Solid polymers doped with rare earth metal salts. II. Thermal behavior and morphology of the neodymium acetate–poly(ethylene oxide) system

Samples of poly(ethylene oxide), PEO, doped with neodymium acetate, Nd (Act)₃, were prepared and found to be microphase separated. At an EO/Nd (Act)₃ molar ratio no less than 4, wide-angle x-ray diffraction (WAXD) patterns and small-angle x-ray scattering (SAXS) data suggest that bulk Nd (Act)₃ and ionic clusters are both absent. It is inferred from differential scanning calorimetry (DSC) thermograms that in the presence of PEO, Nd (Act)₃ forms an amorphous phase which is different from the amorphous phase formed by Nd (Act)₃ alone. The tighter binding of CH₃COO^- to Nd³⁺, in comparison to Cl^-, appears to be responsible for the lack of true dissolution of Nd (Act)₃ in PEO, a behavior clearly distinct from a number of polymer-metal salt complexes reported in the literature. © 1993 John Wiley & Sons, Inc.     

Solid polymers doped with rare earth metal compounds. III. Formation and stability of macromolecular complexes comprising neodymium nitrate and dipivaloylmethane in poly(ethylene oxide)

The solubility, complexation, and morphology in the Nd(NO₃)₃-PEO and Nd(Dpm)₃-PEO systems were investigated using the FTIR, DSC, TGA, WAXD, and SAXS techniques. In both systems, dissolution was verified by the absence of features characteristic of the bulk-phase dopants detectable with WAXD and DSC, and complexation was evident from the FTIR spectral shifts involving the stretching motions of the EO unit. The extent of the Nd³⁺-EO interaction was found to be much stronger with Nd(NO₃)₃ than Nd(Dpm)₃. As a consequence, a T_g elevation from 222K in pure PEO to 335K at an EO/Nd³⁺ ratio (defined as n) of between 4.0 and 5.6 was observed in the Nd(NO₃)₃-PEO system. Moreover, completely dry and amorphous complexes were obtained at n ≥ 5.6, while residual moisture accompanying complexes at n ≤ 4 was found to persist upon prolonged vacuum drying. Being intrinsically hygroscopic at all doping levels, the Nd(NO₃)₃-PEO system was found to absorb moisture from the atmosphere resulting in wet amorphous complexes, although precipitation of Nd(NO₃)₃)·6H₂O was observed at n ≤ 4. It was proposed that moisture present in the Nd(NO₃)₃-PEO system be classified into two categories. One is tightly bound to Nd³⁺ to satisfy its coordination requirement, which was determined to be 11. The other is loosely bound, which is capable of being removed by heating and returning upon exposure to the atmosphere. It is the latter that can be readily quantified by the TGA technique and that lowers T_g via plasticization. In addition to the observed minor FTIR spectral shifts, a relatively weak Nd³⁺-EO interaction in the Nd(Dpm)₃-PEO system resulted in a lack of the T_g elevation for PEO, persistence of the crystalline portion of PEO at all doping levels, and the formation of new crystalline phases as revealed by the WAXD patterns and the DSC thermograms. The short-range order in PEO does not appear to be perturbed, but the SAXS data suggest that the long range-order is disrupted by the presence of Nd(Dpm)³ at an extremely low doping level (i.e., n ≥ 60). © 1994 John Wiley & Sons, Inc.     

Complex forming properties of crosslinked poly (ethylene oxide). I. Interaction of linear and crosslinked poly(ethylene oxide) with molybdenum(vi) salts

Evidence was found of donor–acceptor complexation of molybdenum(VI) compounds by linear and crosslinked PEO. The interaction was studied by optical and NMR spectroscopy and conductivity measurements in organic medium. PEO networks were capable of binding molybdenum salts even in aqueous solution. The character of the interaction is considered to be essentially different from complex formation with alkali metal salts. This is manifested in the relatively low values of the stability constants of complexes with linear PEO. A remarkable effect of crosslinking on the binding capacity of PEO is registered resulting in an increase of complexation constants in chloroform by two orders of magnitude.     

Complex formation between poly(ethylene oxide) and alkali picrates

The interaction of poly(ethylene oxide) with alkali picrates in tetrahydrofuran and dioxane was studied by optical and NMR spectroscopy and conductance measurements. Evidence was found of the formation of two kinds of solvation complex, differing in the nature of the ion pairs involved. A strong anion effect on cation binding to the polyether was demonstrated.     

Polyacrylamide–graft–poly(ethylene oxide)

Water-soluble graft copolymers were synthesized by copolymerization of acrylamide with mono-methoxy-poly(ethylene oxide)-methacrylates (Me-PEO-MA). The Me-PEO-MA macromers were synthesized by a catalytic esterification of methacrylic acid with mono-methoxy-poly(ethylene glycol)s with different molecular weights. The graft copolymers obtained were characterized by ¹H-NMR spectroscopy, gel permeation chromatography (GPC) and Ubbelohde viscosimetry. The rheological behaviour of aqueous polymer solutions, which are expected to show hydrophobic association at elevated temperatures, was studied with a cone and plate-rheometer.     

Interactions of inorganic salts with poly(ethylene oxide)

Evidence is presented for the interaction of metal salts such as potassium iodide with polyethers such as poly(ethylene oxide). This interaction is sufficiently marked that the incorporation of 10–30% of the salt in the bulk polymer markedly reduces crystallinity while retaining compatibility. Examination of electroviscous effects in methanol demonstrates that the salt–polymer adduct behaves as a typical polyelectrolyte at low salt concentrations, while the polymer in absence of salt is essentially insoluble in methanol at room temperature. Measurements of the equilibrium between salt and polymer along with a study of various molecular weight polymers strongly suggest that one salt molecule associates with about nine ethylene oxide units. It is proposed that the association is due to an ion–dipole interaction, and the anion is tentatively postulated as the species directly associating with the polymer. The association of other metal salts and other polymers are interpreted in this light. The significance of these results in interpreting salting-in phenomena is also discussed.     

Synthesis and block‐specific complexation of poly(ethylene oxide)–poly(tetrahydrofuran)–poly(ethylene oxide) triblock copolymers

Well‐defined ABA triblock copolymers in which A stands for poly(ethylene oxide) (PEO) and B for poly(tetrahydrofuran) (PTHF) were synthesized by end‐capping bifunctionally living PTHF with different polyethylene glycol–monomethylethers. Differential scanning calorimetry analysis of these copolymers showed two melting points: one around 55 °C due to the PEO blocks, and one around 30 °C due to the PTHF segments, demonstrating that these block copolymers show extensive phase separation. Upon addition of sodium thiocyanate, crystalline complexes with PEO were formed and as a consequence, the melting points of the PEO segments had shifted to approximately 170 °C, whereas the melting points of the PTHF segments decreased slightly. The obtained materials behave as thermoplastic elastomers up to 160–175 °C. The influence of the relative lengths of the PEO and the PTHF segments on the thermal and mechanical properties of the materials have been investigated. Copyright © 1999 John Wiley & Sons, Ltd.     

Poly[(methylene oxide) oligo(ethylene oxide)] vs. poly(ethylene oxide) as hosts for neodymium compounds

In view of the residual crystallinity in PEO found to limit the solubility of some Nd³⁺-compounds, amorphous PEO (aPEO) was synthesized for exploration as an alternative host. Complexation, solubility limit, morphology, and response to moisture absorption in the doped systems were investigated using FTIR, DSC, TGA, and WAXD techniques. Representing a perturbation to the structural regularity present in PEO, aPEO was found to present lower solubilities for dopants (Nd(act)₃ and Nd(acac)₃, both characterized by a weak Nd³⁺–ether oxygen interaction. On the other hand, no difference in solubility was observed for dopant Nd(NO₃)₃, characterized by a strong Nd³⁺–ether oxygen interaction. Laser interferometry was employed to assess film homogeneity of the Nd(NO₃)₃-doped systems across a 20-mm diameter, and the measured peak-to-valley distortion values were observed to be encouraging for practical applications. © 1994 John Wiley & Sons, Inc.     

Complex formation of daunomycin with poly(vinylpyrrolidone) and poly(ethylene glycol)

Russian Journal of General Chemistry - Complexes of the anthracycline antitumor antibiotic daunomycin with biocompatible polymer carriers, poly(vinylpyrrolidone) and poly(ethylene glycol), have...     

Structure of poly(ethylene oxide) complexes. II. Poly(ethylene oxide)–mercuric chloride complex

The structure of the crystalline complex of poly(ethylene oxide) with mercuric chloride, whose composition is (CH₂CH₂O)₄ · HgCl₂, has been determined by x-ray diffraction. The unit cell is orthorhombic with the dimensions of a = 13.55 Å, b = 8.58 Å, and c (fiber axis) = 11.75 Å, and the unit cell contains 4 HgCl₂ molecules and 16 CH₂CH₂O units. Four chains pass through the lattice and four monomeric units are contained in the fiber identity period. The space group is Ccmm–D_2h¹⁷, Ccm2¹–C_2v¹², Cc2m–C_2v¹⁶ or C222₁–D₂⁵. The positions of Hg and Cl atoms have been determined by the Patterson function synthesized by the use of intensity data of the fiber sample, and the molecular conformation of poly(ethylene oxide) has been determined by examining the space not occupied by mercuric chloride molecules in the crystal lattice. The conformation of polyethylene oxide in the complex has been found to be the form of T₅GT₅G ; that is, where G and G mean the right- and left-handed gauche forms, respectively. This molecular structure has been confirmed further by the results of the Fourier syntheses by using the more accurate data refined by the intensity measurements with a diffractometer on the powder sample. The bond length between Hg and Cl in the complex (2.30 Å) is a little longer than that of HgCl₂ in the crystal (2.25 Å). This is consistent with the fact that the infrared absorption band associated with the antisymmetric stretching vibration of HgCl₂ shifts to 353 cm^?1 in the complex from 367 cm^?1 in the crystal. It was also found that another type of complex, giving a different infrared spectrum and x-ray diffraction pattern, was obtained when the original complex was soaked much longer in a saturated ether solution of HgCl₂.     

Ion conductivity of poly(ethylene oxide)-based polyurethane networks containing alkali metal salts

Ion conductivity of poly(ethylene oxide) (PEO)-based polyurethane networks containing alkali metal salts has been investigated. Consequently, it has been revealed that the conductivity is dependent on the following parameters: lattice energy of the alkali metal salt, concentration of alkali metal salt, and the cross-linking density of the network polymer (which is a function both of the amount of cross-linking agent and the molecular weight of PEO). Under optimal conditions, the conductivity at ambient temperature corresponded to 2.51 × 10^?5 Scm^?1, which is greater than that of a typical alkali metal-PEO system by a factor of about 10² to 10³. Moreover, from the standpoint of the application to electrochromic displays (ECD), tensile bond strength between the polymer electrolytes and tungsten trioxide (WO₃), which is the most promising electrochromic material, has been evaluated. The bonding strength of the bond of WO₃ with the present electrolyte has been found to be much larger than that of the alkali metal-PEO system.     

Compatibility in poly(ethylene oxide)–poly(methyl methacrylate) blends

The compatibility of poly(ethylene oxide)-poly(methyl methacrylate) (PEO-PMMA) blends were examined covering the complete composition range. Up to 20% of PEO content films were transparent and glass transition temperatures were determined by DSC and by refractive index vs. temperature measurements. Only one T_g was obtained for these samples and the relationship between T_g and composition has been evaluated. At higher PEO content crystallization took place and the films were opaque. Melting temperatuures of PEO in blends were determined by DSC. Melting point depression was observed for increasing proportion of PMMA and the binary interaction parameter has been calculated.     

Compatibility of poly(ethylene oxide)–poly(vinyl acetate) blends

The compatibility of poly(ethylene oxide)–poly(vinyl acetate) (PEO-PVA) blends was examined at five compositions covering the complete range. Samples were prepared by coprecipitation and solution casting. Dynamic mechanical properties were studied at 110 Hz between ?120 and 65°C for dry, quenched, and annealed samples. The study also included tensile testing at 25°C, examination of blend morphology, and DSC measurements at elevated temperatures. Optical microscopy revealed that crystallization of PEO proceeds essentially unhindered at up to 25% poly(vinyl acetate) content by weight. Higher levels of this component drastically reduce spherulite size, and at the highest PVA compositions there was no evidence of crystallization. Thermomechanical spectra of quenched and annealed samples indicate limited mixing of the two components except for the higher (>75%) PVA compositions. Tensile properties show a mutual reinforcement at 10-25% PVA content due to possible polymer segment association. The melting-point depression of PEO is significant above 25% PVA and has been attributed to morphological changes of the PEO crystalline phase.     

Complex formation of p-nitrocalix[6]arene with rare earth metal ions.

p-Nitrocalix[6]arene (CALX-N6, L) formed a 1:1 metal complex, ML, with light rare earth metal ions (M3+), such as La3+, Pr3+ and Nd3+ except Ce3+, but formed a 1:2 (M(3+):L) complex, ML2 (the charge of the complex is omitted) with heavy rare earth metal ions, such as Sm(3+)-Lu3+ including Y3+. The conditional stability constants of these 1:1 and 1:2 complexes, KML and KML2, were measured by a ligand displacement method using absorption spectrophotometry in 4% (v/v) acetone aqueous solution at pH 9.65 +/- 0.15 and 25 degrees C.     

Crystallization of polystyrene–poly(ethylene oxide) multiblock copolymers

The heat of fusion of poly(ethylene oxide) blocks has been measured by DSC on twelve polystyrene–poly(ethylene oxide) multiblock (AB)_n copolymers and two ABA triblock copolymers after conditioning at various times and temperatures. Regardless of the length of polystyrene blocks, copolymers with poly(ethylene oxide) blocks with M?_n = 404 showed no heat of fusion, those with M?_n = 900 almost no peaks, those with M?_n = 1960 small broad peaks, and those with M?_n = 5650 clearly observable peaks. the greatest heat of fusion measured for block copolymers was 60–70% of the value for hompolymer. Small-angle x-ray patterns are given. The relation between crystal growth and block length is discussed.     

Spin label study of phase morphology and polymer segmental motion in poly(acrylic acid)–poly(ethylene oxide) complex

The ESR lineshapes of nitroxide radical end‐labeled on poly(ethylene oxide) (SLPEO) for the pure polymer and for different weight ratio complexes with poly(acrylic acid) (PAA) were studied as a function of temperature. For SLPEO one spectral component was detected in the entire temperature range, indicating that the spin label was in the homogeneous phase domain. For all PAA–PEO complexes two spectral components with different rates of motion, a ‘fast’ and a ‘slow’ component, were observed, which indicates the existence of microheterogeneity at the molecular level: the more mobile the PEO‐rich microphase, the more rigid is the PAA‐rich microphase. On the other hand, the SLPEO polymer segmental motion was restricted owing to the hydrogen bond interaction between the carboxyl proton in PAA and the ether oxygen in PEO. This restriction was exacerbated with increasing the PAA content in the complex, which could be further substantiated through the calculated S and τ_c values. Copyright © 2003 John Wiley & Sons, Ltd.     

Study of interpolymer complex formation of polyvinylpyrrolidone and poly(ethylene oxide) with phenolic polymers in nonaqueous media

A study was made of interpolymer complex formation between polyvinylpyrrolidone (PVP) and poly(ethylene oxide) (PEO) with phenolic polymers (PPF) in an acetone–methanol mixture by several methods; for example, viscosity, potentiometry, conductometry, turbidity, and precipitate (complex) weight. A distinct stepwise complex formation between PVP and phenolic polymers was observed by these methods. As in polycarboxylic acid, however, PEO formed a 1:1 complex with phenolic polymers. Some of these observations have been interpreted in terms of the structure of the polymers, preferential solvation of the component polymers, and the probable change in conformation of the complex molecules in mixed solvents.     

Crosslinked poly(ethylene oxide) modified with tetraalkylammonium salts as phase transfer catalyst

Radiation crosslinked poly(ethylene oxide)s (PEO) modified with two tetraalkylammonium salts: allyldimethyldodecylammonium bromide and ethylmethacrylate dimethyldodecylammonium bromide were prepared. They have been characterized by elemental analysis, IR, ¹H-NMR spectra, and DSC measurements. Their activity as phase transfer catalysts (PTC) in the model displacement reaction of 1-bromooctane with aqueous sodium cyanide were studied. The reaction kinetics were followed under pseudo-first-order conditions. Small amounts of onium salt inserted into the PEO network gave rise to a five time increase in the rate constant. The recovered catalysts could be re-used without loss of activity. © 1995 John Wiley & Sons, Inc.     

Synthesis and characterization of polystyrene–poly(ethylene oxide)–heparin block copolymers

A procedure for the preparation of new block copolymers composed of a hydrophobic block of polystyrene, a hydrophilic spacer-block of poly(ethylene oxide) and a bioactive block of heparin was investigated. Polystyrene with one amino group per chain was synthesized by free radical oligomerization of styrene in dimethylformamide, using 2-aminoethanethiol as a chain transfer agent. This amino group was used in the coupling reaction with amino-telechelic poly(ethylene oxide) to produce an AB type diblock copolymer with one amino group per polystyrene (PSt)–poly(ethylene oxide) (PEO) chain. The amino-semitelechelic oligo-styrene was converted into the isocyanate-semitelechelic oligo-styrene using toluene 2,4-diisocyanate and subsequent coupling with H₂N–PEO–NH₂ afforded AB type block copolymers with terminal amino groups. The coupling of PSt–PEO–NH₂ with heparin was performed in a DMF–H₂O mixture, first by activating the heparin carboxylic groups with EDC at pH 5.1–5.2 and subsequently reacting the activated carboxylic groups with the amino groups of the PSt–PEO–NH₂ at pH 7.5. Depending on the molecular weights of the diblock copolymer used 25–29% w/w heparin was incorporated. These polymers will be further evaluated for their blood-compatibility.