Synthesis and properties of unsaturated polyoxyethylene and its graft copolymers with styrene

The unsaturated polyoxyethylene (PEO) was synthesized by copolymerization of ethylene oxide with allyl glycidyl ether in toluene using bimetallic-oxo-alkoxide as a catalyst. The effects of polymerization conditions on conversion and intrinsic viscosity of the copolymer were studied. The unsaturated copolymer was characterized with infrared spectra, ¹H NMR, and wide-angle X-ray diffraction. The relationship between crystallinity of the copolymers and conductivity of their LiClO₄ complexes were investigated. The copolymer with ∼ 65 wt % PEO content exhibits a room temperature conductivity of 1 × 10⁻⁴ S cm⁻¹ at a molar ratio of EO/Li = 20. The unsaturated PEO was graft-copolymerized with styrene using 2,2′-azobis(isobutyronitrile) as initiator in toluene, with grafting efficiency ∼ 50%. The purified graft copolymer was characterized with infrared spectra, ¹H NMR, and wide-angle X-ray diffraction, and was shown to have good emulsifying properties and a phase-transfer catalytic property. LiClO₄ complex of the graft copolymer with 70 wt % PEO content exhibits a room temperature conductivity approaching 1 × 10⁻⁴ S cm⁻¹ at molar ratio of EO/Li = 20/1. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 70: 2417–2425, 1998     

Preparation and ionic conductivity of solid polymer electrolyte based on polyacrylonitrile‐polyethylene oxide

The transparent and flexible solid polymer electrolytes (SPEs) were fabricated from polyacrylonitrile‐polyethylene oxide (PAN‐PEO) copolymer which was synthesized by methacrylate‐headed PEO macromonomer and acrylonitrile. The formation of copolymer is confirmed by Fourier‐transform infrared spectroscopy (FTIR) measurements. The ionic conductivity was measured by alternating current (AC) impedance spectroscopy. Ionic conductivity of PAN‐PEO‐LiClO₄ complexes was investigated with various salt concentration, temperatures and molecular weight of PEO (Mn). And the maximum ionic conductivity at room temperature was measured to be 3.54 × 10^?4 S/cm with an [Li⁺]/[EO] mole ratio of about 0.1. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 461–464, 2006     

Ionic conductivity in polyethylene-b-poly(ethylene oxide)/lithium perchlorate solid polymer electrolytes

The ionic conductivity and phase arrangement of solid polymeric electrolytes based on the block copolymer polyethylene-b-poly(ethylene oxide) (PE-b-PEO) and LiClO₄ have been investigated. One set of electrolytes was prepared from copolymers with 75% of PEO units and another set was based on a blend of copolymer with 50% PEO units and homopolymers. The differential scanning calorimetry (DSC) results, for electrolytes based on the copolymer with 75% of PEO units, were dominated by the PEO phase. The PEO block crystallinity dropped and the glass transition increased with salt addition due to the coordination of the cation by PEO oxygen. The conductivity for copolymers 75% PEO-based electrolyte with 15 wt% of salt was higher than 10⁻⁵ S/cm at room temperature and reached to 10⁻³ S/cm at 100 °C on a heating measurement. The blend of PE-b-PEO (50% PEO)/PEO/PE showed a complex thermal behavior with decoupled melting of the blocks and the homopolymers. Upon salt addition the endotherms associated with PEO domains disappeared and the PE crystals remained untouched. The conductivity results were limited at 100 °C to values close to 10⁻⁴ S/cm and at room temperature values close to 3 × 10⁻⁶ S/cm were obtained for the 15 wt% salt electrolyte. Raman study showed that the ionic association of the highly concentrated blend electrolytes at room temperature is not significant. Therefore, the lower values of conductivity in the case of the blend with 50% PEO can be assigned to the higher content of PE domains leading to a morphology with lower connectivity for ionic conduction both in the crystalline and melted state of the PE domains.     

Microphase separated structures in the solid and molten states of double-crystal graft copolymers of polyethylene and poly(ethylene oxide)

Transitions from one microphase separated structure in the solid state to a different one in the molten state in polyethylene-graft-poly(ethylene oxide) copolymers, PE-g-PEO, were investigated by variable temperature X-ray scattering measurements and thermal analyses. Small-angle X-ray scattering patterns from polymers with PEO grafts with 25, 50 and 100 ethylene oxide (EO) units show that the polymer passes through three distinct structures at ～10 nm length scales with increase in temperature (T): lamellar structures of PE and PEO at T < T_m^PEO, PE lamellae surrounded by molten PEO at T_m^PEO < T < T_m^PE, and microphase separated structures at T > T_m^PE when both PE and PEO are molten (T_m refers to the melting temperature). These phase transformations also occur during cooling but with hysteresis. Crystalline phases of PEO side chains and PE main chains could be identified in the wide-angle X-ray diffraction profiles indicating that the PE backbone and PEO grafts crystallize into separate domains, especially with longer grafted chains (50 and 100 units). At EO segment lengths > 50, PEO shows the expected increase in melting and crystallization temperatures with the increase in the grafted chain length. PE does not affect T_m^PEO but does decrease the onset of crystallization upon cooling. PEO grafts result in fractionation of PE, decrease the melting point of PE and increase the undercooling for the onset of crystallization of PE.     

Solid polymer electrolytes based on nanocomposites of ethylene oxide–epichlorohydrin copolymers and cellulose whiskers

With the aim of developing ion‐conducting solid polymer electrolytes that combine high ionic conductivity with good mechanical properties, we prepared and investigated nanocomposites of LiClO₄‐doped ethylene oxide‐epichlorohydrin (EO‐EPI) copolymers and nanoscale cellulose whiskers derived from tunicates. We show that homogeneous nanocomposite films based on EO‐EPI copolymers, LiClO₄, and tunicate whiskers can be produced by solution‐casting THF/water mixtures comprising these components and subsequent compression‐molding. The Young's moduli of the nanocomposites thus produced are increased by a factor of up to >50, when compared to the copolymers, whereas the electrical conductivities experience only comparably small reductions upon introduction of the whiskers. The nanocomposite with the best combination of conductivity (1.6 × 10^?4 S/cm at room temperature and a relative humidity of 75%) and Young's modulus (7 MPa) was obtained with a copolymer having an EO‐EPI ratio of 84 : 16, a whisker content of 10% w/w, and a LiClO₄ concentration of 5.8% w/w. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 2883–2888, 2004     

Synthesis,characterization, and properties of amphiphilic poly(ethyl acrylate) with uniform polyoxyethylene grafts

Amphiphilic copolymers of ethyl acrylate (EA) with uniform polyoxyethylene (PEO) grafts were synthesized by copolymerization of EA with methacrylate terminated PEO macromer in benzene using azobisisobutyronitrile as the initiator. The effects of the molecular weight of the macromers, the charging weight ratio of the macromer to EA, the total monomer concentration, and the amount of initiator on the grafting efficiency (GE) were reported as was the molecular weight of the copolymers. The highest GE reached to above 90% and the molecular weight of the copolymers varied from (5–15) × 10⁴. The reactivity ratio of EA with the macromer was determined to be 0.83. The graft copolymers were purified with extractions and the purified products were characterized with IR, ¹H‐NMR, gel permeation chromatography, differential scanning calorimetry, and membrane osmometry. The average grafting number of the copolymer varied from 2 to 11. The glass‐transition temperature of the poly(EA) in the copolymer was increased because of the partial compatibility of the two components. The crystalline property, emulsifying property, and dilute solution viscosity of the graft copolymers, as well as ionic conductivity of their complexes with alkali metal salts, were studied. The emulsifying volume decreased with the increasing molecular weight of the PEO grafts. The addition of NaOH to the emulsion affected the emulsifying volume only slightly, whereas the addition of HCl changed the oil in water type emulsion into a water in oil type. The conductivity of the LiClO₄ complex of the copolymer with an oxyethylene/Li ratio of 20 reached 3.7 × 10^?5 S/cm at 27°C. The lower the crystallinity of the complex, the higher was the conductivity. The dilute solution viscosity showed the existence of intramolecular microphase separation. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 903–912, 2001     

Synthesis of biocompatible tadpole-shaped copolymer with one poly(ethylene oxide) (PEO) ring and two poly(ɛ-caprolactone) (PCL) tails by combination of glaser coupling with ring-opening polymerization

The biocompatible tadpole-shaped copolymers [cyclic-poly(ethylene oxide) (PEO)]-b-[linear poly(?-caprolactone) (PCL)]₂ [(c-PEO)-b-PCL₂] with one PEO ring and two PCL tails were synthesized by combination of glaser coupling with ring-opening polymerization (ROP). First, a linear PEO precursor with two alkyne groups at the chain terminal and two hydroxyl groups at the chain middle was prepared by ROP of EO monomer and the following transformation of functional groups. Then, cyclic PEO with two hydroxyl groups at the same site was obtained by the “Glaser” cyclization. Finally, the hydroxyl groups on cyclic PEO directly initiated the ROP of ?-CL monomer to produce the target copolymers (c-PEO)-b-PCL₂. The target copolymers and intermediates were all well characterized by GPC, MALDI-TOF MS, ¹H NMR and FT-IR.     

Phase behavior of LiClO4-doped poly(ε-caprolactone)-b-poly(ethylene oxide) hybrids in the presence of competitive interactions

The phase behavior of a series of LiClO₄-doped poly(ε-caprolactone)-b-poly(ethylene oxide) (PCL-b-PEO) was studied as a function of PEO volume fraction (f_PEO), doping ratio (r) and temperature (T). It is found that the morphology of the hybrids changes from disordered structure (DIS) to hexagonally packed cylindrical (HEX) structure and then to lamellar (LAM) structure as the volume fraction of the PEO/salt phase (f_PEO/salt) increases at f_PEO/salt < 0.5. Order–order transitions are observed upon heating some hybrids. An approximate phase diagram of the PCL-b-PEO/LiClO₄ hybrids with f_PEO/salt < 0.5 was constructed in terms of f_PEO/salt and the segregation strength (χ_effN). As compared with the phase diagram of the weakly segregated diblock copolymers, the phase diagram of the hybrids has two features: the boundaries of the LAM and HEX structures shifts to lower f_PEO/salt and body-centered cubic spherical (BCC) structure is not observed for the samples studied. This can be attributed to the weaker ability of the salt inducing microphase separation at low f_PEO and the conformational change of the PEO block induced by the salt. Some unexpected phase behaviors were observed for the hybrids with f_PEO/salt > 0.5, including the hexagonally perforated layers (HPL) to LAM transition upon heating the same hybrid and HEX to gyroid (GYR) transition with the increase of doping ratio at the same temperature. These unexpected phase behaviors are qualitatively interpreted based on the competitive association of the PCL block with Li⁺ ions at elevated temperatures and higher doping ratios, which leads to re-distribution of the Li⁺ ions in different phases and the inconsistency between the calculated f_PEO/salt and the real volume fraction of the PEO/salt phase.     

Some properties of organosoluble poly(2,5-didodecyloxy-p-phenylenevinylene) and its blends with poly(oxyethylene)

An organosoluble precursor of poly(2,5-didodecyloxy-p-phenylenevinylene) (PDDOPV) with high molecular weight was synthesized via the chlorine precursor route and characterized by IR and UV-Vis spectra, GPC, DSC, and elemental analysis. Factors effecting the thermal elimination reaction were studied. The solubility, absorption spectra and photoluminescence spectra of PDDOPV were also investigated. The conductivity of PDDOPV doped with different dopants (I₂, Br₂, FeCl₃ and H₂SO₄) and the I₂-doped conductivity of PDDOPV/PEO (polyoxyethylene) blends and PDDOPV/PEO/LiClO₄ blends were compared. The results showed that a synergistic mixed conductivity existed in the I₂-doped PDDOPV/PEO/LiClO₄ blend.     

Synthesis of high molecular weight polyoxyethylene with a quaternary catalyst and study of its conductive blends with poly(2‐vinyl pyridine)

High molecular weight polyoxyethylene (PEO) was synthesized by using a quaternary catalyst composed of triisobutyl aluminum, phosphoric acid, water, and N,N‐dimethylaniline (DMA). Optimum synthesis conditions and some properties of the product were studied. This catalyst showed high activity and the molecular weight of the polyoxyethylene obtained can approach one million. The activity of polymerization mainly depends upon the composition of catalyst. The optimum composition is as follows: i‐Bu₃Al:H₃PO₄:H₂O:DMA = 1 : 0.17 : 0.17 : 0.10–0.15 (molar ratio).The active centers of the catalyst was thus proposed. The high molecular weight PEO synthesized by this catalyst was blended with poly(2‐vinyl pyridine) (PVP) and then doped with LiClO₄ and TCNQ to obtain a conductive elastomeric material. Ionic, electronic, and mixed (ionic–electronic) conductivities of blends were investigated. At a Li/EO molar ratio of 0.1 and a TCNQ/VP molar ratio of 0.5, the mixed conductivity of the blend of PEO/PVP/LiCIO₄/TCNQ is higher than the sum of ionic conductivity of PEO/PVP/LiCIO₄ and electronic conductivity of PEO/PVP/TCNQ, when the weight ratio of PEO to PVP is 6/4 or 5/5. It can reach 4 × 10^?6 S/cm at room temperature. Differential scanning calorimetry, thermal gravimetric analysis, and the appearance of the blend showed that both TCNQ and LiClO₄ can complex with PEO and PVP, thus enhancing the compatibility between PEO and PVP. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

A novel CuI-based iodine-free gel electrolyte for dye-sensitized solar cells

A novel CuI-based iodine-free gel electrolyte using polyethylene oxide (PEO, MW = 100,000) as plasticizer and lithium perchlorate (LiClO₄) as salt additive was developed for dye-sensitized solar cells (DSSCs). Such CuI-based gel electrolyte can avoid the problems caused by liquid iodine electrolyte and has relative high conductivity and stability. The effects of PEO and LiClO₄ concentrations on the viscosity and ionic conductivity of the mentioned iodine-free electrolyte, as well as the performance of the corresponding quasi solid-state DSSCs were investigated comparatively. Experimental results indicate that the performance of DSSCs can be dramatically improved by adding LiClO₄ and PEO, and there are interactions (Li⁺–O coordination) between LiClO₄ and PEO, these Li⁺–O coordination interactions have important influence on the structure, morphology and ionic conductivity of the present CuI-based electrolyte. Addition of PEO into the electrolyte can inhibit the rapid crystal growth of CuI, and enhance the ion and hole transportation property owing to its long helix chain structure. The optimal efficiency (2.81%) was obtained for the quasi solid-state DSSC fabricated with CuI-based electrolyte containing 3 wt% LiClO₄ and 20 wt% PEO under AM 1.5 G (1 sun) light illumination, with a 116.2% improvement in the efficiency compared with the cell without addition of LiClO₄, indicating the promising application in solar cells of the present CuI-based iodine-free electrolyte.     

Synthesis and properties of PS-PEO core-shell amphiphilic dendrigrafts

Water-soluble amphiphilic dendrigrafts constituted of a hydrophobic polystyrene core and a hydrophilic poly(ethylene oxide) shell have been prepared via a ‘grafting onto’ procedure from polystyrene dendrigraft precursors. The introduction of the surrounding hydrophilic shell was achieved through cyclic trans-acetalization between ω-acetal functionalized branches of the polystyrene precursor and PEO grafts bearing a α-bis(hydroxymethyl) chain end (A₂-PEO). Yields of grafting are strongly affected by the increase of the degree of polymerization of the reactive PEO grafts (respectively, 100, 87, and 38% with A₂-PEO20, A₂-PEO100 and A₂-PEO150). However, paradoxically, only the use of A₂-PEO100 or A₂-PEO150 as reactive grafts affords water-soluble dendrigrafts due to higher PEO weight content (respectively, 41 and 36%). The dimensions and the shape of the PS_core-PEO_shell polymers were investigated in solution (THF and water) by dynamic light scattering and in the dry state by TEM and AFM.     

Influence of LiClO4 on the thermal,mechanical, and morphological properties of P(DMS‐co‐EO)/ P(EPI‐co‐EO) blends

The UV‐vis absorption, thermal analysis, ionic conductivity, mechanical properties, and morphology of a blend of poly(dimethylsiloxane‐co‐ethylene oxide) [P(DMS‐co‐EO)] and poly(epichlorohydrin‐co‐ethylene oxide) [P(EPI‐co‐EO)] (P(DMS‐co‐EO)/P(EPI‐co‐EO) ratio of 15/85 wt %) with different concentrations of LiClO₄ were studied. The maximum ionic conductivity (σ = 1.2 × 10^?4 S cm^?1) for the blend was obtained in the presence of 6% wt LiClO₄. The crystalline phase of the blend disappeared with increasing salt concentration, whereas the glass transition temperature (T_g) progressively increased. UV‐vis absorption spectra for the blends with LiClO₄ showed a transparent polymer electrolyte in the visible region. The addition of lithium salt decreased the tensile strength and elongation at break and increased Young's modulus of the blends. Scanning electron microscopy showed separation of the phases between P(DMS‐co‐EO) and P(EPI‐co‐EO), and the presence of LiClO₄ made the blends more susceptible to cracking. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 1230–1235, 2004     

A polymeric solid electrolyte based on a binary blend of poly(ethylene oxide), poly(methyl vinyl ether-maleic acid) and LiClO4

A new polymeric solid electrolyte based on a PEO/PMVE-MAc blend, complexed with LiClO₄, was obtained and characterized by differential scanning calorimetry (DSC), Fourier transform infrared spectroscopy (FTIR), polarized light optical microscopy, electrochemical impedance and cyclic voltammetry. DSC traces indicated miscibility for all the PSE samples. Crystallinity was suppressed for samples with LiClO₄ concentrations higher than 2.5 wt%. FTIR associated with DSC studies indicated that there is a preferential formation of complexes PEO/Li⁺/PMVE-MAc in all PSE samples studied here. The ionic conductivity of PSE reaches a maximum of about 10⁻⁵ S/cm at ambient temperature and 7.5 wt% LiClO₄. The electrochemical stability window is 4.5 V and associated with the other characteristics, make the PSE studied here suitable for applications in ‘smart-windows’, batteries, sensors, etc.     

Conductivities and some other properties of oxymethylene-linked 2-vinylpyridine-oxyethylene multiblock copolymers

Oxymethylene-linked 2-vinylpyridine-oxyethylene (2VP-EO) mulitblock copolymers doped with LiClO₄ or/and tetracyanoquinodimethane (TCNQ) showed ionic electronic and mixed (ionic-electronic) conductivity. Effects of the poly(oxyethylene) content and of the molar ratios of EO/Li and TCNQ/2VP on the conductivities of the complexes were studied. The optimum molar ratios of EO/Li and TCNQ/2VP were 10 and 1.0, respectively. The copolymers emulsified benzene/water systems and exhibited good phase-transfer catalysis properties in the Williamson reaction of solid potassium phenolate with n-butyl bromide. After neutralization with HCI solution, the copolymers showed polyelectrolyte solution properties.     

Polymer solid electrolyte from amorphous poly[epichlorohydrin‐co‐(ethylene oxide)]/lithium perchlorate complex

High molecular mass copolymers (P(EH/EO)s) were synthesized by coordination anionic polymerization of ethylene oxide (EO) and epichlorohydrin (EH), and P(EH/EO)s were used for the preparation of the ion‐conducting matrix. The copolymers having EO unit contents of less than 63 mol% were amorphous, and subjected to the complexation with lithium perchlorate. The temperature dependence of ionic conductivity of the P(EH/EO)/LiClO₄ complexes was expressed by the Williams–Landel–Ferry equation. Optimal conductivity was observed as a function of salt concentration. This is the result of two contradictory factors: the increase of glass transition temperature (negative for the ionic conductivity) and the increase of carrier number (positive for the ionic conductivity) with increasing lithium perchlorate concentration. The ionic conductivity strongly depended on EO unit contents in the copolymers. The introduction of EO units to poly(epichlorohydrin) main chain increased the ionic conductivity as did the addition of 20 wt% poly(oxyethylene) glycol monomethylether of molecular mass 750. © 2000 Society of Chemical Industry     

Effect of additives in PEO/PAA/PMAA composite solid polymer electrolytes on the ionic conductivity and Li ion battery performance

Polyethylene oxide (PEO) based-solid polymer electrolytes were prepared with low weight polymers bearing carboxylic acid groups added onto the polymer backbone, and the variation of the conductivity and performance of the resulting Li ion battery system was examined. The composite solid polymer electrolytes (CSPEs) were composed of PEO, LiClO_4, PAA (polyacrylic acid), PMAA (polymethacrylic acid), and Al₂O₃. The addition of additives to the PEO matrix enhanced the ionic conductivities of the electrolyte. The composite electrolyte composed of PEO:LiClO₄:PAA/PMAA/Li_0.3 exhibited a low polarization resistance of 881.5 ohms in its impedance spectra, while the PEO:LiClO₄ film showed a high value of 4,592 ohms. The highest ionic conductivity of 9.87 × 10⁻⁴ S cm⁻¹ was attained for the electrolyte composed of PEO:LiClO₄:PAA/PMAA/Li_0.3 at 20 °C. The cyclic voltammogram of Li⁺ recorded for the cell consisting of the PEO:LiClO₄:PAA/PMAA/Li_0.3:Al₂O₃ composite electrolyte exhibited the same diffusion process as that obtained with an ultra-microelectrode. Based on this electrolyte, the applicability of the solid polymer electrolytes to lithium batteries was examined for an Li/SPE/LiNi_0.5Co_0.5O₂ cell.     

Enhanced Ionic Conductivity in Poly(ethylene oxide)/Layered Double Hydroxide Nanocomposite Electrolytes

All solid-state poly(ethylene oxide) (PEO) nanocomposite electrolytes were made containing nanoscale fillers of layered double hydroxides (LDHs). Two kinds of oligo(ethylene oxide) modified LDHs were prepared by template method, and added into PEO/LiClO₄ matrix (with EO/Li molar ratio of 8) to study the effect on the ionic conductivity of PEO/LDH nanocomposite electrolytes. The structures of the modified LDHs were characterized by infrared spectra, thermogravimetric analysis and wide-angle X-ray diffraction. The results show that the oligo(ethylene oxide) with phosphonate anion can be effectively intercalated into the gallery region of LDHs and formed as an organic-inorganic hybrid (PLDH). With enhanced compatibility of LDH sheets by oligo(ethylene oxide) surface modification, the PEO/PLDH nanocomposite exhibits fully exfoliation morphology. The well dispersed LDH layers in PEO/LiClO₄/PLDH nanocomposite electrolytes rendering the formation of amorphous phase, results in an enhancement of ionic conductivity by three orders of magnitude compared to the pure PEO/LiClO₄ polymer electrolyte. This novel nanocomposite electrolytes system with high ionic conductivity will be benefited to fabricate the thin-film type of Li-polymer secondary battery. This revised version was published online in July 2006 with corrections to the Cover Date.     

Effects of lithium perchlorate on poly(ethylene oxide) spherulite morphology and spherulite growth kinetics

Effects of lithium perchlorate (LiClO₄) on the crystallization behaviors of poly(ethylene oxide) (PEO) were investigated by differential scanning calorimetry (DSC), Fourier transform infrared spectroscopy (FTIR), and polarized optical microscopy (POM) in PEO/LiClO₄ system. DSC results indicate that there are nucleation effects of LiClO₄ on the crystallization of PEO. But, on the other hand, the coordination of lithium ion with the oxygen ether atoms of PEO can obviously reduce the crystallinity and spherulite growth rate of PEO. This contrary effect of LiClO₄ on the crystallization of PEO in PEO/LiClO₄ complexes system was analyzed and discussed in detail. The Laurizen–Hoffman theory was used to describe the Li‐coordinated crystallization kinetics of PEO spherulite. It showed that the nucleation constant (K_g) and folding surface free energy (σ_e) decreased with increasing LiClO₄ contents, and the energy necessary for the transport of segments across the liquid–solid interface (ΔE) increased on increasing the contents of LiClO₄. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Thermal,thermomechanical, and electrochemical characterization of the organic–inorganic hybrids poly(ethylene oxide) (PEO)–silica and PEO–silica–LiClO4

To study the effect of the silica content on the properties of the salt‐free and salt‐added hybrids based on poly(ethylene oxide) (PEO) and silica, two series of hybrids, PEO–silica and PEO–silica–LiClO₄ (O:Li, 9:1) hybrids were prepared via the in situ acid‐catalyzed sol–gel reactions of the precursors [i.e., PEO functionalized with triethoxysilane and tetraethyl orthosilicate (TEOS)]. The morphology of the hybrids was examined by scanning electron microscopy (SEM) of the fracture surfaces of the hybrid. The results indicated that the discontinuity develops with increasing the weight percent of silica in both hybrids. The differential scanning calorimetric (DSC) analysis indicated that effects of silica content on the glass transition temperatures (T_g) of the PEO phase were different in salt‐free and salt‐added hybrids. The T_g of PEO phase increased with increasing weight percent of silica in salt‐free hybrids, whereas the curve of T_g of PEO phase and silica content had a maximum at 35 wt % of silica content in salt‐added hybrids. For both salt‐free and salt‐added hybrids, peaks of the loss tangent, determined by dynamic mechanical analysis (DMA) were gradually broadened and lowered with increasing weight percent of silica. The storage modulus, E′, in the region above T_g increases with increasing silica content for both PEO–silica and PEO–silica–LiClO₄ hybrids. In the conductivity and composition curves for PEO–silica–LiClO₄ hybrids, the conductivity shows a maximum value of 3.7 × 10^?6 S/cm, corresponding to the sample with a 35 wt % of silica. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 2471–2479, 2001