  We use lattice-Boltzmann molecular dynamics (LBMD) simulations to study the
compression of a confined polymer immersed in a fluid and pushed by a large
spherical colloid with a diameter comparable to the channel width. We examined
the chain's deformation with both purely repulsive and weakly attractive
Lennard-Jones (LJ) potentials applied between the monomers. The sphere's
velocity was varied over 3 orders of magnitude. The chain is in a non-dense
state at low pushing velocities for both repulsive and attractive monomer
interactions. When the velocity of the spherical colloid exceeds a threshold
$v^*$, the back end of the chain transitions to a high density state with low
mean square monomer displacement (MSD) values. The front end, however, remains
in a non-dense state with high MSD indicating a pseudo two-state coexistence.
This crossover is also revealed through volume per monomer and MSD as a
function of the sphere's velocity. We also studied polymer dynamics by
investigating folding events at different times.
