Construction of amorphous structure using reverse mapping

As an efficient method for creating amorphous polymer structures, a technique using reverse mapping was introduced. While conventional methods required compression and equilibration from a dilute state, this method uses a Coarse-Grained model to rapidly create structures based on specified density and characteristic ratio, then converts them to a Full-Atomistic model to reproduce polymer entanglement and structural characteristics. Validated with several polymers such as polyethylene and polystyrene, the method’s structural validity and efficiency were confirmed.

Use Cases Highlights

Efficient creation of relaxed structures for long-chain polymer models
Consideration of characteristic structural parameters of polymers
Capability to create more ideal structures compared with conventional methods

Efficient creation of relaxed structures for long-chain polymer models

A comparison of amorphous structure creation flows between the conventional method and the reverse-mapping method is shown. The conventional method involves compression from a dilute state, whereas the reverse-mapping method uses a Coarse-Grained model for efficient equilibration followed by conversion to a Full-Atomistic model.

Process flow of amorphous structure creation function (left: standard version, right: reverse mapping version)

Consideration of characteristic structural parameters of polymers

A comparison of density and radius of gyration (Rg) for three types of polymers—polyethylene (PE), polybutadiene (PB), and polystyrene (PS)—is shown. While densities are similar between both methods, differences in Rg become more pronounced as the degree of polymerization increases.

Density and radius of gyration for three levels of polymer models created with the amorphous generation function

Capability to create more ideal structures compared with conventional methods

The degree-of-polymerization dependence of the mean-squared end-to-end distance for PB, PE, and PS models is shown. The reverse-mapped version yielded trends close to the theoretical proportional relationship, confirming the structural validity.

Comparison of polymerization degree dependence of generated PB, PE, and PS models

Reference

[1] L. J. Fetters, D. J. Lohse, and R. H. Colby, Physical properties of polymers handbook , 445?452 (2006).
[2] H. Nitta, T. Ozawa and K. Yasuoka, J. Chem. Phys., 159, 194903 (2023).

Details of analysis