Diblock copolymers adsorbed at a water-oil interface

We probe the conformation of a diblock copolymer layer adsorbed at the surf ace of water-in-oil emulsion droplets at various concentration of a molecul ar surfactant. The diblock copolymer is made of a hydrophobic polybutadiene part linked to a hydrophilic polyethylene oxide one. The measure provides the equilibrium thickness of the polymer layer that is obtained with two di fferent techniques, i.e. dynamic light scattering and force measurements. T he structure of the layer is shown to change from a "mushroom" conformation in which the adsorbed chains form independent Gaussian coils to a conforma tion where they interact and extend in the continuous phase. The transition from one regime to the other is progressive as the ratio surfactant/polyme r bulk concentration varies.