Tailor-made Porous Membranes via Templates Containing Systems

6 TAILOR-MADE POROUS MEMBRANES VIA TEMPLATES CONTAINING SYSTEMS 

For silica gels a number of parameters have been demonstrated to have a large effect on the evolution of porosity and subsequently on the resulting silica materials [1]. Almost dense, micro- or mesoporous silica materials can be obtained depending on the experimental conditions in which hydrolysis and condensation reactions of silicon alkoxides are carried out. This is not the case for transition metal alkoxides which are very sensitive to hydrolysis. They do not cillow the adaptation of sol-to-gel transition in order to obtain controlled porous textures. Some years ago special attention was paid to the utilization of amphiphilic systems as reactive media to control hydrolysis and condensation kinetics with transition metal alkoxides [37]. In a more recent work Ayral et al. 

Other methods have been applied based on the insertion in the gel matrix of passive template agents such as chemically fixed organic entities or physically trapped polymer particles. Then the elimination of the templates leads to the formation of a porous structure in which a relation between pore size and physical dimension of incorporated templates is anticipated. 

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