Segment distribution of the micellar brushes of poly(ethylene oxide) via small-angle neutron scattering

Coronal structures of the micelles spontaneously formed in water by poly(ethylene oxide)-b-polybutadiene (PEO-PB) were investigated using small-angle neutron scattering (SANS). Selective deuterium labeling of the hydrophobic PB block was employed to enhance the neutron scattering contrast between the PEO and PB segments for subsequent structural characterization of their micelles. Analyses of the core- and corona-contrast SANS data based on the intramicellar interference factors led to determination of the segment density profiles of the micellar PEO brushes. Both spherical and cylindrical brushes proved to have coronal layers that are best described in form by a concave concentration profile. The results are consistent with the view that the PEO segments, despite favorable interactions with water molecules, are significantly accumulated near the hydrophobic interface, possibly due to the effect of the strong incompatibility of PB and water.