New polyethylene macroinitiators and their subsequent grafting by atom transfer radical polymerization

A semicrystalline polyethylene (PE) macroinitiator was prepared by copolymerizing ethylene and an inititating monomer (5-norbornen-2-yl-2'-bromo-2'-methyl propanoate) (3) using [N-(2,6-diisopropylphenyl)-2-(2,6-diisopropylphenylimino)isobutanamidato]-Ni(eta1-CH2Ph)(PMe3) (1) and Ni(COD)2 (bis(1,5-cyclooctadiene)-nickel) (2). Although 3 decomposes Ni(COD)2, if the initiating species (1/2) are exposed to ethylene for a period of time, t1, and then 3 is introduced for another period of time, t2, the polymerization takes place in a controlled manner. Variations in temperature, pressure, and [3] afford a great deal of control over the composition and architecture of the PE macroinitiator. Subsequent grafting with methyl methacrylate (MMA) yields PE-graft-PMMA with narrow polydispersities and increasing PMMA content at longer reaction times. Because the products are semicrystalline materials with high melting points, they are anticipated to function as blend compatibilizers for linear polyethylene.     

An n-Type Conjugated Oligoelectrolyte Mimics Transmembrane Electron Transport Proteins for Enhanced Microbial Electrosynthesis

Interfacing bacteria as biocatalysts with an electrode provides the basis for emerging bioelectrochemical systems that enable sustainable energy interconversion between electrical and chemical energy. Electron transfer rates at the abiotic-biotic interface are, however, often limited by poor electrical contacts and the intrinsically insulating cell membranes. Herein, we report the first example of an n-type redox-active conjugated oligoelectrolyte, namely COE-NDI , which spontaneously intercalates into cell membranes and mimics the function of endogenous transmembrane electron transport proteins. The incorporation of COE-NDI into Shewanella oneidensis MR-1 cells amplifies current uptake from the electrode by 4-fold, resulting in the enhanced bio-electroreduction of fumarate to succinate. Moreover, COE-NDI can serve as a “protein prosthetic” to rescue current uptake in non-electrogenic knockout mutants.     

Photoswitchable Conjugated Oligoelectrolytes for a Light-Induced Change of Membrane Morphology

The synthesis of a new conjugated oligoelectrolyte (COE), namely DSAzB, is described, which contains a conjugated core bearing a diazene moiety in the center of its electronically delocalized structure. Similar to structurally related phenylenevinylene-based COEs, DSAzB readily intercalates into model and natural lipid bilayer membranes. Photoinduced isomerization transforms the linear trans COE into a bent or C-shape form. It is thereby possible to introduce DSAzB into the bilayer of a cell and disrupt its integrity by irradiation with light. This leads to controlled permeabilization of membranes, as demonstrated by the release of calcein from DMPG/DMPC vesicles and by propidium iodide influx experiments on S. epidermidis. Both experiments support that the permeabilization is selective for the light stimulus, highly efficient, and repeatable. Target-selective and photoinduced actions demonstrated by DSAzB may have broad applications in biocatalysis and related biotechnologies.     

Effect of the chemical structure of a tetradentate equatorial ligand on the spin-crossover properties of the Fe (III) complexes chain structures: Electron paramagnetic resonance study

The effect of the chemical structure of the equatorial ligand on the spin state of the Fe (III) ion in a series of 1-D chain complexes of the general formula [Fe(L)(tvp)]BPh₄·nCH₃OH, where L = dianions of Schiff base containing a different number of aromatic groups: N,N′-ethylenebis (salicylaldimine) (salen) 1 , N,N′-ethylenebis (acetylacetone)2,2′-imine (acen) 2 , N,N′-ethylenebis (benzoylacetylacetone)2,2′-imine (bzacen) 3 , and tvp = 1,2-di(4-pyridyl)ethylene, was studied by ultraviolet–visible (UV–vis) and electron paramagnetic resonance (EPR) methods. The values of exchange interactions, thermodynamic parameters of spin-crossover, and electronic structure features of the Fe (III) complexes were estimated from the EPR data. The substitution of a fragment of the equatorial ligand L in the series salen–acen–bzacen changes the local symmetry of the complex in the 1-D chain, thereby affecting the spin variable properties.     

Over 9% efficiency achieved for all-polymer solar cells processed by a green solvent

正Bulk-heterojunction polymer solar cells(PSCs)have attracted considerable attention owning to their potential for fabricating flexible,light-weight and large area solar cell panels via high-throughput roll-to-roll technologies.Compared with conventional PSCs comprising small molecule acceptors,such as fullerenes,all-polymer solar cells(all-PSCs)containing blends of p-type/n-type polymers in the photoactive layer provide advantages including easily     

Processing additives for improved efficiency from bulk heterojunction solar cells

Two criteria for processing additives introduced to control the morphology of bulk heterojunction (BHJ) materials for use in solar cells have been identified: (i) selective (differential) solubility of the fullerene component and (ii) higher boiling point than the host solvent. Using these criteria, we have investigated the class of 1,8-di(R)octanes with various functional groups (R) as processing additives for BHJ solar cells. Control of the BHJ morphology by selective solubility of the fullerene component is demonstrated using these high boiling point processing additives. The best results are obtained with R = Iodine (I). Using 1,8-diiodooctane as the processing additive, the efficiency of the BHJ solar cells was improved from 3.4% (for the reference device) to 5.1%.     

Synthesis and characterization of low‐bandgap cyclopentadithiophene‐biselenophene copolymer and its use in field‐effect transistor and polymer solar cells

Novel series of conjugated copolymers, incorporating cyclopentadithiophene (CPDT) and the biselenophene ( R‐CPDT‐Se2 ), were synthesized by Pd‐catalyzed Stille coupling polymerization. The optical, electrochemical, field‐effect carrier mobilities, and photovoltaic properties of the R‐CPDT‐Se2 were investigated and compared with cyclopentadithiophene (CPDT) and the bithiophene ( EHex‐CPDT‐T2 ). The highest hole mobility of thin film transistor devices fabricated with new p‐type polymer semiconductors, Oct‐CPDT‐Se2 , was 1.3 × 10^?3 cm²/Vs with an on/off ratio of about 10⁵. The maximum power conversion efficiency of polymer solar cell fabricated with the blend of EHex‐CPDT‐Se2 /C₇₁‐PCBM reached 1.86% with an open circuit voltage (V_OC) of 0.55 V, a short circuit current density (J_sc) of 7.27 mA/cm², and a fill factor (FF) of 0.47 under AM 1.5G irradiation (100 mW/cm²). © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2009     

An Optical Approach for Drug Screening Based on Light‐Harvesting Conjugated Polyelectrolytes

Drugs turn the light off : Conjugated polyelectrolytes (CPEs) have been used in fluorescent assays for real‐time screening of small molecules that prevent the RNA–protein complexation that is important for virus replication and thereby can be considered potential initial candidates for drug discovery (see picture).