Various new technologies are benefiting from the incorporation of new nanophase materials into existing materials and devices. This dissertation explores two-dimensional motifs in creation of organic nanomaterials with new and superior properties. The major part of this thesis focuses on organic nanodisks prepared by controlled polymerization in the interior of bicelles, discoidal lipid aggregates. Another shape studied here is nanothin film mounted on a gold surface.
Synthesis of nanodisks is carried out by UV-initiated polymerization of a mixture of styrene and divinylbenzene loaded into self-assembled bicelles. Bicelles act as temporary self-assembled scaffolds, and after the synthesis lipids can be separated and recycled to template a new batch of nanodisks. This method yields new two-dimensional nanoparticles with 15–30 nm diameter and 2 nm thickness.
Aggregation behavior of nanodisks was studied in water, organic solvents, and solid phase. Aggregation of nanoparticles has been a major problem in developing various applications. Nanodisks formed a stable (>1 week) suspension of single particles in toluene and carbon tetrachloride, but required a surfactant for uniform dispersion in water. Using sodium docecylsulfate (SDS) as the surfactant, zeta potential studies revealed that particles have a good electrostatic stability at SDS concentrations below the critical micelle concentration. Further, varying the surface density of surfactants can control the size of aggregates of nanodisks in water. Upon drying, nanodisks aggregate into sub-micron platelets.
Cross-linked polystyrene nanodisks were then incorporated into bulk polystyreme to determine whether they reinforced its thermal and mechanical properties. Small-angle neutron scattering data suggest that material containing small amounts of nanodisks, as little as 0.001%, form true nanocomposites as evidenced by the presence of individual nanodisks in polystyrene matrix. Thermogravimetric analysis and flexure testing show that the composites have superior thermal and mechanical properties.
The cytotoxicity of nanodisks was also studied by determining whether cells generated reactive oxygen species in response to disks. This was tested in three cell lines for 24h by two methods: multi-well fluorescent plate reader and flow cytometry. Results indicate unlike some nanomaterials, nanodisks stimulate only a small amount of ROS in cells.
A novel bifunctional monomer, 3-(4-vinylphenyl)propanethiol, was also synthesized and used as organic coating. The monomer combines the utility of forming self-assembled monolayers with a thiol-ene cross-linking ability, enabling the development of robust films with controlled and uniform thickness in the range of several nanometers.