Highly ordered materials

Lowik D, Shklyarevskiy 10, Ruizendaal L et al (2007) A highly ordered material from magnetically aligned peptide amphiphile nanofiber assemblies. Adv Mater 19 1191-1195... 

The pores of the silica template can be filled by carbon from a gas or a liquid phase. One may consider an insertion of pyrolytic carbon from the thermal decomposition of propylene or by an aqueous solution of sucrose, which after elimination of water requires a carbonization step at 900°C. The carbon infiltration is followed by the dissolution of silica by HF. The main attribute of template carbons is their well sized pores defined by the wall thickness of the silica matrix. Application of such highly ordered materials allows an exact screening of pores adapted for efficient charging of the electrical double layer. The electrochemical performance of capacitor electrodes prepared from the various template carbons have been determined and are tentatively correlated with their structural and microtextural characteristics. 

The same hypothesis can be applied to preparations made in suspension. In C-S-H(f), increase in Ca/Si ratio above the theoretical minimum value of 5 6 probably results entirely from omission of bridging tetrahedra until a value of about 1.0 is reached. Relatively highly ordered materials can be obtained. Further increase in Ca/Si ratio could result either from omission of more bridging tetrahedra, or from the presence of regions of Jennite-type... 

X-ray diffraction measurements and structural calculations on murein [22-25] and pseudomurein [26-28] have revealed several common structural features in both polymers. Murein and pseudomurein sacculi possess a density of p= 1. 39-1.46g/cm which is characteristic of highly ordered material. A much lower density, in the range of p= 1.24-1.32g/cm is to be expected for amorphous polymers [26]. X-ray diffraction showed diffuse Debye-Scherer rings with Bragg periodicities of about 0.45 nm and 0.94 nm in the planes and of 4.3-4.5nm vertically to the planes of both types of cell walls. These data have been interpreted in two different ways ... 

The highly ordered materials are based principally on ordered arrangements of pores, the walls of which are essentially disordered. 

Fig. 5 A schematic illustrating the necessity of an interconnected pore system for the formation of mesoporous carbon. When MCM-41 (A), which does not have interconnections, was used as template, the structure collapsed upon calcination. The use of large pore interconnected SBA-15 (B) led to a stable, highly ordered material. (Adapted from Ref. I)...

As was shown for polydiacetylene [15] the presence of the exciton peak at the energy of 1.6 eV provides evidence for the high degree of ordering of carbon chains in the film. Therefore we can conclude that the sp -hybridized carbon films also consist of a very highly ordered material. 

The design and synthesis of highly ordered materials is one main aim in polymer, supramolecular and material science (7,2). Such architectures, e.g. on surfaces or in thin films, could provide new mechanical, thermal, electrochemical, photochemical or magnetic properties. In particular systems containing metal ions are of special interest. Several approaches lead to such materials ... 

Figure 21.25. Classification of standard isotherms (lUPAC [34]). Type I Material that is microporous only, Type II and III, statistical multilayer adsorption on a wetting (II) and a nonwetting surface (III). Type IV (wetting) and V (non-wetting) Mesoporous materials showing a characteristic hysteresis that indicates capillary condensation. VI Stepwise adsorption in a highly ordered material (e.g., graphite).

Dendronized poljnners can, however, also be designed so that there is an attractive interaction between dendrons that leads to shape control. This requires two features (1) dendrons with mesogenic properties and (2) their loose attachment to the backbone which leaves the dendrons sufficient freedom to find the optimum packing. This kind of shape control driven by the dendrons mesogenic properties can lead to highly ordered materials in the solid state as will be described later. 

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