The association behavior of polyelectrolyte block copolymers in aqueous solution as a function of polymer and salt concentration is investigated for poly(ethylethylene-b-styrenesulfonic acid) (PEE-PSSH). This copolymer combines a soft hydrophobic block with a highly charged polyelectrolyte block that allows direct dissolution in aqueous solutions to investigate micellization under equilibrium conditions. Increasing polymer and salt concentration leads to the fusion of polyelectrolyte micelles into vesicles and fractal toroid-micronetworks. Association structures were characterized by static light scattering (SLS), small-angle neutron scattering (SANS), transmission electron microscopy (TEM), and atomic force microscopy (AFM). At high salt concentrations the solution phase separates into a dilute micellar phase and a concentrated gel phase.

The quality of life partially depends on the ability to maintain the transportation of goods and people in an efficient and reliable fashion, even under difficult climatic conditions. A well-known problem at low temperatures is the filter blockage of diesel fuel. Fuel oils contain alkanes that precipitate at low temperature as large crystals or spherulites of wax in such a way as to form gels. Thereupon the fuel loses its ability to flow and the transportation system falters or is stopped. The lowest temperature at which the fuel will still flow is known as the pour point. As the temperature approaches that of the pour point, difficulties emerge in transporting the fuel through lines and pump. Furthermore, wax crystals can plug screens and filters at temperatures above the pour point; the so-called cold filter plugging point. To combat this behavior various additives have been developed to depress the pour point or to decrease the size and alter the shape of the wax crystals; e.g., smaller sized crystals are less likely to clog either screens or filters. This paper reports on the use of a crystalline-amorphous diblock copolymer that performs, in its selfassembled state, as an efficient nucleator for the wax in middle distillate fuels.

Amphiphilic block copolymers consisting of a hydrophobic block of hydrogenated polybutadiene and a partly sulfonated polyelectrolyte block of poly(styrenesulfonate) are effective stabilizers in emulsion polymerization. At low relative amounts of block copolymer (0.4 wt % as a fraction of monomer weight) and salt-free conditions, well-defined and stable latices with particle diameters of ca. 100 nm and solid contents of 20 wt % are obtained. This high stabilization efficiency of optimized block copolymer systems enables the formulation of latex systems with a relatively low remaining polarity in solid films and offers new interesting model systems with exclusively electrosteric stabilization. A comparison of polymerization in high or low ionic strength solution and the variation of the degree of sulfonation of the poly(styrenesulfonate) block shows an optimum stabilization of the latices at low ionic strength during polymerization. Fully sulfonated polymers systems presumably show a molecular orientation perpendicular to the particle surface, whereas 50% sulfonated species take on a traillike conformation along the surface, which is explained by remaining hydrophobic interactions. Due to this multiple surface particle contacts, the application of partly sulfonated polymers leads to more effective stabilization. At higher stabilizer concentrations, aggregates are found, which can be redispersed by ultrasonification or addition of low molecular weight surfactant solution.

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