Synthesis and characterization of poly(1,4‐bis((E)‐2‐(3‐dodecylthiophen‐2‐yl)vinyl)benzene) derivatives

New amorphous semiconducting copolymers, poly(9,9‐dialkylfluorene)‐alt‐(3‐dodecylthienyl‐divinylbenzene‐3‐dodecylthienyl) derivatives (PEFTVB and POFTVB), were designed, synthesized, and characterized. The structure of copolymers was confirmed by H NMR, IR, and elemental analysis. The copolymers showed very good solubility in organic solvents and high thermal stability with high T_g of 178–185 °C. The weight average molecular weight was found to be 107,900 with polydispersity of 3.14 for PEFTVB and 76,700 with that of 3.31 for POFTVB. UV–vis absorption studies showed the maximum absorption at 428 nm (in solution) and 435 nm (in film) for PEFTVB and at 430 nm (in solution) and 436 nm (in film) for POFTVB. Photoluminescence studies showed the emission at 498 nm (in solution) and 557 nm (in film) for PEFTVB and at 498 nm (in solution) and 536 nm (in film) for POFTVB. The solution‐processed thin‐film transistors showed the carrier mobility of 2 × 10^?4 cm² V^?1 s^?1 for PEFTVB‐based devices and 2 × 10^?5 cm² V^?1 s^?1 for POFTVB‐based devices. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 3942–3949, 2010     

Linear π‐conjugated polymers containing 2,4,6‐tris(thiophen‐2‐yl)‐1,3,5‐triazine unit: Synthesis and optical properties

Some linear π‐conjugated polymers containing 2,4,6‐tris(thiophen‐2‐yl)‐1,3,5‐triazine unit were synthesized via Sonogashira or Suzuki reaction for the first time and characterized by IR, NMR, and GPC. Because of the introduction of 2,4,6‐tris(thiophen‐2‐yl)‐1,3,5‐triazine unit into π‐conjugated system, all polymers exhibited good thermal stability with high decomposition temperature. Their optical and electrochemical properties were investigated. Based on the 2,4,6‐tris(thiophen‐2‐yl)‐1,3,5‐triazine unit linked with different aromatic rings, the polymers showed the tunable fluorescence from blue to blue‐green emission with satisfied quantum yield. Cyclic voltammetry measurement indicated that the LUMO and HOMO levels of the polymers could be adjustable through the main‐chain structural modification. All polymers had low LUMO level (?2.86 to ?3.06 eV) due to the high‐electron affinity of triazine unit. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 702–712, 2008     

Regioregular poly[3‐(4‐alkoxyphenyl)thiophene]s

An easy synthetic procedure for soluble poly[3‐(4‐alcoxyphenyl)thiophene]s is reported. The polymers present a high regioregularity degree as determined by both UV–vis spectra and ¹H and ¹³C NMR analysis. Furthermore, X‐ray powder diffraction analysis performed on films of the polymers suggests a π‐stacked packing structure of the macromolecules. Electrical characterization was performed on one of the synthesized polythiophenes on both undoped and doped (with FeCl₃ or iodine) films. The conductivity and charge‐carrier mobility were assessed by current–voltage and field effect measurements. Well‐structured polymer films were obtained simply via spin coating from chloroform solutions and without the need of further processing, unlike other regioregular polythiophenes reported in the literature. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 1758–1770, 2007     

Energy transfer in poly(3‐hexylthiophene)‐g‐Polyfluorene graft copolymers

Conjugated graft copolymers consisting of a poly(3‐hexylthiophene) (P3HT) backbone and poly(9,9'‐dioctylfluorene) side chains (PF) with different grafting degrees were synthesized by the CuAAC reaction. The properties of these materials were studied by UV‐Vis and fluorescence spectroscopy. The former technique provides insight in their self‐assembly, while the latter is used to study the energy funneling from the PF side chains to the P3HT backbone. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 1252–1258     

Single step synthesis of poly(3‐octylthiophene)/multi‐walled carbon nanotube composites and their characterizations

The transport properties of conducting polymers are known to be greatly influenced by the chemical unsaturation surrounding the polymer backbone, besides favorable conformation of the side chains present. Polymeric composites with multi‐walled carbon nanotubes (MWNT) can provide a good conductive path at relatively low carbon contents, as these have high aspect ratio, specific surfaces and are cost effective. Hence their use in various applications such as organic LED, solar cells and supercapacitors are very much anticipated. In this respect poly(3‐octylthiophene)/MWNT composites have been prepared by an “insitu” polymerization process in chloroform medium with FeCl₃ oxidant at room temperature. The composites were characterized by Fourier Transfer Infrared spectroscopy (FT‐IR), Raman, work function and X‐ray diffraction (XRD) measurements. The results indicate only a weak π‐π interaction between the moieties, in the absence of a strong covalent bonding. The ultraviolet–visible (UV–Vis) measurements also support this view. The photoluminescence (PL) quenching indicates the effectiveness of the interface in the formation of the donor–acceptor type composite. The conductivity of the composites is followed by a four probe technique to understand the conduction mechanism. The Hall voltage measurement is followed to monitor carrier concentrations and mobilities. The impressive conductivity and mobility values encourage the utility of the composites as photovoltaic material. Copyright © 2008 John Wiley & Sons, Ltd.     

Regioregular Poly[3‐(4‐alkoxyphenyl)thiophene]s: Evidence for a Two‐Step Aggregation Process

Summary: A chiral, regioregular poly[3‐(4‐alkoxyphenyl)thiophene] has been prepared and studied. Films prepared by fast evaporation of the solvent, consist of random‐coils, while films prepared by slow evaporation are composed of chirally aggregated, coplanar strands. Heat treatment transforms the random‐coils into aggregated films via an intermediate state, which was characterized as chiral, coplanar, unaggregated polymer strands.

Overview of the possible aggregation processes.     

Segmented poly[2‐methoxy‐5‐(2‐ethylhexyloxy)‐1,4‐phenylene vinylene] via xanthate and dithiocarbamate precursors: A comparative study of thermal eliminations

Segmented poly[2‐methoxy‐5‐(2‐ethylhexloxy)‐1,4‐phenylene vinylene] (MEH‐PPV)‐x's, which contain conjugated segments of varying lengths that are interspersed by nonconjugated units along the polymer backbone, were synthesized by selective thermal elimination of precursors containing controlled amounts (x) of a thermally labile group, namely, xanthate or dithiocarbamate (DTC). These precursors were in turn synthesized by competitive nucleophilic substitution of the Wessling polyelectrolyte with varying molar fractions of the respective nucleophiles—potassium ethyl xanthate or sodium diethyl dithiocarbamate. Methanol, used as the reaction medium, also served to introduce the second thermally less labile nucleophilic substituent. This approach for the preparation of segmented MEH‐PPV‐x is superior to the previous approach that used acetate as the thermally labile group, because it offers greater control over the composition despite a simpler synthetic procedure. Detailed studies of the thermal‐elimination kinetics of the three precursors, namely, acetate, xanthate, and DTC, both in solution and in thin films, were carried by in situ monitoring of their ultraviolet–visible spectra. These studies revealed that the rates of elimination followed the order, DTC > xanthate > acetate. The activation energies for the elimination were, however, not widely different (ca. 30 kcal/mol), suggesting that the rates primarily reflected differences in the pre‐exponential factor. After elimination, the segmented MEH‐PPV‐x samples exhibited the expected redshift in their absorption and fluorescence spectra with an increasing molar fraction (x) of eliminated segments, which was accompanied by a drastic reduction in the fluorescence quantum yields. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 3929–3940, 2003     

Electrochemical synthesis of poly(3‐methylthiophene): A kinetic study

Poly(3‐methylthiophene) (P3MT) films were electrogenerated on both platinum and carbon‐felt working electrodes. The kinetic equation was determined by the monomer and electrolyte concentrations being changed for different reaction times. For each sample, the weight of the polymer obtained was measured along with the polymerization charge, the oxidation charge, the ratio (R) between the two magnitudes, the charge storage efficiency (SE), and the doping level. The results obtained from the kinetic study indicate significant electrolyte participation in the electropolymerization process. The SE and the doping level decreased inversely proportionately to both the reaction time and the concentrations of the monomer and electrolyte. The ratio R increased with reaction time as well as with monomer or electrolyte concentrations for all P3MTs generated on the carbon‐felt electrodes, whereas for those films generated on platinum electrodes, the highest values were obtained for the lowest monomer and electrolyte concentrations. © 2000 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 38: 1258–1266, 2000     

Synthesis of chromo‐ and fluorogenic poly(ortho‐diaminophenylene) chemosensors for fluoride anion

Two new poly(ortho‐diaminophenylene) derivatives containing fluorene and/or quinoxaline moieties per repeat unit in the main chain were synthesized via Suzuki coupling reaction followed by reduction process. The synthesized polymers were characterized and explored as colorimetric and fluorometric anion‐sensing materials. The polymers in dilute tetrahydrofuran (THF) solution emitted green light (about 530 nm) in their precursor benzothiadiazole forms and blue to green light (477–523 nm) in their reduced forms. The color of polymer solution was dramatically altered upon addition of fluoride anion without noticeable absorption change in UV–vis spectrum. The fluorescence was ratiometrically quenched with a linear relationship between fluorescence intensity and fluoride anion concentration implying static quenching mechanism could be applied judging from the maintenance of constant fluorescence lifetime with variable fluoride anion concentration. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 1546–1556, 2007     

Highly substituted poly(2,3‐diphenyl‐1,4‐phenylenevinylene) derivatives having bulky phenyl and fluorenyl pendant groups: Synthesis,characterization, and electro‐optical properties

Two series of poly(2,3‐diphenyl‐1,4‐phenylenevinylene) (DP‐PPV) derivatives containing multiple bulky substituents were synthesized. In the first series, two different groups were incorporated on C‐5,6 positions of the phenylene moiety to increase steric hindrance and to obtain blue‐shifted emissions. In the second series, bulky fluorenyl groups with two hexyl chains on the C‐9 position were introduced on two phenyl pendants to increase the solubility as well as steric hindrance to prevent close packing of the main chain. Polymers with high molecular weights and fine‐tuned electro‐optical properties were obtained by controlling the feed ratio of different monomers during polymerization. The maximum photoluminescent emissions of the thin films are located between 384 and 541 nm. Cyclic voltammetric analysis reveals that the band gaps of these light‐emitting materials are in the range from 2.4 to 3.3 eV. A double‐layer EL device with the configuration of ITO/PEDOT/P4/Ca/Al emitted pure green light with CIE′1931 at (0.24, 0.5). Using copolymer P6 as the emissive layer, the maximum luminescence and current efficiency were both improved when compared with the homopolymer P4. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 6738–6749, 2006     

Electrosyntheses of high‐quality freestanding poly(fluorene‐co‐3‐methylthiophene) films with tunable fluorescence properties

The copolymerization of 3‐methylthiophene (MeT) and fluorene (FE) was successfully achieved in boron trifluoride diethyl etherate by the direct anodic oxidation of the monomer mixtures on a platinum electrode. The optimal feed ratio together with the best suitable potential for their copolymerization was determined. The as‐formed copolymer films, which were copolymerized with a feed ratio of FE/MeT = 2:1 at a constant potential of 1.3 V (vs a saturated calomel electrode), had the advantages of both poly(3‐methylthiophene) and polyfluorene, such as good electrochemical behavior, high conductivity, excellent thermal stability, and high film quality. The structure of the copolymer was investigated with ultraviolet–visible, infrared spectroscopy, and thermal analysis. Fluorescence spectroscopy studies revealed that the dedoped copolymer film in the solid state was a good blue‐light emitter with a strong emission at 435 nm and a shoulder at 459 nm. The emitting properties of the copolymer could be tuned by parameters during the electrochemical polymerization, such as the applied potential and monomer feed ratio. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 4904–4915, 2006     

Efficient blue‐green‐emitting poly[(5‐diphenylamino‐1,3‐phenylenevinylene)‐alt‐(2,5‐dihexyloxy‐1,4‐phenylenevinylene)] derivatives: Synthesis and optical properties

New poly(phenylene vinylene) derivatives with a 5‐diphenylamino‐1,3‐phenylene linkage (including polymers 2 , 3 , and 5 ) have been synthesized to improve the charge‐injection properties. These polymers are highly photoluminescent with fluorescent quantum yields as high as 76% in tetrahydrofuran solutions. With effective π‐conjugation interruption at adjacent m‐phenylene units, chromophores of different conjugation lengths can be incorporated into the polymer chain in a controllable manner. In polymer 2 , the structural regularity leads to an isolated, well‐defined emitting chromophore. Isomeric polymer 3 of a random chain sequence, however, allows the effective emitting chromophores to be joined in sequence by sharing a common m‐phenylene linkage (as shown in a molecular fragment). Double‐layer light‐emitting‐diode devices using 2 , 3 , and 5 as emitting layers have turn‐on voltages of about 3.5 V and produce blue‐green emissions with peaks at 493, 492, and 482 nm and external quantum efficiencies up to 1.42, 0.98, and 1.53%, respectively. In comparison with a light‐emitting diode using 2 , a device using 3 shows improved charge injection and displays increased brightness by a factor of ～3 to 1400 cd/m² at an 8‐V bias. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 2307–2315, 2006     

Effect of chemical modifications on the electronic structure of poly(3‐hexylthiophene)

The widespread use of poly(3‐hexylthiophene) (P3HT) in the active layers of organic solar cells indicates that it possesses chemical stability and solubility suitable for such an application. However, it would be desirable to have a material that can maintain these properties but with a smaller bandgap, which would lead to more efficient energy harvesting of the solar spectrum. Fifteen P3HT derivatives were studied using the Density Functional Theory. The conclusion is that it is possible to obtain compounds with significantly smaller bandgaps and with solubility and stability similar to that of P3HT, mostly through the binding of oxygen atoms or conjugated organic groups to the thiophenic ring. © 2013 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys., 2013     

Thermally stable red electroluminescent hybrid polymers derived from functionalized silsesquioxane and 4,7‐bis(3‐ethylhexyl‐2‐thienyl)‐2,1,3‐benzothiadiazole

Hyperbranched organic–inorganic hybrid conjugated polymers P1 and P2 were prepared via FeCl₃‐oxiditive polymerization of 4,7‐bis(3‐ethylhexyl‐2‐thienyl)‐2,1,3‐benzothiadiazole ( A ) and octa(3‐ethylhexyl‐2‐thienyl‐phenyl)polyhedral oligomeric silsesquioxane (POSS) ( B ) at different POSS concentrations. Compared to linear polymer PM derived from A , P1 , and P2 exhibit much higher PL quantum efficiency (?_PL‐f) in condensed state with improved thermal stability. ?_PL‐f of P1 and P2 increased by 80% and 400%, and the thermal degradation temperatures of P1 and P2 are increased by 35 °C and 46 °C, respectively. Light‐emitting diodes were fabricated using P1 , P2 , and PM . While the electroluminescent spectra of both P1 and PM show λ_max at 660 nm, P1 exhibits a much narrower EL spectrum and higher electroluminescence (～500%) compared with PM at a same voltage and film thickness. The maximum current efficiency of P1 is more than seven times of that of PM . The turn‐on voltages of the LEDs are in the order of P2 > PM > P1 . LED prepared by blending P1 with MEH‐PPV shows a maximum luminescence of 2.6 × 10³ cd/m² and a current efficiency of 1.40 cd/A, which are more than twice (1.1 × 10³ cd/m²) and five times (0.27 cd/A) of LED of PM /MEH‐PPV blend, respectively. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 5661–5670, 2009     

Synthesis of poly(m‐phenylene) and poly(m‐phenylene)‐block‐ poly(3‐hexylthiophene) with low polydispersities

Well‐defined poly(m‐phenylene) (PMP), which is poly(1,3‐dibutoxy‐m‐phenylene), was successfully synthesized via Grignard metathesis polymerization. PMP with a reasonably high number‐average molecular weight (M_n) of 25,900 and a very low polydispersity index of 1.07 was obtained. The polymerization of a Grignard reagent monomer, 1‐bromo‐2,4‐dibutoxy‐5‐chloromagnesiobenzene, proceeded in a chain‐growth manner, probably due to the meta‐substituted design producing a short distance between the MgCl and Br groups and thereby making a smooth nickel species (? C? Ni? C? ) transfer to the intramolecular chain end (? C? Ni? Br) over a benzene ring. PMP showed a good solubility in the common organic solvents, such as tetrahydrofuran, CH₂Cl₂, and CHCl₃. Furthermore, a new block copolymer comprised of PMP and poly(3‐hexylthiophene) was also prepared. The tapping mode atomic force microscopy image of the surface of the block copolymer thin film on a mica substrate showed a nanofibril morphology with a clear contrast. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011.     

Study on incomplete fluorescence quenching of cationic poly(p‐phenylenevinylene)s with different contents of cis‐ and trans‐vinylic linkages

Fluorescence properties of a series of cationic poly(p‐phenylenevinylene) (PPV) derivatives with different contents of cis‐ and trans‐vinylic linkages quenched by Fe(CN) were intensively investigated. PPVs with cis‐/trans‐vinylic linkages display downward Stern‐Volmer curves indicating incomplete quenching. The fluorescence quenching mechanism and the effect of many factors possible on the incomplete quenching has been examined, and the difference of the quenching behavior of two isomers was investigated, which further confirmed that the presence of cis‐vinylic linkages would most probably cause inaccessible fluorophores and thus the incomplete quenching. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2010     

One‐pot synthesis of conjugated poly(3‐hexylthiophene)‐b‐poly(phenyl isocyanide) hybrid rod–rod block copolymers and its self‐assembling properties

In this article, the synthesis of a series of conjugated rod–rod block copolymers based on poly(3‐hexylthiophene) (P3HT) and poly(phenyl isocyanide) (PPI) building blocks in a single pot is presented. Ni‐catalyzed Grignard metathesis polymerization of 2,5‐dibromo‐3‐hexylthiophene and subsequent addition of 4‐isocyanobenzoyl‐2‐aminoisobutyric acid decyl ester in the presence of Ni(dppp)Cl₂ as a single catalyst afford P3HT‐b‐PPI with tunable molecular weights and compositions. In solid state, microphase separation occurred as differential scanning calorimetric analysis of P3HT‐b‐PPI revealed two glass transition temperatures. In solutions, the copolymers can self‐assemble into spherical aggregates with P3HT core and PPI shell in tetrahydrofuran and exhibit amorphous state in CHCl₃. However, atomic force microscopy revealed that the block copolymers self‐assemble into nanofibrils on the substrate. These unique features warrant the resultant conjugated rod–rod copolymers' potential study in organic photovoltaic and other electronic devices. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013, 51, 2939–2947     

Structure and morphology control in thin films of regioregular poly(3‐hexylthiophene)

This review focuses on the structural control in thin films of regioregular poly(3‐hexylthiophene) (P3HT), a workhorse among conjugated semiconducting polymers. It highlights the correlation existing between processing conditions and the resulting structures formed in thin films and in solution. Particular emphasis is put on the control of nucleation, crystallinity and orientation. P3HT can generate a large palette of morphologies in thin films including crystalline nanofibrils, spherulites, interconnected semicrystalline morphologies and nanostructured fibers, depending on the elaboration method and on the macromolecular parameters of the polymer. Effective means developed in the recent literature to control orientation of crystalline domains in thin films, especially by using epitaxial crystallization and controlled nucleation conditions are emphasized. © 2011 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 49: 1218–1233, 2011