The occurrence of lyotropic mesophases in solutions of various polysaccharides, such as non‐ionic schizophyllan and anionic xanthan, was demonstrated by means of polarizing microscopy. In contrast to synthetic polymers where the formation of liquid‐crystalline phases has been attributed to the presence of mesogenic groups in the main‐ or side‐chain, here a helical structure is a prerequisite for the formation of mesophases. It was then shown that the stability of the helix is dependent on the chemical structure and the arrangement of the side groups. Apart from their optical anisotropy, some lyotropic mesophases are distinguished by extraordinary viscous and elastic properties (e.g. maximum behaviour of viscosity). The viscoelastic material functions were determined by rheological methods. A precise characterization of the chemical and steric microstructure should provide information on the ability of polysaccharides to form mesophases. Determination of the chemical microstructure (quaternary polymer) was carried out by 1H NMR spectroscopy after ultrasonic degradation. Low‐ and multi‐angle laser light scattering were employed for the determination of the steric microstructure which indicates an expanded semi‐flexible structure. The experimental results were compared with those from molecular modelling.

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 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.