Automated Parameterization of Coarse-Grained Polyethylenimine under a Martini Framework

Area of Science:

• Polymer Science
• Computational Chemistry
• Materials Science

Background:

• Synthesized polyethylenimine (PEI) is a versatile polymer with complex, polydisperse branched structures.
• Understanding the structure-property relationships of PEI is crucial for optimizing its performance in diverse applications.
• Manual development of coarse-grained (CG) force fields for PEI is labor-intensive and error-prone.

Purpose of the Study:

• To develop a fully automated algorithm for coarse-graining branched polyethylenimine (PEI) architectures from all-atom (AA) simulations.
• To validate the accuracy of the automated coarse-graining method by comparing simulation results with AA simulations and experimental data.
• To enable efficient computational prediction of PEI properties and chemical structures.

Main Methods:

• Development of a fully automated algorithm to generate coarse-grained (CG) models from all-atom (AA) simulation trajectories and topologies of branched PEI.
• Application of the algorithm to coarse-grain a 2 kDa branched PEI, comparing diffusion coefficients, radius of gyration, and end-to-end distances with AA simulations.
• Experimental validation using commercially available 2 kDa and 25 kDa PEI, simulating CG models at various concentrations to reproduce diffusion coefficients, Stokes-Einstein radii, and intrinsic viscosity.

Main Results:

• The automated algorithm successfully coarse-grained branched PEI architectures.
• CG simulations accurately replicated key properties such as diffusion coefficient, radius of gyration, and end-to-end distance from AA simulations.
• The CG PEI models reproduced experimental data for diffusion coefficient, Stokes-Einstein radius at infinite dilution, and intrinsic viscosity.

Conclusions:

• The developed automated algorithm provides an efficient and accurate method for coarse-graining complex branched PEI structures.
• This computational strategy allows for the inference of probable chemical structures of synthetic PEIs.
• The coarse-graining methodology is extendable to other polymer systems, offering broad applicability in polymer research.