  We present Monte Carlo computer simulations for melts of semiflexible
randomly knotted and randomly concatenated ring polymers on the fcc lattice and
in slit confinement. Through systematic variation of the slit width at fixed
melt density, we first explore the influence of confinement on single-chain
conformations and inter-chain interactions. We demonstrate that confinement
makes chains globally larger and more elongated, while enhancing both contacts
and knottedness propensities. As for multi-chain properties, we show that
ring-ring contacts decrease with the confinement, yet neighbouring rings are
more overlapped as confinement grows. These aspects are reflected on the
decrease of the links formation between pairs of rings. The results suggest
that confinement can be used to fine-tune the mechanical properties of the
polymer network. In particular, confinement biases the synthesis of networks
that are softer to mechanical stress. Finally, in connection with a previous
study of us and recent simulations on two-dimensional polymer melts, our
findings suggest that entanglements in polymer melts arise from pairwise
ring-ring links alone.
