Polyampholyte sequence controls the type of electrostatic coil-globule transition in good solvent

Area of Science:

• Polymer Physics
• Computational Chemistry
• Soft Matter Physics

Background:

• Polyampholytes are polymers with both positive and negative charges.
• Their conformational behavior is influenced by electrostatic interactions and solvent quality.
• Understanding sequence effects is crucial for predicting polymer properties.

Purpose of the Study:

• To investigate the conformational dynamics of globally neutral polyampholytes.
• To explore how monomer sequence affects electrostatically driven chain contraction.
• To analyze the coil-globule transition under varying electrostatic conditions.

Main Methods:

• Utilized coarse-grained molecular dynamics simulations.
• Examined polyampholytes with diblock, random, and alternating monomer sequences.
• Varied the solution Bjerrum length (lb) to modulate electrostatic interactions.

Main Results:

• Diblock and random polyampholytes display a continuous coil-globule crossover with increasing Bjerrum length.
• Alternating polyampholytes undergo a collapse similar to neutral polymers due to short-range dipole-dipole interactions.
• Collapse curves for alternating polyampholytes fit a universal master curve, indicating renormalized second virial coefficients.

Conclusions:

• Primary monomer sequence profoundly impacts charge-balanced polyampholyte conformations in good solvents.
• The nature of the electrostatically driven coil-globule transition differs significantly based on sequence.
• Simulation results align with theoretical scaling laws for polymer collapse.