Synthesis and patterning of polymer films from self-assembled monolayers of free radical initiators

Surface tethered polymer films were prepared by a “grafting-from” methodology utilizing free radical initiation. Initiators were covalently bound to the surface of silicon substrates by self-assembled monolayer (SAM) techniques. Two initiator SAMs were prepared for this purpose. One contained azo functionality and the second contained perester functionality.; The rate of decomposition of the perester functional monolayer was studied. A deuterated surfactant was synthesized for this purpose. Solution decomposition was followed by 1H NMR. Decomposition was followed by ATR-FTIR spectroscopy. The rate of surface decomposition was compared to the rate in solution. The decomposition rates were found to be equivalent within experimental error.; Tethered diblock copolymers of styrene and MMA were prepared from the azo functional initiator. The first block, PS, was prepared by a reverse atom transfer radical polymerization process (RATRP) using CrBr and PMEDTA ligand. The second block, PMMA, was prepared using the first block as a surface tethered macroinitiator for atom transfer radical polymerization (ATRP). The resulting surface tethered PS-b-PMMA films exhibited variable water contact angles. Immersion in methyl cyclohexane (MCH) resulted in water contact angles of 92° advancing and 69° receding, similar to those of a polystyrene film. Immersion in dichloromethane resulted in contact angles of 73° advancing and 55° receding, similar to those of a PMMA film.; Finally, laterally patterned polymer films were prepared from the bound azo functional initiator. Polymerization of styrene was initiated by UV irradiation. Lateral patterning was achieved by use of a stereolithography apparatus (SLA). A SLA was constructed for this purpose. The SLA permitted selective initiation of styrene polymerization from the surface of the substrate. Patterned arrays were formed using continuous and intermittent irradiation. The intermittent irradiation scheme produced thicker films in less polymerization time. This is due to the reduced instantaneous concentration of growing radicals in the polymerization area. In both cases the thickness of the polymer films increased with irradiation time.