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Carbon nanofibers (CNFs) were fabricated by thermal treatment of electrospun nanofibers obtained from precursor blends of polybenzimidazole (PBI) and Matrimid®. The microcarbon structures of CNFs obtained from PBI, and the 50:50 and 75:25 blends were studied using XRD and Raman spectra. Nitrogen adsorption/desorption measurements revealed that surface area and porosity of CNFs increased with an increase in Matrimid® content. Electrochemical performance of these CNF electrodes was studied for their application in energy storage devices. The CNFs from the PBI/Matrimid® (75:25)-precursor blend showed the lowest electrochemical impedance, and highest specific capacitance (111 F/g) and energy and power densities of 24 and 6 kW/kg, respectively. Steam activation and annealing further enhanced the performance resulting in a specific capacitance of 126 F/g, and energy and power densities of 49 and 7 kW/kg, respectively.

Graphene is a promising electrode material for energy storage applications. The most successful method for preparing graphene from graphite involves the oxidation of graphite to graphene oxide (GO) and reduction back to graphene. Even though different chemical and thermal methods have been developed to reduce GO to graphene, the use of less toxic materials to generate graphene still remains a challenge. In this study we developed a facile one-pot synthesis of deoxygenated graphene (hGO) via alkaline hydrothermal process, which exhibits similar properties to the graphene obtained via hydrazine reduction (i.e. the same degree of deoxygenation found in hydrazine reduced GO). Moreover, the hGO formed freestanding, binder-free paper electrodes for supercapacitors. Coin cell type (CR2032) symmetric supercapacitors were assembled using the hGO electrodes. Electrochemical characterization of hGO was carried out using lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) and ethylmethylimidazolium bis-(trifluoromethanesulfonyl)imide (EMITFSI) electrolytes. The results for the hGO electrodes were compared with the hydrazine reduced GO (rGO) electrode. The hGO electrode exhibits a energy density of 20 W h kg −1 and 50 W h kg −1 in LiTFSI and EMITFSI respectively, while delivering a maximum power density of 11 kW kg −1 and 14.7 kW kg −1 in LiTFSI and EMITFSI, respectively.

Carbon nanofibers were prepared using electrospinning and thermal treatment of a new precursor, poly(acrylonitrile-co-vinylimidazole). Raman spectroscopy confirmed carbonization. Steam activation resulted in high surface area of 1120 m2/g. Coin cells were assembled using ethylmethylimidazolium bis(trifluoromethylsulfonyl) imide (EMITFSI) as the electrolyte. Cyclic voltammetry showed classic box-like behavior of electrochemical double layer capacitors with specific capacitances ranging between 122 F/g (10 mV/s) and 86 F/g (300 mV/s). From Ragone plots, the maximum energy and power densities were 47.4 Wh/kg (0.5 A/g) and 7.2 kW/kg (5 A/g), respectively. Keywords: Carbon nanofibers, Supercapacitors, Copolymers, Electrospinning

Polyacrylonitrile/poly(methyl methacrylate) (PMMA) fibers containing graphene are prepared by the electrospinning method, and hierarchical porous carbon nanofibers (CNFs) are obtained after subsequent heat treatment. The hierarchical porous CNFs have an improved structure and properties because of the increased surface area, unique nanotexture and increased electrical conductivity due to the dispersion of graphene. The carbonized fiber exhibits a high surface area (over 500 m 2 g −1 ) as result of the narrow ultramicro- and mesopore size distributions (centered at approximately 0.7 and 3.7 nm, respectively), and a broad mesopore size distribution ranging from 10 to 50 nm. The hierarchical pore structures are introduced by the evolution of small gas molecules during the decomposition of the PMMA during heat treatment. The highest specific capacitance of the CNFs is 128 F g −1 , and the energy densities are 16.0–21.4 W h kg −1 in an aqueous solution and 75.0–58.2 W h kg −1 in an organic electrolyte over a power density range of 400–20,000 W kg −1 . Under constant current charging/discharging at 1 mA cm −2 for 100 cycles, the stability of the CNFs in a 6 M KOH aqueous electrolyte decreases by ∼17% compared with the initial specific capacitance value.

In this study, we explore the effect of the dialkoxy and dithioalkoxy side chains on the benzo [1,2-b:4,5-b′]dithiophene (BDT) unit by comparing the O-BDT homopolymer (O-PBDT), S-BDT homopolymer (S-PBDT), and S-BDT-alt-O-BDT copolymer (SO-PBDT) by computational calculations and experimental results. The polymers were prepared by Pd-catalyzed Stille coupling. Additionally, hole mobility and film morphology were studied by fabricating organic field effect transistors (OFETs) and using TappingMode AFM, respectively. The photovoltaic properties of the polymers were measured from fabricated PSC devices. The replacement of the alkoxy (−OR) groups with thioalkoxy (−SR) groups lowered the HOMO energy level of the conjugated polymers from 5.31 to 5.41 eV, and consequently enhanced Voc, while still preserving the excellent properties offered by the BDT-based polymers. Especially, high Voc of 0.99 V was achieved from S-PBDT polymer based PSC with up to 4.0% of PCE, which is one of the highest efficiencies reported f...

Exfoliated graphite nanoplatelet (xGnP) and V2O5 nanotube (VNT) composite electrodes were fabricated and tested as electrodes for supercapacitors. Enhancement of the electrochemical performance of the composite over its component materials was demonstrated using cyclic voltammetry (CV), constant current charge/discharge testing and electrochemical impedance spectroscopy in aqueous and organic electrolytes. The calculated specific capacitance of the composite was 35 F g−1 in the aqueous electrolyte and 226 F g−1 in the organic electrolyte at a scan rate of 10 mV s−1 using a three-electrode system. Asymmetric coin cell devices were fabricated using activated carbon cloth as the positive electrode and xGnP–VNT composite as the negative electrode. The energy and power densities in 1 M LiTFSI were 28 Wh kg−1 and 303 W kg−1, respectively, at a discharge current density of 250 mA g−1.

Novel proton conducting composite membranes were synthesized by blending Nafion ® polymer with sulfonated organosilicon dendrimers (G3-S). Blending G3-S with Nafion resulted in stable, flexible membranes with loadings up to 10% by weight. The high amount of sulfonic acid groups on the dendrimer increased the ion exchange capacity and improved the water retention capability of the composite membranes with less swelling. The proton conductivity of the composite membranes was higher at all measured temperatures under both high and low relative humidity conditions, compared to pure Nafion ® . The proton conductivity of Nafion ® increased from 0.086 S/cm (at 80 °C at 100% relative humidity) for the pure polymer to 0.156 S/cm for the 10 wt% loading of dendrimer.

Vanadium pentoxide (V2O5) layered nanostructures are known to have very stable crystal structures and high faradaic activity. The low electronic conductivity of V2O5 greatly limits the application of vanadium oxide as electrode materials and requires combining with conducting materials using binders. It is well known that the organic binders can degrade the overall performance of electrode materials and need carefully controlled compositions. In this study, we develop a simple method for preparing freestanding carbon nanotube (CNT)-V2O5 nanowire (VNW) composite paper electrodes without using binders. Coin cell type (CR2032) supercapacitors are assembled using the nanocomposite paper electrode as the anode and high surface area carbon fiber electrode (Spectracarb 2225) as the cathode. The supercapacitor with CNT-VNW composite paper electrode exhibits a power density of 5.26 kW Kg−1 and an energy density of 46.3 Wh Kg−1. (Li)VNWs and CNT composite paper electrodes can be fabricated in similar manner and show improved overall performance with a power density of 8.32 kW Kg−1 and an energy density of 65.9 Wh Kg−1. The power and energy density values suggest that such flexible hybrid nanocomposite paper electrodes may be useful for high performance electrochemical supercapacitors.

Lead-based nanocrystals (NCs) are promising materials for high-efficiency solar cells since they are able to generate multiexcitons with high efficiency. One complication of utilizing these NCs is the insulating ligands capping their surfaces. In this paper, we have successfully developed and characterized a phosphonate-functionalized poly-3-hexylthiophene (POP3HT-50) and used it in the direct synthesis of PbS NCs within the polymeric host matrix without extraneous ligands. Devices made of POP3HT-50/PbS nanocomposites show an order of magnitude improvement in η when compared to that reported for a P3HT/ PbS device (η = 0.011% versus 0.001%). The improved performance is consistent with better electronic contact between PbS NCs and POP3HT-50.

Zeolitic imidazolate frameworks (ZIFs), that have the potential for gas separation, were used as additives in mixed-matrix membranes (MMMs). ZIF-8, which exhibits the sodalite topology, is composed of zinc (II) ion clusters linked by imidazolate ligands. The ZIF-8 pore aperture is 3.4 A allowing it to readily absorb small molecules such as H 2 and CO 2 . ZIF-8/Matrimid ® MMMs were fabricated with loadings up to 80% (w/w), which are much higher than the typical loadings achieved with select zeolite materials. Only at the highest loading did the ZIF-8/Matrimid ® MMM show a loss of mechanical strength, leading to a decrease in flexibility. The ZIF-8/Matrimid ® MMMs permeability properties were tested for H 2 , CO 2 , O 2 , N 2 , CH 4 , C 3 H 8 , and gas mixtures of H 2 /CO 2 and CO 2 /CH 4 . The permeability values increased as the ZIF-8 loading increased to 40% (w/w). However, at higher loadings of 50% and 60% (w/w), the permeability decreased for all gases, and the selectivities increased consistent with the influence of the ZIF-8 additive. The ideal selectivities of gas pairs containing small gases, such as H 2 /O 2 , H 2 /CO 2 , H 2 /CH 4 , CO 2 /CH 4 , CO 2 /C 3 H 8 , and H 2 /C 3 H 8 , showed improvement with the 50% (w/w) ZIF-8 loading, demonstrating a transition from a polymer-driven to a ZIF-8-controlled gas transport process. In control experiments using as-synthesized ZIF-8 with filled pores, there was no transition at 50% (w/w) loading. This may be the first example of an MMM wherein molecular sieving is evident and suggests that additive loadings >50% (w/w) may be required to observe this effect in MMMs.

Carbon nanofibers (CNFs) are promising electrode materials for electrochemical double layer capacitors due to their high porosity and electrical conductivity. CNFs were prepared by electrospinning and subsequent thermal treatment of a new precursor polymer, 6FDA-durene, without the addition of pore generating agents. The conversion of precursor nanofibers into CNFs was confirmed using Raman spectroscopy. CNFs were activated and annealed, and nitrogen adsorption/desorption measurements were conducted to determine surface area and porosity. These activated/annealed CNFs were used as binderless electrodes in coin cells with an ionic liquid electrolyte. The devices displayed a specific capacitance of 128 F g−1, an energy density of 63.4 Wh kg−1 (at 1 A g−1), and a power density of 11.0 KW kg−1 (at 7 A g−1).

Low efficiencies and costly electrode materials have limited harvesting of thermal energy as electrical energy using thermo- electrochemical cells (or "thermocells"). We demonstrate thermocells, in practical configurations (from coin cells to cells that can be wrapped around exhaust pipes), that harvest low-grade thermal energy using relatively inexpensive carbon multiwalled nanotube (MWNT) electrodes. These electrodes provide high electrochemically accessible surface areas and fast redox-mediated electron transfer, which significantly enhances thermocell current generation capacity and overall efficiency. Thermocell efficiency is further improved by directly synthesizing MWNTs as vertical forests that reduce electrical and thermal resistance at electrode/substrate junctions. The efficiency of thermocells with MWNT electrodes is shown to be as high as 1.4% of Carnot efficiency, which is 3-fold higher than for previously demonstrated thermocells. With the cost of MWNTs decreasing, MWNT-based thermocells may become commercially viable for harvesting low-grade thermal energy.

Single-particle fluorescence spectroelectrochemistry was used to investigate the electrochemical oxidation of isolated, immobilized particles of the conjugated polymers BEH-PPV and MEH-PPV at an indium tin oxide (ITO) electrode immersed in an electrolyte solution. Two types of particles were investigated: (i) polymer single molecules (SM) and (ii) nanoparticle (NP) aggregates of multiple polymer single molecules. For the BEH-PPV polymer, the observation of nearly identical lowest oxidation potentials for different SM in the ensemble is evidence for effective electrostatic screening by the surrounding electrolyte solution. A combination of Monte Carlo simulations and application of Poisson-Boltzmann solvers were used to model the charging of polymer single molecules and nanoparticles in the electrochemical environment. The results indicate that the penetration of electrolyte anions into the polymer nanoparticles is necessary to produce the observed narrow fluorescence quenching vs oxidation potential curves. Finally, fluorescence-lifetime single-molecule spectroelectrochemical (SMS-EC) data revealed that at low potential an excited state reduction process (i.e., electron transfer from ITO to the polymer) is probably the dominant fluorescence quenching process.

The electrospinnability of pitch was improved by blending in a solution of polyacrylonitrile (PAN) resulting in the reduction of the average fiber diameter from 2000 to 750 nm. Activated carbon fibers (ACFs) derived by stabilization, carbonization and steam activation at 700, 800, and 900 °C of the PAN/pitch electrospun fibers for 60 min were investigated as electrodes for supercapacitors. The Brunauer, Emmett, Teller (BET) specific surface area ranged from 732 to 1877 m 2 g -1 and the specific capacitance from 75.5 to 143.5 Fg -1 , depending on the activation conditions. Electrodes from the electrospun web activated at 900 °C exhibited a particularly quick response showing a high frequency of 5.5 Hz at a phase angle of-45° of the impedance spectroscopy.

Poly(p-phenylenevinylene) (PPV) derivatives have long been studied because of their attractive opto- and electroluminescent properties and have potential applications for devices such as light-emitting diodes and photovoltaics. The ability to induce alignment of these PPV derivatives may lead to the enhancement of charge mobility and their efficiency. In this study, uniform nanofibers of poly[2,5-(2'-ethylhexyloxy)]-1,4-phenylenevinylene (BEH-PPV) have been fabricated through the method of electrospinning, and an induced alignment of the polymer fibers was observed through photoluminescence data. This study also focuses on the doping of these fibers with the fullerene derivative, 1-(3-methoxycarbonyl)-propyl-1-phenyl-(6,6)-C(61) (PCBM), to induce more incidence of donor/acceptor junctions. Composite fibers with up to a 1:2 weight ratio of PCBM/BEH-PPV have been fabricated and exhibited an ability to quench the photoluminescence of BEH-PPV, indicative of charge transfer.

Injecting high electronic charge densities can profoundly change the optical, electrical, and magnetic properties of materials. Such charge injection in bulk materials has traditionally involved either dopant intercalation or the maintained use of a contacting electrolyte. Tunable electrochemical charge injection and charge retention, in which neither volumetric intercalation of ions nor maintained electrolyte contact is needed, are demonstrated for carbon nanotube sheets in the absence of an applied field. The tunability of electrical conductivity and electron field emission in the subsequent material is presented. Application of this material to supercapacitors may extend their charge-storage times because they can retain charge after the removal of the electrolyte.

Chemical oxidative polymerization of aniline using peroxydisulfate oxidant in aqueous pH 2.5–10.0 buffers yields electrically insulating brown powders that are believed to be mixtures of Michael-type adducts of benzoquinone monoimine and aniline at various stages of hydrolysis. A spectroscopically similar product is formed when solid 1,4-benzoquinone is added to an aqueous solution of aniline at room temperature in the absence of peroxydisulfate. This suggests that the peroxydisulfate oxidant in the aniline/S2O82− system provides a pathway for the formation of benzoquinone monoimine as an intermediate. Benzoquinone monoimine intermediate could be formed as a result of a Boyland–Sims rearrangement of aniline proceeding via the intermediacy of p-aminophenyl sulfate. Benzoquinone monoimine undergoes a series of conjugate 1,4-Michael-type addition/reoxidation/coupling steps with aniline or p-aminophenyl sulfate yielding the oligoaniline product. The precipitate that is isolated is also in the midst of two simultaneous pH dependent hydrolysis reactions: (i) hydrolysis of the imine groups to quinone, and (ii) hydrolysis of arylsulfates to phenols. The ratio of hydrolysis in each case was determined by the C/N ratio and sulfur elemental analysis values yielding analytical data that is consistent with experimentally determined values and also with our proposed reaction scheme. These findings offer a rationale for the high C/N ratios (>6.0) frequently observed in these systems while tracing the genesis of the residual sulfur in the product to unhydrolyzed arylsulfate. The oligoaniline product has previously been reported to have a novel poly-aza structure consisting of continuously linked –N–N–N– bonds, and alternately also reported to consist of phenazine-type linkages. This study is consistent with the latter and describes a pathway to phenazine coupling through a second and third stage hydrolysis of the arylsulfate and reoxidation with peroxydisulfate. There is no pathway for the formation of linear –N–N–N– linkages in the aniline/benzoquinone adduct and the striking similarity between its spectroscopic properties and the aniline/S2O82− adduct suggests that it is not a preferred pathway under these experimental conditions.

Metal–organic framework 5 (MOF-5) nanocrystals with a high surface area (3000 m 2 /g) and high thermal stability (up to 400 °C) were synthesized and added to Matrimid ® to form mixed-matrix membranes for gas separations. Scanning electron microscopy (SEM) images of the membrane cross-sections revealed significant plastic deformation of the polymer matrix owing to the strong affinity between the MOF-5 and Matrimid ® . At 30% MOF-5 loading, the permeabilities of the gases tested increased 120% while the ideal selectivities remained constant compared to Matrimid ® . Residual gas analysis of permeates of gas blends with different mixture ratios revealed an increase in selectivity for CH 4 .

Novel polysilsesquioxane (R–Si–(O)1.5) PEMs with highly cross-linked Si–O backbones and pendant organic side chains comprising propylsulfonic or ethylphosphonic acid groups, were prepared via sol-gel polymerization. The inorganic component provides thermal/mechanical/chemical stability while the organic component gives flexibility and proton-conducting properties. The propylsulfonic acid membranes exhibited proton conductivities (σ) up to 10−2 S/cm at high relative humidities and temperatures, while the ethylphosphonic acid membranes showed lower proton conductivities but higher thermal stabilities. Preliminary results for the propylsulfonic acid membranes in direct methanol fuel cell (DMFC) performance are reported.

Mixed-matrix membranes were prepared from Matrimid® and mesoporous ZSM-5 nanoparticles containing crystalline ZSM-5. The ideal selectivity for H2/N2 separation increased from 79.6 for pure Matrimid® to 143 at 10% loading, while the selectivity of O2/N2 increased from 6.6 for pure Matrimid® to 10.4 at 20% loading. The ideal H2/CH4 separation factor increased from 83.3 to 169 at 20% loading. The results suggest that the mesopores of the ZSM-5 material provide good contact between the nanoparticles and the polymer, since the polymer chains can penetrate into the mesopores. The micropores of ZSM-5 crystals provide size and shape selectivity.

The polymerization to polyaniline nanofibers was carried out in an aqueous system using aniline, 1 M HCl. and ammonium peroxydisulfate (APS) with additional use of sodium hypochlorite solution as a co-oxidant. The addition of sodium hypochlorite solution was made either before or after the addition of APS. This new method always produces polyaniline nanofibers with long length. Additional advantages of this new method are discussed. The effect of aniline concentration, hypochlorite concentration, different acid use, reaction temperature, and both aniline and hypochlorite purity on morphology and electrical property of the nanofibers synthesized by this new method was investigated.

Linear meta -polyaniline ( m -PAni) has been synthesized and proton-conducting polymer membranes have been prepared through solution casting of acid-doped m -PAni. The obtained membranes show good proton conductivities at temperatures above 100 °C, achieving 10 −2.7 S/cm at 120 °C under extremely low-humidity conditions. The effect of doping acids, doping levels and humidity, on the conductivity is discussed.

A microporous metal-organic framework Cu–4,4′-bipyridine–hexafluorosilicate (Cu–BPY–HFS), having a surface area of 2000 m2/g, was combined with Matrimid® polymer to form free standing films. The permeability properties of Cu–BPY–HFS–Matrimid® mixed-matrix membranes were tested for the pure gases H2, N2, O2, CH4, and CO2 and the gas mixtures CO2/CH4, H2/CO2 and CH4/N2. The ideal selectivity of CH4/N2 increased from 0.95 to 1.21, which suggests that Cu–BPY–HFS has a strong affinity towards CH4 and favors its permeation. The higher solubility of CH4 in the membranes leads to higher selectivity for CH4/N2. The enhanced CH4 transport is also apparent in the case of ideal selectivity for CO2/CH4 and H2/CH4. For CH4/N2 gas mixtures, the selectivity increased from 0.95 to 1.7. The Cu–BPY–HFS's affinity towards CH4, and its large surface area increased the solubility of CH4 in the mixed-matrix membranes, which led to higher selectivity towards CH4.

A carbon aerogel was prepared by carbonizing a resorcinol−formaldehyde polymer gel at 800 °C. Nitrogen adsorption shows the obtained carbon aerogel has both micropores (0.54 nm) and mesopores (2.14 nm). Matrimid mixed-matrix membranes containing the carbon aerogels were successfully prepared and evaluated for the permeation of H2, N2, O2, CH4, CO2, and gas mixtures. The ideal selectivity of H2/N2, CO2/CH4, and O2/N2 gas pairs increased from 79.6, 34.5, and 6.6 for pure Matrimid to 111, 47.8, and 9.1 at 20% loading, respectively. These results suggest that the polymer chains can penetrate the carbon mesopores to achieve good contact between the carbon aerogel and Matrimid, while the micropores may provide size and shape selectivity.

Mesoporous benzene silica (MBS) composites were synthesized and their physical properties were investigated. Three different MBS samples were prepared using octadecyltrimethylammonium chloride, vitamin E TPGS, and Pluronic 123 block copolymer as structure directing agents, respectively. The template extracted MBS samples were heat treated to 1000 °C under argon to carbonize the benzene rings in the pore walls to form a graphitic structure. These carbon/SiO 2 composites were treated with HF to dissolve the SiO 2 . The materials were characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, and nitrogen adsorption. The MBS samples 1–3 had pore sizes of 2.73, 3.35, and 5.52 nm, respectively. The carbon materials CBS samples 1–3 prepared in this study were microporous ( 2 /g.

We report the first results on conformal deposition of parylene on plastic solar cells, and study the effects of protection on performance characteristics of polymer solar cell. We show that single parylene coating layer is not a very effective barrier even for thicknesses as large as 10 μm. Our results support the experimental observations that the main degradation processes in poly(3-hexylthiophene) are the oxygen-assisted photochemical reactions, such as photobleaching and chain scission. Multilayer barriers made of parylene and aluminum oxide coatings are very promising for full protection of organic solar cell from degradation even under intense AM1.5 solar light.

Electrospinning has been used to produce mesoporous metal oxide fibers with diameters in the nanometer to submicron range. The mesoporous metal oxide fibers include TiO 2 , Ta 2 O 5 , TaNbO 5 as well as the crystalline Nb 2 O 5 and VTiO 2 . The structure directing agents Pluronic P-123 [(EO) 20 –(PO) 70 –(EO) 20 ] and Brij 76 [C 18 H 37 (OCH 2 OCH 2 ) 10 OH], were used to generate the mesopores in the fibers. The fibers were characterized by XRD, scanning electron microscopy and surface area analysis. In the case of TiO 2 and Ta 2 O 5 the first examples of mesoporous molecular sieve papers were generated. The papers and fibers remain intact even after heating to 900 °C.

A detailed study of the postproduction heat treatment of organic solar cells based on regio-regular poly(3-hexylthiophene) (RR-P3HT) and [6,6]-phenyl-C61 butyric acid methyl ester (PCBM) is presented. The efficiency of the devices was significantly improved by postproduction heat treatment and both the optimal annealing temperature and optimal annealing time were determined. The phase separation of PCBM and RR-P3HT into bi-continuous network structure occurs within a very short period of time and is very stable.

Mesoporous SBA-15/polyaniline composites were synthesized and their physical properties were investigated. The polyaniline was polymerized inside the pores of the mesoporous material by a post-synthesis process as well as an in one step process during the preparation of the molecular sieve. These materials were characterized by X-ray diffraction, scanning electron microscopy and nitrogen adsorption. The composite polyaniline/SBA-15 was electrically insulating (dc conductivity ∼10 −8 S/cm) and produced proton conductivities of up to 10 −2 S/cm when doped with HCl.

Tungstosilicate mesoporous materials (WMM) were synthesized using the ionic surfactant cetyltrimethylammonium bromide (C 16 H 33 N + (CH 3 ) 3 Br − , CTMABr) and non-ionic surfactants, including C 12 H 25 (OCH 2 CH 2 ) 10 OH (Brij 22, C 12 EO 10 OH), C 16 H 33 (OCH 2 CH 2 ) 10 OH (Brij 56, C 16 EO 10 OH), and C 18 H 37 (OCH 2 CH 2 ) 10 OH (Brij 76, C 18 EO 10 OH). Using CTMABr, the highest W/Si ratio achieved for the molecular sieve product was 0.03. The proton conductivity ranged from 0.5 to 2.2 × 10 −2 S/cm, where the highest conductivity was observed with the H 3 PO 4 based preparation. Non-ionic surfactants produced materials with a W/Si ratio as high as 0.05 without any dense WO 3 impurities. These samples showed thicker pore walls (39 A), higher thermal stability, and higher proton conductivity (4.0 × 10 −2 S/cm). The WMMs were also employed to make a composite membrane with linear polyethyleneimine (PEI)-3-glycidoxypropyl-trimethoxysilane (GLYMO)-bis(trifluoromethanesulfonyl)imide (HTFSI). At 100 °C and 100% relative humidity, the composite membrane with 30 wt.% calcined (at 500 °C) WMM showed the highest conductivity of 6.1 × 10 −2 S/cm. At 130 °C and 20% relative humidity, the highest conductivity of 6.4 × 10 −3 S/cm was obtained for the composite membrane with 30 wt.% as-synthesized WMM.

The electronic dopants, like tetrafluorocyanoquinodimethane (F 4 –TCNQ) molecules, used for p-doping of hole transport layers in organic light-emitting diodes (OLEDs) are found to quench the electroluminescence (EL) if they diffuse into the emissive layer. We observed EL quenching in OLED with F 4 -TCNQ doped N,N′-diphenyl-N′N′-bis(1-naphthyl)-1,1′-biphenyl-4,4′-diamine hole transport layer at large dopant concentrations, >5%. To separate the effects of exciton–dopant quenching, from exciton–polaron quenching we have intentionally doped the emissive layer of (8-tris-hydroxyquinoline) with three acceptors (A) of different electron affinities: F 4 -TCNQ, TCNQ, and C 60 , and found that C 60 is the strongest EL-quencher, while F 4 -TCNQ is the weakest, contrary to intuitive expectations. The new effects of charge transfer and usually considered energy transfer from exciton to neutral (A) and charged acceptors (A − ) are compared as channels for non-radiative Ex–A decay. At high current loads the EL quenching is observed, which is due to decay of Ex on free charge carriers, hole polarons P + . We consider contributions to Ex–P + interaction by short-range charge transfer and describe the structure of microscopic charge transfer (CT)-processes responsible for it. The formation of metastable states of ‘charged excitons’ (predicted and studied by Agranovich et al. Chem. Phys. 272 (2001) 159) by electron transfer from a P to an Ex is pointed out, and ways to suppress non-radiative Ex–P decay are suggested.

Continuous carbon nanotube composite fibers having record energy-to-break (toughness) are reported. These fibers have been employed in the fabrication of lightweight fiber supercapacitors, which can be woven or sewn into fabrics and, therefore, be potentially considered as components for electronic textiles. Moreover, these fibers provided remarkable electromechanical actuator capabilities.

There is growing interest in new ways to configure titanium dioxide (TiO 2 ) as new applications emerge such as in photovoltaics and catalysis. A method has been developed for the preparation of mesoporous TiO 2 fibers using electrostatic deposition. The mesoporous metal oxide fibers were prepared using Pluronic 123 as the template. The fibers contain anatase crystallized in the pore walls which transforms to rutile upon calcination above 800 °C. The electrospun fibers were evaluated for the photodecomposition of phenol and formic acid.

A generic topochemical route for the rational synthesis of carbon single walled nanotubes (SWNTs) of one specified type is proposed and analyzed using theoretical and experimental results. This route uses crystal-controlled 1,4-addition polymerization of diacetylene groups in cyclic monomer molecules to make organic nanotubes, whose three-dimensional covalent network combines carbon–carbon bonds of the cyclic monomer and four parallel polydiacetylene chains formed by solid-state reaction. Up to 75% of the carbon–carbon bonds of the target carbon nanotube are correctly connected in the organic nanotube, and none are incorrectly connected. Target monomers are down selected by using molecular mechanics calculations to predict the allowable crystal packing parameters, from which topochemical reactivity is predicted using a well-established reactivity diagram. This approach correctly predicts the solid-state polymerizability of a cyclic diacetylene that we experimentally demonstrated forms a targeted hydrocarbon nanotube. Substituent extrusion is the final step in forming the carbon nanotube from the organic nanotube, which should occur cleanly because the covalent connectivity of the organic nanotube holds the structure in place. Using this two-step topochemical control of reaction and structure, during formation of the organic nanotube and during substituent extrusion, routes to armchair and zigzag SWNTs having different ring diameters are proposed.

The process of electrospinning, which produces fibers in the nanometer to micron range under the influence of high voltages, has been widely studied to produce polymer and textile fibers. Mesoporous molecular sieve fibers have been produced in our lab, and this technique was extended to produce an interwoven mesh of polymer-molecular sieve composite fibers. The electroluminescent polymer MEH-PPV and molecular sieve SBA-15 were used to produce the composite fibers. An interesting aspect of these composites is that the fluorescence of MEH-PPV is blue shifted in the composites. The composites have been characterized by microscopy, vibrational spectroscopy, and fluorescence measurements.

The optical properties of high quality single crystals of distyrylbenzene (DSB) have been studied. At room temperature the photoluminescence (PL) spectrum is quite broad with quantum yield of 65%. At low temperature the PL spectrum shows many narrow vibrational side bands with QE of 68%, where the 0–0 band shows different polarization properties from the other phonon bands. We used the Spano ‘pinwheel’ model of strong vibration–exciton coupling in herringbone lattice to explain the appearance of the ‘forbidden’ 0–0 transition at low temperature and its unusual polarization properties. This model also predicts a strong temperature dependence for the 0–0 band relative to the 0– n transitions, as verified experimentally.

Inverse gold photonic crystals templated from synthetic opals with a face centered cubic (FCC) crystal lattice were constructed by heat converting gold chloride to metallic gold. Tetrahedral formations constructed of alternating large and small octahedrons oriented in the zinc sulfide structure were created by controlling the infiltration of gold chloride. Silica spheres were coated with polyanilinesulfonic acid, polypyrrole, poly[2-methoxy-5-(2′-ethylhexyloxy)-1,4-phenylenevinylene] (MEH-PPV) and 5 nm colloidal gold. Ordinary yeast cells were coated with polyanilinesulfonic acid, polypyrrole and 5 nm colloidal gold. Spheres coated with MEH-PPV were dispersed in H2O and coated with polyelectrolytes which recharged and sterically stabilized the colloidal surfaces. The recharged spheres self-assembled by sedimentation with a FCC crystalline lattice possessing 500 μm wide and 1 mm long crystallites. Silica spheres with diameters as large as 1500 μm were self-assembled along the [1 0 0] direction of the FCC crystal lattice. Opals infiltrated with gold and opals constructed from polymer coated spheres were co-infiltrated with polypropylene yielding inverse polypropylene composite photonic crystals.

Electrospun fibers comprising mesoporous molecular sieve materials are described. In an aspect of the invention, fibers are electrospun from a conducting solution to which a high voltage electric current is applied. The apparatus includes in one aspect one or more conducting solution introduction devices for providing a quantity of conducting solution, said conducting solution introduction devices being electrically charged thereby establishing an electric field between said conducting solution introduction devices and a target, and means for controlling the flow characteristics of conducting solution from said one or more conducting solution introduction devices.

The gas transport properties of surface-treated poly(3-(2-acetoxyethyl)thiophene) (P3AcET) membranes are reported. Base or acid catalyzed hydrolysis of the ester group of P3AcET yields poly(3-(2-hydroxyethyl)thiophene) (P3HET), a highly permselective conducting polymer. Permeability coefficients were determined for as-cast P3AcET membranes (PCO2=1.42, PO2=0.24, PN2=0.05, PCH4=0.08 Barrers) and selectivity values were calculated (O2/N2=5.1, CO2/CH4=18.5). Formation of a thin selective P3HET surface layer resulted in an overall decrease in permeance (P/l) accompanied by a dramatic increase in selectivity for both the base-treated (O2/N2=12.9, CO2/CH4=20.0) and acid-treated (O2/N2=11.7, CO2/CH4=45.0) composites. Microscopic (AFM, SEM) and spectroscopic (ATR-FTIR) characterization of the thin film composites confirmed the surface specificity of the hydrolysis reaction.

Electrochromic devices composed of laminated polymer layers, as the working electrode, and vanadium pentoxide, as the counter electrode, were prepared and evaluated. Three different laminate systems were investigated using various combinations of poly(3,4-ethylenedioxythiophene), poly(N-methylpyrrole), and polyaniline as the active electrochromes. The color change of the laminate devices was measured using spectrocolorimetric techniques and analyzed using Commission Internationale de l'Eclairage 1931 (x, y)-chromaticity coordinates. The device's observed colors in their fully doped and dedoped states are found to be linearly dependent on the color coordinates of the two individual polymers that comprise the laminate.

In this study, we have explored the first use of the siliceous MCM-41 molecular sieve as an additive to enhance the gas permeability characteristics of a high-performance polysulfone. For all gases...

Mechanistic studies on the polymerization of α,α‘-dibromo-2-methoxy-5-(2-ethylhexyloxy)xylene have been performed. Polymerizations were initially carried out by adding potassium tert-butoxide to monomer in the presence of a chain transfer agent, anthracene. Anthracene showed little effect on the molecular weight of the resulting polymer, suggesting that the major polymerization route was not radically initiated. Polymerizations were also carried out by adding monomer to potassium tert-butoxide in the presence of a nucleophile, 4-methoxyphenol. The molecular weight of the resulting polymer scaled linearly with the amount of 4-methoxyphenol, suggesting an anionic mechanism. In addition, each polymerization was monitored by in-situ torque measurements to further elucidate the polymerization mechanism and optimize polymerization conditions.

We present for the first time a novel strategy of producing carbon nanofibers (CNFs) using polyacrylonitrile (PAN)-incorporated with iron oxide particles using electrospinning method. The successfully electrospun iron oxide-incorporated PAN thin white web was stabilized in air. Formation of iron oxide nanoparticles resulted in the formation of porous structure on the web. Following heat treatment to the stabilized fibers to about 1000 °C in an N2 atmosphere resulted in CNFs with specific surface areas, which ranged from 310, 420, and 550 m2 g− 1, for PAN containing 1, 2 and 3 wt.% iron oxide, respectively.

Three compositionally different copolymers derived from N-vinylcarbazole and N-phenyl-2-(5′-vinyl-2′-thienyl)-5-(2″-thienyl)-pyrrole were synthesised chemically and characterised. The composition of the copolymers was estimated using FT-IR spectroscopy and in situ spectroelectrochemistry and spectrocolorimetric measurements were performed on the solid state electrochromic devices fabricated using these copolymers as working electrodes. The colour contrasts of these devices in both the neutral and the doped states were measured by spectrocolorimetry conforming to the Commission International de l'Eclairage (CIE) methods. The CIE colour coordinate values in the p-doped state of the devices could be correlated to the comonomer ratios in these copolymers.

The ability to tune colour constitutes an important goal in the design of electrochromic devices. The majority of single electrochromic materials, whether inorganic or organic have a very narrow spectral colour change, however. Complex colours such as browns and tans that mimic natural vegetation and soils are not inherent to these materials. We have explored several strategies to achieve these colours including the use of copolymers that contain two distinct moieties, blends of polymers that have different colour changes, laminating two different polymers on the working electrode, and using fine patterns of two different materials to confuse the eye. We have constructed solid state electrochromic devices using ITO/Mylar substrates, a solid polymer electrolyte, a V2O5 counterelectrode and working electrodes that were made via one of the four methods outlined above. The colour changes of these devices were measured using spectrocolourimetry conforming to the CIE standard. The colour changes observed were similar to those of natural vegetation and soils.

Solution cast membranes of poly(3-dodecylthiophene) (PDDT) were studied for the room temperature separation of N 2 , O 2 , and CO 2 . A procedure for fabricating reproducible, smooth, uniformly thick (∼35 μm), defect-free membranes is described. Permeability values were measured for as-cast PDDT membranes ( P N 2 =9.4, P O 2 =20.2, P CO 2 =88.2 Barrers) and selectivity values were calculated ( α O 2 /N 2 =2.2, α CO 2 /N 2 =9.4). Chemically induced oxidation (∼23%) with SbCl 5 resulted in a decrease in permeability ( P N 2 =3.5, P O 2 =10.5, P CO 2 =48.5 Barrers) and a corresponding increase in permselectivity ( α O 2 /N 2 =3.0, α CO 2 /N 2 =14.0). Reduction of the oxidized membrane with hydrazine partially reversed these trends ( P N 2 =5.4, P O 2 =15.1, P CO 2 =62.9 Barrers, α O 2 /N 2 =2.8, α CO 2 /N 2 =11.6). The chemical compositions of as-cast, oxidized, and hydrazine-treated PDDT membranes were determined using elemental analysis and energy dispersive X-ray spectrometry. Membrane microstructure was investigated by optical microscopy, TappingMode™ atomic force microscopy and scanning electron microscopy. The composition and microscopy results were correlated with changes in gas-transport properties.

We report femtosecond transient-absorption (TA) studies of a five-ring oligomer of poly({ital para}-phenylene vinylene) prepared in two different forms: solid-state films and dilute solutions. At high pump fluences, in both types of samples, we observe generation of two-exciton states, which are detected by the evolution of TA spectra and dynamics with increasing pump intensity. In solutions, double excitation of molecules results in the formation of stable biexcitons with enhanced oscillator strength, leading to an increased efficiency of the radiative decay and a superlinear pump dependence of the stimulated emission. In solid-state samples, the two-exciton states are unstable and decay on the subpicosecond time scale due to ultrafast charge transfer, accompanied by generation of interchain excitons. {copyright} {ital 1998} {ital The American Physical Society}