Strong Polar Organic Solvents Research Articles

Macromolecular grafting of carboxyl polymers on the surface of non-woven fabrics and their adsorption behavior on metal cations

In order to address the issues of the time-consuming, the low density of functional groups and the instability of mussel-inspired adsorbents, an efficient in situ cross-linked mussel-inspired coating-assisted macromolecular grafting strategy was proposed to prepare a polyacrylic acid (PAA) grafted polypropylene nonwoven (PP-g-PAA) for the efficient removal of heavy metal ions. The mussel-inspired coating was formed by rapid deposition in the presence of oxidizing agents and polyamines, and then thiol-terminated polyacrylic acid (PAA-SH) prepared by thiol-ene click reaction and glutaraldehyde were added in situ, and then PAA brushes were introduced on the surface of the polypropylene nonwoven via the Michael addition Schiff base reaction between the thiol and o-benzoquinone, and the improvement of the stability of the adsorbent was achieved through in situ formation of the three-dimensional cross-linked structure. A high density carboxyl group functionalized adsorbent with a grafting rate up to 38.98% was obtained, which also exhibited unprecedented tolerance to strong acid, alkali and polar organic solvents. Meanwhile, grafting on polyester nonwovens, sponges and PVDF membrane substrates confirmed the versatility of the proposed method. The PP-g-PAA was characterized by SEM, IR and XPS, and the adsorption behaviors of the adsorbent for Pb2+, Cu2+ and Cd2+ were systematically investigated. The results showed that the adsorption capacity of PP-g-PAA was nearly twice as high as that of the mussel-inspired adsorbent. The adsorption mechanism was also well investigated.

Polyoxometalate-modified halloysite nanotubes-based thin-film nanocomposite membrane for efficient organic solvent nanofiltration

Polyoxometalate-modified halloysite nanotubes (POM@MHNTs) were synthesized and doped into the polyamide (PA) matrix by interfacial polymerization to prepare doped POM@MHNTs thin-film nanocomposite (TFN) membranes for organic solvent nanofiltration (OSN). Likewise, thin-film composite (TFC) and TFN membranes doped with HNTs were fabricated. It is worth noting that the methanol flux of the TFN can be efficiently enhanced by tuning the contents of POM@MHNTs. The as-synthesized optimal sample (TFN-0.10) exhibits superior methanol flux of TFN-0.10 membrane of 14.80 L m−2 h−1 bar−1 (1.76 times of that of undoped TFC membrane and 1.12 times of that of doped HNTs membrane (TFN-HNTs-0.10). These are mainly due to the tubular structure of POM@MHNTs providing additional solvent transfer channels and the ridge-valley morphology of the membrane surface increasing the contact area between the membrane and the solvent. Meanwhile, the POM@MHNTs nanohybrids are similarly electrostatically attracted by the amide groups on the polyamide chains produced by interfacial polymerization, improving the compatibility of POM@MHNTs with polyamide membranes. TFN-0.10 OSN membrane showed stable chemical properties in medium polar organic (methanol, ethanol, THF), acid polar organic (acetonitrile), and strong polar organic (DMF) solvents. Prepared TFN OSN membranes exhibited strong long-term operation capability and organic solvent resistance after 80 °C DMF immersion for 7 days with inconspicuous separation performance changes. This work offers the prospect of using organic-inorganic hybrid modified nanomaterials to improve OSN performance.

High flux thin film composite (TFC) membrane with non-planar rigid twisted structures for organic solvent nanofiltration (OSN)

Organic solvent nanofiltration (OSN) has become an emerging green and efficient technique for the separation and purification of organic solvents. The key of the industrial application of this technique is OSN membrane. Till now, current OSN membranes still have relatively low solvent permeance due to the high hydraulic resistance of the dense structure of the OSN barrier layer. Herein, a thin-film composite (TFC) polyamide-polyarylate OSN membrane containing polymers of intrinsic microporosity (PIMs) structure was successfully prepared via interfacial polymerization (IP) using a kind of hydrophilic monomer with rigid twisted structure as aqueous co-monomer together with m-phenylenediamine (MPD). The added co-monomer remarkably enhanced the perm-selectivity of the prepared OSN membrane, with an increase of more than 1.5 times for ethanol permeance, while maintaining the rejection of rhodamine B (RDB, 479 Da) above 99% under the optimal conditions. Moreover, the prepared OSN membrane has a much high permeance to polar solvents, e.g., 110.5, 112.6 and 95.8 L m−2h−1 MPa−1, for ethyl acetate, methanol and DMF, respectively. The most exciting aspect of the prepared OSN membrane is its superior solvent resistance in strong polar organic solvent. It maintained an essentially unchanged solute rejection during 63 d immersion in DMF at 80 °C, and during 120 h continuous cross-flow filtration of the RB-DMF solution at room temperature, which is superior over most of the state-of-the-art literature works, indicating its broad application prospects for separation and purification of polar organic solvent systems.

Preparation and Characterization of Water-Insoluble Gardenia Blue Pigment.

Based on molecular simulations, the synthetic route of water-insoluble gardenia blue pigment was prepared by the reaction of genipin and L-Phenylalanine methyl ester hydrochloride. A highly purified pigment was obtained after extraction by chloroform and purification by silica gel column chromatography, and the value of color is up to 288. A study on the structural characteristics of the pigment was implemented with a scanning electron microscope, ultraviolet-visible spectrophotometer, Fourier transform infrared spectrometer, X-ray photoelectron spectrometer, and quatropde-time of flight mass spectrometer. The results showed that the surface of the pigment was largely smooth and spherical; The λmax was 607 nm, and the main functional groups include O-C=O, C=O, C-N, C=C, OH, and benzene ring; We detrained six different molecular weight and chemical structures of pigments and speculated the particular structures and formation mechanisms of three kinds of pigment, whose molecular weights are 690.1156, 720.1226, and 708.1246 Da, respectively. The pigment was only able to be dissolved in ethanol, methanol, acetone, ethyl acetate, and other strong polar organic solvents, but was not able to be dissolved in water, ethyl ether, petroleum ether, and other weak polar organic solvents. In terms of light and thermal stabilities, water-insoluble gardenia blue pigment is significantly better than water-soluble gardenia blue pigment (p < 0.05). When it is under direct light for 7 days or incubated at 80–120 °C for 24 h, the pigment residual rates were 74.90, 95.26, 88.27, and 87.72%, respectively.

Synthesis and characterization of novel soluble poly(arylene ether amide triphenylphosphine oxide)s by heterogeneous palladium-catalyzed carbonylation polymerization

A new aromatic diiodide monomer, bis(4-(3-iodophenoxy)phenyl)phenylphosphine oxide (BIPPO), was prepared by condensation of bis(4-fluorophenyl)phenylphosphine oxide with 3-iodophenol. A series of poly(arylene ether amide triphenylphosphine oxide)s were synthesized via heterogeneous palladium-catalyzed carbonylative polycondensation of BIPPO, aromatic diamines, and carbon monoxide. Polymerization reaction proceeded smoothly in N,N-dimethylacetamide (DMAc) at 120 °C with 1,8-diazabicyclo[5,4,0]-7-undecene (DBU) as the base by using the bidentate phosphino-modified magnetic nanoparticles-anchored palladium complex [2P-Fe3O4@SiO2-PdCl2] as a recyclable catalyst under 1 bar of CO, producing new poly(arylene ether amide triphenylphosphine oxide)s with inherent viscosities ranging from 0.69 to 0.76 dl/g. All the polymers obtained were easily soluble in strong polar aprotic organic solvents and even in less polar pyridine at room temperature, and provided transparent, flexible and tough films by casting from their DMAc solutions. These polymers displayed good thermal stability with the glass transition temperatures ranging from 196 to 249 °C, the temperatures at 5% weight loss ranging from 441 to 490 °C in nitrogen. All the polymers were amorphous and their films showed good mechanical behavior with tensile strengths of 78.5–91.6 MPa, tensile moduli of 2.15–2.69 GPa, and elongations at break of 9.8–14.6%.

Preparation of ionic liquid mediated molecularly imprinted polymer and specific recognition for bisphenol A from aqueous solution

In this paper, an ionic liquid mediated molecularly imprinted polymer (IL-MIP) was prepared, in which synthesis system 1-butyl-3-methylimidazolium tetrafluoroborate (IL) was introduced to improve its selectivity and adsorption for the target. The structures of the prepared materials were characterized by SEM, BET, 13CNMR and FTIR, and the adsorption performance of the resultant IL-MIP for BPA and its analogues (phenol, 4-NP, 4-CAP and 1-naphthol) in strong polar media were investigated in detail. The experimental data showed that the adsorption capacities of IL-MIP and molecularly imprinted polymer (MIP) for Bisphenol A (BPA) were 116.16 mg/g and 87.30 mg/g, with imprinting factor of 3.77 and 2.72, respectively. In addition, several other competitive analogues with different polarities (phenol, 4-NP, 4-CAP and 1-naphthol) were chosen to evaluate the selectivity of IL-MIP and the experimental results demonstrated that the synthesized IL-MIP displayed selectivity toward BPA and against analogue molecules. This work provided a simple and effective method to selectively extract BPA from aqueous medium or strong polar organic solvent.

Two 8-hydroxyquinoline-based fluorescent chemosensors for ultra-fast and sensitive detection of water content in strong polar organic solvents with large Stokes shifts.

It is of great significance to detect the moisture in organic solvents before used in water-sensitive reactions. Herein, two Schiff base quinoline derivatives, 8-hydroxyquinoline-2-carboxaldehyde thiosemicarbazone (HQCT) and 8-hydroxyquinoline-2-carboxaldehyde (pyridine-2-carbonyl)-hydrazine (HQPH), were designed and synthesized by a simple one-step reaction, and used as fluorescent chemosensors for ultra-fast and sensitive detection of water content in strong polar organic solvents. Based on excited-state intramolecular proton transfer (ESIPT) process, HQCT and HQPH exhibited strong fluorescence emissions with large Stokes shifts in dimethyl sulfoxide (DMSO) and N, N-dimethylformamide (DMF) solvents compared to other various organic solvents, and their fluorescence quenching and fluorescent color changes were obviously observed with increasing water content. The experimental results revealed that the hydroxyl groups substituted at the 8-position of HQCT and HQPH played a key role in the fluorescence emission processes. Dynamic light scattering (DLS) and 1H NMR titration indicated that the sensing mechanism for the detection of water was based on inhibition of the ESIPT by H2O via forming hydrogen bonds. In the range of 0.0-1.8wt%, the fluorescence intensity of chemosensors changed as a linear function of water content. The detection limits of water in DMSO by HQCT and HQPH were as low as 0.0220wt% and 0.0274wt%, respectively. Moreover, HQCT and HQPH are successfully applied for the detection of moisture content in real commercial organic solvents.

Study on the structure and properties of PPS/PCNF hybrid membranes and their applications in wastewater treatment

Membrane separation technology is widely used in water treatment. In this paper, we prepared polyphenylene sulfide/porous carbon nanofibers (PPS/PCNF) hybrid membranes by adding PCNF into PPS membranes. In the thermally induced phase separation (TIPS) process, PCNF could migrate to the top surfaces of the hybrid membranes, which made the pore size on the top surfaces of the membranes significantly decreasing and the pore size distribution became narrower. Compared with the conventional surface coating modified membranes, the surface coating material of PCNF would not falling off from PPS membrane, and it made the hybrid membranes to become more hydrophobic and to have the higher breaking elongation. PCNF, as a kind of heterogeneous nucleating agent, increased the melting temperature and the crystallization temperature of PPS/PCNF membrane, which resulted in PPS/PCNF membrane having the higher breaking elongation. Most importantly, PPS/PCNF hybrid membranes had a good intercepting performance, with bovine serum protein (BSA) intercepting rate of 92.7% and dye methylene blue (MLB) intercepting rate of 99.9%. Meanwhile, they also had a good removal effect on bacteria in strong polar organic solvent, and the removal rate achieved 93.7%. Thus, the PCNF hybridized PPS can play a crucial role on wastewater treatment in the future.

Synthesis and properties of novel soluble aromatic polyamides containing 4-aryl-2,6-diphenylpyridine moieties and pendant fluorinated phenoxy groups

Three diamine monomers containing pyridine groups were prepared via the modified Chichibabin reaction of aromatic aldehydes with 4′-nitroacetophenone, followed by reduction with hydrazine hydrate in the presence of Pd/C. Novel aromatic polyamides containing 4-aryl-2,6-diphenylpyridine moieties and pendant fluorinated phenoxy groups were synthesized from these diamines and two fluorinated isophthaloyl dichlorides by the low temperature solution polycondensation in N,N-dimethylacetamide (DMAc). All the polymers are amorphous and readily soluble in strong polar organic solvents such as DMAc, N-methyl-2-pyrrolidinone (NMP), N,N-dimethylformamide (DMF), and dimethyl sulfoxide (DMSO) at room temperature. The resulting polymers showed glass transition temperatures between 270 and 314 °C and 5 % weight loss temperatures ranging from 442 °C to 475 °C, and char yields at 800 °C higher than 53 % in nitrogen. These polyamides could be cast into transparent, flexible and strong films from DMAc solution with tensile strengths of 72.5–87.3 MPa, tensile moduli of 2.35–2.87 GPa, and elongations at break of 5.3–9.5 %. The polyamide films exhibited low dielectric constants of 3.21–3.54 (1 MHz), low water uptakes in the range of 1.17–1.38 %, and high transparency with an ultraviolet-visible absorption cut-off wavelength in the 380–391 nm range.

Sugar-Based Polyamides: Self-Organization in Strong Polar Organic Solvents.

Periodic patterns resembling spirals were observed to form spontaneously upon unassisted cooling of d-glucaric acid- and d-galactaric acid-based polyamide solutions in N-methyl-N-morpholine oxide (NMMO) monohydrate. Similar observations were made in d-galactaric acid-based polyamide/ionic liquid (IL) solutions. The morphologies were investigated by optical, polarized light and confocal microscopy assays to reveal pattern details. Differential scanning calorimetry was used to monitor solution thermal behavior. Small- and wide-angle X-ray scattering data reflected the complex and heterogeneous nature of the self-organized patterns. Factors such as concentration and temperature were found to influence spiral dimensions and geometry. The distance between rings followed a first-order exponential decay as a function of polymer concentration. Fourier-Transform Infrared Microspectroscopy analysis of spirals pointed to H-bonding between the solvent and the pendant hydroxyl groups of the glucose units from the polymer backbone. Tests on self-organization into spirals of ketal-protected d-galactaric acid polyamides in NMMO monohydrate confirmed the importance of the monosaccharide's pendant free hydroxyl groups on the formation of these patterns. Rheology performed on d-galactaric-based polyamides at high concentration in NMMO monohydrate solution revealed the optimum conditions necessary to process these materials as fibers by spinning. The self-organization of these sugar-based polyamides mimics certain biological materials.

Synthesis and properties of new fluorene-based polyimides containing trifluoromethyl and isopropyl substituents

A new fluorene-based diamine monomer containing pendant trifluoromethyl and isopropyl substituents, 9,9-bis[4-(4-amino-2-trifluoromethylphenoxy)-3-isopropylphenyl]fluorene (3), was successfully synthesized through a three-steps reaction using 2-isopropylphenol and 9-fluorenone as starting materials. Then it was employed to prepare a series of fluorinated polyimides (5a–5d) with various commercial aromatic dianhydrides via a one-step high-temperature polycondensation. These polymers could be quickly dissolved in some strong polar organic solvents, such as N-methyl-2-pyrrolidone, N,N-dimethylacetamide, and N,N-dimethylformamide, chloroform and dichloromethane at room temperature. Flexible and transparent films can be obtained conveniently by solution-casting. Their films exhibited high thermal stability with glass transition temperatures in the range of 239–287 °C, and good optical transparency with the cutoff wavelength in the range of 326–363 nm. They also revealed low dielectric constants with the values in the range of 2.65–2.84 at 1 MHz measured for their capacitance. In comparison with some trifluoromethyl-substituted polyimides without the isopropyl substituents, these polyimides showed better solubility and lower dielectric constants and cutoff wavelength.

Chemical modification with functionalized ionic liquids: a novel method to improve the enzymatic properties of Candida rugosa lipase

Chemical modification of lysine residues in Candida rugosa lipase (CRL) was carried out using five different functional ionic liquids, and about 15.4-25.0 % of the primary amino groups of lysine were modified. Enzymatic properties of the native and modified CRLs were investigated in olive oil hydrolysis reaction. Improved thermal stability, catalytic activity in organic solvents, and adaptability to temperature and pH changes were achieved compared with the native enzyme. CRL modified by [choline][H2PO4] showed the best results, bearing a maximum improvement of 16.7 % in terms of relative activity, 5.2-fold increase in thermostability (after incubation at 45 °C for 5 h), and 2.3-fold increase in activity in strong polar organic solvent (80 % dimethyl sulfoxide) compared with the native enzyme. The results of ultraviolet, circular dichroism and fluorescence spectroscopy suggested that the change of the secondary and tertiary structures of CRL caused by the chemical modification resulted in the enhancement of enzymatic performance. The modification of CRL with functional ionic liquids was proved to be a novel and efficient method for improving the enzymatic properties of CRL.

New fluorinated poly(ether sulfone imide)s with high thermal stability and low dielectric constant

A new aromatic diamine monomer with four pendant trifluoromethyl groups, 2,2′-bis{3-[3,5-di(trifluoromethyl)phenyl]-4-[4-amino-phenoxy]phenyl}sulfone (3), was successfully synthesized through free-radical substitution, Suzuki coupling and nucleophilic substitution reactions using bis(4-fluorophenyl)sulfone and N-bromosuccinimide as starting materials. Then it was employed to prepare a series of fluorinated poly(ether sulfone imide)s (PESIs 5a–c) with various commercial aromatic dianhydrides via a one-step high-temperature polycondensation. These polymers could be easily dissolved in some strong polar organic solvents, such as N-methyl-2-pyrrolidone, N,N-dimethylacetamide, and N,N-dimethylformamide, chloroform, dichloromethane and tetrahydrofuran at room temperature. Flexible and transparent films can be obtained easily by solution casting. They had high thermal stability and didn't show significant weight loss up to temperature of approximately 530 °C in nitrogen and air atmospheres. They also revealed low dielectric constants with the values in the range of 2.74–2.90 at 1 MHz measured for their capacitance.

Electrosynthesis and characterization of poly(hydroxy-methylated-3,4-ethylenedioxythiophene) film in aqueous micellar solution and its biosensing application

A new and efficient synthetic route to hydroxymethylated-3,4-ethylenedioxylthiophene (EDOT-MeOH) was developed by a simple four-step sequence, and its global yield was approximately 41.06%. The poly(hydroxymethylated-3,4-ethylenedioxylthiophene) (PEDOT-MeOH) film was electrosynthesized in aqueous sodium dodecylsulfate micellar solutions and characterized by different methods. The EDOT-MeOH possessed better water solubility, and lower onset oxidation potential than EDOT. The as-obtained PEDOT-MeOH film displayed good reversible redox activity, stability and capacitance properties in a monomer-free electrolyte, especially the good solubility of PEDOT-MeOH film in strong polar organic solvents such as dimethyl sulfoxide and tetrahydrofuran created a potential application in many different fields. Fluorescent spectra indicated that PEDOT-MeOH was a yellow-green-light-emitter with maximum emission at 568 nm. The as-formed PEDOT-MeOH film had good biocompatibility and was used for fabricating the electrochemical vitamin C biosensor. The proposed biosensor showed a linear range of 3 × 10−6 mol/L to 1.2 × 10−2 mol/L with the detection limit of 1 μmol/L, a sensitivity of 95.6 μA (mmol/L)− cm−2, and a current response time less than 10 s and a fairly good stability (The relative standard deviation was 0.43% for 20 successive assays, the proposed biosensor still retained 93.5% of bioactivity after 15 days storage. This result indicated that the prepared PEDOT-MeOH film as immobilization matrix of biologically-active species could be a promising candidate for the design and application of biosensor.

One-Pot Synthesis of Highly Monodispersed Ferrite Nanocrystals: Surface Characterization and Magnetic Properties

In the present study, a facile one-pot synthetic route, utilizing a strong polar organic solvent, N-methyl 2-pyrrolidone (NMP), is demonstrated to obtain highly monodispersed ferrite nanocrystals. The equimolar mixture of oleic acid, C(17)H(33)COOH (R-COOH), and oleylamine, C(18)H(35)NH(2) (R'-NH(2)), was used to coat the magnetic nanocrystals. Structural and magnetic properties of the ferrite nanocrystals were studied by a multitechnique approach including X-ray diffraction (XRD), high resolution transmission electron microscopy (HRTEM), Fourier transform infrared (FTIR) spectroscopy, thermogravimetric analysis (TGA), X-ray photoelectron spectroscopy (XPS), vibrating sample magnetometry (VSM), and Mössbauer spectroscopy. FTIR spectral analysis indicates oleylamine helps in deprotonation of oleic acid, resulting in the formation of an acid-base complex, R-COO¯:NH(3)(+)-R', which acts as binary capping agent. Structural and coordination differences of iron were studied by XPS and Mössbauer spectral analysis. XPS analysis was carried out to examine the oxidation state of iron ions in iron oxide nanocrystals. The presence of a magnetically dead layer (∼0.38 and ∼0.67 nm) and a nonmagnetic organic coating (∼2.3 and ∼1.7 nm) may substantially reduce the saturation magnetization values for CoFe(2)O(4) and Fe(3)O(4) nanocrystals, respectively. The energy barrier distribution function of magnetic anisotropy was derived from the temperature dependent decay of magnetization. A very narrow energy barrier distribution elucidates that the ferrite nanocrystals obtained in this study are highly monodispersed.

Facile synthesis of 3D boron nitride nanoflowers composed of vertically aligned nanoflakes and fabrication of graphene-like BN by exfoliation

Here, we present a facile solid phase method for preparing unique, 3D hexagonal boron nitride (hBN) nanoflowers, which are composed of vertically aligned BN nanoflakes. The growth process of BN nanoflowers is well-controlled by appropriately changing the reaction times and can be explained by a delayed-release mechanism. These BN nanoflowers present good thermal stability and high specific surface area. In addition, the nanoflakes composing the nanoflowers can be easily exfoliated into few-layered graphene-like BN, which is readily dispersible in strong polar organic solvents. By FTIR spectra and theoretical calculation, it is believed that the interaction of BN nanosheet and solvent predominately induces the exfoliation of graphene-like BN. Furthermore, the graphene-like BN film displays superhydrophobicity with a contact angle of 140°.

Electrochemical Polymerization of Carbazole in Acetic Acid Containing Boron Trifluoride Diethyl Etherate

AbstractHigh‐quality polycarbazole (PCz) films with an electrical conductivity of 10−2 S·cm−1 were synthesized electrochemically by direct anodic oxidation of carbazole in a novel mixed electrolyte of acetic acid containing 26% boron trifluoride diethyl etherate (BTDE) and 5% poly(ethylene glycol) with molar mass of 400 (by volume). The oxidation potential of carbazole in this medium was measured to be only 0.89 V vs. a saturated calomel electrode (SCE), which was much lower than that determined in acetonitrile containing 0.1 mol·L−1 Bu4NBF4 (1.36 V vs. SCE). PCz films obtained from this medium showed good electrochemical behavior, good thermal stability, and were partly soluble in strong polar organic solvents such as dimethyl sulfoxide and tetrahydrofuran. The fluorescence spectra implied that PCz obtained from this medium was a good blue‐light emitter. FT‐IR, 1H NMR and theoretical studies showed that the polymerization of carbazole mainly occurred at the 3,6‐positions. To the best of our knowledge, this is the first report on the electrosyntheses of conducting polymers in mixed electrolyte of acetic acid and BTDE.

Low potential electrochemical polymerization of diphenyl ether and characterization of its polymers

High-quality poly(diphenyl ether) (PDPE) films with electrical conductivity of 4.4 X 10 -1 S cm -1 were synthesized electrochemically by direct anodic oxidation of diphenyl ether (DPE) in boron trifluoride diethyl etherate (BFEE) containing 5% concentrated sulfuric acid (SA) (by volume). The oxidation potential onset of DPE in pure BFEE was measured to be only 1.37 V versus a saturated calomel electrode (SCE), which was much lower than that determined in acetonitrile +0.1 mol L -1 tetrabutylammonium tetrafluoroborate (1.98 V vs. SCE). The addition of SA to BFEE can further decrease the oxidation potential onset of the monomer to 1.18 V versus SCE in the mixed electrolyte of BFEE + 5% SA. PDPE films obtained from this medium showed good redox activity and stability even in concentrated SA. Dedoped PDPE films were partly soluble in the strong polar organic solvent dimethyl sulfoxide. Fluorescent spectral studies indicated that soluble PDPE was a good blue-light emitter with a quantum yield of 0.30. Infrared spectroscopy and quantum chemistry and C 4 .

Electrosyntheses of high quality poly (5-cyanoindole) films in boron trifluoride diethyl etherate containing additional diethyl ether

High quality poly (5-cyanoindole) (P5CI) films were synthesized electrochemically by direct anodic oxidation of 5-cyanoindole on a stainless steel sheet in boron trifluoride diethyl etherate (BFEE) + 50% diethyl ether (EE) (v/v) + 0.05 mol L −1 Bu 4NBF 4. They can be peeled off the electrode into freestanding films. The introduction of EE to BFEE can improve the solubility of monomer. The oxidation potential of 5-cyanoindole in this medium was measured to be only 1.15 V versus SCE, which was lower than that determined in acetonitrile + 0.1 mol L −1 Bu 4NBF 4 (1.58 V versus SCE). BFEE + 50% EE + 0.05 mol L −1 Bu 4NBF 4 was tested to be a better medium than acetonitrile for the electrosyntheses of P5CI films. P5CI films obtained from BFEE + 50% EE + 0.05 mol L −1 Bu 4NBF 4 showed good electrochemical behavior, good thermal stability with conductivity of 10 −2 S cm −1. The polymerization of 5-cyanoindole ring through 2,3-position was proved by FT-IR and 1H NMR spectroscopy. As-formed P5CI films were thoroughly soluble in strong polar organic solvent dimethyl sulfoxide (DMSO) while partly soluble in tetrahydrofuran (THF) or acetone. Fluorescence spectral studies indicated that P5CI was a good blue-light emitter.

Electrosyntheses of high‐quality poly(5‐nitroindole) films in boron trifluoride diethyl etherate containing additional diethyl ether

AbstractHigh‐quality poly(5‐nitroindole) (PNP) films were synthesized electrochemically by the direct anodic oxidation of 5‐nitroindole in boron trifluoride diethyl etherate (BFEE) containing additional 10% diethyl ether (EE) (by volume). The addition of EE to BFEE could improve the solubility of the monomer. The oxidation potential onset of 5‐nitroindole in this medium was measured to be only 1.04 V versus a saturated calomel electrode (SCE), which was much lower than that determined in acetonitrile and 0.1 mol L−1 tetrabutylammonium tetrafluoroborate (1.53 V vs SCE). PNP films obtained from this medium showed good electrochemical behavior and good thermal stability with a conductivity of 10−2 S cm−1; this indicated that BFEE containing 10% EE was a suitable medium for the electrosyntheses of PNP films. Structural studies showed that the polymerization of the 5‐nitroindole ring occurred at the 2,3‐position. As‐formed PNP films were thoroughly soluble in the strong polar organic solvent dimethyl sulfoxide and partly soluble in tetrahydrofuran or acetone. Fluorescent spectral studies indicated that PNP was a good green‐light emitter, with excitation and emission wavelengths of 420 and 550 nm, respectively. To the best of our knowledge, this is the first time that nitro‐group‐substituted high‐quality conducting polymer films have been electrodeposited. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 3986–3997, 2005