| The goal of this research was to develop self-assembled monolayer (SAM) techniques as a rational means to template the growth of molecular crystals. A series of X-substituted-mercaptobiphenyls and benzenethiols were synthesized, and subsequently self-assembled onto 2D gold substrates that were prepared via high-pressure gold sputtering on mica. The SAMs surface functionality and roughness were assessed by contact angle measurements and atomic force microscopy, respectively. Reasonable predictions as to the spatial separation of the terminal functional groups (H, I, NO2, Br, CN) can be made based on the close-packing requirements of the arene groups.;The SAMs-growth method was first applied to controlling the growth orientation of a polar crystal system, 4-iodo-4'-nitrobiphenyl. The orientation of polar crystals grown on these templates suggests that dipole-dipole interactions at the SAM/crystal interface direct the polar and/or direct orientation of the macroscopic crystal. The next phase was to control molecular crystal polymorphism using SAM template strategies. This was achieved on three crystal systems to date--2-iodo-4-nitroaniline, 1,3-bis(m-nitrophenyl) urea, and (E)-4,4'-dimesityl-but-3-enolidylidene- but-3'-enolide.;Empirical observations made from these studies suggested that the quality of crystals grown on SAMs often appeared to be of higher quality than those grown from solution. Second harmonic generation measurements were obtained on molecular crystals known to exhibit nonlinear optical activity when grown from conventional solvents and on SAMs templates. In the majority of cases, crystals grown on SAM templates appear to have better crystalline order and improved SHG response.;Overall, the SAMs-directed nucleation of 27 crystal systems was examined---19 of which were successful. Collectively, these investigations demonstrate the utility of the method and shed insight into the fundamental roles both chemistry and epitaxy play at the SAM/crystal interface. |
