The study on the conductivity of styrene-maleic anhydride copolymer electrolytes based on poly(ethylene glycol)400 and LiClO4

Polyelectrolytes, in this study were synthesized from styrene-maleic anhydride (SMA) copolymer, poly(ethylene glycol)400 (PEG400), and lithium perchlorate (LiClO₄). Fourier transform infrared spectroscopy (FTIR), and magic angle spinning (MAS) solid-state NMR were used to monitor the interaction between Li⁺ ions and polymer. The results of FTIR and MAS solid-state NMR indicate the Li⁺ ions are preferentially coordinated to the ether oxygen of PEG. The T_g of the PEG segments in polyelectrolyte increases with LiClO₄ concentration, as determined by differential scanning calorimetry (DSC), indicating that solubility of the Li⁺ ions in the host polymer increases with the PEG content. Impedance spectroscopy (IS) shows that the bulk conductivity of polyelectrolytes and the conductivity behavior obeys the Vogel-Tamman-Fulcher (VTF) equation.     

Studies on comb-like polymer electrolyte with a nitrile group

The behavior of lithium ions in a comb-like polymer electrolyte with a nitrile group has been characterized by differential scanning calorimeter (DSC), thermogravimetric analysis (TGA), ac impedance, Fourier transform infrared (FTIR) spectroscopy, and solid-state NMR measurements. The comb-like copolymer is synthesized by poly(ethylene glycol-methyl ether methacrylate) (PEGMEM) and acrylonitrile (AN). FTIR spectra reveal the interactions of Li⁺ ions with both the ether oxygen of the PEGMEM and the nitrogen atom of the AN segments. solid-state NMR spectra demonstrate the interactions of Li⁺ ions with both the ether oxygen of the PEGMEM and the nitrogen atom of the AN segments. Moreover, solid-state NMR shows that the lithium ions are preferentially coordinated to the PEGMEM segment. The T_g increases for the copolymers doped with LiClO₄. These results indicate the interactions of Li⁺ with both PEGMEM and AN segments form transient cross-links. The dependence of the maximum conductivity on the doping lithium ion concentration was determined. The AN unit in the copolymer improves the dissociation of the lithium salt, and the mechanical strength.     

Synthesis and characterization of side-chain liquid crystalline polymers and oriented elastomers containing terminal perfluorocarbon chains

Several novel chiral side-chain liquid crystalline (LC) polysiloxane resins containing epoxy groups and mesogenic components have been graft copolymerized by a one-step hydrosilylation reaction with poly(methylhydrogeno)siloxane, an epoxy monomer 2-(allyloxymethyl)oxirane, and chiral fluorinated liquid-crystalline monomers 4′-(4-(allyloxy)benzoyloxy)biphenyl-4-yl 6-(perfluorooctanoyloxy)hexahydrofuro[3,2-b]furan-3-yl adipate and 4′-(4-(undec-10-enoyloxy)benzoyloxy)biphenyl-4-yl 6-(perfluorooctanoyloxy)hexahydrofuro[3,2-b]furan-3-yl adipate. The synthesized epoxy resins are cured using 4,4′-diaminodiphenyl-methane in mesophase state under a magnetic field to obtain crosslinked oriented elastomers. The chemical structures, LC properties and surface morphology of the monomers, the resins and the liquid crystalline elastomers (LCEs) are characterized by use of various experimental techniques such as FTIR, ¹H NMR, EA, TGA, DSC, POM, and X-ray measurements. The mesomorphic properties of the synthesized resins and corresponding oriented elastomers are influenced by the terminal perfluorocarbon chains components effectively. The resins show chiral nematic and chiral smectic C phases (), and are frozen in their corresponding oriented elastomers. The LC phases are verified by X-ray measurements, and the orientational order parameters of the oriented LCEs are calculated as well.     

Melt complex viscosity and molecular weights for homo-polypropylene modified by grafting bifunctional monomers under electron beam irradiation

High melt viscosity polypropylene was manufactured by grafting bifunctional monomers, HDDA (1,6-hexanediol diacrylate) and TPGDA (tripropyleneglycol diacrylate), onto homo-polypropylene under an electron beam irradiation. Melt complex viscosity (η^∗) of modified polypropylene was sensitive to irradiation dose and monomer content. The melt viscosity of the polypropylene modified with TPGDA increased to 132,290 Pa s (at 190 °C and 0.1 rad/s of frequency) from 5039 Pa s for virgin homo-polypropylene. TPGDA monomer could give higher melt viscosity at low dosages than HDDA monomer, probably due to the structural feature of TPGDA with three numbers of methyl groups.Modified polypropylene with high melt complex viscosity had a broad molecular weight distribution with remarkable shift to higher molecular weight leading to high values of both and . Melt viscosity of modified polypropylene could be properly correlated by the equation , where the term gave a dominant effect for the estimation of η^∗.     

Kinetic analysis on LiFePO4 thin films by CV, GITT, and EIS

LiFePO₄ thin films were deposited on Ti substrates by pulsed laser deposition (PLD). The apparent chemical diffusion coefficients of lithium in the films, , were measured by cyclic voltammetry (CV), galvanostatic intermittent titration technique (GITT), and electrochemical impedance spectroscopy (EIS). The average values calculated from CV results were in the order of 10⁻¹⁴ cm² s^–1. The values obtained by GITT, and EIS techniques were in the range of 10^–14–10^–18 cm² s^–1, 10^–14–10^–18 cm² s^–1, respectively. The values obtained by the two methods show a minimum point at x ∼ 0.5 for Li_1−xFePO₄. However, the overpotential values of the LiFePO₄ thin film electrodes obtained from the GITT results and the diffusion impedance deduced from the impedance spectra also show the minimum values at x ∼ 0.5 for Li_1–xFePO₄. This contradict could be caused by the improper use of GITT and EIS techniques for measuring the chemical diffusion coefficient of Li in Li_1–xFePO₄ which constitutes two phase, i.e., LiFePO₄ and FePO₄ in this region.     

Criteria dilemma of phase behavior in ternary blends comprising polystyrene, poly(alpha-methyl styrene), and poly(4-methyl styrene)

A ternary blend system of polystyrene (aPS), poly(α-methyl styrene) (PαMS), and poly(4-methyl styrene) (P4MS) (blends of three styrenic homopolymers of similar molecular structures) was investigated by using differential scanning calorimetry (DSC), polarized-light optical microscopy (POM), scanning electron microscopy (SEM), and solid-state ¹³C cross-polarization/magic angle spinning nuclear magnetic resonance (CP/MAS NMR). This ternary system of aPS/PαMS/P4MS exhibits a small miscibility loop only at relatively high percentages of PαMS (≥80%), while most of the aPS/PαMS/P4MS compositions exhibit two coexisting aPS/PαMS and aPS/P4MS phases in the immiscibility loop. In the immiscible loop, SEM measurements revealed evidence in contrasting with DSC for criteria of miscibility. DSC characterization revealed a single T_g for most ternary blend compositions; however, SEM graphs apparently indicated sub-micron phase domains, except for several PαMS-rich compositions (>80%). The and techniques using NMR were found to resolve the dilemma between the conventional thermal analysis and microscopy results, and indeed supported that the ternary blends at above 80% PαMS are completely homogeneous on the molecular level. Attempts have been made to resolve the seemingly contradictory interpretations on the complex ternary phase structures and domains from the DSC, and microscopy results.     

Catalytic NO–H2–CO–O2 reactions over Pt-supported mesoporous yttrium oxide

Catalytic light-off of a stream of NO, H₂, CO in an excess O₂ has been studied over various metal oxides loading 1 wt% Pt. Because a low-surface area Y₂O₃ (<5 m² g⁻¹) was found to exhibit the highest de-NO_x activity, a mesoporous Y₂O₃ was then synthesized from an yttrium-based surfactant mesophase templated by dodecyl sulfate , which was anion-exchanged by acetate (AcO = CH₃COO⁻). The product showed a 3-D mesoporosity with a large surface area (396 m² g⁻¹) and the Pt-supported catalyst achieved much improved light-off characteristics suitable for the low-temperature de-NO_x in the presence of CO and excess O₂.     

Theoretical study on morphology of ABCD 4-miktoarm star block copolymer

A real-space implementation of the self-consistent field theory (SCFT) has been used to study the morphologies of ABCD 4-miktoarm star block copolymers. For the sake of numerical tractability, the morphologies and the phase diagrams of ABCD 4-miktoarm star block copolymers are investigated in two dimensions (2D) by varying the volume fractions of the blocks and the interaction parameters. Many interesting and complex morphologies occur and compared with ABCD linear block copolymers; ABCD 4-miktoarm star block copolymers have more regular disciplines. We found that systems with similar components have similar morphologies and at the weaker segregation, the minority components always cannot separate from the other blocks and they easily dissolve to form one phase with other block(s), but with the increase of the segregation degree (large ), the ordered phases can be well separated. With the help of our computational prediction, experimental researchers can work more purposefully and efficiently.     

Surface enhanced infrared spectroscopy—Au(1 1 1-20 nm)/sulphuric acid—new aspects and challenges

The structure and orientation of water molecules on Au(1 1 1-20 nm) film electrodes in contact with aqueous sulphuric acid solution was studied by surface enhanced infrared reflection-absorption spectroscopy (SEIRAS) employing an attenuated total reflection (ATR) configuration (ATR-SEIRAS) with a vertical spectroelectrochemical cell. The spectrum of interfacial water is strongly dependent on electrode potential, ionic strength and pH. Coadsorption of hydronium ions with weakly hydrogen-bonded water molecules was found at E<E_pzc. At E>E_pzc strong hydrogen-bonding among water molecules and to coadsorbed sulphate species exists. Based on pH-dependent electrochemical, spectroscopic and in situ STM investigations, a new model is suggested to represent the ordered () adlayer at maximum sulphate coverage θ=0.2: a Zundel or hydrated hydronium ion H₅O₂⁺, in which one proton is shared between two water molecules, bridges adjacent sulphate species via hydrogen-bonds along the main diagonal of the () unit cell. This alternating arrangement gives rise to a long-range ordered, 2D network of sulphate and water species interconnected by hydrogen-bonds, and capable to form hydrogen-bonds with second-layer water species. The suggested model is consistent with all experimental observations as well as predictions from quantum-chemical and molecular dynamic simulations.     

Li-ion diffusion kinetics in LiFePO4 thin film prepared by radio frequency magnetron sputtering

LiFePO₄ thin films were prepared by radio frequency (RF) magnetron sputtering and were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM) and atomic force microscope (AFM). Li-ion chemical diffusion coefficients, , were measured by potentiostatic intermittent titration technique (PITT), electrochemical impedance spectroscopy (EIS), and cyclic voltammetry (CV). The effects of Ag content, film thickness, and film orientation on the electrochemical performance and Li-ion chemical diffusion coefficients of the LiFePO₄ thin films were investigated. values were measured using the liquid electrolyte and the solid electrolyte, and the obtained values were discussed. The values by PITT and EIS were in the range of 10⁻¹⁴ to 10⁻¹² and 10⁻¹⁵ to 10⁻¹² cm² s⁻¹, respectively and that by CV was in the order of 10⁻¹⁴ cm² s⁻¹.     

NMR evidence of different conformations of structure-directing cyclohexylamine in high-doped AlPO4-44 materials

A series of high-crystalline ZnAPSO-44 samples have been successfully synthesised using cyclohexylamine as structure-directing agent, keeping a constant (Si + Zn)/(Al + P) ratio of 0.25 and systematically varying the Si/Zn ratio. Chemical analyses by ICP shows a good correlation between the heteroatom (Si and/or Zn) content of the samples and that of the initial gels. A combination of single crystal and powder X-ray diffraction techniques evidences a high crystallinity and a total purity for all samples. In addition, single crystal X-ray diffraction studies of the samples from which large crystals could be isolated, allow us to certify that either the whole or the majority of the cyclohexylamine molecules adopt a NH₂- or -equatorial conformation inside of the pores. Furthermore, for the first time, ¹H MAS NMR spectroscopy was used as a proof of the protonation of SDA molecules within the microporous materials, unequivocally indicating that cyclohexylamine molecules were protonated. ¹³C MAS NMR studies indeed corroborated such protonation state of the SDA molecules and, more importantly, allowed to detect the presence of a mixture of -equatorial and -axial conformers of cyclohexylamine in the Si-richest samples, the former being always the dominant. Based on both ¹³C and ²⁹Si cross-polarization MAS NMR measurements as well as on the calculated interaction energies of the two conformers as a function of the framework composition, it is proposed that this non-described -axial conformation of cyclohexylammonium within the microporous materials was associated to the presence of SiO₂ islands into the AlPO₄ framework, whereas the -equatorial conformer was the only one found in the case of isolated incorporation of Si⁴⁺ (and/or Zn²⁺) ions.     

Fabrication of electrochemically stable fluorinated nano-carbon film compared with other fluorinated carbon materials

We fabricated electrochemically stable fluorinated nano-carbon film that had an sp² and sp³ hybrid nanocrystalline structure formed using the electron cyclotron resonance (ECR) sputtering method. This fluorinated ECR (F-ECR) nano-carbon film prepared with a short CF₄ plasma treatment has a high fluorine content (F/C:0.20) and a low oxygen content (O/C:0.02) on its surface and retains its original morphology. This F-ECR nano-carbon is capable of a lower capacitance current, and a wider potential window than untreated ECR nano-carbon. The electron transfer rates at an F-ECR electrode are as high as those of untreated carbons for , whereas they are much slower than those of untreated ECR nano-carbon for Fe^2+/3+ and owing to its selective sp² fluorination. These slow electron transfer rates for Fe^2+/3+ and are maintained during potential cycles due to its robust nanocrystalline structure. In contrast, these slow electron transfer rates were easily recovered for fluorinated glassy carbon under same condition. Furthermore, a smaller fluorination effect was observed for polycrystalline boron-doped diamond owing to the low reactivity of its sp³ bonds. Our ECR nano-carbon film is suitable for the effective fabrication of a fluorinated surface while maintaining a relatively active electrochemical interface and excellent stability.     

Li-ion diffusion kinetics in LiMn2O4 thin films prepared by pulsed laser deposition

LiMn₂O₄ thin films were deposited on Au substrates by pulsed laser deposition (PLD). The Li-ion chemical diffusion coefficients of the films, , were measured by cyclic voltammetry (CV), galvanostatic intermittent titration technique (GITT), potentiostatic intermittent titration technique (PITT), and electrochemical impedance spectroscopy (EIS). It was found that the values by CV and PITT were in the order of 10⁻¹³ cm² s⁻¹, and those by EIS and GITT were in the range of 10⁻¹³ to 10⁻¹¹ and 10⁻¹⁴ to 10⁻¹¹ cm² s⁻¹, respectively. These data were compared with the previously reported values.     

Effect of N(4)-substituent groups on transfer of 2-benzoylpyridine thiosemicarbazone derivates at the water/1,2-dichloroethane interface

Dependent on the pH of the aqueous phase, the transfer of protonated forms of 2-benzoylpyridine N(4)-phenyl thiosemicarbazone (BPPT) (which has antimicrobial, antifungal and anticytotoxic activities) and 2-benzoylpyridine N(4)-ethyl thiosemicarbazone (BPET) across water/1,2-dichloroethane (1,2-DCE) interface has been studied by cyclic voltammetry. The protonation constants of the ligands ( and ) were determined by spectrophotometry. The standard partition coefficients () and the standard Gibbs energies of ionic (cationic) species of ligands () were calculated from the standard transfer potentials (). The standard Gibbs energies of their transfer () and partition coefficients of neutral species (log P_N) were determined by shake-flask method. These thermodynamic parameters were evaluated as a quantitative and qualitative measure of the lipophilicities of two compounds. The differences between the partition coefficients of cationic and neutral form of compounds [diff(log PI⁺−N)] were interpreted by results obtained from voltammetric data. Effect of N(4)-phenyl and ethyl groups for transfer of 2-benzoylpyridine thiosemicarbazone derivatives at macro-liquid/liquid interface was investigated. The antimicrobial activity of BPET was tested against four types of bacteria and found to be active against Staphlylococcus aureus.     

Electrochemical performances of gel polymer electrolytes using tetra(ethylene glycol) diacrylate

A gel polymer electrolyte (GPE) was prepared using tetra(ethylene glycol) diacrylate monomer, benzoyl peroxide, and (). The LiCoO₂/GPE/graphite cells were prepared and their electrochemical properties were evaluated at various current densities and temperatures.The viscosity of the precursor containing the tetra(ethylene glycol) diacrylate monomer was around . The ionic conductivity of the gel polymer electrolyte at 20°C was around . The gel polymer electrolyte had good electrochemical stability up to vs. Li/Li⁺. The capacity of the LiCoO₂/GPE/graphite cell at rate was 63% of the discharge capacity at rate. The capacity of the cell at −10°C was 81% of the discharge capacity at 20°C. Discharge capacity of the cell with gel polymer electrolyte was stable with charge-discharge cycling.