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. © 2000 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 38: 1045–1052, 2000     

Nanoheterogeneity in PEO/PMMA blends probed by 129Xe-NMR

Xenon has been used as a structural probe of solid poly(ethylene oxide)/atactic poly(methyl methacrylate) (PEO/PMMA) blends of concentrations 10/90 to 75/25. ¹²⁹Xe-NMR spectra at 293 K show significant changes in line width and chemical shift as the blend composition is varied. The ¹²⁹Xe spectra are interpreted in terms of exchange between amorphous single-phase PEO and PMMA domains. It is shown that a simple two-site exchange model can be used to calculate spectra which fit the experimental data over the whole concentration range. Xe exchange between blend subregions is demonstrated also by a two-dimensional NMR experiment. The PEO/PMMA results are compared to previously published poly(vinylidene fluoride)/PMMA ¹²⁹Xe spectra. © 1997 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 35: 2681–2688, 1997     

Strength of hydrogen bonding in the novolak-type phenolic resin blends

The specific interaction strength of novolak-type phenolic resin blended with three similar polymers [i.e., poly(ethylene oxide) (PEO), poly(ethylene glycol) (PEG), and poly(vinyl alcohol) (PVA)] were characterized by means of glass transition temperature behavior and Fourier transform infrared (FTIR) spectroscopy. The interassociation formed within phenolic blends with the addition of a modifier not only overcomes the effect of self-association of the phenolic upon blending, but also increases the strength of phenolic blend. The strength of interassociation within the phenolic blend is the function of the hydrogen bonding group of a modifier, in increasing order, is phenolic/PVA, phenolic/PEG, and phenolic/PEO blend, corresponding to the result of “q” value in the Kwei equation. The FTIR result is in agreement with the inference of T_g behavior. In addition, the fact that the specific strength of hydrogen bonding of hydroxyl–hydroxyl is stronger than that of hydroxyl–ether can also be concluded. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 1721–1729, 1998     

Polymer decoration study in chain folding behavior of solution-grown poly(ethylene oxide) crystals

The polymer decoration method based on the vaporization and condensation-crystallization of polyethylene (PE) upon the fold surface of polymer crystals has been widely used to study the chain folding behavior of the crystals. When this method was utilized to study solution-grown high molecular weight poly (ethylene oxide) (PEO) lamellar crystals, the highly anisotropic, low molecular weight fragment PE decorated become oriented parallel to the fold direction and form rods, which can be observed by transmission electron microscopy (TEM) and electron diffraction (ED). The growth sectors were clearly observed. From the ED patterns the {200} planes of the orthorhombic low molecular weight PE rod crystals can be observed, and the c-axis of these crystals is aligned parallel to the {120} growth planes of the PEO crystals. The decoration results indicate that the major fold orientation of high molecular weight PEO single crystals grown from dilute solution is along the {120} planes. © 1995 John Wiley & Sons, Inc.     

聚氧乙烯大单体与甲基丙烯酸甲酯的共聚合及其共聚物的研究

研究了聚氧乙烯（ＰＥＯ）大单体与甲基丙烯酸甲酯的溶液共聚合，考察了引发剂用量，单体总浓度、投料比、反应时间对共聚物组成和分子量的，ＩＲ、ＨＮＭＲ、ＧＰＣ、ＶＰＯ、ＤＳＣ航透射电等测定结果表明，经纯化的共聚物具有预期的结构，且呈现微相分离，体外人体正常抗凝血浆复钙时间测定结果显示：共聚物的抗凝血明显好于玻璃和ＰＭＭＡ均聚物，且随共聚物中ＰＥＯ含量的增加而增强，经水化处理的共聚物的抗凝血性比未经处理的     

Controlled release of indole‐3‐butyric acid (IBA)—based on polymeric matrix prepared by ionizing radiation

Polyacrylamide/polyethylene oxide (PAAm/PEO) controlled release matrices were designed to obtain a better control over the concentration of indole‐3‐butyric acid (IBA). PAAm/PEO incorporated IBA was prepared by exposing aqueous solutions of PEO, PAAm, crosslinking agent N,N′‐methylene‐bisacrylamide, and IBA mixtures to electron beam irradiation. PAAm/PEO copolymer structural property relationships that affect its controlled release behavior were determined. Analysis of the results obtained indicated that it is possible to optimize IBA controlled release by adjusting the dimensions and crosslinking degree of the copolymer as well as the concentration of the incorporated IBA. The crosslinking degree of the copolymer can be controlled by governing the irradiation dose, polymer blend composition and/or the amount of crosslinking agent. IBA release rates have been investigated as a function of environmental conditions, such as the changes in pH and temperature to determine the factors, which mostly contribute to the release of IBA. The effect of PAAm/PEO–IBA matrix on the average height of corn (Zea mayz) plant was investigated. The results obtained, revealed that PAAm/PEO‐IBA systems have a capability to deliver IBA slowly and continuously. As a result, the development of root and vegetative systems of Zea mayz plant was greatly promoted. Copyright © 2004 John Wiley & Sons, Ltd.     

Thermal and structural characterization of poly(ethylene-oxide)/keratin blend films

Blends of poly(ethylene oxide) (PEO) and keratin were prepared with the aim of obtaining bio-compatible materials suitable for film and fibre production. Aqueous keratin solutions, prepared by keratin extraction from wool with urea, m-bisulphite and sodium dodecyl sulphates (SDS), filtration and dialysis, were added with different amounts of PEO and solid films were prepared by casting. The addition of SDS prevents protein aggregation. Morphological, thermal and spectroscopic analysis of the films pointed out that keratin hinders the PEO crystallization process, since a progressive decrease in the size of PEO spherulites is observed and the melting point and the related enthalpy decrease with increasing the keratin content. On the other hand, according to thermal and spectroscopic investigations. PEO seems to interfere with the keratin self-assembling giving the protein a different thermal behaviour.     

Functionalization of gold electrode surface with heterobifunctional poly(ethylene oxide)s having both mercapto and aldehyde groups

We synthesized heterobifunctional poly(ethylene oxide) (PEO) (α‐formyl‐ω‐mercapto‐PEO; CHO‐PEO₄₀₀‐SH, average molecular weight of PEO part being 400), which had both an aldehyde group as a binding site with amino group of protein and a mercapto group for gold electrode surface. The CHO‐PEO₄₀₀‐SH was adsorbed on a gold electrode surface and cytochrome c (cyt.c) was fixed on this modified electrode. The redox response of covalently immobilized cyt.c was observed on the cyclic voltammetry measurement, showing that CHO‐PEO₄₀₀‐SH can be used as a linker to fix cyt.c on an electrode. Another type of heterobifunctional PEO (α‐formyl‐ω‐(2‐pyridyldithio)‐PEO; CHO‐PEO₃₀₀‐SS‐Py), which had an aldehyde group and a 2‐pyridinethiol (2‐Py) through disulfide bond, was synthesized to form co‐adsorbed monolayer of PEO chain and 2‐Py on an electrode surface. It was expected, due to the spacer with shorter PEO chain and lower surface density, that better redox response of the fixed cyt.c was obtained. However, the redox response of fixed cyt.c was not detected on the CHO‐PEO₃₀₀‐SS‐Py modified gold electrode. Instead, this heterobifunctional PEO was found to function as a good promoter for cyt.c dissolved in phosphate buffer solution. Copyright © 2003 John Wiley & Sons, Ltd.     

Investigation of mechanical properties of polyvinyl chloride-polyethylene oxide (PVC-PEO) based polymer electrolytes for lithium polymer cells

Polymer electrolytes composed of a blend of polyvinyl chloride-polyethylene oxide (PVC-PEO) as a host polymer, lithium triflate (LiCF₃SO₃) as a salt, mixture of ethylene carbonate (EC) and dibuthyl phthalate (DBP) as plasticizers and silica (SiO₂) as the nanocomposite filler were studied. Results suggest that PVC-PEO blending exhibits improved mechanical strength compared to that of pure PEO. The introduction of LiCF₃SO₃ changes the mechanical properties of PVC-PEO blends from hard and brittle to soft and tough. In PVC-PEO:LiCF₃SO₃ (70:30) system, the Young’s modulus value decreases from 5.30 × 10⁻¹ MPa to 4.78 × 10⁻⁴ MPa and the elongation at peak value increases from 3.71 mm to 32.09 mm with the incorporation of DBP and EC. The deteriorated mechanical properties with the addition of plasticizers are overcome with the addition of SiO₂ as nanocomposite filler. In PVC-PEO-LiCF₃SO₃-DBP-EC system, the addition of 5% SiO₂ increases the Young’s modulus value from 4.78 × 10⁻⁴ MPa to 1.51 × 10⁻³ MPa. The improvement of the mechanical properties reveals greater dispersion of SiO₂ particles in PVC-PEO blend based polymer electrolytes. In practical lithium polymer cells, inorganic fillers are frequently added to improve the mechanical strength of the electrolyte films.     

Enhanced ionic conductivity of poly(ethylene oxide) (PEO) electrolyte by adding mesoporous molecular sieve LiAlSBA

Mesoporous molecular sieve LiAlSBA was prepared via an ion exchange process with mesoporous AlSBA directly, which has a regular 2D hexagonal structure with pore size about 7 nm. It was added into poly(ethylene oxide) (PEO) solid electrolyte as filler. The characteristics of the composite polymer electrolyte were determined by XRD, DSC, TGA, FTIR, PLM and electrochemical methods. Compared with bare PEO electrolyte, the adding of dispersed LiAlSBA powder improved the ionic conductivity of PEO polymer electrolyte more than three orders. The reason for it is that mesoporous LiAlSBA powder acts as crystal cores in PEO composite electrolyte and fines the crystallites, decreases the crystallinity, which provides much more continuous amorphous domain for Li⁺ moving easily in PEO electrolyte. Besides, lithium ions of the mesoporous molecular sieves can hop from one site to another along the surface of the mesoporous channels, this mechanism is absent in the case of common nano-ceramic fillers in PEO electrolyte.