A New Dithienylbenzotriazole‐Based Poly(2,7‐carbazole) for Efficient Photovoltaics

A new dithienyl benzotriazole‐based conjugated polymer was synthesized by Suzuki coupling reaction. The polymer was found to be soluble in common organic solvents, such as chloroform, tetrahydrofuran and chlorobenzene, with excellent film‐forming properties. The structure of the polymer was confirmed by ¹H NMR, the molecular weights determined by GPC and the thermal properties investigated by TGA and DSC. The polymer films exhibited an absorption band in the wavelength range 300 to 610 nm. Preliminary photovoltaic cells based on the composite structure of indium tin oxide (ITO)/PEDOT:PSS/ PCDTBTz:PC ₆₀ BM (1:2 w/w)/Al showed an open‐circuit voltage of 0.92 V, a power conversion efficiency of 2.2% and a short circuit current of 5.33 mA cm^?2.

     

Modification of Oligomeric Cyanate Ester Polymer Properties with Multi‐Walled Carbon Nanotube‐Containing Particles

The properties of an oligomeric cyanate ester polymer were modified by the addition of 0.01–3 wt.‐% multi‐walled carbon nanotube (MWNT) containing particles. The dynamic mechanical behavior and thermal properties of the cyanate ester/MWNT nanocomposites were evaluated. The storage modulus, G′, of the nanocomposite with 1 wt.‐% MWNT particles was nearly 60 and 600% higher than the neat polymer at 100 and 200 °C, respectively. The glass transition temperature of the nanocomposite was also raised by 30 °C and its thermal stability in air and nitrogen was increased by 58 and 25 °C, respectively. The property improvements are attributed to reinforcement of the cyanate ester as a result of good nanotube dispersion and effective polymer‐MWNT interaction.

     

Electroactive Polymer with Oligoanilines in the Main Chain: Synthesis,Characterization and Dielectric Properties

An electroactive polymer with well‐defined oligoanilines in the main chain has been prepared by oxidative coupling polymerization. The detailed characteristics of the polymer were systematically studied by FT‐IR, ¹H NMR, GPC and XRD. Its electrochemical behavior was explored with UV‐Vis spectra and cyclic voltammetry showing that its intrinsic electroactivity was maintained and exhibited three distinct reversible oxidative states. Its electrical conductivity is about 3.91 × 10^?4 S · cm^?1 in HCl‐doped form at room temperature. Furthermore, the polymer displays a dielectric constant of 48.4 and 13.6 at 10 and 1 MHz, respectively, mainly attributed to the improvement in delocalized charge density and electrical conductivity of the polymer by introduction of the conjugated oligoaniline segments.

     

Thermoreversible Supramolecular Organization in Poly(vinylidene fluoride)–Dodecyl Benzene Sulfonic Acid Blends

Blends of poly(vinylidene fluoride) (PVF₂) and dodecyl benzene sulfonic acid (DBSA) were found to phase separate in the melt state from hot‐stage polarizing optical microscopy and differential scanning calorimetry (DSC). Both these studies also indicated the formation of a reversible mesomorphic order in the DBSA‐rich phase of the blends. Scanning electron microscopy (SEM) showed a fibrillar network morphology of the DBSA‐rich phase. Wide‐angle X‐ray diffraction (WAXD) revealed the formation of a lamellar structure in the blends corresponding to a long period of 26 Å. The mesomorphic nature of the blends is believed to arise from the supramolecular organization of the surfactant molecules within the lamella. Thermal study indicated that the supramolecularly organized complex is the VF₂ monomer unit:DBSA ≈ 4:1, and the enthalpy of complexation is ～723 J · mol^?1.

SEM micrograph of a PVF₂‐DBSA blend with weight fraction of DBSA (W_DBSA) = 0.62.     

Synthesis,Characterization and Field‐Effect Transistor Performance of Poly[2,6‐bis(3‐alkylthiophen‐2‐yl)benzo[1,2‐b;4,5‐b′]diselenophene]s

Benzo[1,2‐b:4,5‐b′]diselenophene (BDS) has been incorporated for the first time in a polymer. bis(Stannyl)‐functionalized BDS was copolymerized with 3,3′‐bis(alkyl)‐5,5′‐bithiophenes (dodecyl and tetradecyl side chains) through Stille copolymerization, to yield p‐type polymer semiconductors for organic field‐effect transistor application. The electronic and structural effect of the selenium atoms, compared to sulphur atoms in analogous copolymers, is described. The molecular weight has a decisive influence on the photophysical properties and supramolecular ordering, expressed in field‐effect transistor measurements. Saturation mobilities around 10^?2 cm² · V^?1s^?1 are obtained on standard silicon substrates.

     

Facile Synthesis of Nanoporous Hydroquinone/Catechol Formaldehyde Resins and their Highly Selective,Efficient and Regenerate Reactive Adsorption for Gold Ions

We present a new type of nanoporous hydroquinone/catechol formaldehyde resin synthesized by a one‐pot route, with a surface area of up to 1 112 m² · g^?1. The resins show highly efficient reactive adsorption for silver/gold (silver adsorbance up to 2.43 g · g^?1) and excellent selectivity for gold (K_d is as high as 1 914 090 mL · g^?1). The first‐used resins can be regenerated with NaHSO₃, and the gold capacities of the recycled PCFR and PHFR reach 44 and 78% of their first loading capacities, respectively.

     

Synthesis and Characterization of Polymer Brushes on Micromechanical Cantilevers

Summary: A technique to cover microelectromechanical systems (MEMS), such as micromechanical cantilever (MC) sensors, with a covalently bound brush layer has been developed. The polymer layer was grown using a “grafting‐from” synthesis of polymer brushes under mild conditions, by surface‐initiated atom transfer radical polymerization. Atomic force microscopy (AFM) and ellipsometry have revealed a uniform thickness of about 12 nm from which a grafting density of polymer brushes of 0.19 chains · nm^?2 was estimated. The coating with polymer brushes can be realized on a selected surface. It was shown that a single‐sided brush layer swells reversibly in toluene, resulting in a bending of the micromechanical cantilever.

Schematic representation of the PMMA brush synthesis on the MC surface, by surface‐initiated ATRP.     

Synthesis and Photovoltaic Properties of Alternating Conjugated Polymers Derived from Indeno[1,2‐b]fluorene and Bithiophene or Thieno[3,2‐b]thiophene‐Cored Benzothiadiazole

Two narrow bandgap copolymers derived from 6,6′,12,12′‐tetraoctyl‐indeno[1,2‐b]fluorene and bithiophene or thieno[3,2‐b]thiophene‐cored benzothiadiazole are synthesized and characterized. The copolymers show broad absorption in the range 350–700 nm. The application of the copolymers as photovoltaic cells with configurations ITO/PEDOT:PSS/blend/Al and ITO/PEDOT:PSS/blend/interlayer/Al is investigated. A power conversion efficiency (PCE) of approximately 3.0% is achieved under an AM 1.5G solar simulator (80 mW cm^?2) for the cells with ITO/PEDOT:PSS/polymer:PC₇₁BM([6,6]‐phenyl‐C₇₁ butyric acid methyl ester) (1:4)/interlayer/Al.

     

Fluorinated Styrene‐ and Carbazole‐Based Cladding Polymer Layers for EO and NLO Polymer Devices

Novel polymer cladding materials were synthesized and their potential for use in optical waveguide devices was investigated. 9‐[2‐(2,3,5,6‐Tetrafluoro‐4‐vinylphenoxy)ethyl]‐9H‐carbazole and 1‐pentafluorophenylpyrrole‐2,5‐dione were used as comonomers for preparing the acrylic cladding copolymers. These showed a low resistivity (≈2 × 10¹³ Ω · cm) at room temperature and a low optical loss (?0.6 dB · cm^?1) at a wavelength of 1.55 µm. The refractive indexes and the glass transition temperatures of the polymer cladding materials can be controlled by the composition of the copolymers. The resulting polymers are good candidates for cladding materials for practical applications in devices.

     

High‐Content Pendant Photochromic Copolymer with Dithienylethene/Fluorene 2:1 Mole Ratio

Summary: Two photochromic dithienylethene units were incorporated into one fluorene unit as a monomer and the mole ratio of photochromic unit/repeat unit reached to 2:1 using this monomer. The content of dithienylethene component in the polymer could be improved effectively by polymerization of this monomer, which contains more than one dithienylethene units. All the starting materials concerned in the synthesis are commercially available and so the synthesis could be performed on a large scale. The polymer obtained by typical palladium‐catalyzed Suzuki coupling reaction is photochromic both in solution and in solid state and possesses good solubility. The photochromic and photomodulation luminescence properties of the polymer are also presented.

Structure of the photochromic polymer based on dithienylethene.     

Spectroelectrochemical and Photovoltaic Characterization of a Solution‐Processable n‐and‐p Type Dopable Pyrrole‐Bearing Conjugated Polymer

D‐A‐D‐type polymers are of high interest in the field of photovoltaics and electrochromism. In this study we report the synthesis and electrochemical properties of PPyBT along with its photophysical properties and photovoltaic performance. PPyBT is soluble in common organic solvents and both n‐ and p‐type dopable, which is a desired property for conjugated polymers. During electrochemistry studies, the onset potentials of the polymer were determined as +0.2 V for oxidation and ?1.4 V for reduction. Using these values, HOMO and LUMO energy levels were calculated. The photovoltaic properties of PPyBT were also studied. PL studies showed that there is a charge transfer between PPyBT (donor) and PCBM (acceptor).

     

Surface Area Effects in Hydroxyapatite/Poly(ε‐caprolactone) Nanocomposites

In order to understand the contribution of nanoparticle surface area to the properties of nanocomposite materials, hydroxyapatite nanoparticles with different specific surface areas (60 m² · g^?1 and 111 m² · g^?1) were synthesized using reverse microemulsion and processed into nanocomposites. Experimental results indicated that the thermomechanical reinforcement did show a dependence on nanoparticle surface area, although the transition temperatures did not. The reinforcement trends were dependent on temperature, suggesting that the nanoparticles had a greater impact on the amorphous polymer chains. The reinforcement above T_g may be plotted against nanoparticle surface area to obtain a single reinforcement trend, suggesting that surface area is a general parameter for nanocomposite property control.

     

Electrochromic Response of Nanostructured Poly(3,4‐ethylenedioxythiophene) Films Grown in an Aqueous Micellar Solution

Poly(3,4‐ethylenedioxythiophene) (PEDOT) films have been electropolymerized from an aqueous micellar solution encompassing the monomer (EDOT) and the moieties sodium dodecyl sulfate (SDS) and lithium triflate. The presence of these anionic dopants in the polymer matrix and a doping level of 0.26 have been confirmed by X‐ray photoemission and electron paramagnetic resonance (EPR) spectroscopy. The hydrophobic micellar core encompassing the monomer orchestrates the growth of a uniform homogeneous polymer deposit as electron microscopy and atomic force microscopy studies reveal the film to be composed of a continuous interlinked network of quasi‐spherical grains (50–150 nm in dimensions) and pores alongwith a low surface roughness. The film exhibits a large coloration efficiency of 153 cm² · C^?1 and a transmission modulation of 62% (λ = 632.8 nm), which are manifestations of the open ion‐permeable morphology. The Q_{(inserted/extracted)} ratio ranges between 1.2 and 1.4 when cycled back and forth between the clear and blue states 2 500 times, thereby affirming the suitability of these films for practical electrochromic smart windows.

     

Multifunctional Porous Poly(vinylidene fluoride)‐graft‐Poly(butyl methacrylate) with Good Li+ Ion Conductivity

PnBMA is grafted on PVDF using ATRP in NMP solution at 90 °C and characterized by means of 1D and 2D NMR. ¹⁹F NMR spectra clearly reveal that the attack occurs on the head‐head >CF₂ groups. Cast PB films show a honeycomb‐patterned porous microstructure, and the “breath‐figure” model is used to explain pore formation. FT‐IR spectra suggest a supramolecular interaction between >C?O groups of PnBMA and >CF₂ groups of PVDF. Storage modulus, loss modulus and stress at break decrease with graft conversion, but the strain at break increases significantly. The toughness of the copolymers also increases dramatically (882%). The porous materials can be applied as solid‐state electrolytes (Li⁺‐doped) with good ionic conductivity (10^?5 S · cm^?1).

     

On the Mechanism of the Ring‐Expansion Polymerization of Thiiranes

Ring polymers are synthesized using a cyclic bifunctional thioester as initiator for REP of thiiranes. PMT yields satisfactory results, whereas polymerization with MT appears to develop dead polymeric material as by‐product and TBMT gives only negligible conversion rates. The process produces high yields and high conversion rates. The corresponding molecular weight distributions show increasing broadening and multimodal character with increasing reaction time due to thermodynamically controlled ring‐merging reactions between macrocycles. The polymerization rate of PMT obeys a pseudo first‐order kinetics with an activation energy of 38.8 kJ mol^?1. ¹H NMR, ESI‐MS, and glass transition temperatures independent of the molecular weight demonstrate the presence of cyclic polymer.

     

Synthesis,Electrochemical and Photovoltaic Properties of Multi‐Armed Polythiophenes with Triphenylamine Trivinylene as Conjugated Linker

Three polythiophenes with 5%, 10% and 15% triphenylamine trivinylene (TPAV) as bridge linker, PT‐TPAV5, PT‐TPAV10 and PT‐TPAV15, were synthesized. The Wittig‐Horner‐Emmons reaction and the Stille method were employed to synthesize these polymers. The polythiophenes were subsequently used in bulk‐heterojunction polymer solar cells (PSCs) as donor materials. The polymers exhibited a striking and reversible color change after the oxidation of the polymer films. The power conversion efficiencies of the PSCs based on PT‐TPAV5, PT‐TPAV10 and PT‐TPAV15 as donors and PCBM as acceptor were 0.17%, 0.50%, and 0.35%, respectively, under the illumination of AM 1.5, 100 mW · cm^?2.

     

Synthesis of Silica‐Supported Metallocene Catalysts for Olefin Polymerization

Four supported metallocene catalysts were synthesized directly on silica [Si(CpZrCp), Si(CpZrInd), Si(IndZrCp), and Si(IndZrInd)]. The first ligand was chemically tethered to silica (internal ligand) while the second was free from silica (external ligand). The polymerization of ethylene and the copolymerization of ethylene with hexene were investigated. The activity of the catalysts and the molecular weights of the polymers were found to depend on the position of the ligands. In all cases, high‐molecular‐weight polyethylene with moderate polydispersity was obtained. Moreover, the copolymerization of ethylene with hexene provided a homogeneous polymer.

Reaction of ZrCl₄(OC₄H₈)₂ with modified silica (SiCp).     

α,ωn‐Heterotelechelic Hyperbranched Polyethers Solubilize Carbon Nanotubes

The synthesis of novel linear‐hyperbranched (linhb) polyether block copolymers based on poly(ethylene oxide) and branched poly(glycerol), bearing a single pyrene or myristyl moiety at the α‐position of the linear chain is described. The polymers exhibit low polydispersity ( < 1.3) and controlled molecular weights ( = 5 000 g · mol^?1). The mainly hydrophilic block copolymers with multiple hydroxyl end groups readily dissolve multiwalled carbon nanotubes (MWCNTs) in water by mixing and subsequent sonification, resulting in noncovalent attachment of the linhb hybrid structure to the carbon nanotubes (CNTs). Transmission electron microscopy (TEM) was employed to visualize the solubilized nanotubes; after sulfation of the multiple hydroxyl groups the polymer layer was detected in the TEM images.

     

Cyclodextrins in Polymer Synthesis: Free Radical Polymerization of β‐Cyclodextrin Complexes of Photosensitive Mesoionic 6‐Oxo‐1,6‐dihydropyrimidin‐3‐ium‐4‐olates in Aqueous Medium

Solid mesoionic 2‐[2‐(isopropenylcarbonyloxy)ethylthio]‐1‐methyl‐6‐oxo‐3‐phenyl‐5‐propyl‐1,6‐dihydropyrimidin‐3‐ium‐4‐olate was complexed in water using β‐cyclodextrin (β‐CD) and randomly methylated β‐CD, which resulted in polymerizable complexes with 2:1 stoichiometry. The β‐CD complex was characterized using ¹H NMR, ROESY NMR and UV spectroscopy. Polymerization of the complex prepared from methylated β‐CD led to a photosensitive polymer, which precipitated during polymerization and was nearly free of CD. Polymerization was carried out with a water‐soluble redox initiator. In addition, a copolymer with methyl methacrylate was prepared from the complexes, which showed a different mass‐dependent distribution in the incorporation in comparison to a copolymer prepared without CD in organic solvents.

     

Towards Highly Substituted Starburst Macromolecular Semiconductors: Microwave Synthesis,Spectroscopy and Electrochemical Properties

As part of a strategy to explore highly functionalized macromolecular semiconductors, a series of highly substituted twelve‐armed macromolecules F1CzTr‐F3CzTr consisting of truxene, 9‐phenylcarbazole and oligofluorene units were synthesized. To accomplish the synthesis of twelve‐armed targets, a high yield microwave enhanced synthesis method for direct twelve‐fold Suzuki couplings was developed. The resulting materials exhibited high purity and good monodispersity (PDI 1.01–1.03). The molecular weight of the compound F3CzTr achieved 14 266 g · mol^?1, representing one of the largest well‐defined starburst conjugated molecules. The thermal, photophysical and electrochemical properties were investigated.