Setting Directions: Anisotropy in Hierarchically Organized Porous Silica

• DOI: 10.1021/acs.chemmater.7b03032
• Publication Date: 2017-08-31T19:11:47Z
• Authors: Florian Putz; Roland Morak; Michael S. Elsaesser; Christian Balzer; Stephan Braxmeier; Johannes Bernardi; Oskar Paris; Gudrun Reichenauer; Nicola Hüsing
• Keywords: 02 engineering and technology; 0210 nano-technology

Structural hierarchy, porosity, and isotropy/anisotropy are highly relevant factors for mechanical properties thereby the functionality of porous materials. However, even though anisotropic hierarchically organized, materials well known in nature, such as bone or wood, producing synthetic counterparts laboratory is difficult. We report first time a straightforward combination sol–gel processing shear-induced alignment to create hierarchical silica monoliths exhibiting anisotropy on levels both, meso- macropores. The resulting material consists an macroporous network struts comprising 2D hexagonally organized cylindrical mesopores. While mesopores inherent feature pores formed by liquid crystal templating, macropores induced shearing network. Scanning electron microscopy small-angle X-ray scattering show that majority forming oriented towards direction; quantitative analysis data confirms roughly 40% strut volume exhibits preferred orientation. material's macroporosity also reflected its properties; i.e., Young's modulus differs nearly factor 2 between directions shear application perpendicular it. Unexpectedly, adsorption-induced strain little no anisotropy.