Silicon Chemistry 2: 157–165, 2003. C  2004 Kluwer Academic Publishers. Printed in the Netherlands. 157 Alkyl-glycoside surfactants in the synthesis of mesoporous silica ﬁlms Urˇ ska Lavrenˇ ciˇ c ˇ Stangar & Nicola H ¨ using Institute of Materials Chemistry, Vienna University of Technology, Getreidemarkt 9/165, A-1060 Vienna, Austria (Received 21 November 2002; accepted 15 August 2003) Key words: alkyl glycosides, IR spectroscopy, mesoporous silica, sol–gel, sugar-based surfactants, thin ﬁlms Abstract Alkyl glycosides were used as templating surfactants in the sol–gel processing of thin silica ﬁlms. The sols were made from a prehydrolyzed silicate solution with the addition of a glucoside or a maltoside surfactant. The sol–gel–xerogel transitions and the silica–sugar interactions were studied by IR ATR spectroscopy. The siloxane condensation rate in the silica/glycoside sol was considerably reduced compared to a pure silica system due to hydrogen bonding interactions between the silanols and the sugar head groups. Thin ﬁlms were deposited on silicon wafers and characterized by IR transmission, X-ray diffraction and TEM analysis. The size of the sugar head group had a large inﬂuence on the type of the mesophases formed. The use of the glucoside surfactant only resulted in temperature unstable lamellar phases, whereas the maltosides at low concentrations assembled in curved mesophases that were stable to template removal by extraction or calcination. Abbreviations: IR – infrared, ATR – attenuated total reﬂectance, XRD – X-ray diffraction, TEM – transmission electron microscopy, β -C 8 Glc – n-octyl β -D-glucopyranoside, β -C 10 Mal – n-decyl β -D-maltopyranoside, β -C 12 Mal – n-dodecyl β -D-maltopyranoside, TEOS – tetraethoxysilane, EtOH – ethanol, GL – glycosidic linkage. Introduction The synthesis of mesoporous silica-based materials with the help of ionic or non-ionic surfactants repre- sents a growing ﬁeld of research in the last decade. The discovery of this surfactant-templated approach [1] has paved the way to new materials with controlled porosity. Since then, a tremendous extent of research has been devoted to the preparation of mesostructured powders and thin ﬁlms, summarized in a review by Edler and Roser [2]. The preparation of thin ﬁlms re- quires the optimization of the parameters that govern the mesophase formation during evaporation-induced self-assembly [3, 4], such as deposition rate, ambient humidity, sol viscosity, and sol ageing time. The inﬂu- ence of these parameters is a result of several processes that compete in a very short period of time during thin- ﬁlm deposition: solvent evaporation, aggregation and organization of surfactant in the presence of siliceous species, and condensation of the silica host. In the present study, we have investigated the de- position of mesostructured silica ﬁlms prepared with commercially available sugar-based non-ionic sur- factants: n-octyl β -D-glucopyranoside (β -C 8 Glc), n- dodecyl β -D-maltopyranoside (β -C 12 Mal) and n-decyl β -D-maltopyranoside (β -C 10 Mal). These alkyl glyco- sides belong to a new family of biodegradable, non- toxic surfactants that form supramolecular aggregates in polar solvents, e.g., water. The liquid crystalline phase behavior in water is well known for β -C 8 Glc [5, 6] and β -C 12 Mal [7, 8]. Our aim was to investigate their self-assembly capability in combination with a prehydrolyzed silicate solution by means of infrared (IR) spectroscopy, X-ray diffraction (XRD) and trans- mission electron microscopy (TEM). The latter two are standard and powerful techniques for the charac- terization of mesostructured powders and thin ﬁlms. On the other hand, IR spectroscopy has been applied only in a few works to characterize mesoporous sil- ica ﬁlms [9–13]. IR ATR spectroscopy is thought a convenient method to study the sol–gel process in situ during the solidiﬁcation of the ﬁlm-forming solution on the surface of the IR internal reﬂecting element [14]. We aimed to investigate the nature of the interactions