Polymer-templated ordered mesoporous films

Richman EK et al (2008) Ordered mesoporous silicon through magnesium reduction of polymer templated silica thin films. Nano Lett 8(9) 3075-3079 Shen L et al (2012) Magnesiothermically reduced diatomaceous earth as a porous silicon anode material for lithium ion batteries. J Power Sources 213 229-232 Shen X et al (2013) Si/mesoporous carbon composite as an anode material for lithium ion batteries. J Alloys Compounds 552 60-64... 

Fang J, Kang CB, Huang Y, Tolbert SH, Pilon L (2012) Thermal conductivity of ordered mesoporous nanocrystalline silicon thin films made from magnesium reduction of polymer-templated silica. J Phys Chem C 116 12926-12933 Fricke J, Hummer E, Morper H-J, Scheuerpflug P (1989) Thermal properties of silica aerogels. Revue de Phys Appl Colloque C4 24 87-97... 

The synthesis of OMC involves the use of ordered mesoporous silica (OMS) template with a specific pore topology [7]. As illustrated in Figure 3.1, the appropriate carbon precursor (carbon sources such as sucrose, furfuryl alcohol, acetylene gas, pyrrole, and acrylonitrile) is fed into the pores of the template via the infiltration approach, followed by its carbonization to achieve the siUca-carbon composite and template removal in ethanol-water solution of HF or NaOH to obtain the mesoporous carbon replica. The structure of the as-obtained OMC strongly depends on the structure of the used template. Chang et al. [7] have reviewed the synthesis of OMC as support materials for fuel cell applications. The rod- and tube-type mesoporous carbon structures can be realized by filling carbon precursors in the template pores and coating carbon precursors as a thin film on the pore walls of the template, respectively. In order to get the well-defined structure of OMC, the template should have three-dimensional interconnected pore structure. On the other hand, the carbonization of the carbon precursors should be confined exclusively within the mesopores of the ordered mesoporous silica templates with sufficient carbon precursor filling therefore, before the pyrolysis process, the carbon soiu-ce should be converted to a cross-linked polymer induced by the use of the acid polymerization catalysts [5,7]. 

Figure 7.3a shows the profound impact a so-called non-solvent for PT, such as chlorobenzene, can have on the nanostructure. Although chlorobenzene does not dissolve the polymer film, no obvious mesoporous nanostructure is left after template removal. This is most probably due to diffusion of solvent molecules into the conjugated polymer which destabilize the about 11 nm thick gyroidal network struts and eventually leads to the structural collapse. Using diethyl ether as solvent for the template dissolution instead resulted in mesoporous and highly ordered films. However, the free-surface did not show the same degree of order and porosity as the bulk of the film, see Fig. 7.3c. This behavior at the free-surface was more pronounced in the case of PEDOT and PPy, and will be discussed in more detail in the following to sections.

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