Low‐Band Gap Polyplatinaynes with Electron‐Accepting Silole Units

Summary: The synthesis and thermal, redox and photoluminescence properties of a soluble donor‐acceptor polyplatinayne with the electron‐accepting silole ring and its model compound are described. The polymer has an optical band gap of 2.10 eV which is much lower than that of thienyl‐ or silyl‐bridged congeners. The incorporation of electron‐accepting silole unit in the metallopolymer main chain creates a new π‐conjugated system that features unique donor‐acceptor characteristics.

     

Ink‐Jet Printing of Metallic Nanoparticles and Microemulsions

Summary: Two types of ink‐jet inks are presented: ink containing an aqueous dispersion of silver nanoparticles and an oil‐in‐water microemulsion‐based ink. The metallic ink contains nanoparticles of silver, which are formed in the presence of an ionic polymeric stabilizer. Sintering of the printed image obtained with the use of such silver‐based inks at temperatures as low as 300 °C results in formation of patterns possessing noticeable conductivity. The microemulsion inks are based on a thermodynamically stable microemulsion, in which the dispersed oil phase is a volatile solvent containing a water‐insoluble colorant. After contact of the jetted ink droplets with a substrate, nanodroplets of the microemulsion are converted into nanoparticles of the solubilized colorant. In some cases, it was found that the evaporation of microemulsion ink droplets leads to formation of rings composed of ordered nanoparticles.

Scheme of ink‐jet printing of an oil‐in‐water microemulsion followed by conversion of the nanodroplets into nanoparticles, caused by quick evaporation of the solvent within the microemulsion droplets. Therefore, the ink behaves as a dye‐based ink prior to printing, but after printing it behaves like a pigment‐based ink.     

Enhancement of Photostability in Blue‐Light‐Emitting Polymers Doped with Gold Nanoparticles

A dramatic increase in the photostability of a blue‐light‐emitting polymer, poly(9,9‐dioctylfluorene), was achieved by the addition of 5–10 nm gold nanoparticles. The optical absorption band of the gold nanoparticles was tuned to resonate the triplet exciton ground state bandgap energy of the polymer. Photo‐oxidation rate of poly(9,9‐dioctylfluorene) was effectively reduced by doping the polymer with very small amounts (≈10⁻⁶–10⁻⁵ volume fraction) of the gold nanoparticles.

Retarded photo‐oxidation in PDOF nanocomposite films with various doped gold nanoparticles.     

Novel Chromophore‐Functionalized Poly[2‐(trifluoromethyl) adamantyl acrylate‐methyl vinyl urethane]s with High Poling Stabilities of the Nonlinear Optical Effect

Nonlinear optical vinyl polymers with high glass transition temperature (T_g) were prepared by the functionalization of a fluorinated acrylate‐methyl vinyl isocyanate copolymer. A modified pathway to obtain a thiophene bridged chromophore was worked out. Poled films of the polymers show a fairly high and stable nonlinear optical response, even at elevated temperatures.

The thiophene‐bridged chromophore, based on a substituted dicyanomethylene‐dihydrofuran acceptor, synthesized here.     

A Low Curing Temperature Silver Ink for Use in Ink‐Jet Printing and Subsequent Production of Conductive Tracks

Summary: A drop‐on‐demand ink‐jet printer has been used to print a silver‐organic solution onto glass substrates. Conductive silver tracks were obtained by heat treatment of the ink‐jet printed deposits at temperatures ranging from 125 °C–200 °C in air. Resistivity values were found to have dropped to two to three times the theoretical resisitivity of bulk silver after temperatures of 150 °C and above were used.

Resistivity values of a silver‐based ink.     

Polymer‐Based Rectifying Diodes on a Glass Substrate Fabricated by Ink‐Jet Printing

Summary: The fabrication of polymer diodes on a glass substrate by an ink‐jet printing technique is reported. Both an n‐type semiconductive polymer, poly[2‐methoxy‐5‐(2‐ethylhexyloxy)‐1,4‐(1‐cyanovinylene)phenylene] (CN‐PPV), and a p‐type semiconductive polymer, polypyrrole (PPy) or poly(3,4‐ethylenedioxythiophene) (PEDOT), were printed through a piezoelectric ink‐jet printer. The printed CN‐PPV/PPy and CN‐PPV/PEDOT diodes showed good rectifying characteristics. These results indicate the potential of the low‐cost ink‐jet printing technique to produce polymer microelectronic devices and circuits.

Schematic diagram of the printed polymer diode     

Anthracene‐Containing Wide‐Band‐Gap Conjugated Polymers for High‐Open‐Circuit‐Voltage Polymer Solar Cells

The synthesis, characterization, and photophysical and photovoltaic properties of two anthracene‐containing wide‐band‐gap donor and acceptor (D–A) alternating conjugated polymers ( P1 and P2 ) are described. These two polymers absorb in the range of 300–600 nm with a band gap of about 2.12 eV. Polymer solar cells with P1 :PC₇₁BM as the active layer demonstrate a power conversion efficiency (PCE) of 2.23% with a high V_oc of 0.96 V, a J_sc of 4.4 mA cm⁻², and a comparable fill factor (FF) of 0.53 under simulated solar illumination of AM 1.5 G (100 mW cm⁻²). In addition, P2 :PC₇₁BM blend‐based solar cells exhibit a PCE of 1.42% with a comparable V_oc of 0.89 V, a J_sc of 3.0 mA cm⁻², and an FF of 0.53.

     

Fluorene‐Based Co‐polymer with High Hole Mobility and Device Performance in Bulk Heterojunction Organic Solar Cells

A new donor–acceptor polymer based on 9,9‐dioctylfluorene is synthesized and tested in organic photovoltaic devices. Results show that the polymer exhibits good solubility in a range of organic solvents and has a high hole mobility. When blended with a PC₇₀BM acceptor and fabricated into a bulk heterojunction, photovoltaic devices having a maximum power conversion efficiency (PCE) of 6.2% and a peak external quantum efficiency of 74% are created. Such efficiencies are realized without any necessity for solvent additives or thermal annealing protocols.

     

Fabrication of Robust High‐Quality ORMOCER® Inverse Opals

Summary: The nanostructuring of ORMOCER® to form inverse opals is described. For this purpose a polymer opal is used as a template and infiltrated with liquid ORMOCER®. After photopolymerization of the resin the host opal is dissolved in tetrahydrofuran and an ORMOCER® inverse opal is obtained. It shows excellent periodicity (by SEM) and optical properties to reveal a high degree of face centered cubic order. This replication process leads to a nanostructured photonic crystal with the outstanding mechanical properties of ORMOCER® and high temperature stability up to 350 °C.

ORMOCER® inverse opal annealed at 200 °C for 10 h.     

Ink‐Jet Printing of Luminescent Ruthenium‐ and Iridium‐Containing Polymers for Applications in Light‐Emitting Devices

Summary: Defined films of luminescent ruthenium(II ) polypyridyl‐poly(methyl methacrylate) (PMMA) and iridium(III ) polypyridyl‐polystyrene (PS) copolymers could be prepared by ink‐jet printing. The copolymers were deposited on photoresist‐patterned glass substrates. Films as thin as 120 nm could be printed with a roughness of 1 to 2%. In addition, the film thickness could be varied in a controlled way through the number of droplets deposited per unit area. The topography of the ink‐jet printed films was analyzed utilizing an optical profilometer. The absorbance and emission spectra were measured using fast parallel UV‐vis and fluorescence plate reader.

Photo of the solutions of luminescent ruthenium (left) and iridium (right) containing polymers in a glass microtiter plate (top). The subsequently prepared films using ink‐jet dispensing techniques are shown below.     

Gold Nanoparticles Functionalized by a Dextran‐Based pH‐ and Temperature‐Sensitive Polymer

A dextran‐based dual‐sensitive polymer is employed to endow gold nanoparticles with stability and pH‐ and temperature‐sensitivity. The dual‐sensitive polymer is prepared by RAFT polymerization of N‐isopropylacrylamide from trithiocarbonate groups linked to dextran and succinoylation of dextran after polymerization. The functionalized nanoparticles show excellent stability under various conditions and can be stored in powder‐form. UV and DLS measurements confirm that the temperature‐induced optical changes and aggregation behaviors of the particles are strongly dependent on pH.

     

Effect of the Molecular Weight of AB Diblock Copolymers on the Lamellar Orientation in Thin Films: Theory and Experiment

We propose a theoretical explanation of the parallel and perpendicular lamellar orientations in free surface films of symmetric polystyrene‐block‐polybutadiene diblock copolymers on silicon substrates (with a native SiO_x layer). Two approaches are developed: A correction to the strong segregation theory and a qualitative analysis of the intermediate segregation regime. We show that the perpendicular orientation of the lamellae formed by the molecules of high molecular weight is stabilized by A–B interfacial interactions. They are weaker in the case of the perpendicular orientation of the lamellae, whereas the surface tension coefficient of the A–B interface decreases with the increase of the molecular weight.

     

Ink‐Jet Printing,Self‐Assembled Polyelectrolytes,and Electroless Plating: Low Cost Fabrication of Circuits on a Flexible Substrate at Room Temperature

Summary: The driving forces behind the development of flexible electronics are their flexibility, lightweightedness, and potential for low‐cost manufacturing. However, because of physical limitations, traditional thermal processes cause deformations in the flexible substrate. As a result, the adhesion quality of the printed wires is deteriorated. This article reviews recent developments in printing circuits on a flexible substrate by combining self‐assembled polyelectrolytes, ink‐jet printing of a catalyst, and electroless plating of metals. The limitations and potential applications of this technology are also discussed. Experiments implementing this technology demonstrated significant results. By a vibration‐induced assistance during an ink‐jet printing catalyst process, line width and blurring can be controlled to within ±3% variation. Following the IPC 6013 standard for flexible electronics, the results after thermal cycling (288 °C, 6 times) and a hot oil test (260 °C, 3 times) indicated that the metallic circuit had retained excellent adhesion properties and electric characteristics. We also report the first successful demonstration of a metal film in a via‐hole inner wall on a flexible substrate. This novel fabrication method is ideal for the realization of large area, flexible electronics and future multilayer flexible substrate application, such as flexible display, chip on flexible substrate, etc., particularly where traditional lithographic processes can not be applied.

Flexible high‐density circuit on an FR‐4 substrate (left) and picture of via hole with copper inner wall (right).     

Self‐Assembled Hollow Polyaniline/Au Nanospheres Obtained by a One‐Step Synthesis

Self‐assembled hollow nanosphere composites of polyaniline and Au nanoparticles (PANI‐p‐TSA/Au) were chemically synthesized from solutions containing p‐toluenesulfonic acid (p‐TSA) with the addition of gold chloride trihydrate as the oxidant. The composite materials were characterized by SEM, TEM, and a range of spectroscopic methods. Spectroscopic characterizations confirmed that the polymeric product is a form of doped PANI, while electron diffraction and X‐ray diffraction showed that elemental Au was present in the PANI‐p‐TSA/Au nanocomposites. The room temperature electrical conductivity of the PANI‐p‐TSA/Au nanocomposites was two orders of magnitude greater than a PANI‐p‐TSA obtained in the presence of ammonium persulfate as the oxidant under the same conditions.

     

Effect of Cocatalysts on the Catalytic Activities of Tantalum‐ and Niobium‐Based Catalysts for Ring‐Opening Metathesis Polymerization of Norbornene

A series of pentavalent tantalum and niobium complexes with aryloxy ligands was prepared, and their catalytic behavior for the ROMP of norbornene was studied in the presence of an alkylaluminum cocatalyst. Tantalum complexes 1 – 4 showed very high activity for the ROMP of NBE in combination with ⁱBu₃Al to give high‐molecular‐weight polymers. In contrast, the niobium complexes 5 and 6 , as well as NbCl₅, exhibited very high activity upon activation with Me₃Al to give high‐molecular‐weight polymers.

     

Resilient Amorphous Networks Prepared by Photo‐Crosslinking High‐Molecular‐Weight D,L‐Lactide and Trimethylene Carbonate Macromers: Mechanical Properties and Shape‐Memory Behavior

Tough networks are prepared by photo‐crosslinking high‐molecular‐weight DLLA and TMC macromers. These amorphous networks exhibit tunable thermal and mechanical properties and have excellent shape‐memory features. Variation of the monomer ratio allows adjustment of T_g between approximately ?13 and +51 °C. The elastic moduli at room temperature can be varied between 4.5 and 2730 MPa. The crosslinks allow the networks to return to their original shape after deformation. 60:40 DLLA:TMC networks have T_g values between room temperature and body temperature, with mechanical properties at body temperature close to soft tissues. Several medical devices are prepared from these networks.

     

Ethylene and Ethylene/Propylene Polymerization Behavior of Bis(phenoxy‐imine) Zr and Hf Complexes with Perfluorophenyl Substituents

The catalytic properties of bis(phenoxy‐imine) Zr and Hf complexes incorporating perfluorophenyl groups with methylaluminoxane were investigated. The fluorinated complexes produced far higher‐molecular‐weight polyethylenes and ethylene/propylene copolymers with increased activities compared with the non‐fluorinated congeners. Moreover, the fluorinated complexes displayed a higher incorporation ability for propylene.

Structures of complexes 1 – 4 .     

Vapor‐Based Synthesis of Poly[(4‐formyl‐p‐xylylene)‐co‐(p‐xylylene)] and Its Use for Biomimetic Surface Modifications

Summary: The vapor‐based synthesis and characterization of a reactive polymer, poly[(4‐formyl‐p‐xylylene)‐co‐(p‐xylylene)] ( 1 ), have been reported. The reactive polymer coating enables the immobilization of oligosaccharides via the chemoselective aldehyde‐hydrazide coupling reaction.

     

Effect of Turbulent Flow on Coil‐Globule Transition of λ‐DNA

Summary: The addition of spermidine (SPD) into turbulent flow as a condensing agent showed the abrupt change of turbulent drag reducing (DR) efficiency of λ‐DNA in turbulent flow for the first time. The resultant asymptote DR efficiency explains the origin of those changes, which can be conclusively verified via the electrophoresis experiment. Despite the different fluid conditions, with and without condensing agent, all λ‐DNA molecules possessed the same half‐cut dimension, implying that the discrete change of DNA conformation can dramatically alter the flow characteristics.

Coil‐globule transition of DNA by spermidine.     

Synthesis and Photovoltaic Properties of a Thienylenevinylene and Diketopyrrolopyrrole Copolymer with High Mobility

A novel donor–acceptor‐type polymer with a low band‐gap that alternates electron‐rich thienylenevinylene groups with electron‐deficient diketopyrrolopyrrole (DPP) units (PETVTDPP) has been synthesized by Pd‐catalyzed Stille cross‐coupling polymerization. The polymer shows a broad absorption band of wavelengths that range from 330 to 900 nm, and a low band‐gap value of 1.43 eV. The field‐effect mobility of an organic thin‐film transistor based on this polymer is 0.05 cm² · Vs⁻¹. Bulk‐heterojunction solar cells using a mixture of PETVTDPP and PC_[71]BM for the active layer show a power conversion efficiency (PCE) of 1.94% under simulated AM 1.5 G solar irradiation at 100 mW · cm⁻².