Effect of confinement on coil-globule transition

Area of Science:

• Polymer Physics
• Thermodynamics
• Statistical Mechanics

Background:

• Understanding polymer behavior in confined environments is crucial for materials science and nanotechnology.
• Previous studies have explored polymer confinement, but the interplay of solvent conditions and wall separation requires further investigation.

Purpose of the Study:

• To investigate the equilibrium thermodynamic properties of a linear polymer chain confined between two parallel walls.
• To analyze the influence of varying wall separation (D) and solvent conditions on polymer chain dimensions and phase transitions.
• To characterize the force exerted by the walls on the confined polymer.

Main Methods:

• Employed series analysis and exact enumeration techniques for precise calculations.
• Calculated key polymer properties including end-to-end distance and density distribution profile.
• Investigated the polymer's phase behavior by analyzing the theta-temperature variation with wall separation.

Main Results:

• Observed non-monotonic behavior in the end-to-end distance as a function of wall separation (D).
• Identified a specific wall separation (D*) where the polymer density profile exhibits a maximum.
• Found that the polymer collapse transition occurs at a higher temperature compared to bulk conditions (2D and 3D).
• Demonstrated re-entrance behavior in the theta-temperature with changing D.

Conclusions:

• Confinement significantly alters polymer thermodynamic properties and phase transitions.
• The observed re-entrance phenomenon suggests complex interactions between polymer, solvent, and confining walls.
• Results provide fundamental insights into polymer behavior in nanoscale confined geometries.