Templating silica network construction using 3,5-dihydroxybenzylalcohol based dendrimers: influence of dendrimer aggregation on evolving network structure

The role of inter-dendritic interactions in 3,5-dihydroxybenzylalcohol (DHBA) based dendrimers of generations 0-5 (G0-G5), used as templates in the construction of hybrid silica networks, on the surface morphology is explored. Reaction of periphery situated hydroxyl groups in these dendrimers with Si(NMe2) 4 or ClSi(NEt2) 3, followed by hydrolysis and polycondensation yields highly crosslinked silica based hybrid materials. The use of chloro/aminosilane reagents leads to in situ removal of dendrimer templates while in the case of tetraaminosilane, the dendrimer moieties are subsequently removed upon treatment with HCl. A detailed study of these network materials before and after removal of dendrimer fractions using solid state NMR and FT-IR spectroscopies, transmission electron microscopy and nitrogen adsorption, reveals that the aggregation of DHBA based dendrimers controls the evolution of the network structure and their pore sizes. The resulting dendrimer templated networks are water repellant on their surfaces with a hydrophilic interior.