discharged energy density and energy efficiency are derived from the dielectric displacement–electric field loops of the polymer nanocomposites. It is found that, by using the core–satellite structured Ag@BT nanoassemblies as fillers, the polymer nanocomposites can not only have higher discharged energy density but also have high energy efficiency. The mechanism behind the improved electrical properties was attributed to the Coulomb blockade effect and the quantum confinement effect of the introduced ultra-small Ag nanoparticles. This study could serve as an inspiration to enhance the energy storage densities of dielectric polymer nanocomposites.
Co-reporter:Liyuan Xie, Xingyi Huang, Yanhui Huang, Ke Yang, and Pingkai Jiang
The Journal of Physical Chemistry C 2013 Volume 117(Issue 44) pp:22525-22537
Publication Date(Web):October 4, 2013
DOI:10.1021/jp407340n
Polymer nanocomposites with high dielectric constant have extensive applications in the electronic and electrical industry because of ease of processing and low cost. Blending and in situ polymerization are two conventional methods for the preparation of polymer nanocomposites. However, the resulting nanocomposites, particularly highly filled nanocomposites, generally have some disadvantages such as high dielectric loss and low dielectric constant and thus show low energy density and low energy efficiency. Here we developed a core@double-shell strategy to prepare barium titanate (BT)-based high performance polymer nanocomposites, in which the first shell is hyperbranched aromatic polyamide (HBP) and the second shell is poly(methyl methacrylate) (PMMA). This method utilized the advantages of both polymer shells, resulting in superior dielectric property which cannot be achieved in nanocomposites prepared by the conventional blending methods. It is found that, compared with the conventional solution blended BT/PMMA nanocomposites, the core@double-shell structured BT@HBP@PMMA nanocomposites had higher dielectric constant and lower dielectric loss. The energy densities of BT@HBP@PMMA nanocomposites were higher than that of BT/PMMA nanocomposites accordingly. The dielectric response of the nanocomposites was analyzed, and the mechanisms resulting in the higher dielectric constant and lower dielectric loss in BT@HBP@PMMA nanocomposites were proposed. This study suggests that the core@double-shell strategy shows strong potential for preparing polymer nanocomposites with desirable dielectric properties.
Co-reporter:Chao Wu, Xingyi Huang, Genlin Wang, Xinfeng Wu, Ke Yang, Shengtao Li and Pingkai Jiang
Journal of Materials Chemistry A 2012 vol. 22(Issue 14) pp:7010-7019
Publication Date(Web):02 Mar 2012
DOI:10.1039/C2JM16901K
The incorporation of graphene sheets (GSs) into polymer matrices affords engineers an opportunity to synthesize polymer composites with excellent physical performances. However, the development of high performance GS-based composites is difficult because of the easy aggregation of GSs in a polymer matrix as well as the weak interfacial adhesion between GSs and the host polymer. Herein, we present a simple and effective route to hyperbranched aromatic polyamide functionalized graphene sheets (GS–HBA). The resulting GS-HBA exhibits uniform dispersion in a thermoplastic polyurethane (TPU) matrix and strong adhesion with the matrix by hydrogen-bond coupling, which improve the load transfer efficiency from the matrix to the GSs. Thus, the GS–HBA–TPU composites possess excellent mechanical performance and high dielectric performance. It has been demonstrated that the GS–HBA composite has higher modulus, higher tensile strength and higher yield strength, and remains at nearly the same strain at break when compared with the composites with graphene oxide, ethylene diamine-modified graphene, and hydrazine reduced graphene. In addition, the hyperbranched polymer chains allow construction of a large number of microcapacitors and suppress the leakage current by isolating the GSs in a TPU matrix, resulting in a higher permittivity and lower loss tangent for the GS–HBA composite in comparison with ethylene diamine-modified graphene, or hydrazine reduced-graphene composites.
Co-reporter:Mi Li, Xingyi Huang, Chao Wu, Haiping Xu, Pingkai Jiang and Toshikatsu Tanaka
Journal of Materials Chemistry A 2012 vol. 22(Issue 44) pp:23477-23484
Publication Date(Web):08 Oct 2012
DOI:10.1039/C2JM34683D
Novel polyaniline decorated reduced graphene oxide (rPANI@rGO) two-dimensional (2D) hybrids sheets were successfully prepared by in situ polymerization of aniline on graphene oxide (GO) sheets and successive reduction by hydrazine. PANI is heavily reduced, thus it is electrically insulating. The hybrid sheets were used as a novel filler for high performance poly(methyl methacrylate) (PMMA) nanocomposites. Our results show that, when compared with the PMMA/rGO composites, the PMMA/rPANI@rGO nanocomposites not only show a high dielectric constant but also have low dielectric loss. For example, at 1000 Hz, a dielectric constant of 40 and a dielectric loss of 0.12 were observed in the PMMA/rPANI@rGO nanocomposite with rGO/PMMA volume ratio of 6%, whereas the dielectric constant and dielectric loss of PMMA/rGO composite with rGO/PMMA volume ratio of 6% are about 20 and 1250, respectively. More importantly, the dielectric properties of PMMA/rPANI@rGO nanocomposites can be tuned by controlling the addition of the hybrid sheets. The improved dielectric properties in PMMA/rPANI@rGO nanocomposites should originate from the isolation effect of rPANI on the rGO in PMMA matrix, which not only improves the dispersion of rGO but also hinders the direct electrical contact between rGO. This research sets up a novel route to polymer composites with high dielectric constants and low dielectric loss, and also expands the application space of graphene-based fillers.
Co-reporter:Ke Yang;Liyuan Xie;Chao Wu;Pingkai Jiang;Toshikatsu Tanaka
Macromolecular Rapid Communications 2012 Volume 33( Issue 22) pp:1921-1926
Publication Date(Web):
DOI:10.1002/marc.201200361
Abstract
A novel route to prepare core–shell structured nanocomposites with excellent dielectric performance is reported. This approach involves the grafting of polystyrene (PS) from the surface of BaTiO3 by an in situ RAFT polymerization. The core–shell structured PS/BaTiO3 nanocomposites not only show significantly increased dielectric constant and very low dielectric loss, but also have a weak frequency dependence of dielectric properties over a wide range of frequencies. In addition, the dielectric constant of the nanocomposites can also be easily tuned by varying the thickness of the PS shell. Our method is very promising for preparing high-performance nanocomposites used in energy-storage devices.
Co-reporter:Xingyi Huang, Tomonori Iizuka, Pingkai Jiang, Yoshimichi Ohki, and Toshikatsu Tanaka
The Journal of Physical Chemistry C 2012 Volume 116(Issue 25) pp:13629-13639
Publication Date(Web):June 5, 2012
DOI:10.1021/jp3026545
The interface between filler and matrix has long been a critical problem that affects the thermal conductivity of polymer composites. The effects of the interface on the thermal conductivity of the composite with low filler loading are well documented, whereas the role of the interface in highly filled polymer composites is not clear. Here we report on a systematic study of the effects of interface on the thermal conductivity of highly filled epoxy composites. Six kinds of surface treated and as received AlN particles are used as fillers. Three kinds of treated AlN are functionalized by silanes, i.e., amino, epoxy, and mercapto group terminated silanes. Others are functionalized by three kinds of materials, i.e., polyhedral oligomeric silsesquioxane (POSS), hyperbranched polymer, and graphene oxide (GO). An intensive study was made to clarify how the variation of the modifier would affect the microstructure, density, interfacial adhesion, and thus the final thermal conductivity of the composites. It was found that the thermal conductivity enhancement of the composites is not only dependent on the type and physicochemical nature of the modifiers but also dependent on the filler loading. In addition, some unexpected results were found in the composites with particle loading higher than the percolation threshold. For instance, the composites with AlN treated by the silane uncapable of reacting with the epoxy resin show the most effective enhancement of the thermal conductivity. Finally, dielectric spectroscopy was used to evaluate the insulating properties of the composites. This work sets the way toward the choice of a proper modifier for enhancing the thermal conductivity of highly filled dielectric polymer composites.
Co-reporter:Jinhong Yu, Xingyi Huang, Chao Wu, Xinfeng Wu, Genlin Wang, Pingkai Jiang
Polymer 2012 Volume 53(Issue 2) pp:471-480
Publication Date(Web):24 January 2012
DOI:10.1016/j.polymer.2011.12.040
Interface is a critical factor in determining the properties of polymer composites. Generally, the physicochemical properties of the interface are closely associated with the surface chemistry of fillers. In this study, we report a simple method to fabricate boron nitride (BN) nanoplatelets using a sonication-centrifugation technique and investigate the effects of functionalization BN nanoplatelets on thermal properties of epoxy composites. Two methods have been used for functionalizing BN nanoplatelets: non-covalent functionalization by octadecylamine (ODA) and covalent functionalization by hyperbranched aromatic polyamide (HBP). The functionalized BN nanoplatelets were characterized by Fourier-transform infrared (FT-IR), nuclear magnetic resonance (1H NMR), thermogravimetric analyzer (TGA), and transmission electron microscopy (TEM). Epoxy composites were fabricated by incorporating three kinds of fillers: BN nanoplatelets, BN nanoplatelets functionalized by ODA (BN-ODA), and BN nanoplatelets functionalized by HBP (BN-HBP). Our results show that the BN-HBP results in a strong interface and thus the composites exhibit significantly increased glass transition temperature, thermal decomposition temperature, thermal conductivity and dynamic thermal mechanical modulus. BN-ODA produced intermediate interface interaction, resulting in a moderate improvement of thermal properties. The composites with BN nanoplatelets show the least improvements of thermal properties.
Co-reporter:Wei Wu ; Xingyi Huang ; Shengtao Li ; Pingkai Jiang ;Tanaka Toshikatsu
The Journal of Physical Chemistry C 2012 Volume 116(Issue 47) pp:24887-24895
Publication Date(Web):October 31, 2012
DOI:10.1021/jp3088644
High dielectric constant polymer composites capable of withstanding a high electrical field have much application in electronic devices and electrical equipment because of their ease of processing, flexibility, and low cost. Conventional polymer composites with a high dielectric constant, namely ceramic particulate composites and conductive filler based percolative composites, either show low dielectric enhancement or cannot withstand high electric field. Here we report a new strategy for preparing high dielectric constant polymer composites by using novel three-dimensional zinc oxide (3D ZnO) superstructures as fillers. Two kinds of 3D ZnO (flower-like and walnut-like) superstructures were prepared via a template-free solvothermal method. Their poly(vinylidene fluoride) (PVDF) composites as well as commercial ZnO filled PVDF composite were investigated by a broadband dielectric spectroscopy at a wide temperature range (−50 to +150 °C). Our results showed that, compared with the commercial ZnO, the newly synthesized ZnO superstructures not only significantly increase the dielectric constant of their PVDF composites but also show similar effect on the breakdown strength of their composites. For instance, the dielectric constants (100 Hz) of the composite samples with commercial ZnO, flower-like, and walnut-like ZnO superstructures are 19.4, 221.1, and 104.9, respectively, whereas their breakdown strengths are 45, 42, and 40 kV/mm, respectively. The dielectric investigation evidenced that the higher dielectric constant in the composites with ZnO superstructures should be attributed to the formation of a ZnO percolation network.
Co-reporter:Liyuan Xie, Xingyi Huang, Chao Wu and Pingkai Jiang
Journal of Materials Chemistry A 2011 vol. 21(Issue 16) pp:5897-5906
Publication Date(Web):23 Mar 2011
DOI:10.1039/C0JM04574H
Core-shell structured BaTiO3/poly(methyl methacrylate) (PMMA) nanocomposites were successfully prepared by in situ atom transfer radical polymerization (ATRP) of methyl methacrylate (MMA) from the surface of BaTiO3 nanoparticles. A broadband dielectric spectrometer was used to investigate the temperature dependence of the dielectric properties of the nanocomposites in a frequency range from 0.1 Hz to 1 MHz. It was found that the nanocomposites not only showed a significantly increased dielectric constant when compared with pure PMMA, but also showed the inherent low loss of the base polymer in a wide range of frequencies. Only in the very low frequency/high temperature range, can a higher dielectric loss can be observed in the nanocomposites. It was also found that the effective dielectric constant of the core-shell structured hybrid nanoparticles can be tailored by varying the polymer shell thickness. The dielectric response of beta relaxation of PMMA was also studied and the results showed that the nanoparticles had no influence upon the relaxation activation energy. Fourier-transform infrared spectroscopy (FTIR) and 1H NMR spectra confirmed the chemical structure of the PMMA shell on the surface of the BaTiO3 nanoparticles. Transmission electron microscopy (TEM) and thermogravimetric analysis (TGA) results revealed that the PMMA shell thickness could be well controlled by tuning the feed ratio of MMA to BaTiO3.
Co-reporter:Chao Wu, Xingyi Huang, Liyuan Xie, Xingfeng Wu, Jinghong Yu and Pingkai Jiang
Journal of Materials Chemistry A 2011 vol. 21(Issue 44) pp:17729-17736
Publication Date(Web):06 Oct 2011
DOI:10.1039/C1JM12903A
High permittivity polymer-based materials are highly desirable due to their inherent advantages of being easy to process, flexible and light weight. Herein, a new strategy for the development of polymer composites with high permittivity and low dielectric loss has been proposed based on morphology-controllable graphene–TiO2 nanorod hybrid nanostructures. These hybrid nanostructures possess large aspect ratio, high surface area and high electric conductivity graphene sheets, which provide ideal electrodes in the construction of microcapacitors. In addition, the morphology-controllable TiO2 nanorod decoration effectively prevents direct contact between the graphene sheets in the composite, which give advantages for forming a large microcapacitor network and suppressing the leakage current. As a consequence, a polystyrene composite with 10.9 vol% graphene–TiO2 nanorod sheets exhibits a very high permittivity of 1741 at 102 Hz, which is 643 times higher than the value for pure polystyrene (2.7), and low dielectric loss (tanα) of only 0.39. The permittivity of the composites can be controlled by controlling the amount of nanorod decoration on the graphene substrates, which provides a new pathway for tuning the permittivity of polymer composites. We expect that our strategy of controlling filler interface will be applied to acquire more polymer composites with high permittivity and low dielectric loss.
Co-reporter:Yong Li, Xingyi Huang, Zhiwei Hu, Pingkai Jiang, Shengtao Li, and Toshikatsu Tanaka
ACS Applied Materials & Interfaces 2011 Volume 3(Issue 11) pp:4396
Publication Date(Web):October 18, 2011
DOI:10.1021/am2010459
Dielectric polymer composites with high dielectric constants and high thermal conductivity have many potential applications in modern electronic and electrical industry. In this study, three-phase composites comprising poly(vinylidene fluoride) (PVDF), barium titanate (BT) nanoparticles, and β-silicon carbide (β-SiC) whiskers were prepared. The superiority of this method is that, when compared with the two-phase PVDF/BT composites, three-phase composites not only show significantly increased dielectric constants but also have higher thermal conductivity. Our results show that the addition of 17.5 vol % β-SiC whiskers increases the dielectric constants of PVDF/BT nanocomposites from 39 to 325 at 1000 Hz, while the addition of 20.0 vol % β-SiC whiskers increases the thermal conductivity of PVDF/BT nanocomposites from 1.05 to 1.68 W m–1 K–1 at 25 °C. PVDF/β-SiC composites were also prepared for comparative research. It was found that PVDF/BT/β-SiC composites show much higher dielectric constants in comparison with the PVDF/β-SiC composites within 17.5 vol % β-SiC. The PVDF/β-SiC composites show dielectric constants comparable to those of the three-phase composites only when the β-SiC volume fraction is 20.0%, whereas the dielectric loss of the PVDF/β-SiC composites was much higher than that of the three-phase composites. The frequency dependence of the dielectric property for the composites was investigated by using broad-band (10–2–106 Hz) dielectric spectroscopy.Keywords: barium titanate (BaTiO3) nanoparticles; dielectric constant; poly(vinylidene fluoride) (PVDF); silicon carbide (β-SiC) whiskers; thermal conductivity;
Co-reporter:Jinhong Yu, Xingyi Huang, Lichun Wang, Peng Peng, Chao Wu, Xinfeng Wu and Pingkai Jiang
Polymer Chemistry 2011 vol. 2(Issue 6) pp:1380-1388
Publication Date(Web):02 Apr 2011
DOI:10.1039/C1PY00096A
Epoxy nanocomposites with hyperbranched aromatic polyamide grafted alumina (Al2O3) nanoparticles as inclusions were prepared and their thermal properties were studied. The Al2O3 nanoparticles were firstly treated with a silane coupling agent to introduce amine groups, then grafting of the hyperbranched aromatic polyamide started from the modified surface. Fourier transform infrared spectroscopy (FTIR) and nuclear magnetic resonance spectroscopy (NMR) analysis proved hyperbranched aromatic polyamide grafted Al2O3 nanoparticles were successfully prepared by solution polymerization. Transmission electron microscopy (TEM) showed that there was a thin polymer layer on the Al2O3 nanoparticles surface, which contributes to the uniform dispersion of Al2O3 nanoparticles in epoxy matrix and the improvement of the interfacial interaction between Al2O3 nanoparticles and epoxy matrix. Thus the glass transition temperature, thermal stability, thermal conductivity and thermomechanical properties of nanocomposites were enhanced.
Co-reporter:Zhishen Ma, Xingyi Huang, Pingkai Jiang
Polymer Degradation and Stability 2010 Volume 95(Issue 9) pp:1943-1949
Publication Date(Web):September 2010
DOI:10.1016/j.polymdegradstab.2010.04.002
In this work, we investigated the effects of an ethylene propylene diene monomer (EPDM) and poly[styrene-b-(ethylene-co-butylene)-b-styrene] (SEBS) on the water tree resistance in cross-linked polyethylene (XLPE). The XLPE/EPDM and XLPE/SEBS blend samples were prepared by melting compounding and subsequent compression molding. It was found that SEBS could greatly increase the water tree resistance of XLPE and the resistance performance was improved with SEBS content within 15 phr, whereas EPDM did not show any improvement in the water tree resistance of XLPE. The frequency dependent behaviors of the water treeing phenomena and the effects of EVA on the water tree resistance of XLPE/EPDM and XLPE/SEBS blends were also investigated. The water treeing phenomena of the blends were interpreted from the viewpoints of electro-mechanical and electro-chemical mechanisms.
Co-reporter:Zhishen Ma;Pingkai Jiang;Genlin Wang
Journal of Applied Polymer Science 2010 Volume 115( Issue 6) pp:3168-3176
Publication Date(Web):
DOI:10.1002/app.31421
Abstract
Water treeing is one of the main deterioration phenomena observed in the polymeric insulation of extruded crosslinked polyethylene (XLPE) cables, which can affect the service life of power cables. In this work, we investigated the effect of grafting of a silane (vinyl trimethoxysilane, VTMS) on the resistance of XLPE to water treeing. A series of water-treeing tests, the mechanical and dielectric measurements indicated that the silane-grafting could significantly improve the water tree resistance of the conventional XLPE cable insulation with little influences on its dielectric properties, e.g., the dielectric breakdown strength, dielectric constant and loss tangent, and its mechanical performance. It was found that there exists an optimum value of VTMS concentration (about 0.6 phr) corresponding to the minimum water tree length. The water tree resistance mechanism of silane-grafted XLPE was proposed on the basis of the process of silane hydrolysis and crosslinking. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010
Co-reporter:Xingyi Huang, Liyuan Xie, Pingkai Jiang, Genlin Wang, Yi Yin
European Polymer Journal 2009 Volume 45(Issue 8) pp:2172-2183
Publication Date(Web):August 2009
DOI:10.1016/j.eurpolymj.2009.05.019
This paper presents the results of morphological and ac electrical investigations on low density polyethylene (LDPE) composites with octavinyl polyhedral oligomeric silsesquioxane (POSS). It has been shown that at low loadings, the frequency dependence of dielectric constant and dielectric loss for the LDPE/POSS composites showed unusual behaviors when compared with conventional (micro-sized particulates) composites. The ac breakdown strength was measured and statistical analysis was applied to the results to determine the effects of POSS loadings on the dielectric strength of LDPE. The morphological characterization showed that the presence of POSS additives apparently altered the supermolecular structure of LDPE and resulted in more homogeneous morphology when compared with the neat LDPE. The structure–property relationship was discussed and it was concluded that the final dielectric properties of the composites were determined not only by the incorporation of POSS additives but also by the supermolecular structure of LDPE. Rheological analyses of LDPE/POSS composite were also performed and the results showed that the octavinyl-POSS had good compatibility with LDPE.
Co-reporter:Jian Chen;Pingkai Jiang;Genlin Wang
Journal of Applied Polymer Science 2009 Volume 112( Issue 2) pp:1076-1081
Publication Date(Web):
DOI:10.1002/app.29552
Abstract
We reported the effects of four kinds of aromatic compounds (diphenylacetylene, biphenyl, anthracene, pyrene) on the gamma-irradiation resistance of the styrene-ethylene-butylene-styrene/polystyrene (SEBS/PS) blends. It was found that, after gamma irradiation, the blends with aromatic additives had improved mechanical, dielectric, and thermal characteristics when compared with those samples without additives, and that among the four compounds, pyrene was shown to be the most effective additive. The rheological results were consistent with the changes of mechanical, dielectric, and thermal properties, and the blends with pyrene had the lowest values of melt-flow rate after gamma irradiation. The possible mechanism of the effects of the aromatic compounds on the irradiation resistance SEBS/PS blends was also suggested. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009
Co-reporter:Xingyi Huang;Chonung Kim;Zhisen Ma;Pingkai Jiang;Yi Yin;Zhe Li
Journal of Polymer Science Part B: Polymer Physics 2008 Volume 46( Issue 20) pp:2143-2154
Publication Date(Web):
DOI:10.1002/polb.21547
Abstract
Polyethylene (PE)/aluminum (Al) nanocomposites with various filler contents were prepared by a solution compounding method. We investigated the influence of the surface modification of Al nanoparticles on the microstructure and physical properties of the nanocomposites. The silane coupling agent octyl-trimethoxysilane was shown to significantly increase interfacial compatibility between the polymer phase and Al nanoparticles. Rheological percolation threshold values were determined by analyzing the improvement in storage modulus at low frequencies depending on the Al loadings. Lower percolation threshold values were obtained for the composites prepared with the original nanoparticles than those prepared with the silane-modified Al nanoparticles. A strong correlation between the time and concentration dependences of dc conductivity and rheological properties was observed in the different nanocomposite systems. The rheological threshold of the composites is smaller than the percolation threshold of electrical conductivity for both of the nanocomposite systems. The difference in percolation threshold is understood in terms of the smaller particle–particle distance required for electrical conduction when compared with that required to impede polymer mobility. It was directly shown by SEM characterization that the nanoparticle surface modification yielded better filler dispersion, as is consistent with our rheological and electrical analysis. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 2143–2154, 2008
Co-reporter:Xingyi Huang;Qingquan Ke;Chonung Kim;Hanfang Zhong;Ping Wei;Genlin Wang;Fei Liu;Pingkai Jiang
Polymer Engineering & Science 2007 Volume 47(Issue 7) pp:1052-1061
Publication Date(Web):29 MAY 2007
DOI:10.1002/pen.20784
The nonisothermal crystallization and melting behavior of LDPE and LDPE/Al nano- and microcomposites prepared from melt compounding were studied using differential scanning calorimetry (DSC). The DSC results show that the Al nanoparticles can either facilitate or hinder the crystallization of LDPE, depending on the dispersion of the nanoparticles in LDPE. The well-dispersed Al nanoparticles do not have nucleating effects and mainly act as obstacles in the crystallization process, but the agglomerates of Al nanoparticles can act as nucleating agents and slightly accelerate the crystallization process of LDPE. The Al microparticles have nucleating effect and facilitate the crystallization process of LDPE. The combined Avrami–Ozawa equation was used to describe the nonisothermal crystallization process. It was found that the combined Avrami–Ozawa method can successfully describe the nonisothermal crystallization process. The melting behavior indicates that the lamellar thickness distribution of the nanocomposites and microcomposites is not significantly changed in comparison with the neat LDPE. POLYM. ENG. SCI., 47:1052–1061, 2007. © 2007 Society of Plastics Engineers
Co-reporter:Liyuan Xie, Xingyi Huang, Chao Wu and Pingkai Jiang
Journal of Materials Chemistry A 2011 - vol. 21(Issue 16) pp:NaN5906-5906
Publication Date(Web):2011/03/23
DOI:10.1039/C0JM04574H
Core-shell structured BaTiO3/poly(methyl methacrylate) (PMMA) nanocomposites were successfully prepared by in situ atom transfer radical polymerization (ATRP) of methyl methacrylate (MMA) from the surface of BaTiO3 nanoparticles. A broadband dielectric spectrometer was used to investigate the temperature dependence of the dielectric properties of the nanocomposites in a frequency range from 0.1 Hz to 1 MHz. It was found that the nanocomposites not only showed a significantly increased dielectric constant when compared with pure PMMA, but also showed the inherent low loss of the base polymer in a wide range of frequencies. Only in the very low frequency/high temperature range, can a higher dielectric loss can be observed in the nanocomposites. It was also found that the effective dielectric constant of the core-shell structured hybrid nanoparticles can be tailored by varying the polymer shell thickness. The dielectric response of beta relaxation of PMMA was also studied and the results showed that the nanoparticles had no influence upon the relaxation activation energy. Fourier-transform infrared spectroscopy (FTIR) and 1H NMR spectra confirmed the chemical structure of the PMMA shell on the surface of the BaTiO3 nanoparticles. Transmission electron microscopy (TEM) and thermogravimetric analysis (TGA) results revealed that the PMMA shell thickness could be well controlled by tuning the feed ratio of MMA to BaTiO3.
Co-reporter:Liyuan Xie, Xingyi Huang, Bao-Wen Li, Chunyi Zhi, Toshikatsu Tanaka and Pingkai Jiang
Physical Chemistry Chemical Physics 2013 - vol. 15(Issue 40) pp:NaN17569-17569
Publication Date(Web):2013/08/21
DOI:10.1039/C3CP52799A
Dielectric polymer nanocomposites with high dielectric constant have wide applications in high energy density electronic devices. The introduction of high dielectric constant ceramic nanoparticles into a polymer represents an important route to fabricate nanocomposites with high dielectric constant. However, the nanocomposites prepared by this method generally suffer from relatively low breakdown strength and high dielectric loss, which limit the further increase of energy density and energy efficiency of the nanocomposites. In this contribution, by using core–satellite structured ultra-small silver (Ag) decorated barium titanate (BT) nanoassemblies, we successfully fabricated high dielectric constant polymer nanocomposites with enhanced breakdown strength and lower dielectric loss in comparison with conventional polymer–ceramic particulate nanocomposites. The discharged energy density and energy efficiency are derived from the dielectric displacement–electric field loops of the polymer nanocomposites. It is found that, by using the core–satellite structured Ag@BT nanoassemblies as fillers, the polymer nanocomposites can not only have higher discharged energy density but also have high energy efficiency. The mechanism behind the improved electrical properties was attributed to the Coulomb blockade effect and the quantum confinement effect of the introduced ultra-small Ag nanoparticles. This study could serve as an inspiration to enhance the energy storage densities of dielectric polymer nanocomposites.
Co-reporter:Chao Wu;Genlin Wang;Xinfeng Wu;Ke Yang;Shengtao Li;Pingkai Jiang
Journal of Materials Chemistry A 2012 - vol. 22(Issue 14) pp:
Publication Date(Web):2012/03/13
DOI:10.1039/C2JM16901K
The incorporation of graphene sheets (GSs) into polymer matrices affords engineers an opportunity to synthesize polymer composites with excellent physical performances. However, the development of high performance GS-based composites is difficult because of the easy aggregation of GSs in a polymer matrix as well as the weak interfacial adhesion between GSs and the host polymer. Herein, we present a simple and effective route to hyperbranched aromatic polyamide functionalized graphene sheets (GS–HBA). The resulting GS-HBA exhibits uniform dispersion in a thermoplastic polyurethane (TPU) matrix and strong adhesion with the matrix by hydrogen-bond coupling, which improve the load transfer efficiency from the matrix to the GSs. Thus, the GS–HBA–TPU composites possess excellent mechanical performance and high dielectric performance. It has been demonstrated that the GS–HBA composite has higher modulus, higher tensile strength and higher yield strength, and remains at nearly the same strain at break when compared with the composites with graphene oxide, ethylene diamine-modified graphene, and hydrazine reduced graphene. In addition, the hyperbranched polymer chains allow construction of a large number of microcapacitors and suppress the leakage current by isolating the GSs in a TPU matrix, resulting in a higher permittivity and lower loss tangent for the GS–HBA composite in comparison with ethylene diamine-modified graphene, or hydrazine reduced-graphene composites.
Co-reporter:Guanyao Wang, Xingyi Huang and Pingkai Jiang
Journal of Materials Chemistry A 2017 - vol. 5(Issue 12) pp:NaN3120-3120
Publication Date(Web):2017/02/27
DOI:10.1039/C7TC00387K
The attractiveness of dielectric polymer nanocomposites stems from their potential applications in electrical insulation and energy storage devices. However, the inevitable electrical mismatch and incompatibility between nanofillers and polymer matrices usually give rise to undesirable dielectric properties and weak energy storage capability. Despite the progress achieved to date, there is still plenty of room for further improvement in terms of energy storage of polymer nanocomposites. Herein, anatase TiO2 nanowires (NWs) were utilized as dopants into a ferroelectric polymer since their moderate dielectric constant is beneficial for alleviating the electric field intensification in the polymer–filler system. Besides, inspired by the strong adhesion property of mussels, a brush-like long-chain tailed dopamine derivative (h-DOPA) is employed to improve the inclusion of TiO2 NWs into the polymer matrix, leading to remarkably reduced dielectric loss and leakage current densities in comparison with the nanocomposites with raw nanowires. Benefiting from the excellent compatibility between these two components, the breakdown strength of these proposed nanocomposites decreases gently from ca. 520 MV m−1 to ca. 350 MV m−1, accompanied by nanofiller loadings from 2.5 vol% to 15 vol%. Moreover, the nanocomposite with 2.5 vol% h-DOPA@TiO2 NWs discharges an ultrahigh energy storage density of 11.13 J cm−3 at 520 MV m−1, while that of the pure polymer can reach only up to 8.75 J cm−3 at 500 MV m−1. A strikingly high energy density of 8.57 J cm−3 is also achieved with the nanofiller volume fraction as high as 15% at a low electric field of 350 MV m−1, nearly double that of pure P(VDF-HFP) (4.76 J cm−3 at 360 MV m−1). The results and methods presented here provide deep insights into a facile and versatile approach to fabricate polymer nanocomposites with high energy storage capability.
Co-reporter:Mi Li, Xingyi Huang, Chao Wu, Haiping Xu, Pingkai Jiang and Toshikatsu Tanaka
Journal of Materials Chemistry A 2012 - vol. 22(Issue 44) pp:NaN23484-23484
Publication Date(Web):2012/10/08
DOI:10.1039/C2JM34683D
Novel polyaniline decorated reduced graphene oxide (rPANI@rGO) two-dimensional (2D) hybrids sheets were successfully prepared by in situ polymerization of aniline on graphene oxide (GO) sheets and successive reduction by hydrazine. PANI is heavily reduced, thus it is electrically insulating. The hybrid sheets were used as a novel filler for high performance poly(methyl methacrylate) (PMMA) nanocomposites. Our results show that, when compared with the PMMA/rGO composites, the PMMA/rPANI@rGO nanocomposites not only show a high dielectric constant but also have low dielectric loss. For example, at 1000 Hz, a dielectric constant of 40 and a dielectric loss of 0.12 were observed in the PMMA/rPANI@rGO nanocomposite with rGO/PMMA volume ratio of 6%, whereas the dielectric constant and dielectric loss of PMMA/rGO composite with rGO/PMMA volume ratio of 6% are about 20 and 1250, respectively. More importantly, the dielectric properties of PMMA/rPANI@rGO nanocomposites can be tuned by controlling the addition of the hybrid sheets. The improved dielectric properties in PMMA/rPANI@rGO nanocomposites should originate from the isolation effect of rPANI on the rGO in PMMA matrix, which not only improves the dispersion of rGO but also hinders the direct electrical contact between rGO. This research sets up a novel route to polymer composites with high dielectric constants and low dielectric loss, and also expands the application space of graphene-based fillers.
Co-reporter:Chao Wu, Xingyi Huang, Liyuan Xie, Xingfeng Wu, Jinghong Yu and Pingkai Jiang
Journal of Materials Chemistry A 2011 - vol. 21(Issue 44) pp:NaN17736-17736
Publication Date(Web):2011/10/06
DOI:10.1039/C1JM12903A
High permittivity polymer-based materials are highly desirable due to their inherent advantages of being easy to process, flexible and light weight. Herein, a new strategy for the development of polymer composites with high permittivity and low dielectric loss has been proposed based on morphology-controllable graphene–TiO2 nanorod hybrid nanostructures. These hybrid nanostructures possess large aspect ratio, high surface area and high electric conductivity graphene sheets, which provide ideal electrodes in the construction of microcapacitors. In addition, the morphology-controllable TiO2 nanorod decoration effectively prevents direct contact between the graphene sheets in the composite, which give advantages for forming a large microcapacitor network and suppressing the leakage current. As a consequence, a polystyrene composite with 10.9 vol% graphene–TiO2 nanorod sheets exhibits a very high permittivity of 1741 at 102 Hz, which is 643 times higher than the value for pure polystyrene (2.7), and low dielectric loss (tanα) of only 0.39. The permittivity of the composites can be controlled by controlling the amount of nanorod decoration on the graphene substrates, which provides a new pathway for tuning the permittivity of polymer composites. We expect that our strategy of controlling filler interface will be applied to acquire more polymer composites with high permittivity and low dielectric loss.
Co-reporter:Liyuan Xie, Xingyi Huang, Ke Yang, Shengtao Li and Pingkai Jiang
Journal of Materials Chemistry A 2014 - vol. 2(Issue 15) pp:NaN5251-5251
Publication Date(Web):2014/01/21
DOI:10.1039/C3TA15156E
The introduction of high dielectric constant ceramic nanoparticles into an insulating polymer is an important approach to prepare high dielectric constant nanocomposites for electric energy storage applications. A key to obtaining desirable properties is the homogeneous dispersion of the nanoparticles in the corresponding polymer. Conventional methods used to improve the nanoparticle dispersion enhance the physical interaction between the nanoparticle and the polymer matrix via nanoparticle surface modification. In this work, the covalent bonding between the nanoparticle and the polymer matrix was utilized to simultaneously enhance the nanoparticle dispersion and nanoparticle/polymer interaction by functionalizing both the polymer and the nanoparticles. The poly(vinylidene fluoride-co-hexafluoropropylene) [PVDF-HFP] was functionalized with glycidyl methacrylate (GMA) via atom transfer radical polymerization. The barium titanate (BaTiO3) nanoparticles were modified by amino-terminated silane molecules. Then the nanocomposites were prepared by a “grafting to” method. Namely, grafting GMA functionalized PVDF-HFP to the surfaces of the BaTiO3 nanoparticles. The introduction of GMA into the PVDF-HFP not only increases the dielectric constant, but also changes the dielectric response of PVDF-HFP. More importantly, this “grafting to” approach results in core–shell structured BaTiO3@PVDF-HFP-GMA and thus a homogeneous dispersion of BaTiO3 nanoparticles in the nanocomposites. The dielectric constant, electric energy density and thermal conductivity of the nanocomposites are significantly enhanced with the increase of BaTiO3, while the dielectric loss shows a slight decrease as the nanoparticle loading increases.
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