Dedoped State Research Articles

Chemically dedoped PEDOT:PSS films with an amidine/polymer overcoating and their applications as a semiconducting channel in organic field-effect transistors and inverters

We investigate the properties of a conducting polymer composite of poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) after chemical dedoping with an amidine base and demonstrate the applications of the dedoped films as a semiconducting channel in a transistor and an inverter. We observe that PEDOT:PSS can be chemically transformed from a conductor to a semiconductor through a post-treatment with 1,5-diazabicyclo[4.3.0]non-5-ene (DBN), which can donate electrons to the oxidized PEDOT chains and screen negative charges of PSS by salt formation. Both appearance of visible absorption bands and disappearance of (bi)polaronic absorption bands are observed in the DBN-treated PEDOT:PSS film, suggesting the effective dedoping. Compositional depth profiling and morphological analyses show that two distinct layers evolve after chemical dedoping and that the majority of internal PEDOT chains are dedoped over the whole film. We also introduce an overcoating layer using polyvinylpyrrolidone (PVP) with DBN to get more stable PEDOT:PSS films in a dedoped state. Organic field-effect transistors (OFETs) with the dedoped PEDOT:PSS film as a semiconducting channel show the typical p-type enhancement-mode characteristics without any doping-induced shift of threshold voltage. The pinch-off, hard saturation, and distinguishable switching characteristics with on-to-off current ratio of 104 are observed without redoping. We also demonstrate a logic circuit from the OFET as a proof-of-concept of semiconducting nature of PEDOT:PSS.

(Invited) Impedimetric Detection of Histamine Using PEDOT:PSS-Based Organic Electrochemical Sensor for Precision Animal Agriculture

Introduction As human world population is expected to reach 9.8 billion by the year 2050 [1], the consumption of animal products is also expected to increase by a large margin, including dairy and meat. Therefore, improving the feed nutrients convergence to final products in a sustainable way is highly needed. One approach is diagnosing animal diseases in early stage with the use of biosensors, which can monitor various biomarkers, chemical molecules, present inside rumen. This will allow improvement in animal diet, with subsequent increase of energy convergence from diet to animal protein [2].Our group is currently developing a set of technologies to accomplishing such early diagnosis. One of the components is a miniature robotic agent, termed RUMENS (Rumen Understanding through Millipede-Engineered Navigation and Sensing), an active sensing platform hosting an array of commercial and purpose-built sensors [3]. Histamine is a biomarker present inside rumen, of which high levels are closely linked to subacute ruminal acidosis (SARA). SARA is a common disease in high-producing lactating cows, leading to decrease in production of animal proteins [4]. Here, we report on an electrochemical impedimetric histamine sensor. Method Polymeric semiconductor poly(3,4-ethylenedioxythiophene) polystyrene sulfonate, or PEDOT:PSS, (Clevios PH 1000) was purchased from Heraeus (Holding GmbH Hanau, Germany). Histamine, ethylene glycol (EG), isopropyl alcohol (IPA), 3-glycidoxypropyltrimethoxysilane (GOPS), dodecylbenzenesulfonic acid solution (DBSA), acetone, and phosphate-buffered saline powder (pH=7.4) were all purchased from Sigma Aldrich (St. Louis, MO, USA). All chemicals were used without any purification. PEDOT:PSS solution was prepared by mixing 95 Vt.% PEDOT:PSS aqueous suspension with 1 Vt.% of GOPS, 3.98 Vt.% of EG, and 0.02 Vt.% DBSA. The electrolytes were histamine dissolved in phosphate buffer saline (PBS, pH=7.4). The glass substrates were cleaned by sonicating in DI water, IPA, and acetone. Cr and Au were thermally evaporated (Lesker, Nano 36) on clean substrates, with a thicknesses of 4 nm and 30 nm, respectively. Subsequently, a plasma processing in high mode for 3 minutes was carried out, using reactive ion etching (Glow Research) to activate the substrate surface. Next, PEDOT:PSS film was spin cast at 2000 rpm for 60 seconds, followed by annealing at 140 °C for 70 minutes in air, resulting in a thickness of 150 nm. Finally, PEDOT:PSS was patterned using dry plasma etching through a shadow mask.An impedance measurement was carried out to test the impedance with different histamine concentrations (from 0.1 µM to 1 mM). 3 μL electrolyte was dropped on the PEDOT:PSS layer (at the right-top of Figure1). Devices were cleaned by immersion in DI water for 10 min between measurements to remove remaining histamine. Results and Conclusions As shown in Figure 1, the real part (Z’) of impedance was increasing with the increased histamine concentration: at lower frequencies, the increase in Z’ was monotonically correlated with the concentration (right side of the graph), which did not hold at higher frequencies (left side of the graph). More specifically, we can find that from the left-top inset, the real part of the impedance has a significant positive relationship with the histamine concentration, with R2 as high as 0.95. Since PEDOT:PSS is a ionic semiconductor, which means the ions could diffuse into PEDOT and PSS moieties. The active aliphatic amino group on the ethylamine part in histamine is protonated in neutral electrolyte. Thus, histamine plays the role of cations, which can reversibly penetrate into PEDOT:PSS layer then block the holes transport by a dedoping process. Consequently, the diamine will be oxidized, while the partially doped PEDOT segment will be reduced to the dedoped state. Higher histamine concentration represents higher degree of dedoping process. Therefore, the conductivity of PEDOT:PSS will decrease, leading to increase in impedance [5].

The importance of sulfonate to the self-doping mechanism of the water-soluble conjugated polyelectrolyte PCPDTBT-SO3K

In-depth understanding of the doped and de-doped states of CPE-K, a unique, water-soluble, highly conductive polymer.

Electrochemical synthesis and investigation of poly(1,4-bis(2-(3,4-ethylenedioxy)thienyl)benzene) and its application in an electrochromic device

1,4-Bis(2-(3,4-ethylenedioxy)thienyl)benzene, prepared by Stille cross-coupling reaction was successfully electrochemically polymerized to give polymer 1,4-bis(2-(3,4-ethylenedioxy)thienyl)benzene (PEBE). Characterizations of the resulting polymer PEBE were performed by cyclic voltammetry (CV), UV–vis, Fourier transform infrared spectroscopy and scanning electron microscopy. Moreover, the spectroelectrochemical and electrochromic properties of the polymer film were investigated. The resulting polymer film has distinct electrochromic properties and shows three different colors (deep red, gray, and light blue) under various potentials. At the dedoped state of the polymer, the π–π* transition absorption peak is located at 510 nm and the optical band gap (E g) was calculated as 1.92 eV. The PEBE film shows a maximum optical contrast (ΔT%) of 31.0 % at 500 nm with a response time of 0.85 s. The coloration efficiency of PEBE film was calculated to be 182.2 cm2C−1. An electrochromic device (ECD) based on PEBE and poly(3,4-ethylenedioxythiophene) was also constructed and characterized. The response time was measured as 0.4 s, and the coloration efficiency of the device was calculated to be 225.4 cm2C−1. Furthermore, this ECD exhibited satisfactory optical memories and redox stability.

Visible to Near-IR Electrochromism and Photothermal Effect of Poly(3,4-propylenedioxyselenophene)s

A new selenophene derivative, 3,4-propylenedioxyselenophene (ProDOS), was electropolymerized to a polymeric thin film which demonstrated wide spectral tunability from the visible to near-infrared (NIR) region. The anodic and cathodic peaks of the polymeric ProDOS (PProDOS) were observed at +0.22 and −0.30 V, showing a narrow band gap. In the visible region, the PProDOS film showed color change from navy blue in its dedoped state (−0.12 V vs Ag/AgCl) to highly transparent pale gray green in its doped state (0.68 V vs Ag/AgCl) with a high coloration efficiency (CE) of 273 cm2 C–1 and large transmittance change (contrast ratio of 5.7). The color change of the PProDOS film by electrochromism in the visible region was simultaneously accompanied by NIR electrochromism. Upon exposure to a NIR source (0.7 W cm–2), the doped PProDOS film resulted in a temperature rise of 10.7 °C compared to that of the bare indium tin oxide (ITO) coated glass, while the navy blue colored PProDOS film experienced a temperature rise of 10.2 °C. This photothermal effect by NIR light exposure was switchable between the colored and bleached state by simply dedoping and doping the film electrochemically, respectively. Furthermore, bleached PProDOS particles dispersed in water (0.05 mg mL–1) also showed a high photothermal effect (2 W cm–2) with a temperature rise of 13.1 °C, as compared to pure water. Compared with poly(3,4-ethylenedioxythiophene) (PEDOT), it was found that the new selenophene polymer (PProDOS) provided efficient visible to NIR electrochromism in addition to the high photothermal effect, resulting in a large temperature rise and heat conversion upon exposure to a NIR source.

Semi-conducting poly( 1-naphthylamine) nanotubes: A pH independent adsorbent of sulphonate dyes

Due to serious environmental consequences of dyestuff usage and disposal, stringent regulations and measures are being adopted by governments all over the world. Among the various adsorbents used, conducting polymers have recently attracted attention for the removal of dyes and waste water purification. The present study, reports for the first time, utilization of nanotubes of conducting poly( 1-naphthylamine) (PNA) as an adsorbent for the removal of sulphonate dyes – commassie brilliant blue R-250 (CB) and orange G (OG). The adsorption of CB as well as OG dyes onto PNA–camphorsulphonic acid (CSA) and PNA was studied by equilibrium isotherms, and adsorption kinetics, while the conformational, morphological and conductivity changes of the dye adsorbed PNA nanotubes were investigated by UV–vis, morphological and conductivity measurements. Maximum adsorption capacity of PNA–CSA in CB acidic and basic media was obtained as 252 mg of dye/g of PNA and 188 mg of dye/g of PNA, respectively, while for PNA, the adsorption capacity was found to be 200 mg of dye/g of PNA and 185 mg of dye/g of PNA in acidic and basic media, respectively. Likewise, maximum adsorption capacity of PNA–CSA for OG in acidic and basic media was obtained respectively as 328 mg of dye/g of PNA and 296 mg of dye/g of PNA while for PNA, the adsorption capacity was found as 315 mg of dye/g of PNA and 277 mg of dye/g of PNA in acidic and basic media. UV–vis studies confirmed the doping of PNA by the dyes in acidic and basic media. Conductivity measurements revealed that dye adsorbed PNA exhibited conductivity in the semi-conducting range. The nanotubes of PNA revealed adsorption capacity in both acidic, basic media even in the dedoped state, the property not shown by other conducting polymers. PNA can, therefore, be used as a pH independent adsorbent for the removal of dyes in doped and dedoped states.

Nanojunctions in conducting polypyrrole single nanowire made by focused electron beam: Charge transport characteristics

A focused electron (E)-beam with various doses was irradiated on the intended positions of conducting polypyrrole (PPy) single nanowire (NW) to fabricate nanojunctions. The current-voltage characteristics and their temperature dependence of the PPy single NW with nanojunctions were measured and analyzed. By increasing the E-beam dose and the number of nanojunctions, the current level of the single NW was dramatically decreased, and the conductance gap became more severe as the temperature decreased. The charge transport behavior varied from three-dimensional variable range hopping to fluctuation induced tunneling models, depending on the dose of focused E-beam. From micro-Raman spectra, the focused E-beam irradiation induced the de-doped states and conformational modification of polymer chains in the nanojunctions. The results suggest that the nanojunctions made by focused E-beam acted as a quasi-potential barrier for charge conduction in the conducting PPy single NW.

Electrochemical copolymerization of benzanthrone and 3-methylthiophene and characterization of their fluorescent copolymer

Poly(3-methylthiophene-co-benzanthrone), a novel copolymer, was successfully achieved by electrochemical oxidation of the monomer mixtures of 3-methylthiophene (3MeT) and benzanthrone in the binary solvent system containing boron trifluoride diethyl etherate and acetonitrile. A series of experiments with different monomer feed ratios were carried out to investigate the influence of monomer feed ratio on the electrochemical copolymerization and the overall properties of the copolymer films. The resulting copolymer possesses the advantages of both polybenzanthrone and poly(3-methylthiophene), such as considerable fluorescence property, good redox activity, high thermal stability, and relatively high electrical conductivity. Ultraviolet–visible, FT-IR, and thermal analysis were used to characterize and investigate the structure and thermal stability of the copolymers. Fluorescence spectroscopic studies revealed that the copolymer dissolved in common organic solvents was a good green or yellow-green light emitter, with a strong emission at 499 nm in doped state and 529 nm in dedoped state.

Quantitative in-situ EPR spectroelectrochemical studies of doping processes in poly(3,4-alkylenedioxythiophene)s: Part 1: PEDOT

Quantitative in-situ EPR spectroelectrochemical studies of poly(3,4-ethylenedioxythiophene) (PEDOT) have been carried out with an aim to gain new insights into the doping processes taking place in this polymer. Corroborating the findings made during previous studies of this polymer, absolute measurements conducted in this study provided new detailed information regarding some of the basic parameters characterising the doping process of this conjugated polymer. It was found that concentrations of paramagnetic centres in PEDOT vary from 0.02 spin per mer in the dedoped state up to a maximum of 0.12 spin per mer at 0.15 [e −/mer] doping level, corresponding to 1 spin per ca. 8.5 meric units. Such notable concentration values indicate that polarons represent a numerous charge carrier group in PEDOT, contrary to observations made for other members of polythiophene family. Furthermore polarons do not disappear at high doping levels of PEDOT but rather decrease their numbers gradually down to 0.08 spins per mer at a maximum doping level of 0.55 [e −/mer] attained in this study. Based on information about concentrations of spins and polymer doping charges, concentrations of bipolarons have been evaluated as a function of doping level. Results indicate that bipolaron formation starts at ca. 0.06 [e −/mer] doping level when spin generation efficiency begins to deviate from 1 and interspin interactions emerge as evidenced by doping level dependency of EPR signal linewidth (Δ B pp). Decomposition of complex EPR spectra of PEDOT in its doped state corroborated the presence of two groups of paramagnetic centres in this polymer. Based upon doping level dependencies of their spectroscopic parameters (concentration, Δ B pp linewidth and g-factor), the identity of these centres has been redefined compared to our previous reports, linking their properties with the type of polymer phase (crystalline or amorphous) they reside in.

Doped and de-doped polypyrrole nanowires by using a BMIMPF 6 ionic liquid

We electrochemically synthesized π-conjugated polypyrrole (PPy) nanowires by using an environmentally stable and recyclable ionic liquid, 1-butyl-3-methylimidazolium hexafluorophosphate (BMIMPF 6), as a dopant, based on an anodic alumina oxide (Al 2O 3) nanoporous template. The de-doped states of the PPy nanowires were obtained from doped PPy nanowires through cyclic voltammetry (CV) using a solution of the catalyst in the BMIMPF 6 ionic liquid. We confirmed the de-doped states of PPy nanowires based on a decrease of the bipolaron peak of the ultraviolet and visible (UV–vis) absorbance spectra. The formation of PPy nanowires was visualized by using scanning electron microscopy and transmission electron microscopy. We studied the optical and structural properties of the doped and de-doped PPy nanowires by UV–vis absorbance and Fourier transform-infrared spectra. Our work included obtaining a laser confocal microscope Raman spectra for a single strand of the PPy nanowires.

Electropolymerization of 1,2-methylenedioxybenzene in 1-butyl-3-methylimidazolium hexafluorophosphate room temperature ionic liquid

The electrochemical polymerization of 1,2-methylenedioxybenzene (MDOB) in a room temperature ionic liquid 1-butyl-3-methylimidazolium hexafluorophosphate (BmimPF6) has been investigated. Its polymer poly(1,2-methylenedioxybenzene) (PMDOB) showed good redox activity and stability even in concentrated sulfuric acid. IR and 1H NMR spectra confirmed that the polymerization occurred at the C4 and C5 positions on the benzene ring of MDOB, resulting in the main backbone of PMDOB similar to polyacetylene. In contrast to acetonitrile containing 0.1mol/L Bu4NBF4, BmimPF6 serves as both the growth medium and an electrolyte. Hence, enhanced electrochemical stability of PMDOB can be easily obtained on repetitive redox cycling. As-formed PMDOB represented good electrochromic properties from green grass to opalescent between doped and dedoped states. Scanning electron microscopic results demonstrated that smooth and compact PMDOB films composed of ordered nanostructures were obtained, implying their possible utilizations in ion-sieving films, ion-selective, and matrices for catalyst particles.

Conducting polymeric nanoparticles synthesized in reverse micelles and their gas sensitivity based on quartz crystal microbalance

Conducting polymer poly(3,4-ethylenedioxythiophene) (PEDOT) nanoparticles were prepared by reverse micelle method, which could be well dispersed in water or alcoholic solvent with ultrasonic treatment. The formation and doped state of PEDOT nanoparticles were confirmed by UV–vis–near IR absorption spectrum, X-ray photoelectron spectroscopy (XPS) and FT-IR spectrum. The nanoparticles with the size of ca. 20–40nm were characterized by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Compare to electrical conductivity of conventional PEDOT particles (ca. 0.5S/cm), the as-prepared palletized nanoparticles have higher conductivity (ca. 10.2S/cm) and the conductivity varies with the doped and de-doped states of PEDOT. As for sensing property, it has been found that QCM device coated with nanoparticles shows faster response and recovery to 20ppm ammonia gas (ca. 50s) than that of conventional PEDOT particles. The PEDOT nanoparticle covered device exhibits almost linear relation to lower NH3 gas concentration and shows a saturate tendency of gas sensitivity with the increase of gas concentration over 500ppm. The mechanisms of electrical conductivity and gas sensitivity of PEDOT nanoparticles were also discussed.

Reversible control of kinesin activity and microtubule gliding speeds by switching thedoping states of a conducting polymer support

We describe a method for reversibly controlling the ATPase activity of streptavidin-linkedkinesin by changing the doping states of a conducting polymer support. When the polymer(poly(CH2OH-EDOT)) was electrochemically switched from its dedoped (semiconducting) state to its doped(conducting) state, the ATPase activity of the adsorbed kinesin complex decreased by 35%with a concomitant decrease in the gliding speeds of kinesin-driven microtubules. When thepolymer was switched back to its original dedoped state, nearly identical increases wereobserved in the kinesin ATPase activity and microtubule speeds. Use of a fluorescentATP substrate analogue showed that the total amount of kinesin adsorbed on thepoly(CH2OH-EDOT) surface remained constant as the doping state of the polymer was switched. Themicrotubules exhibited nearly identical speed differences on the doped and dedopedsurfaces for both chemical and electrochemical doping methods. Michaelis–Mentenmodelling suggests that the doped surface acts as an ‘uncompetitive inhibitor’ of kinesin.This work represents an investigation into the phenomenon of an electrically switchablesurface exerting a moderating effect on the activity of an adsorbed protein that does notcontain a bound, electroactive metal ion.

Studies of dopant effects in poly(3,4‐ethylenedi‐oxythiophene) using Raman spectroscopy

AbstractRaman spectroscopy has been used to study the doping processes in poly(3,4‐ethylenedioxythiophene) PEDOT prepared via conventional electrochemical methods. The initially doped PEDOT films resulting from the polymerization process were first dedoped before being further oxidized in different electrolyte solutions at a number of different potentials to generate polymer films doped with a variety of dopants with different doping levels. Raman spectra of these re‐doped PEDOT films were recorded ex‐situ in order to monitor the progress of the re‐doping processes by observing the shifts in the positions of CC stretching vibrations. This has provided an understanding of the extent of conversion between PEDOT structures from the dedoped state to the highly doped state during electrochemical re‐doping. It was discovered that the extent of conversion varies with the type of dopant incorporated in the polymer films, which suggests that the doping process depends also on the nature of the dopant. Factors such as the size, the structural complexity and the charge on the dopant are believed to have significant effects on the efficiency of the doping processes in PEDOT. A curve‐fitting method was also applied to fit the symmetric CαCβ stretching band and its neighboring bands, in order to calculate the ratio of the band intensities due to the neutral and the oxidized structures in PEDOT. The doping level can then be approximately estimated by substituting this ratio into a previously determined correlation equation. Copyright © 2006 John Wiley & Sons, Ltd.

Electrosyntheses of Freestanding and Conducting Poly[poly(N-vinyl-carbazole)] Films in Tetrahydrofuran Containing Additional Boron Trifluoride Diethyl Etherate

Freestanding and conducting poly[poly(N-vinyl-carbazole)] (PPVK) films with good fluorescence property were synthesized electrochemically by direct anodic oxidation of poly(N-vinyl-carbazole) (PVK) in tetrahydrofuran containing boron trifluoride diethyl etherate (BFEE) (12%, by volume) and Bu4NBF4 (0.05 M). The oxidation onset potential of PVK in this medium was measured to be 1.07 V vs. SCE. PPVK films obtained from this medium showed good electrochemical behavior and good thermal stability with conductivity of 10−2 S cm−1. PPVK films were black in doped state and transparent white in dedoped state. Structural studies showed that the secondary polymerization of PVK occurred at benzene ring. These polymer films had good mechanical properties, which can be easily cut into a variety of structures with a knife or a pair of scissors.

Hyperbranched Sulfonated Polydiphenylamine as a Novel Self-Doped Conducting Polymer and Its pH Response

A synthesis strategy for a hyperbranched sulfonated polydiphenylamine was developed. First, a hyperbranched polyvinylbenzoxylamine (H-PVBPA) was prepared by controlled atom transfer radical copolymerization of an amino-protected vinylbenzoxylamine (4-VBPA-tBOC) and 4-chloromethyl styrene followed by deprotection. Second, H-PVBPA was reacted with sodium diphenylamine sulfonate under acidic conditions to generate hyperbranched sulfonated polydiphenylamine (H-PSDA). The H-PSDA exhibited conductivities of 3.7 × 10-2 and 1.2 × 10-2 S/cm in HCl-doped and self-doped states, respectively. The microstructure of H-PSDA in aqueous solutions was found to be sensitive to the pH. In the dedoped state (at pH ≥ 7), AFM identified nanoscale particles of uniform size around 40 nm. The self-doped H-PSDA aggregated at pH = 7 via intermolecular doping interaction, generating large and irregular particles (>200 nm). When the pH was decreased below 5, the aggregates could be dispersed as smaller particles of about 120 nm becaus...

ESR spectroelectrochemistry of poly(3,4-ethylenedioxythiophene) (PEDOT)

In situ ESR spectroelectrochemical studies of poly(3,4-ethylenedioxythiophene) (PEDOT) have been performed, in an attempt to take a closer look at species responsible for the conductivity of the polymer in the doped state. A series of ESR spectra at progressively changed potentials applied to the polymer film in the oxidation and subsequently, reduction half-cycles were recorded. The results reveal distinct ESR lines with a noteworthy concentration of spins in the reduced state of the polymer and marked changes in both the intensities and Δ B pp widths of the ESR signal across the studied potential range, indicating non-trivial changes in the character of charge carriers with changing potential. Also, interesting phenomena like the potential hysteresis of the spin concentration and of Δ B pp linewidths between the oxidation and reduction cycles of the polymer are observed. The presence of residual spins in the polymer in the reduced state may indicate that at least to some partial extent, PEDOT chains exist in the quinoid rather than benzoid configuration in the dedoped state. Hysteresis of spectroscopic parameters may imply that certain hindrance factors like slow anion expulsion speed accompany the dedoping process of the polymer.

Electrochemical Polymerization of Thianaphthene in Mixed Electrolytes of Boron Trifluoride Diethyl Etherate and Trifluoroacetic Acid

AbstractSubstrate‐supported polythianaphthene (PTN) films have been electrochemically synthesized by direct oxidation of thianaphthene on platinum or stainless steel electrode in mixed electrolytes of boron trifluoride diethyl etherate (BFEE) and trifluoroacetic acid (TFA). The oxidation potentials of the monomer in these media are considerably lower than those in neutral solvents. Increasing the content of TFA in the mixed electrolytes can effectively decrease the oxidation potential and increase the coupling rate of the monomer. On the other hand, a high TFA concentration can result in a negative effect on the properties of the as‐formed polymer. The mixed electrolyte of BFEE + 16.7% TFA was found to be the most suitable medium for the electrosyntheses of PTN. PTN in dedoped state is soluble in usual strong polar organic solvent such as dimethyl sulfoxide (DMSO). Fluorescent spectral studies indicate that the polymer is a blue light emitter. magnified image

Electrochemical polymerization of thianaphthene

Thianaphthene has been electrochemically polymerized in pure boron trifluoride diethyl etherate (BFEE) solution or in a mixed electrolyte of BFEE and concentrated sulfuric acid (SA). The addition of a certain amount of sulfuric acid into BFEE accelerated the polymerization and also increased the current efficiency of the electrosynthesis. Poly(thianaphthene) (PTN) in the dedoped state is soluble in usual strong polar organic solvents such as dimethyl sulfoxide (DMSO), N, N-dimethylformamide (DMF) and N-methyl pyrrolidinone (NMP). Its structure has been examined by infrared, H 1-NMR and UV spectra. Fluorescent spectral studies indicate that the polymer is a strong blue light emitter.

Stability and behavior of poly-1-naphthol films towards charge transfer reactions

Conducting poly-1-naphthol films (0.5–2.0 μm) showed a decreasing tendency for doping with film thickness. The average specific capacitance of poly-1-naphthol films formed by cyclic voltammetry in MeCN containing tetrabutylammonium perchlorate in the reduced dedoped state was found to be ∼ 10 mF cm −3 and increased on electrochemical oxidation (doping) to ∼ 60 mF cm −3. Stabilization of the polymer by repetitive cyclic voltammetry led to increase or decrease in the redox charge with number of cycles, depending on the final oxidation potential and in all cases, the peak separation decreased due to rearrangement of the polymer chains. The polymer doping/dedoping processes showed a pronounced increase in the diffusion coefficient of the charge transfer with thickness and a substantial difference between the doping and dedoping process. The doping process is controlled by an initial fast charge propagation step and followed by a slower step of anion insertion into the polymer film while in the dedoping only the anion removal from the film could be distinguished. The electron transfer for the redox [Fe(CN) 6] 4−/3− on the polymer films showed also a strong dependence on film thickness. It is inferred that the polymer film is composed of two layers; an inner compact layer (< 1 μm) which impedes to a larger extent the charge transfer reactions and an outer less compact and easily removable layer with more facile permeability. When the film is thickened, however, the inner layer is partially distorted and its barrier character towards charge transfer is gradually lost.