Preparation and properties of poly(ethylene oxide) star polymers

Poly(ethylene oxide) (PEO) star polymers were prepared by anionic polymerization of methacryloyl chloride and glyceryl trimethacrylate with sec‐butyllithium in cyclohexane. The ensuing polymers were grafted with poly(ethylene glycol) of molecular weight 400. The final product was washed with methylene chloride and analyzed with infrared spectroscopy, differential scanning calorimetry, and thermogravimetry. Star polymers of PEO were also prepared by anionic polymerization of glycidol with sec‐butyllithium in cyclohexane. The initiator was chosen so as to yield a polymer of 10,000 molecular weight. The resulting polymers were analyzed by nuclear magnetic resonance, infrared spectroscopy, and thermogravimetry. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 87: 322–327, 2003     

Phase behavior of aqueous systems containing block copolymers of poly(ethylene oxide) and poly(propylene oxide)

Phase behavior of aqueous systems containing block copolymers of poly(ethylene oxide (PEO) and poly(propylene oxide) (PPO) was evaluated by building up temperature-concentration phase diagrams. We have studied bifunctional triblock copolymers (HO-PEO-PPO-PEO-OH) and monofunctional diblock copolymers (R-PEO-PPO-OH and R-PPO-PEO-OH, where R length is linear C₄ and C_12–14). The cloud points of the polymer solutions depended on EO/PO ratio, polarity, R length and position of the hydrophilic and hydrophobic segments along the molecule. Such factors influence on the solutions behavior was also analyzed in terms of critical micelle concentration (CMC), which was obtained from surface tension vs. concentration plots. Salts (NaCl and KCl) added into the polymer solutions change the solvent polarity decreasing the cloud points. On the other hand, the cloud points of the polymer solutions increased as a hydrotrope (sodium p-toluenesulfonate) was added. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 66: 1767–1772, 1997     

Neutron scattering of hydrophobically modified poly(ethylene oxide) in aqueous solutions in the presence of latex particles

The structure of aqueous solutions of hydrophobically end-capped poly(ethylene oxide), PEOM, in the presence of solid particles (latex) was investigated by small angle neutron scattering. Mono- and di-functionalised PEOMs with the same ratio of hydrophilic to aliphatic (C₁₆H₃₃) hydrophobic groups of molecular weights 16?000 and 32?000 g mol⁻¹, respectively, were compared. We used solvent conditions in which either PEOM or latex were matched by varying the ratio of water to heavy water. Initially, a decrease in the scattering intensity at small angles was observed when PEOM was added to a suspension of latex at constant concentration. A peak was observed in the structure factor which indicated repulsion between particles. The position of the peak lied at a lower q value for mono-functionalised PEO than for di-functionalised PEO. This observation may be explained by the formation of bridges between aggregates by the di-functionalised PEOM. On varying the solvent, the characteristic peak of PEOM alone disappears at low polymer concentrations due to PEOM adsorption onto the latex particles but reappears at higher polymer concentrations.     

Aggregate formation in poly(ethylene oxide) solutions

Static light scattering and viscosity measurements were performed on different molecular weight poly (ethylene oxide) to see the formation of aggregates in its dilute solutions. Viscosity measurements were carried out for PEO samples in water and methanol at 20–45°C and in chloroform at 20–30°C. Using Huggin's equation, the viscosity plots showed distinct upward curvature indicating the presence of aggregates in both PEO/H₂O and PEO/CH₃OH solutions The [η] values for PEO/H₂O and PEO/CH₃OH system were 2–4 times as large as observed for other linear flexible polymers in good solvents thus showing extensive coil swelling/aggregation. This is also apparent from the exponent a values of the Mark–Houwink–Sakurada equation. Light Scattering results using Zimm method showed that aggregation occurred in low molecular weight samples; however, in higher molecular weight samples there was a little evidence for aggregation both in water and methanol. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 2578–2583, 2006     

Studies on aluminum-isopropoxide doped poly(ethylene oxide), poly(vinyl alcohol), and poly(ethylene oxide)-poly(vinyl alcohol) blends

Poly(ethylene oxide), poly(vinyl alcohol), and their blend in a 40 : 60 mole ratio were doped with aluminum isopropoxide. Their structural, thermal, and electrical properties were studied. Aluminum isopropoxide acts as a Lewis acid and thus significantly influences the electrical properties of the polymers and the blend. It also acts as a scavanger for the trace quantities of water present in them, thereby reducing the magnitude of proton transport. It also affects the structure of polymers that manifests in the thermal transformation and decomposition characteristics. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 69: 2147–2157, 1998     

Synthesis of amphiphilic microspheres by suspension copolymerization of styrene and poly(ethylene oxide) macromonomer

Amphiphilic microspheres, ranging in size from 3 to 35 μm, were prepared by suspension copolymerization of styrene with poly(ethylene oxide) vinylbenzyl (PEO–VB) macromonomer by changing polymerization conditions. It was found that an increase in the amount of dispersant and the PEO–VB concentration resulted in decreases of the size and size distribution of amphiphilic microspheres. The morphology, size, and size distribution of amphiphilic microspheres were characterized by scanning electron microscopy. The structure of copolymer was confirmed by infrared spectroscopy, differential scanning calorimetry, elemental analysis, and X‐ray photoelectron spectroscopy. The content of the hydroxyl groups localized in the microspheres ranged from 0.05 to 0.2 mmol/g. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 333–339, 2001     

Comparison of micelles formed by amphiphilic poly(ethylene glycol)‐b‐poly(trimethylene carbonate) star block copolymers

In this article, we describe the synthesis and solution properties of PEG‐b‐PTMC star block copolymers via ring‐opening polymerization (ROP) of trimethylene carbonate (TMC) monomer initiated at the hydroxyl end group of the core PEG using HCl Et₂O as a monomer activator. The ROP of TMC was performed to synthesize PEG‐b‐PTMC star block copolymers with one, two, four, and eight arms. The PEG‐b‐PTMC star block copolymers with same ratio of between hydrophobic PTMC and hydrophilic PEG segments were obtained in quantitative yield and exhibited monomodal GPC curves. The amphiphilic PEG‐b‐PTMC star block copolymers formed spherical micelles with a core–shell structure in an aqueous phase. The mean hydrodynamic diameters of the micelles increased from 17 to 194 nm with increasing arm number. As arm number increased, the critical micelle concentration (CMC) of the PEG‐b‐PTMC star block copolymers increased from 3.1 × 10^?3 to 21.1 × 10^?3 mg/mL but the partition equilibrium constant, which is an indicator of the hydrophobicity of the micelles of the PEG‐b‐PTMC star block copolymers in aqueous media, decreased from 4.44 × 10⁴ to 1.34 × 10⁴. In conclusion, we confirmed that the PEG‐b‐PTMC star block copolymers form micelles and, hence, may be potential hydrophobic drug delivery vehicles. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Ultraviolet-induced crosslinking of solid poly(ethylene oxide)

Poly(ethylene oxide) (PEO) of molecular weight from 200,000 to 2,000,000 was crosslinked by exposure to ultraviolet radiation with a high-pressure 150 W mercury lamp. Photochemical crosslinking of PEO proceeds in the presence of photoinitiators such as benzophenone and acetophenone which act as a hydrogen-abstracting agent. Gel fraction yield exceeds 90%, and the number-average molecular weight between crosslinks determined by equilibrium swelling in chloroform varies from 3,000 to 100,000. The degree of crosslinking can be controlled by changing the irradiation temperature. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 64: 2299–2307, 1997     

Associative properties of perfluorooctyl end‐functionalized polystyrene–poly(ethylene oxide) diblock copolymers

The synthesis of 2,2,3,3‐tetrahydro‐perfluoroundecanoyl end‐functionalized polystyrene–poly(ethylene oxide) block (PS‐block‐PEO‐R_F) copolymers and their matching PS‐block‐PEO diblock copolymers was carried out by sequential anionic polymerization. Viscometry and ¹⁹F NMR studies show that the PS‐block‐PEO copolymers, in contrast to their matching PS‐block‐PEO‐R_F copolymers, exhibit a micellar rather than the associative behavior seen for the latter. However, the presence of an excess of fluorinated acid, used for end‐functionalization, produces a reduction of the associative behavior above the overlap concentration, with the fluorinated acid acting like a surfactant. A competition may also occur between PS—and R_F—mediated micellization. Copyright © 2004 Society of Chemical Industry     

NMR study of poly(vinylpyrrolidone)/poly(ethylene oxide) blends

Development of polymeric blends has become very important for polymer industries because they have been shown to be successful and versatile alternatives to obtain new polymers. In this work binary blends formed by poly(vinylpyrrolidone) (PVP) and poly(ethylene oxide) (PEO) were studied by solution and solid‐state NMR to determine their physical interaction, homogeneity, and compatibility for use as membranes to separate water/alcohol. The NMR results allowed us to acquire information on the microstructure and molecular dynamic behavior of polymer blends. From the NMR solution it was possible to evaluate the microstructure: PVP presented a preferential syndiotactic distribution sequence and PEO presented two regions, one crystalline and the other amorphous. Considering the solid‐state NMR results it was possible to evaluate the molecular dynamics and all binary blends, showing that PEO behaves as a plasticizer; some intermolecular interaction was also observed. An important point was to evaluate the microstructure of the carbonyl PVP using cross polarization/magic‐angle spinning (CP/MAS) and CP/MAS/dipolar decoupling that was not observed before. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 2820–2823, 2002     

Surface immobilization of star‐shaped poly(ethylene oxide) on poly(dimethylsiloxane)

A thin layer of star‐shaped poly(ethylene oxide) (PEO) (starPEO), on the polydimethylsiloxane (PDMS) membrane was prepared by a simple immobilization procedure. Photoreactive molecules were introduced on the surface of the polymeric support to achieve the formation of thin starPEO film from the materials having no functional groups. This novel technique enabled us to immobilize any kind of chemical, especially one that had no functional groups, and readily to control the amount of immobilization. The gas permeation properties of the starPEO‐immobilized PDMS membranes were investigated for pure propane and propylene. The permeance of gases were found to decrease in the starPEO‐immobilized PDMS membranes, although the ideal separation factors for propylene/propane were increased with the loading amount of silver ions, because of the facilitation action of silver ions in the immobilized PEO unit on the PDMS membranes, as propylene carriers. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 2369–2373, 2002     

Syntheses of poly(ethylene oxide) polyurethane ionomers

Sulfonated dimethyl fumarate (SDMF) was prepared with dimethyl fumarate (DMF) and sodium hydrogensulfite (NaHSO₃). Sodium sulfonate side‐chain poly(ethylene oxide) (SPEO) was synthesized by grafting sodium sulfonate onto the chain of PEO with molecular weights of 400, 600, 800, and 1000. SPEO was used subsequently in step‐growth polymerization to give a polyurethane ionomer (SPU). Samples were characterized by element analysis, FTIR, ¹H‐NMR, EDX mapping, X‐ray, gel permeation chromatography, and impedance analysis. The SPUs exhibited an amorphous structure. The maximum conductivity of the SPU was 1.02 × 10⁻⁶ S cm⁻¹ at the room temperature. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 184–188, 2000     

High molecular weight poly( -lactide) and poly(ethylene oxide) blends: thermal characterization and physical properties

The miscibility of high molecular weight poly( -lactide) PLLA with high molecular weight poly(ethylene oxide) PEO was studied by differential scanning calorimetry. All blends containing up to 50 weight% PEO showed single glass transition temperatures. The PLLA and PEO melting temperatures were found to decrease on blending, the equilibrium melting points of PLLA in these blends decreased with increasing PEO fractions. These results suggest the miscibility of PLLA and PEO in the amorphous phase. Mechanical properties of blends with up to 20 weight% PEO were also studied. Changes in mechanical properties were small in blends with less than 10 weight% PEO. At higher PEO concentrations the materials became very flexible, an elongation at break of more than 500% was observed for a blend with 20 weight% PEO. Hydrolytic degradation up to 30 days of the blends showed only a small variation in tensile strength at PEO concentrations less than 15 weight%. As a result of the increased hydrophilicity, however, the blends swelled. Mass loss upon degradation was attributed to partial dissolution of the PEO fraction and to an increased rate of degradation of the PLLA fraction. Significant differences in degradation behaviour between PLLA/PEO blends and (PLLA/PEO/PLLA) triblock-copolymers were observed.     

Miscibility of polystyrene with poly(ethylene oxide) and poly(ethylene glycol)

The intrinsic viscosity of polystyrene–poly(ethylene oxide) (PS–PEO) and PS–poly(ethylene glycol) (PEG) blends have been measured in benzene as a function of blend composition for various molecular weights of PEO and PEG at 303.15 K. The compatibility of polymer pairs in solution were determined on the basis of the interaction parameter term, Δb, and the difference between the experimental and theoretical weight-average intrinsic viscosities of the two polymers, Δ[η]. The theoretical weight-average intrinsic viscosities were calculated by interpolation of the individual intrinsic viscosities of the blend components. The compatibility data based on [η] determined by a single specific viscosity measurement, as a quick method for the determination of the intrinsic viscosity, were compared with that obtained from [η] determined via the Huggins equation. The effect of molecular weights of the blend components and the polymer structure on the extent of compatibility was studied. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 69: 1471–1482, 1998     

Interaction of poly(ethylene oxide) with solvents: 1. Preparation and swelling of a crosslinked poly(ethylene oxide) hydrogel

Crosslinked polymer gels containing over 90 wt% poly(ethylene oxide) have been made and their swelling in a large number of solvents studied. The results confirm previous observations that the interaction of poly(ethylene oxide) with water is quite different from the interaction with most other solvents. Formamide also appears to be anomalous. The crosslinked polymer, swollen with water, shows dramatic syneresis between 0° and 100°C but at 100°C still retains approximately three molecules of water for each ether oxygen.     

Toughening of polypropylene with crystallizable poly(ethylene oxide)

A crystallizable polymer, poly(ethylene oxide) (PEO), was used as new modifier to tailor the toughness of isotactic polypropylene (iPP). An optimum performance was achieved at a medium PEO content of 15 wt% where the toughness was enhanced by 300%, while the strength only decreased slightly. To elucidate the origin of toughening in the iPP/PEO blends, various crystallographic and morphological experiments including X‐ray diffraction, electron microscopy and calorimetry were adopted to explore the dependences of polymorphic composition and crystallized morphology on PEO content. When the PEO content is less than 15 wt%, the dispersed PEO cannot crystallize, and these non‐crystalline PEO microspheres are embedded in both α‐ and β‐form iPP spherulites, which is mainly responsible for the toughening. In contrast, when the PEO content is higher than 15 wt%, the PEO phase becomes crystallizable, and significant phase segregation takes place, resulting in a marked deterioration in mechanical properties. Copyright © 2011 Society of Chemical Industry     

Phototransformation of water-soluble polymers. Part II: photooxidation of poly(ethylene oxide) in aqueous solution

Poly(ethylene oxide) (PEO) was irradiated in aqueous solution under long wavelengths (λ>300 nm, 20 °C) and in presence of oxygen. The photooxidation of PEO was studied by IR spectrophotometry, viscometry and size exclusion chromatography. The formation of the oxidation photoproducts was studied by infrared analysis of films obtained by evaporation of aliquots of irradiated aqueous solutions. The photoproducts were identified by chemical derivatization treatments coupled with infrared measurements. Viscosimetry and SEC analysis showed that photooxidation was leading to a dramatic decrease of the molecular weights. The influence of the pH of the aqueous solutions was also examined. Unexpected results were obtained for the pH 12 solutions, indicating a strong inhibition of the oxidation.

Comparison with the results obtained in the case of PEO irradiated in the solid state showed that no direct transposition of the knowledge concerning the behavior of the solid polymer could be made.     

Crystallization of poly(ethylene oxide) in i-polypropylene–poly(ethylene oxide) blends

A two-stage stable system of isotactic polypropylene–poly(ethylene oxide) blend, in which poly(ethylene oxide) can be permanent either in molten or in crystallized states in the temperature range from 280 to 327 K, was described. The behavior of that blend was explained in terms of fractionated crystallization. A fine dispersion of poly(ethylene oxide) inclusions is required for efficient suppression of crystallization initiated by heterogeneous nuclei. The application of a thin film of polypropylene-poly(ethylene oxide) 9 : 1 blend obtained by quenching for multiuse erasable and rewritable carriers for visible information has been demonstrated. The same sample exhibits different dynamic mechanical properties when poly(ethylene oxide) inclusions are molten or crystallized. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 66: 2047–2057, 1997     

Study on the properties of crosslinking of poly(ethylene oxide) and hydroxyapatite–poly(ethylene oxide) composite

This study covers the crosslinking of poly(ethylene oxide) (PEO) and its composite with calcium hydroxyapatite (HA), their mechanical and swelling properties, and morphology. Sheets of the composites of PEO (two different grades with M_v: 5 × 10⁶ and 2 × 10⁵) and HA and neat PEO were prepared by compression molding. The prepared composite and PEO (0.1‐mm‐thick) sheets were crosslinked with exposure of UV‐irradiation in the presence of a photoinitiator, acetophenone (AP). This simple method for crosslinking, induced by UV‐irradiation in the presence of AP, yielded PEO with gel content up to 90%. Gel content, equilibrium swelling ratio, and mechanical and morphological properties of the low molecular weight polyethylene oxide (LMPEO)–HA crosslinked and uncrosslinked composites were evaluated. Although the inclusion of HA into LMPEO inhibits the extent of crosslinking, the LMPEO–HA composite with 20% HA by weight shows the highest gel content, with appreciable equilibrium swelling and mechanical strength. The growth of HA in simulated body fluid solutions on fractured surfaces of LMPEO and also LMPEO–HA was found to be very favorable within short times. The dimensional stability of these samples was found to be satisfactory after swelling and deposition experiments. The good compatibility between the filler hydroxyapatite and poly(ethylene oxide) makes this composite a useful tissue‐adhesive material. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 488–496, 2003     

Spherulitic crystallization in blends of poly(ethylene oxide) and poly(methyl methacrylate)

The crystallization kinetics of binary blends of poly(ethylene oxide) and poly(methyl methacrylate) were investigated. The isothermal spherulitic growth rates were measured by means of a polarized light microscope. The temperature and composition dependence on the growth rates have been analysed. The temperature range studied was from 44° to 58°C. The introduction of poly(methyl methacrylate) into poly(ethylene oxide) resulted in a reduction of the spherulitic growth rate as the proportion of poly(methyl methacrylate) was increased from zero to 40% by weight. Results have been analysed using the theoretical equations of Boon and Azcue for the growth rate of polymer-diluent mixtures. The experimental results are in good agreement with this equation. The temperature coefficient is negative as is the case in the crystallization of bulk homopolymers.