Significance of the Dispersion Stability of Carbon Nanotubes on the Thermal Conductivity of Nylon 610 Nanocomposite

Herein, the effect of the dispersion uniformity of multi-wall carbon nanotubes (MWNTs) on the thermal conductivity of nylon 610/MWNTs nanocomposite was investigated. Compared to raw MWNTs, the carboxylated MWNTs (MWNT-COOH) were well dispersed in aqueous hexamethylenediamine solution and the dispersion stability was further improved by the presence of poly(vinyl alcohol). By means of interfacial polymerization between the aqueous hexamethylenediamine solution containing the MWNTs and a sebacoyl chloride phase, nylon 610/MWNT composites were prepared. It was found that the stable dispersion state of MWNTs in aqueous solutions greatly improved the thermal conductivity of the ultimate nanocomposites. It is noted that the thermal conductivity of nylon 610/MWNT-COOH/PVA nanocomposite was 135% higher than that of nylon 610/raw MWNTs for the same 0.1 wt% content of MWNTs.     

Poly(aniline-2-sulfonic acid) modified multiwalled carbon nanotubes with good aqueous dispersibility

Poly(aniline-2-sulfonic acid) (PASA)-modified multiwalled carbon nanotubes (MWNTs) were prepared by in situ oxidative polymerization. HRTEM images show that the PASA-modified MWNTs (PASANTs) are core (MWNT)-shell (PASA) tubular structures with a shell thickness of several nanometers. The strong interaction between the surface of the MWNTs and the conjugated structure of the PASA shell layer was proven by FTIR spectra. It was found that the aqueous dispersibility and dispersion stability of PASANTs were significantly improved compared to those of the raw MWNTs. Furthermore, when the PASA content is greater than 30 wt%, no precipitation is found for the dispersions of modified MWNTs after sedimentation for 500 h, exhibiting an excellent stability. The electrical conductivity of these modified MWNTs is 2-5 times higher than that of raw MWNTs and is 10(3) times higher than that of PASA.     

Grafting of polyaniline onto the surface of 4‐aminobenzoyl‐functionalized multiwalled carbon nanotube and its electrochemical properties

Polyaniline (PANi)‐grafted multiwalled carbon nanotube (MWNT) composite is prepared by a two‐step reaction sequence. MWNT is first functionalized with 4‐aminobenzoic acid in polyphosphoric acid/phosphorous pentoxide as a “direct” Friedel‐Crafts acylation reaction medium. The resultant 4‐aminobenzoyl‐functionalized MWNT is then treated with aniline using ammonium persulfate/aqueous hydrochloric acid to promote a chemical oxidative polymerization, leading to PANi‐grafted MWNT composite. The resultant composite is characterized by elemental analysis, Fourier‐transform infrared spectroscopy, wide‐angle X‐ray diffraction, scanning electron microscopy, transmission electron microscopy, thermogravimetric analysis, UV–vis absorption spectroscopy, fluorescence spectroscopy, cyclic voltammetry, and electrical conductivity measurement. The thermooxidative stability and electrical conductivity of PANi‐grafted MWNT composite are improved compared to those of PANi. Specifically, the electrical conductivity of PANi‐grafted MWNT is improved 10–900 times depending upon the level of doping. The capacitance of the composite is also greatly enhanced. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 3103–3112, 2010     

新型聚N，N-二甲基苯胺/多壁碳纳米管修饰电极的制备、表征与应用

采用多壁碳纳米管(MWNT)改性聚N,N-二甲基苯胺(PDMA)膜,制备了新型复合膜修饰玻碳电极,并用SEM、电化学方法对修饰电极进行表征。 结果表明,无论MWNT是以掺杂还是先滴涂MWNT再聚合DMA多层修饰方式,均会改变PDMA膜的形貌和电化学性能。 复合膜修饰电极比单一PDMA膜修饰电极大幅度提高了比表面积和电活化面积,同时使PDMA和MWNT更好地协同发挥其优良的电化学特性。 实验结果表明,层层修饰制备的聚N,N-二甲基苯胺/多壁碳纳米管复合膜修饰电极对香草醛的电化学响应远大于基体电极和其它方法制备的修饰电极,电催化作用显著提高,其过电位降低了148 mV,氧化峰电流约增加了6倍;其电极反应是吸附控制的不可逆氧化过程,转移电子数n为2,质子数m为1,传递系数α为0.4062,吸附量为Γ=3.527×10-9 mol/cm2;检出下限为8.0×10-7 mol/L,样品平均回收率为99.87%。     

聚乙烯醇/聚乙烯吡咯烷酮碱性复合膜的制备及其性能

通过在不同浓度KOH溶液中进行掺杂,制备出了聚乙烯醇/聚乙烯吡咯烷酮(PVA/PVP)碱性聚合物电解质膜.详尽考察了膜的组成、微观结构、热稳定性、离子电导率和甲醇吸收率.结果表明,PVA与PVP两者具有较好的相容性,当m(PVA)∶m(PVP)=1∶0.5时,膜断面致密、均匀,未发生大尺度相分离.PVP的混入可以极大提高复合膜的电导率和热稳定性.当m(PVA)∶m(PVP)=1∶1时,复合膜的电导率可达2.01×10-3 S.cm-1.PVA/PVP/KOH膜的甲醇吸收率随温度的升高没有明显变化,100℃时其甲醇吸收率仅为同条件下Nafion 115膜的1/4.这表明该复合膜有望作为一种新型的碱性直接甲醇燃料电池用固体电解质膜且可提高膜的使用温度.     

Properties of Poly(Vinyl Alcohol)‐Based Composite Membranes for Direct Methanol Fuel Cell Applications

The feasibility of poly(vinyl alcohol)(PVA)/sulfosuccinic acid(SSA)/heteropolyacid (HPA) composite membranes was investigated to apply for direct methanol fuel cells (DMFC). The composite membranes were prepared by the solution casting method and their properties were examined. The FTIR spectra showed that the Keggin unit of HPA was preserved in the composite membranes and that specific interactions were involved between PVA and HPA. The composite membranes showed uniform distribution of PWA particles in the PVA/SSA/PWA composite membranes by FE‐SEM. The HPA bleeding out was observed to decrease with increasing HPA concentration. The proton conductivity of PVA/SSA/HPA composite membranes improved at low HPA concentration (5‐10 wt.%), while those properties decreased as HPA concentration increased over 10 wt.%.     

Novel Poly(vinyl alcohol)/Chitosan/Modified Graphene Oxide Biocomposite for Wound Dressing Application

Rapid absorption of wound exudate and prevention of wound infection are prerequisites for wound dressing to accelerate wound healing. In this study, a novel kind of promising wound dressing is developed by incorporating polyhexamethylene guanidine (PHMG)‐modified graphene oxide (mGO) into the poly(vinyl alcohol)/chitosan (PVA/CS) matrix, conferring the dressing the required mechanical properties, higher water vapor transmission rate (WVTR), less swelling time, improved antibacterial activity, and more cell proliferation compared to the PVA/CS film crosslinked by genipin. In vivo experiments indicate that the PVA/CS/mGO composite film can accelerate wound healing via enhancement of the re‐epithelialization. PVA/CS/mGO composite film with 0.5 wt% mGO sheets displays the best wound healing properties, as manifested by the 50% higher antibacterial rate compared to GO and the wound healing rate of the mouse using this dressing is about 41% faster than the control group and 31% faster than the pure PVA/CS dressing. The underlying mechanism of the accelerated wound healing properties may be a result of the improved antibacterial ability to eradicate pathogenic bacteria on the wound area and maintain an appropriate moist aseptic wound healing environment to accelerate re‐epithelialization. These findings suggest that this novel composite PVA/CS/mGO film may have promising applications in wound dressing.     

高稳定性化学交联聚乙烯醇/聚乙烯吡咯烷酮碱性固体电解质膜

碱性固体电解质膜的稳定性是影响其在电化学领域应用的一个重要因素.本文在前期研究工作的基础上,通过直接共混和化学交联修饰制备出了聚乙烯醇/聚乙烯吡咯烷酮(PVA/PVP)碱性聚合物电解质膜.采用傅里叶变换红外(FTIR)光谱、热重分析(TGA)、扫描电镜(SEM)和交流阻抗等方法详细考察了复合膜的分子结构、热稳定性、化学稳定性、氧化稳定性和尺寸稳定性.红外光谱结果表明,PVP成功地混入聚合物基体中,在1672cm-1处表现出来自于PVP第I带C襒O的强吸收峰.TGA结果表明,提高掺杂的KOH溶液浓度对PVA/PVP碱性膜的热稳定性没有明显影响.SEM分析结果表明,复合膜经高温、高浓度碱(80℃,10mol·L-1)处理后,其断面结构仍致密均匀,未出现类似小孔等膜降解情况,此时膜电导率(1.58×10-3S·cm-1)相比室温相同碱液时提高91.5%,表明PVA/PVP膜具有很好的耐碱化学稳定性.同时,PVA/PVP碱性膜表现出良好的抗氧化性,在60℃的3%和10%H2O2溶液中处理均没有观察到明显的质量损失,150h后仍能保持原膜质量的89%和85%.此外,由于膜内形成致密的内互交联网络结构,复合膜在水中800h之后也表现出很好的同向性和电导率稳定性.     

Morphology,electrical resistance,electromagnetic interference shielding and mechanical properties of functionalized MWNT and poly(urea urethane) nanocomposites

The functionalized multi‐walled carbon nanotubes (MWNT) had been prepared by free radical reaction with vinyltriethoxysilane. Polydimethylsiloxane (PDMS)‐based poly(urea urethane) (PUU) was also synthesized. PUU was further end‐capped with aminopropyltriethoxysilane (A‐silane), or with phenyltrimethoxysilane (P‐silane). Fourier transform infrared (FTIR), Raman spectra and thermogravimetric analysis (TGA) confirmed the functionalization of MWNT. The M_n and M_w of PUU were 85,123 and 235,876 g/mol, respectively. Both A‐silane end‐capped PUU and P‐silane end‐capped PUU showed improved dispersion of MWNT compared with that of PUU and MWNT. Moreover, the reduced discrepancy of surface electrical resistance of the two sides of the MWNT/PUU nanocomposite film was found due to the homogeneous dispersion of MWNT. The microwave absorption and tensile strength of MWNT/PUU were also improved by the well dispersion of MWNT in PUU matrix. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 1096–1105, 2006     

Porous and electrically conductive polypyrrole-poly(vinyl alcohol) composite and its applications as a biomaterial

Bulk modification of polypyrrole (PPY) with poly(vinyl alcohol) (PVA) was carried out by the electropolymerization of pyrrole in the presence of PVA in the reaction solution, with tetraethylammonium perchlorate (TEAP) as the electrolyte. The surface morphology of the as-synthesized PPY-TEAP-PVA film was investigated using scanning electron microscopy, and the film was further characterized using X-ray photoelectron spectroscopy, electrical conductivity, the water contact angle, and BET surface area measurements. The PPY-TEAP-PVA composite is electrically conductive, hydrophilic, and microporous with a high surface area. Its potential as a biomaterial was investigated with respect to its blood compatibility and function as a substrate for biosensor fabrication and cell culture. The presence of PVA in the film attenuates blood protein adsorption, and the porous nature of the PPY-TEAP-PVA film results in a 10-fold increase in the amount of glucose oxidase covalently immobilized on the film over that on a nonporous PPY film. PC12 cell attachment and growth on the PPY-TEAP-PVA film was also shown to be enhanced compared with that on tissue culture polystyrene. The attached cells proliferated and formed a monolayer on the film surface after 48 h of seeding.     

Dramatic enhancement of carbon nanotube dispersion in polyimide composites by a two‐step amino functionalization approach

Amino modified multiwall carbon nanotubes (MWNTs) are prepared, respectively, by two ways: the conventional one‐step method that directly treats acyl chloride functionalized MWNTs with 4, 4′‐diaminodiphenyl ether (ODA), giving the amino modified MWNT (Di‐MWNT), as well as an improved two‐step method in which acyl chloride functionalized MWNT react with mono‐Boc protected ODA first and then the Boc‐groups are deprotected to provide the amino modified MWNT (NH₂‐MWNT). Anhydride‐terminated polyimide (PI) composite films based on NH₂‐MWNT and Di‐MWNT are fabricated by solution blending and consequent planar casting. The exposed amino groups of NH₂‐MWNT create strong covalent bonds with the anhydride‐terminated polyamide acid in the course of N‐acylation and curing chemical reactions. Solubility examinations of nanotubes and morphologies of the composite films indicate that the dispersion of NH₂‐MWNT is significantly better than Di‐MWNT in PI matrix and NH₂‐MWNT can form connected network throughout the PI matrix which makes the NH₂‐MWNT/PI film presenting superior conductivity. Both morphologies and mechanical properties of the composites show that NH₂‐MWNT has stronger interfacial interaction with the PI matrix. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013 , 51, 3449–3457     

恒定磁场(0.4T)对聚苯胺微观取向结构的影响

在恒定磁场(0.4 T)条件下, 采用乳液聚合法合成了十二烷基苯磺酸掺杂聚苯胺(PAn), 并通过透射电子显微镜(TEM)、X射线衍射(XRD)、傅立叶红外光谱(FT-IR)、电导率、产物复合膜电阻率的各向异性, 以及产物间甲酚(m-cresol)溶液的电导率在外电场作用下变化的分析与表征, 系统研究了磁场对PAn的微观取向结构及其性能的影响. 实验结果表明, 与无磁场条件下制备的聚苯胺(PAn_-O)相比, 磁场条件下制备的聚苯胺(PAn_-M)具有更高的结晶度和明显的微观取向结构, 其微粒有序排列和堆砌成了许多具有一定长/径比的条状聚集体; PAn_-M/PVA(聚乙烯醇)复合膜经磁化成膜, 可以表现出明显的导电性能的各向异性; PAn_-M/m-cresol溶液的电导率, 在有、无外场(电场)作用下存在明显的突变. 分析认为: 由于磁场条件下制备的PAn粉末存在着微观取向和显著的抗磁磁化率的各向异性, 在外磁场作用下其堆砌方式会进一步演变成宏观的取向, 随之表现出物理性能上的各向异性.     

魔芋葡甘聚糖/聚乙烯醇纳米纤维膜及其释药行为研究

为了研制药物缓释效果优良的薄膜材料,利用静电纺丝设备研制不同比重的魔芋葡甘露聚糖/聚乙烯醇纳米纤维膜,并通过扫描电镜、傅里叶变换红外光谱和示差扫描量热法表征纳米纤维膜的结构和性能,结合体外实验和数学模型研究其缓释行为.结果显示当魔芋葡甘露聚糖含量占纳米纤维膜总质量约76%时,纳米纤维膜中微纤丝粗细最均匀且结点较少,纳米纤维膜中魔芋葡甘聚糖和聚乙烯醇之间存在明显的相互作用,含有5-氨基水杨酸的纳米纤维膜在pH=7.4 PBS磷酸盐缓冲液中25 h的累积释放量大约为45%,显示出良好的药物缓释效果,其缓释行为与Higuchi模型具有较高的拟合度.研究表明利用静电纺丝设备研制的魔芋葡甘聚糖/聚乙烯醇纳米纤维膜可以为药物缓释载体的开发提供理论依据.     

PVA-膨润土-KOH-H2O复合碱性聚合物电解质的制备与表征

以聚乙烯醇(PVA)与膨润土(bentonite)和氢氧化钾为原料, 采用溶液浇铸法制备了PVA-膨润土-KOH-H2O复合碱性聚合物电解质膜. 运用X衍射(XRD)、扫描电镜(SEM)和循环伏安(CV)等技术对复合膜进行了表征, 分析了膨润土对聚合物膜电导率的影响. 结果表明, 膨润土对电解质的导电性能具有双重作用: 一方面膨润土本身会阻塞PVA内部结构中的部分离子通道, 导致复合电解质的电导率降低; 另一方面, 膨润土有助于体系中KOH含量的增加, 同时PVA-膨润土相界面高导电性缺陷层的形成有助于体系电导率的提高. 当体系水的质量分数较低时, 复合电解质体系电导率存在极大值; 当w(H2O)为65%时, 则观察到电导率的线性增加趋势; 电解质最高室温电导率达0.110 S·cm-1. XRD图谱显示适当配比的复合膜中PVA呈无定形态; SEM结果证实了适当配比的复合膜中存在大量微米级孔径的微孔通道. 循环伏安曲线表明PVA-膨润土-KOH-H2O碱性聚合物电解质膜有约2.0 V的较宽电化学稳定窗口.     

聚苯胺／含联苯结构聚芳砜导电复合膜的研究

采用溶液共混法得到了聚苯胺／含联苯结构聚芳砜导电复合膜。该复合膜有良好的力学性能和导电性能，对其导电规律进行了探讨。热分析结果表明复合膜有良好的热稳定性，用扫描电镜观察了复合膜的微观形貌，表明ＰＡｎ与ＬＰＥＳ的共混相容性较好。     

Enhanced electrical conductivity in chemically modified carbon nanotube/methylvinyl silicone rubber nanocomposite

Chemically modified multiwalled carbon nanotubes/methlyvinyl silicone rubber (m-MWNT/VMQ) nanocomposites with relatively good dispersion of nanotubes were prepared by treating the surface of MWNT using γ-aminopropyltriethoxy silane (KH550). Significant enhanced electrical conductivity was discovered in the m-MWNT/VMQ nanocomposites. The results could be attributed a strong interaction between m-MWNT and VMQ which was from the chemically modification of the surface for MWNT. The electrical property was also discussed in order to understand the percolation and electrical transport mechanism. The m-MWNT/VMQ nanocomposites with high conductivity in this study are promising application as one of novel functional materials.     

Stabilization of electrospun poly(vinyl alcohol) nanofibrous mats in aqueous solutions

<正>The stability ofpoly(vinyl alcohol)(PVA) nanofibrous mats in water media was improved by post-electrospinning treatments.Bifunctional glutaraldehyde(GA) in methanol was used as a crosslinking agent to stabilize PVA nanofiber,but fiber twinning was observed frequently,and the highly porous structure of PVA nanofibrous mats was destroyed when the crosslinked fiber was soaked in water.To overcome this shortcoming,chitosan(CS) was introduced into the PVA spinning solution to prepare PVA/CS composite nanofibers.Their treatment in GA/methanol solution could retain the fiber morphology of PVA/CS nanofibers and porous structure of PVA/CS nanofibrous mats even if they were soaked in aqueous solutions for 1 month.Scanning electron microscopy(SEM),X-ray diffraction(XRD),thermal gravimetric analysis(TGA) and differential scanning calorimetry(DSC) were applied to characterize the physicochemical structure and thermal properties of PVA nanofibers.It was found that the water resistance of PVA nanofibrous mats was enhanced because of the improvement of the degree of crosslinking and crystallinity in the electrospun PVA fibers after soaking in GA/methanol solution.     

掺杂多壁碳纳米管改性聚溴甲酚绿膜修饰电极的制备、表征与应用研究

研究了掺杂多壁碳纳米管(MWNT)改性聚溴甲酚绿膜(PBG),以不同修饰方法制备了4种修饰电极,用扫描电镜、交流阻抗及循环伏安法等对电极进行表征。结果表明:4种修饰电极的电活化面积均得到明显提高,其中以层层修饰制备的聚溴甲酚绿膜/多壁碳纳米管复合膜(PBG/MWNT/GC)电极最能发挥MWNT和PBG的电活性。将电极用于8-羟基喹啉(8-HQ)电化学行为的研究,结果表明:4种修饰电极的伏安响应明显提高,且8-HQ在PBG/MWNT/GC上的氧化峰电位负移最多,峰电流最大,约为裸玻碳电极的4.5倍,电催化作用显著增强。8-HQ在PBG/MWNT/GC上电极反应的电子转移数和质子数均为1,是吸附控制的不可逆电氧化过程,氧化峰电流Ip与浓度c在4.0×10-6～3.5×10-4mol/L范围内呈良好的线性关系,r=-0.997 2,检出限(S/N=3)为1.96×10-8mol/L。PBG/MWNT/GC修饰电极可实现8-HQ的快捷、简便测定。     

聚苯胺／聚乙烯醇导电复合膜的制备及性质研究

用较简单的化学氧化现场吸附聚合法（ｉｎ－ｓｉｔｕｐｏｌｙｍｅｒｉｚａｔｉｏｎ）制得了聚苯胺（ＰＡｎ）／聚乙烯醇（ＰＶＡ）导电复合膜．该膜具有较好的导电性和机械性能；其电导率可达５．８ｓ／ｃｍ，拉伸强度达１３ＭＰａ，断裂伸长率为１１０％左右．本文讨论了制备的各种条件对复合膜导电性能及力学性能的影响、稳定性及电化学活性；并采用循环伏安曲线、扫描电镜（ＳＥＭ）、ＦＴＩＲ谱及元素分析对该复合膜的结构和性能进行了表征．     

Polypyrrole–polyvinyl alcohol stable nanodispersion: A prospective conducting black ink

Chemical polymerization of pyrrole within aqueous polyvinyl alcohol (PVA) solution gives rise to a nanodispersion with unique stability and monodispersity. The nanodispersion has shown uniform distribution of perfectly spherical ～110 nm polypyrrole particles (from transmission electron microscopy and dynamic light scattering) with high doping level (from UV‐Vis analysis) and sufficient electrical conductivity (10^?3 S/cm). The dispersion with optimum stability and conductivity was subjected to viscoelastic studies. The viscosity of the system was adjusted by dilution with water and shear thinning (under steady shear) was generally observed. Dynamic mechanical studies have shown that the dispersion behaves like a semidiluted polymeric solution that roughly follows the Zimm model of viscoelasticity. This behavior accounts for its unique stability and miscibility with water at any proportion without precipitation. On drying or leaving the sample for 7 days, Fe³⁺ induced partial crosslinking of PVA chains takes place via –OH groups, although complete gelling does not occur. The dispersion forms flexible and uniform films on glass and metal surfaces that does not dissolve after complete drying; this observation combined with shear thinning encourages its application as ink or paint. © 2011 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2011