  Monte Carlo simulations are used to study the conformational properties of a
folded semiflexible polymer confined to a long channel. We measure the
variation in the conformational free energy with respect to the end-to-end
distance of the polymer, and from these functions we extract the free energy of
the hairpin fold, as well as the entropic force arising from interactions
between the portions of the polymer that overlap along the channel. We consider
the scaling of the free energies with respect to varying the persistence length
of the polymer, as well as the channel dimensions for confinement in
cylindrical, rectangular and triangular channels. We focus on polymer behaviour
in both the classic Odijk and back folded Odijk regimes. We find the scaling of
the entropic force to be close to that predicted from a scaling argument that
treats interactions between deflection segments at the second virial level. In
addition, the measured hairpin fold free energy is consistent with that
obtained directly from a recent theoretical calculation for cylindrical
channels. It is also consistent with values determined from measurements of the
global persistence length of a polymer in the backfolded Odijk regime in recent
simulation studies.
