Showing papers in "Macromolecular Rapid Communications in 2005"
TL;DR: In this paper, the effective conjugation length of poly(2,7-carbazole) and poly(p-phenylene)-like structure is compared to poly(3,6-carbazole).
Abstract: Summary: Carbazole-based oligomeric and polymeric materials have been studied for almost 25 years for their unique electrical, electrochemical and optical properties. Interestingly, carbazole units can be linked in two different ways leading to either poly(3,6-carbazole) or poly(2,7-carbazole) derivatives. While the former class seems to be very interesting for electrochemical and phosphorescence applications, the latter shows very promising optical properties in the visible range for light emitting diodes (LED). The major intrinsic difference between these two classes is the effective conjugation length: poly(2,7-carbazole) materials having the longer one, due to their poly(p-phenylene)-like structure. Using different synthetic strategies and substitution patterns, the physico-chemical properties of both classes can be fine-tuned, leading to high performance materials for a large number electronic applications.
Chemical structures for poly(3,6-carbazole) and poly(2,7-carbazole) and the materials used as the starting points for their respective syntheses.
591 citations
TL;DR: In this paper, Electroactive shape-memory composites were synthesized using conducting polyurethane (PU) composites and multi-walled carbon nanotubes (MWNTs) surface modification of the MWNTs by acid treatment improved the mechanical properties of the composites.
Abstract: Summary: Electro-active shape-memory composites were synthesized using conducting polyurethane (PU) composites and multi-walled carbon nanotubes (MWNTs) Surface modification of the MWNTs (by acid treatment) improved the mechanical properties of the composites The modulus and stress at 100% elongation increased with increasing surface-modified MWNT content, while elongation at break decreased MWNT surface modification also resulted in a decrease in the electrical conductivity of the composites, however, as the surface modified MWNT content increased the conductivity increased (an order of 10−3 S · cm−1 was obtained in samples with 5 wt-% modified-MWNT content) Electro-active shape recovery was observed for the surface-modified MWNT composites with an energy conversion efficiency of 104% Hence, PU-MWNT composites may prove promising candidates for use as smart actuators
The electro-active shape-recovery behavior of PU-MWNT composites The pictured transition occurs within 10 s when a constant voltage of 40 V is applied
560 citations
TL;DR: It is demonstrated that PET, which is usually regarded as ‘non-biodegradable’, can effectively be depolymerized by a hydrolase from the actinomycete Thermobifida fusca.
Abstract: Summary: It is demonstrated that PET, which is usually regarded as ‘non-biodegradable’, can effectively be depolymerized by a hydrolase from the actinomycete Thermobifida fusca. Erosion rates of 8 to 17 µm per week were obtained upon incubation at 55 °C. Lipases from Pseudomonas sp. and Candida antarctica did not degrade PET under comparable conditions. The influences of crystallinity, melting point, and glass transition temperature on the enzymatic attack on PET, PBT, and PHB are discussed.
Outline of the degradation of PET.
355 citations
TL;DR: In this paper, a rough polydimethylsiloxane (PDMS) surface containing micro-, sub-micro-, and nano-composite structures was fabricated using a facile one-step laser etching method.
Abstract: Summary: Rough polydimethylsiloxane (PDMS) surface containing micro-, submicro- and nano-composite structures was fabricated using a facile one-step laser etching method. Such surface shows a super-hydrophobic character with contact angle higher than 160° and sliding angle lower than 5°, i.e. self-cleaning effect like lotus leaf. The wettabilities of the rough PDMS surfaces can be tunable by simply controlling the size of etched microstructures. The adhesive force between etched PDMS surface and water droplet is evaluated, and the structure effect is deduced by comparing it with those own a single nano- or micro-scale structures. This super-hydrophobic PDMS surface can be widely applied to many areas such as liquid transportation without loss, and micro-pump (creating pushing-force) needless micro-fluidic devices.
Etched PDMS surface containing micro-, submicro-, and nano-composite structures shows a self-cleaning effect with water CA as high as 162° and SA lower than 5°.
355 citations
TL;DR: In this article, a drop-on-demand ink-jet printer was used to print a silver-organic solution onto glass substrates and conductive silver tracks were obtained by heat treatment of the inkjet printed deposits at temperatures ranging from 125°C to 200°C in air.
Abstract: Summary: A drop-on-demand ink-jet printer has been used to print a silver-organic solution onto glass substrates. Conductive silver tracks were obtained by heat treatment of the ink-jet printed deposits at temperatures ranging from 125 °C–200 °C in air. Resistivity values were found to have dropped to two to three times the theoretical resisitivity of bulk silver after temperatures of 150 °C and above were used.
Resistivity values of a silver-based ink.
317 citations
TL;DR: In this paper, the bromine chain ends of polystyrene were successfully transformed into various functional end groups (ω-hydroxy, ω-carboxyl and ω -methyl-vinyl) by a two-step pathway: (1) substitution of the brome terminal atom by an azide function and (2) 1,3-dipolar cycloaddition of the terminal azide and functional alkynes (propargyl alcohol, propiolic acid and 2-methyl-1-buten-3-yne).
Abstract: Summary: The bromine chain ends of well-defined polystyrene ( = 2 700 g · mol−1, = 1.11) prepared using ATRP were successfully transformed into various functional end groups (ω-hydroxy, ω-carboxyl and ω-methyl-vinyl) by a two-step pathway: (1) substitution of the bromine terminal atom by an azide function and (2) 1,3-dipolar cycloaddition of the terminal azide and functional alkynes (propargyl alcohol, propiolic acid and 2-methyl-1-buten-3-yne). The “click” cycloaddition was catalyzed efficiently by the system copper bromide/4,4′-di-(5-nonyl)-2,2′-bipyridine. In all cases, 1H NMR spectra indicated quantitative transformation of the chain ends of polystyrene into the desired function.
Preparation of well-defined functional polymers possessing diverse chain-end functionalities by the combination of atom transfer radical polymerization and click chemistry.
286 citations
TL;DR: In this paper, a polypyrrole nanotubes with high electric conductivity and azo function have been fabricated in high yield via an in-situ polymerization.
Abstract: Summary: Polypyrrole nanotubes with high electric conductivity and azo function have been fabricated in high yield via an in-situ polymerization. During the process fibrillar complex of FeCl3 and methyl orange (MO), acting as a reactive self-degraded template, directed the growth of polypyrrole on its surface and promoted the assembly into hollow nanotubular structures.
TEM image of uncompleted PPy nanotubes synthesized in MO solutions after reaction for 40 min.
286 citations
TL;DR: In this paper, a polyurethane network containing polyamide polyhedral oligomeric silsesquioxane (OapPOSS) was used as a crosslinking agent together with 4,4-methylenebis-(2-chloroaniline) to obtain enhanced glass transition temperatures.
Abstract: Octaaminophenyl polyhedral oligomeric silsesquioxane (OapPOSS) was used as a crosslinking agent together with 4,4-methylenebis-(2-chloroaniline) to prepare polyurethane networks containing POSS. Fourier transform infrared spectroscopy (FT-IR), dynamic mechanical analysis (DMA) and thermogravimetric analysis (TGA) were employed to characterize the POSS-reinforced polyurethane. The POSS-containing PU networks displayed enhanced glass transition temperatures (Tgs) and the storage moduli of the networks of the glassy state and rubber plateaus were also observed to be significantly higher than that of the control polyurethane although only a small amount of POSS was incorporated into the systems. The results can be ascribed to the significant nanoscale reinforcement effect of POSS cages on the polyurethane matrix. TGA results showed the thermal stability was also improved with incorporation of POSS into the system.
221 citations
TL;DR: In this article, the authors present a method for printing circuits on a flexible substrate by combining self-assembled polyelectrolytes, ink-jet printing of a catalyst, and electroless plating of metals.
Abstract: The driving forces behind the development of flexible electronics are their flexibility, lightweightedness, and potential for low-cost manufacturing. However, because of physical locations, traditional thermal processes cause deformations in the flexible substrate. As a result, the adhesion quality of the printed wires is deteriorated. This article reviews recent developments in printing circuits on a flexible substrate by combining self-assembled polyelectrolytes, ink-jet printing of a catalyst, and electroless plating of metals. The limitations and potential applications of this technology are also discussed. Experiments implementing this technology demonstrated significant results. By a vibration-induced assistance during an ink-jet printing catalyst process, line width and blurring can be controlled to within ′3% variation. Following the IPC 6013 standard for flexible electronics, the results after thermal cycling (288 °C, 6 times) and a hot oil test (260 °C, 3 times) indicated that the metallic circuit had retained excellent adhesion properties and electric characteristics. We also report the first successful demonstration of a metal film in a via-hole inner wall on a flexible substrate. This novel fabrication method is ideal for the realization of large area, flexible electronics and furore multilayer flexible substrate Application, such as flexible display, chip on flexible substrate, etc. particularly where traditional lithographic processes can not be applied.
216 citations
TL;DR: Two types of ink-jet inks are presented: ink containing an aqueous dispersion of silver nanoparticles and an oil-in-water microemulsion-based ink as discussed by the authors.
Abstract: Two types of ink-jet inks are presented: ink containing an aqueous dispersion of silver nanoparticles and an oil-in-water microemulsion-based ink. The metallic ink contains nanoparticles of silver; which are formed in the presence of an ionic polymeric stabilizer. Sintering of the printed image obtained with the use of such silver-based inks at temperatures as low as 300 °C results in formation of patterns possessing noticeable conductivity. The microemulsion inks are based on a thermodynamically stable microemulsion, in which the dispersed oil phase is a volatile solvent containing a water-insoluble colorant. After contact of the jetted ink droplets with a substrate, nanodroplets of the microemulsion are converted into nanoparticles of the solubilized colorant. In some cases, it was found that the evaporation of microemulsion ink droplets leads to formation of rings composed of ordered nanoparticles.
205 citations
TL;DR: A superhydrophobic coating was facilely fabricated in one step by casting bisphenol A polycarbonate (PC) solution under moisture as discussed by the authors, and a rough surface with a micro-nano-binary structure (MNBS) similar to the microstructure shown on lotus leaf was formed.
Abstract: A superhydrophobic coating was facilely fabricated in one step by casting bisphenol A polycarbonate (PC) solution under moisture. Vapor-induced phase separation occurred during the solidifying process and a rough surface with a micro-nano-binary structure (MNBS) similar to the microstructure shown on lotus leaf was formed.
TL;DR: In this article, reversible addition fragmentation chain transfer (RAFT) polymerization of pentafluorophenyl methacrylate (PFMA) was carried out in the presence of cumyldithiobenzoate and 4-cyano-4-((thiobenzoyl)sulfanyl)pentanoic acid, respectively.
Abstract: Reversible addition fragmentation chain transfer (RAFT) polymerization of pentafluorophenyl methacrylate (PFMA) was carried out in the presence of cumyldithiobenzoate and 4-cyano-4-((thiobenzoyl)sulfanyl)pentanoic acid, respectively. These chain transfer agents with 2,2'-azoisobutyronitrile (AIBN) as initiator yielded the active ester polymer poly(PFMA) with M n up to 17000 g . mol -1 and low polydispersity index (M w /M n <1.2). Kinetic analysis using 19 F NMR spectroscopy and gel permeation chromatography (GPC) measurements showed controlled polymerization behavior for both chain transfer agents. Successful preparation of linear diblock copolymers consisting of an active ester block and methyl methacrylate, N-acryloylmorpholine, or N,N-diethylacrylamide, respectively, could be demonstrated. These polymers could easily react with amines in a polymer analogous reaction to form multifunctional polymers.
TL;DR: In this paper, the development of a novel technique for the preparation of homogeneous BaTiO 1 /polyvinylidene fluoride (BT/PVDF) nanocomposites without obvious agglomeration of BaTiOs 3 particles was reported.
Abstract: The development of a novel technique for the preparation of homogeneous BaTiO 1 /polyvinylidene fluoride (BT/PVDF) nanocomposites without obvious agglomeration of BaTiO 3 particles was reported in this communication. The morphology, structure, and frequency dependence of the dielectric properties of the nanocomposites were characterized. All results show that the dielectric properties of the nanocomposites in this study are desirable, and the process for preparing the nanocomposites has potential applications in the electronic industry.
TL;DR: In this article, N,N-Dimethylformamide was used as a solvent for the polyvinylpyrroiidone (PVP) and reducing agent for the Ag + ions in the PVP solutions.
Abstract: Poly(N-vinylpyrroiidone) (PVP) was used in two methods to prepare polymer nanofibers containing Ag nanoparticles. The first method involved electrospinning the PVP nanofibers containing Ag nanoparticles directly from the PVP solutions containing the Ag nanoparticles, N,N-Dimethylformamide was used as a solvent for the PVP as well as a reducing agent for the Ag + ions in the PVP solutions. In the second method, poly(vinyl alcohol) (PVA) aqueous solutions were electrospun with 5 wt.-% of the PVP containing Ag nanoparticles. The Ag; nanoparticles were evenly distributed in the PVA nanofibers. PVP containing Ag nanoparticles could be used to introduce Ag nanoparticles to other polymer nanofibers that are miscible with PVP.
TL;DR: The bis-hydrophilic block copolymer, poly(acrylic acid) 45 -black poly(N,N-diethylacrylamide) 360, was obtained after hydrolysis of poly(tert-butyl acrylate) 45-block-poly(N-N-decyclic acid) 360 in the presence of Et 3 Al as mentioned in this paper.
Abstract: The bis-hydrophilic block copolymer, poly(acrylic acid) 45 -black-poly(N,N-diethylacrylamide) 360 , was obtained after hydrolysis of poly(tert-butyl acrylate) 45 -block-poly(N,N-diethylacrylamide) 360 , synthesized by sequential anionic polymerization of tert-butyl acrylate (tBA) and N,N-diethylacrylamide (DEAAm) in the presence of Et 3 Al. The polymer is stimuli-sensitive with respect to both pH and temperature in aqueous solution, reversibly forming spherical crew-cut micelles with PDEAAm-core ( z = 21.5 nm) under alkaline conditions for T>35 °C as well as inverse star-like micelles with an expaned PAA-core ( z = 43.8 nm) under acidic conditions for T<35°C, as indicated by dynamic light scattering.
TL;DR: In this article, the diameter dependence of polystyrene-block-poly(methyl methacrylate) nanorods was systematically investigated by varying the pore diameters of the templates from 400 nm down to 25 nm.
Abstract: Polystyrene-block-poly(methyl methacrylate) nanorods were prepared by wetting ordered porous alumina templates. We systematically investigated the diameter-dependence of their morphologies by varying the pore diameters of the templates from 400 nm down to 25 nm. If the pore diameter exceeds the period of the block copolymer, the pores accommodate a non-integer number of repeal periods. In case of smaller pores the occurrence of an ordered state could not he unambiguously verified.
TL;DR: In this article, the effect of the initial interlayer spacing of the organoclay on the overall morphology and properties of an immiscible polycarbonate/poly(methyl methacrylate) blend was examined.
Abstract: This communication describes the effect of organic modifier miscibility with the matrices, and the effect of the initial interlayer spacing of the organoclay, on the overall morphology and properties of an immiscible polycarbonate/poly(methyl methacrylate) blend. By varying the organic-modifier-specific interactions with the blend matrices at the same time as changing the initial interlayer spacing of the organoclay, different levels of compatibilization were revealed. The evidence for the interfacial compatibilization of the organoclay was assessed by scanning electron microscopy observations and was supported by differential scanning calorimetry analyses. The effect on the level of clay exfoliation was also examined.
TL;DR: In this paper, a co-continuous structure of polyamide 6 (PA6)/acrylonitrile-butadiene-styrene (ABS) (40/60 w/w) nanocomposites with a novel morphology were prepared by the melt mixing of PA6, ABS and organoclay.
Abstract: Polyamide 6 (PA6)/acrylonitrile-butadiene-styrene (ABS) (40/60 w/w) nanocomposites with a novel morphology were prepared by the melt mixing of PA6, ABS and organoclay. The blend nanocomposites had a co-continuous structure, in which both PA6 and styrene-acrylonitrile (SAN) were continuous phases. It was found that the toughening rubber particles were only located in the SAN phase and the strengthening clay platelets were selectively dispersed in the PA6 phase. The co-continuous nanocomposites showed greatly improved mechanical properties over the whole temperature range when compared with the same blend sample without clay.
TL;DR: In this paper, a method to measure the Young's modulus of a single electrospun polyacrylonitrile (PAN) fiber is reported. But the method is based on the bending of the fiber attached to an atomic force microscopy (AFM) cantilever.
Abstract: A method to measure the Young's modulus of a single electrospun polyacrylonitrile (PAN) fiber is reported. The Young's modulus can be calculated from the force-displacement curves obtained by the bending of a single fiber attached to an atomic force microscopy (AFM) cantilever. It is suggested that the high modulus of electrospun fibers is caused by the orientation of molecular chains, which is confirmed by wide-angle X-ray diffraction (WAXD) measurements. The communication will provide a basic understanding of the relationship between mechanical properties and structures of electrospun fibers.
TL;DR: In this article, a new method for the preparation of polyaniline nanoballs by using HAuCl 4 as an oxidizing agent was reported, where aniline is oxidized and forms polyanILine whilst the hydrogen tetrachloroaurate is reduced and forms gold nanoparticles.
Abstract: We report a new method for the preparation of polyaniline nanoballs by using HAuCl 4 as an oxidizing agent. During the reaction, aniline is oxidized and forms polyaniline whilst the hydrogen tetrachloroaurate is reduced and forms gold nanoparticles. These gold nanoparticles are found to decorate the nanoballs.
TL;DR: In this paper, a core-sheath nanofibers with conductive polyaniline as the core and an insulating polymer as the sheath were prepared by electrospinning.
Abstract: Summary: Core-sheath nanofibers with conductive polyaniline as the core and an insulating polymer as the sheath were prepared by electrospinning of blends of polyaniline with either polystyrene or polycarbonate. These unique core-sheath structures offer potential in a number of applications including nanoelectronics. When polyaniline was blended with poly(methyl methacrylate) and poly(ethylene oxide), only isolated domains of polyaniline in beadlike structures were formed. The phase morphology of electrospun fibers is thought to be dependent on the high-surface tension of the solution and the molecular weight of the polymers. Incompatibility of the polymers and low molecular weight of compositions played a key role in the formation of core-sheath structures, as opposed to co-continuous morphologies.
TEM image of electrospun polyaniline/polystyrene nanofiber after staining by OsO4. The dark regions are polyaniline.
TL;DR: In this paper, it was demonstrated that the nanowires grew by rod-to-rod association, in which the molecular long axis of the P3HT chains appeared to be well-oriented parallel to the silicon substrate (Si/SiOx).
Abstract: Summary: Nanowire lengths and length-to-width aspect ratios in regioregular poly(3-hexylthiophene) (P3HT) were simply controlled through changes in the solvent vapor pressure during solidification. It is demonstrated that the nanowires grew by rod-to-rod association, in which the molecular long axis of the P3HT chains appeared to be well-oriented parallel to the silicon substrate (Si/SiOx). The formation of the nanowires took place by one dimensional self-assembly, governed by π-π stacking of the P3HT units.
TEM high contrast images showing P3HT nanowires fabricated by spin-coating under a solvent vapor pressure.
TL;DR: In this article, the compatibilization efficiency of organically modified montmorillonite (OMMT) in immiscible polycarbonate (PC)/poly(methyl methacrylate) (PMMA) blends for the first time was described.
Abstract: Summary: This communication describes the compatibilization efficiency of organically modified montmorillonite (OMMT) in immiscible polycarbonate (PC)/poly(methyl methacrylate) (PMMA) blends for the first time. The size of the dispersed PC particles was reduced significantly upon the addition of OMMT (6 wt.-%) to the blend. The compatibilization effect of the OMMT was also assessed by differential scanning calorimetry, mechanical properties and thermal stability analysis of the modified blend.
SEM images of the fracture surfaces.
TL;DR: In this article, the first organocatalytic, bulk ring-opening polymerization (ROP) of e-caprolactone (e-CL) with solid cotton and paper cellulose as the initiators is presented.
Abstract: We have developed the first direct, organocatalytic, bulk ring-opening polymerization (ROP) of e-caprolactone (e-CL) with solid cotton and paper cellulose as the initiators. The mild ROPs were performed without solvent, and are operationally simple, inexpensive and environmentally benign. Organic-acid-catalyzed heterogeneous derivatization of cellulose provides a novel route to valuable cellulose-based biocompatible nanomaterials. The furnished polymerization products were characterized by FTIR, 1 H and 13 C NMR spectroscopy, MALDI-TOF mass spectrometry and electron microscopy.
TL;DR: In this paper, a polyamide film with a triangular net-like structure was shown to switch between superhydrophobic and super-hydrophilic wettability by biaxially extending and unloading the elastic film.
Abstract: Reversible switching between superhydrophobic and superhydrophilic wettability of a polyamide film with a triangular net-like structure can be achieved by biaxially extending and unloading the elastic film. Both the change of the average side-length of the triangular net-like structure upon biaxial extension and unloading, and the surface tension of the water droplet, are believed to be responsible for the reversible switching between superhydrophobicity and superhydrophilicity.
TL;DR: An oil-in-water high internal phase emulsion I consisting of acrylic acid, water, and a crosslinker (N,N'-methylene bisacrylamide) as the water phase, and toluene as the oil phase was successfully stabilised to sustain thermal initiation of radical polymerization resulting in porous open-cellular monolithic material as mentioned in this paper.
Abstract: An oil-in-water high internal phase emulsion I consisting of acrylic acid, water, and a crosslinker (N,N'-methylene bisacrylamide) as the water phase, and toluene as the oil phase was successfully stabilised to sustain thermal initiation of radical polymerisation resulting in porous open-cellular monolithic material. The type of initiator used influenced the average pore size ranging from approx. 708 nm to approx. 1 087 nm, as determined by mercury porosimetry.
TL;DR: In this paper, the reaction between octaaminophenyl polyhedral oligomeric silsesquioxane (OAPS) and 2,2'-(1,3-phenylene)-bis(4,5-dihydro-oxazoles) (PBO) over different temperature ranges was confirmed by FT-IR spectroscopy.
Abstract: The reaction between octaaminophenyl polyhedral oligomeric silsesquioxane (OAPS) and 2,2'-(1,3-phenylene)-bis(4,5-dihydro-oxazoles) (PBO) over different temperature ranges was confirmed by FT-IR spectroscopy. The OAPS was used to modify benzoxazine (BZ) in the presence of PBO. The novel polybenzoxazine (PBZ)-PBO/ OAPS hybrid nanocomposite was prepared by solvent methods. Dynamic mechanical analyses indicated that the nanocomposites exhibited much higher T g values than the pristine PBZ and PBZ-PBO resin, and the storage modulus of the nanocomposites was maintained at higher temperatures, although only a small amount of OAPS was incorporated into the systems. Dynamic thermogravimetric analysis showed that the thermal stability of the hybrid was also improved by the inclusion of OAPS.
TL;DR: In this paper, the authors used ink-jet printing of an oxidizing agent to pattern a pre-ocated conducting polymer, poly(3,4-ethylenedioxy)-thiophene-poly(styrene sulfonate) (PEDOT-PSS), yielding electrodes with predefined shapes and a controlled degree of sheet resistivity for use in gray-scale organic light-emitting devices (OLEDs).
Abstract: Due to its capability of dispensing very small volumes of different liquids in a control manner, ink-jet printing is well suited for combinatorial experiments. The multi-nozzle ink-jet delivery system is especially advantageous for parallel chemical synthesis of different materials. We have used ink-jet printing of an oxidizing agent to pattern a pre-ocated conducting polymer, poly(3,4-ethylenedioxy)-thiophene-poly(styrene sulfonate) (PEDOT-PSS), yielding electrodes with predefined shapes and a controlled degree of sheet resistivity for use in gray-scale organic light-emitting devices (OLEDs). The electrical and optical properties of the PEDOT-PSS layer are modified via chemical interaction using the oxidizing agent, These experiments were performed using a desktop ink-jet printer in conjunction with common graphic software which employed color functions such as CMY (cyan, magenta and yellow), HSL (hue, saturation and luminosity) and RGB (red, green and blue).
Abstract: The liquid-liquid phase separation (LLPS) is of-ten coupled with other ordering processes such as crystallization. In a polyolfein blend system, overwhelming changes fluctuation-assisted crystallization. In this process, the usual nucleation barrier could be overcome (or at least partially) by the spontaneous fluctuation growth of LLPS in the spinodal region.
TL;DR: In this paper, the properties of monodisperse oligofluorenes (OEn, n = 2 to 7) and corresponding polyfluorene were studied by cyclic and differential pulse voltammetry.
Abstract: Electrochemical properties of monodisperse oligofluorenes (OEn, n = 2 to 7) and corresponding polyfluorene were studied by cyclic and differential pulse voltammetry. In combination with data of UV-vis absorption spectra, a series of linear relations such as the band gap, the oxidation potential, the ionization potential, and the electron affinity with the reciprocal number of the fluorene units (1/n) were deduced. When a chain length of ca. 14 repeat units is reached, a stable structure of about one positive charge per 3.5 repeat units is obtained.