Emergent Isotropic-Nematic Transition in 3D Semiflexible Active Polymers.

Area of Science:

• Soft Matter Physics
• Polymer Physics
• Biophysics

Background:

• Active semiflexible filaments, like cytoskeletal polymers and bacterial colonies, are prevalent in nature.
• Understanding the interplay between activity and flexibility in governing their collective organization, particularly the isotropic-nematic transition, is crucial but remains limited.

Purpose of the Study:

• To investigate how activity and flexibility jointly influence the isotropic-nematic (I-N) transition in 3D active semiflexible polymers.
• To characterize the impact of active forces on the nature and density-dependence of the I-N transition.

Main Methods:

• Large-scale Brownian dynamics simulations were employed.
• Simulations explored 3D active semiflexible polymers with systematically varied flexibility degrees and activity strengths.

Main Results:

• Tangential active forces shift the I-N transition to higher densities, with the shift dependent on flexibility and activity strength.
• Activity alters the transition's nature: discontinuous at low strengths, continuous at moderate, and suppressed at high strengths.
• Enhanced collective bending fluctuations cause chain shrinkage and delay the I-N transition, while moderate activity induces temporal isotropic-nematic state transitions.

Conclusions:

• Active forces and material flexibility critically control the organization and phase behavior of semiflexible polymer systems.
• The study reveals activity-induced instabilities and novel nonequilibrium phase diagrams for active polymer systems.
• Findings provide insights into the collective dynamics of biological filaments and synthetic active matter.