Molecular modelling of nucleation in polymers

Area of Science:

• Polymer science and materials chemistry.

Background:

• Conventional theories attribute polymer lamellar thickness to kinetics.
• Polymer nucleation differs from small molecules due to single-chain multi-nuclei participation.
• This leads to entropic frustration and transient structures during nucleation.

Purpose of the Study:

• Investigate molecular mechanisms of early-stage polymer crystallization from solutions.
• Clarify the origins of finite lamellar thickness in polymer crystals.
• Challenge existing assumptions in polymer crystallization theories.

Main Methods:

• Utilized Langevin dynamics simulations.
• Developed and employed theoretical models, including an exactly solvable model for chain entropy.

Main Results:

• Demonstrated that finite lamellar thickness is an equilibrium, not kinetic, phenomenon.
• Identified chain adsorption and cooperative chain dynamics as dominant factors in lamellar growth.
• Revealed that a single polymer chain can participate in multiple nuclei, causing entropic frustration.

Conclusions:

• The finite lamellar thickness in polymer crystals is an equilibrium thermodynamic result.
• Early-stage polymer crystallization is governed by unique chain behaviors like multi-nuclei participation and cooperative adsorption.
• This study provides a new framework for understanding polymer crystallization, diverging from traditional kinetic-based explanations.