## 3 Polymerization Reactions within AAO Templates
### Electrochemical Polymerization
They found a compromise between effectiveness and mildness of template dissolution conditions for a safe release of PPY nanotubes, i.e., they found that the effective release of functional poly-COOH-PPY-nanotubes from nanoporous AAO templating critically depended on finely tuned membrane digestion conditions. Concerning the synthesis of poly(3,4-ethylenedioxythiophene) (PEDOT), [PERSON] et al. [111] reported the fast charging/discharging capability of PEDOT nanotubes by electrochemical polymerization in a porous alumina membrane for high-powered supercapacitor applications (see Section 4.1. for further details). [PERSON] et al. also studied the fabrication and the electrical and optical properties of conducting PEDOT nanotubes by means of vapor deposition polymerization inside AAO templates having a diameter range from 50 to 200 nm [112] (see Section 4.1 for further details). Related to the templated synthesis of polyaniline microtubules, [PERSON] and [PERSON] studied the polymerization of aniline in microporous polycarbonate membranes [113]. In contrast to polypyrrole, the polyaniline (PANI) nanotubes did not close up, even after long polymerization times. This was explained on the basis that the surface layers eventually grow across the membrane surface and block the pore ends. As a result, the accessibility of the monomer and the oxidant for entrance into the pores was hindered and further polymerization within the pores was not possible. Therefore, no solid polyaniline fibers could be formed by this method giving rise to an improvement in the conductivity of the confined polymers, compared to the bulk samples, due to the high alignment of the confined polymer chains. [PERSON] et al. [114] also reported the synthesis of aniline and pyrrole copolymer nanofibrils within the pores of a microporous AAO membrane. In this case, both polymers were involved in the formation of the copolymer rather than in a composite. Continuing with aniline polymerization, [PERSON] et al. [115] reported the synthesis of highly ordered polyaniline nanotube arrays by in situ polymerization using AAO as  
Figure 3: Scanning electron micrographs of chemically synthesized polypyrrole microtubules (**a**,**b**) and electrochemically synthesized poly(N-methylpyrrole) microtubules (**c**) [27], Copyright 2011. Reproduced with permission from the publisher: Springer. nanoreactors. The doping degree of PANI nanotubes was higher than that of a PANI in bulk, since the crystal form of polyaniline nanotubes resulted in a more ordered structure of the polymer chains. [PERSON] et al. [116] reported the fabrication of intrinsically conducting PANI nanostructures (ICP) by polymerization of ANI within AAO templates and compared the properties to those of an extrinsically conducting polyvinyldifluororine (ECP) and multiwall carbon nanotubes (PVDF + MWCNT) obtained by melt infiltration of a PVDF + MWCNT film in AAO nanocavities of the same dimensions. Analysis of the final nanostructures of PANI and PVDF-MWCNT confirmed, in both cases, the formation of well-aligned and uniform rodlike polymer nanostructures, as shown in Figure 4. It was also found that the polymerization rate of ANI was critical and needed to be well-controlled to achieve the desired morphology. Moreover, confocal Raman microscopy demonstrated the formation of the conducting emeraldine salt of PANI through all the length of the AAO nanocavities and broadband dielectric spectroscopy (BDS) the enhancement of the electrical conductivity of polyaniline nanofibers polymerized in the nanocavities of the AAO template. When comparing a nanostructured ECP (PVDF with a 3% of MWCNT) and a nanostructured ICP (PANI), similar conductivity was obtained.