Composite PANI/clay

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]. 

Figure 14.16 X-ray dif action analysis comparison of Na -MMT, PANI, and PANI-clay composite (a) and ER properties of PANI-clay composite (b). Reprinted with the permission from Ret [94]. Copyright 1999 Wiley-VCH Verlag GmbH.

MMT is a clay naturally abundant and inexpensive, and due to its capacity to swell and exchange cations it is the most common inorganic matrix used for PAni composites [116-118]. Using anilinium intercalated clay (Ani-MMT) as precursor, it is possible to obtain a special type of nanocomposite when anilinium (Ani) polymerization is carried out mainly between the interlayer regions [119, 120]. 

The formation of intercalated and/or exfoliated nanocomposite is dependent on the monomer/clay ratio when aniline polymerization is performed in an acidic aqueous suspension of MMT in the presence of an oxidizing agent. If a small amount of PAni is present in the composite, conductivity of the material is still very close to that of pure MMT clay. In a critical amount of polymer and denominated percolation threshold [121], conductivity increases by several orders of magnitude with a small increase in the PAni amount. After reaching the optimum values, the value of conductivity starts decreasing and found very close to that of free PAni. On the oflier hand, nanocomposites of PAni-MMT [116, 118, 119] obtained by Ani-MMT polymerization show lower conductivity than fi ee PAni [117] and this fact can be attributed to the lack of connectivity between intercalated PAni chains [116, 118, 119] or a change in the nature of polymeric chains. 

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