Figure 4. dE/dfi vs. Q for independently calibrated SAXS and SANS data from 3.7k/40k PS-b-PFOA blockcopolymer micelles in CO2

intensity, as the SLD for PS increases by a factor of ~6 on deuteration. A fourth adjustable parameter was introduced in the model, to account for the fraction of added oligomer solubi-lized in the core of the micelle (a). The results [6] indicate that virtually all of the added oligomer goes in the core (a~ 100%), independently of oligomer concentration and isotopic content. Figure 5 shows how the forward SANS cross section increases by over an order of magnitude as the particle size and aggregation number swell to accommodate the polystyrene solubilized in the core. For runs performed at 40 oC, i.e. higher solvent density, as compared to 65 C, the number of molecules per micelle (Nagg) decreases to about half of what was observed at 65 OC. This can be understood [6] as an increase in surface area of block copolymer in contact with the solvent, concomitant with the increase in solubility of the block copolymer at higher density. The data also indicate that an increase in solvent density

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