Langevin dynamics simulation on optimal conditions for large and stable loops of adsorbed homopolymers on substrates

Adsorption of polymer chains on a solid surface is a universal interfacial behavior. Loops in the adsorbed chains are considered to exert a significant effect on the overall properties of a substrate-supported polymer film via entanglement with non-adsorbed chains in the film. In this work, the size and stability of loops formed by adsorbed homopolymer chains on an attractive substrate were studied by Langevin dynamics simulations. The size of loops decreases while the stability increases with increasing attraction strength of the substrate. In contrast, with an increase in the polymer concentration, the size of loops increases but the stability decreases. However, both the size and stability of loops increase with increasing chain length. Simulation results show that the optimal conditions for forming large and stable loops are long homopolymer chains, substrates with moderate attraction strength, and moderate polymer concentration. Large and stable loops can be formed by long homopolymers adsorbed on a substrate with moderate attraction at moderate polymer concentrations.