To demonstrate living anionic surface-initiated polymerization (LASIP) on silica nanoparticles, the initiator precursor 1,1-diphenylethylene (DPE) was functionalized with alkyldimethylchlorosilane and grafted onto silica particle surfaces. n-BuLi was used to activate the DPE, which allowed the anionic polymerization of the styrene monomer to proceed in benzene solution. A high-vacuum reactor was used to allow polymerization from the surface of silica particles under anhydrous solution conditions. The dispersion of the DPE functionalized silica particles showed a distinct red color indicating an activated nanoparticle−DPE−n-BuLi complex suitable for anionic polymerization. The degree and mechanism of polymerization were determined based on characterization of the grafted and detached polystyrene chains using thermogravimetric analysis, size exclusion chromatography, NMR, and Fourier transform infrared spectroscopy. In addition, atomic force microscopy and X-ray photoelectron spectroscopy were used to characterize the polymer-coated nanoparticles. The importance of activation of the grafted initiator, control of aggregation, and removal of the excess n-BuLi for high molecular weight formation is emphasized. While the polydispersities are broader compared to those obtained by solution polymerization of a free initiator, a living anionic polymerization mechanism is still observed.

Anionic surface initiated polymerization (SIP) was investigated to improve the stabilities and grafting densities of polymers on clay. This is a challenge because of the difficulties with the anionic polymerization mechanism and the presence of adventitious H2O molecules in silicates and clay. Our results showed the living anionic polymerization was only possible with the 1,1-diphenylethylene (DPE) initiator and a reaction protocol involving heating to 120 °C. The reaction serves to distinguish between surface and intergallery initiation.

The formation of homopolymer and block copolymer brushes grafted from Au and Si (SiOx) surfaces via living anionic surface-initiated polymerization (LASIP) is described. The initiator precursor 1,1diphenylethylene (DPE) was functionalized with alkylsilane or alkylthiol and grafted onto planar Si wafer and Au surfaces, respectively, by self-assembled monolayer techniques. n-BuLi was used to activate the DPE initiator for anionic polymerization of monomers at the interface. A high-vacuum reactor was used for polymerization at surfaces under anhydrous solution conditions. By a careful sequence of monomer introduction, reaction, and termination, homopolymer and block copolymer tethered polymer brushes were obtained. The grafted polymer chains were investigated using surface sensitive techniques such as ellipsometry, contact angle measurements, atomic force microscopy, Fourier transform infrared spectroscopy, surface plasmon spectroscopy, and X-ray photoelectron spectroscopy. The importance of activation of the grafted initiator, control of polymerization conditions, and removal of excess BuLi is emphasized. Interesting differences in morphology, thickness, grafting density, and polymerization conditions contrast LASIP from solution and other surface-initiated polymerization mechanisms. The formation of block copolymer sequences highlights the unique utility of a living anionic polymerization technique on surfaces.