Polymer Bristles:  Adsorption of Low Molecular Weight Poly(oxyethylene)−Poly(oxybutylene) Diblock Copolymers on a Perfluorocarbon Emulsion

We report the results of a small-angle neutron scattering study into the structure of the adsorbed layers formed at the interface in a dilute perfluorodecalin-in-water emulsion by five short chain diblock copolymers of oxyethylene (OE) and oxybutylene (OB) (OE<INF>26</INF>OB<INF>13</INF>, OE<INF>29</INF>OB<INF>11</INF>, OE<INF>30</INF>OB<INF>7</INF>, OE<INF>27</INF>OB<INF>6</INF>, and OE<INF>58</INF>OB<INF>13</INF>). The results are discussed in the context of the Marques−Joanny−Leibler scaling description of block copolymer adsorption from selective solvents and provide an insight into the validity of the theory in the unusual limit of short chain lengths and small anchor blocks, close to the boundary between the buoy-dominated and the van der Waals−buoy regimes. The volume fraction profiles are best described by parabolic and, to a lesser extent, Gaussian functional forms. When the temperature was increased, the buoy blocks were found to contract toward the surface, giving rise to profiles that were more blocklike, in accordance with theoretical predictions by Wijmans and Zhulina (Macromolecules <BO>1993</BO>, 26, 7214).