Preparation and characterization of soluble and DBSA doped polyaniline grafted multi-walled carbon nanotubes nano-composite

Soluble and highly doped polyaniline (PANI) grafted multi-walled carbon nanotubes (MWNTs) nano-composite was synthesized by in situ oxidation polymerization, de-doping with ammonium hydroxide and doping the PANI-Emeraldine base (PANI-EB) grafted MWNTs nano-composite in N-methyl-2-pyrrolidinone (NMP) with Dodecyl benzene sulfonic acid (DBSA). Transmission electron microscope (TEM), Raman spectra, Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS) and standard four-probe methods were employed to characterize morphology, chemical structure and electronic conductivity of the nano-composite. The results show that oxidized phenylamine groups of phenylamine groups contained MWNTs (p-MWNTs) initiate PANI polymerization on the surface of p-MWNTs. PANI coatings graft on the surface of p-MWNTs via amide bond forming homogeneous core (p-MWNTs)–shell (PANI) nano-structures. After doping PANI-EB grafted MWNTs nano-composite with DBSA, the attachment of soluble DBSA doped PANI chains on the surface of p-MWNTs via covalent bonding renders p-MWNTs compatible with polymer matrix and lead to DBSA doped PANI grafted MWNTs nano-composite soluble and stable in NMP. Owing to incorporation of p-MWNTs and chemical bridges between p-MWNTs and PANI chains, conductivity of DBSA doped PANI grafted MWNTs nano-composite at room temperature is increased by about two orders of magnitude over neat DBSA doped PANI.     

可溶性DBSA掺杂PANI接枝MWNTs复合材料的结构与性能

多壁碳纳米管(MWNTs)经对苯二胺功能化后,苯胺基团以3.7%的含量通过酰胺键连接到MWNTs表面(p-MWNTs),以十二烷基苯磺酸(DBSA)为掺杂剂和乳化剂,通过原位聚合,制备了在四氢呋喃(THF)中稳定溶解的DBSA掺杂聚苯胺(PANI)接枝MWNTs(PANI-g-MWNTs)导电复合材料.采用Raman光谱、傅里叶变换红外光谱(FTIR)、X射线光电子能谱(XPS)、紫外-可见光谱(UV-vis)、透射电子显微镜(TEM)、X射线衍射仪(XRD)和四电极电导率仪研究复合材料的结构与性能.实验结果表明,p-MWNTs表面的苯胺基团参与原位聚合反应,使PANI与p-MWNTs通过酰胺键连接起来,形成以p-MWNTs为核、DBSA掺杂PANI为壳的纳米结构.包覆层中DBSA掺杂PANI受限生长在p-MWNTs表面,其结构规整度较纯DBSA掺杂PANI提高.DBSA掺杂PANI-g-MWNTs复合材料溶解在THF中获得31.55 mg/mL的溶解度和至少1个月的稳定性,该复合材料的室温电导率为6.23×10-1 S/cm,较纯DBSA掺杂PANI提高1个数量级.     

聚苯胺接枝多壁碳纳米管复合材料的结构与性能研究

多壁碳纳米管(MWNTs)经对苯二胺功能化后,通过原位聚合及去掺杂反应,首次制备了能在N-甲基吡咯烷酮(NMP)中稳定溶解的本征态聚苯胺(EB)接枝MWNTs(EB-g-MWNTs)复合材料。复合材料中EB与p-MWNTs通过酰胺键连接,形成以p-MWNTs为核、EB为壳的纳米结构,并且EB的结构规整度提高;当该复合材料溶解在NMP中时,溶解度为33.72mg/mL,稳定性好,至少可保存1个月。     

Preparation polystyrene/multiwalled carbon nanotubes nanocomposites by copolymerization of styrene and styryl-functionalized multiwalled carbon nanotubes

Styryl-functionalized multiwalled carbon nanotubes (p-MWNTs) were prepared by esterification based on the carboxylate salt of carbon nanotubes and p-chloromethylstyrene in toluene. Then in situ radical copolymerization of p-MWNTs and styrene initiated by 2,2′-azobis(isobutyronitrile) (AIBN) was applied to synthesize composites of styryl-functionalized multiwalled carbon nanotubes and polystyrene (PS) (p-MWNTs/PS). Characterizations carried out by FT-IR, ¹H NMR, UV–vis show that styryl group covalently bond to the surface of MWNTs. The results of UV showed that the solutions of p-MWNTs/PS in chloroform have the hyperchromic effect. Transmission electron microscopy (TEM) images of p-MWNTs/PS composites and scanning electron microscopy (SEM) images of fracture surface of p-MWNTs/PS composites showed the functionalized nanotubes had a better dispersion than that of the unfunctionalized MWNTs in the matrix. The results of thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) suggested that the thermal stability of p-MWNTs/PS composites improved in the presence of MWNTs.     

DBSA二次掺杂聚苯胺接枝多壁碳纳米管复合材料的结构与性能研究

多壁碳纳米管(MWNTs)经对苯二胺功能化后,通过原位聚合及去掺杂和二次掺杂反应,首次制备了能在N_甲基吡咯烷酮(NMP)中稳定溶解的十二烷基苯磺酸(DBSA)二次掺杂聚苯胺接枝MWNTs(PANI-g-MWNTs)复合材料.研究表明:复合材料中PANI与p-MWNTs通过酰胺键连接,形成以p-MWNTs为核、DBSA 二次掺杂PANI为壳的纳米复合结构;当复合材料溶解在NMP中时,借助DBSA二次掺杂PANI的溶解性和p-MWNTs与PANI间的连接作用,使其在NMP中获得35.56mg/mL的溶解度和近1个月的稳定性;该复合材料的热稳定性在300～500℃明显提高,其室温电导率较DBSA二次掺杂PANI提高近两个数量级.     

聚苯胺纳米矩形管的制备与表征

以樟脑磺酸(CSA)为掺杂剂、过硫酸铵为氧化剂.在水溶液体系中通过苯胺原位聚合制得直径为300～600nm的聚苯胺纳米矩形管,其导电率为0.1～1S/cm.通过扫描电镜(SEM)和透射电镜(TEM)对产物的形貌进行表征.发现n(CSA)/n(ANi)将影响产物的形貌.利用傅立叶红外光谱(FT-IR)和紫外一可见光谱(Uv_vis)对聚苯胺分子结构进行表征,发现产物是质子化掺杂的聚苯胺.通过X射线衍射(XRD)分析发现,聚苯胺纳米矩形管比纤维结构具有更好的分子链排列规整性.     

聚氨酯/二氧化硅包覆多壁碳纳米管复合材料的导热与电绝缘性能

通过溶胶-凝胶法制备了厚度为30nm-50nm的二氧化硅(SiO2)包覆多壁碳纳米管(SiO2-MWNTs),并与聚氨酯(PU)复合制备了PU/SiO2-MWNT复合材料。研究了SiO2-MWNTs对PU导热电绝缘性能的影响。结果表明,SiO2包覆层增强了MWNTs与PU之间的界面相互作用,促进了MWNTs在PU中的分散。由于SiO2包覆层的电绝缘作用,PU/SiO2-MWNT复合材料保持了PU的电绝缘性能。同时SiO2包覆层作为过渡层,降低了PU与MWNTs间的模量失配,减少了声子的界面散射,提高了PU/SiO2-MWNT复合材料的导热性能。当SiO2-MWNTs的质量分数为0.5%和1.0%时,PU/SiO2-MWNT复合材料的热导率分别提高了53.7%和63.8%。     

MWNTs/PANI composite materials prepared by in-situ chemical oxidative polymerization for supercapacitor electrode

Multi-walled carbon nanotubes (MWNTs)/polyaniline (PANI) composite materials were prepared by in-situ chemical oxidative polymerization of an aniline solution containing well-dispersed MWNTs. The supercapacitive behaviors of these composite materials were investigated with cyclic voltammetry (CV), charge–discharge tests, and ac impedance spectroscopy, respectively. The composites based on the charge-transfer complex between well-dispersed MWNTs and PANI matrixes show much higher specific capacitance, better thermal stability, lower resistance, and were more promising for applications in supercapacitors than a pure PANI electrode. The highest specific capacitance value of 224 Fg⁻¹ was obtained for the MWNTs/PANI composite materials containing MWNTs of 0.8 wt%. The improvement mechanisms of the capacitance of the composite materials were also discussed in detail.     

Comparative studies of solid-state synthesized polyaniline doped with inorganic acids

Polyaniline (PANI) salts doped with inorganic acids (HCl, H₂SO₄ and H₃PO₄) were directly synthesized by using solid-state polymerization method. The FTIR spectra, UV–vis absorption spectra and X-ray diffraction patterns were used to characterize the molecular structures of the PANI salts. Voltammetric study was done to investigate the electrochemical behaviors of all these PANI salts. The PANI salts were affected by varying the protonation media (HCl, H₂SO₄ and H₃PO₄). The FTIR and UV–vis absorption spectra revealed that all PANI salts contained the conducting emeraldine salt phase at different oxidation state. The crystallinity of PANI doped with HCl was better than those doped with H₂SO₄ and H₃PO₄. The conductivity of the PANI doped with HCl is the highest among the inorganic acid doped PANI.     

Potentiometric study of polyaniline film synthesized with various dopants and composite-dopant: A comparative study

The potentiometric study of polyaniline (PANI) film synthesized with dopants viz. polyvinyl sulfonic acid (PVS),p-toluene sulfonic acid (p TS), dodecyl benzene sulfonic acid (DBS) and composite-dopants viz. PVS-p TS and PVS-DBS, has been carried out. The synthesized PANI films were characterized by electrochemical technique, UV-visible spectroscopy, Fourier transform infrared spectroscopy (FTIR), scanning electron microscope (SEM) and conductivity measurement. It was found that the PANI doped with PVS gives good electrochemical properties, conductivity as well as surface morphology as compared to p TS and DBS, whereas in composite dopants the PANI doped with PVS-pTS gives good polymer matrix as compared to PVS-DBS.     

Preparation and characterization of water soluble and conducting poly(sodium 4-styrenesulfonate) doped poly(3,4-ethylenedioxythiophene)/multi-walled carbon nanotubes core–shell nanocomposites by in situ polymerization

Water soluble and conducting poly(sodium 4-styrenesulfonate) (PSSNa) doped poly(3,4-ethylenedioxythiophene) (PEDOT)/multi-walled carbon nanotubes (MWNTs) nanocomposites were synthesized by PSSNa functionalized MWNTs and 3,4-ethylenedioxythiophene (EDOT) in situ oxidation polymerization. In the process, MWNTs were functionalized by PSSNa via physicochemical interaction, PSS groups on the surface of MWNTs absorbed EDOT monomers and acted as counter ions during in situ polymerization, macromolecules of PEDOT growth on the surface of MWNTs formed a homogeneous core (MWNTs)–shell (PEDOT) nanostructure. Owing to water soluble PEDOT–PSSNa coating on the surface of MWNTs and the association of PSSNa acting as inter-linking between PEDOT and MWNTs, the core–shell nanostructures were dissolved in water forming stable aqueous solution with good transparence. The composite was more stable in the temperature range up to 300 °C and exhibited improved thermal stability at the range of 300–500 °C compared with PEDOT–PSSNa. Because of π–π interactions between MWNTs and PEDOT coatings as well as homogenously dispersion of MWNTs in PEDOT, conductivity of the composites at room temperature was increased by two orders of magnitude over PEDOT–PSSNa.     

Electron field emitters based on multi-walled carbon nanotubes coated with conducting polymer/metal/metal-oxide composites

The present work describes the field emission properties of multi-walled nanotubes (MWNTs)-based conducting polymer/metal-oxide/metal/MWNTs composites (polyaniline (PANI)/SnO₂/Sn/MWNTs). MWNTs were synthesised by chemical vapour deposition technique. SnO₂/Sn/MWNTs were prepared by using chemical reduction followed by calcination. By in situ polymerisation method, surface of SnO₂/Sn/MWNTs were coated with PANI. PANI/SnO₂/Sn/MWNTs field emitters were fabricated over flexible graphitised carbon fabric substrate by spin coating technique. High-resolution transmission electron microscopy and scanning electron microscopy were used to characterise the field emitters. Field emission properties have been studied using an indigenously made facility. The fabricated PANI/SnO₂/Sn/MWNTs field emitters exhibited excellent field emission properties with a turn on field of 1.83 V µm^?1 and a field enhancement factor of 4800.     

Polyaniline as a Gas-Sensor Material

Polyaniline (PANI) was synthesized by oxidative polymerization of aniline using ammonium persulfate in an acid medium. The polyaniline salt was converted to base form by treatment with ammonium hydroxide. The polyaniline base was dissolved in N-methyl pyrrolidone (NMP) for film casting. The cast film was doped with HCl for obtaining higher conductivity. Both doped and undoped PANI films were characterized by UV-visible, FTIR, and XRD analyses. The electrical conductivity of the PANI film was studied by a four-point probe method at room temperature. Finally, ammonia gas-sensing characteristics of the prepared polyaniline film were studied by measuring the change in electrical conductivity on exposure to ammonia gas at different concentrations. The influence of concentration of acid during polymerization of aniline and dopant concentration on the gas sensing characteristics of PANI film are reported in this paper.     

Synthesis of poly(ethylene glycol) functionalized MWNTs and their inclusion complexes with α-cyclodextrin

Poly(ethylene glycol) (PEG) functionalized multiwalled carbon nanotubes (MWNTs), prepared by coupling of isocyanate-decorated MWNTs with PEG of different molecular weights (M _n = 400, 1000, 2000, and 4000 g/mol), were used to form inclusion complexes (ICs) with α-cyclodextrin (α-CD) through the grafted PEG chains being threaded with α-CD rings in aqueous solution. The FTIR, TGA, UV-Vis, and scanning electron microscopy (SEM) techniques were employed to characterize the formed ICs. The ICs formation time was monitored by UV-Vis spectroscopy, and the results indicated that the inclusion interaction between MWNT surface anchored PEG chains and α-CD was dependent on the molecular weight of PEG. The grafted PEG with molecular weights of 4000 and 2000 g/mol, respectively, can form ICs with α-CD, while the grafted PEG with molecular weights of 1000 and 400 g/mol, respectively, are difficult to form ICs with α-CD due to the steric hindrance from nanotubes. The stoichiometry value determined by TGA indicated that the ratio of ethylene glycol (EG) unit to α-CD in the resulted ICs was about 15:1. In addition, the morphology of the ICs was observed by SEM and transmission electron microscopy (TEM).     

碳纳米管/聚苯胺复合材料的制备及电性能

利用超声波将多壁碳纳米管(CNTs)分散于苯胺盐酸溶液体系中,以过硫酸铵((NH4)2S2O8)为氧化剂,原位聚合法制备碳纳米管/聚苯胺纳米复合材料(CNTs/PANI)。采用扫描电子显微镜(SEM)、傅立叶变换红外光谱(FT-IR)、四探针电导率测试仪对复合材料进行表面观察、结构测定和电性能表征。结果表明,复合材料为核-壳结构,碳纳米管和聚苯胺间存在相互作用,其电导率随碳纳米管含量的增加而增加。     

Synthesis and characterization of new polyaniline/nanotube composites

New polyaniline/nanotube (PANI/NT) composites have been synthesized by “in situ” polymerization processes using both multi-wall carbon nanotubes (MWNTs) and single-wall carbon nanotubes (SWNTs) in concentrations ranging from 2 to 50 wt.%. Although no structural changes are observed using MWNTs above a concentration of 20 wt.%, the in situ synthesis results in electronic interactions between nanotubes and the quinoid ring of PANI leading to enhanced electronic properties and thus to the formation of a genuine PANI/MWNT composite material. On the other hand, using SWNTs favors the formation of inhomogeneous mixtures rather than of a homogeneous composite materials, independent of the SWNT concentration. X-ray diffraction, Raman and transport measurements show the different behavior of both classes of nanotubes in PANI/NT materials. The difficulties in the formation of a true PANI/SWNT composite are related to the far more complex structure of the SWNT material itself, i.e. to the presence of entangled bundles of SWNTs, amorphous carbon and even catalytic metal particles.     

Novel neural interface for implant electrodes: improving electroactivity of polypyrrole through MWNT incorporation

Multi-walled carbon nanotubes (MWNTs) can be incorporated into conductive polymers to produce superior materials for neural interfaces with high interfacial areas, conductivity and electrochemical stability. This paper explores the addition of MWNTs to polypyrrole (PPy) through two methods, layering and codeposition. Conductivity of PPy doped with polystyrene sulfonate (PSS), a commonly used dopant, was improved by 50% when MWNTs were layered with PPy/PSS. The film electrochemical stability was improved from 38% activity to 66% activity after 400 cycles of oxidation and reduction. Growth inhibition assays indicated that MWNTs are not growth inhibitory. The electroactive polymer-MWNT composites produced demonstrate properties that suggest they are promising candidates for biomedical electrode coatings.     

Electrochemical fabrication of polyaniline/multi-walled carbon nanotube composite films for electrooxidation of methanol

Polyaniline (PANI)/multi-walled carbon nanotubes (MWNTs) composite films were fabricated by electropolymerization of aniline containing well-dissolved MWNTs. The films can be used as catalyst supports for electro-oxidation of methanol. Cyclic voltammogram and Chronoamperogram results show that platinum particles deposited on PANI/MWNT composite films exhibit higher electrocatalytic activity towards methanol oxidation than that deposited on pure PANI films. The porous structure and electrical conductivity of PANI films has been significantly changed by introduction of MWNTs, higher surface areas of PANI/MWNT composites has been achieved therefore. It favors for platinum particles to be highly dispersed on the PANI/MWNT composite films and the better electrocatalytic activity of Pt/PANI/MWNT electrode is induced consequently.     

Synthesis and characterization of polyaniline/activated carbon composites and preparation of conductive films

Polyaniline was synthesized via polyaniline/activated carbon (PANI/AC) composites by in situ polymerization and ex situ solution mixing. PANI and PANI/AC composite films were prepared by drop-by-drop and spin coating methods. The electrical conductivities of HCl doped PANI film and PANI/AC composite films were measured according to the standard four-point-probe technique. The composite films exhibited an increase in electrical conductivity over neat PANI. PANI and PANI/AC composites were investigated by spectroscopic methods including UV–vis, FTIR and photoluminescence. UV–vis and FTIR studies showed that AC particles affect the quinoid units along the polymer backbone and indicate strong interactions between AC particles and quinoidal sites of PANI. The photoluminescence properties of PANI and PANI/AC composites were studied and the photoluminescence intensity of PANI/AC composites was higher than that of neat PANI. The increase of conductivity of PANI/AC composites may be partially due to the doping or impurity effect of AC, where the AC competes with chloride ions. The amount of weight loss and the thermostability of PANI and PANI/AC composites were determined from thermogravimetric analysis. The morphology of particles and films were examined by a scanning electron microscope (SEM). SEM measurements indicated that the AC particles were well dispersed and isolated in composite films.     

Synthesis and thermal behavior of poly(ε-caprolactone) grafted on multiwalled carbon nanotubes with high grafting degrees

Poly(ε-caprolactone) (PCL) was grafted onto multiwalled carbon nanotubes (MWNTs) with high grafting degrees. The surface of MWNTs was first modified by 2-hydroxyethyl benzocyclobutene (BCB-EO) via a [2 + 4] cyclo-addition reaction. Polymerization of ε-caprolactone was conducted in the presence of BCB-EO modified MWNTs and the catalyst stannous octoate. Alternatively, the grafted-BCB-EO first reacted with CpTiCl₃ and then the reactant was used to catalyze polymerization of ε-caprolactone. The grafting degrees of PCL prepared from BCB-EO modified MWNTs can reach at least 94%, much higher than those prepared by other two conventional methods. TEM result shows that the morphology and thickness of the grafted PCLs strongly depend on the grafting degree and grafting method. The crystallization and melting behaviors of the MWNTs-grafted PCL were investigated. MWNTs can exert both nucleation and confinement effects on crystallization of the grafted PCL, leading to lower crystallinity but higher crystallization temperature (T_c) and melting temperature (T_m) of the grafted PCLs. It is found that crystallinity of the grafted PCLs increases with the grafting degree, but T_c and T_m also depend on the molecular weight.