We have studied the conformation of a polymer brush in equilibrium wit
h a solvent that is subject to a shear flow. The interplay between the
polymer brush and the hydrodynamic flow of the solvent has been model
ed, with simple but largely justifiable approximations. The main techn
ique used in our study is a Monte-Carlo simulation algorithm that is d
istinct from many standard numerical methods used in studies of polyme
r brushes in that it combines an off-lattice description of polymer br
ushes-the Edwards Hamiltonian-with a modification of the standard Metr
opolis Monte-Carlo transition probability to take into account the eff
ective force acting upon the polymer molecules by the moving solvent.
The conformation of the polymer brush, the configurations of each indi
vidual chain in particular, is investigated in detail. It is found tha
t the significant response of the brush to the solvent shear flow mani
fests principally in the form of the chain tilting toward and stretchi
ng along the direction of the flow, whereas the overall conformational
properties, such as the averaged local monomer density, and the linea
r span of the brush in the direction normal to that of the flow remain
essentially unaffected by the flow. Such response can be understood b
oth qualitatively and semiquantitatively in terms of a notion of the m
echanical balance of the different physical forces involved, which was
used in the theory of Rabin and Alexander (Rabin, Y.; Alexander, S. E
urophys. Lett. 1990, 13, 49). The relevance of our study to some recen
t experiments is briefly discussed.