Enhanced photovoltaic performance of quasi-solid-state dye-sensitized solar cells via incorporating quaternized ammonium iodide-containing conjugated polymer into PEO gel electrolytes

In this study, a series of gel electrolytes prepared from blends of alternating conjugated polymer electrolytes (CPEs)/poly(ethylene oxide) (PEO) were developed for use in quasi-solid-state dye-sensitized solar cells (DSSCs). The alternating CPEs poly[(N-(3′-((N,N-dimethyl)-N-ethylammonium)propyl)-3,6-carbazole)-alt-(9,9-dioctyl-2,7-fluorene)]diiodide, poly[(N-(3′-((N,N-dimethyl)-N-ethylammonium)propyl)-3,6-carbazole)-alt-(9,9-bis(2-(2-methoxyethoxy)ethyl)-2,7-fluorene)]diiodide (MPCFO-E), and poly[(N-(3′-((N,N-dimethyl)-N-ethylammonium)propyl)-3,6-carbazole)-alt-(siloxane substituted-2,7-fluorene)]diiodide (MPCFS-E) were synthesized through copolymerization of carbazole units (featuring quaternized ammonium iodide groups) and fluorene units featuring flexible side chains (9,9-dioctylfluorene, ethylene oxide-substituted fluorene, and siloxane-substituted fluorene, respectively). The MPCFO-E/PEO-based and MPCFS-E/PEO-based DSSCs exhibited lower electrochemical resistances, superior photovoltaic (PV) properties, and improved PV stabilities relative to those of the corresponding PEO-based DSSC. Among the studied systems, the DSSC based on the MPCFO-E (0.5 wt.%)/PEO blend electrolyte exhibited the best PV performance, with a short current density of 4.97 mA cm⁻² and a photoenergy conversion efficiency of 1.17%.     

Theoretical study on the structure and property relationship of the cationic conjugated polyelectrolytes

A theoretical study using density functional theory was performed to understand the structure/property relationship of the cationic conjugated polyelectrolytes, poly[9,9-bis-(6′-N,N,N-trimethylammonium) hexyl] fluorene-alt-4,7-(2,1,3-benzothiadiazole)] (PFBT-X, where X = Br). The torsion angle between the fluorene and benzothiadiazole units in the PFBT monomer was found to substantially affect the structural and electronic properties of the cationic PFBT monomer. The changes of geometrical parameter, HOMO and LUMO energy levels, and band gap, as well as the absorption maximum are discussed in terms of the torsion in the PFBT monomer structure. For comparison, its neutral analogue, the monomer of poly(9,9-di-n-octylfluorene-alt-benzothiadiazole) (F8BT) was also studied. The length of conjugation backbone was also examined.     

Syntheses of Conjugated Polymers for Photonics

Summary: By the Suzuki coupling reaction of 9,9-dioctyl-2,7-bis(1,3,2-dioxaborinan-2-yl)fluorene ( I ) and 3,5-di-tert-butylphenyl 2,5-dibromobenzenesulfonate ( II ) the alternating poly{[9,9-dioctylfluoren-2,7-diyl]-alt-[2-(3,5-di-tert-butyl-phenoxysulfonyl)-1,4-phenylene]} ( III ) was synthesized. Alkaline hydrolysis of III gave a conjugated polyelectrolyte carrying sulfonic acid groups ( IV ). Monomers 2,5-dibromo-3-[2-(pyren-1-yl)vinyl]thiophene and 2,5-dibromo-3-[2-(quinolin-4-yl)vinyl)thiophene were prepared and copolymerized with I to afford poly{[9,9-dioctylfluoren-2,7-diyl]-alt-[3-(2-(pyren-1-yl)vinyl)thiophen-2,5-diyl]} ( V ) and poly{[9,9-dioctylfluoren-2,7-diyl]-alt-[3-(2-(quinolin-4-yl)-vinyl)thiophen-2,5-diyl] ( VI ), respectively. Conjugated backbone of V contains the conjugated pyrene unit in the side chain. Similarly the side chain of VI contains the conjugated quinoline structure unit which can be for instance protonated. By the Suzuki polycondensation reaction of I and of the prepared methyl 3-(2,7-dibromocarbazole-9-yl)propionate ( VII ) the new poly{[9,9-dioctylfluorene-2,7-diyl]-alt-[9-(2-methoxycarbonylethyl)carbazole-2,7-diyl]} ( VIII ) was synthesized and characterized.     

Linearly polarized white fluorescence from shish-kebab type liquid crystalline poly(P-phenylenevinvlene)s with (P-phenylene)s as kebab

Liquid crystalline(LC) polymers with a shish-kebab-type moiety on their cross-conjugated(p-phenylene)s-poly(p-phenylenevinylene) s main chains were synthesized through Gilch polymerization in order to develop a kind of polymers available for linearly polarized white-light-emitting from single chain.In this system,the 2,5-bis(4’-alkoxyphenyl)benzene as the "kebabs" connects with poly(p-phenylenevinylene)(PPV) main chain backbone using its molecular gravity center and the PPV as the "shish" or "skewer"(the "shish-kebab").The polymers possess desirable properties such as excellent solubility and liquid crystalline properties.To drop the "kebabs" of the 2,5-bis(4’-alkoxyphenyl)benzene into the orientation microgroove of aligned polyimide film,not only the "shish" of polymer main chain can be aligned by the virtue of orientation of "kebabs" but also the uniform cross-conjugated structure between the "kebabs" and "shish" can be broken. Then,the alignment of the polymer main chain showed yellow light emission and was also accompanied by orientation of the LC side chains showing blue light emission,this gave rise to a notable linearly polarized white fluorescence.     

Synthesis and Characterization of a Water‐Soluble Carboxylated Polyfluorene and Its Fluorescence Quenching by Cationic Quenchers and Proteins

We have developed a new intermediate monomer, 2,7‐[bis(4,4,5,5‐tetramethyl‐1,3,2‐dioxaborolan‐2‐yl)‐9,9‐bis(3‐(tert‐butyl propanoate))]fluorene, that allows the easy synthesis of water‐soluble carboxylated polyfluorenes. As an example, poly[9,9′‐bis(3′′‐propanoate)fluoren‐2,7‐yl] sodium salt was synthesized by the Suzuki coupling reaction, and the properties of the polymer were studied in aqueous solutions of different pH. Fluorescence quenching of the polymer by different cationic quenchers (MV²⁺, MV⁴⁺, and NO₂MV²⁺; MV=methyl viologen) was studied, and the quenching constants were found to be dependent on the charge and electron affinity of the quencher molecule and the pH of the medium. The largest quenching constant was observed to be 1.39×10⁸ M ^?1 for NO₂MV²⁺ at pH 7. The change in polymer fluorescence upon interaction with different proteins was also studied. Strong fluorescence quenching of the polymer was observed in the presence of cytochrome c, whereas weak quenching was observed in the presence of myoglobin and bovine serum albumin. Lysozyme quenched the polymer emission at low protein concentrations, and the quenching became saturated at high protein concentrations. Under similar experimental conditions, the polymer showed improved quenching efficiencies toward cationic quenchers and a more selective response to proteins relative to other carboxylated conjugated polymers.     

A new fluorescent sensor selective for Pb<Superscript>2+</Superscript> in water capable of two-photon-induced fluorescence measurement

A new fluorescent sensor (1) for Pb²⁺ containing a 1,4-dicyano-2,5-bis(styryl)benzene fluorophore and 2-(N,N′-bis(carboxylmethyl))amino-1-carboxylmethoxylbenzene as receptor has been synthesized. The sensor selectively responds to Pb²⁺ in the aqueous environment, and brings about similar and significant changes in one- and two-photon excited emission spectra: λ _max red-shift from 460 (519) to 590 nm. The selective response is pH-independent in a large physiological pH range, and two-photon action cross section (ϕδ) is 51 GM (1 GM = 1×10⁻⁵⁰ cm⁴·s·photon⁻¹·molecule⁻¹) at 740 nm. Supported by the National Natural Science Foundation of China (Grant Nos. 20705621 & 20706008), the National Basic Research Project of China (Grant No. 2009CB724706), the Ministry of Education of China, Changjiang Scholars Innovative Research Team in University (Grant No. IRT0711) and Cultivation Fund of the Key Scientific and Technical Innovation Project (Grant No. 707016)     

Cationic polyfluorene: Conformation and aggregation in a “good” solvent

The conjugated polyelectrolyte (CPE) poly{9,9′-bis[6″-(N,N,N-trimethylammonium)-hexylfluorene-alt-co-phenylene] dibromide} (PFPN⁺Br⁻) demonstrates a high solubility in methanol in comparison to other more hydrophilic or hydrophobic solvents. We have employed a combination of pulsed-field-gradient-NMR, photoluminescence (PL), and Raman spectroscopy to establish the conformation and aggregation behavior of PFPN⁺Br⁻ in methanol, with the aim to attain information on how to design CPEs with a high solubility in a preferred solvent. We find that the diffusion coefficient and PL spectrum of PFPN⁺Br⁻, as well as the Raman-active methyl rocking mode of methanol, all exhibit a strong dependence on PFPN⁺Br⁻ concentration. We rationalize our findings with a model in which PFPN⁺Br⁻ forms aggregates via π–π interactions between main-chain segments, while the ionic side chains are surrounded and electrostatically screened by the methanol solvent. Accordingly, the notably high solubility of PFPN⁺Br⁻ in methanol is rationalized by favorable interactions between the ionic side chains and the methanol molecules. We propose that an appropriate design of a high-solubility CPE should consider a matching of the mixed hydrophobic/hydrophilic character of the ionic side chain with that of the preferred solvent.     

Carbazole-modified blue light-emitting copolymers with the backbones integrated by diphenyloxadiazole,fluorene, and triphenylamine

Two new blue light-emitting polymers, poly{[2,5-bis(4-phenylene)-1,3,4-oxadiazole]-[9,9-dihexylfluorene-2,7-diyl]-[N-(4-(9H-carbazol-9-yl)phenyl)-N,N-bis(p-phenylene)aniline]} (POFPA) and poly{[2,5-bis(4-phenylene)-1,3,4-oxadiazole]-[9,9-dihexylfluorene-2,7-diyl]-[4-(3,6-(di-9H-carbazol-9-yl)-9H-carbazol-9-yl)-N,N-bis(p-phenylene)-aniline]} (POFCPA), were synthesized by Suzuki coupling reactions. By GPC analysis against a linear polystyrene standard POFPA and POFCPA were found to have M_n of 1.68 × 10⁴ and 3.70 × 10³, respectively. In contrast to POFPA, the main absorption peak of POFCPA in dilute toluene solution was blue-shifted by Δλ = 26 nm owing to its backbone of relatively shorter π-conjugation length and more carbazole units in side chain. The absolute fluorescence quantum yield (Φ_f) of POFCPA in dilute toluene solution was determined as 73%, much higher than that of POFPA (Φ_f ≈ 58.9%) measured under the same conditions. An electroluminescence device based on POFCPA displays a stable blue emission having color coordinates of (0.15, 0.20), a maximum brightness of 4762 cd/m², and a maximum current efficiency of 1.79 cd/A. By using this polymer as the host material doped with 1 wt.% 4,4′-bis[2-(4-(N,N-diphenylamino)phenyl)vinyl]biphenyl, the achieved highest brightness, maximum current efficiency and maximum power efficiency are 13,613 cd/m², 3.38 cd/A, and1.84 lm/W, respectively.     

Reaction of <Emphasis Type="Italic">N,N</Emphasis>′-bis(trimethylsilyl)dicyandiamide with bis(η<Superscript>5</Superscript>-cyclopentadienylvanadium) dichloride

1,3,5-Tris[bis(η⁵-cyclopentadienyl)chlorovanadium]melamin is prepared in high yield by the reaction of N,N′-bis(trimethylsilyl)dicyandiamide with bis(η⁵-cyclopentadienylvanadium) dichloride in tetrahydrofuran. As side products, trimethylchlorosilane and cyclopentadiene formed. Reaction of N,N′-bis(trimethylsilyl) dicyandiamide with benzoyl chloride results in the formation of tris(benzoyl)melamin.     

Structural and physicochemical characteristics of chelate nickel(II) compounds based on 1,2,3-triketone (hydrazone)imines

The crystal structures of the chelates Ni^IIL (L²⁻ are the N,N′-(o-phenylene)-bis[4-(4-methylphenyl)hydrazono-3-oxo-1,1,2,2-tetrafluorononane-5-iminate], N,N′-ethylene-bis[3-(4-methylphenyl)hydrazono-4-oxo-5,5,6,6,7,7,8,8-octafluorooctane-2-iminate], or N,N′-ethylene-bis(4-hydroxy-5,5,6,6,7,7,8,8-octafluoro-3-octene-2-iminate) anions) were studied by X-ray diffraction. Magnetic measurements and ESR spectroscopic studies revealed the appearance of paramagnetism due to a tetrahedral distortion of the coordination unit and also the unusual behavior of the effective magnetic moment at low temperatures. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 1, pp. 103–109, January, 2007.     

The photophysical properties and morphology of fluorene-alt-benzene based conjugated polymer

A series of fluorene-alt-benzene based conjugated main chain polymers chemically attached with alkyl side chains of different lengths on phenylene rings were designed and synthesized by a palladium catalyzed Suzuki coupling reaction. The UV-vis absorption and fluorescence spectra, thermal stability of spectral property, phase transition behavior and morphology of the synthesized polymers were investigated. With increasing the length of the alkyl side chain, the UV and fluorescence spectra exhibit an obvious blue shift compared with those of the unsubstituted polymer. The alkyl substitution improves the thermal spectral stability of the polymers due to the steric hindrance of the alkyl side chains, thus leading to efficient separation of the main chain backbones. The phase transition behavior is closely related to the length of the alkyl side chains attached on the phenylene rings. The annealed films of the polymers display characteristic nematic liquid crystalline texture. TEM observations indicate that solvent-cast thin deposits of all the polymers show typical fibrillar morphology.     

The Structure of New Host Molecules that form Channel Inclusion Compounds

1,3-Benzenediamine,N,N′-bis(4,6-dichloro-1,3,5-triazine-2-yl) and 1,3,5-Triazine,2,2′-[2-methyl-1,3-phenylenebis(oxy)] bis(4,6-dichloro) were synthesized as host molecules. The inclusion compound of 1,3-Benzenediamine,N,N′-bis(4,6-dichloro-1,3,5-triazine-2-yl) crystallizes in the monoclinic crystal system in space group C2/c. The host molecule occupies the space group 2-fold special position and packed in the crystal lattice in such a manner as to leave channels running along the c axis of a rectangular cross-section. It crystallizes with two molecules of acetone that are hydrogen bonded to the amino nitrogen atoms. Molecules of 1,3,5-Triazine,2,2′-[2-methyl-1,3-phenylene bis(oxy)]bis(4,6-dichloro) are packed in the crystal in such a manner as to leave channels of a trapezoid cross-section that are running along the a axis. Guest molecules such as metanol, ethanol, and ethyl acetate can be used to fill the channels. The crystal structures of two inclusion compounds are described.     

Two‐photon excitation and optical limiting in polyfluorene derivatives

Fluorene‐based polymers are widely known materials due to a combination of features such as photoluminescence and electroluminescence, oxidative stability, and film‐forming ability. However, studies reporting nonlinear optical properties in this class of conjugated polymer are scarce. Here, we report a new class of polyfluorene derivatives poly(9,9′‐n‐dihexyl‐2,7‐fluorenedilvinylene‐alt‐1,4‐phenylenevinylene), poly(9,9′‐n‐dihexyl‐2,7‐fluorenedilvinylene‐alt‐2,5‐thiophene), and poly[(9,9‐di‐hexylfluorenediylvinylene‐alt‐1,4‐phenylenevinylene)‐co‐((9,9′‐(3‐t‐butylpropanoate) fluorene‐1,4‐phenylene)] displaying high two‐photon absorption (2PA) in the spectral range from a 490 to 1100 nm. The 2PA cross‐section peak values for these materials are as high as 3000 Göppert Mayer (1 GM = 1 × 10^?50 cm⁴ s/photon), which is related to the high degree of conjugation along the polymer backbone. The polymers that were used in this study presented a strong two‐photon luminescence and also displayed optical limiting behavior, which, in combination with their well‐established properties, make them highly suitable for nonlinear optical devices. © 2011 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 50: 148–153, 2012     

Bipyridinophane‐containing conjugated polymers modulated with an intramolecular aromatic C?H/π interaction

Bipyridinophane–fluorene conjugated copolymers have been synthesized via Suzuki and Heck coupling reactions from 5,8‐dibromo‐2,11‐dithia[3]paracyclo[3](4,4′)‐2,2′‐bipyridinophane and suitable fluorene precursors. Poly[2,7‐(9,9‐dihexylfluorene)‐co‐alt‐5,8‐(2,11‐dithia[3]paracyclo[3](4,4′)‐2,2′‐bipyridinophane)] ( P7 ) exhibits large absorption and emission redshifts of 20 and 34 nm, respectively, with respect to its planar reference polymer Poly[2,7‐(9,9‐dihexylfluorene)‐co‐alt‐1,4‐(2,5‐dimethylbenzene)] ( P11 ), which bears the same polymer backbone as P7 . These spectral shifts originate from intramolecular aromatic C? H/π interactions, which are evidenced by ultraviolet–visible and ¹H NMR spectra as well as X‐ray single‐crystal structural analysis. However, the effect of the intramolecular aromatic C? H/π interactions on the spectral shift in poly[9,9‐dihexylfluorene‐2,7‐yleneethynylene‐co‐alt‐5,8‐(2,11‐dithia[3]paracyclo[3](4,4′)‐2,2′‐bipyridinophane)] ( P10 ) is much weaker. Most interestingly, the quenching behaviors of these two conjugated polymers are largely dependent on the polymer backbone. For example, the fluorescence of P7 is efficiently quenched by Cu²⁺, Co²⁺, Ni²⁺, Zn²⁺, Mn²⁺, and Ag⁺ ions. In contrast, only Cu²⁺, Co²⁺, and Ni²⁺ ions can partially quench the fluorescence of P10 , but much less efficiently than the fluorescence of P7 . The static Stern–Volmer quenching constants of Cu²⁺, Co²⁺, and Ni²⁺ ions toward P7 are of the order of 10⁶ M^?1, being 1300, 2500, and 37,300 times larger than those of P10 , respectively. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 4154–4164, 2006     

Synthesis and photoluminescence properties of poly(2-methoxy-5-(2’-ethylhexyloxy)-<Emphasis Type="Italic">p</Emphasis>-phenylene vinylene-<Emphasis Type="Italic">co</Emphasis>-styrene) copolymers

A series of conjugated and non-conjugated copolymers of poly(2-methoxy-5-(2′-ethylhexyloxy)-p-phenylene vinylene-co-styrene) were synthesized via a typical chlorine precursor route. The obtained copolymers were characterized by FTIR spectra, UV-Vis spectra, ¹H NMR and GPC. The results obtained indicated that the introduction of non-conjugated PS segments in MEH-PPV led to the interruption of conjugation structure and shortened the effective conjugated length, by which the optical properties of the conjugated polymer can be adjusted.     

Intermolecular Order of Poly-(2,5-dimethyl-para-phenylene vinylene) and Poly-(para-phenylene vinylene) – A Comparison

Summary.  Poly-(para-phenylene vinylene) (2b, PPV) and poly-(2,5-dimethyl-para-phenylene vinylene) (1b) were prepared via the formation of a double bond by thermal elimination of an octylsulfinyl side group at 200°C under vacuum. X-Ray diffraction experiments revealed a certain degree of long-range order within both polymers. However, considerable differences in the diffraction pattern were observed, the packing of the polymer chains within the bulk structure being responsible for these differences. Within the crystal structure of 2b, neighbouring PPV chains pack in a zig-zag arrangement (herringbone pattern). Analysis of the diffraction pattern of 1b on the basis of the crystal structure of a model compound (2,5,2′,5′-tetramethylstilbene) revealed that the molecular planes of neighbouring polymer chains pack parallel to each other. A model for the crystal structure of 1b is given. The change of packing from a herringbone to a parallel arrangement of the molecular planes is related to the introduction of methyl groups as side chains to PPV. Received December 14, 2000. Accepted (revised) December 20, 2000     

The behavior of <Emphasis Type="Italic">p</Emphasis>-bis{3-[N-(3-chloro-buten-2-yl)pyrrolidinio(piperidinio or morpholinio)]propyn-1-yl}benzene dichlorides in an aqueous base medium

In aqueous base medium p-bis{3-[N-(3-chlorobuten-2-yl)pyrrolidinio (piperidinio or morpholinio)]-propyn-1-yl}benzene dichlorides undergo a two-way dehydrochlorination-cyclization reaction to form benzo[5,6-a:5′,6′-c]bis(2,2-tetramethylene- or -2,2-pentamethylene-4-methylisoindolinium) and benzo-[5,6-a:5′,6′-c]bisspiro(4-methylisoindoline-2,4′-morpholinium) dichlorides. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 4, pp. 546–549, April, 2009.     

Estimation of flocculation structure in filled polymer composites by dynamic rheological measurements

 The frequency and concentration dependences of the storage modulus (G ^′) for carbon black and short-carbon-fiber-filled polymer composites were investigated by means of dynamic rheological measurements. It was found that G ^′ at low frequencies and amplitudes could be used as a sensitive experimental parameter for detecting the flocculation structure of the ultra-fine-particle-filled polymer composites. Correlation of electrical resistivity of the composites to the relative storage modulus, G ^′ _r(=G ^′ _c/ G ^′ _p), revealed that the three-dimensional interparticle networks start to construct through the matrix when G ^′ _r increases to 7 regardless of the composite systems. Quantitative calculations in order to determine the flocculation structure were carried out by means of the modified Kerner equation. A plot of the calculated value, defined as the floc index A, dependence of electrical resistivity for various systems was found to be a universal curve. Accordingly, we suggest that A might universally correspond to the flocculation structure of the filler, which is independent of the nature of the filler, the molecular weight, the chemical composition of the polymer and the temperature at which the measurement is made. This method is particularly effective for estimating the flocculation structure of ultra-fine-particle-filled polymer composites no matter whether the filler is conductive or not. Received: 26 May 1999/Accepted in revised form: 28 September 1999     

Crystal structures and luminescence of two zinc(II) complexes with benzimidazole ligands

Two new zinc(II) complexes have been synthesized and studied by single crystal X-ray diffraction method: [Zn(L1)Cl₂]·2DMF (1) and [Zn(L2)Cl₂]·DMF (2) (L1 = 3,3′-bis(2-benzimidazolyl)-2,2′-dipyridine, L2 = 3,3′-bis[2-bis(2-ethylbenzimidazolyl)]-2,2′-dipyridine). Compound 1 is monoclinic, C2/c, a = 23.142(3) ?, b = 11.845(1) ?, c = 14.735(3) ?; compound 2 is orthorhombic, C222₁, a = 12.140(7) ?, b = 16.283(9) ?, c = 16.51(1) ?. In both compounds, Zn(II) cations are coordinated by two chlorine atoms and two benzimidazole nitrogen atoms in a slightly distorted tetrahedron fashion. Structural features responsible for fluorescent properties of the complexes are discussed.     

Synthesis,characterization and catalytic properties of heterogeneous iron(III) tetradentate Schiff base complexes for the aerobic epoxidation of styrene

A series of hybrid mesoporous SBA-15 materials containing four iron(III) Schiff base complexes of the type [FeL ^x (NO₃)] (x = 4–7, L = N,N′-bis(salicylidene)ethylenediamine, N,N′-bis(salicylidene)diethylenetriamine, N,N′-bis(salicylidene)o-phenylenediamine, N,N′-bis(3-nitro-salicylidene)ethylenediamine) was synthesized by a post-grafting route. The XRD, N₂ adsorption/desorption and TEM measurements confirmed the structural integrity of the mesoporous hosts, and the spectroscopic characterization techniques (FT-IR, UV–vis spectroscopy, ¹H NMR) confirmed the ligands and the successful anchoring of iron(III) Schiff base complexes over the modified mesoporous support. Quantification of the supported ligand and metal was carried out by TG/DSC and ICP-AES techniques. The catalyst FeL⁷-SBA resulting from N,N′-bis(3-nitro-salicylidene)ethylenediamine) ligand was considerably active for the aerobic epoxidation of styrene, in which the highest conversion of styrene reached 83.6%, and the selectivity to styrene oxide was 83.0%. Moreover, it was also found that the catalytic activity increases with the decrease in the electron-donating ability of the Schiff bases, and the selectivity varies according to the types of substituents in the ligands.