PEO Spherulites Research Articles

Structural, morphological, optical, electrical and dielectric features based on nanoceramic Li4Ti5O12 filler reinforced PEO/PVP blend for optoelectronic and energy storage devices

Polymer nanocomposite films had been fabricated by the solution casting process using the organic matrix of polyethylene oxide/polyvinylpyrrolidone (PEO/PVP: 50/50 wt%) blend and various filling levels of lithium titanium oxide nanoparticles (Li4Ti5O12 NPs). The TEM and XRD techniques indicated the phase purity of the cubic Li4Ti5O12 NPs with a crystallite size of about 69 nm. The FTIR spectra revealed that the complexation/miscibility between the PEO/PVP blend components were existed through the formation hydrogen bonding between the main functional groups of these polymers and also the loaded NPs fundamentally behaved as geometrical incarceration for the structure of PEO/PVP matrix, due to the formation of polymer-nanoparticles interactions. The SEM images indicated observable variations in the size of PEO spherulites, formed aggregations and pores of host matrix on 1 wt% Li4Ti5O12 NPs and additional 3 and 5 wt%. The optical features of nanocomposites such as optical energy band gap and refractive index were evaluated through the UV/vis. absorbance spectra, where the redshift for the main absorption edge of the filled films implied that Li4Ti5O12 NPs had been successfully embedded into the PEO/PVP matrix. The maximum refractive index and the lowest optical bandgap energy were obtained for the nanocomposite sample (5 wt%). The AC electrical conductivity σac and the dielectric response of the prepared samples were studied, where the loaded NPs increased the values of σac, dielectric loss, and dielectric constant of the PEO/PVP blend and the dielectric constant of the nanocomposite films decreased with increasing the applied frequency. The electrical modulus formalism (M*) and impedance formalism (Z*) were used to analyze the impedance data. The enhancements in the optical and electrical characteristics make these nanocomposite materials appropriate for many uses such as integral thin film capacitors, flexible nanodielectrics for organoelectronic devices, high power Li-ion batteries, optical band gap tuner and many optoelectronic devices.

Fascinating morphology and crystallization behavior of melt miscible binary blends of crystalline homopolymers depicting nearly simultaneous melting transitions

We report on the interesting crystallization behavior of crystalline/crystalline polymer blends, composed of poly(butylene adipate) (PBA) and poly(ethylene oxide) (PEO), with nearly simultaneous melting and crystallization transitions. The miscibility of the two components ensured that the crystallization, on cooling, occurred from the homogenous phase in the melt. The crystalline morphology and structure was investigated using a combination of DSC, PLOM, WAXD and SAXS measurements. The crystalline structure and morphology of the PEO/PBA blends were found to be governed by a strong competition between the faster crystallization kinetics of PEO and relatively much higher nucleation density of PBA. In the PEO-rich blend, the faster crystallization kinetics of the PEO dominated the crystallization morphology development such that the minority component i.e. PBA was found to get entrapped in the interlamellar and interfibrillar regions of PEO spherulites. Interestingly, the resulting crystallization of PBA, within the confined intraspherultic regions of PEO, favored the formation of β phase crystals even at very high isothermal crystallization temperatures. In the symmetric and PBA-rich blends, the higher nucleation density of PBA had a dominant influence on the crystalline morphology development, especially at high degree of supercooling. This resulted in the formation of a variety of interesting morphologies which included interpenetrating spherulites, PEO templated PBA and PBA templated PEO spherulites. Furthermore, the α crystal phase of PBA was found to be more stable in a large supercooling window plausibly due to the dilution effect of PEO. The present study provide novel insight into the competitive role of crystallization rate and nucleation density on the crystallization behavior of crystalline/crystalline blends, with similar melting points, which has been scarcely studied in the past.

Reducing the Crystallite Size of Spherulites in PEO-Based Polymer Nanocomposites Mediated by Carbon Nanodots and Ag Nanoparticles.

The PEO-based polymer nanocomposites were prepared by solution cast method. Green approaches were used for synthesis of carbon nanodots (CNDs) and silver nanoparticles (Ag NPs). It was found that the crystallite size of spherulites of PEO was greatly scarified upon incorporation of CNDs and Ag NPs. In the present work, in opposition to other studies, broadening of surface plasmon resonance (SPR) peak of metallic Ag NPs in PEO-based polymer composites was observed rather than peak tuning. Various techniques, such as powder X-ray diffraction (XRD), SEM, UV–Vis spectroscopy, and photoluminescence (PL), were used to characterize the structural, morphological, and optical properties of the samples. Increase of amorphous phase for the PEO doped with CND particles was shown from the results of XRD analyses. Upon the addition of suspended Ag NPs to the PEO:CNDs composites, significant change of XRD peak position was seen. A field-emission scanning electron microscope (FESEM) was used to investigate the surface morphology of the samples. In the SEM, a significant change in the crystalline structure was seen. The size of PEO spherulites in the PEO nanocomposite samples became smaller and the percentage of amorphous portion became larger, owing to the distribution of CNDs and Ag NPs. The UV–Vis absorption spectra of the PEO-based polymer were found to improve and shift to higher wavelengths upon incorporation of CNDs and Ag NPs into the PEO matrix. The SPR peak broadening in the UV–Vis spectra was observed in the PEO:CNDs composites due to the Ag NPs. The absorption edge value of PEO was found to shift toward lower photon energy as the CNDs and Ag NPs are introduced. The photoluminescence (PL) spectra were also observed for the PEO:CNDs and PEO:CNDs:Ag samples and found to be more intense in the PEO:CNDs system than in the PEO:CNDs:Ag system. Lastly, the optical band gap of the samples was further studied in detail using of Tauc’s model and optical dielectric loss parameter. The types of electron transition were specified.

Thermal Properties and Morphology of Compatible Poly(ethylene oxide)/Natural Rubber‐graft‐poly(methyl methacrylate) Blends

Free standing films of blends of poly(ethylene oxide) and natural rubber‐graft‐poly(methyl methacrylate) (PEO/NR‐g‐PMMA) with 40 mol% of PMMA‐graft were prepared at different mass compositions using solution casting technique. These blends show immiscibility in the molten state as indicated by two glass transition temperatures (Tg's), which correspond relatively close to the PEO and NR‐backbone components. The assessment of Tg of the PMMA‐graft can not be made under the experimental condition (heating up to 80 °C). It is expected that the Tg of PMMA‐graft is around 100 °C. Upon cooling from the melt, PEO crystallizes and liquid‐solid phase separation takes place. At room temperature, although the blends are immiscible, results show that the amorphous phase of the blends may comprise of mixture of compatible interfacial region of PEO and PMMA‐graft. Differential scanning calorimetry (DSC) analysis was used for the qualitative assessment of the blend compatibility. The compatibility of PEO and PMMA‐graft was evaluated by change in heat capacity (ΔCp) of the glass transition of PEO and NR‐backbone in the blends. Furthermore, the crystallinity (X*) and melting temperature (Tm) of PEO in the blends at higher content of NR‐g‐PMMA are depressed, which support the Tg and ΔCp results. These findings are in agreement with PEO crystalline structure from WAXS analysis and morphological studies where the PEO spherulites show a significant change upon addition of NR‐g‐PMMA in the blends.

Thermal Properties and Morphology of Poly(ethylene oxide)/Poly(n‐butyl methacrylate) Blends

From the thermodynamic point of view, most of the high molar‐mass binary polymer blends are immiscible due to the entropic contribution to the free energy of mixing is relatively small. The miscibility of the systems on the molecular scale can be assessed by the thermal properties such as quantities of glass transition temperature (Tg) and change in heat capacity (ΔCp) of the polymers. For a semi‐crystalline polymer such as poly(ethylene oxide) (PEO), the crystallinity (X*) and the melting temperature (Tm) can also give some hints on the miscibility. Apart from the thermal properties, additional scientific findings such as morphology of the blends are needed as supplementary evidences to support the results. We focus on the PEO as the polymer host, blends with poly(n‐butyl methacrylate) (PnBMA) which were prepared using solution casting technique. Thermal properties of PEO/PnBMA polymer blends were investigated by modulated differential scanning calorimeter (MDSC) on the isothermal crystallized samples at 25 °C. Tg of PEO in the blends do not show significant variation with addition of PnBMA for entire composition range while for Tg of PnBMA in the blends, it is challenging to be estimated under the experimental condition due to the overlapping of the Tg of PnBMA and melting endotherm of PEO. Constancy of quantity Tg of PEO and ΔCp of PEO corresponding to the content of PEO in the blends suggest that PEO and PnBMA are immiscible for entire blend composition. X* and Tm of PEO in the blends show insignificant variation in PEO/PnBMA blends, when PEO as major component. This implies that these blends are immiscible under the experimental conditions as agreed with results of Tg and ΔCp. Spherulitic morphologies of PEO in the blends were studied by polarized optical microscopy (POM). PnBMA phase disperses randomly in PEO matrix when PEO in excess. The absence of significant change for the fibrillar spherulitic structures of PEO spherulites with addition of PnBMA (when PEO is the major component) suggests that immiscibility of PEO and PnBMA. Besides, the crystalline structure of PEO in PEO/PnBMA blends using X‐ray diffraction (XRD) reveals that the crystalline structure of PEO is not disturbed with the addition of PnBMA when PEO is in excess as the two distinct peaks of PEO do not shift as compared to neat PEO. Impedance spectroscopy (IS) studies show that the ionic conductivities (σDC) of the polymer blends at room temperature slightly increase with increasing of PEO with the order of magnitude of 10−11–10−10 S cm−1. This system serves as a potential polymer host as solid polymer electrolytes when added with inorganic salt.

Polyethylene oxide films reinforced by cellulose nanocrystals: Microstructure-properties relationship

Composite films of polyethylene oxide/cellulose nanocrystals (PEO/CNCs) comprising up to 75wt.% CNCs were obtained via solution casting. For the first time, investigations of the PEO/CNCs composite films over a wide composition range were carried out. Morphology, crystalline structure, thermal stability and the resulting reinforcing effect on the PEO matrix were studied. Polarizing optical microscopy (POM), scanning electron microscopy (SEM), X-ray diffraction (XRD), differential scanning calorimetry (DSC), thermogravimetric (TG) analysis, Fourier transform infrared spectroscopy (FTIR), and tensile testing were used to examine the properties of the composites. The revealed extreme dependences of the composite properties refer to the CNCs content of 15–35wt.%. This composition range is characterized by destruction of PEO spherulites and appearance of a pronounced PEO fibrillar structure.

Nano-assembly of intertwining lamellae of opposite bending senses in poly(ethylene oxide) co-crystallizing with poly(p-vinyl phenol)

Strongly interacting amorphous poly(p-vinyl phenol) (PVPh) was added into semi-crystalline poly(ethylene oxide) (PEO) at 20 wt.% to generate dendritic lamellae of alternating birefringence colors, which intertwine roughly in the radial directions as periodic stripes. Optical and atomic-force microscopy analyses are performed on revealing lamellae assembly in highly dendritic PEO spherulites by crystallizing PEO/PVPh (80/20) at crystallization temperature (T c ) equals to 45 °C. The lamellae of two opposite colors in the same PEO spherulite quadrant are exactly of same geometry (of elongated plates, each being 0.2 μm in width and 2–5 μm in length), but they fan out +/−45o, respectively, as they grow away from the radial direction. The opposite colored-lamellae are radiating out in radial directions, interweaving each other to display alternating colors in radial alignment. However, such alternating colors can also be similarly seen in ring-banded spherulites in many polymers. The results presented in this study have demonstrated that the lamellae of alternating birefringent colors cannot only be seen in banded spherulites, but also in spherulites with radial dendrites.

POLYMER ELECTROLYTE BLENDS OF MONO-CARBOXYLIC ACID–MODIFIED EPOXIDIZED NATURAL RUBBER AND POLY(ETHYLENEOXIDE)

ABSTRACTNatural rubber with 50% of isoprene units epoxidized (ENR50) was treated with excess of mono-carboxylic acids to completely ring open the epoxide groups. The reaction was carried out by heating ENR50 dissolved in toluene with each of acetic and benzoic acid separately at 105 °C. The ring-opening reaction has produced hydroxyl –OH and ester –O-COR groups, leading to an increase in Tg. The products were characterized by Fourier transform infrared spectroscopy, nuclear magnetic resonance spectroscopy, thermal gravimetric analysis, and differential scanning calorimetry. By the solution casting method, each of the modified ENR50s was blended with poly(ethylene oxide) (PEO) in various ratios in toluene, and 2% lithium perchlorate (LiCIO4) was added as the dopant. Results show that the modified ENR and PEO formed incompatible blends. The PEO spherulite growth rate in the blends increased with PEO content. The electrical conductivity was found to increase with the weight fraction of PEO in the blend. At the ratio of 25/75, the acetic acid–modified ENR50/PEO blend exhibits a conductivity value of 3.1 × 10−8 S cm−1. The benzoic acid–modified ENR50/PEO achieved conductivity of 5.8 × 10−7 S cm−1 at the ratio of 30/70. These blends form conducting polymer electrolytes with potential application in batteries.

Dielectric dispersion and relaxation studies of melt compounded poly(ethylene oxide)/silicon dioxide nanocomposites

The polymer nanocomposite films consisted of poly(ethylene oxide) (PEO) matrix with different weight percentage concentrations of silicon dioxide (SiO2) as nanofiller have been prepared by melt-pressed technique. The complex dielectric function, ac electrical conductivity, electric modulus and complex impedance spectra of the nanocomposite films have been investigated over the frequency range 20 Hz to 1 MHz, at room temperature. The real part of permittivity increases with decrease of frequency below 10 kHz, whereas these values remain almost constant in the high-frequency region. The high-frequency permittivity of these nanocomposites decreases with increase of SiO2 concentration. The relaxation peaks are observed in dielectric loss, loss tangent and loss modulus spectra of the nanocomposites which are corresponding to the PEO segmental motion (local chain dynamics). It is found that the PEO chain dynamics is much faster in the nanocomposites as compared to that in the pristine PEO film. The real part of electrical conductivity spectra of these materials has linear behaviour of two different slopes in the frequency regions of above 10 kHz and below 1 kHz. The interactions between PEO chain and SiO2 nanoparticles, and their effect on PEO spherulites in these nanocomposites are explored by X-ray diffraction measurements.

Miscible crystalline/crystalline polymer blends of polyoxymethylene copolymer/poly(ethylene oxide) with interpenetrated spherulites and enhanced properties

Miscibility and crystallization behavior of a polymer blend consisting of two crystalline components, polyoxymethylene copolymer (Co‐POM) and poly(ethylene oxide) (PEO), have been investigated. Experimental results indicate that Co‐POM is thermodynamically miscible with PEO, as shown by the existence of single‐composition dependent glass transition temperature over the entire composition range. The crystal structures and spherulitic morphologies of (Co‐POM)/PEO blends were studied by X‐ray diffraction, differential scanning calorimetry, scanning electron microscopy, and polarizing light microscopy. It was found that the PEO spherulites crystallized within the matrix of the crystals of the pre‐existing Co‐POM phase and resulted in a high extent of interfibrillar segregation. The unique interpenetrated crystalline structure was beneficial for the sufficient contact between the two components and significantly improved both the toughing and the lubricating effect of PEO on the POM matrix. On incorporation of 30 wt% PEO, the notched impact strength of POM was enhanced from 6.7 to 10.3 MPa, by about 53.7%, while the elongation at break increased from 28.5% to 121.0%, by about 3.2 times. Furthermore, the friction coefficient drastically decreased from 0.35 to 0.17, demonstrating the enhanced tribological performance of the miscible blends. J. VINYL ADDIT. TECHNOL., 22:479–486, 2016. © 2015 Society of Plastics Engineers

Influence of Blend Composition on Crystallization of Poly(L-Lactic Acid)/Poly (Ethylene Oxide) Crystalline/Crystalline Blends

The effect of blend composition on crystallization morphology and behavior of a crystalline/crystalline blend, poly(l-lactic acid) (PLLA)/poly(ethylene oxide) (PEO), during slow, non-isothermal crystallization was studied by polarized light microscopy (PLM) connected with a hot-stage and differential scanning calorimetry (DSC). The results showed that all of the PLLA/PEO blends produced spherulites which gradually became bigger and looser, as well as coarser, with the increment of the PEO content, indicating that the PEO crystals was resided in the interlamellar or interfibrillar (between clusters of commonly oriented lamellae) regions of the PLLA spherulites. In the (25/75) and (10/90) blends, the nucleation and growth processes of the PEO spherulites could be clearly observed in the pre-existing PLLA spherulites. The onset crystallization temperature and the melting point of one component decreased with increasing the content of the other one owing to the good miscibility of the two components in the non-crystalline state and the interaction between their macromolecules, indicating that the crystallization of each component was influenced by the other one.

Phase behaviour and morphology of composite comprising of poly(ethylene oxide), polyacrylate and lithium perchlorate

Thin films of poly(ethylene oxide) (PEO) and polyacrylate (PAc) blend and the composite PEO/PAc/lithium perchlorate (LiClO4) are prepared via solution casting method. Thermal analysis using differential scanning calorimetry depicts that both the PEO/PAc blend and the PEO/PAc/LiClO4 composite form single phase systems, as evident from the presence of single composition-dependant glass transition temperature (Tg). Polarized optical microscopy (POM) was applied to study the spherulite growth rate and morphology of PEO in both the PEO/PAc blend and PEO/PAc/LiClO4 composite. Homogeneity in the phase behaviour of the PEO/PAc blend and the PEO/PAc/LiClO4 composite is reaffirmed by the continuous suppression of the growth rate and the severe deformation and coarseness of the PEO spherulite with ascending PAc content in the blend and increasing LiClO4 concentration in the composite. Additionally, the amount of salt that causes macro-phase separation in the neat polymers and the PEO/PAc blends is governed by the coordination ability of the polymer, especially PEO, to the Li+ ion. Results from both thermal analysis and POM reflect the higher preference of LiClO4 for PEO than PAc. Therefore, PEO/PAc 85/15 blend is observed to exhibit the highest capability to interact with the Li+ ion.

A novel PEO-based composite polymer electrolyte with NaAlOSiO molecular sieves powders

Ion-conducting thin film polymer electrolytes based on poly(ethylene oxide) (PEO) complexes with NaAlOSiO molecular sieves powders has been prepared by solution casting technique. X-ray diffraction, scanning electron microscopy, differential scanning calorimeter, and alternating current impedance techniques are employed to investigate the effect of NaAlOSiO molecular sieves on the crystallization mechanism of PEO in composite polymer electrolyte. The experimental results show that NaAlOSiO powders have great influence on the growth stage of PEO spherulites. PEO crystallization decrease and the amorphous region that the lithium-ion transport is expanded by adding appropriate NaAlOSiO, which leads to drastic enhancement in the ionic conductivity of the (PEO)16LiClO4 electrolyte. The ionic conductivity of (PEO)16LiClO4-12 wt.% NaAlOSiO achieves (2.370 ± 0.082) × 10−4 S · cm−1 at room temperature (18 °C). Without NaAlOSiO, the ionic conductivity has only (8.382 ± 0.927) × 10−6 S · cm−1, enhancing 2 orders of magnitude. Compared with inorganic oxide as filler, the addition of NaAlOSiO molecular sieves powders can disperse homogeneously in the electrolyte matrix without forming any crystal phase and the growth stage of PEO spherulites can be hindered more effectively.

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

AbstractEffects 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 (Kg) and folding surface free energy (σe) 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

Melting behaviour, morphology and conductivity of solid solutions of PEO/PAc blends and LiClO4

The melting behaviours of poly(ethylene oxide)/polyacrylate (PEO/PAc) and PEO/PAc doped with LiClO4 were investigated by differential scanning calorimetry. The equilibrium melting temperature and the crystallinity of PEO show no significant variation with the addition of PAc but are suppressed by the incorporation of LiClO4. The deformed structure of PEO spherulite resulting from disrupted crystallisation is observed in salt doped PEO and its blends. Conductivity as a function of salt concentration is studied using the power law. Lower ion mobility and correlation of ions for PAc corroborate with its lower conductivity as compared to PEO. Despite a reasonable amount of LiClO4 being solvated by PAc, the conductivity of the solid solutions of PEO/PAc blends is primarily governed by PEO.

Lamellar orientation and interlamellar cracks in co-crystallized poly(ethylene oxide)/poly(L-lactic acid) blend

The correlation between the lamellar orientation in ring-banded spherulites and crack patterns in blends of two crystalline polymers crystallized in two steps was investigated. The two polymers were poly(ethylene oxide) (PEO) and poly(L-lactic acid) (PLLA) with a low molecular weight. The techniques used for this investigation included polarizing light optical microscopy, scanning electron microscopy and atomic force microscopy. Crack formation was influenced by the ring band patterns in PLLA and overlapping or impingement between PEO spherulites upon cooling. By extracting the water-soluble PEO from the PEO/PLLA blend, the inner morphology of the lamellar textures was further revealed to have a complex pattern. It consisted of the outer macro-lamellae with a flat-on width of 20 μm and twisting micro-lamellae with a 1–2 μm edge-on width. As the excess PEO was etched off from the valley and the interlamellar crevices of the PLLA lamellae, the outer macro-lamellae plates (∼20 μm flat-on width) exhibited up and down periodicity with flat-on orientation. However, the micro-lamellae (with 1–2 μm edge-on width) with twisting were visible inside the cracks. Similar analysis of a PEO-rich composition, PEO/PLLA (80/20) blend with irregular ring bands and no cracks, revealed that the outer macro-lamellae were not present. However, all micro-lamellae twists in the ridge regions irregularly protrude out to create zig-zag banding. Atomic force microscopy (AFM) phase images for the ridge and valley regions of the water-etched poly(ethylene oxide)/poly(L-lactic acid) (50/50) blend crystallized at crystallization temperature (Tc)=110 °C. The AFM graph (5 μm×5 μm) of the ridge region b shows a texture different from that of the valley region c. The surface patterns of the lamellae in the valley and ridge in these two regions appeared as flat-on and edge-on lamellae, respectively. The anisotropicity of the platelet crystals in these two regions was also apparently different. The orientation of the crystal lamellae in the valley (region c) was circumferential, whereas that of the lamellae in the ridge (region b) was radial. The difference in orientation in the ridge and valley regions may account for the cracks in the ridge regions but not in the valley region.

Effect of poly(butylene succinate) crystals on spherulitic growth of poly(ethylene oxide) in binary blends of the two substances

AbstractThe effects of the lamellar growth direction, extinction rings, and spherulitic boundaries of poly(butylene succinate) (PBSU) on the spherulitic growth of poly(ethylene oxide) (PEO) were investigated in miscible blends of the two crystalline polymers. In the crystallization process from a homogeneous melt, PBSU first developed volume‐filling spherulites, and then PEO spherulites nucleated and grew inside the PBSU spherulites. The lamellar growth direction of PEO was identical with that of PBSU even when the PBSU content was about 5 wt %. PEO, which intrinsically does not exhibit banded spherulites, showed apparent extinction rings inside the banded spherulites of PBSU. The growth rate of a PEO spherulite, GPEO, was influenced not only by the blend composition and the crystallization temperature of PEO, but also by the growth direction with respect to PBSU lamellae, the boundaries of PBSU spherulites, and the crystallization temperature of PBSU, TPBSU. The value of GPEO first increased with decreasing TPBSU when a PEO spherulite grew inside a single PBSU spherulite. Then, GPEO decreased when TPBSU was further decreased and a PEO spherulite grew through many tiny PBSU spherulites. This behavior was discussed based on the aforementioned factors affecting GPEO. © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 47: 539–547, 2009

Suppression of crystallization in a plastic crystal electrolyte (SN/LiClO4) by a polymeric additive (polyethylene oxide) for battery applications

A basic problem with many promising solid electrolyte materials for battery applications is that crystallization in these materials at room temperature makes ionic mobilities plummet, thus compromising battery function. In the present work, we consider the use of a polymer additive (polyethylene oxide, PEO) to inhibit the crystallization of a promising battery electrolyte material, the organic crystal forming molecule succinonitrile (SN) mixed with a salt (LiClO4). While SN spherulite formation still occurs at low PEO concentrations, the SN spherulites become progressively irregular and smaller with an increasing PEO concentration until a ‘critical’ PEO concentration (20% molar fraction PEO) is reached where SN crystallization is no longer observable by optical microscopy at room temperature. Increasing the PEO concentration further to 70% (molar fraction PEO) leads to a high PEO concentration regime where PEO spherulites become readily apparent by optical microscopy. Additional diffraction and thermodynamic measurements establish the predominantly amorphous nature of our electrolyte–polymer mixtures at intermediate PEO concentrations (20–60% molar fraction PEO) and electrical conductivity measurements confirm that these complex mixtures exhibit the phenomenology of glass-forming liquids. Importantly, the intermediate PEO concentration electrolyte–polymer mixtures retain a relatively high conductivity at room temperature in comparison to the semicrystalline materials that are obtained at low and high PEO concentrations. We have thus demonstrated an effective strategy for creating highly conductive and stable conductive polymer–electrolyte materials at room temperature that are promising for battery applications.

Polymer blends based on PEO and starch: Miscibility and spherulite growth rate evaluated through DSC and optical microscopy

The miscibility and PEO spherulite growth rate in PEO/starch blends (starch from cassava) were evaluated using the depression in the melting point (by DSC) and optical polarized microscope, respectively, and compared to pure PEO. The PEO/starch blend ratio changed from 100/0 to 60/40 (weight/weight). The starch induces changes in PEO crystallization on PEO/starch blends but the crystallization rates do not change linearly to the blend ratio. For 90/10, 80/20, 70/30, 65/35 and 60/40 ratios, lower values for the equilibrium melting temperature were observed as compared to the pure PEO. The obtained interaction parameter value was − 0.25 by the use of Nishi–Wang equation. The depression in the equilibrium melting temperatures and the negative value for the polymer–polymer interaction parameter suggest that the blends are miscible in the molten state in the range of investigated ratios, except for the 95/05 ratio in which the equilibrium melting temperature increased relative to the pure PEO. The miscibility should be due to the H-bonds among the hydroxyl groups from starch and oxygen atoms of repeat units of PEO.

Effects of Blend Composition and Crystallization Temperature on Unique Crystalline Morphologies of Miscible Poly(ethylene succinate)/Poly(ethylene oxide) Blends

In a previous short communication (Macromolecules 2002, 35, 8251−8254), we reported a unique morphology in binary miscible crystalline poly(ethylene succinate) (PES)/poly(ethylene oxide) (PEO) polymer blends, in which two kinds of spherulites, corresponding to each component, respectively, grew simultaneously and PEO spherulites continued to crystallize inside PES spherulites on contact, forming interpenetrated spherulites. In the present work the effects of blend composition and crystallization temperature on the crystalline morphologies of PES/PEO blends were studied by optical microscopy in detail. The unique morphology of PES spherulites penetrated by PEO spherulites was observed for the blends with PEO content ranging from 50 to 90% in a wide crystallization temperature range. Furthermore, three novel and interesting crystalline morphologies were found depending on blend composition and crystallization temperature. First, new boundaries were formed by the growth of a single PEO spherulite itself afte...