Short-length polymers selectively end-capped with a metal carboxylato group at both ends, i.e. metal carboxylato-telechelic polymers, exhibit an unusual shear-thickening behaviour in apolar solvents, depending on the main experimental parameters that control the ion-pair association, such as metal cation, concentration and temperature. In contrast to the non-ionic precursors, metal carboxylato-telechelics are indeed responsible for a marked increase in the solution viscosity in a range of shear rates between 0.1 and 1000 s -'. The shear-rate dependence of the solution viscosity has been analysed in a close relationship to metal counterion, polymer concentration, temperature and addition of polar compounds to the apolar solvent. As a rule, the dilatant behaviour depends strongly on the formation of polymer aggregates in relation to the mutual interactions of the ion pairs. A consensus is now emerging on the origin of the shear-thickening effect, which should be found in inter-aggregate associations rather than in a transition from intramolecular to intermolecular associations of the individual chains.

The salt-induced chromatin condensation in chicken erythrocyte nuclei is studied by differential scanning calorimetry (DSC). The degree of chromatin condensation is measured for condensation induced by monovalent, divalent, trivalent, or tetravalent cations and by a mixture of sodium and magnesium. These last two cations show an evident competition effect. Salt-induced chromatin condensation is shown to be an entropy-driven process. A simple model of chromatin based on the polyelectrolyte counterion condensation theory is used in order to compute the charge neutralized by the cations in each chromatin domain. The degree of chromatin condensation is shown to be related to the weighed sum of the square of the phosphate charge of each domain. The model predicts the salt and the chromatin concentration dependence of the condensation and the effect of H1 removal.

Influence of both polymer molecular weight and concentration, and solution preparation on the SAXS profile of ω- and α,ω-metal sulfonato and carboxylato polystyrenes in toluene has been investigated. For sulfonated polymers, position of the ionic peak obeys a general law which allows the phase morphology to be predicted. Ionic end-groups are phase-separated into small multiplets which act as physical crosslinks. Size of the multiplets does not depend on polymer molecular weight and concentration. Multiplets are homogeneously distributed throughout the polymer matrix, and organized in a liquid-like manner. Difunctional samples obey the same general behavior but only above a critical concentration which depends on the chain molecular weight. Although the position of the ionic peak is independent of the sample preparation, shape and intensity are clearly related to the large-scale heterogeneity of solutions

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A new class of Halato-Telechelic Polymers (HTP) has been prepared. Prelerninary SAXS results on a, wcarboxy poly (tert. butyl acrylate)~ end-neutralized with Ba, Mg and Na alkoxides show that the "ionic peak" usually observed in ionomers goes undetected. In contrast, a series of peaks appear at very low angles corresponding to Bragg spacings from 70 to 14 nm. The successive peak positions are consistent with a hexagonal structure. In order to confirm this new experimental evidence, the effects of several parameters on the SAXS patterns have been investigated. Samples of various counterions and molecular weigths have been prepared under different conditions. Morphological changes have also been analyzed in the presence of a non-polar solvent (toluene).