  Molecular Dynamics simulations of a coarse-grained bead-spring model of
flexible macromolecules tethered with one end to the surface of a cylindrical
pore are presented. Chain length $N$ and grafting density $\sigma$ are varied
over a wide range and the crossover from ``mushroom'' to ``brush'' behavior is
studied for three pore diameters. The monomer density profile and the
distribution of the free chain ends are computed and compared to the
corresponding model of polymer brushes at flat substrates. It is found that
there exists a regime of $N$ and $\sigma$ for large enough pore diameter where
the brush height in the pore exceeds the brush height on the flat substrate,
while for large enough $N$ and $\sigma$ (and small enough pore diameters) the
opposite behavior occurs, i.e. the brush is compressed by confinement. These
findings are used to discuss the corresponding theories on polymer brushes at
concave substrates.
