Alumina templates, poly nanotubes

Alumina nanoporous templates have also been used in gas-phase growth of CPNTs. It has been reported that isolated nanotubes consisting of poly(p-phenylenevinylene) (PPV) and carbonized-PPV bilayers can be synthesized in an alumina template by chemical-vapor deposition (CVD) polymerization. In a smdy done by Kim and colleagues, CVD polymerization of PPV was carried out by passing monomer vapor through a pyrolysis zone at 625 °C to form precursor polymer nanotubes on the inner surface of the alumina nanochannels. The nanotubes were further thermally treated in vacuum at 270 °C for an extended time (14 h) to be converted into PPV nanotubes. In order to create PPV/ carbonized PPV bilayer nanotubes, the PPV nanotubes were then carbonized at 850 °C... 

Xiao et al. investigated the electrochemical synthetic mechanism of conducting-polymer nanotubes in a porous alumina template using poly(3,4-ethylenedioxythiophaie) (PEDOT) as a model compound [70]. The electrochemical polymerization of EDOT was performed potentiostatically at various potentials from 1.0 to 1.8 V (vs. Ag/AgCl) in a solution containing EDOT, LiC104, and acetonitrile. They found that the tubular portion of the nanotube structure increased as the applied potential increased from 1.4 to 1.8 V at a fixed concentration of EDOT, while the tubular portion decreased with increasing monomer concentration from 10 to 100 mM at a fixed poteitial of 1.6 V. 

A large step towards bio-functional nanotubes was taken by the same research group. An alumina membrane was first coated with two alternating layers of poly(ethylene imine) and poly(styrenesulfonic acid). Cytochrome c, with a positively charged surface at pH 7, was then alternated five times with poly(styrenesulfonic acid) in a LbL nanotube synthesis. Alternatively, cytochrome e and glutaraldehyde were employed to build up five covalent bilayers. Dissolution of the alumina template with 5% phosphoric acid yielded the protein-containing nanotubes. ... 

Among oxides, alumina template has been widely used because of its easy preparation by anodic treatment of aluminum metal. Nanofibrils with uniform and well aligned structure made of copolymers based on PANI and PPy have been prepared on this template [238] and aligned nanotubular heterojunctions of poly(p-phenylene) and PTh have been isolated it has been demonstrated that the length and the wall thickness of the nanotubes can be controlled by varying experimental parameters such as the electropolymerization current, the duration, and the nature of the doping anion present in the electropolymerization solution [239, 240]. 

Anodic aluminum oxide (AAO) membranes are a popular choice as templates for nanowires and nanotubes. As such they have been used to fabricate polymer nanochannels, mostly via melt inbltration, which has given the possibility of stud dng the wetting and flow of polymer melts in the alumina pores. In one such work an enhanced flow rate of poly-caprolactone was observed when mechanical vibration is applied to the AAO during the filling process. It... 

Wehrspohn and coworkers fabricated palladium nanotubes (Figure 9.15) through a template-assisted process [65] whereby dichloromethane or chloroform was used to form a solution of poly(D,L-lactide) (PDLLA) and palladium acetate. The solution was added to porous alumina in a 1 1 ratio under ambient conditions. Vaporization of the solvent resulted in the formation of Pd(OAc)2/PDLLA tubes, followed by annealing at 200 °C which degraded the precursor to elemental palladium. Further pyrolytic treatment at 3500°C removed PDLLA, while the alumina tern-... 

Figure 9.15 Scanning electron micrographs of poly(D,L-lactide (PDLLA). (a) An array of Pd nanotubes (pore diameter 400nm, pore aligned palladium nanotubes (b) Crossdepth lOOpm) obtained by wetting porous sectional view of an individual nanotube, alumina and after annealing at 200°C for Reproduced with permission from Ref [62] 6h and removing both the template and 2007 Wiley Interscience.

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