Effect of chemical modification on hydrolysis and condensation reaction of zirconium alkoxide

Chemical modification effect of acetic acid was examined to control the hydrolysis and following condensation reaction of zirconium alkoxide. When acetic acid was added to zirconium alkoxide solution, acetic acid coordinated to a zirconium alkoxide to form a stable bidentate chelating compound if molar ratio of acetic acid to zirconium alkoxide (here after abbreviated as R-A) was less than two. In the case of simultaneous addition of acetic acid and water into a zirconium alkoxide solution, acetic acid immediately reacted with alkoxide. Water reacted with residual functional alkoxy groups to proceed the following condensation. Changing the degree of chelating the acetic acid to a zirconium alkoxide led to the control of the hydrolysis and condensation by decreasing the alkoxy groups of zirconium alkoxide. Polymeric transparent monolithic gels could be successfully prepared in the range from R-A = 1 to R-A = 1.5, and from R-W = 1 to R-W = 1.5 (here R-W means molar ratio of water to zirconium alkoxide), respectively.