“Effect of anilines as a synthesis component on the hydrophobicity of silica”

A. C. TURALLAS, G. ROMANELLI, P. VÁZQUEZ

Como, Italia

Workshop; III Workshop Oxid Basic Materials; 2004

In the field of polymeric systems an important goal is to reinforce the polymer matrix and to improve mechanical and thermal properties. Inorganic additives are introduced into polymer systems as fillers or as reinforcing agents. Among the hybrid organic-inorganic powdered materials, the silica receives considerable interest because different degrees of hydrophobic/hydrophilic are determining its dispersion in the polymeric matrix. The synthesis and characterization of hybrid organic–inorganic powdered materials have received great attention in past years. These materials present properties related to the matrix as well as the organic phase, which can be combined in order to obtain new materials. The sol–gel method is an important route to prepare such materials using alkoxysilanes R-Si(OR)3 and tetraethylorthosilicate (TEOS) as precursors. The polycondensation of alkoxysilanes can be described in three steps: (i) hydrolysis, (ii) silanol condensation and (iii) silanol–alcohol condensation. The relative simplicity and versatility of the sol–gel process, when compared to covalent-bonding methods to obtain hybrid materials, associated with low cost, are responsible for its extensive utilization. The possibility of obtaining different physicochemical characteristics like surface area, particle shape and size, porosity and organic functionalization grade, are some advantages of this process [1-3]. However, a little change in the parameter conditions of the synthesis, like solvent, catalyst or silane amount, can produce great modifications in the final properties of the materials. In this context, the study of the synthesis conditions and the related resulting properties are very important to understand these systems [4]. The silica can have hydrophobic properties when its surface is functionalized. This process requires the presence of silanol groups at the surface. There are many types of silica differing in their surface properties, in particular, the density of silanol groups and the types of silanols (isolated, hydrogen bonded, geminal) vary by techniques of preparation of silica. The purpose of this investigation is to know the grafting process on silica prepared by sol-gel. The principle of the investigation work consists in comparing the grafting of anilines, with different active groups, on silica to obtain different degree of the surface hydrophobicity. For a better understanding of these solids, the characterization of the nature of the species was determined by FT-IR, XRD, DTA-TGA and surface area (SBET).