Unexpectedly normal phase behavior of single homopolymer chains

Area of Science:

• Polymer Physics
• Statistical Mechanics
• Soft Matter Physics

Background:

• Understanding polymer phase behavior is crucial for materials science and biophysics.
• The phase diagrams of polymers, particularly single flexible chains, are complex and influenced by inter-monomer interactions.
• Previous studies often focused on specific interaction ranges or simplified models.

Purpose of the Study:

• To investigate how the range of attractive monomer-monomer interactions affects the phase diagram topology of a single flexible homopolymer chain.
• To compare the phase behavior of a single polymer chain with that of a polymer solution under similar interaction conditions.
• To explore the universality of phase diagram topologies between polymer systems and colloidal dispersions.

Main Methods:

• Utilized Monte Carlo simulations to model a single flexible homopolymer chain.
• Implemented an attractive square well interaction model between monomers with varying interaction ranges.
• Analyzed the equilibrium phase diagrams for both the single chain and corresponding polymer solutions.

Main Results:

• A critical range of attraction was identified, above which vapor, liquid, and solid phases appear in the phase diagram.
• Below this critical range, the liquid-vapor transition disappears from the equilibrium phase diagram for both single chains and solutions.
• The observed phase diagram topology changes are analogous to those seen in colloidal dispersions.

Conclusions:

• The range of attractive square well interactions fundamentally alters the topology of polymer phase diagrams.
• The interplay between enthalpy and conformational entropy in polymers can yield phase diagram topologies similar to those driven by enthalpy and translational entropy in simple liquids.
• This study highlights a potential universality in the phase behavior of different soft matter systems.