Polymer intrusion into narrow pores at the interface between a poor solvent and adsorbing and non-adsorbing surfaces

We report thermodynamic and conformational properties of collapsed polymer globules in a poor solvent close to adsorbing and non-adsorbing surfaces containing a cylindrical pore that is either smaller or larger than the coil size in bulk solution. Configurational Bias Monte Carlo simulations at infinite dilution were used for this purpose. We find that above the critical adsorption transition changing from good solvent to poor solvent conditions causes an increase of the partition coefficient due to cooperative monomer adsorption on the pore wall. Below the adsorption transition, the reverse effect is observed. The radius of gyration components as well as conformational (free) energies and entropies as a function of the chain centre of mass (CM) position along the pore axis reveal strong anomalies in the vicinity of the pore entrance. Below the adsorption transition, the dense globule in a poor solvent swells and deforms when penetrating the pore and recollapses once it is fully confined. Above the adsorption transition in solvents above and below the Θ-point, minima occur in the free energy at chain CM positions just in front of the pore entry causing a barrier upon pore penetration. Upon approaching the small pore from the bulk poor solvent region, the chain conformational entropy and energy run through a maximum below and above the adsorption transition.