Templating by the Immersion Method

Bulk titania wet gels, prepared by hydrolysis of TNB in ethanol solution with addition of EACAC using acid catalyst, were aged at 90°C for 1 h, and the wet gels were immersed into an ethanol solution of surfactants, CTAC oxBTAC, at 60°C for 1 h, and dried at 90°C for 24 h (surfactant-modified gels) [28, 29]. The dried gels were annealed at 500°C for 2 h. 

Polymer-templated titania gels were also prepared. Monolithic titania wet gels were immersed in a solution of hydrophilic polymers, triblock-copolymer, poly(ethylene oxide)-poly(propylene oxide)-poly (ethylene oxide) [Pluronic, M.W. 12,600, Sigma Chemical Co.] or a PEG (M.W. = 4,000 and 20,000, Sigma Chemical Co.), under an atmospheric pressure before drying [29]. The dried gel films were annealed at 500°C for 2 h. 

The bulk gels and gel films templated with hydrophobic polymer were prepared by the following Immersion methods [33]. 

Monolithic gels were obtained in 20 min at room temperature. After aging at 50°C for 1 h, the wet gels were immersed into polystyrene solution. Immersion conditions are the following the concentration of polystyrene (PS, M.W. 230,000, Aldrich Chemical Co.) was 0.1-11 g in 30 ml of THF, and immersion time was 1-100 h. The wet gels were also aged and dried without immersion to obtain the xerogels. 

---