Polystyrene template

An excellent example that shows the potential of combining various bottom-up techniques is the joint work by Whitesides and Stucky [4]. Hierarchical metallic oxides were produced by combining (i) sol-gel self-assembly of neutral surfactants, (ii) spherical polystyrene templates, and (iii) molds with micrometric cavities (micromolding). Figure 3.12 shows how the described materials are hierarchically organized at several scales ranging from a few nanometers to hundreds of micrometers. 

X. Luo, G. D. Vidal, A. J. Killard, A. Morrin, and M. R. Sm3dh, Nanocauliflowers A nanostructured polyaniUne-modified screen-printed electrode with a self-assembled polystyrene template and its application in an amperometric enzyme biosensor, Electroanalysis, 19, 876-883 (2007). 

Y. Yang, Y. Chu, F.Y. Yang, and Y.P. Zhang, Uniform hollow conductive polymer microspheres synthesized with the sulfonated polystyrene template. Mater. Chem. Phys., 92(1), 164-171 (2005). 

A standard three-electrode cell equipped with an Ag/AgCl reference electrode and a platinum mesh or stainless steel counter electrode was used for the metal electroplating. Before immersing the polystyrene templates into the plating solution they were dipped into methanol to enable the infiltration of the hydrophobic meso-pores by the aqueous electrolyte. Subsequently, the samples were rinsed with deionized water, dried, and electively freed from the styrenic template by dissolution in toluene for several minutes. Platinum metal was deposited potentiostatically at room... 

G. Rethore, A. Mathew, H. Naik, A. Pandit, Preparation of chitosan/ polyglutamic acid spheres based on the use of polystyrene template as a nonviral gene carrier. Tissue Eng. Part C Methods 15 (2009) 605-613. 

Ceramic monolithic structures made from inverted opal silicon carbonitride (see Figure 6.6) were presented by Mitchell et al. [460]. The inverse opal structure was achieved using polystyrene templates. They prepared monoliths of 74% porosity, typically 350-pm wide, 100-pm high and 3-mm long. Propane steam reforming was then successfully performed in the reactor (see Section 7.1.2). 

Other approaches for the electrodeposition of structured Pt based films involved polystyrene spheres that were pre-self-assembled on the substrate prior to deposition. The film thickness and pore volume can be varied by using different diameters of polystyrene spheres. 3D nano-network structures were made in this manner. Both the lyotropic liquid template and the self-assembled polystyrene template method have been employed to form Pt and PtRu alloy films [75, 76]. An example of a macroporous Pt-based film made using polystyrene spheres is shown in Figure 9.7. 

The mechanical properties of the colloids are determined by the mechanical properties of the silica shell. To calculate the Young s modulus of the silica shell, the shell thickness needs to be known. Therefore, the mechanical characterization was performed on hollow silica colloids with smooth surface, [32, 43], The size of the colloids was adjusted by using polystyrene templates of different diameter and the shell thickness was tuned by the amount of tetraethoxysilane added to the reaction mixture. The polystyrene core was removed by calcination. The shell thickness of the hollow colloids was measured from transmission electron microscopy images (Fig. 7a). 

Schematic illustration of the preparation process for 3D macroporous LiFeP04 (a) self-assembly of polystyrene spheres (b) addition of a mixed solution of Li, P, and Fe sources to ordered polystyrene template and (c) heat treatment to obtain 3D macroporous liFeP04. (From Hou, Y.Y. et al., /. Mater. Chem. A., 1,2013.)...

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