Two‐Step direct arylation for synthesis of naphthalenediimide‐based conjugated polymer

A naphthalenediimide (NDI)‐based conjugated polymer was synthesized by a two‐step direct C‐H arylation sequence. In the first step, two ethylenedioxythiophene units were coupled to NDI by direct arylation. In the second step, the direct arylation polycondensation of the monomer, formed in the first step, with 2,7‐dibromo‐9,9‐dioctylfluorene afforded the corresponding NDI‐based conjugated polymer ( PEDOTNDIF ) with molecular weight of 21,500 in 91% yield. The optical and electrochemical properties of the polymer were evaluated. The polymer showed ambipolar behavior in organic field‐effect transistors (OFETs). The electron mobility of PEDOTNDIF was estimated to be 2.3 × 10^?6 cm² V^?1 s^?1 using an OFET device with source‐drain (S‐D) Au electrodes. A modified OFET device with S‐D MgAg electrodes increased the electron mobility for PEDOTNDIF to 1.0 × 10^?5 cm² V^?1 s^?1 due to the more suitable work function of these electrodes, which reduced the injection barrier to the semiconducting polymer. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 1401–1407     

High molecular weight poly(ethylene‐2,5‐furanoate); critical aspects in synthesis and mechanical property determination

Furan‐2,5‐dicarboxylic acid (FDCA) is a widely advocated renewable substitute for terephthalic acid (TA). Preparation of high molecular weight FDCA based polyesters by an industrially common combination of melt polymerization and subsequent solid state post condensation is described. Ultimately, poly(ethylene 2,5‐furanoate) (PEF) with absolute M_n = 83,000 g mol^?1 is obtained, determined by triple detection Size Exclusion Chromatography. The bulk polymer properties of FDCA based polyesters, necessary to evaluate their industrial potential were determined the Young's modulus of PEF is determined to be 2450 ± 220 MPa and the maximum stress 35 ± 8 MPa. The influence of crystallinity on the mechanical properties as function of temperature was determined by dynamic mechanical thermal analysis. A detailed differential scanning calorimetry study on the crystallization behavior of high molecular weight PEF allowed to calculate the equilibrium melting temperature (T_m⁰) of 239.3 and 239.7 °C for the first and second melting peak, respectively. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013 , 51, 4191–4199     

Characterization of two‐ and three‐photon absorption of polyfluorene derivatives

Fluorene‐based polymer derivatives are promising materials for organic electronic devices because of their photoluminescence and electroluminescence, good film‐forming ability, and favorable chemical and thermal properties. Although optical properties of polyfluorene have already been reported, most of the studies focused on the linear optical properties, whereas nonlinear optical characteristics have only recently received more detailed attention. Here, we report on two polyfluorene derivatives, poly(9,9′‐n‐dihexyl‐2,7‐fluorenediyl) (LaPPS 10) and poly(9,9′‐n‐dihexyl‐2,7‐fluorene‐diyl‐vinylene) (LaPPS 38), which present intense nonlinear absorption and fluorescence. Two‐photon absorption cross‐section properties of both polymers were characterized in the spectral range from 500 nm up to 900 nm, reaching peak values around 2000 Göppert Mayer units. Optical limiting behavior and two‐photon‐induced fluorescence of both polymers have also been investigated. Furthermore, the first molecular hyperpolarizability of the polymers was also studied using hyper‐Rayleigh scattering. In addition, the three‐photon absorption (3PA) spectra of both materials were also investigated, and 3PA cross‐section values in the order of 1 × 10^?78 cm⁶ s² photon^?2 were observed. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2014 , 52, 747–754     

Electrical conductivity,photoconductivity, and optical properties of poly(1,4‐diaminoanthraquinone) organic semiconductor for optoelectronic applications

The electrical conductivity and optical properties of the poly(1,4‐diaminoanthraquinone) [poly(1,4‐DAAQ)] have been investigated. The electrical conductivity of the polymer increases with temperature and room temperature conductivity was found to be 2.68 10^?5 S cm^?1. The optical band gap of the polymer is 1.87 eV due to the direct optical transitions. The photoconductivity of the polymer is higher than that of dark conductivity. When the light is switched on, the resistance decreases abruptly and when it is switched off, the resistance increases. This confirms that the polymer is a photoconductive material. The obtained results indicate that the poly(1,4‐DAAQ) is a photoconducting organic semiconductor with photovoltaic and dark current properties. Copyright © 2008 John Wiley & Sons, Ltd.     

Thermoelectrical and optical properties of double wall carbon nanotubes:polyaniline containing boron n‐type organic semiconductors

The electrical conductivity, thermoelectrical, and optical properties of the polyaniline containing boron/double wall carbon nanotubes (CNTs) composites have been investigated. The electrical conductivities of the composites prepared with 1%, 5%, and 8% CNT concentrations at 300 K were found to be 5.31 × 10^?6, 2.72 × 10^?4, and 1.12 × 10^?3 (S/cm), respectively. The thermoelectrical results indicate that all the samples exhibit n‐type electrical conductivity. The optical band gaps of the samples were found to be 3.71 eV for 0% DWNT, 3.32 eV for 1% DWNT, 3.15 eV for 5% DWNT, and 3.12 eV for 8% DWNT. The obtained results suggest that the electrical conductivity of PANI‐B polymer is improved by DWNT doping. Copyright © 2008 John Wiley & Sons, Ltd.     

Effects of substituted side‐chain position on donor–acceptor conjugated copolymers

The optical properties and electrical properties of a series of low‐band‐gap conjugated copolymers, in which alkyl side chains were substituted at various positions, were investigated using donor–acceptor conjugated copolymers consisting of a cyclopentadithiophene derivative and dithienyl‐benzothiadiazole. With substituted side chains, the intrinsic properties of the copolymers were significantly altered by perturbations of the intramolecular charge transfer. The absorption of poly[2, 6‐(4,4‐bis(2‐octyl)‐4H‐cyclopenta‐[2,1‐b:3,4‐b′]dithiophene)‐alt‐4, 7‐bis(4‐octyl‐thiophene‐2‐yl)benzo‐2,1,3‐thiadiazole] [ PCPDT‐ttOTBTOT ( P2 )], which assumed a tail–tail configuration, tended to blue shift relative to the absorption of poly[2,6‐(4,4‐bis(2‐octyl)‐4H‐cyclopenta‐[2,1‐b:3,4‐b′]dithiophene)‐alt‐4,7‐bis (thiophene‐2‐yl)benzo‐2,1,3‐thiadiazole] [ PCPDT‐TBTT ( P1 )]. The absorption of poly[2,6‐(4,4‐bis(2‐octyl)‐4H‐cyclopenta‐[2,1‐b:3, 4‐b′]dithiophene)‐alt‐4,7‐bis(3‐octyl‐thiophene‐2‐yl)benzo‐2,1,3‐thiadiazole] [ PCPDT‐hhOTBTOT ( P3 )], which assumed a head–head configuration, was blue shifted relative to that of P2 . The electrical transport properties of field‐effect transistors were sensitive to the side chain position. The field‐effect mobility in P2 (μ₂ = 1.8 × 10^?3 cm²/V s) was slightly lower than that in P1 (μ₁ = 4.9 × 10^?3 cm²/V s). However, the mobility of P3 was very low (μ₃ = 3.8 × 10^?6 cm²/V s). Photoexcitation spectroscopy showed that the charge generation efficiency (shown in transient absorption spectra) and polaron pair mobility in P1 and P2 were higher than in P3 , yielding P1 and P2 device performances that were better than the performance of devices based on P3 . © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

Dithienoindophenines: p‐Type Semiconductors Designed by Quinoid Stabilization for Solar‐Cell Applications

Compared with the dominant aromatic conjugated materials, photovoltaic applications of their quinoidal counterparts featuring rigid and planar molecular structures have long been unexplored despite their narrow optical bandgaps, large absorption coefficients, and excellent charge‐transport properties. The design and synthesis of dithienoindophenine derivatives (DTIPs) by stabilizing the quinoidal resonance of the parent indophenine framework is reported here. Compared with the ambipolar indophenine derivatives, DTIPs with the fixed molecular configuration are found to be p‐type semiconductors exhibiting excellent unipolar hole mobilities up to 0.22 cm² V^?1 s^?1, which is one order of magnitude higher than that of the parent IP‐O and is even comparable to that of QQT(CN)4‐based single‐crystal field‐effect transistors (FET). DTIPs exhibit better photovoltaic performance than their aromatic bithieno[3,4‐b]thiophene (BTT) counterparts with an optimal power‐conversion efficiency (PCE) of 4.07 %.     

Electrical transport properties of an organic semiconductor on polyaniline doped by boric acid

The electrical conductivity, thermoelectric power, and dielectric properties of polyaniline doped by boric acid (PANI‐B) have been investigated. The room temperature electrical conductivity of PANI‐B was found to be 1.02 × 10^?4 S cm^?1. The thermoelectric power factor for the polymer was found to be 0.64 µW m^?1 K^?2. The optical band gap of the PANI‐B was determined by optical absorption method, and the PANI‐B has a direct optical band gap of 3.71 eV. The alternating charge transport mechanism of the polymer is based on the correlated barrier hopping (CBH) model. The imaginary part of the dielectric modulus for the PANI‐B suggests a temperature dependent dielectric relaxation mechanism. Electrical conductivity and thermoelectric power results indicate that the PANI‐B is an organic semiconductor with thermally activated conduction mechanism. Copyright © 2008 John Wiley & Sons, Ltd.     

Study of Linear and Nonlinear Optical Properties of Four Derivatives of Substituted Aryl Hydrazones of 1,8‐Naphthalimide

Four 1,8‐naphthalimide hydrazone molecules with different electron‐donating groups have been applied in the study of linear and nonlinear optical (NLO) properties. These compounds showed strong green emission in solution. Their NLO properties such as two‐photon absorption (TPA) behavior with femtosecond laser pulses ca. 800 nm and excited‐state absorption (ESA) behavior with nanosecond laser pulses at 532 nm were investigated. Compound 4 presented the largest two‐photon cross section (550 GM) among them due to two factors: the conjugated length of compound 4 is the longest and the electron‐donating ability of compound 4 is the strongest. Different from TPA behavior, compound 2 showed the best nonlinear absorption properties at 532 nm and its nonlinear absorption coefficient and third‐order nonlinear optical susceptibilities χ ⁽³⁾ were up to 1.41×10^?10 MKS and 4.65×10^?12 esu, respectively. Through the modification of the structure, the nonlinear optical properties of these compounds at different wavelengths (532 and 800 nm) were well tuned. The great broad‐band nonlinear optical properties indicate hydrazones are good candidates for organic nonlinear optical absorption materials.     

A New Copper(I) Complex Based on Imidazole and Triphenylphosphine Ligands: Synthesis,Structure, Third‐Order NLO,and Fluorescence Properties

A new candidate [Cu(PPh₃)₂Him]Br ( 1 , PPh₃=triphenylphosphine, Him=1‐H‐imidazole) for nonlinear optical (NLO) materials has been synthesized and characterized crystallographically. The third‐order NLO optical properties were measured by the Z‐scan technique with an 8 ns pulsed laser at 532 nm. Compound 1 exhibits strong NLO absorptive abilities [α₂=(61±5)×10^?12] and effective self‐focusing performance [n₂=(15±3)×10^?18 m²·W^?1] in 1.01×10^?4 mol·dm^?3 DMF solution. The compound also exhibits luminescence in DMF solution at room temperature and shows narrow emission with maximum at 382 nm. The electronic structure and photoluminescent process were investigated by means of TD‐DFT calculations. The results suggest that the contribution to the frontier orbitals from the Cu? Br δ bond plays a crucial role in its linear optical properties, and the origin of luminescence is attributable to the π??→n transitions.     

High‐performance field‐effect transistors based on furan‐containing diketopyrrolopyrrole copolymer under a mild annealing temperature

Two furan‐flanked polymers poly{3,6‐difuran‐2‐yl‐2,5‐di(2‐octyldodecyl)‐pyrrolo[3,4‐c]pyrrole‐1,4‐dione‐alt‐thienylenevinylene} (PDVFs), with a highly π‐extended diketopyrrolopyrrole backbone, are developed for solution‐processed high‐performance polymer field‐effect transistors (FETs). Atomic force microscopy and grazing incidence X‐ray scattering analyses indicate that PDVF‐8 and PDVF‐10 films exhibit a similar nodular morphology with the ultrasmall lamellar distances of 16.84 and 18.98 Å, respectively. When compared with the reported polymers with the same alkyl substitutes, this is the smallest d‐spacing value observed to date. This closed lamellar crystallinity facilitates charge carrier transport. Therefore, polymer thin‐film transistors fabricated from as‐spun PDVF‐8 films exhibit a high hole mobility exceeding 1.0 cm² V^?1 s^?1 with a current on/off ratio above 10⁶. After annealing treatment at 100 °C in air, the highest hole mobility of PDVF‐8‐based FETs was significantly improved to 1.90 cm² V^?1 s^?1, which is among the highest values of the reported FET devices fabricated from polymer thin films based on this mild annealing temperature. In contrast, long alkyl‐substituted PDVF‐10 exhibited a relatively low hole mobility of 1.65 cm² V^?1 s^?1 mainly resulting from low molecular weight. This work demonstrated that PDVFs would be promising semiconductors for developing cost‐effective and large‐scale production of flexible organic electronics. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 1970–1977     

Synthesis and Properties of Semiconducting Bispyrrolothiophenes for Organic Field‐Effect Transistors

A series of new highly soluble bispyrrolothiophenes were synthesized from vinyl azides by using transition‐metal‐catalyzed C?H‐bond functionalization. In addition to modifying the substituents present on the end‐pyrrolothiophene moieties, the arene linker in between the two units was also varied. The solution‐state properties and field‐effect‐transistor (FET) electrical behavior of these bispyrrolothiophenes was compared. Our investigations identified that the optical properties and oxidation potential of our compounds were dominated by the pyrrolothiophene unit with a λ_max value of approximately 400 nm and oxidation at approximately 1 V. FET devices constructed with thin films of these bispyrrolothiophenes were also fabricated by means of thin‐film solution processing. One of these compounds, a bispyrrolothiophene linked with benzothiodiazole, exhibits a mobility of approximately 0.3 cm² V^?1 s^?1 and the I_on/I_off value is greater than 10⁶.     

Electrosynthesis and electrochromic properties of free‐standing copolymer based on oligo(oxyethylene) cross‐linked 2,2’‐bithiophene and 3,4‐ethylenedioxythiophene

Oligo(oxyethylene) chains cross‐linked 2,2’‐bithiophene (BT‐E5‐BT) has been synthesized successfully. A free‐standing copolymer film based on BT‐E5‐BT and 3,4‐ethylenedioxythiophene (P(BT‐E5‐BT‐co‐EDOT)) has been synthesized by electrochemical polymerization. The electrical conductivity of P(BT‐E5‐BT‐co‐EDOT) copolymer (16 S m^?1) has improved by four orders of magnitude compared to the homopolymer of BT‐E5‐BT (P(BT‐E5‐BT), 5 × 10^?3 S m^?1) at room temperature. Both homopolymer and copolymer films exhibit well‐defined redox and satisfied coloration efficiency. Spectroelectrochemistry studies indicate that the P(BT‐E5‐BT‐co‐EDOT) has a lower band gap in the range of 1.83–1.90 eV and shows more plentiful electrochromic colours (green, blue, purple and salmon pink) compared with the homopolymer P(BT‐E5‐BT). The Copolymer P(BT‐E5‐BT‐co‐EDOT) shows the moderate optical contrast (26% of 480 nm) and coloration efficiency (205.41 cm^?1 C^?2). The copolymer method provides a novel way to fabricate a free‐standing organic electrochromic device. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 1583–1592     

Preparation and characterization of polyaniline with high electrical conductivity

In the present paper, polyaniline (PANI) was polymerized by ammonium persulphate using a chemically oxidative process under mild tempertures ranging from ?5–20°C. Electrical conductivity of as synthesized PANI got enhanced gradually owing to the increase in molecular weight and crystallinity with decrease in synthesis temperature. Extraction with tetrahydrofuran (THF) was employed as the purification method of emeraldine base (EB) to enhance the electrical conductivity of PANI effectively attributed to the removal of the low molecular weight fractions and defective molecular chains. Methanesulfonic acid (MSA) was used to dope EB due to its strong acidity and small molecular size, and the amount of dopant versus EB was also optimized. Using a novel “synergistic doping” process with m‐cresol, electrical conductivity of PANI is further enhanced owing to more regular molecular chains which resulted in better interchain charge carriers' conduction. The emeraldine salts obtained finally have high electrical conductivity reaching up to 32.5 S cm^?1, which is much higher than that of the conventionally synthesized sample reported previously. Copyright © 2008 John Wiley & Sons, Ltd.     

Enhanced performance of photorefractive poly(N‐vinyl carbazole) composites

We present the enhanced photorefractive performance of high molecular weight poly(N‐vinyl carbazole) (PVCz)‐based composites. Higher diffraction efficiency with faster speed of grating build‐up was obtained by optimizing the composition of the PVCz composites. At relatively low applied electric field of E = 45 V μm^?1, diffraction efficiency of 26% for p‐polarized probe beam and corresponding that of 5.1% for s‐polarized probe beam were measured with faster grating build‐up speed of 48.3 s^?1 for the composite with 2,4,7‐trinitrofluorenone (TNF) as a sensitizer. Fastest speed of grating build‐up of 100 s^?1 and large optical gain up to 110 cm^?1 were measured at E = 80 V μm^?1 for the composite with fullerene derivative of PCBM as a sensitizer. These improved performances are due to a large orientational enhancement effect with faster response speed in addition to Pockels effect for the samples with appropriate glass transition temperature. © 2011 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2011     

Synthesis and electronic energy‐level regulation of imide‐fused poly(thienylene vinylene) derivatives

A series of novel poly(thienylene vinylene) derivatives (PTVs), P20‐P24 , with imide substituents were designed and synthesized by palladium‐catalyzed Stille coupling polymerization, wherein the imide substituent density was decreased gradually, which allowed us to explicitly study the effect of electron‐deficient substituent on the optical, electrochemical, and photovoltaic properties of the PTVs. All of the four polymers showed broad absorption bands with optical bandgaps between1.66 and 1.78 eV. By reducing density of electron‐deficient imide group, the LUMO energy levels of the polymers could be tuned gradually from ?3.75 to ?3.43 eV, with HOMO levels upshifted from ?5.64 to ?5.16 eV. Bulk heterojunction solar cells with the polymers as donor and PC₇₁BM as acceptor demonstrated very different excitons dissociation behavior. With decreasing the imide‐fused unit density, the open‐circuit voltage (V_OC) values in the devices decreased from 0.78 to 0.62 V, whereas the short‐circuit currents (J_SC) increased from 0 to 2.26 mA cm^?2 and then decreased to 1.01 mA cm^?2. By adjusting the electron‐withdrawing imide substituent density, power conversion efficiency of the PTVs‐based solar cells can be increased to four times, reached 0.86%. To the best of our knowledge, this is the first systematic study of the relationship between molecular energy level and photovoltaic properties of PTVs. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013 , 51, 4975–4982     

Synthesis of third‐order non‐linear optical polymers based on conjugated poly(heteroarylene methines)

A series of 10 new poly(heteroarylene methylenes) containing one pyrrole or thiophene ring alternating with a carbon atom in the main chain were synthesized and characterized. The polymers which were synthesized in the air were found to be partially dehydrogenated by the oxygen, that is, the bridge carbon atoms between pyrrole or thiophene rings were partially sp³ atoms and partially sp² atoms. However the polymers which were synthesized in the flowing nitrogen atmosphere were found to be deoxidized, that is the bridge atoms were sp³ atoms. The deoxidized polymers could be oxidatively dehydrogenated with tetrchlorobenzoquinone. These polymers are useful model systems to investigate the effect of conjugation length on the electronic and optical properties of conjugated polymers. Third‐order optical non‐linearities of the reulting polymers were studied by z‐scan techniques. The results show that the reulting polymers exhibited large third‐order optical non‐linear susceptibilities as large as 10^?8 esu. Copyright © 2004 John Wiley & Sons, Ltd.     

Novel pendent thiophene side‐chained benzodithiophene for polymer solar cells

In this article, pendent thiophene (2‐butyl‐5‐octylthiophene) side chain is used to modify the backbone of the polymers containing benzo[1,2‐b:4,5‐b′]dithiophene (BDT) and thieno[3,4‐c]pyrrole‐4,6‐dione (TPD). Compared with the dodecyloxy side‐chained polymer (P1), pendent thiophene‐based polymers (P2 and P3) show similar number‐average molecular weight (M_n), polydispersity index, thermal stability (T_d ～ 334–337 °C), and optical band gaps ( ) (～1.8 eV). Polymer (P2)‐based BDT with pendent thiophene and ethylhexyl‐modified TPD shows relatively low‐lying HOMO energy level (?5.52 eV) and nearly 1 V high open circuit voltage (V_OC). The polymer solar cell devices based on three copolymers show power conversion efficiencies from 2.01% to 4.13%. The hole mobility of these polymers tested by space charge limited current method range from 3.4 × 10^?4 to 9.2 × 10^?4 cm²V^?1s^?1. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 1558–1566     

Non‐Resonant z‐Scan Characterization of the Third‐Order Nonlinear Optical Properties of Conjugated Poly(thiophene azines)

The nonlinear optical properties of a functionalized poly(thiophene azine), namely, poly(3,4‐didodecylthiophene azine), PAZ, at the optical telecommunication wavelength of 1550 nm are investigated by means of the closed‐aperture z‐scan technique in both thin films and solutions. Values of χ⁽³⁾=(2.4±0.4)×10^?13 esu, n₂=(4.0±0.7)×10^?15 cm² W^?1, and γ=(4.5±0.7)×10^?34 esu are estimated for the third‐order (Kerr) susceptibility, the intensity‐dependent refractive index, and the molecular second hyperpolarizability of solution samples, respectively. A very small dependence on the polymer chain length is found. Markedly higher values of (4.4±1.1)×10^?11 esu, (6.6±1.0)×10^?13 cm² W^?1, and (5.0±0.8)×10^?33 esu are measured for the corresponding quantities in thick (up to 20 μm) polymer films cast on quartz plates. The enhancement of the NLO responses on going from solution to solid samples is attributed to a partially ordered structure and to the presence of interchain interactions leading to greater π‐electron delocalization in the cast polymer films. The results are compared with those previously obtained by using third‐harmonic generation (THG), taking into account that those data were measured under conditions of three‐photon resonance, whereas our z‐scan measurements are fully off‐resonance.     

Optical‐limiting and nonlinear optical polyacetylenes: Synthesis of azobenzene‐containing poly(1‐alkyne)s with different spacer and tail lengths

Poly(1‐alkyne)s containing azobenzene pendant groups with different lengths of the spacer and terminal alkyloxy group {? [HC?C(CH₂)_mOCO? C₆H₄? N?N? C₆H₄? OC_pH_2p+1]_n? , where m = 1, 2, 3, or 9 and p = 4, 7, or 12} were synthesized in satisfactory yields with the [Rh(nbd)Cl]₂–Et₃N catalyst. All the polymers were soluble in common organic solvents such as CHCl₃ and tetrahydrofuran. Their structures and properties were characterized and evaluated with IR, NMR, thermogravimetric analysis, UV, and optical‐limiting and nonlinear optical analyses. All the polymers were thermally stable and decomposed at temperatures as high as ～300 °C. The optical‐limiting and nonlinear optical properties of the polymers were sensitive to their molecular structures. Polymers having shorter spacer lengths and longer terminal groups showed better performances and larger third‐order nonlinear optical susceptibility (up to 1.34 × 10^?10 esu). © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 2346–2357, 2006