PNCPy was prepared by anodic polymerization and its properties in both doped and undoped state were characterized. The doping level of the oxidized material has been found to be larger than that of other conducting polymers; the more relevant electrochemical properties of the doped material were retained after undoping. SEM and AFM data are consistent with a lumpy surface and a multidirectional growing of the polymer chains. Finally, PNCPy has been combined with PEDOT to prepare three‐layer systems with enhanced electroactivity and electrostability. Results suggest that PNCPy is a potential candidate for the fabrication of electric circuit components that are able to block the current flow below a given potential.
New polyhydrazides and poly(amidehydrazide)s bearing redox‐active carbazole and triphenylamine units were prepared. The resulting poly(1,3,4‐oxdiazole)s and poly(amide‐1,3,4‐oxadiazole)s had high glass‐transition temperatures (288–330 °C) and high thermal stability. The dilute solutions of all the hydrazide and oxadiazole polymers showed a weak–medium photoluminescence with emission maxima around 474–506 nm. The polymer films revealed two well‐defined and reversible redox couples upon electrochemical oxidation, together with interesting electrochromic behaviors. They showed enhanced redox‐stability and electrochromic performance. CV of the oxadiazole polymers also showed reduction processes due to the formation of radical anions of the oxadiazole units.
Summary: New alternating copolymers based on indolocarbazole (IC), both two‐ and three‐coupled, and bithiophene (BT) or bis(3,4‐ethylenedioxythiophene) (BiEDOT), were obtained using Stille or Suzuki coupling reactions. Those copolymers have been investigated by cyclic voltammetry, electrochemical quartz crystal microbalance, in situ electron spin resonance, in situ conductivity, and UV‐Vis‐NIR spectroelectrochemistry techniques. All polymer films undergo reversible oxidation processes. One to three isoelectronic oxidation processes, involving one electron per repeat unit, produce radical cations, dications, and radical trications. The oxidative charge is localized in the IC moiety for BT copolymers or over the whole polyconjugated backbone for BiEDOT copolymers. Redox neutral‐polaron conductivities are in the range of 0.02–0.1 S · cm?1 and polaron‐bipolaron conductivities in the range of 0.1–0.7 S · cm?1.
Two types of N‐substituted pyrroles with azide and terminal alkyne groups have been synthesized and electropolymerized. “Click” chemistry, specifically Huisgen 1,3‐dipolar cycloaddition, was used as a general method for functionalization of the polypyrrole films. Several model compounds, including redox active (quinone), bioactive (cholic acid) and recognition elements (carbohydrate and thymidine) could easily be attached onto the electrode surfaces without loss of functionality or the electroactivity of the underlying conducting polymers. The results suggest that the polypyrrole films are clickable and provide a novel biocompatible and versatile platform for efficient modifications on electrode surfaces.
Polymerization of methylbutyl‐2‐(3‐thienyl)acetate (MBTA) was achieved by constant current electrolysis at low temperature. Subsequently, the syntheses of block copolymers of polyMBTA were accomplished in the presence of either pyrrole or thiophene by constant potential electrolysis. Moreover, the copolymer of MBTA with thiophene was obtained with constant potential electrolysis.
Summary: For the development of n‐channel field‐effect transistors it is indispensable to look for semiconducting polymers with electrons as majority charge carriers (n‐type). In addition high electron mobility values are of significant advantage in these compounds. Polymers with electron transporting properties have been rarely investigated. Main chain polymers with strong acceptor units like 1,2,4‐triazoles‐4H are potential candidates for electron transporting materials in electronic devices. Therefore, a synthetic pathway leading to an organo‐soluble polymer consisting only of 4‐hexyl‐1,2,4‐triazole‐4H units in the main chain is presented in this work. We will report the synthesis using modified classical polycondensation. The chemical and electronic properties of the polytriazole have been investigated in detail. The material has been used to prepare “electron‐only” devices for the calculation of the electron mobility.
The suggested chemical structure of poly(4‐hexyl‐1,2,4‐triazole‐4H) (PHTA). 相似文献
The preparation of poly[2,6‐(1,4‐phenylene)‐benzobisimidazole] (PPBI) nanofibers was examined using the crystallization of oligomers during isothermal polymerization of self‐polymerizable 2‐(1,4‐carbophenoxyphenyl)‐5,6‐diaminobenzimidazole. The polymerization was carried out at 350 °C at a concentration of 1wt.‐% for 6 h in three kinds of solvent. The solvent influenced the morphology of PPBI precipitates significantly, and PPBI nanofiber networks were successfully formed in DBT, of which the width ranged from 30 to 110 nm. Molecules were aligned along the long axis of nanofibers. A fibrillar morphology with molecular orientation is ideal for high performance materials such as reinforcements, non‐woven fabrics and so on. The nanofiber networks exhibit the highest thermal stability.
As proton‐conducting polymers, phosphonic acid functional polymers are commonly preferred due to their high proton conductivity in humidified and anhydrous systems. In this work, a new copolymer based on 4‐vinyl benzene boronic acid (VBBA) and vinyl phosphonic acid (VPA) is synthesized and then boronic acid groups are grafted with polyethylene glycol methyl ether to produce more‐flexible materials. The reactions are verified by FTIR spectroscopy and thermal analysis (thermogravimetric analysis (TGA) and DSC). The P content of the samples is analyzed by scanning electron microscopy (SEM)–energy dispersive X‐ray spectrometry (EDS). The ion‐exchange capacity (IEC) of the copolymers is measured and compared with the P content. The proton conductivity is investigated in both humidified conditions and the anhydrous state. In 50% humidity, P(VBBA‐co‐VPA)1:0.5 shows a proton conductivity of 5.3 × 10?3 S cm?1 at 30 °C. 相似文献
A series of conjugated polymers (PDTP, PDTPT, PDTPTT) based on dithieno[3,2‐b:2′,3′‐d]pyrrole (DTP) containing branched side‐chains is synthesized. The synthesized polymers show good solubility due to branched side‐chains in the organic solvent in the absence of heat treatment. To increase the oxidation potential, unsubstituted thiophene units are introduced into the polymer backbone. The introduction of unsubstituted thiophene units increases the oxidation potential, elevates degradation temperature, and enhances electronic properties. The PDTPTT FETs show the highest charge‐carrier mobility among the three polymers. These polymers are used as a donor material in bulk heterojunction solar cells, and the PDTPTT photovoltaic cells exhibit high performance. 相似文献
Aqueous self‐assembly of thermosensitive triblock copolymers based on poly(N‐isopropylacrylamide) and poly[2‐(methacryloyloxy)ethyl phosphorylcholine] (PNIPAMm–PMPCn–PNIPAMm and PNIPAMm–PMPCn–S–S–PMPCn–PNIPAMm) were studied using light scattering (SLS and DLS), TEM and fluorescence experiments. These techniques were used to investigate the morphological transition as a function of the temperature, below and above the LCST of the PNIPAM, at various triblock copolymer concentrations ranging from dilute to semi‐dilute regimes. Below the LCST and at low concentrations, aqueous solutions show micellar behavior, while above the LCST self‐assembly leading to large nanoparticles stabilized with PMPC chains. Such behavior is the onset of a gel‐like phase transition observed at higher concentrations.
This work describes the effect of sulfuric acid protonation on the properties of SPOD‐DPE membranes using FT‐IR and impedance spectroscopic analyses. The IR spectra showed the protonation of nitrogen atoms from oxadiazole rings, with a broad band complex in the region 3 000–2 100 cm?1 with two centered peaks at 2 590 and 2 440 cm?1. The S?O characteristic absorption bands in SPOD‐DPE and sulfuric acid were specially studied in the region of 1 800–900 cm?1. The band shifts are associated to the interaction between acid groups and oxadiazole ring nitrogen atoms. The IR spectra evidenced the presence of three absorption species (HSO, SO and free H2SO4) depending on the sulfuric acid concentration. For the protonated SPOD‐DPE membranes, a proton conductivity around 10 mS · cm?1 was reached at 50 °C.
Two novel reactive poly(β‐cyanoethylsilsesquioxane) ( CN‐T ) and poly[(β‐cyanoethylsilsesquioxane)‐co‐(β‐methylsilsesquioxane)] ( CN‐Me‐T ) have been synthesized successfully for the first time via stepwise coupling polymerization (SCP). A variety of characterization methods including FTIR, 1H NMR, 29Si NMR, X‐ray diffraction (XRD), differential scanning calorimetry (DSC) and vapor pressure osmometry (VPO) were combined to demonstrate that the structures of the title polymers possess ordered ladder‐like structures. As expected, the ionic conductivity of these polymers mixed homogeneously with lithium perchlorate reached 10?6 S · cm?1 at room temperature and obviously increased with the raise of temperature.
A series of coumarins were reacted with methacrylate or styrene derivatives to form new olefinic coumarin monomers that were polymerized using 2,2′‐azoisobutyronitrile (AIBN). These polymers were highly insoluble in organic solvents and displayed good thermal stability with glass‐transition temperatures between 70 °C and 130 °C. Luminescence studies on some of the coumarin‐containing polymers (CCPs) showed some fluorescence (ΦF around 0.1). Some of the newly‐prepared coumarins and benzocoumarins were reacted with azo dyes to form mixed coumarin‐azo dye complexes. These mixed complexes were further reacted to prepare acrylic monomers and polymerized using AIBN. These polymers were thermally stable and poorly soluble in organic solvents.
Polymeric positive temperature coefficient (PTC) materials can be used to install “brake” technology for the thermal runaway of lithium‐ion batteries. However, it still has poor cycle stability and obvious negative temperature coefficient (NTC) effect, which reduces the reliability of the material. In order to solve these problems, conductive polymer poly(3,4‐ethylenedioxythiophene) (PEDOT) modified multilayer graphene (MLG) conductive additive (PEDOT‐MLG) is introduced into middle density polyethylene/carbon black (MDPE/CB) system. Compared with the conventional modification, the PEDOT modified MLG shows high conductivity and excellent thermal stability. In addition, the introduction of PEDOT‐MLG into MDPE/CB can further reduce the room temperature resistivity due to the good compatibility between the modified graphene and the matrix, thus improving the PTC intensity to 7.1. What is more, MLG limits the re‐aggregation of CB particles when the temperature further rises, which effectively weakens the NTC effect. 相似文献
Monomers containing N,N ′,N,N ′‐tetraphenylbenzidine (TPD) were prepared by introducing two alkyl or alkoxy substituents into the p‐position of two of the four phenyl groups in the triphenylamine unit. The monomers were copolymerized with 1,4‐divinylbenzene (DVB) in the presence of p‐toluenesulfonic acid and Lewis acids, such as SnCl4 and BF3. The polymerization conditions and the catalyst types showed a marked influence on yield, molecular weight and even polymer structure. 1H NMR measurements revealed that, by using p‐toluenesulfonic acid as a catalyst, the linkage between the TPD unit and DVB occurs at the p‐position of the phenyl group and at the m‐position of the tolyl group in the TPD unit, whereas, with SnCl4 or BF3 catalyst, substitution occurs exclusively at the p‐position of TPD. All polymers are soluble in common organic solvents, which allows the preparation of thin films of good quality. The rigid structure of the polymeric backbone results in a high thermal stability up to 400°C. The results of ionization potential measurements and the redox behavior showed that the introduction of the TPD unit into this kind of polymer backbone does not change its electronic structure. On the basis of high electroactivity, the polymers were successfully used as hole transport layers in two‐layer electroluminescence devices. 相似文献
Summary: The complexation of saccharides with poly(anilineboronic acid) as a function of pH has been studied with simultaneous measurements of open‐circuit potential and mass change. This study provides an insight into this reaction as well as the relationship between complexation and open‐circuit potential and the optimum pH for complexation of D ‐fructose and D ‐glucose. The optimum pH values for poly(anilineboronic acid)‐D ‐fructose and ‐D ‐glucose complexation are near the pKa values of the complex reported in homogeneous solution. At physiological pH (7.4), the apparent binding constant of D ‐fructose and D ‐glucose with poly(anilineboronic acid) is 19.2 and 0.2 M ?1, respectively. In contrast, at pH 9.0, the apparent binding constant of D ‐glucose with poly(anilineboronic acid) is 12 M ?1, double than that of D ‐fructose. The decrease in complexation in the polymer films at pH values above the pKa of the complexes is in contrast to the behavior in homogeneous solutions. This trend is observed for both D ‐fructose and D ‐glucose using open‐circuit potential, mass change and polarization modulated infrared reflection absorption spectroscopic measurements. Also, the complexation is limited in the polymer film, i.e., ≤23% boron is involved. These results suggest that steric and/or electrostatic interactions may play an important role in complexation within polymer films.
The influence of the doping level in the formation of specific interactions between plasmid DNA and PEDOT is investigated using experimental assays and theoretical calculations. Electrochemical methods are used to prepare polymer samples with oxidation degrees ranging from 0.14 to 1.05 positive charges per repeating unit. A combination of experimental and theoretical results are used to propose a mechanism for the formation of DNA/conducting polymer complexes, which consists of the initial stabilization of the adducts through non‐specific interactions followed by small structural re‐arrangements that allow to be established specific hydrogen bonds involving the polar groups of the conducting polymer and selected DNA bases.
Cross‐linked poly(3,4‐ethylenedioxythiophene) (PEDOT) films were synthesized by the oxidative polymerization of 3,4‐ethylenedioxythiophene in the presence of five different conjugated and non‐conjugated cross‐linkers. The concentration and structure of the cross‐linker was systematically varied to explore the influence on the electrical conductivity. Optimized compositions displayed an electrical conductivity of up to ≈800 S · cm?1; this corresponds to a conductivity increase of up to 36% compared to linear PEDOT prepared under identical conditions. An increase in the conductivity was only observed for the conjugated cross‐linkers that were incorporated in low concentrations, typically at a level of less than 2 mol‐%. Attempts to incorporate higher concentrations of cross‐linker led to phase separation and crystallization of the cross‐linker and afforded materials in which a significant reduction of the electrical conductivity was observed. The optical properties of the polymer were only marginally affected upon cross‐linking, even at high cross‐linker concentrations.
1,2,4‐triazole‐functional PGMA polymers have been synthesized and their anhydrous proton‐conducting properties were investigated after doping with phosphoric acid and triflic acid. PGMA was prepared by solution polymerization and then modified with 1H‐1,2,4‐triazole (Tri) and 3‐amino‐1,2,4‐triazole (ATri). FT‐IR, 13C NMR and elemental analysis verify the high immobilization of the triazoles in the polymer chain. Phosphoric‐acid‐doped polymers showed lower Tg and higher proton conductivities. PGMA‐Tri 4 H3PO4 showed a maximum water‐free proton conductivity of approximately 10?2 S · cm?1 while that of PGMA‐ATri 2 H3PO4 was 10?3 S · cm?1. The structure and dynamics of the polymers were explored by 1H MAS and 13C CP‐MAS solid‐state NMR.
Summary: A new series of side‐chain liquid‐crystal polymers, the poly[1‐({[(4‐cyano‐4′‐biphenyl)oxy]alkyl}oxy)‐2,3‐epoxypropane], has been synthesized in which the spacer length is varied from 2 to 8 methylene units. The synthesis used for the chemical modification of polyepichlorohydrin (PECH) involved the phase transfer catalyzed etherification of the chloromethyl groups with sodium 4‐cyano‐4′‐biphenoxide and lithium n‐(4‐cyano‐4′‐oxybiphenyl)‐alkanoates. All the resulting polymers (except polymers 7 and 8), including that without spacer, characterized by 1H NMR, and IR, exhibit thermotropic liquid crystalline mesomophism. The thermal behavior of the polymers has been characterized using differential scanning calorimetry (DSC) and polarized light microscopy (POM) equipped with hot‐stage. A more pronounced odd‐even effect in the clearing temperatures is observed on increasing the spacer length in which the odd members display slightly higher values, which were also dependent on the substitution degree of PECH. The flexible PECH chain assists nematic LC formation compared with other more rigid backbone polymers where a smectic phase is often encountered with the same mesogen. A comparison of the thermal properties of the cyanobiphenyl based series reported here. Polyacrylate (PA) and poly(methacrylate)‐based (PMA) SCLCPs containing 4‐cyanobiphenyl as the mesogenic unit are consistent with the general rule that increasing backbone flexibility for a given mesogenic unit and spacer length enhance the clearing temperature. This was not found from the PECH‐based series, which show the lower clearing temperature than the PMA and PA series, even though they have more flexible backbone than PA and PMA series. So the clearing temperature is not solely determined by the flexibility of the backbone.
Schlieren textures of PECHOC2‐B taken at 110 °C (cooling from isotropic phase after annealing 1 h). 相似文献
