Deformations of One Tethered Chain in Strong Flows

1) We describe first the non-uniform stretching of one long flexible tethered chain ( N monomers) immersed in a good solvent moving at velocity V . In strong flows the extension L is predicted to increase quadratically with velocity ( L ∼ N 3 V 2 ). The chain can be pictured as a sequence of blobs of size y decreasing as x −1 ( x being the distance measured from the chain end). 2) We extend this analysis to the stretching of a few grafted chains ("mushroom" regime) when a shear flow (rate s ) of the solvent is imposed near the wall. Here the elongation L ∼ N 3/2 s 1/2 and the blob size decreases as y ∼ x −1/2 . 3) Finally we discuss a chain confined in a slit. We find L ∼ N 4/3 V 1/3 and blobs sizes y ∼ x −3/4 . In all these cases, the deformation is progressive and we expect no sharp coil stretch transitions.