  The effect of excluded volume interactions on the structure of a polymer in
shear flow is investigated by Brownian Dynamics simulations for chains with
size $30\leq N\leq 300$. The main results concern the structure factor $S({\bf
q})$ of chains of N=300 Kuhn segments, observed at a reduced shear rate
$\beta=\dot{\gamma}\tau=3.2$, where $\dot{\gamma}$ is the bare shear rate and
$\tau$ is the longest relaxation time of the chain. At low q, where anisotropic
global deformation is probed, the chain form factor is shown to match the form
factor of the continuous Rouse model under shear at the same reduced shear
rate, computed here for the first time in a wide range of wave vectors. At high
q, the chain structure factor evolves towards the isotropic equilibrium power
law $q^{-1/\nu}$ typical of self-avoiding walk statistics. The matching between
excluded volume and ideal chains at small q, and the excluded volume power law
behavior at large q are observed for ${\bf q}$ orthogonal to the main
elongation axis but not yet for ${\bf q}$ along the elongation direction
itself, as a result of interferences with finite extensibility effects. Our
simulations support the existence of anisotropic shear blobs for polymers in
good solvent under shear flow for $\beta>1$ provided chains are sufficiently
long.

Soft Condensed Matter;Statistical Mechanics