Preparation of one-dimensional polymer films by modification of a hydroxymethylbenzene self-assembled monolayer on iron with alkyltriethoxysilanes for preventing iron corrosion

A self-assembled monolayer (SAM) of p-hydroxymethylbenzene HOCH₂C₆H₄ - (HOMB) moiety adsorbed on iron by the formation of a covalent bond between carbon and iron atoms was prepared by electrochemical derivatization of an iron electrode with p-hydroxymethylbenzenediazonium tetrafluoroborate HOCH₂C₆H₄N₂BF₄. The electrode covered with the HOMB SAM was modified with alkyltriethoxysilanes C_nH_2n+1Si(OC₂H₅)₃ (C_nTES, n = 8 or 18) to prepare a film of one-dimensional polymer. The protective ability of the polymer film was determined by polarization measurement of the covered electrode in an aerated 0.5 M NaCl solution. The ability was enhanced by modification of the HOMB SAM with C_nTES markedly. The iron surface coated with the one-dimensional polymer film of the HOMB SAM modified with C₈TES was characterized by contact angle measurement and FTIR reflection and X-ray photoelectron spectroscopies. The persistence in the protective ability of the polymer film against iron corrosion in 0.5 M NaCl may be associated with the strong adsorption via the covalent bond, revealed by electron-probe microanalysis.     

Additional modification to two-dimensional polymer films of a hydroxymethylbenzene self-assembled monolayer with alkyltriethoxysilanes for enhancing the protective abilities against iron corrosion

Additional modification of the ultrathin two-dimensional polymer film, a p-hydroxymethylbenzene C₆H₄CH₂OH self-assembled monolayer modified with 1,2-bis(triethoxysilyl)ethane (C₂H₅O)₃Si(CH₂)₂Si(OC₂H₅)₃ (BTESE) and alkyltriethoxysilane C_nH_2n+1Si(OC₂H₅)₃ (C_nTES, n = 8 or 18), was attempted to improve the protective ability of the film against iron corrosion. The ability of the film was examined by polarization measurement of an iron electrode coated with the film in an oxygenated 0.5 M NaCl solution after immersion in the solution for 1.5 to 72 h. Marked improvement of the protective efficiency, P was not obtained by additional modification to the polymer film with BTESE. The P values of the two-dimensional polymer films were markedly increased by additional modification with C₈TES. The increases in P were ascribable to improvement of alkyl tail arrangement and additional interconnection in the polymer films. The film on the iron surface was characterized by contact angle measurement, FTIR reflection spectroscopy and X-ray photoelectron spectroscopy. The protective abilities of the two-dimensional polymer films additionally modified with C₈TES were persistent during immersion for 72 h.     

Polymerization of substituted aniline and characterization of the polymers obtained

Chemical polymerization of m-toluidine, o-chloroaniline and nitroaniline has been studied, and characterization of the resulting polymers performed by DSC, X-ray, i.r., XPS and conductivity measurements. It is found that the substituted group of aniline affects not only the polymerization reaction, but also the properties of the polymers obtained. The polymerization conditions, such as the pH value of the polymerization solution, have a certain influence on the polymer yield and its conductivity. The solubility of polymers of substituted aniline (SPA_n) is similar to that of polyaniline. The results on X-ray diffraction of SPA_n reveal that the substituted group has some effect on the regularity of the polymers. DSC measurements show the existence of an endothermic peak as a disordering of the regular segments. The spin concentration of SPA_n increases with increasing conductivity of the polymers to a certain degree. On the basis of the XPS and doping reaction of SPA_n, a possible structure of the conducting polymer is proposed.     

Study of chemically (AsF5) and electrochemically doped aluminium polyfluorophthalocyanine, (PcAlF)n

Chemical AsF₅ and electrochemical AsF₆^? doping of aluminium polyfluorophthalocyanine, (AlPcF)_n, has been studied. Thermogravimetric analysis, infrared spectroscopy, X-ray diffraction and electrical conductivity measurements were used to characterize the doped materials. Particular attention has been devoted to the study of the most heavily doped samples obtained in the first case (between 4 and 5 AsF₅ molecules per phthalocyanine ring). A qualitative structural model is proposed to explain the low electrical conductivity of these samples. Results are compared with those for iodine-doped (AlPcF)_n and (GaPcF)_n.Cyclic voltammetry performed on polymer films revealed the existence of two oxidation peaks. While it is very likely that the second peak is accompanied by a chemical reaction taking place at the polymer electrode, it is possible to obtain a lightly AsF₆^?-doped sample for applied potentials lower than 0.6 V (versus Ag/Ag⁺). Very similar results are obtained with BF₄^? and ClO₄^? doping anions.     

Synthesis of π-conjugated polymers possessing 1,3-butadiene-1,4-diyl units by reactions of regioregular organometallic polymer having titanacyclopentadiene moieties in the main chain

The synthesis and properties of π-conjugated polymers possessing phenylene-1,4-diyl and 1,3-butadiene-1,4-diyl alternating units in the main chain by reactions of a regioregular organometallic polymer having titanacyclopentadiene-2,5-diyl unit are described. The polymerization of 1,4-diethynyl-2,5-dioctyloxybenzene with a low-valent titanium complex, generated in situ from titanium(IV) isopropoxide and isopropyl magnesium chloride, was carried out at ?78 °C to ?50 °C for 12 h to give the regioregular organotitanium polymer. The diene-containing π-conjugated polymers were obtained by the reactions of the organotitanium polymer with electrophiles such as hydrochloric acid and iodine. For example, the reaction with hydrochloric acid gave a diene-containing polymer in a 61% yield whose M_n and M_w/M_n were estimated as 5700 and 1.61, respectively (by GPC). The π-conjugated character of the resulting polymer could be supported by its UV–vis spectrum. That is, the absorption maximum (λ_max) of the polymer was observable at 470 nm, which was bathochromically shifted by 115 nm compared to that of a model compound (1,4-bis(2-methoxyphenyl)-1,3-butadiene, λ_max = 355 nm).     

Poly[(1,4-phenylenevinylene)-alt-(1,3-phenylenevinylene)]s with different length of side chain: their synthesis and optical properties

Poly[(2,5-dialkoxy-1,4-phenylenevinylene)-alt-(1,3-phenylenevinylene)]s (PpPVmPVs) with various length of alkyl side chains have been synthesized by using Wittig reaction. Polymer structure and olefin bond geometry (cis- and trans-CHCH) are characterized by spectroscopic methods. Soluble PpPVmPV 6 with high content of trans-CHCH requires side chain as short as n-propyl, partially attributed to the presence of m-phenylene linkage along the polymer backbone. PpPVmPV 3 with predominant cis-CHCH linkage further improves the polymer solubility, indicating a large impact of olefin bond geometry to the polymer solubility. Fluorescence quantum efficiency measurement shows that the alkyl chain length has little influence on the luminescence of PpPVmPV.     

Attempts to synthesize a mixed oxygen-bridged metal (phthalocyaninato)(tetrabenzoporphyrinato) polymer

The synthesis of the mixed polymer [TBPcGeO]_n containing phthalocyaninatogermanium (PcGe) and tetrabenzoporphyrinatogermanium (TBPGe) subunits linked by oxygen bridges, is reported. Iodine doping leadi to [TBPcGeOI_1.1]_n at the maximum doping level, which shows a room temperature d.c. conductivity σ_RT = 8 × 10⁻² S/cm.     

Electrochemical properties of luminescent polymers and polymer light-emitting electrochemical cells

The electrochemical p-doping potentials (φ_p) and n-doping potentials (φ_n) of 10 soluble poly(1,4-phenylene vinylene) (PPV) derivatives and of the conjugated polymer blend in a light-emitting electrochemical cell (LEC) were measured by cyclic voltammetry. The energy levels corresponding to the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) of the polymers were determined from the onset potentials for n-doping (φ_n′) and p-doping (φ_p′), respectively. The electrochemical energy gap, E_g′=Δφ=φ_p′−φ_n′, agrees well with the optical energy gap (E_g). For copolymers of poly(2-methoxy, 5-(2′-ethyl-hexyloxy) paraphenylene vinylene) (MEH-PPV) and poly(2-butyl, 5-(2′-ethyl-hexyl) paraphenylene vinylene) (BuEH-PPV), the n-doping potentials are nearly independent of the ratio of MEH-PPV to BuEH-PPV. However, p-doping potentials depend strongly on the ratio, the higher the MEH-PPV fraction, the lower the p-doping potential of the copolymer. For cyano-PPV (CN-PPV), both p-doping and n-doping potentials were shifted by ca. 0.6 V (more electronegative) as a result of the electron withdrawing effect of cyano side group. The electrochemical p-doping and n-doping processes of the MEH-PPV polymer blend in the LEC device were confirmed from linear sweep voltammetry of the LEC; the doping onset potentials were the same as for an MEH-PPV film measured in a liquid electrolyte.     

The influence of molecular weight on the Resonant Raman Scattering of polyacetylene

For the first time, polyacetylene, (CH)_x, films of known number average molecular weights, M_n, have been examined using Resonance Raman Scattering techniques. (CH)_x samples of 500, 5300, 10500, and 100,000 Daltons were synthesized using the classical titanium tetra-n-butoxide/triethyl aluminum catalyst/cocatalyst system. After thermal isomerization, modeling of the RRS spectra using the Brivio, Mulazzi model indicate that the 100,000 Dalton polymer is composed principally of long trans conjugated segments. In contrast, polymers of 10500 M_n and below are seen to contain significantly larger fractions of short trans conjugated segments. For samples below 10500, no clear relationship between actual polymer molecular weight and G, the ratio of long to short segments, is observed. These results suggest that not until very long chains are obtained can samples containing a large fraction of long conjugated segments be obtained. Ambient, short term oxidation of 100,000 M_n polymer shows an increase in satellite band intensities at ω_c−c and ω_c=c, where ω is frequency, which corresponds to a decrease in G. Low level chain oxidation or doping is shown to preferentially occur within long conjugated segments.     

Protection of iron against corrosion by coverage with ultrathin two-dimensional polymer films of a hydroxymethylbenzene self-assembled monolayer anchored by the formation of a covalent bond

Ultrathin films of two-dimensional polymers were prepared on an iron electrode by modification of a p-hydroxymethylbenzene p-HOCH₂C₆H₄ (HOMB) self-assembled monolayer (SAM) with 1,2-bis(triethoxysilyl)ethane (C₂H₅O)₃Si(CH₂)₂Si(OC₂H₅)₃ (BTESE) and alkyltriethoxysilanes C_nH_2n+1Si(OC₂H₅)₃ (C_nTES, n = 8 and 18). The electrode was derivatized by cathodic reduction of p-hydroxymethylbenzenediazonium tetrafluoroborate HOCH₂C₆H₄N₂BF₄ in an electrolytic acetonitrile solution below 10 °C for 1 h to form the SAM via a covalent bond between carbon and iron atoms. The protective ability of the polymer film against iron corrosion was determined by polarization measurement of the coated electrode in an oxygenated 0.5 M NaCl solution. The protective efficiencies of the polymer films prepared by modification with BTESE plus C₈TES and C₁₈TES were 63.9% and 68.5% after immersion in 0.5 M NaCl for 1.5 h, respectively. These values were higher than those of the one-dimensional polymer films prepared with the respective C_nTES. The film of the HOMB SAM modified with BTESE plus C₈TES was characterized by contact angle measurement using a drop of water and X-ray photoelectron and FTIR reflection spectroscopies. The films of the HOMB SAM modified with BTESE plus C₈TES and C₁₈TES were persistent during immersion of the coated electrodes in 0.5 M NaCl for many hours by far as compared with the alkanethiol SAM anchored on iron by the formation of a coordinate bond.     

Synthesis,structure and luminescent properties of neodymium(III) coordination polymers with 2,3-pyrazinedicarboxylic acid

The coordination polymer [Nd₂(pzdc)₃(H₂O)]_n·nH₂O (complex I) with three-dimensional framework has been prepared by hydrothermal synthesis of 2,3-pyrazinedicarboxylic acid (pzdc) and neodymium nitrate and characterized by elemental analyses, IR spectroscopy, thermal analyses and single crystal X-ray diffraction. The complex crystallizes in monoclinic system, space group P2(1)/c. Every Nd(III) atom in the coordination polymer is nine-coordinated with different coordination environments. The pzdc ligands coordinate to the central Nd(III) atoms in bridging tetradentate, hexadentate, or heptadentate modes. The thermal decomposition of the complex has been predicted with the help of thermal analyses (TG, DTG and DTA). Complex I exhibits luminescent emissions bands in the solid state at room temperature. The isomorphous complex [Nd₄(pzdc)₆(H₂O)₂]_n·3nH₂O (complex II) has also been prepared by hydrothermal reaction under different conditions. Luminescent emission of complex I display selectivity for some heavy metal ions.     

Synthesis,polymerization and wool coating studies of 3-iso-butylpyrrole and 3-iso-pentylpyrrole

In a four-step method starting from pyrrole, the synthesis of 3-iso-butylpyrrole and 3-iso-pentylpyrrole, was achieved in 45 and 44% yields, respectively. Polymerization studies of these branched alkyl pyrroles are described and the results compared with those obtained for the unbranched structural isomers n-butyl and n-pentylpyrrole. A series of conductive textiles were produced by the chemical polymerization of the iso-alkylpyrroles using both solution and vapour polymerization techniques. Fabrics coated with poly-iso-alkylpyrrole formed using the solution polymerization method had a lower surface resistance than those formed using the vapour polymerization method. These conductivity results were in direct contrast to those previously obtained for 3-n-alkylpyrroles on fabrics. A remarkable crystal-like growth on the surface of the textile fabric was observed when solution polymerization of 3-iso-pentylpyrrole was employed—reinforcing the notion that subtle changes in monomer structure can drastically affect bulk polymer properties.     

Recombination kinetics of polarons in films of alkylator-sensing co-polymers

We report on the effect of an alkylating agent sensing of a nucleophilic unit, Pyridine-Thiophene (PyTh), on the polaron recombination in a co-polymer [Poly(3-hexylthiophene)]_n(PyTh)_m (m≈0.025n$m\approx 0.025n$). We show that by exposing the co-polymer to an alkylating agent, such as methyl iodide, the recombination rate increases substantially, possibly due to the introduction of additional recombination pathways created by the charge transfer between the electron deficient alkylated pyridinium sites and the electron rich thiophene polymer backbone.     

Inverse gas chromatography for identification of poly(ethylene glycol adipate) and tripropionitrilamine on the surface of polymeric sorbent

Identification of the adsorption of poly(ethylene glycol adipate) (PEGA) and tripropionitrilamine (TPA) on styrene-divinylbenzene porous polymer was performed with the use of the inverse gas-chromatography method in finite concentration. PEGA and TPA were applied in quantities ω = 10^?6?10^?3 mass fractions. As test sorbates n-propanol, n-butanol, and n-hexane used. The adsorption isotherm and the values of specific retention volumes were calculated via the Glueckauf method. It was found that the dependence of the retention volumes on the sorbate concentration in gas phase of the studied samples is well approximated by a power function corresponding to the Freundlich isotherm. The possibility of detecting PEGA and TPA on the surface of sorbent through the A coefficients of a power function was shown, and a linear dependence between the A values and negative logarithm of ω was also found, making it possible to quantitatively determine TPA and PEGA on the surface of a sorbent.     

Uniform dispersion of triplet emitters in multi-layer solution-processed organic light-emitting diodes

The influence of the iridium complex solubility on the efficiency of multi-layer solution-processed organic light-emitting diode is demonstrated by synthesized orange triplet iridium complexes with the same core. The solubility of the iridium(III) bis(4-phenylthieno[3,2-c]pyridinato-N,C²′) acetylacetonate is increased and uniform dispersion of iridium complex in polymer host poly(vinylcarbazole) is achieved by tert-butyl and n-hexyl group modification. Blade coating technique is utilized to achieve tri-layer structures with a polymer hole-transporting layer poly[(9,9-dioctylfluorenyl-2,7-diyl)-co-(4,4′-(N-(4-s-butylphenyl))diphenylamine)], a host–guest emissive layer, and small-molecule hole-blocking layer 1,3,5-tris(N-phenylbenzimidazol-2-yl) benzene. The efficiency as high as 20 cd/A is achieved for orange-emitting device.     

Synthesis and electrochemical properties of a new class of boron-containing n-type conjugated polymers

Several electron-deficient polymers containing the 9,10-diboroanthracene unit have been synthesized and characterized. Electrochemical study shows that they have high electron affinities. Photoluminescence of rr-P3HT is quenched in the presence of one of the polymers in the solid state, demonstrating the potential utility of this class of polymer as powerful n-type materials in organic photovoltaic devices.     

The formation of oligomers in the electrolyte upon polymerization of pyrrole

Pyrrole was polymerized by electrochemical and chemical oxidation of a solution of pyrrole and p-toluene sulfonic acid in acetonitrile. We have investigated the components formed within that electrolyte solution during the polymerization. Both, UV–VIS spectroscopy and size exclusion chromatography give evidence that pyrrole oligomers nP (n≤30) are formed in the solutions during the polymerization process. A model is proposed in which these oligomers act as intermediates of the polymerization reaction. Within that model the deviations from Faradayic behaviour at elevated current densities are explained. It also rationalizes the fact that polymer films with completely different properties can be realized by varying the experimental parameters.     

Synthesis,crystal structure and anticancer activity of 2D-coordination polymer of cerium(III) with chiral Schiff base trans-N,N′-bis-(2-hydroxy-1-naphthalidehydene)-(1R,2R)-cyclohexanediamine

The chiral Schiff base coordination polymer [Ce(H₂L)₃(NO₃)₃Ce(H₂L)₃(NO₃)₃(H₂O)]_n [H₂L: trans-N,N′-bis-(2-hydroxy-1-naphthalidehy-dene)-(1R,2R)-cyclohexanediamine] was synthesized and characterized by infrared spectroscopy, elemental analysis and single-crystal X-ray diffraction analysis. X-ray crystallography shows that the Ce(III) coordinates with three neutral Schiff base ligands and three nitrates. One Ce(III) is nine-coordinated by three oxygen atoms from three different Schiff base ligands and six oxygen atoms from three nitrates, the other Ce(III) is ten-coordinated because of the coordination of an additional water molecule. Each Schiff base ligand serves as a bridging ligand to link Ce(III) ions through oxygen atoms, leading to a coordination polymer. The Ce(III) coordination polymer displays two dimensional plane grid network structure. The antiproliferation activities of the ligand H₂L and its Ce(III) coordination polymer on MDA-MB-231 breast cancer cells were also studied by MTT (3-[4,5-dimethyltiazol-2-yl]-2,5-diphenyl-tetrazolium bromide) method. The results indicate that H₂L and [Ce(H₂L)₃(NO₃)₃Ce(H₂L)₃(NO₃)₃(H₂O)]_n can inhibit the cellularproliferation. Moreover, the coordination polymer had higher antiproliferative activity than that of the ligand.     

Mode characterization of microring polymer lasers

Conducting polymer films coated on circular glass fibers offer a low loss, high Q, resonance structure for investigating photopumped lasers. The high Q structure allows a simplification of the boundary conditions, that the field goes to zero at the boundary. Solutions of the wave equation are then simply integer Bessel function of high order. The product nρ, where n is the refraction index and ρ is the microring radius, is needed to several decimal places to successfully assign spectral emission lines to the appropriate Bessel function. A Fourier transform of the emission spectra consists of a series of diminishing peaks with a spacing of nρ. With this evaluated product in hand a calculation of the laser emission can be obtained.     

Synthesis,characterization, conductivity,band gap and thermal analysis of poly-2-[(4-mercaptophenyl) imino methyl] phenol and some of its polymer–metal complexes

The oxidative polycondensation reaction conditions of 2-[(4-mercaptophenyl) imino methyl] phenol (4-MPIMP) was studied in an aqueous alkaline medium between 30 and 90 °C by using oxidants such as air O₂, NaOCl and H₂O₂. Polymer–metal complex compounds were synthesized from the reactions of poly-2-[(4-mercaptophenyl) imino methyl] phenol (P-4-MPIMP) with Cr³⁺, Co²⁺, Ni²⁺, Cu²⁺, Mn²⁺, Zn²⁺, Pb²⁺, Cd²⁺ and Zr⁴⁺ ions. The structures of these monomer and polymer were identified from UV–vis, FT-IR, ¹H NMR, ¹³C NMR and elemental analysis. While thermal analysis of P-4-MPIMP and polymer–metal complexes were made by TGA–DTA, the number-average molecular weight (M_n), weight-average molecular weight (M_w) and polydispersity index (PDI) values of this polymer were determined by size exclusion chromatography (SEC). According to TG–DTA analyses, P-4-MPIMP–Cu was found to be higher stable than other synthesized polymer and polymer–metal complexes. While conductivity measurements of polymer and polymer–metal complexes were done by electrometer using four point probe techniques, electrochemical and optical band gap values of 4-MPIMP, P-4-MPIMP and polymer–metal complexes were determined by using cyclic voltammetry and UV–vis measurements. Conductivity and band gap values show that this polymer and polymer–metal complexes are a typical semiconductor.