From Polymeric to Particulate Inorganic Macrocellular Foams: Some Integrative Chemistry Synthetic Pathways
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1007-S05-08
From Polymeric to Particulate Inorganic Macrocellular Foams: Some Integrative Chemistry Synthetic Pathways Florent Carn, and Rénal Backov C.R.P.P. CNRS UPR 8641, 115 Ave. Albert Schweitzer, Pessac, F-33200, France ABSTRACT Hierarchically organized matter appears today a strong and highly competitive field of research mainly induced by the wide scope of applications expected. In this context, chemistry of shapes appears as a strong interdisciplinary field of research combining soft chemistry and soft matter. Hierarchical inorganic porous silica monoliths can be obtained combining air-liquid foams either with molecular precursors promoting condensation within the foam’s Plateau borders confined geometry or with pre-synthesized nanobuilding blocks that will be organized within the foam’s Plateau border and films. By controlling the air-liquid foam’s water liquid fraction we can design the inorganic porous texture at the macroscale (i.e. cell sizes and shapes as well as the Plateau borders thickness). Considering the nanobuilding block approach, final scaffolds are a very close transcription of the tailored periodic air-liquid foam template, while highly ordered close-packed silica colloids are texturing the as-synthesized foam walls. The interconnected nanoparticles and associated void space between adjacent particles allow generating intrinsic mesopores, thereby defining hierarchically organized porous scaffolds. The good control over both the air-liquid foam’s water volume fraction and the bubble size allow a rational tuning of the macropore shapes (diameter, Plateau border’s width). In contrast with previous studies, closed-cell structures can be reached, while the opal like scaffold structure is maintained with thermal treatment, avoiding thus strong shrinkage associated to the sintering effect.
INTRODUCTION Meta-stable thermodynamic systems such as air-liquid [1] or bi-liquid [2] foams are of strong interest toward obtaining organized solid-state structures at the macroscopic length scale. To previous macroscopic patterns we can maintain micellar organization at the mesoscale leading thus to hierarchically organized architectures. Other routes enable to reach complex textures are based on either preformed nano-patterns [3] or micro-organism [4]. The overall strategies are strongly related to a growing field called the “chemistry of shapes”[5]. In the specific issue where meta-stable thermodynamic systems are used as macroscopic patterns, disorganized macroporous inorganic foams have been generated using either an effervescence method [6] or a strong stirring process [7]. Recently our group has developed new processes to obtain macrocellular silica monoliths with a high degree of control over both cell sizes and
morphologies [1], that we extended to other oxides like TiO2 [8] and V2O5 [9]. This first route uses a sol-gel foaming process where the foam’s water volumic fraction is controlled when performing the sol-gel chemistry. However, the macropores rational control (i.e. dimension and morphology)
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