Polythiophenes with Carbazole Side Chains: Design,Synthesis and Their Application in Organic Solar Cells

A series of polythiophene derivatives P1‐P5 containing carbazole side chains were designed and synthesized via the Stille polymerization. All carbazole containing polymers showed broad absorption in the visible region. The power conversion efficiencies of solar cells based on blends of two component copolymers and [6,6]‐phenyl‐C₆₁‐butyric acid methyl ester (PC₆₁BM) were determined to be 0.29 and 0.56% for P1 and P5 , respectively. For solar cells fabricated with the three component copolymers and PC₆₁BM, the efficiencies were 0.56% for P2 , 0.86% for P3 , and 0.70% for P4 . The introduction of electron‐donating carbazole side chains can broaden the absorption in the visible region and meanwhile reduce phase separation due to the steric hinderance of the carbazole moiety to the conjugated main chain. Improving efficiency needs a balance of broad absorption and ordered packing of polymer chains in the solid state.

     

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).

     

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.

     

Direct Sub‐Micrometer‐Patterning of Conjugated Polymers and Polymer Light‐Emitting Devices by Electron Beam Lithography

The lateral pattering of polymer light emitting devices (PLEDs) on the micro‐ and even sub‐micrometer level is a challenging task. Being able to fabricate devices with sub‐micrometer active device dimensions will, however, open new possibilities for fundamental studies as well as enable improvements in device performance. Therefore, in this study an electron beam‐based patterning method for conjugated polymers is evaluated, where the structuring is achieved by deliberate degradation and alteration of the molecular structure accompanied by a change in the emission properties. We find that the typical feature size accomplished with this method is approx. 2 µm for the active line width in PLEDs, while the in‐depth investigation of the structures shows that the lateral resolution is found to be approx. 500 nm.

     

Xanthene‐Based Oligothiophene‐Layered Polymers

We synthesized xanthene‐based oligothiophene‐layered polymers containing bithiophenes, terthiophenes, quaterthiophenes and quinquethiophenes by the Suzuki‐Miyaura coupling reaction. The polymers were characterized by various spectroscopic and electrochemical methods. They were well soluble in common organic solvents and thermally stable. Effective π‐π interactions among the layered oligothiophene units in the polymer backbone were not observed in the ground state as well as in the excited state. A possible application of the polymers in opto‐electronic devices such as hole transporting materials is expected.

     

Syntheses of New 3,6‐Carbazole‐Based Donor/Acceptor Conjugated Copolymers for Optoelectronic Device Applications

The syntheses, properties, and optoelectronic device characteristics of four new 3,6‐carbazole‐based donor/acceptor conjugated copolymers are reported. Such copolymers are used to explore the effects of acceptor strength and backbone coplanarity on the electronic and optoelectronic properties. The optical bandgaps of the studied copolymers are PCzQ (2.29 eV) > PCzDTQ (1.91 eV) > PCzTP (1.75 eV) > PCzDTTP (1.49 eV), which are much smaller than the parent poly(3,6‐carbazole). The power conversion efficiency of the photovoltaic cells fabricated from blends of copolymer/PC₆₁BM or PC₇₁BM reached 1.01 and 1.73% by varying the film thickness or blend ratio. The experimental results suggest the potential application of 3,6‐carbazole acceptor conjugated copolymers in optoelectronic devices.

     

Diphenylacetylene Polymer Nanofiber Mats Fabricated by Freeze Drying: Preparation and Application for Explosive Sensors

Finely structured diphenylacetylene polymer nanofibers were successfully prepared by a freeze drying method. SEM revealed that the morphology and structure of the fibers were significantly dependent on the concentration of the polymer solution, the ‘frozen in’ quenching temperature and the chemical structure of the polymer derivatives. Polarized fluorescence spectroscopy revealed that the polymer chains within the nanofiber were uniaxially oriented and highly elongated. The polymer nanofiber was remarkably sensitive to explosive nitroaromatic compounds when compared to the corresponding thin films. The fluorescence of polymer nanofiber obtained from 0.003 wt.‐% cryogenic benzene solution rapidly decreased to 50% of its initial value in ≈35 s by exposing to 2,4‐dinitrotoluene.

     

Plastic Transmissive Infrared Electrochromic Devices

Poly(3‐hexyl thiophene) was used to build a thin‐layer, electrically switchable infrared shutter. Electrochromic materials are typically studied in the visible, whereas we focused on P3HT electrochromic behavior in the infrared where morphology changes may have greater impact. Devices were fabricated on ITO‐coated silicon and germanium and their performance was characterized in the mid infrared (2–6 µm). Thicker polymer films increased device switching time and did not improve optical contrast. Choice of salt in the electrolyte significantly affects switching dynamics and salt concentrations affect maximum optical contrast. These results are potentially important for the integration of polymer technology into infrared imaging and detection applications.

     

A high intake of conjugated linoleic acid does not affect liver and kidney function tests in healthy human subjects

Conjugated linoleic acid (CLA) is consumed widely as a supplement. It causes hepatomegaly in animals, but toxicological data in humans are limited. We therefore studied the effect of a high daily intake of CLA on liver and kidney function in healthy subjects. Twenty subjects received 14.6 g cis-9,trans-11 CLA and 4.7 g trans-10,cis-12 CLA isomers a day for 3 weeks. Liver and kidney function was measured at 0, 3, 7, 10, 16, and 21 days. Mean values of all tests remained within normal limits. Lactate dehydrogenase (mean ± SD) increased from 290.9 ± 43.6 to 322.5 ± 60.7 U/L (p = 0.04) on day 21. One subject exceeded the upper limit of normal of 450 U/L on day 21, to 472 U/L and another showed an isolated elevation to 555 U/L on day 7. γ-Glutamyltranspeptidase increased from 12.1 ± 5.9 to 13.5 ± 6.2 U/L (p = 0.002). No one exceeded the upper limit of 50 U/L for men and 40 U/L for women. A daily intake of 19.3 g CLA for 3 weeks does not produce clinically relevant effects on markers of liver and kidney function in healthy volunteers.     

TESTICULAR GAMETOGENIC AND STEROIDOGENIC ACTIVITIES IN CYCLOPHOSPHAMIDE TREATED RAT: A CORRELATIVE STUDY WITH TESTICULAR OXIDATIVE STRESS

ABSTRACT

The present work examined the changes in testicular activities in relation to testicular oxidative stress in cyclophosphamide as well as human chorionic gonadotrophin (hCG) co-treated cyclophosphamide treated Wistar strain rats. Testicular activities were evaluated by the quantification of spermatogenesis and by the measurement of steroidogenic key enzyme activities along with plasma levels of testosterone. Testicular oxidative stress in relation to cyclophosphamide treatment was monitored by the study of products of free radicals like conjugated dienes and malondialdehyde (MDA) as well as the activity of testicular antioxidant enzymes like peroxidase and catalase. Cyclophosphamide treatment at the dose of 5 mg/kg body weight/day for 28 days resulted a significant diminution in the activities of testicular Δ⁵, 3β-hydroxysteroid dehydrogenase (Δ⁵, 3β-HSD), 17β-hydroxysteroid dehydrogenase (17β-HSD) activities, plasma level of testosterone along with significant reduction in the number of germ cells at stage-VII of spermatogenesis. Levels of testicular MDA and conjugated dienes both were elevated whereas testicular peroxidase and catalase activities both were inhibited significantly in cyclophosphamide treated rats in comparison to control. After hCG co-administration at the dose of 5 I.U./kg body weight/day for 28 days in cyclophosphamide treated rats resulted a significant protection in the activities of testicular peroxidase and catalase along with significant decrease in the levels of MDA and conjugated dienes to the control level. Moreover, the testicular steroidogenic key enzyme activities and spermatogenesis along with plasma levels of testosterone were restored to the control level. Therefore, it may be concluded that there is a correlation between testicular steroidogenic activities as well as spermatogenesis and testicular oxidative stress in cyclophosphamide treated rats. Moreover, as restoration of plasma testosterone to the control level is noted in hCG co-treated cyclophosphamide treated rat, therefore, the results suggest that testosterone may be the key regulator for this correlation.