Pulling on grafted flexible polymers can cause twisted bundles.

Area of Science:

• Polymer Physics
• Soft Matter Physics
• Computational Materials Science

Background:

• Semiflexible polymer bundles exhibit twisting at low temperatures to optimize energetic balance between attraction and bending costs.
• The behavior of flexible grafted polymer bundles under external forces, particularly regarding twisting, remains less understood.

Purpose of the Study:

• To investigate whether flexible grafted polymer bundles can exhibit helical twisting under applied pulling forces.
• To determine the force regimes governing the conformational transitions of these polymer bundles.

Main Methods:

• Utilized Monte Carlo computer simulations to model small bundles of flexible grafted polymers.
• Analyzed bundle conformations across a range of applied pulling forces (F) and external fields.

Main Results:

• At weak forces (F < Fl), intertwined globular conformations are favored.
• At strong forces (F > Fu), rod-like bundle structures are observed.
• An intermediate force window (Fl < F < Fu) clearly shows bundles adopting helical twists.

Conclusions:

• Flexible polymer bundles can develop helical twists under sufficient pulling force, similar to semiflexible polymers.
• Applied external fields induce qualitatively similar effects to pulling forces.
• Flexible polymers under force or field effectively behave like semiflexible polymers without external influence.