We present absorption and photoluminescence features of four samples of carbazole molecules substituted with various electron–acceptor groups. These molecules named 1-(N-ethylcarbazolyl)-2-substituted-2-cyanovinylene contain in their structure the electron–donor carbazole nucleus and cyanovinylene bearing either another nitrile function, an ethylester, a phenyl, or a para-nitrophenyl groups. It is shown that depending on the strength of the donor–acceptor internal charge transfer, both the absorption and emission spectra are more or less redshifted. It is found that the ethyl-ester derivative displays the best relative photoluminescence efficiency among all the samples and its peak is measured at 490 nm when taking amorphous thin film. The microcrystalline powder form of the same material exhibits spectral narrowing and shift of the peak emission. We obtain further narrowing of the emission band and further redshifting of the emission when we illuminate, transversely, a glass capillary containing the crystalline sample by an ultraviolet light-emitting diode.

A conjugated alternating copolymer, poly[bicarbazolylene-alt-phenylenebis(eyanovinylene)] (named PCPV), was prepared via the Knoevenagel condensation in the presence of tetrabutylammonium hydroxide. Tetrahydrofuran-soluble low molecular weight materials and insoluble polymer were obtained. The two fractions were characterized in detail by ESR and solid and solution NMR spectroscopies. Strong ESR signals were observed from the pristine PCPV polymer in both fractions. This was explained by the rotational cleavage of the cis vinylic bond to produce two r radicals, called biradicals, which diffuse along the main chains to form radical cations stabilized by conjugation in the alternating repeating moieties. In particular, the insoluble fraction shows an extremely strong and sharp line width signal with a spin concentration equal to 5.8 x 10(17) spins/g. The alternating copolymer synthesized can be considered as a novel conjugated material analogous to substituted polyacetylenes with respect to the mobile unpaired electrons. The solid NMR spectrum of the insoluble fraction of the PCPV copolymer is reported for the first time. By comparison with solution NMR studies of the soluble fraction and of a model compound of the repeating unit, the structure of the copolymer was established. The H-1 NMR spectrum of the soluble fraction allowed calculation of the DPn whose values roughly agree with that estimated by SEC measurements. However, the NMR signals of the soluble fraction were somewhat broadened because of the presence of unpaired electrons in the main chains.

ADVERTISEMENT RETURN TO ISSUEPREVCommunication to the...Communication to the EditorNEXTA Soluble Green-Light-Emitting Alternating Copolymer with Acceptor-Substituted Bicarbazyl UnitsV. Boucard, D. Adès, A. Siove, D. Romero, M. Schaer, and L. ZuppiroliView Author Information Laboratory of Macromolecular Research (CNRS), Galilee Institute, University of Paris-Nord, 93430 Villetaneuse, France Physics Department, Swiss Federal Institute of Technology, CH-1015, Lausanne, Switzerland Cite this: Macromolecules 1999, 32, 14, 4729–4731Publication Date (Web):June 17, 1999Publication History Received10 December 1998Revised22 April 1999Published online17 June 1999Published inissue 1 July 1999https://pubs.acs.org/doi/10.1021/ma981909thttps://doi.org/10.1021/ma981909trapid-communicationACS PublicationsCopyright © 1999 American Chemical SocietyRequest reuse permissionsArticle Views255Altmetric-Citations22LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InRedditEmail Other access optionsGet e-Alertsclose SUBJECTS:Alcohols,Condensation,Diodes,Layers,Polymers Get e-Alerts

Les conditions dans lesquelles des copolymères statistiques (carbazo lylène-pyrrolylène) pouvaient être synthétisés directement par oxydation chimique par FeCl3 ont été étudiées. Des quantités substantielles de copolymères solubles en milieu organique sont obtenues par extraction lorsque les proportions molaires en réactifs carbazole/pyrrole/2 FeCl3 sont utilisées. Une fraction importante de polypyrrole est obtenue à côté d'une fraction d'espèces solubles dans l'éthanol (carbazole et son dimère) et d'une fraction de produits solubles dans l'eau (pyrrole et les premiers termes oligomères). Les copolymères solubles ont été caractérisés par CES, spectroscopies RMN et UV-Visible. L'analyse voltampérométrique de ces matériaux révèle qu'ils possèdent à la fois les caractéristiques des entités carbazolylènes et celles des entités pyrrolylènes.

Conditions in which (carbazolylene-pyrrolylene) random copolymers could be synthetized directly by chemical oxidation by FeCl3 were studied. A substantial amount of soluble copolymers is obtained after work-up in the conditions corresponding to carbazole/pyrrole/2 FeCl3 molar proportions. An important fraction of polypyrrole was obtained beside a fraction of species soluble in ethanol (carbazole and dimer) and an other fraction of products soluble in water (pyrrole accompanied by the first terms of the oligomeric series). Soluble copolymers were characterized by means of SEC, NMR and W-Visible spectroscopies. Cyclic voltammetry analysis disclosed that these copolymers exhibit both the carbazolic and the pyrrolic features.

The Knoevenagel condensation has been applied to the synthesis of ([bicarbazolylene]-alt-[phenylenebis(cyanovinylene)]) copolymers. These materials are mostly insoluble in organic solvents but, depending an the reaction conditions a small amount of soluble oligomers could be obtained. The alternation of electron-donor carbazolylene units and electron-withdrawing phenylene-cyanavinylene entities is believed to be partly responsible for the rigidity of the macromolecular chains, so explaining their insolubility. Moreover, this regular alternation of donor-acceptor moieties is thought to be responsible for the lowering of the bandgap of the soluble oligomers and for decreasing the stability of the bicarbazolylium radical-cations of the doped state. Lastly, materials were fairly resistant to thermal degradation, up to 450 degrees C. (C) 1997 Elsevier Science Ltd.

Stereospecificity and enantioasymmetry of living polymerization of methylthiirane initiated by various bis(alkyl-S-cysteinato)cadmium are studied. Whatever the alkyl group structure R used, we always observe the same general feature for this living polymerization. Two types of chiral sites C-R(*) and C-S(*) are present leading to an isotactic polymer. The preferential incorporation of the R enantiomer implies that active sites may be present in different amounts and/or with different reactivities. Isomeric relationship between the two types of active sites is depending on the <(Mn)over bar> of the growing chain bearing them and two separate stages are observed. In the first step, when the two types of active sites are diastereoisomers (for <(Mn)over bar> of the growing chain bearing the active sites contained between 6000 and 35000) we observe an effect of R on the enantioasymmetry. Stiff alkyl groups lead to relatively high enantioasymmetric constants whereas for long chains (2-octyl), the enantioasymmetry practically disappears.In the second step, when the molar weight of the growing chain bearing the active sites is higher than 35000, the enantioasymmetry polymerization run on the enantiomeric form of active sites does not depend on the alkyl group.