KINETICS ON THE SOL-GEL PROCESS OF THE MODIFIED CU ETHOXIDE

Kinetics of the reactions and gelation of modified Cu ethoxide, Cu2(OR)2(OAC)2(HORE)4, with H2O were measured. When water was added to the methoxethanol solution of the modified Cu ethoxide, the first reaction was substitution reaction of H2O for methoxyethanol ligand in Cu2(OR)2(OAC)2(HORE)4. The substitution reactions lead to forming another dimer with larger spacing between Cu atoms, then alkoxy groups were hydrolyzed. Finally, hydrolyzed dimers were formed and polymerized into a transparent gel. With the transformation of a primary dimer, Cu2(OR)2(OAC)2(HORE)4, to a hydrated or hydrolyzed dimer, Cu2(OX)2(OAC)2(H2O)2(HOX)4 (X = H or R), with large spacing between Cu atoms, a 380 nm absorption band disappeared. Through measurements of changes in absorbance at 380 nm and gelation time with different H2O content, kinetic expressions about the reactions and gelation for the sol-gel process of the modified Cu ethoxide were derived. The derived relations are in a good agreement with the experimental results. It is concluded from the kinetic relationships that the effect of H2O content is to change the properties of the solvent involved.