Unlocking of the unexpected behaviors of polyurea

Polyurea is a thermoplastic elastomer with excellent shock and impact resistance. At high strain rates (~ 10^6 s^-1) and pressures (~ 9 GPa), its shear modulus (500 MPa) matches the shear modulus of high strength steels. Molecular dynamics (MD) simulation can shed light on the molecular origins of this response. However, MD simulation of polyurea is challenging due to its phase-segregated microstructure and the presence of a wide range of associated length and time scales. Our work instead leverages the microstructure to perform multiscale shock simulation of the domains in polyurea and yielded insights into the molecular-scale mechanisms underpinning shock mitigation. To develop a comprehensive understanding of the microstructural mechanisms at play, we have also developed a novel generic coarse-grained model of polyurea as a liquid-crystalline polymer.

[1] Manav, M., & Ortiz, M. (2021). Molecular dynamics study of the shock response of polyurea. Polymer, 212, 123109.

[2] Manav, M., Ponga, M., & Ortiz, M. (2023). Modeling hard–soft block copolymers as a liquid crystalline polymer. Polymer, 287, 126389.

[3] Manav, M., Ponga, M., & Ortiz, M. Dynamic response of a hard-soft block copolymer modeled as a liquid crystalline polymer. In preparation.