Macromolecules, Vol.32, No.5, 1528-1533, 1999
Time-resolved dynamic light scattering studies on gelation process of organic-inorganic polymer hybrids
The gelation process of organic-inorganic polymer hybrids has been investigated by time-resolved dynamic Light scattering. The polymer hybrids were prepared by sol-gel reaction of tetramethoxysilane (TMOS) in the presence of organic compounds, such as poly(dimethylacrylamide) (poly-DMAA) or DMAA monomers. The gelation threshold was characterized by (1) the drastic change in the scattered intensity and an appearance of a speckle pattern during the course of gelation, (2) a power-law behavior of the time-intensity correlation function (ICF), g((2))(tau) - 1, where tau is the decay time, (3) the appearance of a long tail in the characteristic decay time distribution function, and (4) the reduction of the initial amplitude of ICF. The gelation process of TMOS was found to be strongly dependent on the presence of either poly-DMAA or DMAA monomers. In the presence of poly-DMAA, the,gelation was accelerated. On the other hand, it was decelerated when DMAA monomers were present in the system. On the basis of this experimental evidence, we concluded that hydrogen bonding between the amide groups in DMAA and silanol groups in TMOS plays an important role in the gelation kinetics of these hybrids.