Nanocomposite PANI/MWCNT

Figure 9.19 Frequency dependence of (a) dielectric constant (cO and real permeability ip. ), (b) dielectric loss (e")> and magnetic loss (p") of PANI-MWCNT/PS nanocomposites with increasing loading (10, 20, and 30 wt.%) of PANl-MWCNT filler. Reprinted from Ref [11] with permission from Elsevier.

The actual losses can be computed by normalization of these losses with storage terms [i.e., by ratio of dielectric losses/imaginary permittivity is") with dielectric constant/real permittivity ( )] to quantity loss tangent (tan 8). In case of in-situ formed PANI/MWCNT nanocomposites, improvement of dielectric properties leads to high value of loss tangent (Figure 9.23b) which further increases with increase in MWCNT loading. 

Copper chloride (CuCy-doped polyaniline (PANI)/multi-walled carbon nanotubes (MWCNTs) nanocomposite (PANI C2 CNT), CuCy doped PANI (PANI C2) and pure PANI were synthesized by in-situ oxidative polymerization method. The maximum specific capacitance of 724 F/g... 

While care was taken to purify the carbon nanotubes as much as possible before synthesis of the nanocomposite material by using a combination of ultrasonication, washing with deionized water, drying in air, and washing with HCl [29], some impurities must have remained in the sample, causing the observed drop. Additionally, the PANI-MWCNT sample contained a higher amount of moisture, as it was observed that this sample readily absorbed moisture, as the sample was handled and stored in atmospheric conditions. 

Performance improvement of polysulfone ultrafiltration membrane has been achieved by blending with PANI-NFs [457]. Conducting blends of nanostruetured PANI and PANI-clay nanocomposites with ethylene vinyl acetate as host matrix have been prepared [458]. A new conducting hybrid biocompatible composite material of PANI-NFs well dispersed in a collagen matrix was fabricated with various PANI-NFs/eoUagen ratios [459]. PANI-NFs doped by protonic acids can be efficiently dispersed in vinylidene fluoride-trifluoroethylene copolymers [460]. Fabrication of MWCNTs/PANI-NF nanocomposites via electrostatic adsorption in aqueous colloids has been reported [143]. A PANI-NFs/ carbon paste electrode was prepared via dopping PANI-NFs into the carbon paste [461]. 

Chloroform sensing mechanism by PANI/c-MWCNT nanocomposite... 

In recent decades, there have been many attempts to fabricate CNT/PANI composites [329-337]. The incorporation of nanotubes into PANI can result in novel composite materials with enhanced electrical, electrochemical, and mechanical properties. Eor example, Yu et al. prepared MWCNT/PANI nanocomposites through in situ inverse microemulsion synthesis [334]. Such nanocomposites are characterized by very strong interaction between MWCNTs and conducting polymers. Moreover, MWCNT/PANI core-shell nanowires exhibited better thermal stability and electrical conductivity than the pure PANI. The electrical conductivity of MWCNT/PANI composite containing 1 wt% of MWCNTs increased by one order of magnitude (pure PANI 0.02Scm MWCNT/PANI composite 0.20Scm-i) [334]. 

In turn, Konyushenko et al. obtained MWCNT/PANI composites during in-situ polymerization in the presence of MWCNTs, which were uniformly coated with protonated PANI [330]. The electrical properties of nanocomposites were investigated, and similar effects as in previous work [334] were observed, i.e., the electrical conductivity increased with increased concentration of nanotubes in composite materials. The maximum conductivity, 25.4Scm was recorded for composites containing 70 wt% of MWCNTs [330]. Likewise, Wu et al. reported the increase of electrical conductivity for MWCNT/PANI composites [329]. The electrical conductivities of MWCNT/PANI composites containing 0.5 wt% functionalized MWCNTs are about 60-70% higher than of net-PANI [329]. 

Table 1 Difihision coefficient and diffusion length of PANi-Px-MWCNT nanocomposites [Reproduced with permission from [23]...

Px-MWCNT ratios were maintained as 0.75 0.25 (PANi-75), 0.50 0.50 (PANi-50) and 0.25 0.75 (PANi-25). PANi-50 and PANi-25 nanocomposites based supercapacitors exhibited 91 % and 93 % capacitive retention after 2000 charge-discharge cycle while pure PANi showed only 67 % capacitance retention for the same number of cycles. The diffusion length decreased with a decrease in PANi content in the nanocomposites as shown in Table 1. The enhancement of the charge-discharge rate capability of supercapacitors is attributed to the diffusion length of the nanocomposites [23]. 

---