| Two topics related to chemical modification of material surfaces are investigated. First, we apply the "grafting to" approach to construct binary self-assembled monolayers (SAMs) used to control the adsorption of colloidal aggregates onto solid substrates. Second, we investigate the chemical modification of surfaces by employing Monte Carlo computer simulations to investigate the kinetics of surface-initiated controlled radical polymerization (CRP) for the synthesis of grafted polymer films ("grafting from" approach).;SAMs constitute layers of small molecules that assemble spontaneously at an interface. SAMs of mixed aromatic and aliphatic trichlorosilanes with varying thickness, aromaticity, and chemical composition were constructed by simultaneous codeposition of the molecules from solution ("grafting to"). We characterize these layers by measuring their wettability (using contact angle goniometry, CA), thickness (using variable angle spectroscopic ellipsometry, VASE), and chemical composition (using near-edge x-ray absorption fine structure spectroscopy, NEXAFS). Variations in the ratio of aromatic to aliphatic molecules in the deposition solution resulted in SAMs with fine-tuned compositions and thicknesses.;We used mixed SAMs to control the adsorption of asphaltenes onto silicon substrates. Asphaltenes, a petroleum-derived class of molecules that tend to aggregate in solution, are highly polar, aromatic, and surface active. The thickness and chemical composition of the asphaltene treated SAMs were characterized by VASE and NEXAFS, respectively. We find that SAMs that expose the underlying polar silica substrate promote the adsorption of asphaltenes, while SAMs that shield the polar silica layer largely prevent the adsorption.;In the second part of this dissertation, we investigate surface-initiated CRP by Monte Carlo computer simulation. In surface-initiated CRP, polymerization starts directly from a SAM of initiating molecules on a surface. A computer model of the surface-initiated CRP reaction is developed and a stochastic algorithm based on the bond-fluctuation model is implemented. We explore the effect of the grafting density of initiators and the solvent quality on polymer properties such as the average molecular weight, root-mean squared radius of gyration, and polydispersity index. We find that confining the initiators by placing them on the surface or by performing the simulation in poor solvent conditions leads to decreased polymerization rate and increased polydispersity index. Our results suggest that the assumption that solution- and surface-initiated polymers have equivalent properties is seldom valid.;We also study the simultaneous polymerization of surface- and bulk-initiated polymers. The competition between these two polymer populations for a limited supply of free monomers affects the properties of both classes of polymers. The effect that this competition has on the polymer properties depends on the fraction of polymers on the surface, the grafting density of initiators and the initial number of free monomers. We find that increasing the number of fast-growing bulk initiators limits the growth of the slow-growing, surface-confined chains, which results in different molecular weight distributions of bulk- and surface-initiated polymers. |
