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Researchers at the Naval Air Warfare Center Weapons Division (NAWCWD) and Wright-Patterson Air Force Base (WPAFB) investigated poly[2-methoxy-5-(2’-ethylhexyloxy)-1,4-phenylene vinylene], (MEH-PPV) for its potential corrosion-inhibition properties on aerospace aluminum alloy AA2024-T3. Solution processing of the polymer, as well as adhesion testing and accelerated weathering tests were performed on MEH-PPV full military aerospace coatings. Wet and dry tape adhesion testing, as well as pencil hardness, impact flexibility and pneumatic adhesion tensile test instrument (PATTI) testing were used to demonstrate the adhesion performance of MEH-PPV on aluminum substrates. The results showed that MEH-PPV had acceptable adhesion characteristics when compared to hexavalent chromium (Cr(VI)) based coatings in all of these tests. Accelerated weathering analysis was performed on MEH-PPV coatings to determine their corrosion protection and weathering resistance capabilities. These tests included neutral salt spray (NSS) exposure and xenon-arc lamp testing. The results showed that while MEH-PPV does not exhibit significant color change after 500 hours of xenon arc lamp exposure, the polymer has poor corrosion protection performance under aggressive salt environments.

A novel processing technique was used to solution cast films of poly(benzimidazo benzophenanthroline), (BBL), and the novel ladder polymer poly(4-aza-benzimidazo benzophenanthroline) (Py-BBL), which were used as cathode materials in Type IV electroactive polymer-based electrochemical capacitors (EPECs). This new processing technique involves co-casting the polymer from solution with a room temperature ionic liquid, 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (EMIBTI). The new processing technique gave polymer films with superior transport properties and electrochemical stabilities, did not require a break-in period, and yielded higher charge capacity than the standard films. Co-cast films of BBL and Py-BBL were each incorporated into separate Type IV EPECs using poly(3,4-propylene dioxythiophene) (PProDOT) as the anode material. It was found that the PProDOT/BBL capacitors store, on average, about 50% more energy than a comparable PProDOT/Py-BBL EPEC. While PProDOT/BBL films have an energy density advantage at rates (power densities) less than 0.01 kW kg −1 , PProDOT/Py-BBL EPECs are capable of delivering higher energy than the BBL EPECs at rates greater than 0.01 kW kg −1 (550 s per cycle). In fact, PProDOT/Py-BBL devices delivered more than ten times the energy density of PProDOT/BBL devices at 0.5 kW kg −1 (50 s per cycle). The PProDOT/Py-BBL EPECs were cycled for 10,000 cycles at 65% depth of discharge and maintained 96% of the initial energy and power density, whereas the PProDOT/BBL EPECs were cycled under the same conditions and lost more than 35% of the initial energy and power density after only 2300 cycles.

Despite the availability of a large number of alkyl tetrahydrofurfuryl ethers that have a wide range of applications, pure bis(tetrahydrofurfuryl) ether (BTHFE) has not been previously synthesized. Here, we report the synthesis of BTHFE (consisting of the RR, SS, and meso stereoisomers) at greater than 99 % purity from tetrahydrofurfuryl alcohol, using (tetrahydrofuran‐2‐yl)methyl methanesulfonate as an intermediate. Additionally, we demonstrate that BTHFE can be used as a non‐volatile solvent in poly(3,4‐propylenedioxythiophene)‐based supercapacitors. Supercapacitor devices employing solutions of the ionic liquid 1‐ethyl‐3‐methyl‐imidizolium bis(trifluoromethylsulfonyl)imide in BTHFE display similar performances to those prepared by using the neat ionic liquid as an electrolyte, although solution‐based devices exhibit a somewhat higher resistance.

A general review of the chemistry and corrosion control properties of electroactive polymers will be presented. These polymers are also known as conductive polymers (CPs), and this term will be used throughout this article. This paper will focus on both the synthesis of applicable CPs used for corrosion protection in various environments and their potential benefits over common organic barrier coatings.

Recent results concerning the synthesis of new main-chain syndioregic nonlinear optical polymers are presented. In particular, the synthesis of polymers with extended pi conjugation in the chromophore and chromophores with improved thermal stability are presented. The nonlinear optical coefficient of several of the polymers and the optical loss at 1.3 and 1.55 μm were measured and are discussed. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 2824–2839, 2000

Using the method of aqueous solution alternating polyelectrolyte deposition (APD), second-order nonlinear optical (NLO) polymer films were prepared for the first time in which both polymers were NLO-active. Films were prepared by alternately coating a solid substrate with an NLO-active side chain polycation and an NLO-active main chain polyanion. This new polyanion was comprised of α-cinnamoyl chromophores in the syndioregic configuration (an “accordion” polymer). The new polycation was derived from polyepichlorohydrin that was completely substituted with new stilbazolium side chain. The films were transparent and had no texture when observed by polarized microscopy. The increase in intensity of the second harmonic (SH) signal generated in the films was quadratic with each molecular layer to 20 layers. Beyond that, the SH signal intensity saturated as more layers were added.

We report here recent progress toward the goal of processing polymers near room temperature to produce all-polymeric non-linear optical films which may ultimately find application as active waveguides. Polymers designed for spin-casting were found to be processable by the Langmuir–Blodgett–Kuhn (LBK) technique. The T g of the bulk polymer is about 240°C. The temporal stability of non-centrosymmetric order in LBK films at elevated temperatures was followed by measurement of the second harmonic generated (SHG) light intensity. The SHG signal was found to be constant in LBK films heated at 95°C for 10 h.

The design and synthesis of mainchain chromophore polymers in a syndioregic (head-to-head) configuration is described. Polymers were designed for both electric-field poling and Langmuir-Blodgett-Kuhn (LBK) deposition. LBK deposition gives intrinsically polar films (no E-field poling) as evidenced by nonlinear optical (χ (2) ) properties.

Poly(ethylene oxide) (PEO) and poly[oxymethylene-oligo(oxyethylene)](PEM) disks are cross-linked by exposure to UV radiation. The rate of formation of cross-links is greatly enhanced by the presence of benzophenone, and an average cross-link density of up to 6 mol% of ethoxy units can be obtained after irradiation. The highly cross-linked polymers are insoluble in water or organic solvents and show improved physical properties for handling and the formation of free-standing films. Dynamic modulus measurements and polymer swelling are employed to characterize the polymers. Dynamic modulus measurements show that, upon irradiation, PEO and PEM become cross-linked elastomeric solids.

A new main-chain syndioregic (head-to-head) NLO polymer was synthesized. The glass transition temperature of high molecular weight polymer was found to be 208°C, and the polymer has minimal weight loss at temperatures to at least 250°C owing to the incorporation of hydrogen bonding moieties and rigid bridging groups. The polymer was further characterized using nuclear magnetic resonance (NMR) and Fourier transform infrared spectroscopy (FTIR). The study of the nonlinear optical properties of this polymer are in progress. © 1993 John Wiley & Sons, Inc.

In the 1:1 radical cation salt, (trans-1,2-bis(2-naphthyl)ethene)SbF6, the naphthalene stacks of the corresponding 2:1 stoichiometric naphthalene salt are chemically bridged. The magnetic properties of this new organic semiconductor are analysed. The role of defects related to the disordered crystal structure and the influence of sample ageing have been discerned.

A single-crystal radical cation salt was obtained by anodic oxidation of trans-1,2-bis-(2-naphthyl)ethene (1,2-DNE) with SbF−6 as the counter-ion. The crystal structure of (1,2-DNE)SbF6 was solved and found to be similar to the radical cation salts of unsubstituted naphthalene. The crystal structure is disordered, i.e. two orientations of the 1,2-DNE molecules are statistically occupied. The molecular overlap, resulting from these two orientations, models the structure of the salt of poly(2,6-naphthylenevinylene). In contrast to most other radical cation salts which are one-dimensional conductors, a conduction mechanism of higher dimensionality is predicted on the basis of the crystal structure of (1,2-DNE)SbF6. The identical type of disorder is also present in the crystal structure of trans-1,2-bis(1-naphthyl)ethene.

Poly[(4-N-ethylene-N-ethylamino)-α-cyanocinnamate] was prepared by solution esterification of (4-N-ethyl-N-(2-hydroxyethyl) amino)-α-Cyanocinnamic acid and by melt transesterification of ethyl (4-N-ethyl-N-(2-hydroxyethyl) amino)-α-cyanocinnamate. The melt transesterification generally yielded polymer with a number-average molecular weight of about 10,200 by gel permeation chromatography (GPC) versus polystyrene standards. The polymer was found to be amorphous with a glass transition temperature of about 103°C by differential scanning calorimetry (DSC). The solution esterification generally gave a polymer with a number-average molecular weight of about 2200 by GPC versus polystyrene standards. This polymer was found to have a glass transition temperature varying between 60 and 90°C by DSC. The infrared (IR) spectrum of the polymer made from both methods were analyzed in detail. The 1H- and 13C-NMR spectra of the meltsynthesized ethyl cinnamate derivative polymer are consistent with the reported structure.

Films of poly(1,4-naphthalene vinylene) (P-1,4-NV) were obtained by the thermal elimination of a cycloalkylene sulphonium salt precursor polymer. The ultra-violet/visible (u.v./vis.), fluorescence and Raman spectra and the small-angle X-ray scattering diagrams were examined, and the oxidation and reduction potentials of P-1,4-NV were determined by cyclic voltammetry. The u.v./vis. spectra of P-1,4-NV films made from a sulphonium salt polymer based on the cyclic sulphide, tetrahydrothiophene, which was converted to P-1,4-NV at a temperature about 30°C lower than the temperature needed to obtain P-1,4-NV from the dimethylsulphide sulphonium salt polymer, showed phonon sidebands at room temperature as well as at −200°C. The phonon sidebands were apparently associated with a narrow distribution of crystallite sizes, which had an average long-period spacing of 140A, and was obtained when P-1,4-NV was made from the cyclic sulphonium chloride precursor polymer. The oxidation potential was found to be 0.75 V vs. SCE (saturated calomel electrode), the reduction potential was found to be −1.60V vs. SCE and the band-gap energy was found to be around 2.05V. The high value for the oxidation potential of P-1,4-NV, in comparison to the oxidation potential of triiodide (0.52V vs. SCE), from which an approximate value of 2 × 10 −8 for the oxidation equilibrium constant was obtained, explains why very low conductivities are obtained when P-1,4-NV is doped with iodine. Films of the cycloalkylene sulphonium salt precursor polymer could be drawn to as much as 1.6 times their original length, and the drawn films showed a significant degree of orientation according to X-ray diffraction and polarized infra-red spectroscopy.

We explore a number of polymer architectures with the objective of fabricating intrinsically polar polymer films for applications such as electro-optic switches and signal modulators for high bandwidth data processing. The goal of this work is to offer an alternative to the poled polymer approach in order to avoid high temperature processing and high electric fields. This paper reports progress toward achieving this goal.

The accordion polymer [CH 2 N(C 16 H 33 )PhCH=C(CN)CONHCH 2 CHOHCH 2 NHCOC(CN)=CHPhN(C 16 H 33 )CH 2 ] n is prepared by a Knoevenagel polycondensation. The Y-type multilayer of this polymer gave no second harmonic generation, which was not unexpected, because the dipole in adjacnet layers should be pointing in opposite direction

This is a preliminary report on alternating polyelectrolyte deposition (APD) with the goal of making electro-optic films at room temperature. By means of the APD method, films were built up layer-by-layer at room temperature by a dipping process. APD requires two complementary polymers, one being negatively charged and the other being positively charged. The polymer in solution is attracted to the solid substrate by coulombic forces to form the next layer on the substrate. For the first time, second-order nonlinear optical (NLO) polymer films were prepared by APD in which both polymers were NLO-active. The cationic polymer contained a side-chain stilbazole chromophore, and the anionic polymer contained a main-chain cinnamoyl chromophore. The intensity of the second harmonic signal generated in the film increased quadratically with each layer for the first twenty layers.

New thermally stable, spin-castable, electro-optic (EO) polymers designed for high frequency optical modulators are reported (the third generation accordion polymers). The softening temperature (the glass transition temperature) is about 240 degrees Celsius, and the upper limit on short term thermal baking stability is about 320 degrees Celsius. The refractive index at 1.3 microns is about 1.73 and fairly birefringent. The second-order nonlinear optic coefficient, d 33 , of a second generation accordion polymer containing essentially the same chromophore, measured by second- harmonic generation at 1.06 microns, is 120 pm/V (resonance enhanced by the 495 nm absorption). Measurement of the electro-optic coefficient, r 33 , is in progress. The added thermal stability in these polymers is due to the all- aryl amine electron donor. The molecular topology of the polymer backbone makes it possible for over 85 weight percent of the bulk material to be comprised of EO-active chromophore. The chromophores are configured in a head-to- head mainchain topology. The films are completely amorphous (no microcrystalline scattering sites).

Progress on second-order nonlinear optical polymers for high speed optical signal modulation is reported. New accordion polymers containing head-to-head backbone chromophores extended with a styryl-thienyl-vinyl linkage are described. The maximum absorption of the electronic transition (ground state yields excited state) for these polymers occurs at a wavelength of 494 nm. A corona-poled film of the ortho-xylyl bridged accordion polymer has a resonance-enhanced second- order nonlinear optical coefficient of 120 pm/V measured at 1.06 microns, and a glass transition temperature of about 187 degree(s)C. Along with linear polymer, polar cyclic dimers were formed during the polymerization. An extraction process was developed to remove the cyclic dimers from the polymer.

A long term objective of our work has been to identify and characterize the T cells responsible for causing autoimmune type I diabetes in the spontaneously diabetic BB rat. Based on the Th1/Th2 paradigm encompassing "regulated" and "regulatory" T cells, our analyses show that there are very few "regulatory" peripheral Th2 cells. The "regulated" T cells that remain express an unusual, immature phenotype that is neither Th1 nor Th2. Our data also indicate that transcript expression for p56lck, an enzyme required for T cell development, is abnormal in BB peripheral T cells. We discuss the role abnormal transcript expression of p56lck might play in retarding the development of mature regulatory Th2 cells while simultaneously influencing the escape of autoreactive T cells from the thymus.

The redox switching of some conducting polymers was investigated. Poly(3,4- ethylenedioxythiophene) and two of its alkyl derivatives were investigated in a liquid electrolyte to probe its usefulness as a visible electrochromic device. The other type of device is based upon actively changing the surface conductivity of one active layer of the device using conducting polymer: in one state the surface conductivity is high, in the other state the surface conductivity is low. Switching speed, contrast ratio, and overall lifetime for both devices were determined and discussed.

The synthesis and preliminary characterization of new polypeptide-bound chromophores are reported. These polymers were made for the purpose of assembling (beta) -sheets at an air- water surface, and processing them into nonlinear optical films by Langmuir-Blodgett (LB) deposition. These films should be amenable to integration on semiconductor wafers, e.g., as active optical waveguides for phase shifting.

An amorphous, nonlinear optical polymer, which has a glass transition temperature of 208 degree(s)C, was prepared. It is soluble in common organic solvents, and can be processed by conventional photolithographic processes. Corona-poled thin films of this polymer exhibit second-order nonlinear optical properties. This polymer is comprised of mainchain cinnamamide chromophores in the syndioregic configuration. The rigid U-shaped links which bridge the chromophores in this polymer were designed to geometrically stabilize polar, folded conformations in the backbone.

When the chromophores (dipoles) of a polymer are oriented electrically (electric field poling) and mobility is frozen below the glass transition temperature of the polymer, these materials can be used as frequency doublers (second harmonic generation (SHG)), and materials for waveguides and electro-optical devices.1

New nonlinear optical polymers (NLOP) having potential utility in waveguides for the modulation and switching of optical signals are reported. A new class of chromophoric polymers which assume a folded, polar conformation of the backbone have been prepared. The polymers have a syndioregic arrangement of chromophores within the backbone (i.e., a head-to-head, tail-to-tail configuration). Polymers were synthesized by the polymerization of difunctional, precoupled pairs of chromophores and difunctional, bridging groups. Glassy, noncentrosymmetric films were prepared by electric field poling and by Langmuir-Blodgett (LB) deposition. Characterization of multilayer LB films by null ellipsometry to determine the anisotropic refractive parameters was performed at different angles of incidence and at a wavelength of 1.0 (mu).

Head-to-tail mainchain chromophoric polymers have been of interest because of their high chromophore densities [about 30 X 1021 chromophores/cm3 in the case of poly(4-N-ethylene-N-ethylamino)-(alpha) -cyanocinnamate], their proposed tendency to align in an electric field more readily than unconnected chromophores, and the proposed enhancement of the macroscopic hyperpolarizability coefficients. These proposed properties have yet to be proven for the solid state. In fact, results on mainchain nonlinear optical polymers indicate that a much lower degree of alignment resulted than would be expected for unconnected dipoles. It is possible that the head-to-tail configuration of mainchain polymers has too high of an energy barrier to rotation and alignment to allow proper alignment of the dipoles. Therefore, a new class of mainchain polymers, namely head-to-head polymers connected with various flexible spacers (which may allow the dipoles to align) was developed. The synthesis and characterization of these new materials is described. The nonlinear optical properties of several of this new class of mainchain nonlinear optical polymers were compared to the properties of the head-to-tail mainchain polymers.© (1991) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

A novel donor-acceptor polymer based on thiophene and isopyrazole has been prepared for use in n-doping applications. Nonpolymerizable monomer radical cations appear to be the predominant oxidation product, resulting in a need for extended cycling to produce adequate quantities of polymer for characterization. The electrochemical behavior of the polymer films produced is strongly dependent upon the conditions applied during electrodeposition and on the solvent used during cycling of the films. Cycling to reductive potentials during oxidative polymerization in acetonitrile was necessary to produce a polymer film capable of n-doping, likely resulting from a need to establish pathways for cation migration. The neutral polymer undergoes oxidation to the p-doped form at ca. 2000 mV vs Ag/Ag + in propylene carbonate and reduces back to neutral at ca. 0 mV. Conversion of the neutral polymer to its n-doped form involves reductions at -700 and -1300 mV, with reoxidation at -800 and -200 mV to return to the neutral form of the polymer.

Films of poly( p -phenylene vinylene) (PPV) were prepared by thermal elimination reactions of two different sulphonium salt precursor polymers. The ultra-violet/visible (u.v./vis.), fluorescence and Raman spectra and small-angle X-ray scattering diagrams of each PPV sample were compared, and the oxidation and reduction potentials of each PPV were determined by cyclic voltammetry. The u.v./vis. spectra of PPV films made from a sulphonium salt polymer based on a cyclic sulphide, which was converted to PPV at a temperature about 100°C lower than that required to obtain PPV from an acyclic sulphide sulphonium salt polymer, showed phonon sidebands at room temperature as well as at −200°C. The phonon sidebands were apparently associated with a narrower distribution of crystallite sizes (with an average long period spacing of 300 A), which was obtained when PPV was made from the cyclic sulphonium chloride precursor polymer. The experimental values for the oxidation and reduction potentials and for the band gap were found to be in good agreement with the values predicted by ab initio calculations and from previous literature reports. The oxidation potential was found to be 0.80 V vs. SCE (saturated calomel electrode), the reduction potential was found to be −1.8 V vs. SCE, and the band-gap energy was found to be around 2.4 eV. The high value for the oxidation potential for PPV, in comparison to the oxidation potential of triiodide (0.52 V vs. SCE), from which an approximate value of 2 × 10 −10 for the oxidation constant was obtained, explains why only very low conductivities were obtained when PPV was ‘doped’ with iodine.

Preliminary, systematic measurements of the drawing process of sulfonium salt precursor polymer films were obtained using an Instron tensile tester equipped with an environmental chamber, both of which were interfaced with a computer to measure variables such as stress, temperature, and strain. Under the conditions in which highly oriented samples were obtained, at high strain rates and with high heating rates, orientation appeared to be dependent upon the rate of strain but not upon the total strain. Measurements of the storage and loss moduli at similar heating rates revealed that the loss modulus and the ratio of loss modulus to the storage modulus increased with increasing temperature. These results suggest that the solid sulfonium salt precursor polymer of poly(p-phenylenevinylene), PPV, undergoes a phase transition to form an intermediate, liquid-like state during the thermal elimination reaction. Experiments were also performed at a lower strain and heating rate, in which the orientation did depend upon the total strain. However, these polymer films were not as well oriented as were the films drawn at the higher strain and heating rates. Taken together, these results suggest that the transition to a liquid-like phase may be necessary in obtaining highly oriented samples.

Two new types of p-xylene bis-sulfonium chloride monomers were prepared from cycloalkylene sulfides. The polymerization characteristics of these monomers to form poly(p-xylene sulfonium chlorides), and the thermal elimination reactions of their polymers to poly(p-phenylene vinylene), were compared with those of two monomers prepared from dialkyl sulfides. The cycloalkylene sulfonium chloride monomer polymerized to higher yields and to higher molecular weight polymers, which showed more efficient elimination reactions.