Quasi-elastic light scattering from gels

Tanaka, Hocker, and Benedek first realized this essential nature of gds and developed a theory of the dynamics of gel networks [16]. According to their theory the quasi-elastic light scattering from gel networks became one of the standard methods of studying polymer gels. Here we briefly outline the theory of the dynamics of gels. 

Current theories for the dynamic fluctuations and kinetics of polymeric gel swelling are reviewed. The cooperative diffusion constant can be determined either from quasi-elastic light scattering experiments or from the swelling kinetics of spherical or cylindrical gels. The influence of the structure and ionization degree of the network on the cooperative diffusion constant is discussed. 

These examples show that condensation can be tailored via complexation and hydrolysis. Gels are obtained in the presence of an excess of water and for small values of x (x 0.3, h > 10). Clear sols are obtained when Ti(OnBu)4 is hydrolyzed in the presence of acetylacetone. The mean hydrodynamic diameter of colloidal particles was measured by quasi-elastic light scattering. It appears to increase from 2 to 40 nm as the hydrolysis ratio increases from h = 1 to ft = 4 for X = 0.3). It decreases from 40 to 4 nm when the amount of acetylacetone increases from x = 0.3 to x = 1 (for ft = 4) [28]. 

In this review of work at the Institute for Polymers and Organic Solids at UCSB, we summarize the results obtained from spectroscopic studies, quasi-elastic light scattering and field induced birefringence of dilute solutions. We then turn to more recent studies which focus on gels made up of networks of the rodlike molecules. 

This equation of motion was derived and tested experimentally for the first time by Tanaka et al. on polyacrylamide-water gels. From quasi-elastic light scattering and permeation and uniaxial compression experiments, they determined the order of magnitude of the three parameters D, pf, and M. They found that the ratio M/pf is close to the measeured D values. 

---