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Chiral Polythiophenes
No full textPolythiophenes (PT) belong to the class of Conducting organic polymers and Conducting organic polymers that possess chirality present some unique opportunities when used as chiral substrates or as chiral electrode materials.
The properties of chiral conducting PT can be tunable modifying the functional groups to the polymer backbone) and since these polymers can be formed as particles, membranes or micro- and nanodimensional fibers ,it is possible to design and to develop specific molecular systems for molecular recognition. The chiroptical properties of CCP films were studied under different evaporation conditions. The chiral recognition abilities of CCP are reported and also a new application in the field of spin filter
Polymers with Alkylsulfanyl Side Chains for Bulk Heterojunction Solar Cells: Toward a Greener Strategy
No full textThe synthesis and properties of three co-polymers obtained through a Knoevenagel poly-condensation are reported. They are soluble in organic solvents, filmable and solvatochromic. They are characterized through GPC, NMR and UV-visible spectroscopies, CV, and AFM. They display some proneness to form π-stacks, broad absorptions up to about 700 nm, HOMO and LUMO energies that fit those of [60]PCBM. The polymers are incorporated in blends with PCBM within BHJ devices. The best results are found for PSCs obtained from P1 (2.7 % PCE). The insertion of alkylsulfanyl chains improves the photovoltaic performances, with respect to those of alkyl-substituted analogous polymers. The Jsc of the devices are greatly enhanced, supporting the employment of (alkylsulfanyl)thienyl units as base units in photoactive materials
CONJUGATED POLYMERS FOR PHOTOVOLTAICS: FROM SOLUTION TO SOLID-STATE NMR
No full textConjugated polymers are widely studied for applications in organic electronics.[1] The structural scenery is varied and the properties of polymers and copolymers can change heavily with the structure. The characterization of organic polymers used in organic electronics, and in particular in polymer solar cells (PSCs), is strongly multidisciplinary. It requires expertise within different branches of chemistry and at the border among chemistry, physics and engineering.
Here, the contribution of solution NMR to the study of self-aggregation properties of thiophene based conjugated polymers will be presented. NMR findings on polymers in solution appear to be correlated to morphological properties and solvatochromism. Since one of the most actively investigated application of conjugated polymers is as donors in bulk hetero junction PSCs, also some results obtained with solid-state NMR on polymer/fullerene blends will be reported
π-Stacking signature in nmr solution spectra of thiophene-based conjugated polymers
No full textStudies on conjugated polymers seldom report on their NMR characterization in solution. This paper shows how NMR experiments, both 1H NMR and routine 2D NMR spectra, can help in gaining a further insight into the aggregation behavior of conjugated polymers and could be used to flank the more employed solid-state NMR and other spectroscopy and microscopy techniques in the understanding of the aggregation processes. NMR spectroscopy allows distinguishing, within the class of poorly solvatochromic conjugated polymers, those highly prone to form π-stacked aggregates from the ones that have a low tendency toward π-stacking
Aggregation Properties of Aminoalkylsulfanyl Polythiophenes
No full textThe aggregation properties of an aminoalkylsulfanyl polythiophenes cayying a tromethylammonium group were characterized through a combined AFM, DOSY NMR and DLS study
Poly(Cyanovinylene Phenylene-Co-Thiophene)s For Polymer Solar Cells
No full textWe synthetized, using a Knoevenagel polycondensation reaction, three different poly(phenylenecyanovinylene-co-thiophenes) , slightly changing the structure of the thiophene comonomer, to study the effect that these changes can have on the efficiency of photovoltaic devices built using these polymer
Zinc promoted addition of methyl 2,2-dihalocarboxylates to carbonyl compounds
No full textMethyl 2,2-dihalocarboxylates add easily to carbonyl compounds in fair to good yields through the intermediate formation of 2-haloester enolates; the reaction is promoted by zinc, following a ''Barbier'' type procedure
1,2-reduction of alpha,beta-unsaturated hydrazones using dimethylamine-borane/p-toluenesulfonic acid: an easy route to allyl hydrazines
No full textalpha,beta-Unsaturated hydrazones can be easily converted into N-allyl hydrazines by reaction with dimethylamine-borane/p-toluenesulfonic acid under mild reaction conditions. The reduction works well for N'-allyhydrazides but N'-allyl-N,N-dimethylhydrazines are rapidly reoxidised by air and so need to be manipulated under an inert atmosphere prior to M-acylation. Competitive conjugate reduction can also be observed and the regioselectivity of the dimethylamine-borane attack is determined by steric and/or electronic factors. The procedure is also effective for the C=N reduction of unconjugated hydrazones. (C) 2002 Elsevier Science Ltd. All rights reserved
Telechelic oligomers by halogen atom transfer radical addition
No full textMonodispersed telechelic oligomers have been efficiently prepared by Fe-0-FeCl3 promoted halogen atom transfer radical of functional telogens and taxogens, (C) 1998 Elsevier Science Ltd. All rights reserved
Synthesis Of Low Band-Gap Conjugated Polymers For Application In Solar Cells
No full textPolymer solar cells are a fascinating low cost alternative to silicon-based solar cells1 thanks to light weight, mechanical flexibility and processability. The polymers suitable for this purpose should possess good filming and absorption properties (absorption coefficients >105 cm-1 and UV–Vis spectrum ideally matching the solar spectrum)2, high hole mobility, and HOMO–LUMO energy levels suitable to be coupled with the acceptor species3. In this presentation the synthesis of three different low band gap copolymers is reported and discussed. The properties of these materials are compared in order to gain an insight on the molecular structure-performance relationship of the final devic
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