480702 Screening Chemical Parameter Space of Self Assembling Monolayers
Here, we present MoSDeF (Molecular Simulation and Design Framework) : developed to create and parameterize such arbitrary systems and naively manage simulations enabling large scale parameter screening of soft materials. We demonstrate the efficiency of using MoSDeF by generating an ensemble of 36 SAM systems using crystalline and amorphous silica substrates; alkane, methyl capped polyethylene glycol, and hydroxyl capped polyethylene glycol polymers; and chain lengths of 7, 10, 13, 16, 19, and 22 in minutes on a conventional workstation. Seven shearing simulations were done on each of the 36 SAM systems at 300 K and a 10 m/s shear rate for normal loads of 300, 600, 900, 1200, 1500, 2100, and 2700 kJ/mol/Å for a total of 252 simulations. Shearing simulations of the SAM systems were performed using the GROMACS  simulation engine to explore frictional forces, perpendicular forces, nematic ordering, and the stick-slip phenomenon of the individual SAM systems and to establish chemical parameter trends. While crystalline alkane SAM systems may produce unreliable data because of the extreme order of the system, trends were observed for orther systems. Trends observed relate the frictional forces, perpendicular forces, nematic ordering, and the stick-slip phenomenon to the three different polymers and varying chain lengths. The workflow presented here serves as a stepping stone towards the automated screening of soft materials using molecular simulation.
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