The synthesis and characterization of conducting polymers have become one of the most important areas of the research in polymer and materials science. In general, conductive polymers can be synthesized by different methods, with chemical polymerization (classical organic synthesis) and electrochemical polymerization (electrochemical synthesis) being the most commonly used processes. The following sections describe these two different synthesis techniques of polycarbazole and its derivatives.
Carbazole presents several active positions (3,6-, 2,7-, and 1,8-positions), being the 3,6 postions easier to polymerize. Poly(N-vinylcarbazole) and its derivatives has been highly studied since decades, but in the last decade 3,6-carbazole derivatives have been intensively investigated. Nevertheless, these derivatives present several limitations in their application due to their low molecular weight and poor conjugation of the electrons in their structure. On the other hand, the development of 2,7-carbazoles present better properties and applicability than the 3,6 due to their extended conjugation and lower band gap [70
]. Finally, poly(1,8-carbazole) derivatives are the less developed derivatives, and poly(1,8-cabazole) is less planar compared to 3,6 and 2,7 [93
]. However, this property makes these derivatives more suitable for the electrets of photoresponsive organic field-effect transistor memory applications [46
2.1. Chemical Polymerization of Carbazoles and Its Derivatives
Chemical polymerization of carbazole has been carried out in the presence of oxidizing agents such as ammonium persulphate ((NH4
) (APS), ferric chloride (FeCl3
), and potassium dichromate (K2
). The structure and properties of the obtained polymer are strongly dependent on the concentration, the catalyst (oxidizing agent), and the solvent [74
]. The chemical synthesis takes place by oxidation-reduction reactions that are accompanied by a change in the number of electrons in the π system. The first studies on the oxidation of carbazole were published by Branch and Tucker [95
]. Although the most commonly used dopants are FeCl3
, these oxidants can promote polymer aggregation and, as consequence, important problems on the device production. To overcome this drawback Aoai et al. [98
] described a photodoping method based on the use of triaylsulfonium or diaryliodonium salts as PAG (photo acid generator).
The mechanism proposed for the synthesis of PCz (or poly(3,6-cabazole)) is presented in Figure 4
. As depicted in Figure 4
, first, carbazole monomer is oxidized by a single electron transfer forming the cation radical. Then more stable dicarbazyl dimer is produced as a result of the coupling of two cation radicals and the loss of two protons. Regarding the regiochemistry, the polymerization process takes place at 3 or 6 positions. The reactivity of 1 and 8 positions is probably prevented by the rigid structure of carbazole heterocycle.
In order to guarantee de oxidation of the carbazole core, and so, polymerization process, a minimum electronic density has to be ensured in the starting monomer. Consequently, strong electron-withdrawing substituents in the aromatic framework do not benefit the reaction.
Shakir and co-workers [100
], reported one of the first attempt to obtain a new conductive nanocomposite of polycarbazole (PCz) with titanium dioxide (TiO2
) nanoparticles. This composite was successfully synthesized by in-situ chemical polymerization in the presence of different amounts of nanosized TiO2
using ammonium persulfate (APS) as oxidizing agent, in 1:1 molar ratio (Cz:APS), in dichloromethane at room temperature for a period of 24 h (Figure 5
). It is important to notice that, in a first step, the different solutions of TiO2
nanoparticles were added dropwise to the monomer solution under constant stirring, this step allows the carbazole absorption on the surface of the nanoparticles before its polymerization. Creamy coloured solutions were obtained which later transformed into greenish black sediments. The characterization results revealed that the polymerization of PCz had been achieved on the surface of the TiO2
nanoparticles indicating strong interaction between PCz and TiO2
nanoparticles. The same approach was also carried out by Baig et al. [101
] for the synthesis of zirconium (IV) phosphate/polycarbazole nanocomposites.
It is important to notice that this nanocomposite presents antimicrobial properties. The antibacterial activity was in vitro evaluated against Staphylococcus aureus, Staphylococcus epidermidis, Proteus mirabilis, and Escherichia coli. Shakir et al. reported an improvement in the antimicrobial activity for the PCz/TiO2 Nanocomposite compared to TiO2.
The first work on the chemical synthesis of unsubstituted polycarbazole and the formation of hollow microspheres based on this polymer was reported by Gupta and Prakash in 2010 [102
]. Interfacial polymerization of carbazole was carried out using ammonium peroxodisulfate (1.2 M) as oxidizing agent in dichloromethane at room temperature. After 12 h of polymerization, dark green polycarbazole films were obtained with a yield of 50% ± 2%. During this interfacial polymerization, three-dimensional hollow spheres of polycarbazole of various diameters in the range of a few micrometers were obtained. The growth of these spheres was observed using scanning electron microscopy (SEM) and atomic force microscopy (AFM) techniques at different time intervals. These hollow microspheres are grown in the carbazole micelles formed in the interface. That is, monomer micelles are formed in the reaction solution at the interface due to the agitation (mechanical or thermal) [102
]. The polymerization begins inside the micelles and they act as a template for the polycarbazole, being the size of the micelle dependant on the reaction conditions (temperature, concentration, stirring rate, etc.).
A similar procedure was followed by Sangwan et al. [99
], in their work the effects of surfactants and their concentration on interfacial polymerization of carbazole was studied. Three surfactants of different nature such as nonionic Tween 20 (TW20), cationic hexadecyltrimethylammonium bromide (CTAB), and anionic sodium dodecyl sulphate (SDS) were used for different micelle formation. Ammonium persulfate (APS) was used as oxidizing agent, being the polymerization performed in dichloromethane (DCM) at 25 °C for 24 h.
The reported SEM images revealed several PCz morphologies depending on the surfactant type and concentration. As it could be observed at Figure 6
, macroporous honeycomb (Figure 6
b), connected hollow spheres (Figure 6
c), and smaller hollow spheres (Figure 6
d) when using TW20, CTAB and SDS, respectively. On the other hand, for the system with no surfactant, the particle shapes are typically hollow sphere structures (Figure 5
a). In addition, the electrical conductivity of the different PCz were measured being 1.72 ± 0.06 × 10−4
, 2.62 ± 0.79 × 10−3
, 2.16 ± 1.79 × 10−5
and 2.72 ± 0.32 × 10−6
, for PCz, PCz/TW20, PCz/CTAB and PCz/SDS, respectively. In this case, the maximum electrical conductivity was achieved for PCz/CTAB formulation. They observed that the electrical conductivity depends of the packaging capacity of the PCz particles. The particle size obtained was 3213 ± 944, 1182 ± 327, 2068 ± 455, and 2841 ± 835 nm for PCz, PCz/TW20, PCz/CTAB, and PCz/SDS, respectively. That is, a smaller particle size provides higher packing that provides higher surface area for electron transfer. PCz/CTAB presented the highest conductivity due its high packaging. However, in the case of neutral surfactant, even if the particle size was small, the surface seems to be not adequate to obtain good electrical conductivity compared to other formulations. Moreover, the materials were doped with HClO4
at different ratios. Overall, an important increase on the electrical conductivity was observed for all the materials. Moreover, it is important to notice the maximum value obtained for PCz/CTAB doped at 1:50 PCz:HClO4, in which the electrical conductivity reached 11.3 ± 0.36 S.cm−1
In 2011, Gupta et al. [104
], reported the fabrication of PCz/gold nanoparticles nanocomposite by chemical synthesis using gold (III) chloride hydrate (HAuCl4
) as an oxidizing agent by two different techniques: emulsion and interfacial polymerization. In the proposed mechanism, the synthesis of both PCz and gold nanoparticles undergoes in cooperation, Au+3
is reduced to Au0
, whereas, the monomer is oxidized, that is, gold nanoparticles are formed simultaneously to the PCz polymerization. The product was obtained as a green powder with 85% and 75% yields for emulsion and interfacial polymerization, respectively, after 24 h of polymerization in dichloromethane. It is interesting to notice that UV–Vis spectra and Fourier-transform infrared (FTIR) spectra revealed the charge transfer between the polymer matrix and nanoparticles and interaction (Figure 7
), indicating that this metal-polymer hybrid nanomaterial had improved technologically useful properties for molecular electronics system.
In addition, others oxidizing agents, such as anhydrous ferric chloride (FeCl3
), have been also used in the synthesis of PCz. Polycarbazole was synthesized with FeCl3
oxidation in chloroform at room temperature for 24 h. A green precipitate was collected, and washed in order to remove the Fe moieties, being the polymerization yield 80% ± 2% [105
]. However, despite an intensive cleaning of the resulting product, iron moieties are still present in the polymer. The hypothetical interaction between iron and polymer could be based on two different assumptions. So, metallic moieties could be trapped in bulk polymer or cationic ions could be coordinated with the nitrogen of the carbazole. On the other hand, these moieties could affect positively to this polymer properties since this PCz presents higher affinity for proton that could be related to the presence of Fe ion. Due to this proton affinity, PCz with iron moieties could be used in sensors [105
A comparative study in terms of the structural, thermal, morphological, and electrochemical properties of polycarbazole (PCz) synthesized by controlled interfacial polymerization using two different oxidizing agents, ammonium persulfate (APS) and potassium permanganate (KMnO4
) has been reported by Kumar et al. [106
]. The polymerization was carried out in the dark at room temperature in dichloromethane for 24 h, with good yields for PCz–APS and PCz–KMnO4
, 82% and 75%, respectively. In this work, electrochemical impedance spectroscopic studies of both polymers were carried out in order to analyse their charge-transfer properties in the vicinity of modified PCz/glassy carbon (GC) and PCz/ Pt electrodes. Two supporting electrolytes were used in this study, namely 0.1 M tetraethylammoniumtetrafluoroborate (TEATFB) and 0.1 M tetraethylammonium-p-toluene sulfonic acid (TEA-p-TSA). Figure 8
shows the EIS response obtained for this study, in the form of a Nyquist plot. The comparison between the synthesized polymers indicates that PCz–APS presents better electron transfer kinetics compared to PCz–KMnO4 at either electrode (GC) or (Pt).
2.2. Electropolymerization of Carbazole and Its Derivatives
Conductive polymers could be directly synthesized in their doped conductive form from their monomer by an anodic or cathodic reaction. However, anodic polymerization is still the most widely used method. This method offers several advantages, it does not require the addition of catalyst in the electrolytic medium, so it could be considered a clean method and it does not require passage through a halogenated substrate (direct grafting of polymer on a substrate). Generally, this technique consists on the deposition of a polymer film by oxidation, that is, an anodic polymerization on the surface of an electrode of noble metal (gold, platinum) or other conductive materials such as glassy carbon or ITO (indium tin oxide) (Figure 9
On the other hand, cathodic polymerization is less implemented than the anodic oxidation method. It consists of two successive electrochemical reactions, followed by a chemical reaction that requires a catalyst such as nickel [109
]. The material deposited on the electrode is obtained in the neutral state, therefore non-conductive, which could inhibit the reaction and requires to regenerate the active surface by doping the polymer [110
Films obtained by electrochemical polymerization are films with better-defined and controlled properties and structure. The electrochemical polymerization has been widely used in recent years for the synthesis of insulating or semi-conductive polymers. This technique presents several advantages, such us homogeneity, relative ease of processing, and obtaining films with controllable and reproducible thickness and structure. It is also important to notice that these polymer thin films are usually difficult to prepare due to their low solubility in solvents [113
Electrochemical oxidation of carbazole proceeds in a similar way to chemical oxidation but seems to be more selective. The first and most significant study on the electrochemical oxidation of carbazole was published by Ambrose and Nelsonin in 1968 [115
Ates and Özyılmaz [49
] conducted systematic study of corrosion performance of polycarbazole (PCz) and PCz derivatives. In their study, films of PCz, and two nanocomposites of nanoclay and zinc nanoparticles were developed. Films were chemically and electrochemically deposited on a stainless steel (SS304), and their anticorrosive properties were tested against 3.5% NaCl solution by EIS and potentiodynamic polarization curves. Carbazole was electropolymerized by chronoamperometric technique on an SS304 electrode for 3600 s in an oxalic acid/acetonitrile solution. In addition, the chemical polymerized carbazole was carried in acetonitrile using cerium ammonium nitrate (CAN) as initiator for 6–8 h at room temperature. This study showed that PCz, PCz / nanoclay and PCz / nanoZn films obtained using chemical method coated on SS304 electrodes displayed better corrosion protection performance compared to the films obtained by the electrochemical method. For chemically technique, PCz films, the highest protection efficiency (PE = 99.81%) has been obtained.
Srivastava et al. [51
] reported PCz electropolymerization and deposition on ITO-coated glass. A study of polycarbazole films prepared on the different metal contacts, such as Aluminium, Copper, and Tungsten, was also carried out for the fabrication of Schottky diodes. PCz was synthesized by oxidative polymerization of carbazole in dichloromethane and as an oxidant tetrabutylammonium perchlorate (TBAP) in an electrochemical workstation. The polymerization of carbazole requires a low anodic potential (1.3 V) to be oxidized. The electrodeposition was prepared in a similar way. The metal contact was deposited in a previously fabricated PCz/Ito films by vacuum thermal evaporation deposition. Authors reported the fabricated diodes presented reasonably good performance rating parameters, showing the ITO/PCz/W device exceptionally good barrier height (0.95) and reverse saturation current density (J0
) of 1.312 × 10−13
To the best of our knowledge, only few samples of PCz and biopolymer composites have been reported until date. Kayan et al. [107
] reported a study in which a polycarbazole/chitosan composite (PCz/Chi) films were successfully synthesized. The synthesis was carried out by using electrochemical polymerization by depositing on a Pt disk electrode by cyclic voltammetry after 5 cycles in the range of 0.0 V to +1.6 V in acetonitrile solution and 0.1 M lithium perchlorate as a supporting electrolyte. The composites were obtained by a similar procedure, adding solution of chitosan at different concentrations. Authors reported an increase the electrical conductivity of the films increase with the presence of chitosan. On the other hand, EIS measurements indicated that small amount of chitosan could enhance films conductivity by easing electron transfer.
2.3. Polymerization of N-Substitution Carbazoles
Poly(N-vinylcarbazole) (PVK) is one of the most interesting polymers based on N-substituted of carbazole due to its wide applications and its excellent thermal stability, doping behaviour, and UV durable property [77
]. However, PVK present poor processability due to the π−π electron system along its backbone reducing its stability versus oxidation, which reduces the conductivity of the polymers [116
]. In order to reduce these disadvantages, carbazole-based monomers have been modified. The substitution at N-position with a wide variety of functional groups could provide carbazole derivatives with improved properties such as solubility, better thermal stability, electrical, photoelectric, ion exchange and other physicochemical properties [118
]. The improvement on their properties wides the applicability of these materials [120
The polymerization N-vinylcarbazole (NVK) was reported for the first time by Reppe and co-workers in 1934 [122
]. N-vinyl carbazole polymerization (NVK) is extensively investigated and many methods have been used, such as free radical [123
], cationic polymerization [124
], anionic polymerization [125
], atom transfer radical polymerization (ATRP) [126
], reversible additional fragmentation chain transfer (RAFT) polymerization [127
], nitroxide-mediated polymerization (NMP) [128
], charging transfer [129
], electrocuting [129
], solid state polymerization [130
], and organometallic-mediated radical polymerization [131
More recently, Marimuthu and Murugesan [132
] reported an efficient and facile polymerization of N-vinyl carbazole (NVK). 1,4-bis (triethyl methyl ammonium) benzene dibromide (TEMABDB) was used as multi-site phase transfer catalyst (MPTC) and potassium peroxydisulphate (PDS) as water soluble initiator at 40 ± 2 °C in two phase system (cyclohexane/water) with ultrasound condition (45 kHz/550 W) and silent. The polymerization rate for this system was significantly increased when ultrasound was used.
Frau et al. [133
] reported the development of a conjugated polymer network (CPN) based on PVK to fabricate anticorrosion coatings. Electrochemical deposition on steel and ITO substrates by both potentiostatic and potentiodynamic methods were used. Anodic oxidation of the carbazole functional groups was used to prepare a cross-linked macromolecular structure (Figure 10
). The electrodeposition of a PVK in dichlorometane was carried out on a potentiostat with a Pt wire as a counter electrode, nonaqueous Ag/AgCl electrode (0.1 M in acetonitrile) as a reference electrode, and, finally, steel or ITO films as working. A step of 1.2 V for 1000 s was induced for the potentiostatic deposition, whereas potentiodynamic deposition was carried out by cycling the potential between 0 and 1.4 V and a rate of 50 mV s−1
for 20 cycles. Morphological studies indicted a higher roughness on the substrates after a potentiostatic deposition compared to potentiodynamic deposition. In addition, the EIS results demonstrated that the PVK coating present good ion transport blocking properties, according to accelerated corrosion tests. Moreover, they showed efficient corrosion resistance on steel coupons used as a model metal substrate.
Selection of the appropriate monomer and the right polymerisation techniques are crucial considerations for materials with excellent gas-uptake capacities. In this context, conjugated microporous polymers (CMP) have arisen as very promising type of microporous organic polymers (MOP). Huang et al. [134
] reported two simple strategies (name in their work as path (1) and path (2)) for the preparation of CMPs based on N-vinyl carbazole derivatives. Four different derivatives (P1 to P4) were synthesised by combining both free radical polymerization and oxidative FeCl3
polymerization (Figure 11
). The oxidative polymerization was performed at ambient temperature in chloroform using FeCl3
as oxidizing agent for 24 h. On the other hand, the free radical polymerization was carried out by using 2, 2′-azobisisobutyronitrile (AIBN) as initiator in toluene at 70 °C for 6 h. The effects of synthetic methods and sequences on the performance as CMP were evaluated. The BET surface area of the polymers was determined. In path 1, the BET obtained for P2 (878.46 m2
) was significantly higher than that of P1 (68.65 m2
). However, in path 2, the values obtained for both polymers were similar, being 621.18 m2
and 660.62 m2
for P3 and P4, respectively. The gas uptake results evaluated for the absorption of carbon dioxide (CO2
), methane (CH4
), and hydrogen suggested that P2 presents the best performance, that is, path 1 was the most appropriate method to obtain N-vinyl carbazole-based CMPs.
In recent years, graphene has attracted tremendous attention due to its properties and versatility, being used in ON and OFF for memory devices or conducting nanocomposites, among others [135
]. Santos et al. [136
] reported the preparation thin films of poly(N-vinylcarbazole)-GO (PVK-GO) nanocomposites via electrodeposition by cyclic voltammetry (CV) on bare ITO by repeatedly scanning the potential between 0 to 1500 mV at a scan rate of 10 mVs−1
for 50 cycles. The nanocoposite was crosslinked due to the electropolymerization process of the carbazole side groups of PVK. This improved the stability of the nanocomposites to several solvents such as 2-pyrrolidone and N-methylpyrrolidone, close to 30 days.
Similarly, Wang et al. [137
] synthesized poly(9-vinylcarbazole)/silver nanocomposites by in situ formation of silver nanotubes and networks formed at the air–water interface via the reduction of Ag+
ions. The structures of the silver nanotubes were strongly dependent of the experimental conditions such as temperature.
The stability of the redox states is the most suitable property for an electro-active polymer to be useful in building new electrochromic device [138
]. Furthermore, the ability of a material to demonstrate a significant colour shift is important to electrochromic applications. Kocaeren [142
] reported the synthesis of carbazole derivatives with electrochemical and electrochromic properties to be used electrochromic devices (ECDs). Firstly, bis-4-(9H-carbazol-9-yl) phenyl-3,4-diyloxy thiophene (B1) was synthesized from the reaction of 4-(9H-carbazol-9-yl) phenol and 3,4-dibromo thiophene in the presence of potassium carbonate (K2
) in tetrahydrofuran (THF). After that, the polymer of B1 was deposited onto an ITO-glass surface by oxidative electrochemical polymerization (Figure 12
). The electropolymerization was performed on a potentiostat in acetonitrile, using Pt wire as counter electrode, Ag wire as reference electrode and ITO as working electrode, scanned from +0.3 to +1.4 V. The presence of the polymer was evidence due to the increase of a peak in a cyclic voltammetry at 0.95 V. It is important to notice that the polymer film presents a blue colour between 1.0 and 1.4 V due to its oxidation, whereas its colour turns into a light yellow between 0.5 and 0.9 V owning to its reduction. The maximum absorbance wavelengths were 320 and 670 nm. This carbazole derivative, which presents high stability, could be used in electrochromic devices (ECDs) according to redox stability measurements.
Another example of electrochromic carbazole derivative was synthetized by Hsiao and co-worker [143
]. In their study, two previously synthesized carbazole-based monomers were successfully electrodeposited and polymerized onto the ITO electrode by electropolymerization. 4,4′-di(carbazol-9-yl)-4″-methoxytriphenylamine (TPA-2Cz) and 3,6-di(carbazol-9-yl)-N-(4-methoxyphenyl)carbazole (PhCz-2Cz). The electropolymerization onto an ITO (working electrode) of the monomers was carried out with a polymer and 0.1 M Bu4
solution in dichloromethane and ITO as working electrode by several cycles between 0 and 1.4 V at a scan rate of 50 mV s−1
. P(PhCz-2Cz) (Figure 13
a) present a blue-green colour in its maximum oxidation state around 1.28 V. This film changes to yellow (1.07 V) and finally, colourless at 0.0 V. Similarly, P(TPA-2Cz) presents a brown colour at its fully oxidized state and dark green colour at semi-oxidized states.
The same strategy was used in other work of Hsiao and Lin [141
] in which poly(amide-carbazole) and poly(imide-carbazole) were used for the development of two series of diamide-cored carbazole dendrons (6CzR-DA) and diimide-cored carbazole dendrons (6CzR-DI). These monomers series were synthesized from condensation reactions of 3,6-di(carbazol-9-yl)-N-(4-aminophenyl)carbazole (NH2
-3Cz) with aromatic dicarboxylic acids and tetracarboxylic dianhydrides, respectively. Similar to their previous work, these polymer films showed good electrochemical and electrochromic properties.
Yang and co-workers [144
] performed a study on induced oxidative polymerization of 1,3,6,8-tetrakis(4-(9H-carbazol-9-yl) phenyl)pyrene (L) with FeCl3
as oxidant in anhydrous chloroform for 24 h at 60 °C. This process resulted in the formation of the bulk polymer (Figure 14
), being a highly luminescent conjugated microporous polycarbazole derivative (CK-CMP).
Soganci et al. [48
] reported a novel method for electropolymerization a disulfide-linked N-alkyl substituted carbazole derivative. 1,2-bis[6-(9-carbozol-9-yl)hexyl]disulfane (CS) monomer was synthetized in this work (Figure 15
) and then, electropolymerized using cyclic voltammetry and ITO as working electrode. The electropolymerization process of CS monomer was performed comparatively in the BFEE (Boron trifluoride diethyl etherate) containing solution and BFEE-free electrolytic solutions. This material presents interesting electrochromic properties that could be potentially used in smart window applications, due to the high optical contrast value and stability obtained in BFEE compared to other N-alkyl substituted carbazole appeared in literature.
Duran et al. [145
] successfully deposited a poly(N-methyl carbazole) (PNMeCz) coating on stainless steel type 304. The film was deposited by electropolymerization of N-methyl carbazole (NMeCz) monomer in acetonitrile solution containing tetrabutylammonium perchlorate using cyclic voltammetry and stainless steel as working electrode. The film was electrodeposited applying a potential between +0.5 and +1.7 V with a rate of 50 mV/s during 15 cycles. The resistance to the corrosion was evaluated, demonstrating these films presented good anticorrosion properties.
Elkhidr and co-workers [146
], synthesized and studied different electrochemical and optical properties for three carbazole derivatives with different substitution at N-positions, methanol (carbazol-9-yl-methanol), carboxylic acid (carbazol-9-yl- carboxylic acid) and cyanoethyl (carbazol-9-yl-cyanoethyl). Polymeric films of these derivatives were obtained (PCz−OH, PCz−COOH, and PCz-CN, respectively) by the electropolymerization on ITO substrate by repetitive cyclic voltammetry. The electropolymerization was carried out on a potentiostat-galvanostat system, with tree electrodes; the working electrode was ITO, whereas platinum and silver wires were used as counter and pseodoreference electrodes, respectively. A potentiodynamic electropolymerization was performed between +0.0 to +1.6 V with a scan rate of 100 mV/s. The monomer solutions containing NaClO4
electrolyte dissolved in acetonitrile. Polycarbazole presents high solubility problems, being almost insoluble in most of inorganic solvent and soluble in only few organic solvents. However, the polycarbazole derivatives reported in this work showed a good solubility in common organic solvents such as dimethyl sulfoxide (DMSO), N-methyl-2-pyrrolidone (NMP), tetrahydrofuran (THF), and dimethylacetamide (DMAC). The colour variations induced by the redox switching of the carbazole derivatives during the electrochemical process are summarized in Figure 16
, where L is the luminance or brightness, a is hue and b is the saturation using the International Commission on Illumination (CIE) system.
Qin et al. [147
] reported the successful synthesis of conjugated network based on poly(ethylenoxide) grafted carbazole. In their study, first poly(N-epoxypropyl carbazole) (PEPC) was obtained by anionic ring-open polymerization of N-epoxypropyl carbazole (EPC) using potassium hydroxide and 18-crown-6 in toluene at 90 °C for 12 h. After obtaining PEPC, a conjugated network was fabricated by electrodeposition of poly[poly(N-epoxypropyl carbazole)] (PPEPC). The electropolymerization was carried put in a potentiostat using Pt wire as counter electrode and stainless steel and Pt sheets as working electrodes on which the polymer was deposited. A scheme of the complete synthetic process carried out in this work is depictured in Figure 17
. The synthesized PPEPC showed favourable thermal stability and strong mechanical properties, and can be easily bent or cut into different forms.