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(et hylene 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 th e PEO and PB segments for subsequent structural characterization of their m icelles. Analyses of the core- and corona-contrast SANS data based on the i ntramicellar interference factors led to determination of the segment densi ty profiles of the micellar PEO brushes. Both spherical and cylindrical bru shes proved to have coronal layers that are best described in form by a con cave concentration profile. The results are consistent with the view that t he PEO segments, despite favorable interactions with water molecules, are s ignificantly accumulated near the hydrophobic interface, possibly due to th e effect of the strong incompatibility of PB and water.