HomeInhenyeriyavol. 2 no. 1 (2001)

The Pre-Gelation State of an aluminium Based Inorganic Polymer

Julius B. Maridable | Dianne E. Wiley

Discipline: Engineering



The synthesis of an aluminium-based, inorganic polymer was anchored on the hydrolysis of aluminium tri-sec-butoxide in sec-butyl alcohol and the condensation of the partially hydrolysed products to form the polymeric network. By skillfully manipulating the preparation technique, the precipitation of aluminium oxy-hydroxides and the formation of colloidal particulates were avoided. In this study, the pre-gelation stage of the aluminium based inorganic polymer was investigated using four techniques: potentiometry, infrared spectroscopy (FTIR), nuclear magnetic resonance (NMR) and small angle x-ray scattering (SAXS). For acid catalysed reactions, the optimum acid and water concentrations for the reduction of gelation time were between 1.0 and 2.0 mole acid per mole alkoxide and between 2.0 and 3.0 mole water per mole alkoxide. The sols produced were highly acidic and viscous. Potentiometric results showed that pH values which successfully prevented precipitation of Al(OH)3 during the early stages of the reaction were between 6 and 9. FTIR revealed a narrowing of the Al-OH stretching band at 3500 cm-1 and the appearance of an Al-0 band at 820 cm-1 as the reaction progressed. SAXS measurements of the sols gave an average radius of gyration of 89A, indicative of large swollen molecules. Solution 27 Al NMR demonstrated that species with tetrahedrally coordinated aluminium dominated the early stages of the reaction.