Atomistic Simulation of a Thermoplastic Polyurethane and Micromechanical Modeling
Name
lempesis_macromol17_postreview.pdf
Description
Accepted version
Size
11.29 MB
Format
Adobe PDF
Checksum (MD5)
270bc976b12af9376502ac146eaae200
Author(s)
Lempesis, Nikolaos
in ‘t Veld, Pieter J.
Rutledge, Gregory C
Date Issued
September 2017
Journal
Macromolecules
Publisher
American Chemical Society (ACS)
Citation
Lempesis, Nikolaos et al. "Atomistic Simulation of a Thermoplastic Polyurethane and Micromechanical Modeling." Macromolecules 50, 18 (September 2017): 7399–7409 © 2017 American Chemical Society
Version
Author's final manuscript
Abstract
Thermoplastic polyurethanes constitute a versatile family of materials with a broad variety of engineering applications. However, connection between their chemical structure and mechanical properties remains elusive, in large part due to their heterogeneous nature, arising from segregation of chemically distinct segments into separate domains, with resulting complex morphologies. Using atomistic simulations, we examine the structure and mechanical properties of a common family of thermoplastic polyurethanes (TPU) comprising 4,4′-diphenylmethane diisocyanate and n-butanediol (hard segment) and poly(tetramethylene oxide) (soft segment). A lamellar stack model previously developed for the study of semicrystalline polymers is applied here for the first time to a phase-segregated copolymer. Equilibrium structure and properties were evaluated for TPUs with different ratios of hard and soft components, using a combination of Monte Carlo and molecular dynamics simulations. Stress-strain behaviors were then evaluated using nonequilibrium molecular dynamics (NEMD) simulations. The compositional dependence of the Young's moduli thus obtained is shown to be well-approximated by a micromechanical homogenization model of the hard and soft components. Voigt (upper) and Reuss (lower) bounds of modulus were obtained for orientationally averaged aggregates and shown to be greater than those measured experimentally. The discrepancy is explained in terms of the strain rate dependence of elastic moduli, characterized by an Eyring-like function.
MIT Department
Massachusetts Institute of Technology. Department of Chemical Engineering
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DOI of Published Version
https://doi.org/10.1021/acs.macromol.7b01296
