Semicrystalline PEO Research Articles

Polymer Infiltration into Metal-Organic Frameworks in Mixed-Matrix Membranes Detected in Situ by NMR.

Solid-state NMR has been used to study mixed-matrix membranes (MMMs) prepared with a metal-organic framework (MOF, UiO-66) and two different high molecular weight polymers (PEO and PVDF). 13C and 1H NMR data provide overwhelming evidence that most UiO-66 organic linkers are within 1 nm of PEO, which indicates that PEO is homogeneously distributed throughout the MOF. Systematic changes in MOF 13C NMR peak positions and 1H NMR line widths, as well as dramatic reductions in the MOF 1H T1ρ relaxation times, are observed as the PEO content increases, and when the pores have been filled, a further increase in PEO results in the formation of semicrystalline PEO outside the UiO-66 particles. In contrast, similar studies on PVDF MMMs show that the polymer contacts only a small fraction (<20%) of the MOF linkers. Simulations confirm that PEO penetrates into UiO-66 more easily than does PVDF. These studies are among the first to provide experimental insights into MOF-polymer interactions in an MMM.

Highly Branched Poly(ethylene oxide) for Solid Electrolytes

Commercial Li ion batteries use liquid electrolytes between the electrodes to obtain good Li ion conductivity and thus good energy density. However, the liquids are highly flammable, which presents a great challenge in designing large scale batteries. Solid polymer electrolytes (SPEs) based on poly(ethylene oxide) (PEO) have been widely explored as an alternative of all-solid-state Li ion batteries. However, their wide adoption is prohibited due to their low conductivity at room temperatures (lower than 10-5 S cm-1), presumably because PEO is semicrystalline and crystals may not be available for ion conductivity. The goal of this study is to design and prepare series of polymers containing amorphous PEO with high free volume, achieving higher Li ion conductivity than the semi-crystalline PEO. Specifically, polymers were prepared using UV photopolymerization from poly(ethylene glycol) diacrylate (PEGDA) and poly(ethylene glycol) methyl ether acrylate (PEGMEA). The addition of PEGMEA in PEGDA increases the free volume and polymer chain flexibility. Polymer electrolytes based on PEGDA-co-PEGMEA and lithium perchlorate (LiClO4) have been prepared and characterized using DSC, WAXD and electrochemical impedance spectroscopy (EIS). At PEGMEA content of 90% in the polymer with an O:Li ratio of 14, the conductivity approaches the current industrial targeted value (10-5 S/cm), which is two orders of magnitude higher than that of pure PEO. This presentation will also compare the results with those based on the PEO-containing materials using the Vogel-Fulcher-Tammann (VFT) equation. The implication of the VFT model on the potential of PEO-based SPEs in terms of ionic conductivity will be elucidated.

Jeffamine® based polymers as highly conductive polymer electrolytes and cathode binder materials for battery application

Abstract We report a simple synthesis route towards a new type of comb polymer material based on polyether amines oligomer side chains (i.e., Jeffamine® compounds) and a poly(ethylene-alt-maleic anhydride) backbone. Reaction proceeds by imide ring formation through the NH2 group allowing for attachment of side chains. By taking advantage of the high configurational freedoms and flexibility of propylene oxide/ethylene oxide units (PO/EO) in Jeffamine® compounds, novel polymer matrices were obtained with good elastomeric properties. Fully amorphous solid polymer electrolytes (SPEs) based on lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) and Jeffamine®-based polymer matrices show low glass transition temperatures around −40 °C, high ionic conductivities and good electrochemical stabilities. The ionic conductivities of Jeffamine-based SPEs (5.3 × 10−4 S cm−1 at 70 °C and 4.5 × 10−5 S cm−1 at room temperature) are higher than those of the conventional SPEs comprising of LiTFSI and linear poly(ethylene oxide) (PEO), due to the amorphous nature and the high concentration of mobile end-groups of the Jeffamine-based polymer matrices rather than the semi-crystalline PEO The feasibility of Jeffamine-based compounds in lithium metal batteries is further demonstrated by the implementation of Jeffamine®-based polymer as a binder for cathode materials, and the stable cycling of Li|SPE|LiFePO4 and Li|SPE|S cells using Jeffamine-based SPEs.

Poly(ethylene oxide) (PEO) – Poly(vinyl pyrrolidone) (PVP) blend polymer based solid electrolyte membranes for developing solid state magnesium ion cells

The present work is an attempt to find the suitability of Poly(ethylene oxide) (PEO) - Poly(vinyl pyrrolidone) (PVP) blend polymer based solid electrolyte membranes for applications in all solid state magnesium ion cells. On solvating the PEO-PVP blend with different concentrations of Mg(NO3)2 salt, the PEO-PVP-Mg(NO3)2 complex electrolyte, termed as the solid polymer electrolyte (SPE) is formed. Flexible free-standing membranes of this SPE of thickness around 100µm are obtained by solution casting technique. The amorphous nature of the semi-crystalline polymer PEO is enhanced by the addition of the Mg salt, as revealed by XRD, FE-SEM and Raman studies. The ionic conductivity evaluated for this SPE membrane is four orders higher than that of pure PEO and close to that of liquid electrolytes used in Mg ion cells. The highest Mg ion conductivity observed for the SPE membrane, in the present work is 5.8×10−4Scm−1 at room temperature and is higher than previously reported ionic conductivity for Mg salt complexed solid polymer electrolytes. The Cyclic Voltammetry (CV) curve of the SPE with stainless steel (SS) blocking electrodes shows wide electrochemical window of 4V. The Mg ion cells assembled using this SPE as the electrolyte, without the need for any additional separator show an open circuit voltage around 1.46V and are electrochemically active.

Cascade synthesis of a gold nanoparticle-network polymer composite.

The multi-step, cascade synthesis of a self-supporting, hierarchically-structured gold nanoparticle hydrogel composite is described. The composite is spontaneously prepared from a non-covalent, lamellar lyotropic mesophase composed of amphiphiles that support the reactive constituents, a mixture of hydroxyl- and acrylate-end-derivatized PEO117-PPO47-PEO117 and [AuCl4](-). The reaction sequence begins with the auto-reduction of aqueous [AuCl4](-) by PEO117-PPO47-PEO117 which leads to both the production of Au NPs and the free radical initiated polymerization and crosslinking of the acrylate end-derivatized PEO117-PPO47-PEO117 to yield a network polymer. Optical spectroscopy and TEM monitored the reduction of [AuCl4](-), formation of large aggregated Au NPs and oxidative etching into a final state of dispersed, spherical Au NPs. ATR/FT-IR spectroscopy and thermal analysis confirms acrylate crosslinking to yield the polymer network. X-ray scattering (SAXS and WAXS) monitored the evolution of the multi-lamellar structured mesophase and revealed the presence of semi-crystalline PEO confined within the water layers. The hydrogel could be reversibly swollen without loss of the well-entrained Au NPs with full recovery of composite structure. Optical spectroscopy shows a notable red shift (Δλ ∼ 45 nm) in the surface plasmon resonance between swollen and contracted states, demonstrating solvent-mediated modulation of the internal NP packing arrangement.

Synthesis of Semicrystalline/Fluorinated Side-Chain Crystalline Block Copolymers and Their Bulk and Thin Film Nanoordering

Semicrystalline/fluorinated side-chain crystalline block copolymers, dinonylphenyl end-capped poly(ethylene glycol)-block-poly(fluorinated methyl methacrylate) (DNPEPEO-b-PFMAs), were synthesized by ATRP of 3,3,4,4,5,5,6,6,7,7,8,8,9,9,10,10,10-heptadecafluorodecyl methacrylate using a surfactant poly(ethylene glycol) dinonylphenyl ether as precursor. Bulk and thin film morphologies in the block copolymers of DNPEPEO-b-PFMAs were investigated by DSC, WAXS, SAXS, TEM, AFM, and GISAXS. The block copolymers show microphase separated and ordered structures. In the bulk, a cylindrical morphology with PEO cylinders confined in PFMA matrix was confirmed by SAXS and TEM. WAXS studied on the copolymers bulk revealed semicrystalline PEO cylinders and PFMA matrix with the fluorinated side chain organized in bilayers. In thin films of DNPEPEO-b-PFMAs on PDMS modified silicon substrates, well ordered hexagonally packed arrays with PEO cylindrical microdomains normal to the substrate were observed. This fluorinated bloc...

Study of gas permeabilities through polystyrene-block-poly(ethylene oxide) copolymers

Pure gas permeability through a polystyrene-b-poly(ethylene oxide) block copolymer (SEO) membrane was measured between 20 and 80°C. The membrane comprised alternating polystyrene (PS) and poly(ethylene oxide) (PEO) lamellae; the average center-to-center distance between adjacent PS lamellae was 96nm. Among the different gases considered, carbon dioxide showed the highest permeability, with values up to 200Barrer, followed by helium, oxygen, methane and nitrogen. Gas permeability appeared to be controlled by condensability of the gas, molecular size, and molecular interactions. The melting of poly(ethylene oxide) (PEO) domains, which occurred between 40 and 60°C, caused deviation from Arrhenius behavior. A simple model that accounts for transport through a composite composed of semi-crystalline PEO lamellae and amorphous PS lamellae was developed. Model results and experimental data agreed fairly well considering the simplicity of the approach. The model can readily be used to predict pure gas permeabilities of SEO copolymers with arbitrary morphologies and crystallinity. The crystalline PEO volume fractions inferred from the permeation data are within 15% of those determined by differential scanning calorimetry.

Time-resolved conformational analysis of poly(ethylene oxide) during the hydrogelling process

We investigated a drastic conformation change in a poly(ethylene oxide) (PEO) chain during the hydrogelation process using infrared (IR) spectroscopy and quantum chemical calculations (QCCs). Time-resolved in situ IR spectra of the hydrogelling process of a semi-crystalline PEO solid were measured using a flow-through cell. It was found from the time-resolved IR study that gauche conformations around the C–C bonds in the crystalline phase PEO chain maintain their conformations even after hydrogelation, while at least half of the trans conformations around the C–O bonds change into gauche conformations upon hydrogelling. With regard to the phenomena of these conformation changes after contacting water, the destruction and hydrogelation of the crystalline phase around the C–C bonds of the hydrophobic moiety occur prior to changes around the C–O bonds of the hydrophilic moiety. In addition, our QCC confirmed that the stable hydration structure of bridging water, wherein the two hydroxyl groups in a water molecule donate hydrogen bonds to every other ether oxygen atoms in the PEO chain.

Thermal degradation of PEO on SiO 2 nanoparticles as a function of SiO 2 silanol density, hydrophobicity and size

The degradation behavior of semicrystalline PEO on silica (SiO 2) nanoparticles as a function of silanol density, hydrophobicity and nanoparticle size was investigated under N 2 purge by derivative thermogravimetric analysis (dTGA) for adsorption amounts at or below plateau adsorption. The PEO was adsorbed onto colloidal (Stöber) onto 100 nm colloidal that had been heat-treated to vary the silanol density or hydrophobically modified, (CH 3) 3–SiO 2, and onto 15, 40 and 100 nm SiO 2 made by a water-glass process. Either one or two degradation peaks, T d , were observed for the adsorbed PEO, one at ∼180–210 °C and one at ∼250–300 °C. The degradation peak at 180–210 °C appeared either at high adsorption amounts for the 100 nm SiO 2, on the 15 nm SiO 2, and on hydrophobically modified SiO 2, where PEO not directly hydrogen-bonded with SiOH was expected. The degradation peak at 250–300 °C correlated with SiOH density of the SiO 2, and thus SiOH/C O contacts, and the peak position increased with increase in SiOH density. With decreasing adsorption amount for the 100 nm SiO 2, the 180–210 °C peak decreased with respect to the 250–300 °C peak. Thus, the freer PEO segments appeared to degrade at lower temperatures than the H-bonded segments. However, both T d s were well below those observed for neat PEO, which occurs at ca 388 °C. This may arise since PEO is oxidatively unstable, and the volatile degradation products of the relatively small number of PEO chains on the high surface area SiO 2 are removed quickly, resulting in more rapid degradation.

Structure and properties of new polyester elastomers composed of poly(trimethylene terephthalate) and poly(ethylene oxide)

Series of PTT- b-PEO copolymers with different composition of rigid PTT and PEO flexible segments were synthesized from dimethyl terephthalate (DMT), 1,3-propanediol (PDO), poly(ethylene glycol) (PEG, M n = 1000 g/mol) in a two stage process involving transesterification and polycondensation in the melt. The weight fraction of flexible segments was varied between 20 and 70 wt%. The molecular structure of synthesized copolymers was confirmed by 1H NMR and 13C NMR spectroscopy. The superstructure of these polymers was characterized by DSC, DMTA, WAXS and SAXS measurements. It was observed that domains of three types can exist in PTT- b-PEOT copolymers: semi-crystalline PTT, amorphous PEO rich phase (amorphous PEO/PTT blended phase) and semi-crystalline PEO phase. Semi-crystalline PEO phase was observed only at temperature below 0 °C for sample containing the highest concentration of PEO segment. The phase structure, thermal and mechanical properties are effected by copolymer composition. The copolymers containing 30÷70 wt% of PEO segment posses good thermoplastic elastomers properties with high thermal stability. Hardness and tensile strength rise with increase of PTT content in copolymers.

Structure and Mechanical Properties of an O70 (Fddd) Network-Forming Pentablock Terpolymer

Symmetric poly(ethylene oxide-b-styrene-b-isoprene-b-styrene-b-ethylene oxide) (OSISO) pentablock terpolymers with narrow molecular weight distributions in all blocks were synthesized by anionic polymerization. These OSISO pentablock terpolymers have a common poly(styrene-b-isoprene-b-styrene) (SIS) core containing equal volume fractions of polyisoprene and polystyrene but having different lengths of terminal poly(ethylene oxide) (PEO) chains. Small-angle X-ray scattering, transmission electron microscopy, dynamic mechanical spectroscopy, and differential scanning calorimetry were used to identify two-domain lamellae, O70 (the orthorhombic Fddd network), and three-domain lamellae (LAM3) in the OSISO materials; these morphologies were previously identified in poly(isoprene-b-styrene-b-ethylene oxide) (ISO) triblock terpolymers with comparable compositions. Mechanical tensile testing was employed to probe the consequences of adding different lengths of semicrystalline PEO to the ends of intrinsically tough ...

Neutron scattering investigation of a diluted blend of poly(ethylene oxide) in polyethersulfone

By using quasielastic neutron scattering (QENS) with isotopic labeling we have investigated the component dynamics in a miscible blend of polyethersulfone (PES) and poly(ethylene oxide) (PEO) with 75% content in weight of PES. Due to the large difference in the glass-transition temperatures, T(g)'s, of the two polymers (T(g) (PEO) approximately equal to 220 K, T(g) (PES) approximately equal to 382 K) the dynamic asymmetry in the system dramatically increases when approaching the average T(g) of the blend, <T(g)(blend)>. For the fast (PEO) component, this leads to a behavior which hints a crossover from typical glass-forming liquidlike dynamics at high temperatures to confined dynamics close to <T(g)(blend)> induced by the freezing of the segmental motions of the slow PES. The features of the confined PEO motion observed by QENS are similar to those of the secondary gamma-relaxation detected for pure (semicrystalline) PEO. A neutron diffraction study of the short-range order of the homopolymers and the blend suggests that this coincidence could be due to similarities in the intermolecular packing of PEO and PES polymers.

The influence of phase segregation on properties of semicrystalline PEO:LiTFSI electrolytes

Polymer electrolytes composed of poly(ethylene oxide) and lithium imide salt LiN(CF 3SO 2) 2 were prepared by casting from solution. The electrolytes were characterized by impedance spectroscopy, impedance spectroscopy simultaneous with polarizing microscope observation, X-ray diffraction and DSC. It was found, that the properties of amorphous phase, which remained in the semicrystalline PEO:LiTFSI electrolytes, depend on thermal history of the sample. Phase segregation, occurring when the molar ratio of salt in crystalline lamellae is different from the average molar ratio of electrolyte, was indicated as the mechanism of this effect. Phase segregation affected also the mechanism of crystallization and morphology of the crystalline phase. All these factors were found to influence strongly the ionic conductivity of the electrolyte. Due to shift of the glass transition temperature, at low temperature the conductivity of certain electrolytes was higher when they were in semicrystalline state than the conductivity of electrolytes in amorphous state. For electrolytes with high concentration of salt, additional effects of decoupling of the transport of ions from the motions of polymer matrix were observed.

Crystallization behavior of dry‐brush PEO‐PS block copolymer and PEO homopolymer blend

AbstractThe crystallization behavior of semicrystalline PEO homopolymer/triblock PS‐PEO‐PS copolymer blend system, which exhibited “Dry‐Brush” in the melt. A symmetric polystyrene–poly(ethylene oxide)–polystyrene triblock copolymer was blended with PEO homopolymer (h‐PEO) having the same molecular weight as that of the PEO block in the copolymer. Considering the composition of the blend (Wps ≥ 0.8), PEO spheres were formed in the blend. Because of the dry‐brush phase behavior of this blend, h‐PEO added was localized in the PEO microdomains, which increases the domain size without changing the microdomain morphology. The crystallization of PEO block was confined within the microdomains and the crystallization temperature was about 60°C lower than normal. Self‐seeding tests were performed to clarify the nucleation mechanism of the blend. Because the droplets size varies greatly, multicrystallization peaks were witnessed in the self‐seeding process. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007

Spinodal wrinkling in thin-film poly(ethylene oxide)/polystyrene bilayers

Optical microscopy and atomic force microscopy were used to study a novel roughness-induced wrinkling instability in thin-film bilayers of poly(ethylene oxide) (PEO) and polystyrene (PS). The observed wrinkling morphology is manifested as a periodic undulation at the surface of the samples and occurs when the bilayers are heated above the melting temperature of the semi crystalline PEO (T(m) = 63 Celsius) layer. During the wrinkling of the glassy PS capping layers the system selects a characteristic wavelength that has the largest amplitude growth rate. This initial wavelength is shown to increase monotonically with increasing thickness of the PEO layer. We also show that for a given PEO film thickness, the wavelength can be varied independently by changing the thickness of the PS capping layers. A model based upon a simple linear stability analysis was developed to analyse the data collected for the PS and PEO film thickness dependences of the fastest growing wavelength in the system. The predictions of this theory are that the strain induced in the PS layer caused by changes in the area of the PEO/PS interface during the melting of the PEO are sufficient to drive the wrinkling instability. A consideration of the mechanical response of the PEO and PS layers to the deformations caused by wrinkling then allows us to use this simple theory to predict the fastest growing wavelength in the system.

Crystallinity of Hybrid Nanozeolite-Poly(ethylene oxide) Composites

New materials that contain both organic and inorganic components have potentially new chemical and physical properties that can even lie outside those bracketed by their constituents. A series of hybrid polymer-inorganic nanocomposite materials was synthesized using various poly(ethylene oxide), LiCF3SO3, and zeolite mixtures. The series included mixtures of SiO2, PEO-LiX, and PEO-GLYLiX, of varying concentrations (where GLY 1/4 3-glycidoxypropyltrimethoxysi-lane, LiX is lithiated faujasite zeolite, and the Li+ source was LiCF3SO3; for all the LiCF3SO3-containing samples, the PEO oxygen: lithium mole ratio was 12: 1). Their degrees of crystallinity and glass transition temperatures relative to pure semicrystal-line PEO were found to be reduced on the addition of the inorganic components.

Gas solubility, diffusivity and permeability in poly(ethylene oxide)

The effect of pressure on the solubility, diffusivity, and permeability of He, H 2, O 2, N 2, CO 2, CH 4, C 2H 4, C 2H 6, C 3H 6 and C 3H 8 in poly(ethylene oxide) (PEO) is reported at 35 °C. Additionally, the temperature dependence of permeability is reported. The effect of polar ether linkages in PEO on gas transport is illustrated by comparing transport properties in PEO with those in polyethylene (PE). For example, at 35 °C and infinite dilution, semi-crystalline PEO exhibits CO 2 permeability coefficient of 12 Barrers, and CO 2/H 2 and CO 2/N 2 pure gas selectivities of 6.7 and 48, respectively. In contrast, at similar conditions, the permeability of PE to CO 2 is 13 Barrers, but the CO 2/N 2 selectivity is only 13. In addition to good separation properties for quadrupolar–nonpolar gas pairs, PEO also shows interestingly high selectivity for olefins over paraffins, which is ascribed to favorable interaction between the polar ether groups in PEO and olefins. For example, the infinite dilution permeability of PEO to propylene is 3.8 Barrers and pure gas propylene–propane selectivity is 2.7 at 35 °C. At similar conditions, PE exhibits propylene–propane selectivity of only 1.4.

Studies of photooxidative degradation of poly(vinyl chloride)/poly(ethylene oxide) blends

AbstractThe photooxidative degradation of blends (in a full range of compositions) of amorphous poly(vinyl chloride) (PVC) with semicrystalline poly(ethylene oxide) (PEO) in the form of thin films is investigated using absorption spectroscopy (UV–visible and Fourier transform infrared) and atomic force microscopy (AFM). The amount of insoluble gel formed as a result of photocrosslinking is estimated gravimetrically. It is found that the PVC/PEO blendsí susceptibility to photooxidative degradation differs from that pure of the components and depends on the blend composition and morphology. Photoreactions such as degradation and oxidation are accelerated whereas dehydrochlorination is retarded in blends. The photocrosslinking efficiency in PVC/PEO blends is higher than in PVC; moreover, PEO is also involved in this process. AFM images showing the lamellar structure of semicrystalline PEO in the blend lead to the conclusion that the presence of PVC does not disturb the crystallization process of PEO. The changes induced by UV irradiation allow the observation of more of the distinct PEO crystallites. This is probably caused by recrystallization of short, more mobile chains in degraded PEO or by partial removal of the less stable amorphous phase from the film surface. These results confirm previous information on the miscibility of PVC with PEO. The mechanism of the interactions between the components and the blend photodegradation are discussed. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 585–602, 2004

Positron annihilation and differential scanning calorimetry investigations in poly(methylmethacrylate)/low molecular weight poly(ethylene oxide) polymer blends

Positron annihilation lifetime spectroscopy (PALS) and differential scanning calorimetry (DSC) measurements were performed in atactic poly(methylmethacrylate) and low molecular weight poly(ethylene oxide) (PEO) polymer blends, prepared by codissolution in acetonitrile, covering the full range of composition. Results from the two techniques indicate that a window of miscibility is attained at around 20-30 wt % of the semicrystalline PEO.

Conductivities and thermal studies of polymeric electrolytes based on poly(epichlorohydrin)/sodium salts

The halogenated polyether named Hydrin-T® is a terpolymer constituted of epichlorohydrin-ethylene oxide-allyl glycidyl ether. It was studied as a polymeric electrolyte in polymer/NaX systems (X = Br - , I-, SCN - , ClO 4 - and B(C 6 H 5 ) 4 - ). In this work we present an investigation of the ionic conductivity (measured by impedance spectroscopy) and thermal properties (measured by differential scanning calorimetry-DSC, modulated DSC and thermogravimetry) of the polymeric electrolyte as a function of the composition in the range of 5 to 40 m/m (%) of the sodium salt. The solubility of sodium salts in the elastomer terpolymer matrix is comparable to the solubility in the best known matrix of linear semicrystalline PEO. The conductivities of the terpolymer/Nal electrolytes are higher than those of membranes prepared with other salts studied (10 -5 S/cm for the former versus 10 -7 to 10 -6 S/cm for the latter). This system also is the most homogeneous up to 40 m/m (%) and showed the smallest increase of T g values as a function of salt concentration [between -53°C for the pure polymer and -35°C for the 40 m/m (%) of NaI]. Modulated DSC confirmed the homogeneity of the terpolymer/NaI system showing T g transition in a range of only 5°C. A decrease of variation of heat capacity during glass transition with the increase of salt concentration was observed.