New soluble π-conjugated polymers containing 2-diisopropylamino-1,3,5-triazine unit: synthesis,characterization and optical properties

A new type of π-conjugated polymers containing 2-diisopropylamino-1,3,5-triazine were prepared via Sonogashira or Suzuki coupling reaction. The structures of the polymers were performed by FT-IR, ¹H-NMR, UV–vis spectroscopy, photoluminescence spectroscopy, gel permeation chromatography, thermal analysis and X-ray diffraction analysis. These derived polymers were soluble in common organic solvents such as tetrahydrofuran, chloroform, toluene, and showed good thermal stability. Polymers containing 1,4-diethynyl-2,5-bis(dialkoxy)benzene unit in polymer main chain emitted blue-green light in solution phase under UV light irradiation except with polymer containing 9,9-dioctylfluorene(blue light). Acidochromic behaviors of polymers were studied in CHCl₃-CF₃COOH mixtures. 9,9-Dioctylfluorene-containing polymer displayed better acidochromic property and linear relationship between absorbance and concentration with the concentration of CF₃COOH from 5.384?×?10^?4 to 26.92?×?10^?4 mol/L. Electrochemical behaviors of polymers depicted p-doping and some hole-transporting properties. XRD results showed that polymers exhibited certain crystallinity.     

Synthesis and two-photon absorption properties of 2,5-bis[4-(2-arylvinyl)phenyl]-1,3,4-oxadiazoles

Two symmetrical 2,5-bis[4-(2-arylvinyl)phenyl]-1,3,4-oxadiazoles that exhibit strong two-photon absorption and enhanced two-photon excited fluorescence were designed and synthesized based on “push-core-pull-core-push” molecules built from embedding electron-transporting 1,3,4-oxadiazole in aromatic conjugated system through Wittig–Horner reaction. Pumped by nanosecond laser at 800 nm, strong up-conversion emissions with the central wavelength at 507 nm (green) of 2,5-bis[4-(2-N,N-diphenylaminostyryl)phenyl]-1,3,4-oxadiazole and 475 nm (blue) of 2,5-bis[4-{2-(3-N-ethylcarbazolyl)vinyl}phenyl]-1,3,4-oxadiazole in the solution of CHCl₃ have been observed. Their two-photon absorption cross-sections obtained by nonlinear transmission method are 107 × 10⁻⁴⁸ cm⁴ s photon⁻¹ and 66 × 10⁻⁴⁸ cm⁴ s photon⁻¹. A very effective energy transfer from the excited terminal units to the π-conjugated bridging units of the 2,5-bis[4-(2-arylvinyl)phenyl]-1,3,4-oxadiazoles is the dominant contribution to the two-photon absorption.     

Large stokes shift chiral polymers containing (R,R)-salen-based binuclear boron complex: Synthesis,characterization, and fluorescence properties

Two novel chiral fluorescence polymers P-1 and P-2 incorporating (R,R)-salen-based binuclear boron complex in the main chain backbone were synthesized by (R,R)-salen-based boron complex (M-1) with 9,9-dibutyl-2,7-diethynyl-9H-fluorene (M-2) and 1,4-dibutoxy-2,5-diethynylbenzene (M-3) via Pd-catalyzed Sonogashira coupling reaction, respectively. The chiral polymers were characterized by ¹H NMR, UV–vis spectroscopy, photoluminescence (PL), gel permeation chromatography (GPC), TGA, DSC, cyclic voltammetry (CV), and theoretical calculation using density-functional theory (DFT) method. P-1 and P-2 show anisotropic fluorescence property with emission spectral maxima at 474 nm and 514 nm, respectively. Both two chiral polymers can exhibit high fluorescence quantum yields (up to 44% and 52%) with large Stokes shifts over 90 nm. The DFT theoretical calculation of the polymer repeating units indicates that the optical band gaps of P-1 is higher than that of P-2, which was consistent with the CV determination results.     

Synthesis and optical properties of a series of thermally stable diphenylanthrazolines

A series of diphenylanthrazolines were synthesized by Friedländer condensation of 2,5-dibenzoyl-1,4-phenylenediamine and acetyl-functionalized compounds in the presence of polyphosphoric acid as catalyst, in yields ranging from 61% to 88%. The diphenylanthrazolines are thermally robust with high decomposition temperatures (>380.0 °C) and high melt transitions (317–462 °C). All of them show the lowest energy absorption bands (λ_max^Abs: 394–433 nm) from the π–π¹ transitions by virtue of their large molar extinction coefficients (? ≈ 10⁴ M^?1 cm^?1), revealing low optical band gaps (2.59–2.80 eV). The compounds emit blue fluorescence with λ_max^Em ranging from 430 to 466 nm in dilute toluene solution.     

Well‐functioned photovoltaics based on nanofibers composed of PBDT‐TIPS‐DTNT‐DT and graphenic precursors thermally modified by polythiophene,polyaniline and polypyrrole

Reduced graphene oxide nanosheets modified by conductive polymers including polythiophene (GPTh), polyaniline (GPANI) and polypyrrole (GPPy) were prepared using the graphene oxide as both substrate and chemical oxidant. UV–visible and Raman analyses confirmed that the graphene oxide simultaneously produced the reduced graphene oxide and polymerized the conjugated polymers. The prepared nanostructures were subsequently electrospun in mixing with poly(3‐hexylthiophene) (P3HT)/phenyl‐C71‐butyric acid methyl ester (PC₇₁BM) and poly[bis(triisopropylsilylethynyl)benzodithiophene‐bis(decyltetradecylthien)naphthobisthiadiazole] (PBDT‐TIPS‐DTNT‐DT)/PC₇₁BM components and embedded in the active layers of photovoltaic devices to improve the charge mobility and efficiency. The GPTh/PBDT‐TIPS‐DTNT‐DT/PC₇₁BM devices demonstrated better photovoltaic features (J_sc = 11.72 mA cm^?2, FF = 61%, V_oc = 0.68 V, PCE = 4.86%, μ_h = 8.7 × 10^?3 cm² V^–1 s^?1 and μ_e = 1.3 × 10^?2 cm² V^–1 s^?1) than the GPPy/PBDT‐TIPS‐DTNT‐DT/PC₇₁BM (J_sc = 10.30 mA cm^?2, FF = 60%, V_oc = 0.66 V, PCE = 4.08%, μ_h = 1.4 × 10^?3 cm² V^–1 s^?1 and μ_e = 8.9 × 10^?3 cm² V^–1 s^?1) and GPANI/PBDT‐TIPS‐DTNT‐DT/PC₇₁BM (J_sc = 10.48 mA cm^?2, FF = 59%, V_oc = 0.65 V, PCE = 4.02%, μ_h = 8.6 × 10^?4 cm² V^–1 s^?1 and μ_e = 7.8 × 10^?3 cm² V^–1 s^?1) systems, assigned to the greater compatibility of PTh in the nano‐hybrids and the thiophenic conjugated polymers in the bulk of the nanofibers and active thin films. Furthermore, the PBDT‐TIPS‐DTNT‐DT polymer chains (3.35%–5.04%) acted better than the P3HT chains (2.01%–3.76%) because of more complicated conductive structures. © 2019 Society of Chemical Industry     

Synthesis and characterization of thieno[3,4-c]pyrrole-4,6-dione and pyrrolo[3,4-c]pyrrole-1,4-dione-based random polymers for photovoltaic applications

New random poly{benzo[1,2-b:4,5-b']dithiophene-thieno[3,4-c]pyrrole-4,6-dione-pyrrolo[3,4-c]pyrrole-1,4-dione} (PBDT-TPD-DPP) based on benzo[1,2-b:4,5-b']dithiophene (BDT) as donor and thieno[3,4-c]pyrrole-4,6-dione (TPD, 60–90%), pyrrolo[3,4-c]pyrrole-1,4-dione (DPP, 10–40%) as acceptors were synthesized through Stille coupling reaction. The photophysical, electrochemical and photovoltaic properties of random polymers were investigated. The random polymers with high molecular weight (M_n = 33.5–41.7 kDa) exhibited broad and strong absorption covering the spectra range from 350 nm up to 922 nm with absorption maxima at around 700 nm, the relatively deep highest occupied molecular orbital (HOMO) energy levels vary between ?5.25 and ?5.42 eV and suitable lowest unoccupied molecular orbital (LUMO) energy levels ranging from ?3.85 to ?3.91 eV. Polymer solar cells (PSC) based on these new random polymers were fabricated with device structures of ITO/PEDOT: PSS/random polymers: PC₇₁BM (1:2, w/w)/Ca/Al. The photovoltaic properties of random polymers were evaluated under AM 1.5G illumination (100 mW/cm²). Devices based on the random polymers showed open circuit voltage (V_oc) of 0.71–0.83 V, and power conversion efficiency (PCE) of 0.82–1.80%.     

Synthesis and characterization of polymers derived from selenophene

The synthesis of poly(2,5‐selenophen‐oxo‐1,4‐phenylen‐selenide‐1,4‐phenylene‐oxo) (I) and poly(2,5‐selenophen‐oxo‐1,4‐phenylen‐diselenide‐1,4‐phenylen‐oxo) (II) by reaction of 2,5‐bis(1,4‐bromo‐phenylen‐oxo‐)‐selenophene with sodium selenide or diselenide, respectively, using dimethylformamide as solvent, is described. Both monomers and polymers were characterized by elemental analysis, melting point, and FTIR spectroscopy. Polymers I and II were doped with iodine and SbF₅ and characterized by SEM and XPS. Also, the conductivity and the T_g values were determined. For both polymers the best doping agent was iodine, although polymer II always presented higher conductivity, reaching values of about 6 · 10^?9 S · cm^?1. The T_g values suggest a likely crosslinking of the chains in polymer II when doped with SbF₅. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 2019–2026, 2001     

Synthesis,crystal structure and electrocatalytic activity of discrete and polymeric copper(II) complexes with bitopic bis(pyrazol-1-yl)methane ligands

New coordination copper(II) compounds containing bitopic bis(pyrazol-1-yl)methane ligands, namely 1,1,2,2-tetrakis(pyrazol-1-yl)ethane, 1,4-bis[bis(pyrazol-1-yl)methyl]benzene and 1,4-bis[bis(3,5-dimethylpyrazol-1-yl)methyl]benzene were prepared. Reactions of ligands with Cu^2 + ions in 1:2 ratio gave discrete homodinuclear complexes, while 1:1 ligand-to-metal ratio lead to the formation of coordination polymers. Electrocatalytic activity of compounds in oxygen electroreduction reaction on the surface of modified carbon paste electrode was evaluated.     

Blue‐light‐emitting poly(arylene ethynylenes) containing alternating sequences of biphenylene or fluorenediyl and p‐phenylene moieties linked through triple bonds

Two new poly(arylene ethynylenes) were synthesized by the reaction of 1,4‐diethynyl‐2.5‐dioctylbenzene either with 4,4′‐diiodo‐3,3′‐dimethyl‐1,1′‐biphenyl or 2,7‐diiodo‐9,9‐dioctylfluorene via the Sonogashira reaction, and their photoluminescence (PL) and electroluminescence (EL) properties were studied. The new poly(arylene ethynylenes) were poly[(3,3′‐dimethyl‐1,1′‐biphenyl‐4,4′‐diyl)‐1,2‐ethynediyl‐(2,5‐dioctyl‐1,4‐phenylene)‐1,2‐ethynediyl] (PPEBE) and poly[(9,9‐dioctylfluorene‐2,7‐diyl)‐1,2‐ethynediyl‐(2,5‐dioctyl‐1,4‐phenylene)‐1,2‐ethynediyl] (PPEFE), both of which were blue‐light emitters. PPEBE not only emitted better blue light than PPEFE, but it also performed better in EL than the latter when the light‐emitting diode devices were constructed with the configuration indium–tin oxide/poly(3,4‐ethylenedioxythiophene) doped with poly(styrenesulfonic acid) (50 nm)/polymer (80 nm)/Ca:Al. The device constructed with PPEBE exhibited an external quantum efficiency of 0.29 cd/A and a maximum brightness of about 560 cd/m², with its EL spectrum showing emitting light maxima at λ = 445 and 472 nm. The device with PPEFE exhibited an efficiency of 0.10 cd/A and a maximum brightness of about 270 cd/m², with its EL spectrum showing an emitting light maximum at λ = 473 nm. Hole mobility (μ_h) and electron mobility (μ_e) of the polymers were determined by the time‐of‐flight method. Both polymers showed faster μ_h values. PPEBE revealed a μ_h of 2.0 × 10^?4 cm²/V·s at an electric field of 1.9 × 10⁵ V/cm and a μ_e of 7.0 × 10^?5 cm²/V·s at an electric field of 1.9 × 10⁵ V/cm. In contrast, the mobilities of the both carriers were slower for PPEFE, and its μ_h (8.0 × 10^?6 cm²/V·s at an electric field of 1.7 × 10⁶ V/cm) was 120 times its μ_e (6.5 × 10^?8 cm²/V·s at an electric field of 8.6 × 10⁵ V/cm). The much better balance in the carriers' mobilities appeared to be the major reason for the better device performance of PPEBE than PPEFE. Their highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) levels were also a little different from each other. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 299–306, 2006     

Poly(sulfonated phenylene)-block-poly(arylene ether sulfone) copolymer for polymer electrolyte fuel cell application

Novel poly(2-(3-sulfo)benzoyl-1,4-phenylene)-block-poly(arylene ether sulfone) copolymers (PSP-b-PAESs) were successfully synthesized by Ni(0)-catalyzed copolymerization of 2,5-dichloro-3′-sulfo-benzophenone (DCSB) and chlorobenzophenone-endcapped oligo(arylene ether sulfone). Their physical property, morphology and polymer electrolyte fuel cell (PEFC) performance were investigated compared to those of the DCSB-based random copolymers and Nafion112. PSP-b-PAES with a measured ion exchange capacity (IEC) of 1.82 meq g^?1, of which the hydrophilic/hydrophobic block lengths were evaluated as 17/8.4, showed the relatively small number of water molecules sorbed per sulfonic acid group (λ = 15) in water and the anisotropic membrane swelling with 2.4 times larger through-plane swelling than in-plane one, whereas it showed the almost isotropic proton conductivity. The PSP-b-PAES exhibited a microphase-separated structure composed of hydrophobic and hydrophilic domains, whereas the random copolymers exhibited a homogenous morphology. The PSP-b-PAES had the larger proton conductivity than the random copolymer with an IEC of 2.01 meq g^?1, especially under the low relative humidities. Even at a low humidification of 17% RH at 90 °C and 0.2 MPa, the PSP-b-PAES exhibited the high PEFC performance; namely, cell voltage of 0.69 V at load current density of 0.5 A cm^?2 and maximum output of 0.73 W cm^?2, which were much higher than those at 30% RH for the random copolymer (0.65 V and 0.51 W cm^?2) and Nafion112 (0.70 V and 0.61 W cm^?2). The PSP-b-PAES showed the fairly high durability of 750 h under PEFC operation at 90 °C in spite of the relatively low molecular weight. PSP-b-PAESs have the high potential as polymer electrolyte membrane for PEFC applications.     

Annealing temperature-dependent structural and electrical properties of (Ta2O5)1-x - (TiO2)x thin films,x ≤ 0.11

(Ta₂O₅)_1-x- (TiO₂)_x (TTO_x) thin films, with x = 0, 0.03, 0.06, 0.08, and 0.11, were deposited using magnetron direct current (DC) sputtering method onto the P/boron-silicon (1 0 0) substrates by varying areas of Tantalum and Titanium metallic targets, in oxygen environment at ambient temperature. The as-deposited thin films were annealed at temperatures ranging from 500 to 800 °C. Generally, the formation of the Ta₂O₅ structure was observed from the X-ray diffraction measurements of the annealed films. The capacitance of prepared metal– oxide– semiconductor (MOS) structures of Ag/TTO_x/p-Si was measured at 1 MHz. The dielectric constant of the deposited films was observed altering with varying composition and annealing temperature, showing the highest value 71, at 1 MHz, for the TTO_x films, x = 0.06, annealed at 700 °C. With increasing annealing temperature, from 700 to 800 °C, the leakage current density was observed, generally decreasing, from 10^?5 to 10^?8 A cm^?2, for the prepared compositions. Among the prepared compositions, films with x = 0.06, annealed at 800 °C, having the observed value of dielectric constant 48, at 1 MHz; and the leakage current density 2.7 × 10^?8 A cm^?2, at the electric field of 3.5 × 10⁵ V cm^?1, show preferred potential as a dielectric for high-density silicon memory devices.     

Donor-acceptor copolymer based on dioctylporphyrin: Synthesis and application in organic field-effect transistors

A novel alternating D–A copolymer, PPor–BT, with dioctylporphyrin (Por) as a donor unit and 5,6-bis(octyloxy)benzo-2,1,3-thiadiazole (BT) as an acceptor unit, was designed and synthesized by Pd-catalyzed Sonogashira-coupling reaction. The copolymer showed good solubility and film-forming ability. PPor–BT exhibited a broad absorption band from 350 to 950 nm with two peaks centered at 456 and 818 nm corresponding to the Soret band and Q-bands absorption of porphyrin segments, respectively. The employment of electron deficient BT unit to construct donor-acceptor structure observably broadened the absorption spectrum and enhanced the Q-band absorption of the porphyrin-based polymer. The HOMO and LUMO energy levels of the polymer are ?5.06 eV and ?3.63 eV, respectively. The solution-processed organic field-effect transistors (OFETs) were fabricated with bottom gate/top-contact geometry. The mobility of PPor–BT based OFEFs reached 4.3 × 10^?5 cm² V^?1 s^?1 with an on/off current ratio of 10⁴. This mobility is among the highest values for porphyrin-based polymers.     

Ion implantation effects on the characteristics of β-Ga2O3 epilayers grown on sapphire by MOCVD

In this study, the Si-ions implantation technique with different doses from 1 × 10¹⁴ to 1 × 10¹⁵ cm^?2 and dose energy 30, 40 and 50 keV was used to tune the electrical properties in unintentionally doped (UID) β-Ga₂O₃ epilayers grown on the sapphire substrates by metalorganic chemical vapor deposition (MOCVD). A high quality UID β-Ga₂O₃ epilayers were fabricated using the optimized growth parameters of MOCVD. The UID and Si-ions implanted β-Ga₂O₃ epilayers were examined and results were compared with the help of X-ray diffraction, scanning electron microscopy, X-ray photoelectron spectroscopy, and transmission electron microscopy. Si-ions implantation parameters were also simulated by stopping and range of ions in matter software (SRIM) and actual Si-ions concentration was measured by secondary ions mass spectroscopy. The electrical properties of the implanted β-Ga₂O₃ epilayers were measured by transmission length method and Hall measurements. The sheet resistivity for the β-Ga₂O₃epilayers with Si-ion dose of 1 × 10¹⁴, 6 × 10¹⁴ and 1 × 10¹⁵ cm^?2 were found as 2.047, 0.158 and 0.144 Ω cm, respectively measured by Hall measurements and the electron carrier concentrations for the above doses were 4.39 × 10¹⁸, 6.86 × 10¹⁸ and 7.98 × 10¹⁹ cm^?3. From the above results, the ion implantation was demonstrated to effectively reduce the resistivity with the high carrier concentrations.     

Substantial reduction of leakage currents in La/Er/Zn/Ti multielement-doped BiFeO3 multiferroic thin films

Multi-element doping is an effective method to suppress the leakage of BiFeO₃ (BFO). A systematic study on the effect of various elements (La, Er, Zn, Ti) doping on the leakage performance, mechanism and other electrical properties of BFO films was performed As the kinds of doping elements increases, the leakage current density of the BFO film gradually decreases. The leakage current density is gradually reduced from 5.78 × 10^?2 A/cm² doped with one element (La) to 1.25 × 10^?2 A/cm² doped with two elements (La, Ti), 4.13 × 10^?3 A/cm² doped with three elements (La, Ti, Zn), and 4.53 × 10^?4 A/cm² doped with four elements (La, Er, Zn, Ti). Finally, compared with pure BFO films, the leakage current density in doped BFO films is reduced by two orders of magnitude. Moreover, the conduction mechanism in doped BFO films is gradually changed from space charge limited current to ohmic conduction. This work provides an effective method to ameliorate the leakage of ferroelectric materials and lays a foundation for the practical application of BFO-based films.     

Synthesis and characterization of polyphenylene vinylenes having <Emphasis Type="Italic">m</Emphasis>-terphenyl group: comparison of their optical properties

A series of alternate block copolymers of polyphenylene vinylenes that have 1,3-dioctyloxy phenylene in the center of kinked m-terphenyl group as one of the building blocks with either one of the aromatic groups, viz., 1,4-dioctyloxy benzene, 4,6-dioctyloxy benzene and 4,4′-dioctyloxy biphenyl, was synthesized through Heck polymerization. These alternate block copolymers, viz., poly(2,5-bis(octyloxy)phenylene vinylene alt 4′,6′-bis(octyloxy)-1,1′:3′,1″-terphenylene) (P1), poly(2,4-bis(octyloxy)phenylene vinylene alt 4′,6′-bis(octyloxy)-1,1′:3′,1″-terphenylene) (P2) and poly(4,4′-bis(octyloxy-3,3′-biphenylene vinylene alt 4′,6′-bis(octyloxy)-1,1′:3′,1″-terphenylene) (P3), were characterized for their thermal and optical properties. The synthesized polymers had good solubility in organic solvents and were stable up to 350 °C. The molecular weights of the synthesized polymers were in the range 4370–10,900 Da with polydispersity range 1.52–1.65, which were measured by the gel permeation chromatography technique. The optical properties of these polymers showed absorptions in solution at around 400, 329, and 345 nm for P1, P2, and P3 polymers, respectively. The photoluminescence emission maxima of the polymers were at around 461 nm with a shoulder 439 and 424 nm for P1, P2, and P3, respectively. Photoluminescence emission of films of these polymers showed minimum redshift (20 nm) when compared with spectra of their solutions. The optical and photoluminescence emission properties of these polymers were found to vary on the backbone structure.     

Electrochemical characterization of tenoxicam using a bare carbon paste electrode under stagnant and forced convection conditions

From potentiostatic current transients and voltammetry studies, carried out under both stagnant and forced convection conditions, the tenoxicam electrochemical behavior on a bare carbon paste rotating disk electrode was assessed in an aqueous solution (pH = 0.403). It was found that tenoxicam's electrochemical oxidation is a mass transfer-controlled process where a current peak is clearly formed at around 0.74 V when the potential scan was varied in the positive direction. However, when the potential was switched to the negative direction, up to the initial potential value, no reduction peak was formed. Tenoxicam's electrochemical oxidation follows an EC mechanism where the electrodic and chemical kinetics are fast. From sample-current voltammetry both the number of electrons, n, that tenoxicam losses during its electro-oxidation and its half-wave potential, E_1/2, were determined to be 2 and 0.770 V vs. Ag/AgCl, respectively. Moreover, from differential pulse voltammetry plots it was confirmed that effectively in this case n = 2. Considering 2 electrons and both the Randles-Sevcik and Cotrell equations, the tenoxicam's diffusion coefficient, D, was determined to be (3.745 ± 0.077) × 10^?6 and (4.116 ± 0.086) × 10^?6 cm² s^?1, respectively. From linear sweep voltammetry plots recorded under forced convection conditions, it was found that Levich's equation describes adequately the limiting current recorded as a function of the electrode rotation rate, from where the D value was also found to be (4.396 ± 0.058) × 10^?6 cm² s^?1. Therefore, the average D value was (4.09 ± 0.33) × 10^?6 cm² s^?1. Furthermore, from the radius of the tenoxicam molecule, previously optimized at M052X/6-31 + G(d,p) level of theory, and using the Stokes–Einstein approach, D was also estimated to be 4.54 × 10^?6 cm² s^?1 which is similar to the experimentally estimated values, under both stagnant and forced convection hydrodynamic conditions.     

The synthesis of (N1E,N4E)-N1,N4-bis(pyridine-2-YL) ethylene benzene-1,4-diamine and investigation of its efficiency as new binuclear catalyst complex in copper-based ATRP

(N¹E,N⁴E)-N¹,N⁴-bis(pyridin-2-yl) ethylene benzene-1,4-diamine (BPEBD) was synthesized by condensation of 2-acetyl pyridine and 1,4-diaminobenzene and its efficiency as a catalyst in Cu-based atom transfer radical polymerizations (ATRP) of methyl methacrylate (MMA) and styrene (S) was investigated. Linear first-order kinetic plots were obtained. However, there were induction periods. The apparent rate constant values of ATRP of MMA with CuCl/BPEBD catalyst system in toluene were found to be between 2.10 × 10^?5 and 9.83 × 10^?5 s^?1, while they were between 6.67 × 10^?6 and 3.30 × 10^?5 s^?1 in the case of acetonitrile, indicating the presence of a low radical concentration throughout the polymerizations. Low apparent rate constant values denote a good control over ATRP in general. Apparent rate constant vs [ligand]/[catalyst] ratio plots showed a maximum at the [ligand]/[catalyst] ratio of 1. In the ATRP of MMA in toluene, M _n,GPC values increased linearly with conversion and these molecular weight values were close to M _n,th in comparison to that of in acetonitrile. In the polymerization of S, the control of molecular weights was not good, although the reactions were first-order kinetics. Cyclic voltammetry measurements confirmed that CuCl/BPEBD complex in acetonitrile gives quasi-reversible redox couples, and copper (I) centers in CuCl/BPEBD binuclear catalyst complexes are readily oxidized and it potentially suits to facile ATRP.     

Synthesis of poly(<Emphasis Type="Italic">p</Emphasis>-phenyleneethynylene)s bearing oligo-ethylene glycols and their gas permeation properties

1,4-Diiodobenzenes bearing oligo-ethylene glycols [IRC₆H₂IR, R = OCH₂CH₂OCH₃ (1a), O(CH₂CH₂O)₂CH₃ (1b), O(CH₂CH₂O)₃CH₃ (1c)] were polymerized with 1,4-diethynylbenzene in the presence of Pd/Cu catalyst to afford poly(p-phenyleneethynylene)s bearing oligo-ethylene glycols (2a–c), respectively. Polymer 2a was insoluble in any solvents, but the other polymers (2b, 2c) were soluble in CHCl₃. The weight-average molecular weights of 2b and 2c were 5.4 × 10⁴ and 9.6 × 10⁴, respectively, and they gave free-standing membranes by solution-casting method. The densities of membranes of 2b and 2c were 1.26 and 1.22 g/cm³, respectively, and their carbon dioxide permeability coefficients were 12.9 and 13.5 barrers, respectively. The CO₂/N₂ separation factor of membrane of 2b was as large as 33.7. Membrane of 3b, which contains triethylene glycols, exhibited higher CO₂ permselectivity, and the CO₂/N₂ separation factor was 50.0.     

Synthesis of conjugated polymers with broad absorption bands and photovoltaic properties as bulk heterojuction solar cells

Two new broad absorbing alternating copolymers, poly[1-(2,6-diisopropylphenyl)-2,5-bis(2-thienyl)pyrrole-alt-4,7-bis(3-octyl-2-thienyl)benzothiadiazole] (PTPTTBT-P1) and poly[1-(p-octylphenyl)-2,5-bis(2-thienyl)pyrrole-alt-4,7-bis(3-octyl-2-thienyl)benzothiadiazole] (PTPTTBT-P2), were prepared via Suzuki polycondensation with high yields. The two polymers were found to show characteristic absorption in the visible region of the solar spectrum. Interestingly the absorption of PTPTTBT-P1 was found to cover the visible region from 350 to 650 nm with the broad and flat absorption maximum from 440 to 510 nm in film and the absorption of PTPTTBT-P2 was found to cover the visible region from 350 to 950 nm with the relatively distinct absorption maxima at 425 and 522 nm and very weak absorption maximum at 832 nm in film. The electrochemical band gaps of the polymers were calculated to be 1.88 eV and 1.87 eV, respectively, while the optical band gaps of the polymers were calculated to be 1.94 eV and 1.87 eV, respectively. The photovoltaic properties of polymers were investigated with bulk heterojunction (BHJ) solar cells fabricated in ITO/PEDOT:PSS/polymer:PC₇₀BM(1:5 wt%)/TiOx/Al configurations. The maximum power conversion efficiency (PCE) of the solar cell composed of PTPTTBT-P1:PC₇₀BM as an active layer was 1.57% with current density (J_sc) of 8.17 mA/cm², open circuit voltage (V_oc) of 0.52 V and fill factor (FF) of 36%.     

Synthesis and characterization of highly fluorescent phenylene vinylene containing perfluorocyclobutyl (PFCB) aromatic ether polymers

4-(Trifluorovinyloxy)benzaldehyde was treated under Wittig conditions with 4-dihexyloxy-2,5-xylenebis(triphenylphosphoniumbromide) to form 1,4-bis(2′-(4-trifluorovinyloxyphenyl)ethenyl)-2,5-dihexyloxybenzene, a novel phenylene vinylene-bistrifluorovinyl ether monomer. Cyclopolymerization afforded an insoluble, non-luminescent material likely due to cross-addition reactions between phenylene vinylene olefin and trifluorovinyl ether (TFVE). However, 1,2-bis(4-formylphenoxy)hexafluorocyclobutane was polymerized with 1,4-dihexyloxy-2,5-xylenebis(triphenylphosphoniumbromide) and 1-methoxy-4-(2-ethylhexyloxy)-2,5-xylenebis(triphenylphosphoniumbromide) under Wittig conditions to yield two novel poly(perfluorocyclobutyl-co-phenylene vinylene) polymers. The polymers are of moderate molecular weight (8600-8700 M_n), show excellent thermal stability (T_d = 390-405 °C), and are readily soluble in common organic solvents. The materials are highly fluorescent in both solution and thin film with solution quantum yields of 68 and 71%.