Non‐volatile solid‐state memory cells based on composites of metal nanoparticles and polymers are embedded in organic semiconducting host materials. This paper presents data from a wide range of materials and device structures and shows that the switching phenomenon is commonly observed.

A new procedure is described for surface grafting polymer brushes by step-growth polymerization from initiator-embedded polymeric thin films and micron- and nanometer-scale patterns. An imprint lithographic process, nanocontact molding, was used to prepare thin patterned cross-linked polyacrylate network films on silicon wafers that incorporated 4-bromostyrene in the networks. These networks present reactive 4-bromophenyl functionality at the surface that act as attachment sites for the subsequent Ni(0)- mediated step-growth condensation polymerization of 2,7-dibromo-9,9-dihexylfluorene The step-growth polymerization medium consisted of 2,7-dibromo-9,9-dihexylfluorene, Ni(0)-catalyst, and bipyridine in a toluene/dimethylformamide solvent mixture. The resulting growth of polydihexylfluorene brushes from the patterned surface was monitored by contact angle, optical spectrometry, surface profilometry and AFM. Brush growth was conducted from patterned features ranging from 100 microm to 100 nm in width and 50 nm in height. The optical and fluorescence behavior of the polyfluorene brushes was similar to that of thin polyfluorene films made by spin coating.

The synthesis of new polymers, poly(biphenylmethylene)s, derived from bistriflates of bisphenol-type monomers, by Ni(0)-mediated polymerization has been presented. These polymers are interesting because of the nature of the polymer backbone that contains biphenyl units separated by substituted methylene units. The solubility, mechanical properties, and electrical properties of the polymers can be altered by proper selection of the methylene substituents. Polymers and oligomers had molecular weights ranging from 2000 to 15 000 g/mol, as measured by calibrated gel permeation chromatography (GPC), though light scattering and MALDI studies indicate that GPC tends to underestimate the molecular weights of these polymers. The polymers have T g's between 230 and 300 °C and have thermal stabilities ranging from 400 to 493 °C. Thermally cross-linkable, 4-phenylethenyl end-capped oligomers were synthesized and fabricated into thin-film electronic devices, and preliminary results on their characterization are discussed. The unique structure of the polymer backbone makes these materials potentially interesting in electrical applications where large-band-gap polymers with good electron/hole mobility and good thermal and oxidative stability are required.

The photophysical properties of several acceptor substituted 1-arylpyrene derivatives were investigated. The fluorescence spectra strongly depend on the nature of the aryl moiety and the position and number of methoxycarbonyl acceptor groups. Dual fluorescence, originating from a locally excited and a charge transfer state, was observed for the diester derivatives. The solvent dependence of the dual fluorescence and the slightly curved solvatochromic plots indicate a change of the character of the excited states from solvents of low to high polarity. The rate constants for fluorescence and nonradiative decay were calculated to reveal the nature of the excited-state relaxation, that is, the increase of the mesomeric interactions by geometrical flattening or stabilization of the CT state by further twisting toward perpendicularity. Flattening is the major relaxation pathway of the diester phenylpyrene derivative in nonpolar solvents whereas in highly polar solvents the low value for the fluorescence transition dipole moment (M f ) indicates stabilization of the charge transfer state by further twisting. The fluorescence of the diester biphenylpyrene derivative originates from a locally excited state (LE) in nonpolar solvents. The low value for M f in polar solvents and the change of the relative intensity of the dual fluorescence signals with the temperature indicate that the red-shifted fluorescence can be assigned to a twisted intramolecular charge transfer state.

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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.

Efficient syntheses of the novel, pyrene containing branched building blocks 10, 13, 22, 25 and of a pyrene based core molecule 16 for the construction of dendrimers are reported. The main tool is a Suzuki cross-coupling. The functional groups for further growth are amines and carboxylic acids, which were used in an orthogonally protected fashion. It was proven that the building blocks could be assembled to a low generation dendrimer 17.The spherically shape, dendrimers, 1 are unlike practically all other chemical compounds and can potentially be used to generate and investigate a directed charge transfer. 2,3 If the interior of dendrimers is equipped with electron acceptors at defined positions (generations), an electron transfer should be possible from acceptor to acceptor if there is a gradient, which provides the necessary driving force. We are presently pursuing a project to construct dendrimers with a polar gradient and to use them as components to investigate a photochemically induced energy and charge transfer. 4 The polarity gradient should serve as a driving force for either of these transfers and the large distance between the dendrimers' core and surface ought to increase the life-time of an eventual charge separated state. Both an outline of the concept 4 as well as first spectroscopical results 5 have been preliminarily published. We here report in detail the basic synthetic sequences involved. The aim is to construct pyrenes containing branched building blocks like compounds 10 and 13 for dendron and dendrimer synthesis and therefore carry an AB 2 functionality pattern (A: carboxylic acid; B: amine) to allow for application of repetitive growth schemes. The coupling between individual dendritic blocks is based on peptide derived amide bond formation, which has been proven to be very efficient in dendrimer chemistry. 6The concept involves the use of fluorescence probes and dummies, 7 whereby the latter should structurally resemble the former as closely as possible. This is why in the following some of the dendrons carry a methylene spacer between pyrene and acceptor-substituted branching unit (potential dummies) and others do not (potential probes). Tests on model compounds have shown that the incorporation of just a methylene spacer is sufficient for that purpose. 5The whole strategy rests upon compounds 4a and 4b (Scheme 1), which besides the ester (as the protected A of an AB 2 building block), carry two bromo functionalities and one iodo functionality. It was anticipated that, by utilizing the high iodo selectivity 8 of Suzuki cross-coupling (SCC) 9 that the required functionality could be incorporated into the molecule. If both iodinated and brominated sp 2 -hybridized C-atoms are present in the same molecule, the pyrene unit and two N-protected amine-terminated arms (as the B's of an AB 2 building block) could be incorporated at C-I and C-Br, respectively. Scheme 1 Reagents and conditions: (a) EtOH, toluene, H 2 SO 4 , reflux, 5 h, 78% (b) concd HOAc, Br 2 , 0 °C, 12 h, 87% (c) i. H 2 O, NaNO ...

Thin films consisting of a mixture of acrylate/methacrylate monomers were photochemically attached to modified silicon wafer surfaces. Reactive functionality was embedded into the photopolymer film by adding alkoxyamine monomers (inimers) that facilitate polymer brush growth in subsequent polymerization reactions. We present a careful examination of each of the steps, from substrate preparation to silane coupling agent coating, photopolymer attachment, and polymer brush growth. Several 3-methacryloxypropyl silanes were evaluated as silane coupling reagents. The surface roughness of wafers increased from 0.2 to 0.6 nm after treatment with silane. Curing of a thin photopolymer film did not increase the surface roughness. Interestingly, brushes of d8 polystyrene grown from the photopolymer surface displayed half the roughness of the underlying polymer layer, displaying a smoothing effect. All photopolymer films attached to the wafers utilizing a silane layer had excellent adhesion. We studied the film surfaces by water contact angle measurements, atomic force microscopy, and IR and X-ray photoelectron spectroscopies.