Porous silica spheres in macroporous structures and on nanofibres.

Porous nanospheres have a wide range of applications such as in catalysis, separation and controlled delivery. Among these nanospheres, syntheses and applications of porous silica nanospheres have been investigated extensively. Uniform porous silica nanospheres can be synthesized using a modified Stöber method. In the present study, porous silica spheres were prepared in the pre-formed emulsion-templated porous polyacrylamide (PAM). A hierarchical hybrid structure of mesoporous silica spheres was formed in the highly interconnected macroporous polymer. The polymer scaffold could be removed by calcination with porous silica spheres and the macroporous structures retained. This resulted from the close packing or aggregation of small silica nanospheres in the pores and on the surface of pores of PAM. The modified Stöber synthesis was further carried out in pre-formed polymer nanofibres (chitosan and sodium carboxymethyl cellulose). The structure of porous silica spheres on nanofibres was produced in the presence of the polymer or composite fibres. The corresponding inorganic structures were successfully obtained after calcination. The hierarchical structures of porous nanospheres within macroporous structures or on nanofibres are of potential interest to researchers in nanomaterials, porous polymers, supported catalysis and controlled delivery.