Surface adsorption and collapse transition of a linear polymer chain in three dimensions

A phase diagram for a surface-interacting long flexible polymer chain in a poor solvent where the possibility of collapse exists is calculated using a n exact enumeration method. A model of a self-attracting self-avoiding walk on a simple cubic lattice was considered and up to 16 steps in series were evaluated. The phase diagram indicates that while the boundary between the expanded and collapsed phases is straight in the bulk, it exhibits a bend in the surface resulting in two adsorbed collapsed phases separated by an a dsorbed expanded phase. This is attributed to competition between the entro pic fluctuations and effects due to monomer-monomer attraction.