Systematic microcanonical analyses of polymer adsorption transitions

Area of Science:

• Polymer physics
• Statistical mechanics
• Surface science

Background:

• Polymers adsorbing onto surfaces undergo conformational transitions.
• The thermodynamic limit behavior of these transitions is well-understood as continuous.
• Finite-length effects and surface interactions are crucial for understanding real-world systems.

Purpose of the Study:

• Investigate the caloric properties of polymer adsorption transitions near attractive substrates.
• Analyze the role of surface-entropic effects in finite polymer chains.
• Characterize the nature of the adsorption transition for finite-length polymers.

Main Methods:

• Detailed microcanonical analyses of densities of states.
• Extensive multicanonical Monte Carlo computer simulations.
• Examination of microcanonical entropy and temperature as functions of energy.

Main Results:

• Microcanonical entropy is convex in the transition regime for short chains and strong attraction.
• Finite-length polymers exhibit a first-order-like adsorption transition with coexisting adsorbed and desorbed phases.
• A decrease in microcanonical temperature with increasing energy accompanies the transition.

Conclusions:

• Surface-entropic effects are significant for finite adsorbing polymers.
• The adsorption transition for finite chains deviates from the continuous transition observed in the thermodynamic limit.
• The observed temperature decrease is a characteristic physical effect relevant for finite systems.