Composite SWCNT/PANI

Figure 12.15 (a) Schematic diagram of a homogeneous coating of well-dispersed SWCNTs on sUicon electrode due to the random adsorption of PANl molecules onto SWCNTs and (b) FE-SEM image of the PANI/SWCNTs composite materials. Reproduced with permission from Ref [69], Copyright 2012 The Polymer Society of Korea and Springer Netherlands. 

For example, when the PANI-SWCNT sensor was individually exposed to NHj and CO, the sensor resistance increased and decreased, respectively, while the resistance increased for gas mixture (Figure 12.24). This is because the CO (-CO+) can naturally interact with undoped nitrogen atoms in the PANI chains to produce a polaron (-NH. ) thus increasing the conductance, while NHj reacts with the dopant HCl and decrease the doping ability or conductivity for it. Since the absorption response of NH might be faster than that of CO, the resistance increased over the initial value [69]. Firstly absorbed NH gas dominantly reacts with the composite materials, and followed reaction with CO gas cannot probably function properly in the total reaction. 

Raman spectroscopy has been used to probe interactions occurring in PAni nanotube [23-24] composites, the orientation of nanotube bundles within a matrix [25, 26], and the efficiency of load transfer from the host matrix to SWCNTs [27,28]. Unlike X-ray diffraction (XRD) methods [12], Raman spectroscopy can detect very low concentrations of SWCNTs in a polymer matrix [29,30]. The degree of orientation of aligned nanotubes can be estimated by polarized Raman spectroscopy due to the presence of a strong resonance Raman scattering effect [31,32]. Polarized Raman spectroscopy in combination with a mathematical model [33] has been employed to characterize the orientational order of nanotubes in polymers [34]. Using this model, the polarized Raman intensity of nanotubes is correlated with the orientation order parameters of SWCNTs in a utuaxially oriented system. An orientation distribution function can then be obtained. 

Gupta V, Miura N. Poly aniline/single-wall carbon nanotnbe (PANI/SWCNT) composites for high performance snpercapacitors. Electrochim Acta 2006 52 1721-6. 

Regarding the second route mentioned, the colloidal CNT-polymer particle system can be obtained by in situ polymerization. Barraza et al. demonstrated the possibility of preparing SWCNT-filled thermoplastic PS and elastomeric styrene-isoprene copolymer by using a modified version of mini-emulsion polymerization with a cationic surfactant, whereas Deng et al. synthesized CNT/ polyaniline [PANI) composites by in situ emulsion polymerization. Alternatively, the colloidal system can be prepared by direct mixing of the CNTs and the polymer host particles, after the polymerization has already been carried out. 

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