Synthesis, structure characterization and ionic conductivity of star-branched organic-inorganic hybrid electrolytes based on cyanuric chloride, diamine-capped poly(oxyalkylene) and alkoxysilane

A synthesis route for preparing highly conductive solid organic-inorganic hybrid electrolytes has been developed by using cyanuric chloride as the coupling core to react with diamino-terminated poly(oxyalkylene) triblock copolymers, followed by cross-linking with an epoxy alkoxysilane 3-glycidyloxypropyl trimethoxysilane via a sol-gel process. The present hybrid electrolyte with a [O]/[Li] ratio of 32 was found to be the most conductive, reaching a maximum lithium ion conductivity of 6.8 × 10⁻⁵ Scm⁻¹ at 30 °C. The Li-ion mobility was determined from ⁷Li static NMR line width measurements and correlated with their ionic conductivities. The onset of ⁷Li line narrowing was closely related to the T_g of the hybrid electrolytes as measured by DSC experiments. Thus, the motions of the lithium cations are strongly coupled with the segmental motion of the polymer chains, which is in line with the Vogel-Tamman-Fulcher behavior as observed in ionic conductivity.     

A highly conductive organic-inorganic hybrid electrolyte based on co-condensation of di-ureasil and ethylene glycol-containing alkoxysilane

Organic-inorganic hybrid electrolytes based on di-ureasil backbone structures by reacting poly(propylene glycol)-block-poly(ethylene glycol)-block-poly(propylene glycol) bis(2-aminopropyl ether) (ED2000) with 3-(triethoxysilyl)propyl isocyanate (ICPTES), followed by co-condensation with methoxy(polyethylenoxy)propyl trimethoxysilane (MPEOP) in the presence of LiClO₄ were prepared and characterized by a variety of techniques. The hybrid electrolytes showed good resistance to crystallization and excellent conductivity for use in lithium-ion batteries, as determined by differential scanning calorimetry (DSC) and impedance measurements, respectively. The temperature dependence of the ionic conductivity exhibited a VTF (Vogel-Tamman-Fulcher)-like behavior for all the compositions studied and a maximum ionic conductivity value of 6.9 × 10⁻⁵ S cm⁻¹, a relatively high value for solid polymer electrolytes, was achieved at 30 °C for the hybrid electrolyte with a [O]/[Li] ratio of 16. A microscopic view of the dynamic behavior of the polymer chains (¹³C) and the ionic species (⁷Li) was provided by the ¹H and ⁷Li line widths measured from 2D ¹H-¹³C WISE (Wideline Separation) and variable temperature ⁷Li static NMR, respectively, to elucidate the influence of the mobility of the polymer chains and the charge carriers on the observed ionic conductivity. The present salt-free hybrid electrolyte after plasticization with 1 M LiClO₄ in EC/PC solution exhibited a swelling ratio of 275% and reached an ionic conductivity value up to 8.3 × 10⁻³ S cm⁻¹ at 30 °C, which make it a good candidate for the further development of advanced rechargeable lithium-ion batteries.     

Li NMR, ionic conductivity and self-diffusion coefficients of lithium ion and solvent of plasticized organic-inorganic hybrid electrolyte based on PPG-PEG-PPG diamine and alkoxysilanes

Organic-inorganic hybrid electrolytes based on poly(propylene glycol)-block-poly(ethylene glycol)-block-poly(propylene glycol) bis(2-aminopropyl ether) (D2000) complexed with LiClO₄ via the co-condensation of an epoxy trialkoxysilane and tetraethoxysilane have been prepared and plasticized by a solution of ethylene carbonate (EC)/propylene carbonate (PC) mixture (1:1 by weight). The cross-linked hybrid network shows no solvent exudation and retains a large amount of plasticizer over 70 wt.% in stable state. The in situ built in silica network provides the hybrid electrolytes with good mechanical properties. The ionic conductivity of the dry hybrid electrolyte films was enhanced by two orders of magnitude via plasticization, reaching a maximum conductivity value of 4.0 × 10⁻³ S/cm at 30 °C. Variable temperature ⁷Li-{¹H} magic angle spinning (MAS) NMR demonstrated that the Li⁺ cations can be complexed by the polymer network as well as by the plasticizing solvents, but not with the incorporated silica network. Furthermore, the ⁷Li chemical shift change indicated a progressive change in the lithium coordination from lithium-polymer to lithium-solvent with increasing temperatures. The role of the solvents and the mobility of the lithium ions were investigated by pulsed gradient spin echo (PGSE) NMR measurements to elucidate the behavior of the ionic conductivity.     

Toward UV-curable urethane acrylate/silica hybrid coatings: Introducing urethane methacrylate trimethoxysilane (UAMS) as organic–inorganic coupling agent

Urethane methacrylate trimethoxysilane (UAMS) organic–inorganic material was synthesized by the reaction of isophorone diisocyanate with hydroxyethyl methacrylate and aminopropyltrimethoxysilane. This precursor was then added to urethane trimethacrylate (UTMA); consequently, silica domains were appeared within the resulting ultraviolet (UV)-irradiated hybrid coatings. The sol–gel precursors having different amounts of UAMS as well as the UV-irradiated nanocomposite specimens were thoroughly characterized by FTIR, ¹H NMR, ¹³C NMR, SEM, and TGA. The results provided support for the fact that thermo-mechanical properties of hybrid coatings were enhanced markedly by the incorporation of UAMS. This can be explained by the generation of Si–O–Si hard segments throughout the UV-cured films. Study on hardness and thermal stability behavior provided further evidences for the action of UAMS as coupling agent. Noticeably, thermal stability of hybrid coatings experienced an upward trend with the UAMS content, which can be inferred on the basis of strict restrictions on the mobility of polymer chains imposed by the crosslinked network.     

NMR, conductivity and DSC study of Li transport in ethylene glycol/citric acid polymer gel

In this present paper the influence of viscosity on the ionic dynamics of polymer gel electrolytes prepared by the Pechini polymeric precursor method is investigated by impedance spectroscopy, differential scanning calorimetric (DSC) and NMR techniques. Polymer gel electrolytes are formed by ethylene glycol (EG) and citric acid (CA) and lithium perchlorate. Room temperature conductivity of the order of 2.3 × 10⁻⁴ S/cm was obtained for the sample of EG/CA:LiClO₄ with lower viscosity (η = 197 cP). The results show that the ionic conductivity of the electrolytes increases for decreasing viscosity. Proton (¹H) and Lithium (⁷Li) NMR lineshapes and spin-lattice relaxation times were measured as a function of temperature and viscosity (197-868 cP). The ⁷Li relaxation process was found to be dominated by quadrupolar couplings. The activation energy extracted from the ¹H and ⁷Li relaxation data (∼0.23 eV) was found to be independent of the viscosity of the gel electrolyte. The ⁷Li NMR relaxation results indicate an increase of the lithium ion mobility with decreasing viscosity.     

The study on the conductivity and morphology of polyurethaneurea electrolytes based on poly(ethylene glycol) 2000 and LiClO4

Polyurethaneureas (PUU), which were synthesized from 4,4′-diphenylmethane diisocyanate (MDI), poly(ethylene glycol) (PEG, MW=2000), and 3,5-diaminobenzoic acid, were used as the matrix of the polyelectrolytes in this study. Differential scanning calorimetry (DSC), Fourier-transform infrared spectroscopy (FT-IR), and ⁷Li magic angle spinning (MAS) solid-state NMR were used to monitor changes in the morphology of PUU electrolytes corresponding to the concentration of lithium perchlorate (LiClO₄) dopants. The results of DSC and FT-IR indicate the different polymer complexes formed by the interaction of the Li⁺ ions with the different coordination sites of PUU. The ⁷Li MAS solid-state NMR investigation of the PUU electrolytes points out that two different Li⁺ environments exist at lower temperature. The results of DSC and the ⁷Li MAS solid-state NMR show that Li⁺ ions are preferentially coordinated to the ether oxygen of the PEG soft-segment when the salt concentration is below 0.1 mmol LiClO₄(gPUU)⁻¹. Impedance spectroscopy measurements show that the conductivity behavior followed the Arrhenius equation and was influenced by the hard-segment T_g. One of the PUU electrolytes under the investigation has an ionic conductivity as high as 3.0×10⁻⁵ S cm⁻¹ at 30 °C.     

The environment of lithium ions and conductivity of comb-like polymer electrolyte with a chelating functional group

The behavior of lithium ions in a comb-like polymer electrolyte with a chelating functional group have been characterized by differential scanning calorimeter (DSC), dynamic mechanical analysis (DMA), Fourier transform infrared (FTIR) spectroscopy, ac impedance and ⁷Li solid-state NMR measurements. The comb-like copolymer is synthesized by poly(ethylene glycol-methyl ether methacrylate) (PEGMEM) and (2-methylacrylic acid 3-(bis-carboxymethylamino) -2-hydroxy-propyl ester) (GMA-IDA). FTIR and ⁷Li solid-state NMR spectra demonstrate the interactions of Li⁺ ions with both the ether oxygen of the PEGMEM and the nitrogen atom of the GMA-IDA segments. Moreover, ⁷Li solid-state NMR shows that the lithium ions are preferentially coordinated to the GMA-IDA segment. The T_g increases for the copolymers doped with LiClO₄. These results indicate the interactions of Li⁺ with both PEGMEM and GMA-IDA segments form transient cross-links. The Vogel-Tamman-Fulcher (VTF)-like behavior of conductivity implies the coupling of the charge carriers with the segmental motion of the polymer chains. The dependence of the maximum conductivity on the composition of the copolymers and the doping lithium ion concentration was determined. The GMA-IDA unit in the copolymer improves the dissociation of the lithium salt, the mechanical strength and the conductivity.     

A covalent organic/inorganic hybrid proton exchange polymeric membrane: synthesis and characterization

Commercial polyetheretherketone (Victrex PEEK) was sulfonated up to 90% degree of sulfonation (DS), then reacted with SiCl₄ to obtain a hybrid polymer. The product was characterized by ²⁹Si NMR and ATR/FTIR spectroscopies demonstrating the formation of covalent bonds between the organic and inorganic components. No dispersed inorganic silicon was present in the product as evidenced by the lack of any resonance at δ<−100 ppm. Despite the high DS the physicochemical properties of the hybrid were suitable for the preparation of membranes exhibiting high and stable conductivity values (10⁻² S/cm), hence suitable for application as ion exchange membrane.     

Nuclear magnetic resonance and conductivity study of hydroxyethylcellulose based polymer gel electrolytes

Polymer gel electrolytes formed by hydroxyethylcellulose (HEC) plasticized with glycerol and containing lithium perchlorate were studied by nuclear magnetic resonance spectroscopy (NMR) and complex impedance spectroscopy. In heavily plasticized samples, results show that the addition of solvent enhances the conductivity, which reaches 6 × 10⁻⁵ S/cm at room temperature. The ⁷Li NMR results indicate that this enhancement is associated with a decoupling of the lithium-ion dynamics from the local motion of the polymer host, with the increase in the mobility of the ionic species, and with the increase of the charge carrier concentration resulting from the salt dissociation after addition of the solvent. The temperature dependence of the lithium NMR spin-lattice relaxation is interpreted assuming that there are two distinct lithium-ion dynamics. The corresponding NMR relaxation processes are characterized by activation energies of 0.3 and 0.12 eV, respectively.     

Synthesis and proton conducting properties of zirconia bridged hydrocarbon/phosphotungstic acid hybrid materials

Recently, the organic/inorganic hybrid materials with flexibility, thermal, and chemical stabilities are extensively studied for the application of temperature tolerant polymer electrolyte fuel cells. This paper reports the preparation and properties of sol-gel derived proton conducting organic/inorganic materials based on zirconia bridged hydrocarbon phosphotungstic acids. The materials are molecular hybrids where linear hydrocarbons such as trimethylene glycols (TMGs) or octamethylene glycols (OMGs) are covalently bonded to zirconia interface to form macromolecular organic/inorganic networks. The hybrid materials become proton conducting polymer electrolytes by the addition of 12-phosphotungstic acids. The hybrid materials showed high thermal stability, and high protonic conductivity of 4×10⁻³ S cm⁻¹ under saturated humidity condition at 150 °C. The materials can be expected to be used for the application of temperature tolerant polymer electrolyte fuel cell.     

Proton conducting polydimethylsiloxane/zirconium oxide hybrid membranes added with phosphotungstic acid

Inorganic polymer based hybrid membranes consisting of zirconium oxide and polydimethylsiloxane (PDMS) have been synthesized by sol-gel processes. The organic/inorganic polymeric hybrid membranes showed thermal stability and flexibility up to 300 °C. The membrane becomes proton conducting polymer electrolyte when added with 12-phosphotungstic acid (PWA). The conductivity of the membranes was measured in the temperature range from room temperature to 150 °C under saturated humidity and a maximum conductivity of 5×10⁻⁵ S cm⁻¹ was obtained at 150 °C.     

Solid polymer electrolytes V: microstructure and ionic conductivity of epoxide-crosslinked polyether networks doped with LiClO4

A crosslinked polyether network was prepared from poly(ethylene glycol) diglycidyl ether (PEGDE) cured with poly(propylene oxide) polyamine. Significant interactions between ions and polymer host have been observed for the crosslinked polyether network in the presence of LiClO₄ by means of FT-IR, DSC, TGA, and ⁷Li MAS solid-state NMR. Thermal stability and ionic conductivity of these complexes were also investigated by TGA and AC impedance measurements. The results of FT-IR, DSC, TGA and ⁷Li MAS solid-state NMR measurements indicate the formation of different types of complexes through the interaction of ions with different coordination sites of polymer electrolyte networks. The dependence of ionic conductivity was investigated as a function of temperature, LiClO₄ concentration and the molecular weight of polyether curing agents. It is observed that the behavior of ion transport follows the empirical Vogel-Tamman-Fulcher (VTF) type relationship for all the samples, implying the diffusion of charge carrier is assisted by the segmental motions of polymer chains. Moreover, the conductivity is also correlated with the interactions between ions and polymer host, and the maximum ionic conductivity occurs at the LiClO₄ concentration of [O]/[Li⁺]=15.     

Synthesis of novel UV-curable difunctional thiourethane methacrylate and studies on organic–inorganic nanocomposite hard coatings for high refractive index plastic lenses

This study relates to the development of ultraviolet (UV)-curable, organic–inorganic nanocomposite hard coatings for plastic lens substrates, especially for polythiourethane (PTU) and polycarbonate (PC). Novel difunctional thiourethane methacrylate (mercaptoethylsulfide-thiourethane methacrylate: coded MES-TUMA and isophorone diisocyanate-mercaptoethylsulfide-thiourethane methacrylate: coded IPDI-MES-TUMA) was synthesized to enhance the adhesive strength for PTU. On the basis of IR, ¹H NMR, electron spray ionisation-mass spectrometry (ESI-MS) analysis and gel permeation chromatography (GPC), the expected structures were confirmed. These difunctional thiourethane methacrylates were easily mixed with multifunctional urethane acrylate, surface-modified ZrO₂–TiO₂ nanoparticles and photoinitiator in coating formulations. The UV-cured organic–inorganic nanocomposites were very useful as hard coatings for high refractive index plastic lenses such as PTU and PC.     

Structural studies of sol–gel urea/polydimethylsiloxane barrier coatings and improvement of their corrosion inhibition by addition of various alkoxysilanes

A sol–gel organic–inorganic hybrid precursor, bis[(ureapropyl)triethoxysilane]bis(propyl)-terminated-polydimethylsiloxane 1000 (PDMSU, for short), was tested as a corrosion barrier coating for AA 2024 aluminium alloy. The PDMSU coatings were prepared in either ethanol (PDMSU/EtOH) or propanol (PDMSU/PrOH) solvents. XRD measurements of xerogels showed the diffraction peak of amorphous silica domains at 21.5° and a broad peak at approximately 12.2°, which could be associated with the presence of the polyhedral silsesquioxane structural units (T² and T³) determined in our previous investigations from the ²⁹Si NMR spectra. The structure of thin coatings on AA 2024 prepared by heat-treatment at 140 °C was studied with the surface-sensitive IR reflection–absorption (IR RA) spectroscopic technique. Results revealed that in both coatings the poly(dimethylsiloxane) (PDMS) chain segments were projecting from the metal surface, however, this effect was more pronounced for the PDMSU/PrOH than for the PDMSU/EtOH coatings. Information gathered from the structural studies (IR, IR RA, ²⁹Si NMR and XRD) enabled some correlations to be drawn between the coatings’ structure and the effectiveness of the corrosion inhibition, which was assessed from the potentiodynamic and salt-spray measurements. Results showed the improved corrosion inhibition of PDMSU/PrOH coatings attributed to their denser and more compact sol–gel network and also to their higher hydrophobicity, i.e. lower surface energy determined from the contact angle measurements. Addition of various tetraalkoxysilanes and alkyltriethoxysilanes further improved the corrosion inhibition of PDMSU coatings due to more extensive cross-linking. The salt-spray tests showed that tetraethoxysilane and phenyltriethoxysilane were the most effective additives.     

New highly conductive organic–inorganic hybrid electrolytes based on star-branched silica based architectures

A new type of organic–inorganic hybrid electrolyte has been developed by a sol–gel process through the reaction of cyanuric chloride with poly(oxyalkylene) diamine and 3-isocyanatepropyltriethoxysilane, followed by co-condensation of 2-[methoxy(polyethyleneoxy)propyl]trimethoxysilane. A maximum ionic conductivity of 1.0 × 10^?4 Scm^?1 at 30 °C has been achieved with the solid hybrid electrolyte. The results of solid-state NMR not only confirm the structural framework of the hybrids, but also provide a microscopic view of the effects of salt concentrations on the dynamic behavior of the polymer chains. The hybrid materials are blended with PVdF-HFP to form the blend hybrid membrane, followed by plasticization with various electrolyte solvents, with the purpose of increasing ionic conductivity. The plasticized blend hybrid electrolyte exhibits a maximum room temperature ionic conductivity of 8.8 × 10^?3 Scm^?1. Such a high ionic conductivity allows it as a potential candidate for applications in lithium ion batteries.     

Silver nanoparticles distributed into polyaniline bridged silica network: A functional nanocatalyst having synergistic influence for catalysis

A novel organic–inorganic hybrid nanocatalyst, Ag nanoparticles supported poly[N-(3-Trimethoxy silyl)propyl]aniline (Ag@PTMSPA), was prepared by a simple one-step method. X-ray diffraction analysis, field emission transmission electron microscopy and X-ray photo electron spectroscopy reveal the coexistence of Ag nanoparticles (average size ∼ 10 nm) and PTMSPA in Ag@PTMSPA. N₂ adsorption–desorption experiments provide the textural properties of the catalyst, such as surface area (86.6 m²/g), pore volume (1.3 × 10^− 1 cm³/g) and pore size (4.2 nm). UV–visible spectroscopy was used to follow the kinetics of reduction of 4-nitrophenol (4-NP) by sodium borohydride (NaBH₄) in the presence of Ag@PTMSPA catalyst.     

Study of ionic conductivity and microstructure of a cross-linked polyurethane acrylate electrolyte

A cross-linked polyurethane acrylate (PUA) was synthesized by end capping 4,4′-methylene bis(cyclohexyl isocyanate), H₁₂MDI/poly-(ethylene glycol), PEG based prepolymer with hydroxy ethyl acrylate (HEA). Significant interactions of the Li⁺ ions with the soft and hard segments of the host polymer have been observed for the PUA complexed with lithium perchlorate (LiClO₄) by means of differential scanning calorimetry (DSC), Fourier transform infra-red (FTIR) spectroscopy, ⁷Li magic angle spinning (MAS) NMR measurements and thermogravimetric analysis (TGA). The ⁷Li MAS NMR investigation of the PUA indicates the presence of at least three distinct Li⁺ sites at lower temperature, which merge to a single one at higher temperature in similar line with uncross-linked polyurethane. The results of TGA, DSC and FTIR spectroscopy support the formation of different types of complexes by the interaction of the Li⁺ ions with different coordination sites of PUA. No detectable interactions could be observed between Li⁺ ions and groups in HEA. The DSC data indicates the formation of transient cross-links with the ether oxygens of the soft segment and mixing of soft and hard phases induced by the Li⁺ ions. In addition, a Vogel-Tamman-Fulcher (VTF) like temperature dependence of ionic conductivity implies coupling of the ion movement with the segmental motion of the polymer chains in the cross-linked environment. Predominant formation of contact ion pairs of LiClO₄ has been consistently observed through AC conductivity, DSC and NMR spectroscopic results. Swelling measurements of PUA with plasticizers reveal the improved dimensional stability for these cross-linked PUA in comparison with uncross-linked polyurethane.     

Electrochemical study of tailored sol–gel thin films as pre-treatment prior to organic coating for AZ91 magnesium alloy

The behaviour/resistance of four optimised sol–gel coating systems (inorganic, hybrid organic–inorganic, containing zirconium ions and containing cerium ions) against corrosion of AZ91 magnesium alloy were studied. The coatings obtained by the sol–gel process were evaluated as autonomous protective coatings as well as a pre-treatment prior to acrylic top coat. The coating obtained from tetramethoxysilane (TMOS) and diethoxydimethylsilane (DEDMS) as precursors and doped with Ce³⁺ was especially effective as pre-treatment for a final acrylic coating. For non-defected coating the impedance modulus has not changed during the time of immersion (7 days) in 0.5 M Na₂SO₄. An inhibition of coating delamination at the defect of the acrylic coating was recorded by means of LEIS.     

Li NMR spectroscopy and ion conduction mechanism of composite gel polymer electrolyte: A comparative study with variation of salt and plasticizer with filler

Microporous composite gel polymer electrolyte (CGPE) has been prepared by incorporating the home-made silica aerogel (SAG) particles into the poly(vinylidene fluoride-co-hexafluoropropylene) (PVdF-HFP) copolymer/LiClO₄ matrix. The ionic transport behavior of the electrolyte is studied with various experimental techniques such as AC impedance, X-ray diffraction (XRD), infrared (IR) spectra, nuclear magnetic resonance (NMR), scanning electron microscopy (SEM), differential scanning calorimetry (DSC) and thermogravimetric analyzer (TGA), etc. The results reveal that the SAG particles are well dispersed in the electrolytes and incorporate with the other components of the CGPEs. The solid-state ⁷Li NMR study has confirmed the interactions of lithium ion with SAG, polymer and plasticizers, causing to form the microporous structure and reduce the glass transition temperature and crystallinity, resulting in an increase in ionic conductivity of the CGPE. The best ionic conductivity (1.04 × 10⁻² S/cm at room temperature) is obtained from the composite polymer electrolyte containing 4 wt% of SAG, which is approximately four times higher than the ionic conductivity of the electrolyte without the filler.     

Influence of molecular weight of PEG on the property of polymer gel electrolyte and performance of quasi-solid-state dye-sensitized solar cells

A new kind of polymer gel electrolyte based on poly(acrylic acid)-poly(ethylene glycol) (PAA-PEG) hybrid was synthesized. The factor of molecular weight of PEG in the hybrid plays an important role in determining the liquid electrolyte absorbency of the hybrid and ionic conductivity of the polymer gel electrolyte, sequentially affects the photovoltaic performance of quasi-solid-state dye-sensitized solar cells. Using the hybrid with PEG molecular weight of 20,000, a polymer gel electrolyte with liquid electrolyte absorbency of 6.9 g g⁻¹ and ionic conductivity of 5.35 mS cm⁻¹ was obtained. Based on the polymer gel electrolyte, a quasi-solid-state dye-sensitized solar cell with conversion efficiency of 5.25% was achieved under irradiation of AM 1.5, 100 mW cm⁻².