Scientific Study, 2017
11 Pages, Grade: 10
In this study Multi Walled Carbon Nanotubes (MWCNTs) were functionalized by amine group and Polyaniline nanocomposites with functionalized MWCNTs were prepared by ex-situ method. The amine functionalized MWCNTs (am-CNTs) were simply and efficiently blended ultrasonically in the Isopropyl Alcohol solution of polyaniline emeraldine base (PANIEB). Results show the characterization of am-CNTs/PANIEB nanocomposites as a function of different am-CNTs concentrations by weight. The structure and morphology of the composites were characterized by scanning electron microscopy; Transmission electron microscopy and Fourier transform infrared spectroscopy.
Carbon Nanotubes, Polyaniline, Nanocomposites, Conducting Polymers, Morphology.
The composites of carbon nanotubes (CNTs) along with the conductive polymers enhance the mechanical properties of the conducting polymers and also introduce novel electronic properties. These properties are actually based on the interaction between the two materials. 
Among many conductive polymers, polyaniline (PANIEB) is of special interest for the synthesis of Polymer/CNTs composites because of its efficient processability, environmental durability and reversible control of the conductivity both by charge-transfer and protonation doping. A considerable advancement has been made in the fabrication and designing of Polyaniline-Carboxylate multi-walled carbon nanotubes (PANIEB/MWCNTs) composites, because of their exclusive electrical properties as well as their considerable application in electronic devices . Recent results showed that the conductive polymers with the carbon nanotubes having high aspect ratio and conductivity may have significantly improved the mechanical and electrical properties as compared to pure conductive polymers; also the carbon nanotubes provide efficient reinforcement and high thermal stability, making it suitable for various microelectronic applications . Many recent articles suggested various methods for the incorporation of CNTs into PANIEB matrix. Ramamurthy et al.  report solution mixing technique for incorporation of CNTs in the PANI matrix and used specific gravity measurement to illustrate the degree of CNTs dispersion. H. Zengin et al.  reported the synthesis of PANI/MWCNT composite by in-situ Polymerization and ex-situ solution mixing technique.
The experiment was carried out in three steps.
In first step the pristine CNTs was mixed with HNO3 in a double neck round bottom flask fitted with reflux condenser. Temperature was adjusted at 100OC and the time of the operation was adjusted to 24 hrs. The acidic functionalized CNTs (a-CNTs) was separated through centrifuging and washed thoroughly with distilled water under neutral reading was obtained. The acidic functionalized CNTs were then dried.
In the second step the a-CNTs was sonicated with distilled water for 30 min. The sonicated mixture of a-CNTs and distilled water was poured in the auto calve and the octadecyl amine (ODA) was added to it. The autoclave contains the mixture of distilled water, a-CNTs and ODA was heated to 100OC for 24 hrs. The amine functionalized CNTs (am-CNTs) was separated with the help of centrifuging and was then washed with acetone for 5 times.
In the final step different concentrations of am-CNTs (1%, 2%, and 5%) by weight were dispersed ultrasonically in the polyaniline emeraldine base (PANIEB) Isopropyl Alcohol mixture. All samples were sonicated for 30 minute each using ultrasound (Power Sonic 410) to get uniform dispersion of am-CNTs with in the Polyaniline matrix.
Fig 1 (a,b,c) shows the TEM micrograph of am-CNTs/PANI hybrid materials, which display new network structure. Sample (a) contains 1% am-CNTs, which is capsulated with PANIEB and the dispersion of am-CNTs can be observed in the polymer. In sample (b) the hybrid material contains 2% am-CNTs in the polymer matrix. Both Fig (a,b) have little PANIEB particulates in the am-CNTs/PANIEB nanocomposites. The web-like material is inter-connecting the individual am-CNTs present in the polymer matrix. Sample (c) contains 5% am-CNTs. The am-CNTs are well dispersed and encapsulated with the PANIEB. Almost all the individual am-CNTs are well coated with the polymer. The encapsulated am-CNTs are further interconnected which is providing a conductive passage in the polymer nanocomposites. In samples (a,b) the am-CNTs is not fully coated with the PANIEB whereas in sample (c) the am-CNTs are uniformly wrapped with the polymer.
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Fig.1 Transmission Electron Microscopy of am-CNT/PANI nanocomposites. (a) 1% am-CNTs, (b) 2% am-CNTs, (c) 5% am-CNTs.
Fig.2 shows the SEM for the pure PANIEB and three samples, Fig.2 (a) shows the SEM image of pure PANIEB, whereas (b), (c) and (d) shows the SEM image of 1wt%, 2wt% and 5wt% am-CNTs/PANIEB composite respectively. It is observed that am-CNTs are uniformly distributed in the polymer matrix. SEM images of am-CNTs/PANIEB showed that the am-CNTs are entrapped in the PANIEB matrix to give a composite-like appearance. It can be clearly observed from Fig (b), (c) and (d) that the am-CNTs is uniformly dispersed in the polymer matrix even at high concentration e.g. 5 wt.%.
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Fig.2 SEM images for the (a) pure PANIEB and am-CNTs/PANIEB nanocomposites with concentration of (b) 1wt % am-CNTs (c) 2wt% am-CNTs and (d) 5wt% am-CNTs.
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Fig.3 Fourier Transmission Infrared Spectroscopy for am-CNTs/PANIEB nanocomposites.
Fig.3 shows the FTIR spectra for the three different concentrations of am-CNTs in the polymer matrix. Broad peaks at ~3450 cm−1, represents the O-H stretch of the hydroxyl group. The FTIR spectra of the samples indicate the presence of the benzoid and quinoid ring vibrations at about 1485 and 1600 cm−1 [6, 7], respectively which exhibits the oxidation state of emeraldine salt polyaniline. The vibration at 1500 cm−1 is more intense than that of the quinoid band at 1600 cm−1. MacDiarmid et al. described the band at 1150 cm−1 as the “electron-like band” and it is the measure of delocalization of electrons and it belongs to the PANI conductivity . The vibration near 1350 cm−1 represents the presence of C-N group . The peak appearing 750 cm−1 is for =C-H which is the occurrence of out of plane bending.
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