Comparative study of the porosity induced by CTAB and Tween as silica templates

In this study doped-silicon polymers were synthesized using the non-ionic surfactant Tween 80 as template. The obtained material was compared with silicates doped with the cationic surfactant CTAB. Both materials were synthesized by sol–gel process with tetraethoxysilane (TEOS) as silicon source. In the synthesis procedure reported herein the main difference to previous reports is that the obtained solids were dried smoothly at 55 °C avoiding surfactant calcination. The aim of this work is to obtain new biomaterials appropriate to be used for encapsulation devices in which the surfactant kept within the silica network has two roles: (1) to improve the mechanical resistance in drying–swelling processes preventing crack formation, (2) to hold and protect the encapsulated molecules keeping intact their bioactivity during TEOS polymerization. Structural features such as pore size and surface topology were studied by means of N2 adsorption, X-ray diffraction and AFM microscopy. The influence of surfactant net charge and molecular shape on the materials obtained is discussed.