ANALYTICAL ULTRACENTRIFUGATION OF GELS

Analytical ultracentrifugation is a powerful tool for the determinatio n of thermodynamic, elastic and molecular parameters and structural pr operties of gels. Although gelling systems are an important class of m ixtures, only a few researchers have studied their properties by means of analytical ultracentrifugation. This might be due to the extreme e xperimental difficulties concerning the detection of the polymer conce ntration in turbid gels, adhesion problems, etc. Nevertheless, the pot ential benefit of such experiments has led to several investigations i n this field during recent pears. These resulted in the introduction o f a theoretical treatment of the sedimentation of even multicomponent gels and an improved experimental set-up which allows the characteriza tion of a gel/solvent system in a limited concentration range in a sin gle sedimentation equilibrium experiment. For microgels prepared and c rosslinked in emulsions, an interesting rapid sedimentation velocity t echnique is available for their characterization. This review article describes the capabilities of the experimental method and what has bee n achieved with it in the past. Furthermore, it gives an outlook on ap plications which may be possible in the future.