Synthesis and Oxidative Cross-Linking of Fluorene-Containing Polymers To Form Conjugated Network Polyfluorenes: Poly(fluoren-9,9-diyl-<i>a</i><i>lt</i>-alkan-α,ω-diyl)

Synthesis and Oxidative Cross-Linking of Fluorene-Containing Polymers To Form Conjugated Network Polyfluorenes:  Poly(fluoren-9,9-diyl-alt-alkan-α,ω-diyl

Distinct Surface Morphologies of Electropolymerized Polymethylsiloxane Network Polypyrrole and Comonomer Films

The electropolymerization of polysiloxane-functionalized pyrrole or poly(methyl-(undec-pyrrole-1-yl-decyl)-siloxane), to form conjugated network polymer films, is described. The “precursor polypyrrole” was electropolymerized using dynamic cyclic voltammetry (CV) on a flat conducting substrate electrode, resulting in cross-linked polypyrrole films. Unique “nanoscale” morphologies were formed because of phase-segregation of polysiloxane domains and cross-linked polypyrrole, depending on the thickness and electrochemical conditions. By electropolymerizing the precursor polymer in-situ with pyrrole comonomers, the morphology changes with composition ratio. The film properties were investigated by cyclic voltammetry (CV), FT-IR, UV−vis, atomic force microscopy (AFM), surface plasmon spectroscopy (SPS), and X-ray photoelectron spectroscopy (XPS). The precursor method extends the possibility of tailoring film properties of polypyrrole and other conjugated polymers. Interesting insights on the electrochemical properties of cross-linked electrodeposited conjugated polymer films are discussed

Nanopatterning and Fabrication of Memory Devices from Layer-by-Layer Poly(3,4-ethylenedioxythiophene)−Poly(styrene sulfonate) Ultrathin Films

A write−read−erasable memory device was fabricated on layer-by-layer (LbL) ultrathin films prepared from poly(3,4-ethylenedioxythiophene)−poly(styrene sulfonate) (PEDOT−PSS) and poly(diallyldimethylammonium chloride) (PDDA). By use of current-sensing atomic force microscopy (CS-AFM), nanopatterns were formed by applying a bias voltage between a conductive tip (Pt-coated Si3N4 cantilever) in contact with the polymer film and gold substrate. The dependence of the nanopatterns on film thickness, applied bias, and writing speed was studied. Moreover, the height of the patterns was 3−5 times higher than the original thickness of the films, opening the possibility for three-dimensional nanopatterning. The ability of the patterns to be erased after nanowriting was also investigated. By comparing the I−V characteristics under ambient conditions and under N2 environment, a joule-heating activated, water meniscus-assisted anion doping mechanism for the nanopatterning process was determined. Write−read−erase memory device capability was demonstrated on the nanopatterns

Nanopatterning and Nanocharge Writing in Layer-by-Layer Quinquethiophene/Phthalocyanine Ultrathin Films

Nanometer-scale patterning and charging in layer-by-layer (LbL) ultrathin films of quinquethiophene (5TN)/phthalocyanine (CuPS) provides a novel write−read device using a standard current-sensing atomic force microscopy (CS-AFM). The AFM height images showed dented or raised morphological features that could be selectively manipulated by changing the direction of the bias voltages. The conductivity was repeatedly changed between a conductive and insulating state, originating from an electrochemical charging−discharging effect. This was attributed to electrochemical ion transport and the residual mobile ions present in LbL films. Finally, the nanocharge pattern was written by CS-AFM and read out in a conductivity map image

Electrochemically Active Dendritic−Linear Block Copolymers via RAFT Polymerization: Synthesis, Characterization, and Electrodeposition Properties

We describe a series of well-defined dendritic−linear block copolymer architectures via the reversible addition−fragmentation chain transfer (RAFT) polymerization technique. Using dendritic chain transfer agents (CTA)s possessing a single dithioester moiety at the focal point, RAFT polymerization was carried out to attach polystyrene (PS) and poly(methyl methacrylate) (PMMA) chains of controlled lengths by kinetic control. To provide electrochemical functionality, the dendritic CTAs were designed with carbazole moieties at the periphery of the structures. The results on the electrochemical polymerization of the carbazole moieties at the periphery of the dendritic component of the block copolymers reveal quantitative cyclic depositions with changes in viscoelastic properties of the deposited films as monitored by the electrochemical quartz crystal microbalance technique. The electroactive dendritic blocks proved to be an effective electrochemically active macromonomer for the electrodeposition of these structures on conducting substrates

Nanocomposite Hydrogen-Bonded Multilayer Ultrathin Films by Simultaneous Sexithiophene and Au Nanoparticle Formation

Terthiophene-functionalized poly(4-vinylpyridine) (PVP3T) was incorporated successfully as a reductant to form Au nanoparticles within hydrogen-bonded complexed multilayer thin films. By employing polymer pendant terthiophene moieties, this eliminated the need for an external reducing agent. The redox reaction with HAuCl4 yielded Au nanoparticles simultaneously with the formation of electrooptically active sexithiophene units. The nanocomposite films were characterized by TEM, XPS, UV−vis, photoluminescence, FT-IR, and ellipsometry measurements. The TEM images confirm unequivocally the formation of well-dispersed nanoparticles within the multilayer structure with a range of size distributions dependent on the preparation conditions. Interestingly, we observed the growth of dendritic nanostructures within the PVP3T/poly(acrylic acid) multilayers with modifications to the preparation procedure. On the basis of these results, this method yields a unique approach for the fabrication of nanocomposite multilayer heterostructures comprised of metallic nanoparticles and conjugated oligomers with interesting nanostructural and spectroscopic properties

Conjugated Polymer Network Films from Precursor Polymers: Electrocopolymerization of a Binary Electroactive Monomer Composition

We report the synthesis and electropolymerization of a precursor polymer with a binary molecular composition of thiophene and carbazole electroactive groups to form ultrathin films of conjugated polymer networks (CPN) on flat indium tin oxide (ITO) substrates. In the past we have demonstrated the precursor polymer approach based on a single pendant electroactive group. In this work, we describe the interesting electrocopolymerization mechanism and properties of precursor polymers prepared with two different types of pendant electroactive groups (statistical copolymer) and compared behavior to their respective homopolymers. The presence of a smaller amount of carbazole induces the electropolymerization of the higher oxidation potential thiophene units via the reaction of a radical cation and a neutral molecule pathway. These electrochemically generated thin films gave unique optical, electrochemical, and morphological properties as a function of composition. The film properties were investigated by cyclic voltammetry (CV), spectroelectrochemistry, EQCM, atomic force microscopy (AFM), and X-ray photoelectron spectroscopy (XPS)

Surface-Initiated Ring-Opening Metathesis Polymerization (SI-ROMP): Synthesis and Electropolymerization of Terthiophene-Functionalized Olefin Peripheral Dendrons

We report on the synthesis and electrodeposition of peripheral olefin dendrons with electropolymerizable focal point terthiophene units. These films were utilized for surface initiated ring-opening metathesis polymerization (SI-ROMP) of norbornene to form grafted polynorbornene brushes. The dendrons were first electrodeposited on an electrode surface, forming a highly dense and uniform polythiophene-type film, and their electrochemical behavior was investigated. Subsequently, after activation with a transition metal metathesis catalyst, polynorbornene brushes were grown from the electrodeposited films which were found to be highly dependent on the density of exposed olefin functional groups and dendron generation. The change in film morphology was examined by atomic force microscopy (AFM). X-ray photoelectron spectroscopy (XPS) was used to prove polynorbornene brush film growth and composition on top of the electropolymerized layer. Brush growth kinetics experiments were also carried out to understand the correlation between the structure of the dendrons and polynorbornene brush growth mechanism. The method presented in this paper provides a facile route to prepare robust, uniform, and controllable polymer brushes grafted from an underlying π-conjugated polymer layer

Living Anionic Surface Initiated Polymerization (SIP) of Styrene from Clay Surfaces

Living Anionic Surface Initiated Polymerization (SIP) of Styrene from Clay Surface

Transient Three-Dimensional Orientation of Molecular Ions in an Ordered Polyelectrolyte Membrane

Single-molecule fluorescence spectroscopy is employed to reveal 3D details of the mechanisms underpinning ion transport in a polyelectrolyte thin film possessing polymer-brush nanoscale order. The ability to resolve fluorescence emission over three discrete polarization angles reveals that these ordered materials impart 3D orientation to charged, diffusing molecules. The experiments, supported by simulations, report global orientation parameters for molecular transport, track dipole angle progressions over time, and identify a unique transport mechanism: translational diffusion with restricted rotation. In general, realization of this experimental method for translational diffusion in systems exhibiting basic orientation should lend itself to evaluation of transport in a variety of important, ordered, functional materials