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ABSTRACT: New organic–inorganic composite membranes based on poly(vinylidene fluoride-co-chlorotrifluoroethylene)-graft-poly(styrene sulfonic acid) [P(VDF-co-CTFE)-g-PSSA] with embedded phosphotungstic acid (PWA) were prepared. Fourier transform infrared spectra indicated the existence
of a specific interaction between P(VDF-co-CTFE)-g-PSSA graft copolymer and PWA particles. PWA nanoparticles were well confined in the polymeric matrix up to 20wt.%, above
which they started to be extracted from the matrix, as revealed by scanning electron microscope analysis. Accordingly, Young’s
modulus of membranes also increased with PWA concentration up to 20wt.%, above which it continuously decreased. Upon incorporation
of PWA nanoparticles, the proton conductivity of composite membranes slightly decreased from 0.042 to 0.035S/cm at room temperature
up to 20wt.%, presumably due to strong interaction between the sulfonic acids of graft copolymer and PWA nanoparticles. The
characterization by thermal gravimetric analysis demonstrated the enhancement of thermal stabilities of the composite membranes
with increasing concentration of PWA.
Ionics 04/2012; 15(4):439-444. · 1.29 Impact Factor
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ABSTRACT: Nanocomposite films were prepared by sol-gel synthesis from vanadium triisopropoxide with poly((oxyethylene)9 methacrylate)-graft-poly(dimethyl siloxane), POEM-g-PDMS, producing in situ growth of vanadium oxide within the continuous ion-conducting POEM domains of microphase-separated
graft copolymer. The formation of vanadium oxide was confirmed by wide angle x-ray scattering (WAXS) and Fourier transform
infrared (FTIR) spectroscopy. Small angle x-ray scattering (SAXS) revealed the spatially-selective incorporation of vanadium
oxide in the POEM domains. Upon the incorporation of vanadium oxide, the domain periodicity of the graft copolymer monotonously
increased from 17.2 to 21.0 nm at a vanadium content 14 v%, above which it remained almost invariant. The selective interaction
of vanadium oxide with POEM was further verified by differential scanning calorimetry (DSC) and FT-IR spectroscopy. The nanocomposite
films exhibited excellent mechanical properties (10−5-10−7 dyne/cm2), mostly due to the confinement of vanadium oxide in the POEM chains as well as the interfaces created by the microphase
separation of the graft copolymer.
Keywordsnanocomposite–sol-gel–graft copolymer–microphase separation–spectroscopy
Macromolecular Research 04/2012; 15(6):553-559. · 1.15 Impact Factor
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ABSTRACT: Porous TiO(2) nanotube arrays with three-dimensional (3D) interconnectivity were prepared using a sol-gel process assisted by poly(vinyl chloride-graft-4-vinyl pyridine), PVC-g-P4VP graft copolymer and a ZnO nanorod template. A 7 µm long ZnO nanorod array was grown from the fluorine-doped tin oxide (FTO) glass via a liquid phase deposition method. The TiO(2) sol-gel solution templated by the PVC-g-P4VP graft copolymer produced a random 3D interconnection between the adjacent ZnO nanorods during spin coating. Upon etching of ZnO, TiO(2) nanotubes consisting of 10-15 nm nanoparticles were generated, as confirmed by wide-angle x-ray scattering (WAXS), energy-filtering transmission electron microscopy (EF-TEM) and field-emission scanning electron microscopy (FE-SEM). The ordered and interconnected nanotube architecture showed an enhanced light scattering effect and increased penetration of polymer electrolytes in dye-sensitized solar cells (DSSC). The energy conversion efficiency reached 1.82% for liquid electrolyte, and 1.46% for low molecular weight (M(w)) and 0.74% for high M(w) polymer electrolytes.
Nanotechnology 09/2011; 22(36):365401. · 3.98 Impact Factor
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ABSTRACT: A novel amphiphilic poly(4-vinyl pyridine)-graft-poly(lauryl methacrylate) (P4VP-g-PLMA) graft copolymer at 29:71 wt% was synthesized via free radical polymerization, as confirmed by nuclear magnetic resonance (1H NMR). This self-assembled copolymer was used to template the in-situ growth of silver bromide (AgBr) nanoparticles, producing a solid-state nanocomposite film. Interestingly enough, AgBr nanoparticles with a bimodal size distribution were selectively grown within the copolymer matrix. Large nanoparticles with diameters of 30-40 nm were formed in the center of the hydrophilic P4VP spherical domains whereas smaller particles with diameters of 8-10 nm were decorated in hydrophobic PLMA domains. To the best of our knowledge, this is the first report on the nanoscale decoration of amphiphilic copolymer by AgBr nanoparticles with a size-selective, bimodal size distribution.
Journal of Nanoscience and Nanotechnology 10/2010; 10(10):6907-11. · 1.56 Impact Factor
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ABSTRACT: An amphiphilic graft copolymer of poly(vinyl chloride-graft-4-vinyl pyridine), i.e., PVC-g-P4VP was synthesized via atom transfer radical polymerization (ATRP) and modified by introducing 1,5-dihydroxynaphthalene (DHN) as a hydrogen bonding donor to form hydrogen-bonded macromolecules. The PVC-g-P4VP graft copolymer prepared from a selective solvent for PVC, i.e., tetrahydrofuran (THF) exhibited a well-organized micellar morphology consisting of a P4VP core and a PVC corona. However, the graft copolymer prepared from a good solvent for both domains, i.e., N, N-dimethylformamide (DMF) showed a less-organized, random microphase-separated morphology. Upon the introduction of DHN, a more spherical morphology and a more-organized 'bicontinuous-like' morphology was observed in THF and DMF, respectively. This results from strong segregation between the two domains due to the enhanced interfacial energy by DHN. When DHN was removed by methanol, nanoporous films with versatile pore sizes and shapes were generated.
Nanotechnology 09/2010; 21(35):355604. · 3.98 Impact Factor
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ABSTRACT: Randomly microphase-separated graft copolymers have been self-reorganized so as to exhibit a micellar structure with excellent connectivity upon tuning the solvent affinity. These copolymers are used as a structure-directing agent for organized mesoporous TiO(2) films with no grain boundaries, leading to enhanced solar conversion efficiency of dye-sensitized solar cells.
Chemical Communications 03/2010; 46(11):1935-7. · 6.17 Impact Factor
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ABSTRACT: A novel amphiphilic graft copolymer, poly(vinylidene fluoride-co-chlorotrifluoroethylene)-g-poly(4-vinyl pyridine) (P(VDF-co-CTFE)-g-P4VP) at 65:35 wt.%, respectively, was synthesized via atom transfer radical polymerization (ATRP), as confirmed by nuclear magnetic resonance (1H NMR) and transmission electron microscopy (TEM). Silver bromide (AgBr) nanoparticles were in situ generated within the self-assembled P(VDF-co-CTFE)-g-P4VP graft copolymer. TEM, UV-visible spectroscopy and X-ray diffraction (XRD) analyses support the successful formation of P(VDF-co-CTFE)-g-P4VP nanocomposites consisting of stabilized AgBr nanoparticles mostly 20-40 nm in size, which is presumably due to the capping action of the coordinating pyridine groups of the graft copolymer. The wavenumber of pyridine nitrogen in FT-IR spectra and the glass transition temperature (Tg) of the graft polymer measured by DSC shifted upon the formation of AgBr nanoparticles, indicating specific interactions between the nanoparticles and the graft copolymer matrix.
Journal of Colloid and Interface Science 08/2009; 338(2):486-90. · 3.07 Impact Factor
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ABSTRACT: An amphiphilic comb-like copolymer consisting of a poly(vinyl chloride) (PVC) backbone and poly((oxyethylene)9 methacrylate) (POEM) side chains, PVC-graft-POEM was synthesized via atom transfer radical polymerization. This comb copolymer was complexed with LiCF3SO3 to form a solid polymer electrolyte. FTIR and FT-Raman spectroscopy indicate that lithium salts are dissolved in the ion conducting POEM domains of microphase-separated graft copolymer up to 10 wt % of salt concentration. Microphase-separated structure of the materials and the selective interaction of lithium ions with POEM domains were revealed by transmission electron microscopy, wide angle X-ray scattering, and differential scanning calorimetry. The maximum ionic conductivity of 4.4 × 10−5 S/cm at room temperature was achieved at 10 wt % of salt concentration, above which salts are present as less mobile species such as ion pairs and higher order ionic aggregates, as characterized by FT-Raman spectroscopy. © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 47: 1443–1451, 2009
Journal of Polymer Science Part B Polymer Physics 06/2009; 47(15):1443 - 1451. · 1.53 Impact Factor
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ABSTRACT: Graft copolymers comprising poly(vinylidene fluoride-co-chlorotrifluoroethylene) backbone and poly(styrene sulfonic acid) side chains, i.e. P(VDF-co-CTFE)-g-PSSA were synthesized using atom transfer radical polymerization (ATRP) for composite nanofiltration (NF) membranes. Direct initiation of the secondary chlorinated site of CTFE units facilitates grafting of PSSA, as revealed by FT-IR spectroscopy. The successful “grafting from” method and the microphase-separated structure of the graft copolymer were confirmed by transmission electron microscopy (TEM). Wide angle X-ray scattering (WAXS) also showed the decrease in the crystallinity of P(VDF-co-CTFE) upon graft copolymerization. Composite NF membranes were prepared from P(VDF-co-CTFE)-g-PSSA as a top layer coated onto P(VDF-co-CTFE) ultrafiltration support membrane. Both the rejections and the flux of composite membranes increased with increasing PSSA concentration due to the increase in SO3H groups and membrane hydrophilicity, as supported by contact angle measurement. The rejections of NF membranes containing 47 wt% of PSSA were 83% for Na2SO4 and 28% for NaCl, and the solution flux were 18 and 32 L/m2 hr, respectively, at 0.3 MPa pressure. Copyright © 2008 John Wiley & Sons, Ltd.
Polymers for Advanced Technologies 06/2008; 19(11):1643 - 1648. · 2.01 Impact Factor
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ABSTRACT: In this paper, we aim to prepare polymer electrolytes consisting of NaI and I2 dissolved in poly(ethylene oxide) (PEO) and dioctyl phthalate (DOP) as an additive and apply the electrolytes to dye-sensitized
solar cells (DSSC). Upon the incorporation of salt, the phthalic-stretching C=O bands of DOP in Fourier transform infrared
spectra shifted to a lower wave number (Δf = 93cm−1), confirming the unusual strong complex formation between sodium ions and phthalic oxygen. Coordinative interactions and
structural changes of PEO/NaI/I2/DOP electrolytes have also been characterized by wide angle X-ray scattering, presenting an almost amorphous structure of
the polymer electrolytes. The ionic conductivity of the polymer electrolytes reached ∼10–4S/cm at room temperature at the mole ratio of [EO]:[Na]:[DOP] = 10:1:0.5, as determined by the four-probe method. DSSC using
the polymer electrolytes and conductive indium tin oxide glasses exhibited 2.9% of overall energy conversion efficiency (=P
max/P
in × 100) at one sun condition (100mW/cm2). The good interfacial contact between the electrolytes and the dye-attached nanocrystalline TiO2 layers were verified by field-emission scanning electron microscopy.
Ionics 03/2008; 14(2):143-148. · 1.29 Impact Factor
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ABSTRACT: A new molecular thermodynamic model to predict the dependency of the glass transition temperature (Tg) of polymer on its molecular weight was developed based on the configurational entropy model and the Flory–Huggins theory. In this model, the disorientation entropy of the polymer (Sdis) has been taken into account. Quantitative descriptions according to the proposed model are consistent with experimental Tg data of several polymers against the number of chain segment (r). At the same Tg.∞ (Tg of polymer at a infinite r value), the degree of polymer disorientation is strongly correlated with the slope of straight line at lower r regions in the Tg versus r plot, which is quantitatively identified by physical parameter (dis) in this model. Copyright © 2008 John Wiley & Sons, Ltd.
Polymers for Advanced Technologies 03/2008; 19(8):944 - 946. · 2.01 Impact Factor
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ABSTRACT: In this study, poly(vinylidene fluoride-co-chlorotrifluoroethylene)-graft-poly(oxyethylene methacrylate), P(VDF-co-CTFE)-g-POEM, an amphiphilic comb copolymer with hydrophobic P(VDF-co-CTFE) backbone and hydrophilic POEM side chains at 73:27 wt % was synthesized. The POEM side chains were grafted from the P(VDF-co-CTFE) mainchain backbone via atom transfer radical polymerization (ATRP) using direct initiation of the chlorine atoms in CTFE units. Synthesis of microphase-separated P(VDF-co-CTFE)-g-POEM comb copolymer was successful, as confirmed by nuclear magnetic resonance (1H NMR), FTIR spectroscopy, and transmission electron microscopy (TEM). Nanocomposite films were prepared using the comb copolymer as a template film and the in situ reduction of AgCF3SO3 precursor to silver nanoparticles under UV irradiation. Silver nanoparticles with 4–8 nm in average size were in situ created in the solid state template film, as revealed by TEM, UV–visible spectroscopy, and wide angle X-ray scattering (WAXS). Differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) presented the selective incorporation and the in situ growth of silver nanoparticles within the hydrophilic POEM domains of microphase-separated comb copolymer film. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 702–709, 2008
Journal of Polymer Science Part B Polymer Physics 02/2008; 46(7):702 - 709. · 1.53 Impact Factor
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ABSTRACT: The direct preparation of proton conducting poly(vinyl chloride) (PVC) graft copolymer electrolyte membranes using atom transfer radical polymerization (ATRP) is demonstrated. Here, direct initiation of the secondary chlorines of PVC facilitates grafting of a sulfonated monomer. A series of proton conducting graft copolymer electrolyte membranes, i.e. poly(vinyl chloride)-g-poly(styrene sulfonic acid) (PVC-g-PSSA) were prepared by ATRP using direct initiation of the secondary chlorines of PVC. The successful syntheses of graft copolymers were confirmed by 1H-NMR and FT-IR spectroscopy. The images of transmission electron microscopy (TEM) presented the well-defined microphase-separated structure of the graft copolymer electrolyte membranes. All the properties of ion exchange capacity (IEC), water uptake, and proton conductivity for the membranes continuously increased with increasing PSSA contents. The characterization of the membranes by thermal gravimetric analysis (TGA) also demonstrated their high thermal stability up to 200°C. The membranes were further crosslinked using UV irradiation after converting chlorine atoms to azide groups, as revealed by FT-IR spectroscopy. After crosslinking, water uptake significantly decreased from 207% to 84% and the tensile strength increased from 45.2 to 71.5 MPa with a marginal change of proton conductivity from 0.093 to 0.083 S cm−1, which indicates that the crosslinked PVC-g-PSSA membranes are promising candidates for proton conducting materials for fuel cell applications. Copyright © 2008 John Wiley & Sons, Ltd.
Polymers for Advanced Technologies 01/2008; 19(7):915 - 921. · 2.01 Impact Factor
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ABSTRACT: A supramolecular material containing quadruple hydrogen bonding sites was prepared by reacting the amines of methyl isocytosine and the epoxy groups of poly (ethylene glycol diglycidyl ether). This supramolecular polymer was complexed with metal salt, that is potassium iodide, to produce polymer electrolytes, and their physical properties, specific interactions, and conductivity behavior were investigated. The ionic conductivity of polymer electrolytes continuously increased with increasing salt concentration up to 0.4 of salt weight fraction, presenting usually high solubility limit of salt in the supramolecular polymer. Wide angle X-ray scattering data also presented that the metal salt was completely dissolved in the supramolecular polymer up to 0.4 of salt weight fraction. Upon the introduction of metal salt, the mechanical properties of the supramolecular polymer were significantly enhanced by around 10 times and the glass transition temperature of the polymer increased by about 50 °C, as revealed by complex melt viscosities and differential scanning calorimetry. These unusual behaviors of salt solubility and mechanical properties for supramolecular polymer/metal salt complexes were attributed to the strong, additional metal ion coordination to hydrogen bonding sites as well as ether oxygens of polymer matrix, as supported by FTIR spectroscopy. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 3181–3188, 2007
Journal of Polymer Science Part B Polymer Physics 10/2007; 45(23):3181 - 3188. · 1.53 Impact Factor
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ABSTRACT: Solid-state dye-sensitized solar cells (DSSCs) have been constructed employing supramolecular electrolytes with multiple hydrogen bonding. A supramolecule was facilely synthesized by one-pot reaction between the amines of methyl isocytosine (MIC) and the epoxy groups of poly(ethylene glycol diglycidyl ether) (PEGDGE) to produce quadruple hydrogen bonding units. Hydrogen bonding interactions and dissolution behavior of salt in supramolecular electrolytes are investigated. The ionic conductivity of the supramolecular electrolytes with ionic liquid, i.e. 1-methyl-3-propylimidazolium iodide (MPII) reaches 8.5 × 10−5 S/cm at room temperature, which is higher than that with metal salt (KI). A worm-like morphology is observed in the FE-SEM micrographs of TiO2 nanoporous layer, due to the connection of TiO2 nanoparticles resulting from adequate coating by electrolytes. DSSCs employing the supramolecular electrolytes with MPII and KI exhibit an energy conversion efficiency of 2.5% and 0.5%, respectively, at 100 mW/cm2, indicating the importance of the cation of salt. Solar cell performances were further improved up to 3.7% upon tuning interaction strength in the electrolytes.
Electrochimica Acta. 55(7):2567-2574.
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ABSTRACT: Poly(ethylene glycol) (PEG) was modified with a long alkyl acid to produce a self-organized amphiphilic polymer (amPEG). FT-IR and NMR spectroscopies confirmed the amPEG synthesis. This polymer was complexed with lithium iodide (LiI) and 1-methyl-3-propylimidazolium iodide (MPII) to prepare polymer electrolytes to be applied to dye-sensitized solar cells (DSSC). FT-IR studies showed that upon the addition of litium salt the free ether and ester carbonyl bands shifted towards lower wavenumbers, indicating the complexation of Li ions with oxygens on the amPEG. Alkylation and salt introduction reduced PEG crystallinity, as characterized by wide angle X-ray scattering (WAXS) and differential scanning calorimetry (DSC). The ionic conductivities of the polymer electrolytes increased with increasing salt concentrations, and the energy conversion efficiency of DSSC reached 2.6% at 100 mW cm−2 for amPEG/MPII system which is higher than amPEG/LiI. This may be due to the higher mobility of MPII ion than the lithium ion in the polymer electrolyte. The interfacial properties between electrolytes and electrodes were investigated using field-emission scanning electron microscopy (FE-SEM) and electrochemical impedance spectroscopy (EIS).
Journal of Photochemistry and Photobiology A: Chemistry. 217(1):169-176.
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ABSTRACT: Porous TiO2 thin films have been prepared using an amphiphilic graft copolymer, i.e. poly(vinylidene fluoride-co-chlorotrifluoroethylene)-graft-poly(oxyethylene methacrylate) (P(VDF-co-CTFE)-g-POEM) as a structure-directing agent via the sol–gel process. The graft copolymer was synthesized via atom transfer radical polymerization using CTFE units as an initiating site and designed to have a hydrophobic P(VDF-co-CTFE) domain and a hydrophilic POEM domain. Fourier transform-infra red spectroscopy indicated that a hydrophilic titania precursor was selectively incorporated into hydrophilic POEM domains. In-situ formation and morphologies of porous TiO2 thin films were confirmed by ultraviolet–visible spectroscopy, X-ray diffraction, transmission electron microscopy and thermogravimetric analysis. The resultant porous TiO2 films with 10–25 nm in size were used as a photoelectrode for solid-state dye-sensitized solar cells, exhibiting energy conversion efficiency of 2.8% at 100 mW/cm2.
Thin Solid Films.
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ABSTRACT: A novel ABA-type triblock copolymer, i.e. poly(oxyethylene methacrylate)-b-polystyrene-b-poly(oxyethylene methacrylate) (POEM-b-PS-b-POEM) was synthesized via atom transfer radical polymerization (ATRP). This amphiphilic triblock copolymer was used to template the growth of TiO2 from a titanium isopropoxide through sol–gel process in the solid state film. The hydrophilic titania precursor was selectively incorporated into hydrophilic POEM domains and formed TiO2 nanoparticle arrays, mostly due to microphase separation between the PS domains and the POEM/TiO2 domains. High-density arrays of TiO2 nanoparticles with 30–40 nm size after calcinations at 550 °C were confirmed by X-ray photoelectron spectroscopy (XPS), UV–vis spectroscopy, wide angle X-ray scattering (WAXS) and transmission electron microscopy (TEM). The resultant TiO2 nanoparticles showed high photocatalytic activity on the photodegradation of humic acid.
Colloids and Surfaces A: Physicochemical and Engineering Aspects.
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ABSTRACT: A novel amphiphilic comb-like copolymer consisting of poly(vinyl chloride) (PVC) main chains and poly(4-vinyl pyridine) (P4VP) side chains, i.e. PVC-g-P4VP with 65:35 wt% is synthesized via atom transfer radical polymerization (ATRP). This self-assembled copolymer is used to template the growth of silver bromide (AgBr) nanoparticles with diameters of 10–50 nm, as characterized by UV–vis spectroscopy, X-ray diffraction (XRD) and transmission electron microscopy (TEM). Upon introduction of ionic liquid, i.e. 1-methyl-3-octylimidazolium nitrate (MOIM+NO3−), the surface of AgBr nanoparticles is more partially positively charged due to the interactions between NO3− ions and the surfaces of nanoparticles, as revealed by FT-Raman and X-ray photon spectroscopy (XPS). We also demonstrate the ability of AgBr as a new type of olefin carrier by tuning the interactions of positively charged AgBr with the CC bond of olefin molecules. As a result, the membranes containing AgBr nanocomposites exhibit highly stable separation performances for propylene/propane mixture, i.e. a mixed gas selectivity of 6 and a permeance of 5.7 GPU.
Journal of Membrane Science.
