Carbazole-based Polymers Research Articles

Photophysics and Solvent-Induced Aggregation of 2,7-Carbazole-Based Conjugated Polymers

We report on the optical, photophysical, and solvatochromic properties of five carbazole-based polymers, namely poly(N-octyl-2,7-carbazolediyl) (POC), poly(N-(2‘-ethylhexyl)-2,7-carbazolediyl) (PEHC), poly(N-octyl-2,7-carbazolediyl-alt-2,5-thiophene) (POCT), poly(N-(2‘-ethylhexyl)-2,7-carbazolediyl-alt-2,5-thiophene) (PEHCT), and poly(N-octyl-2,7-carbazoleneethynylene) (POCE). Compared to their corresponding triads, the absorption and fluorescence spectra of polycarbazoles in chloroform are red-shifted due to an increase of the effective conjugation length. Among the polycarbazoles investigated, the optical spectra of POCT are the more red-shifted due to the electron donor properties of the thiophene rings. The variation of the photophysical properties of the polycarbazoles mainly involves radiative processes (kF). From steady-state and time-resolved fluorescence studies in chloroform/methanol mixtures, all polymers have revealed solvatochromic effects, which have been related to the formation of H- and/or J-aggregates. On one hand, the aggregation process found on homopolymers (POC and PEHC) and copolymers involving thiophene units (POCT and PEHCT) is accompanied by a strong quenching of the photoluminescence efficiency. On the other hand, for POCE, the molecular interactions between the polymeric chains are not strong enough to induce a deactivation of the fluorescence. Finally, it is observed that the nature of alkyl chains on the nitrogen atoms of the carbazole moieties has a significant effect on the emission properties of the polymers.

A postfunctionalization strategy to develop carbazole-based photorefractive polymers with low Tg

Carbazole-based polymers bearing methine groups with low glass transition temperature ( T g) for photorefractive purpose were prepared via postfunctionalization strategy. The successful reaction was identified by spectroscopic analysis and gel permeation chromatography. This approach is more facile compared with the direct polymerization from corresponding functional monomer. Chromophore content of the resulting polymers varied from 25% to 63% depending on the type of chromophore as calculated from 1H NMR spectra. Molecular weight of the polymers are higher than 2.4 × 10 5, and the polymers are easily soluble in common organic solvents like DMF and THF. T g of the polymers ranges from 40 to 58 °C depending on the structure of chromophore, and the polymers are relatively stable under 310 °C.

New carbazole-based polymers for dye solar cells with hole-conducting polymer

New carbazole-based polymers for use in dye-sensitized solar cells with p-conducting polymers have been synthesized. Further, a ruthenium-complex has been prepared to serve as electron/hole injecting dye in these cells. The energy gap has been determined by absorption and luminescence measurements of these materials in selected organic solvents. Cyclic voltammetry measurements have been performed to determine the energy level of the highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO). The energy levels of the polymers have been compared with the ones of a ruthenium-complex dye to check if a combination of these materials could make a promising couple in dye solar cells (DSC) with a hole-conducting polymer. Additionally, a combination of the new synthesized material with a commercial dye, cis-(NCS) 2bis(4,4′-dicarboxy-2,2′-bipyridine)-ruthenium(II), in its two-fold deprotonated form “N719” and a polymer, poly(3-octylthiophene) (P3OT), has been investigated.

FIB-SIMS investigation of carbazole-based polymer and copolymers electrocoated onto carbon fibers, and an AFM morphological study

The work presented in this paper reports preliminary results obtained by focused ion beam-secondary ion mass spectroscopy (FIB-SIMS) analysis in the study of micro-sized carbon fiber electrocoated by conjugated-nonconjugated polymers such as poly( N-vinylcarbazole-co-methylthiophene), poly( N-vinylcarbazole-co-vinylbenzene sulfonic acid) and polycarbazole. The aim of this study was to investigate by FIB-SIMS analysis the presence and concentration gradient of certain elements via depth profiling of the coating on selected carbon fibers. The presence of dopant ions together with their gradient of concentration in the coating layer was elucidated as well as the thickness of the copolymer layer electrocoated onto the carbon surface. AFM analysis performed on the electrocoated fibers yielded information regarding the surface morphology and roughness.

Carbazole-based azo group-containing single component polymer exhibiting photorefractive performance

Photorefractive (PR) polymers have been investigated widely mostly with host–guest polymer composites [1, 2] and fully functionalized polymers [3, 4]. Host– guest polymer composites exhibit poor stability due to phase separation, while fully functionalized polymers are difficult to be synthesized in most cases. Therefore, much effort has been paid in constructing bifunctional polymers with both photoconductivity and electro-optic (EO) effect for photorefractive purpose in recent years. Such bi-functional photorefractive polymers may have good stability against phase separation and be much easier to synthesize; the minor composition of photo-sensitizer may be incorporated in a composite manner. In constructing the bi-functional photorefractive polymers, carbazole-based polymers have attracted considerable attention, which is because of the fact that polyvinylcarbazole (PVK) based host–guest polymers have been realized to exhibit high EO response and good photorefractive performance. But the high glass transition temperature (Tg) of PVK made it difficult to pole at room temperature to achieve orientational birefringence. Lowering the Tg by adding plasticizer normally resulted in the deduction of photorefractive performance due to the relative lowering of chromophore concentration. On the other hand, the direct polymerization of a functionalized carbazole monomer normally gives a polymer with low molecular weight owing to both the bulkiness of the monomer and the side effect of the functional group, which is not beneficial to the film forming property of the polymer. In our effort to synthesize carbazole-based azo group-containing bi-functional photorefractive polymer with low Tg through a post-azo-coupling reaction, we surprisingly found that the single component polymer exhibits good PR performance at room temperature without adding any sensitizer and plasticizer. The polymer synthesis is shown in Scheme 1; a precursor polymer bearing carbazole group with a long alkylene chain was prepared through conventional free radical polymerization; then the precursor polymer was allowed to react with diazonium salt in nitrobenzene with the help

Multiply Colored Electrochromic Carbazole-Based Polymers

We report the synthesis and electrochemical polymerization of a series of bisheterocycle-N-substituted carbazoles. These monomers exhibit low peak oxidation potentials (Ep,m) which range from 0.15 to 0.46 V vs Ag/Ag+, indicating facile polymerization. Repeated scan electrochemical polymerization for these monomers proceeds rapidly, relative to carbazole, to form stable electroactive films. Cyclic voltammetry of the polymers indicates that the films are well adhered to the electrode surface and that each of the polymers possess two distinct redox waves. At applied potentials greater than 1.15 V, a third irreversible oxidative process is observed, presumedly due to cross-linking. Optoelectrochemical analysis indicates that these polymers have an electronic bandgap (measured as the onset of the π-to-π* transition) between 2.4 and 2.5 eV. Three distinct colors are achievable by varying the redox state of the polymers suggesting potential use for multiply colored electrochromic displays. For the series of bis(...

Muticoloured electrochromic polymers derived from easily oxidized bis[2-(3,4-ethylenedioxy)thienyl]carbazoles

Two bis[2-(3,4-ethylenedioxy)thienyl]carbazole-based polymers are synthesized by the electropolymerization of highly conjugated, low-oxidation potential monomers; these polymers exhibit multicolour electrochromic behaviour, each possessing three separate accessible states.

Recent Advances in Photoconductive and Photosensitive Polymers

Abstract The synthesis and evaluation of photoconductive and photosensitive polymers have received considerable attention during recent years because of the increasing demand for such materials in electrophotography and related processes. By now, a wide variety of polymers, unmodified as well as modified chemically or otherwise, has been explored with regard to their potentialities in this field. An authoritative review by Stolka and Pai discussed the basic concepts in photoconductivity, summarizing the experimental techniques commonly employed in this context along with a review of original and patent literature on these systems available through 1976. In a contemporary article, Pen-well, Ganguly, and Smith reviewed the literature on N-vinyl -carbazole polymer systems with specific regard to synthesis, physicochemical property evaluation vis-a-vis their theoretical implications, and related topics. More recently, Biswas and Das reviewed the developments in carbazole-based polymer systems throusrh 1979.

Electron paramagnetic resonance in irradiated carbazole-based polymers

Electron paramagnetic resonance in irradiated carbazole-based polymers