The patterning of biologically active materials has been accomplished by the use of imprint lithography of functional photopolymer resins to create controlled nanoscale patterns of a cross-linked photopolymer containing embedded initiator groups. Functionalized polymer brushes consisting of polystyrene and poly(N,N-dimethylacrylamide) were grown from these patterned layers by nitroxide-mediated polymerization. Chain-end functionalization of the brush layer was accomplished by nitroxide radical exchange during the polymerization. Accordingly, brush layers terminated by pyrene and biotin functional groups were obtained by exchange with the appropriate alkoxyamines. The presence of pyrene functionality at the chain ends of the brushes was confirmed by fluorescent emission measurements. Fluorescently labeled streptavidin protein was selectively attached with high selectivity to the patterned biotinylated brush layer through biotin−streptavidin interactions. The functionalized polymer grafted surfaces and nanopatterns have been successfully characterized using a fluorescence spectrophotometer, AFM, SEM, confocal microscopy, and water contact angle measurements.

A method for simultaneously patterning and functionalizing thin poly(2-hydroxyethyl methacrylate) films through a reactive silane infusion based wrinkling is developed. Wrinkled patterns with tunable wavelengths on submicrometer size are easily produced over large area surfaces and can express a wide variety of chemical functional groups on the surface. The characteristic wavelength of wrinkling scales linearly with initial film thickness, in agreement with a gradationally swollen film model. Results from X-ray photoelectron spectroscopy confirm that the wrinkled film is composed of two layers: a gradient cross-linked top layer and a uniform un-cross-linked bottom layer. The surface chemical properties of wrinkles can be easily tuned by infusion of different functional silanes. Hierarchical wrinkled patterns with micro/nano structure can be achieved by combining wrinkling with other simple lithography methods. Wrinkled nanopatterns can be used as a mold to transfer the topology to a variety of other materials using nanoimprint lithography.

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An easy and novel approach to the synthesis of functionalized nanostructured polymeric particles is reported. The surfactant‐free emulsion polymerization of methyl methacrylate in the presence of the crosslinking reagent 2‐ethyl‐2‐(hydroxy methyl)‐1,3‐propanediol trimethacrylate was used to in situ crosslink colloid micelles to produce stable, crosslinked polymeric particles (diameter size ∼ 100–300 nm). A functionalized methacrylate monomer, 2‐methacryloxyethyl‐2′‐bromoisobutyrate, containing a dormant atom transfer radical polymerization (ATRP) living free‐radical initiator, which is termed an inimer (initiator/monomer), was added to the solution during the polymerization to functionalize the surface of the particles with ATRP initiator groups. The surface‐initiated ATRP of different monomers was then carried out to produce core–shell‐type polymeric nanostructures. This versatile technique can be easily employed for the design of a wide variety of polymeric shells surrounding a crosslinked core while keeping good control over the sizes of the nanostructures. The particles were characterized with scanning electron microscopy, transmission electron microscopy, optical microscopy, dynamic light scattering, and Raman spectroscopy. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 1575–1584, 2007

Disubstituted polyacetylene brushes were grown from modified silicon and quartz surfaces using a transition metal-catalyzed polymerization technique employing tungsten hexachloride/tetraphenyl tin (WCl6/Ph4Sn). The substrate surfaces were initially functionalized with terminal alkyne functional groups by using an alkyne-functionalized silane, O-(propagyloxy)-N-(triethoxysilylpropyl) urethane, as a surface coupling agent. Surface polymerization of 5-decyne under microwave irradiation at 150 degrees C for 30 min was performed on the functional surfaces to produce surfaces consisting of grafted poly(1,2-dibutylacetylene) brushes. The alkyne-functionalized and polymer-coated surfaces were characterized using surface contact angle measurements, film thickness measurements, atomic force microscopy, and X-ray photoelectron spectroscopy, and fluorescence spectrometer measurements were performed to analyze the surfaces at each step of the modification process. This simple technique demonstrates a novel way of synthesizing a poly(1,2-dibutylacetylene) brush layer on silicon substrate, and it has future potential in the fabrication of selectively functionalized surfaces on the nanoscale via this new synthetic approach.

Enhancements in both the rate and extent of grafting of poly(9,9'-n-dihexyl fluorene) (PDHF) onto flat and nanopatterned crosslinked photopolymer films are described. Reactivity of the surfaces toward grafting via the Yamamoto-type Ni(0)-mediated coupling reaction is increased by synthesizing and incorporating 2,7-dibromo-9-fluorenyl methacrylate (DBFM, 2) as a new grafting agent. Varying the concentration of surface-embedded DBFM is shown to control both overall graft formation and fluorescence with a maximum thickness of up to 30 nm and peak emission at 407 nm for 40 wt% loading. In addition, microwave irradiation is introduced as an effective means to drive graft formation and thus allows fabrication of PDHF-functionalized surfaces in as little as 30 min. Both forms of improvement are extended to DBFM-embedded, nanocontact-molded features ranging in size from 100 microm to 100 nm in width and 60 nm in height. Microwave-assisted grafting from these patterned surfaces produces fluorescent features as imaged by optical microscopy and a corresponding increase in feature height as measured by atomic force microscopy.

Transition-metal-catalyzed coupling reactions of halogenated molecules leading to formation of new carbon-carbon bonds are a very important category of reactions used in the synthesis of complex compounds and conjugated polymers. [1][2][3] Within the past decade, this methodology has evolved into a powerful synthetic tool for the preparation of a wide range of specialty polymers, composite materials, and pharmaceutically active compounds both in the laboratory and on the industrial scale. It is also widely appreciated in the context of parallel synthesis and combinational chemistry. [4,5] We desired to develop an improved catalytic method for transition-metal-catalyzed aryl coupling reactions and report herein the one-pot, one-step, nickel-catalyzed coupling of aryl bromides in the presence of alkyllithium reagents [Eq. (1)].Metallic reagents including palladium and nickel complexes have demonstrated to be quite effective in C À C coupling reactions. Typically, coupling reactions of aryl halides involving the use of catalytic amounts of nickel(II) complexes require the addition of either magnesium or zinc to facilitate efficient coupling and regeneration of active nickel(0) catalytic species. For example, Kumada coupling reactions use magnesium for the formation of active alkyl/ aryl magnesium bromide species (Grignard formation), which is generally a substrate-and solvent-specific reaction (working optimally in tetrahydrofuran or diethyl ether as solvents). [6][7][8][9][10] Nickel reactions facilitated by the addition of zinc powder have been utilized in a similar fashion in organic synthesis, [11][12][13] as well as in efficient condensation polymerizations. [14][15][16] These reactions are not always well controlled, require prolonged heating at high temperatures, and the products have high levels of metal impurities that can be difficult and costly to remove. This trace-metal contamination is especially problematic if the end use is in pharmaceutical or microelectronic applications in which safety, performance, and reliability require stringent control of purity. Another known aryl-halide coupling reaction involves the use of highly reactive zinc (Rieke zinc), which is prepared by reduction of ZnCl 2 with lithium naphthalenide and has been shown to readily undergo oxidative addition with alkyl, aryl, and vinyl halides under mild conditions to generate the corresponding organozinc compounds. These reactive organozinc compounds are then cross-coupled with other aryl or vinyl halides using palladium(0) catalysts. [17] Recently, homocoupling of bromide compounds has been facilitated through the combination of metallic magnesium and a catalytic amount of iron salts.[18] Coupling reactions involving activated dihalogenated thiophene molecules catalyzed by nickel(II) complexes have also been demonstrated in the presence of reactive zinc (Rieke zinc) [19] or an alkylmagnesium reagent (GRIM/McCullough method) [20] to form regioregular polythiophenes.Coupling reactions of halogenated molecules involving nickel(0) compl...

Acid-catalyzed hydrolysis of 2,5-dimethyl-2,5-hexanediol dimethacrylate (DHDMA)-containing nanoparticles has been carried out to bring about topological reorganization from spherical macromolecular crosslinked particles to linear polymer. The reactive cross-linked poly(methyl methacrylate)-based (x-PMMA) nanoparticles have been prepared via aqueous emulsion techniques where the size of the particles depends upon the type of emulsion polymerization employed, surfactant-free or surfactant-based. Potassium persulfate has been employed as the water-soluble initiator and sodium dodecyl sulfate as the surfactant. Because of the acid-sensitive nature of the tertiary ester groups of the 2,5-dimethyl-2,5-hexanediol dimethacrylate within the cross-linked nanoparticles, they can be easily cleaved into their linear polymer chain composition under acidic conditions. The particles were degraded by heating in dioxane in the presence of p-toluenesulfonic acid at 100 °C for 12 h. The cleavage of the cross-linked nanoparticles was observed by the correlation and size distribution plots obtained using dynamic light scattering. The particles and the acid cleaved, linear polymer residue were characterized using scanning electron microscopy (SEM), solubility tests, and gel permeation chromatography.