The colloidal properties of polystyrene-6-poly(metal methacrylate) AB diblock ionomers are studied by size-exclusion chromatography (SEC). In solvents selectively good for the polystyrene blocks, the ionomers form species that show the characteristics of reverse micelles and that are very stable in solution. This high stability allows the use of SEC for the complete characterization of this micellelike system. SEC experiments show that there is no apparent micelle dissociation-association equilibrium taking place within the time scale of a few days. By combining intrinsic viscosity and SEC measurements, molecular weights, molecular weight distributions, aggregation numbers, and hydrodynamic radii of the micelles have been determined. The effects on these parameters of varying the lengths of the polystyrene or the ionic blocks are investigated systematically. The presence of spherical micelles is confirmed by electron microscopy. For some of the systems, the aggregation numbers are compared with those determined by small-angle X-ray scattering in the solid state.

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The rheological properties of diblock ionomers based on polystyrene-b-poly(sodium methacrylate) (PS-b-PMANa) were studied. Comparing the melt rheology of the block ionomer with that of the star-shaped polymer, it was seen that the viscoelastic properties of the diblock ionomer could be attributed to the same molecular motion as those of star polymers, since the PS-b-PMANa forms micelles that persist even in the melt because of the strong association of the ionic blocks. The dynamic viscoelastic functions of the block ionomer suggested the existence of an additional relaxation at low frequencies. The additional relaxation was thought to be due to the thermal rotational diffusion of the micelles, restricted by the retraction process of polystyrene block chains. The estimated relaxation time was in good agreement with that found experimentally. An alternative explanation of the additional relaxation was based on the possible action of the micelles as a filler, since the rheological behavior of the diblock ionomer at low frequencies was similar to that of a suspension.

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