Journal of Physical Chemistry, Vol.100, No.18, 7603-7609, 1996
Structure of Block-Copolymers Adsorbed to Perfluorocarbon Emulsions
We have used small-angle neutron scattering (SANS) to study the structure of block copolymers (Poloxamer 188, Poloxamer 407, and Poloxamine 908) adsorbed at the perfluorodecalin-water interface in a submicrometer emulsion system. The data were analyzed using an established transform method to yield the polymer volume fraction profile as a function of distance from the oil-water interface. There was a good correlation between the derived adsorbed amounts of polymer and those measured experimentally, and between the adsorbed layer dimensions from SANS and earlier light scattering measurements. The profiles are consistent with a model in which the poly(propylene oxide) blocks are bound at the interface and the poly(ethylene oxide) blocks are largely present as tails. An electrolyte (sodium chloride at 0.1-0.2 M concentration) was found to significantly reduce the bound fraction of Poloxamer 188, and caused a significant increase in the extension of the adsorbed layer, without affecting the amount of polymer adsorbed.