0000000000021423
AUTHOR
Sara Jabbari-farouji
showing 7 related works from this author
Role of the Intercrystalline Tie Chains Network in the Mechanical Response of Semicrystalline Polymers
2017
We examine the microscopic origin of the tensile response in semicrystalline polymers by performing large-scale molecular dynamics simulations of various chain lengths. We investigate the microscopic rearrangements of the polymers during tensile deformation and show that the intercrystalline chain connections known as tie chains contribute significantly to the elastic and plastic response. These results suggest that the mechanical behavior of semicrystalline polymers is controlled by two interpenetrated networks of entanglements and tie chains.
Static and dynamic scaling behavior of a polymer melt model with triple-well bending potential
2018
We perform molecular-dynamics simulations for polymer melts of the coarse-grained polyvinyl alcohol model that crystallizes upon slow cooling. To establish the properties of its high temperature liquid state as a reference point, we characterize in detail the structural features of equilibrated polymer melts with chain lengths $5\le N \le 1000$ at a temperature slightly above their crystallization temperature. We find that the conformations of sufficiently long polymers with $N >50$ obey essentially the Flory's ideality hypothesis. The chain length dependence of the end-to-end distance and the gyration radius follow the scaling predictions of ideal chains and the probability distributions o…
Compression-induced anti-nematic order in glassy and semicrystalline polymers
2020
We provide new insights into the molecular origin of the asymmetry between uniaxial tensile and compressive deformation of glassy and semicrystalline polymers using molecular dynamics simulations. The difference between the two responses strongly depends on the chain length and is the largest at intermediate chain lengths. Irrespective of chain length, the intra- and interchain organization of polymers under extension and compression are remarkably distinct. The chains align along the tensile axis leading to a global nematic order of the bonds and end-to-end vectors, whereas compression reorganizes polymers to lie in planes perpendicular to the compressive axis resulting in the emergence of…
Ewald sum for hydrodynamic interactions of rigid spherical microswimmers
2018
We derive the Ewald sum decomposition of the grand mobility tensor which captures the hydrodynamic interactions in an infinite suspension of rigid spherical microswimmers. The grand mobility tensor connects the motion of an individual swimmer to the active and passive forces and torques acting on all the swimmers, and it is calculated based on a minimal microswimmer model incorporating the swimmers' finite body size. Our results have direct applications to the Stokesian dynamics simulations of an infinite suspension of rigid-bodied microswimmers. They also provide a platform to develop more advanced methods such as particle-mesh-Ewald-sum and accelerated Stokesian dynamics simulations.
Controlling stability and transport of magnetic microswimmers by an external field
2019
We investigate the hydrodynamic stability and transport of magnetic microswimmers in an external field using a kinetic theory framework. Combining linear stability analysis and nonlinear 3D continuum simulations, we show that for sufficiently large activity and magnetic field strengths, a homogeneous polar steady state is unstable for both puller and pusher swimmers. This instability is caused by the amplification of anisotropic hydrodynamic interactions due to the external alignment and leads to a partial depolarization and a reduction of the average transport speed of the swimmers in the field direction. Notably, at higher field strengths a reentrant hydrodynamic stability emerges where t…
Flow properties and hydrodynamic interactions of rigid spherical microswimmers.
2017
We analyze a minimal model for a rigid spherical microswimmer and explore the consequences of its extended surface on the interplay between its self-propulsion and flow properties. The model is the first order representation of microswimmers, such as bacteria and algae, with rigid bodies and flexible propelling appendages. The flow field of such a microswimmer at finite distances significantly differs from that of a point-force (Stokeslet) dipole. For a suspension of microswimmers, we derive the grand mobility matrix that connects the motion of an individual swimmer to the active and passive forces and torques acting on all the swimmers. Our investigation of the mobility tensors reveals tha…
Emergent pattern formation of active magnetic suspensions in an external field
2020
We study collective self-organization of weakly magnetic active suspensions in a uniform external field by analyzing a mesoscopic continuum model that we have recently developed. Our model is based on a Smoluchowski equation for a particle probability density function in an alignment field coupled to a mean-field description of the flow arising from the activity and the alignment torque. Performing linear stability analysis of the Smoluchowski equation and the resulting orientational moment equations combined with non-linear 3D simulations, we provide a comprehensive picture of instability patterns as a function of strengths of activity and magnetic field. For sufficiently high activity and…