(693e) Formation of Ultrathin Polystyrene Films By Admicellar RAFT Polymerization

Since the initial reports in the 1980’s, admicellar polymerization, the surface analog of emulsion polymerization, has been utilized for many applications including filler/matrix compatibility, corrosion control, electrically conductive films, and fabric coatings. Admicellar polymerization produces a polymer film on the order of one nanometer, significantly thinner than other surface coating techniques. Previous studies on admicellar polymerization relied on unusually high ratios of initiator to monomer for free radical polymerization. We hypothesized this is due to the presence of dissolved oxygen in the polymerization media. We studied the effect of oxygen on the polymer formed through admicellar polymerization on silica particles using cetyltrimethylammonium bromide as the adsorbed surfactant bilayer template, styrene as the monomer, and azobisisobutyronitrile as the free radical initiator. The solutions were deoxygenated by purging the headspace with nitrogen prior to the initiation of the admicellar polymerization of styrene. We demonstrated that the presence of oxygen drastically lowers the molecular weight and mass of the polymer film formed on the surface of porous silica substrates. These results open the way for the formation of more advanced thin films. Ongoing studies in our group focuses on uniting the advantages of reversible addition-fragmentation chain transfer (RAFT) polymerization and admicellar polymerization to produce well-defined ultrathin polymer films on surfaces. RAFT polymerization is noted as a highly controlled synthetic method and is compatible with a wide variety of functional monomers under conditions utilized in admicellar polymerization. Our initial investigation focuses on the RAFT polymerization of styrene inside an admicelle on the surface of silica particles. The preliminary results demonstrate the ability to better control the molecular weight of the formed polymer films using RAFT polymerization inside admicelles compared to the traditional admicellar polymerization technique.