Characterization of ultrahigh molar mass, water‐soluble, cationic polyelectrolytes

Abstract

Four different cationic polyelectrolytes were investigated, which are used as flocculating agents in the dewatering of sediments from Hamburg harbour. The chemical structures of these polyelectrolytes were characterized by means of IR and 13C NMR spectroscopy. The substances concerned are the two copolymers of acrylamide formed with acrylate and methacrylate esters, and the homopolymers of these esters. The charge density was determined with the aid of titrimetric methods and quantitative evaluation of IGATED 13C NMR spectra. Determination of the molar mass and steric characterization were carried out by multi‐angle laser light scattering. In order to resolve the experimental problems which arise especially during light scattering in water‐soluble cationic systems, a special method of sample preparation has been devised to remove impurities, which will be described in detail. This method involves the combination of filtration and ultracentrifugation. Evaluation of the light scattering data provided the values for the molar mass Mw′ the second virial coefficient A2 and the radius of gyration <R2G>0,5Z, which also gives information about the solution structure. By comparing the curve of the scattering function extrapolated to zero concentration with model curves and with the aid of the a exponent of the [η]‐M‐relationship, it can be seen that the polyelectrolyte has a highly expanded coil structure in salt solution. This can be primarily attributed to the steric influence of the side groups.