GAFF-IC: realistic viscosities for isocyanate molecules with a GAFF-based force field

ABSTRACT

Aliphatic diisocyanates and their derivatives are key liquid components in the industrial processing of polyurethane materials. In particular, for the synthesis of crosslinked polyurethane materials, the higher functionality molecules obtained by reacting three -or more- diisocyanates are of interest. However, despite their widespread application, the relation between molecular structure and macroscopic physical properties, in particular viscosity, is poorly understood in these systems. In this work, we introduce a new force field parameter set, GAFF-IC, based on the widely-used and versatile GAFF force field, meant for accurate predictions of physical properties of isocyanate-based molecular liquids. The new parameters allow to predict the vaporization enthalpies and densities of several isocyanate-based molecules, which are found in excellent agreement with the available experimental data. The effectiveness and transferability of the improved parameters is verified by calculating the viscosities of several isocyanates, isocyanate dimers (uretdiones) and isocyanate trimers (isocyanurates), resulting in accurate viscosity predictions in excellent agreement with experimental values.

KEYWORDS:

• Molecular dynamics
• isocyanates
• isocyanurates
• viscosity
• GAFF

Acknowledgments

The authors wish to thank Dr. Frank Richter and his research team at Covestro Deutschland AG for continued collaboration and fruitful discussions.

Disclosure statement

There are no conflicts of interest to declare.

ORCID

Veniero Lenzi http://orcid.org/0000-0002-3633-1966

Dirk J. Dijkstra http://orcid.org/0000-0003-0140-9636

Marta M.D. Ramos http://orcid.org/0000-0001-6176-5048

Luís S.A. Marques http://orcid.org/0000-0001-7477-6934

Additional information

Funding

This project has received funding from the European Union's Horizon 2020 research and innovation program under the Marie Skłodowska-Curie Grant Agreement no. 642890 (http://thelink-project.eu/) and it was partially supported by the Portuguese Foundation for Science and Technology (FCT) in the framework of the Strategic Funding UID/FIS/04650/2013, and by the project ”Search-ON2: Revitalization of HPC infrastructure of Uminho” (NORTE-07-0162-FEDER-0000869), under the National Strategic Reference Framework, through the European Regional Development Fund.