Zhigang Xue

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Name: 薛志刚; ZhiGang Xue

Organization: Huazhong University of Science and Technology , China

Department: School of Chemistry and Chemical Engineering

Title: Associate Professor(PhD)

TOPICS

Polymer

Atom Transfer Radical Polymerization

Material Chemistry

Carbon Nanotubes

Chemicals
References

Novel sound insulation materials based on epoxy/hollow silica nanotubes composites

Co-reporter:Xuejun Shi, Jingyi Wu, Xiaoen Wang, Xingping Zhou, Xiaolin Xie, Zhigang Xue

Composites Part B: Engineering 2017 Volume 131(Volume 131) pp:

Publication Date(Web):15 December 2017

DOI:10.1016/j.compositesb.2017.07.055

The performance of a sound insulation material is highly dependent on the technology adopted for its construction. In this study, we synthesized the hollow silica nanotubes (HSNTs) and used them as functional fillers to fabricate a sound insulation nanocomposite based on the epoxy. The sound transmission loss (STL) values of the nanocomposites were measured using a four-microphones standing wave tube. The results showed that for samples with thickness of 3 mm, the STL values of the pure epoxy resin and of nanocomposites with 3 wt% of HSNTs loading were 17 dB and 43 dB, respectively. When the thickness of the nanocomposite increased to 10 mm, the STL value increased to 57.9 dB. The improved sound insulation performances of nanocomposites have been attributed to the unique hollow structure of the hollow silica nanotubes. The mechanical properties and the thermal stability of the nanocomposites were also improved by adding HSNTs into the epoxy matrix.

Deep eutectic solvents for green and efficient iron-mediated ligand-free atom transfer radical polymerization

Co-reporter:Jirong Wang;Jianyu Han;Mohd Yusuf Khan;Dan He;Haiyan Peng;Dianyu Chen;Xiaolin Xie

Polymer Chemistry (2010-Present) 2017 vol. 8(Issue 10) pp:1616-1627

Publication Date(Web):2017/03/07

DOI:10.1039/C6PY02066F

A variety of deep eutectic solvents (DESs) were used as novel, green, and intriguing additives for atom transfer radical polymerization (ATRP) of methyl methacrylate with FeBr2 in the absence of any additional ligands. The polymerization processes had a well controlled capability for producing well-defined polymers with predictable molecular weights as well as narrow molecular weight distributions, and the living feature was further confirmed by chain extension experiments. Relative research on species, dosage, and hydrogen bonding interaction between the components of the DESs together with the solubility of the catalyst have been discussed in detail with the help of NMR spectra and cyclic voltammograms. This DESs-tuned ATRP provides us with the unique opportunity to utilize environmentally friendly media and drastically reduce the high costs of common ligands.

Solid polymer electrolyte based on ionic bond or covalent bond functionalized silica nanoparticles

Co-reporter:Ji Hu;Wanhui Wang;Ronghua Yu;Mengke Guo;Chengen He;Xiaolin Xie;Haiyan Peng

RSC Advances (2011-Present) 2017 vol. 7(Issue 87) pp:54986-54994

Publication Date(Web):2017/12/01

DOI:10.1039/C7RA08471D

Although various types of nanoparticle have been ubiquitously employed as additives to promote the practical performances of composite polymer electrolytes (CPEs) in lithium-ion batteries, the influence of the type of chemical bond between the core and canopy of the modified nanoparticle on the properties of CPEs has rarely been investigated. Herein, two types of nanoparticle additive, namely, ionic bond modified nanoparticles (IBNs) and covalent bond modified nanoparticles (CBNs), were prepared conveniently based on nanosilica with different particle sizes in order to optimize the overall performance of the electrolyte. Furthermore, the CPEs were fabricated by doping IBNs or CBNs as well as lithium salts within a poly(ethylene oxide) matrix and their electrochemical properties were investigated. The dramatic enhancement of the ionic conductivity of the CPEs resulted from the addition of fillers into the system, and the improvement became more significant when the fillers were IBNs that used the smaller silica nanoparticle as the core segment, due to the increased chain mobility, as estimated by the smaller Tg value. Moreover, a broad electrochemical stability window was obtained in the presence of IBNs, and the lithium-ion transference number of the system containing lithium bis(trifluoromethanesulfonimide), which has large anions in the structure, was almost two times higher than the CPEs using lithium perchlorate as the lithium source. Therefore, the synergistic effects of the filler structures and the electrolyte compositions are the key factors to improve the electrochemical performances of CPEs.

Comb-like solid polymer electrolyte based on polyethylene glycol-grafted sulfonated polyether ether ketone

Co-reporter:Mengke Guo, Menglan Zhang, Dan He, Ji Hu, Xiaoen Wang, Chunli Gong, Xiaolin Xie, Zhigang Xue

Electrochimica Acta 2017 Volume 255(Volume 255) pp:

Publication Date(Web):20 November 2017

DOI:10.1016/j.electacta.2017.10.033

Solid polymer electrolytes based on a novel comb-like copolymer, polyethylene glycol-grafted sulfonated polyether ether ketone (SPEEK-g-PEG), was designed and synthesized through the reaction between partially hydroxyl-functionalized sulfonated polyether ether ketone (SPEEK) and epoxy-functionalized PEG. The resulting SPEEK-g-PEG was fully characterized by FTIR, 1H NMR, TGA, and DSC. All data proved the successful grafting of PEG onto the SPEEK main chain. The resulting comb-like structure effectively inhibited the crystallization of PEG. After doping with a lithium salt, the obtained SPEEK-g-PEG polymer electrolyte membrane showed an improved ionic conductivity. The effects of chain length and PEG grafting ratio on the ionic conductivity of SPEEK-g-PEG were also investigated by electrochemical impedance spectroscopy (EIS). Moreover, the effect of this comb-like structure on increasing the ionic conductivity is higher than that of SPEEK/PEG blends, making these comb-like SPEEK-g-PEG copolymers attractive for an application in LIBs.

Advanced carbon materials/olivine LiFePO4 composites cathode for lithium ion batteries

Co-reporter:Chunli Gong, Zhigang Xue, Sheng Wen, Yunsheng Ye, Xiaolin Xie

Journal of Power Sources 2016 Volume 318() pp:93-112

Publication Date(Web):30 June 2016

DOI:10.1016/j.jpowsour.2016.04.008

•Reviews applications of advanced carbon materials/LiFePO4 cathode.•Discusses preparation strategies of LiFePO4 composites cathode.•Analyzes influence factors of electrochemical performances.In the past two decades, LiFePO4 has undoubtly become a competitive candidate for the cathode material of the next-generation LIBs due to its abundant resources, low toxicity and excellent thermal stability, etc. However, the poor electronic conductivity as well as low lithium ion diffusion rate are the two major drawbacks for the commercial applications of LiFePO4 especially in the power energy field. The introduction of highly graphitized advanced carbon materials, which also possess high electronic conductivity, superior specific surface area and excellent structural stability, into LiFePO4 offers a better way to resolve the issue of limited rate performance caused by the two obstacles when compared with traditional carbon materials. In this review, we focus on advanced carbon materials such as one-dimensional (1D) carbon (carbon nanotubes and carbon fibers), two-dimensional (2D) carbon (graphene, graphene oxide and reduced graphene oxide) and three-dimensional (3D) carbon (carbon nanotubes array and 3D graphene skeleton), modified LiFePO4 for high power lithium ion batteries. The preparation strategies, structure, and electrochemical performance of advanced carbon/LiFePO4 composite are summarized and discussed in detail. The problems encountered in its application and the future development of this composite are also discussed.This article reviews the advanced carbon materials/olivine LiFePO4 composite cathodes for lithium ion batteries.

Structure, rheological, thermal conductive and electrical insulating properties of high-performance hybrid epoxy/nanosilica/AgNWs nanocomposites

Co-reporter:Chao Chen, Hongjian Wang, Yang Xue, Zhigang Xue, Hongyuan Liu, Xiaolin Xie, Yiu-Wing Mai

Composites Science and Technology 2016 Volume 128() pp:207-214

Publication Date(Web):18 May 2016

DOI:10.1016/j.compscitech.2016.04.005

A facile and effective approach by incorporating silica nanoparticles (SNPs) to fabricate high performance epoxy-based electronic packaging materials which are both thermally conductive and electrically insulating was presented. Because of the strong interaction between SNPs and silver nanowires (AgNWs), uniformly dispersed SNPs-modified epoxy was employed to promote the dispersion of AgNWs in epoxy matrix. Further, the enhanced modulus of epoxy matrix by the incorporation of SNPs effectively alleviates the modulus mismatch between stiff AgNWs and epoxy matrix. Compared with epoxy/AgNWs composites without SNPs, the resulting hybrid materials, that is, epoxy/SNP/AgNWs, showed distinct improvements in thermal conductivity without degrading their mechanical properties. Also, the SNPs were absorbed onto the surface of AgNWs forming an electrical insulation layer to disrupt the electron flows between adjacent AgNWs, hence retaining the electrical insulation of epoxy matrix. Finally, this new fabrication method is easily scalable owing to its simple procedure and use of commercial well-dispersed SNPs-modified epoxies.

Electric-Field-Assisted Assembly of Polymer-Tethered Gold Nanorods in Cylindrical Nanopores

Co-reporter:Ke Wang, Seon-Mi Jin, Jiangping Xu, Ruijing Liang, Khurram Shezad, Zhigang Xue, Xiaolin Xie, Eunji Lee, and Jintao Zhu

ACS Nano 2016 Volume 10(Issue 5) pp:4954

Publication Date(Web):April 7, 2016

DOI:10.1021/acsnano.6b00487

In this report, we demonstrate the confined assembly of polymer-tethered gold nanorods in anodic aluminum oxide (AAO) channels with the assistance of electric field (EF). Various interesting hybrid assemblies, such as single-, double-, triple-, or quadruple-helix, linear, and hexagonally packed structures are obtained by adjusting pore size in AAO channels, ligand length, and EF orientation. Correspondingly, surface plasmonic property of the assemblies can thus be tuned. This strategy, by coupling of external-field and cylindrically confined assembly, is believed to be a promising approach for generating ordered hybrid assemblies with hierarchical structures, which may find potential applications in photoelectric devices, biosensors, and data storage devices.Keywords: confined assembly; cylindrical confinement; electric field; gold nanorods; helix structure

Ionic polymer–metal composite actuators obtained from sulfonated poly(ether ether sulfone) ion-exchange membranes

Co-reporter:Zhigang Xue, Yongjun Tang, Xiaoling Duan, Yunsheng Ye, Xiaolin Xie, Xingping Zhou

Composites Part A: Applied Science and Manufacturing 2016 Volume 81() pp:13-21

Publication Date(Web):February 2016

DOI:10.1016/j.compositesa.2015.11.007

The cost-effective and high-performance ionic polymer–metal composites (IPMC) were designed and prepared from ion-exchange membranes based on sulfonated poly(ether ether sulfone) (SPEES) with different degrees of sulfonation (DS). The precursor of SPEES, namely PEES, is commercially available and industrial grade. Moreover, the PEES can be transformed easily into ion-conductive SPEES through a simple sulfonation reaction. The ion exchange capacity (IEC) and water uptake (WU) of SPEES membranes increase with increasing their DS, and the proton conductivities of these hydrated SPEES membranes are subsequently enhanced. Compared with the commercial Nafion ion-exchange membrane, the SPEES membranes have higher IEC and WU. The IPMC actuators made of the SPEES membranes show the large bending strain and fast response under electric stimulation. The SPEES membrane with the highest DS (SPEES4) shows the best performance of IPMC actuators. The electromechanical behaviors of these IPMC actuators indicate that the SPEES is a candidate to substitute Nafion.

Synthesis of poly(n-butyl acrylate) homopolymer and poly(styrene-b-n-butyl acrylate-b-styrene) triblock copolymer via AGET emulsion ATRP using a cationic surfactant

Co-reporter:Zhigang Xue;Zhen Wang;Dan He;Xingping Zhou;Xiaolin Xie

Journal of Polymer Science Part A: Polymer Chemistry 2016 Volume 54( Issue 5) pp:611-620

Publication Date(Web):

DOI:10.1002/pola.27809

ABSTRACT

Cationic emulsions of triblock copolymer particles comprising a poly(n-butyl acrylate) (PⁿBA) central block and polystyrene (PS) outer blocks were synthesized by activator generated by electron transfer (AGET) atom transfer radical polymerization (ATRP). Difunctional ATRP initiator, ethylene bis(2-bromoisobutyrate) (EBBiB), was used as initiator to synthesize the ABA type poly(styrene-b-n-butyl acrylate-b-styrene) (PS-PⁿBA-PS) triblock copolymer. The effects of ligand and cationic surfactant on polymerizations were also discussed. Gel permeation chromatography (GPC) was used to characterize the molecular weight (M_n) and molecular weight distribution (MWD) of the resultant triblock copolymers. Particle size and particle size distribution of resulted latexes were characterized by dynamic light scattering (DLS). The resultant latexes showed good colloidal stability with average particle size around 100–300 nm in diameter. Glass transition temperature (T_g) of copolymers was studied by differential scanning calorimetry (DSC). © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016, 54, 611–620

Ionic polymer–metal composite actuator based on sulfonated poly(ether ether ketone) with different degrees of sulfonation

Co-reporter:Yongjun Tang, Zhigang Xue, Xiaolin Xie, Xingping Zhou

Sensors and Actuators A: Physical 2016 Volume 238() pp:167-176

Publication Date(Web):1 February 2016

DOI:10.1016/j.sna.2015.12.015

•We synthesized SPEEK-based IPMC membranes.•IEC was one of crucial factors to determine the performance of IPMC actuators.•SPEEK3-based IPMC showed the best actuation performance.The sulfonated poly(ether ether ketone) (SPEEK) membranes with different degrees of sulfonation (DS) were prepared for fabricating high-performance ionic polymer–metal composite (IPMC) actuators. The ion exchange capacity (IEC), water uptake and ion conductivity of SPEEK membranes increase accordingly with the increase of the DS of SPEEK membranes. The SPEEK membranes show much higher IEC and water uptake than those of the traditional Nafion membrane. The SPEEK actuator with the highest DS, namely SPEEK3 actuator, shows the best bending deformation under the electric stimulus. Compared with Nafion system, the SPEEK3 actuator increases at maximum blending strain under sinusoidal voltage of 3 V at 1 Hz. These greatly enhanced actuation performance indicates the SPEEK is a candidate to substitute Nafion in the field of IPMC actuator.

Poly(ethylene oxide)-based electrolytes for lithium-ion batteries

Co-reporter:Zhigang Xue, Dan He and Xiaolin Xie

Journal of Materials Chemistry A 2015 vol. 3(Issue 38) pp:19218-19253

Publication Date(Web):20 Jul 2015

DOI:10.1039/C5TA03471J

Poly(ethylene oxide) (PEO) based materials are widely considered as promising candidates of polymer hosts in solid-state electrolytes for high energy density secondary lithium batteries. They have several specific advantages such as high safety, easy fabrication, low cost, high energy density, good electrochemical stability, and excellent compatibility with lithium salts. However, the typical linear PEO does not meet the production requirement because of its insufficient ionic conductivity due to the high crystallinity of the ethylene oxide (EO) chains, which can restrain the ionic transition due to the stiff structure especially at low temperature. Scientists have explored different approaches to reduce the crystallinity and hence to improve the ionic conductivity of PEO-based electrolytes, including blending, modifying and making PEO derivatives. This review is focused on surveying the recent developments and issues concerning PEO-based electrolytes for lithium-ion batteries.

Iron-catalyzed atom transfer radical polymerization

Co-reporter:Zhigang Xue, Dan He and Xiaolin Xie

Polymer Chemistry 2015 vol. 6(Issue 10) pp:1660-1687

Publication Date(Web):23 Dec 2014

DOI:10.1039/C4PY01457J

In the last two decades, metal-catalyzed controlled radical polymerization (CRP), or atom transfer radical polymerization (ATRP) has become a ubiquitous tool for the facile synthesis of a wide range of materials with specific macromolecular architectures. The complex plays an important role in ATRP, and for this purpose researchers put a great deal of effort on studying the effect of various complexes on polymerization. However, one of the disadvantages of a copper complex, the most extensively studied catalyst system in ATRP, is the contamination of polymers resulting from a high concentration of stable catalyst. Efficiently and economically removing the catalyst from the resultant polymers will provide a wide variety of new functional polymers for specialty applications, especially for large-scale industrial manufacture. Iron-based catalysts have attracted particular attention because of their low toxicity, low cost, abundance, and environmental friendliness, and thus many iron catalysts have been designed for ATRP. This article reviews the preparation of polymers using iron-catalyzed atom transfer radical polymerization, and is organized according to: (a) mechanistic considerations; (b) iron complexes and ligand types.

Living radical polymerization of vinyl acetate mediated by iron(III) acetylacetonate in the presence of a reducing agent

Co-reporter:Jirong Wang, Jun Zhou, Hussameddin S. E. M. Sharif, Dan He, Yun Sheng Ye, Zhigang Xue and Xiaolin Xie

RSC Advances 2015 vol. 5(Issue 117) pp:96345-96352

Publication Date(Web):05 Nov 2015

DOI:10.1039/C5RA18825C

Iron(III) acetylacetonate (Fe(acac)3) was employed to mediate the controlled radical polymerization of vinyl acetate (VAc) in the presence of a reducing agent (RA). Polymerizations were conducted with a molar ratio of [VAc]0/[initiator]0/[Fe(acac)3]0/[RA]0/[ligand]0 = 500:0.8:1:2:3 and a volume ratio of VAc/solvent = 1 at 70 °C to investigate the effects of initiator, solvent, and reducing agent on the polymerization reaction. The kinetic plots of VAc polymerizations were linear, and the molecular weights (Mn) increased proportionately with monomer conversions.

Amide group-containing polar solvents as ligands for iron-catalyzed atom transfer radical polymerization of methyl methacrylate

Co-reporter:Jun Zhou, Jirong Wang, Jianyu Han, Dan He, Danfeng Yang, Zhigang Xue, Yonggui Liao and Xiaolin Xie

RSC Advances 2015 vol. 5(Issue 54) pp:43724-43732

Publication Date(Web):17 Apr 2015

DOI:10.1039/C5RA05460E

A series of amide group-containing polar solvents, formamide (Fo), N-methylformamide (MFo), N,N-dimethylformamide (DMF), acetamide (Ac), N-methylacetamide (MAc), N,N-dimethylacetamide (DMAc), urea, tetramethyl urea (TMU), 2-pyrrolidone (2-Py), N-methyl-2-pyrrolidone (NMP) and 5-methyl-2-pyrrolidone (MPy), were used as both solvents and ligands for iron(II)-catalyzed atom transfer radical polymerizations (ATRPs) of methyl methacrylate (MMA), with ethyl 2-bromo-2-phenylacetate (EBPA) as the initiator. Most of the polymerizations were well-controlled in character, and the structures of the polar solvents greatly affected the catalytic activity. In addition, the living features of the systems remained in the presence of limited amounts of polar solvents. Some of the polar solvents (MFo, TMU and 2-Py) were also employed for iron(III)-catalyzed activators generated by electron transfer (AGET) ATRPs of MMA, and the results were as good as those of the ATRPs.

PANI–PEG copolymer modified LiFePO4 as a cathode material for high-performance lithium ion batteries

Co-reporter:Chunli Gong, Fangli Deng, Chi-Pong Tsui, Zhigang Xue, Yun Sheng Ye, Chak-Yin Tang, Xingping Zhou and Xiaolin Xie

Journal of Materials Chemistry A 2014 vol. 2(Issue 45) pp:19315-19323

Publication Date(Web):22 Sep 2014

DOI:10.1039/C4TA04089A

The poor electronic conductivity and low lithium ion diffusion rate of a LiFePO4 cathode material are the two major obstacles for its commercial applications in the power lithium ion batteries. This article utilized an electroactive and ion conductive copolymer, polyaniline–poly(ethylene glycol) (PANI–PEG), to modify carbon-LiFePO4 (cLFP) by a facile in situ chemical copolymerization method. The structure and morphology of the cLFP/PANI–PEG composite were confirmed by Fourier transform infrared spectroscopy (FTIR), X-ray diffractometry (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Compared with a cLFP/PANI composite, the cLFP/PANI–PEG composite exhibited a more uniform and full polymer coating layer. Furthermore, this cLFP/PANI–PEG cathode material exhibits excellent cyclic stability (95.7% capacity retention after 100 cycles at 0.1 C) and high rate capability (125.3 mA h g−1 at 5 C) as the PANI–PEG copolymer coating layer facilitated electron and ion transport within the electrode. Electrochemical impedance spectroscopy (EIS) proved that the lithium ion diffusion in the cLFP/PANI–PEG composite was increased significantly by one order of magnitude compared with cLFP, indicating its possibility to be served as a cathode material for high-performance lithium ion batteries.

Poly(ethylene glycol) grafted multi-walled carbon nanotubes/LiFePO4 composite cathodes for lithium ion batteries

Co-reporter:Chunli Gong, Zhigang Xue, Xiaoen Wang, Xing-Ping Zhou, Xiao-Lin Xie, Yiu-Wing Mai

Journal of Power Sources 2014 Volume 246() pp:260-268

Publication Date(Web):15 January 2014

DOI:10.1016/j.jpowsour.2013.07.091

•We report a new conductive agent to increase the electrochemical property of LiFePO4.•PEG layer improves the dispersion of MWCNTs and facilitates Li+ diffusion in the cathode.•Highly dispersed MWCNTs increase the thermal conductivity of the cathode.Poly(ethylene glycol) (PEG) grafted multi-walled carbon nanotubes (MWCNTs-g-PEG or MP) were synthesized and used to modify LiFePO4 as cathodes for lithium-ion batteries (LIBs). The effects of different molecular weights of PEG grafted on MWCNTs and different mass fractions of MP on the properties of LiFePO4/MP composite cathodes were evaluated by their morphology, charge–discharge tests, electrochemical impedance spectroscopy, electrical and thermal conductivities. Their electrochemical behaviors at ambient temperature and low temperature, high rate capability and cycling performance were observed in the presence of the MP additives. The lithium ions diffusion in the LiFePO4/MP composite electrodes was almost 2 orders of magnitude higher than that in the LiFePO4/acetylene black (AB) electrode when the conductive additive content was 5 wt.%. Thermal studies of LiFePO4/MP were also examined by the heat-pole method, which showed higher thermal conductivity of the cathode in cases of MP being incorporated into LiFePO4 particles than LiFePO4 cathodes with AB or MWCNTs additives. These results suggest that MP is a promising conductive additive to increase the electrochemical performances, thermal transport and safety of LiFePO4 cathodes for LIBs.

The enhanced actuation response of an ionic polymer–metal composite actuator based on sulfonated polyphenylsulfone

Co-reporter:Yongjun Tang, Chao Chen, Yun Sheng Ye, Zhigang Xue, Xingping Zhou and Xiaolin Xie

Polymer Chemistry 2014 vol. 5(Issue 20) pp:6097-6107

Publication Date(Web):07 Jul 2014

DOI:10.1039/C4PY00663A

The sulfonated polyphenylsulfone (SPPSU) membranes with different degrees of sulfonation (DS) were prepared for fabricating low-cost and high-performance ionic polymer–metal composite (IPMC) actuators. The properties of SPPSU ion exchange membranes and the electromechanical performance of resulting SPPSU actuators can be manipulated by controlling their DS. As the DS of SPPSU membranes increases, their ion exchange capacity (IEC), water uptake and ion conductivity increase accordingly, whereas the hydrated mechanical properties (strength and modulus) decrease. The SPPSU membrane with the highest DS (SPPSU4) shows much higher IEC and water uptake, and slightly lower ion conductivity than those of the traditional Nafion membrane. Among the prepared IPMC actuators, the SPPSU4 actuator performs the best in the bending deformation under the electric stimulus. The maximum bending strain (MBS) of the SPPSU4 actuator is comparable to that of the Nafion actuator coupled with several times faster bending response at 3 V DC voltage. Compared with the Nafion system, the SPPSU4 actuator increases approximately twice at MBS under a sinusoidal voltage of 3 V at 1 Hz. This greatly enhanced actuation performance indicates that the SPPSU is a candidate to substitute Nafion in the field of IPMC actuators.

High-performance epoxy/silica coated silver nanowire composites as underfill material for electronic packaging

Co-reporter:Chao Chen, Yongjun Tang, Yun Sheng Ye, Zhigang Xue, Yang Xue, Xiaolin Xie, Yiu-Wing Mai

Composites Science and Technology 2014 Volume 105() pp:80-85

Publication Date(Web):10 December 2014

DOI:10.1016/j.compscitech.2014.10.002

Silver nanowires (AgNWs), as one-dimensional nanostructured materials, possess high aspect ratio and intrinsically high thermal conductivity. However, AgNWs are difficult to disperse homogeneously in epoxy resin, and their high electrical conductivity also limits their applications for electronic packaging. Herein, silica-coated silver nanowires (AgNWs@SiO2) were synthesized by a flexible sol–gel method and then incorporated into epoxy. The less stiff silica intermediate nanolayer on AgNWs not only alleviated the mismatch between AgNWs and epoxy, but also enhanced their interfacial interaction. Hence, the thermal conductivity of an epoxy/AgNWs@SiO2 composite with 4 vol.% filler loading was increased to 1.03 W/mK from 0.19 W/mK of neat epoxy compared to 0.57 W/mK of an epoxy/AgNWs composite with identical nanowire loading. Simultaneously, the insulating silica nanolayer effectively avoided formation of an electrically conductive network of AgNWs in epoxy, leading to high electrical insulation of the composite. AgNWs@SiO2 nanowires with core–shell structure also improved the dielectric properties of epoxy. In addition, these composites possessed a viscosity suitable for the underfill process in electronic packaging.

Iron-mediated AGET ATRP of methyl methacrylate in the presence of polar solvents as ligands

Co-reporter:Danfeng Yang;Dan He;Yonggui Liao;Xingping Zhou;Xiaolin Xie

Journal of Polymer Science Part A: Polymer Chemistry 2014 Volume 52( Issue 7) pp:1020-1027

Publication Date(Web):

DOI:10.1002/pola.27083

ABSTRACT

The polar solvents, N-methylpyrrolidone (NMP), N,N-dimethylformamide (DMF), and acetonitrile (CH₃CN) were used as ligands for iron(III)-mediated activators generated by electron transfer atom transfer radical polymerizations (AGET ATRPs) of methyl methacrylate (MMA) with various initiators and reducing agents. Polymerizations were conducted with a molar ratio of [MMA]₀/[initiator]₀/[FeBr₃]₀/[reducing agent]₀ = 100:1:1:0.5 and a volume ratio of MMA/solvent = 2:1 at 60 °C to investigate the effects of initiator, solvent and reducing agent, and most of the systems showed the typical features of “living”/controlled radical polymerization. In order to get a deeper understanding of the mechanism, the amount of the reducing agent was changed to study the polymerization behavior. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014, 52, 1020–1027