Effects of different acid functional groups on proton conductivity of polymer‐1,2,4‐triazole blends

Proton transfer reactions under anhydrous conditions have attracted remarkable interest due to chemical energy conversions in polymer electrolyte membrane fuel cells. In this work, 1H‐1,2,4‐triazole (Tri) was used as a proton solvent in different polymer host matrices such as Poly(vinylphosphonic acid) (PVPA), and poly(2‐acrylamido‐2‐methyl‐1‐propane sulfonic acid) (PAMPS). PVPATri_x and PAMPSTri_x electrolytes were investigated where x is the molar ratio of Tri to corresponding polymer repeat unit. The interaction between polymer and Tri was studied via FTIR spectroscopy. Thermogravimetry analysis and differential scanning calorimetry were employed to examine the thermal stability and homogeneity of the materials, respectively. PVPATri_1.5 showed a maximum water‐free proton conductivity of 2.3 × 10^?3 S/cm at 120 °C and that of PAMPSTri₂ was 9.3 × 10^?4 S/cm at 140 °C. The results were interpreted in terms of different acidic functional groups and composition. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 3315–3322, 2006     

Polymer electrolyte membranes based on p‐toluenesulfonic acid doped poly(1‐vinyl‐1,2,4‐triazole): Synthesis,thermal and proton conductivity properties

Throughout this work, the synthesis, thermal as well as proton conducting properties of acid doped heterocyclic polymer were studied under anhydrous conditions. In this context, poly(1‐vinyl‐1,2,4‐triazole), PVTri was produced by free radical polymerization of 1‐vinyl‐1,2,4‐triazole with a high yield. The structure of the homopolymer was proved by FTIR and solid state ¹³C CP‐MAS NMR spectroscopy. The polymer was doped with p‐toluenesulfonic acid at various molar ratios, x = 0.5, 1, 1.5, 2, with respect to polymer repeating unit. The proton transfer from p‐toluenesulfonic acid to the triazole rings was proved with FTIR spectroscopy. Thermogravimetry analysis showed that the samples are thermally stable up to ～250 °C. Differential scanning calorimetry results illustrated that the materials are homogeneous and the dopant strongly affects the glass transition temperature of the host polymer. Cyclic voltammetry results showed that the electrochemical stability domain extends over 3 V. The proton conductivity of these materials increased with dopant concentration and the temperature. Charge transport relaxation times were derived via complex electrical modulus formalism (M*). The temperature dependence of conductivity relaxation times showed that the proton conductivity occurs via structure diffusion. In the anhydrous state, the proton conductivity of PVTri1PTSA and PVTri2PTSA was measured as 8 × 10^?4 S/cm at 150 °C and 0.012 S/cm at 110 °C, respectively. © 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 48: 1016–1021, 2010     

Click chemistry‐assisted triazole‐substituted azobenzene and fulgimide units in the pendant‐based copoly(decyloxymethacrylate)s for dual‐mode optical switches

Copolymer containing new thermally reversible click chemistry‐assisted triazole‐substituted azobenzene and fulgimide units in the pendant F‐co‐A was prepared by free‐radical solution addition polymerization technique. The F and A were also prepared for comparison. The DSC analysis of F indicates that the polymer possessing the C‐form of fulgimide unit exhibited higher T_m than that of E‐form of the same polymer and revealed that the C‐form of fulgimide unit in F is highly ordered. The cis‐trans back isomerization behavior of the click chemistry‐assisted triazole‐substituted azobenzene unit in film A has thermal irreversibility, while in F‐co‐A it exhibited thermal reversibility. The UV‐exposed film of F‐co‐A heated around T_g leads to cis‐trans back isomerization of azobenzene unit and thermally stable C‐form of fulgimide which retains its conjugated structure where both the photochromic units are converted into planar conformations and exhibit high fluorescence properties. The fluorescence maxima of C‐form in F‐co‐A red shifted compared with F , because the substituted triazole ring in the azobenzene unit stabilized the C‐form of fulgimide unit. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 7843–7860, 2008     

Novel anhydrous proton conducting copolymers of 1‐vinyl‐1,2,4‐triazole and diisopropyl‐p‐vinylbenzyl phosphonate

Phosphonic acid functional polymers are currently of interest because of their high proton conductivity in humidified and anhydrous systems. In addition, heterocyclic compounds are used in anhydrous proton conducting polymer membranes. In that study, a new copolymer based on 1‐vinyl‐1,2,4‐triazole (VTri) and diisopropyl‐p‐vinylbenzyl phosphonate (VBP) was synthesized, and their thermal, chemical, and proton conducting properties were investigated. The copolymers were synthesized by free radical copolymerization of the corresponding monomers at several monomer feed ratios to obtain P(VTri‐co‐VBP) copolymers. The copolymer samples were then hydrolyzed to produce poly(vinyl triazole‐co‐vinyl phosphonic acid) copolymers. The composition of the copolymers was determined by elemental analysis. The copolymerization and hydrolysis reactions were verified by Fourier transform infrared spectroscopy and ion exchange capacity measurements. Thermogravimetry analysis indicates that the copolymers are thermally stable up to 300°C. In order to increase the proton conductivity, the copolymers were doped with H₃PO₄ at several stoichometric ratios. The proton conductivity increases with triazole and phosphoric acid content. In the absence of humidity, the copolymer electrolyte, P(VTri‐co‐VBPA)1:0.5 X = 2, showed a proton conductivity of 0.005 S/cm at 150°C. Copyright © 2013 John Wiley & Sons, Ltd.     

Synthesis and proton conductivity studies of polystyrene‐based triazole functional polymer membranes

In this study, poly(vinylbenzylchloride) (PVBC) was produced by free‐radical polymerization of 4‐vinylbenzylchloride, and then it was functionalized with 3‐amino‐1,2,4‐triazole (ATri) and 1H‐1,2,4‐triazole (Tri). The composition of the polymers was verified by elemental analysis, and the structure was characterized by Fourier transform infrared and ¹³C‐nuclear magnetic resonance spectra. PVBC was modified by ATri with 68% and Tri with 50% yield. The polymers were doped with trifluoromethanesulfonic acid (TA) at various molar ratios, X = 0.5, 1, 2, and 3 with respect to aminotriazole and triazole units. Proton transfer from TA to the triazole rings was proved with Fourier transform infrared spectroscopy. Thermogravimetric analysis showed that the samples are thermally stable up to approximately 200 °C. Differential scanning calorimetry results illustrated the homogeneity of the materials. Under anhydrous conditions, PVBCATri3TA and PVBCTri3TA showed highest proton conductivity of 0.086 and 0.042 S/cm, respectively. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2010     

Investigation of proton conductivity of anhydrous proton exchange membranes prepared via grafting vinyltriazole onto alkaline‐treated PVDF

This work uses a simple “grafting through” approach in the preparation of anhydrous poly(vinylidene fluoride) (PVDF)‐g‐PVTri polymer electrolyte membranes (PEMs). Alkaline‐treated PVDF was used as a macromolecule in conjunction with vinyltriazole in the graft copolymerization. The obtained polymer was subsequently doped with triflic acid (TA) at different stoichiometric ratios with respect to triazole units and the anhydrous PEMs (PVDF‐g‐PVTri‐(TA)_x) were prepared. All samples were characterized by FTIR and ¹H NMR. The composition of PVDF‐g‐PVTri was determined by energy dispersive spectroscopy. Thermal properties of the membranes were examined by thermogravimetric analysis and differential scanning calorimetry. The surface roughness and morphology of the membranes were studied using atomic force microscopy, X‐ray diffraction, and scanning electron microscopy. PVDF‐g‐PVTri‐(TA)₃ (C3‐TA₃) with a degree of grafting of 47.22% showed a maximum proton conductivity of 0.09 S cm^?1 at 150 °C and anhydrous conditions. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 1885–1897     

Poly[2,7‐(9,9‐dihexylfluorene)‐alt‐pyridine] with donor‐acceptor architectures: A new series of blue‐light‐emitting alternating copolymers

A novel series of well‐defined alternating poly[2,7‐(9,9‐dihexylfluorenyl)‐alt‐pyridinyl] (PDHFP) with donor‐acceptor repeat units were synthesized using palladium (0)‐catalyzed Suzuki cross‐coupling reactions in good to high yields. In this series of alternating polymers, 2, 7‐(9,9‐dihexylfluorenyl) was used as the light emitting unit, and the electron deficient pyridinyl unit was employed to provide improved electron transportation. These polymers were characterized by ¹H‐NMR and ¹³C‐NMR, gel permeation chromatography (GPC), thermal analyses, and UV‐vis and fluorescence spectroscopy. The glass transition temperature of copolymers in nitrogen ranged from 110 to 148 °C, and the copolymers showed high thermal stabilities with high decomposition temperatures in the range of 350 to 390 °C in air. The difference in linkage position of pyridinyl unit in the polymer backbone has significant effects on the electronic and optical properties of polymers in solution and in film phases. Meta‐linkage (3,5‐ and 2,6‐linkage) of pyridinyl units in the polymer backbone is more favorable to polymer for pure blue emission and prevention of aggregation of polymer chain than para‐linkage (2,5‐linkage) of the pyridinyl units. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 4792–4801, 2004     

The physical and NMR characterizations of allyl‐ and crotylcelluloses

Tri‐O‐allylcellulose (degree of polymerization, DP ∼112) was prepared in ∼91% yield, and tri‐O‐crotylcellulose (DP ∼138) was prepared in ∼56% yield from microcrystalline cellulose (DP ∼172, and polydispersity index, PDI ∼1.95) using modified literature methods. Number‐average molecular weight (M_n = 31,600), weight‐average molecular weight (M_w = 191,800), and PDI = 6.07 data suggested that tri‐O‐allylcellulose may be crosslinking in air to generate branched chains. The polymer was stabilized with 100 ppm butylated hydroxy toluene (BHT). The material without BHT experienced glass transition (T_g, differential‐scanning calorimetry, DSC) between −2 and +3 °C, crosslinked beyond 100 °C, and degraded at 298.6 °C (by thermogravimetric analysis, TGA). M_n (45,100), M_w (118,200), PDI (2.62), and thermal data (T_g − 5 to +3 °C, melting point 185.8 °C, recrystallization 168.9 °C, and degradation 343.6 °C) on tri‐O‐crotylcellulose suggested that the polymer was formed with about the same polydispersity as the starting material and is heat stable. While allylcellulose generated continuous flexible yellow films by solution casting, crotylcellulose precipitated from solution as brittle white flakes. Dynamic mechanical analysis (DMA) data on allylcellulose films (T_g − 29.1 °C, Young's modulus 5.81 × 10⁸ Pa) suggest that the material is tough and flexible at room temperature. All ¹H and ¹³C resonances in the NMR spectra were identified and assigned using the following methods: Double‐quantum filter correlation spectroscopy (DQF COSY) was used to assign the network of seven protons in the anhydroglucose portion of the repeat unit. The proton assignments were verified and confirmed by total correlation spectroscopy (TOCSY). A combination of heteronuclear single‐quantum coherence (HSQC) and ¹³C spectroscopies were used to identify all bonded carbon–hydrogen pairs in the anhydroglucose portion of the repeat unit, and assign the carbon nuclei chemical shift values. Heteronuclear multiple bond correlation (HMBC) spectroscopy was used to connect the resonances of methines and methylenes at positions 2, 3, and 6 to the methylene resonances of the allyl ethers. TOCSY was used again to identify the fifteen ¹H resonances in the three pendant allyl groups. Finally, a combination of HSQC, HMBC, and ¹³C spectroscopies were used to identify each carbon in the allyl pendants at 2, 3, and 6. Because of line broadening and signal overlap, we were unable to identify the conformational arrangement about the C5 and C6 bond in tri‐O‐allyl‐ and tri‐O‐crotylcelluloses. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 1889–1902, 2000     

Polybenzimidazoles tethered with N‐phenyl 1,2,4‐triazole units as polymer electrolytes for fuel cells

Polybenzimidazole (PBI) polymers tethered with N‐phenyl 1,2,4‐triazole (NPT) groups were prepared from a newly synthesized aromatic diacid, 3′‐(4‐phenyl‐4H‐1,2,4‐triazole‐3,5‐diyl) dibenzoic acid (PTDBA). The obtained polymers show superior thermal and chemical stability and good solubility in many aprotic solvents. The inherent viscosities of all polymers were around 1 dL/g. They exhibit high thermal stability with initial decomposition temperature ranging from 515 to 530 °C, high glass transition temperature ranging from 375 to 410 °C, and good mechanical properties with tensile stress in the range of 66–98 MPa and modulus 1897–2600 MPa. XRD analysis indicates that these polymers are amorphous in nature. Physicochemical properties such as water and phosphoric acid‐uptake, oxidative stability, and proton conductivity of membranes of these polymers have also been determined. The proton conductivity ranged from 4.7 × 10^?3 to 1.8 × 10^?2 S cm^?1 at 175 °C in dry conditions. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 2289–2303, 2009     

Synthesis,photophysics, structure‐tunable photoluminescence,and electrochemical properties of soluble poly(p‐phenylenevinylene)‐based polymers with adjacent 1,3,4‐oxadiazoles in the backbone

Three new poly(p‐phenylenevinylene)‐based polymers containing two 1,3,4‐oxadiazole moieties in the main chain per repeat unit were synthesized by Heck coupling. A single, double, or triple bond was introduced between the oxadiazoles to provide a means for modifying the polymer properties. The polymers were readily soluble in common organic solvents and showed T_g values lower than 50 °C. The color of the emissive light in both the solid state and the solution could be tuned by a change in the nature of the bond between the oxadiazole rings. The polymers emitted ultraviolet‐green light in solution with a photoluminescence (PL) emission maximum at 345–483 nm and blue‐green light at 458–542 nm in thin films. The PL quantum yields in solution were 0.36–0.43. The electrochemical properties are affected by the nature of the bond between the oxadiazoles as well. In polymers with a single bond between the oxadiazoles, a lower ionization potential was observed than in polymers with a double or triple bond. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 3079–3090, 2005     

Synthesis of polyimides containing triphenylamine‐substituted triazole moieties for polymer memory applications

A series of thermally stable aromatic polyimides containing triphenylamine‐substituted triazole moieties ( AZTA‐PI )s were prepared and characterized. The glass transition temperatures (T_g) of the polyimides were found to be in the range of 262–314 °C. The polyimides obtained by chemical imidization had inherent viscosities of 0.25–0.44 dL g^?1 in N‐methyl‐2‐pyrrolidinone. The number average molecular weights (M_n) and weight average molecular weights (M_w) were 1.9–3.2 × 10⁴ and 3.2–5.6 × 10⁴, respectively, and the polydispersity indices (PDI = M_w/M_n) were in the range of 1.70–1.78. A resistive switching device was constructed from the 4,4′‐hexafluoroisopropylidenediphthalic dianhydride‐based soluble polyimide ( AZTA‐PIa ) in a sandwich structure of indium‐tin oxide/polymer/Al. The as‐fabricated device can be switched from the initial low‐conductivity (OFF) state to the high‐conductivity (ON) state at a switching threshold voltage of 2.5 V under either positive or negative electrical sweep, with an ON/OFF state current ratio in the order of 10⁵ at ?1 V. The device is able to remain in the ON state even after turning off the power or under a reverse bias. The nonvolatile and nonrewritable natures of the ON state indicate that the device is a write‐once read‐many times (WORM) memory. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2010     

Thermodynamic characteristics of poly(cyclohexylethylene‐b‐ethylene‐co‐ethylethylene) block copolymers

A series of poly(cyclohexylethylene‐b‐ethylene‐co‐ethylethylene) (C‐E/E_E) diblock copolymers containing approximately 50% by volume glassy C blocks and varying fraction (x) of E_E repeat units, 0.07 ≤ x ≤ 0.90, was synthesized by anionic polymerization and catalytic hydrogenation. The effects of ethyl branch content on the melt state segment–segment (χ) interaction parameter and soft (E/E_E) block crystallinity were studied. The percent crystallinity ranged from approximately 30% at x = 0.07 to 0% at about x ≥ 0.30, while the melting temperature changed from 101 °C at x = 0.07 to 44 °C at x = 0.28. Dynamic mechanical spectroscopy was employed to determine the order–disorder transition (ODT) temperatures, from which χ was calculated assuming the mean‐field prediction (χN_n)_ODT = 10.5. Previously published results for the temperature dependent binary interaction parameters for C‐E (x = 0.07), C‐E_E (x = 0.90), and E‐E_E (x = 0.07 and x = 0.90) fail to account for the quantitative x dependence of χ, based on a simple binary interaction model. © 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 48: 566–574, 2010     

Anion conductive aromatic polymers containing fluorenyl groups: Effect of the position and number of ammonium groups

Synthesis and properties of anion conductive aromatic block copolymers, QPE‐bl‐3, QPE‐bl‐3 M2, and M4, containing fluorenylidene biphenylene groups as scaffold for ammonium groups are described. These copolymers share the same main chain structure, but the position and the number of ammonium groups on a fluorenyl group differ. High molecular weight quaternized block copolymers were obtained via typical chloromethylation reaction or using preaminated monomers, and were well‐characterized by ¹H NMR spectra. Self‐standing bendable membranes were obtained by solution casting. QPE‐bl‐3 M4 membranes containing four ammonium groups per hydrophilic repeat unit (highest ammonium density) in the hydrophilic block exhibited well developed phase‐separated morphology, while QPE‐bl‐3 membranes containing two ammonium groups per hydrophilic repeat unit exhibited high anion conductivity. The highest anion conductivity (104 mS/cm) was obtained with QPE‐bl‐3 membrane (IEC = 2.1 meq/g) at 80 °C in water. An H₂/O₂ alkaline fuel cell was operable with the membrane to achieve 62 mW/cm² of the maximum power density at 161 mA/cm² of the current density. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 935–944     

Gold nanoparticle‐incorporated core and shell crosslinked micelles fabricated from thermoresponsive block copolymer of N‐isopropylacrylamide and a novel primary‐amine containing monomer

A novel primary amine‐containing monomer, 1‐(3′‐aminopropyl)‐4‐acrylamido‐1,2,3‐triazole hydrochloride (APAT), was prepared from N‐propargylacrylamide and 3‐azidopropylamine hydrochloride via copper‐catalyzed Huisgen 1,3‐dipolar cycloaddition (click reaction). Poly(N‐isopropylacrylamide)‐b‐poly(1‐(3′‐aminopropyl)‐4‐acrylamido‐1,2,3‐triazole hydrochloride), PNIPAM‐b‐PAPAT, was then synthesized via consecutive reversible addition‐fragmentation chain transfer polymerizations of N‐isopropylacrylamide and APAT. In aqueous solution, the obtained thermoresponsive double hydrophilic block copolymer dissolves molecularly at room temperature and self‐assembles into micelles with PNIPAM cores and PAPAT shells at elevated temperature. Because of the presence of highly reactive primary amine moieties in PAPAT block, two types of covalently stabilized nanoparticles namely core crosslinked and shell crosslinked micelles with ‘inverted’ core‐shell nanostructures were facilely prepared upon the addition of glutaric dialdehyde at 25 and 50 °C, respectively. In addition, the obtained structure‐fixed micelles were incorporated with gold nanoparticles via in situ reduction of preferentially loaded HAuCl₄. High resolution transmission electron microscopy revealed that gold nanoparticles can be selectively loaded into the crosslinked cores or shells, depending on the micelle templates employed. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 6518–6531, 2008     

Synthesis of high‐refractive index polyimide containing selenophene unit

A highly refractive and transparent aromatic polyimide (PI) containing a selenophene unit has been developed. The PI was prepared by a two‐step polycondensation procedure from 2,5‐bis(4‐aminophenylenesulfanyl)selenophene (APSP) and 4,4′‐[p‐thiobis(phenylenesulfanyl)]diphthalic anhydride (3SDEA), and shows high thermal stabilities, such as a relatively high‐glass transition temperature of 189 °C and 5% weight loss temperature (T_5%) of 418 °C. The optical transmittance of the PI film at 450 nm is higher than 50%. The selenophene unit provides the PI with a refractive index of 1.7594, which is higher than corresponding PIs containing a thiophene or a phenyl unit because of the high polarizability per unit volume of the selenium atom. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 4428–4434, 2009     

Cyclic and branched functional polyesters derived from 5,5′,6,6′‐tetrahydroxy‐3,3,3′,3′‐tetramethyl spirobisindane and various dicarboxylic acids

Triethylamine‐promoted polycondensations of 5,5′,6,6′‐tetrahydroxy‐3,3, 3′,3′‐tetramethyl spirobisindane (TTSBI) and α,ω‐alkane dicarboxylic acid dichlorides were performed with equimolar feed ratios. Three different procedures were compared. At a TTSBI concentration of 0.05 mol/L, gelation was avoided, and soluble cyclic polyesters having two OH groups per repeat unit were isolated. These polyesters were characterized with ¹H NMR spectroscopy, MALDI‐TOF mass spectrometry, and SEC and DSC measurements. All polycondensations with sebacoyl chloride resulted in gelation, regardless of the procedure. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 1699–1706, 2007     

Anhydrous state proton conduction in sulfonated bisphenol a polyetherimide with 1H‐1,2,4 triazole as proton solvent

In this study, bisphenol A polyetherimide was sulfonated to various degrees (22, 48, and 62%) by trimethylsilylchlorosulfonate (TMSCS). Novel anhydrous proton conducting polyelectrolytes were prepared by the incorporation of 1H‐1,2,4‐triazole (Taz) as proton solvent in sulfonated polyetherimide (SPEI) matrix. The conductivity reached about 2 × 10^–3 S/cm at 80 °C and 10^–2 S/cm at 140 °C. The temperature dependence proton conductivity of the polyelectrolytes followed Arrhenius equation. The conductivity improved considerably at a temperature close to the triazole melting temperature in SPEI(X)H matrix. It was proposed that the high mobility of the triazolium ions (vehicle diffusion), in addition to structure diffusion, contribute to the high conductivity of these proton conducting electrolytes above the melting temperature of triazole. © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 47: 2178–2187, 2009     

Proton conduction in 1H‐1,2,3‐triazole polymers: Imidazole‐like or pyrazole‐like?

Proton transport (PT) plays an important role in many biological processes as well as in materials for renewable energy devices. Gaining insights into functional group requirements for PT would aid the design of new materials that provide enhanced proton conduction. In this report, we outline our efforts to understand the most probable proton conduction pathway in 1H‐1,2,3‐triazole systems. In triazole‐based systems, both imidazole‐ and pyrazole‐like pathways are possible. By systematically comparing structurally analogous polymers based on N‐heterocycles and benz‐N‐heterocycles, we find that the imidazole‐like pathway makes a significant contribution to the proton transfer in 1H‐1,2,3‐triazole systems, while the contribution from pyrazole‐like pathway is negligible. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 1851–1858, 2010     

Proton‐conducting poly(vinylpyrrolidon)–polyphosphoric acid blends

Anhydrous, proton‐conducting polymer electrolytes of poly(vinylpyrrolidon) (PVP) with polyphosphoric acid (PPA) were prepared. PVP‐x‐PPA blends were obtained for 0.5 ≤ x ≤ 3, where x was the number of moles of PO per polymer repeat unit. Fourier transform infrared studies indicated protonation of the carbonyl group in the five‐member ring. Thermogravimetric analysis showed that these materials were stable up to about 180 °C. Differential scanning calorimetry data demonstrated that the addition of the acid plasticized the material, shifting the glass‐transition temperature from 180 °C for the pure polymer to ?23 °C for x = 3. The temperature dependence of the mechanical properties was investigated with shear experiments. The direct‐current conductivity increased with x and reached about 10^?5 S/cm at ambient temperature. © 2001 John Wiley & Sons, Inc. J Polym Sci Part B: Polym Phys 39: 1987–1994, 2001     

Grafting of aldehyde structures to single‐walled carbon nanotubes for application in phenolic resin‐based composites

Grafting of aldehyde structures to single‐walled carbon nanotubes (SWNTs) has been carried out to endow the nanotubes with appropriate wettability. The results of Fourier transform infrared (FTIR) spectroscopy, ultraviolin‐visible‐near infrared (UV‐VIS‐NIR) spectroscopy, and Raman spectroscopy provide the supporting evidence of aldehyde structures covalently attached to SWNTs. The improved wettability of aldehyde‐functionalized SWNTs (f‐SWNTs) was demonstrated by their good dispersion in organic medium, namely, ethanol and phenolic resin. The prospective covalent bonding between aldehyde structures on the surfaces of f‐SWNTs and phenolic resin makes it possible to prepare an integrated composite with the enhanced‐interfacial adhesion. The f‐SWNT composites, therefore, show much higher average values of dσ/dW_CNT and dE/dW_CNT (i.e., tensile strength and Young's modulus per unit weight fraction) compared with the composites filled with pristine SWNTs or MWNTs. The respective maxima are 9680 MPa and 320 GPa. It is thus feasible for f‐SWNTs to prepare the moderately enhanced but lightweight phenolic composites. Furthermore, the incorporation of f‐SWNTs does not limit the application of phenolic resin as insulation material. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 6135–6144, 2009