TENSION OF POLYMERS IN A STRIP

We consider polymers, modelled as self-avoiding chains, confined on a strip defined on the square lattice with spacing a in the (x, y) plane , limited by two walls which are impenetrable to the chains and locate d at x = 0 and x = m. The activity of a monomer incorporated into the chain is defined as z = exp(beta mu) and each monomer adsorbed on the wall, that is, located at sites with x = 0 or x = m, contributes with a Boltzmann factor omega = exp(-beta epsilon) to the partition functio n. Therefore, epsilon < 0 corresponds to walls which are attractive to the monomers, while for epsilon > 0 the walls are repulsive. In parti cular, we calculate the tension between the walls, as a function of m and omega, for the critical activity z(c), at which the mean number of monomers diverges (the so called polymerization transition). For omeg a > 1 --> 1.549375..., the tension on the walls is repulsive for small values of m, becoming attractive as m is increased and finally becomi ng repulsive again. As omega is increased, the region of values of m f or which the tension is attractive grows.