Chemical Modification of Cellulose Acetate with Titanium Isopropoxide

Abstract

This study describes the chemical modification of cellulose acetate (CA) using titanium isopropoxide (TiP) in a sol-gel process for the formation of an organic/inorganic hybrid (OIH) material. The hydrolysis and condensation reactions that characterize this process result in CA cross-linking and formation of inorganic oxide particles. TiP-modified CA gels and membrane materials are characterized by solubility and swelling measurements, Fourier transform infrared spectroscopy and nuclear magnetic resonance spectroscopy, thermogravimetric analysis, differential scanning calorimetry (DSC) and ultrasonic time-domain reflectometry. Whereas the solubility of the CA significantly decreased with increasing TiP exposure consistent with high levels of cross-linking, unambiguous spectroscopic evidence for cross-linking could not be determined. In addition, DSC measurements indicated no significant change in CA glass-transition temperature as a function of TiP exposure. On the other hand, TiP treatment dramatically improved the creep behavior of treated porous CA membranes, whereby the total compressive strain decreases by as much as 70% relative to the untreated materials. Overall, the results suggest that TiP treatment can be used as a post-fabrication processing step to create OIH-modified CA membranes with improved chemical and mechanical stability.