Rules for the Design of Patchy Particles using Self-Assembled Monolayers.

This thesis centers on the design of patchy particles and their self-assembly into ordered structures. Patchy particles have a patterned surface consisting of sticky and repulsive patches. These patches can be exploited to arrange the particles into ordered structures. In this thesis, the patchy particles are formed using monolayer protected metal nanoparticles (MPMNPs) consisting of a gold substrate coated by a self-assembled monolayer (SAMs) of thiol surfactants. The structure and patterning of the SAM can be controlled by tuning parameters like NP size and monolayer composition (variable number of surfactants in the monolayer with different length, immiscibility, and concentration). The patterned monolayer governs the interactions of the nanoparticle (NP) with its environment and other NPs. Binary SAMs were previously studied in the Glotzer group through molecular simulations. It was found that the MPMNPs could form Janus and striped particles based on sufficient entropic gains at the interfaces between immiscible surfactants. Coarse-grained simulations performed in this study have added additional surfactants to the monolayer to find a variety of new patterns (decorated Janus, decorated Cerberus, Neapolitan, decorated stripes, alternating stripes and tetrahedral particles to name a few). These patterns can be further modified by changing the ordering of the surfactants, adding additional patchiness, or changing the coverage of the patches. This work also introduces a new way of producing small Janus NP by using SAMs of surfactants with equal end groups but sufficient length difference. The long surfactants tend to crystallize on the surface of the NP leading to macrophase separation. These Janus NPs can be further functionalized to form dimers and other interesting structures. The molecular dynamics results obtained in this study are in good agreement with experimental observations. Finally, ordered structures obtained using patterned MPMNPs are also studied. Ordering of binary MPMNPs has been observed experimentally, and this study reproduces this behavior through computer simulations and extrapolates the findings to other mixed SAMs patterns.PhDChemical EngineeringUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/98044/1/inespons_1.pd