PEO Component Research Articles

Location of a nanoclay at the interface in an immiscible poly(ε-caprolactone)/poly(ethylene oxide) blend and its effect on the compatibility of the components

Nanocomposites based on 80/20 and 20/80 (w/w) poly(e-caprolactone) (PCL)/poly(ethylene oxide) (PEO) immiscible blends and organophilic layered silicates were prepared with melt extrusion. From transmission electron microscopy analysis, it was observed that the exfoliated silicate platelets were preferentially located at the interface between the two blend phases. When the blend-based nanocomposites were prepared via a two-step process in which the silicates were first premixed with the PEO component or with the PCL component, the silicate layers migrated from the PEO phase or PCL phase to the interface. The rheological behavior of the nanocomposites was also investigated. At low frequencies, the frequency dependence of the storage modulus changed from a liquidlike behavior for the unfilled blend to a solidlike behavior for the nanocomposites, indicating the formation of a network structure as a result of exfoliation. From the scanning electron micrographs, a monotonic decrease of the PEO domain size in the 80/20 PCL/PEO blend was observed as a function of the organophilic clay content. Therefore, a clear emulsifying effect was induced by the organophilic layered silicates in the immiscible PCL/PEO blend. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007

Surface‐treated and multilayered poly(ε‐caprolactone) nanofiber webs exhibiting enhanced hydrophilicity

AbstractTo improve the hydrophilic properties of poly(ε‐caprolactone) (PCL) nano/microfiber webs for tissue engineering scaffolds, PCL webs of various structures were fabricated by electrospinning with single or double nozzles connected to an auxiliary electrode. Surface‐modified and layered PCL fiber webs were made by including water‐soluble poly(ethylene oxide) (PEO) in the PCL electrospinning solution (single‐nozzle method) or by electrospinning of alternating PCL and PEO solutions using two nozzles (double‐nozzle method), respectively. When the PEO component within the resulting webs was removed by dissolution with distilled water, the remnant PCL webs exhibited two distinct structures. Those made by the single‐nozzle method consisted of nanofibers with high surface roughness, whereas those made by the double‐nozzle method consisted of stacked layers of PCL nanofibers. Both types of structured PCL web showed improved hydrophilicity characteristics compared with those of nanofiber webs generated from a pure PCL solution using a typical electrospinning process. Cell culturing and scanning electron microscopy showed that the interactions between human dermal fibroblasts and the structured PCL scaffolds were very favorable. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 2038–2045, 2007

Application of Nanotechnology in Cancer Research: Review of Progress in the National Cancer Institute's Alliance for Nanotechnology

Application of Nanotechnology in Cancer Research: Review of Progress in the National Cancer Institute's Alliance for Nanotechnology

Enhanced ionic conductivity in PEO-LiClO4 hybrid electrolytes by structural modification

Poly(ethylene oxide)-LiClO4-TiO2 organic-inorganic hybrids were synthesized for Li-polymer battery electrolytes using sol-gel processing. The hybrids containing TiO2 component showed the uniform film formation and also increased ionic conductivity. The hybrid films containing 10 wt% TiO2 showed the smooth surface morphologies and also the highest ionic conductivity. The molecular-level hybrid formation between PEO and TiO2 components was identified using FTIR analyses. The hybrids containing TiO2-Al2O3 mixtures showed the enhanced ionic conductivity compared to those containing only TiO2 most probably due to the Lewis acidic group formation at the surface of Al2O3 components. The PEO-LiClO4-TiO2-Al2O3 hybrids showed high stability both in ionic conductivity and crystallinity. By the sol-gel processing two inorganic components were successfully introduced in the PEO matrix and high-performance solid electrolytes were achieved.

Dynamics of poly(ethylene oxide) in a blend with poly(methyl methacrylate): A quasielastic neutron scattering and molecular dynamics simulations study

In this paper, we have addressed the question of the dynamic miscibility in a blend characterized by very different glass-transition temperatures, Tg, for the components: poly(ethylene oxide) and poly(methyl methacrylate) (PEO/PMMA). The combination of quasielastic neutron scattering with isotopic labeling and fully atomistic molecular dynamics simulations has allowed us to selectively investigate the dynamics of the two components in the picosecond-10 nanoseconds scale at temperatures close and above the Tg of the blend. The main focus was on the PEO component, i.e., that of the lowest Tg, but first we have characterized the dynamics of the other component in the blend and of the pure PEO homopolymer as reference. In the region investigated, the dynamics of PMMA in the blend is strongly affected by the alpha-methyl rotation; an additional process detected in the experimental window 65 K above the blend-Tg can be identified as the merged alphabeta process of this component that shows strong deviations from Gaussian behavior. On the other hand, pure PEO displays entropy driven dynamics up to very large momentum transfers. Such kind of motion seems to freeze when the PEO chains are in the blend. There, we have directly observed a very heterogeneous and moreover confined dynamics for the PEO component. The presence of the hardly moving PMMA matrix leads to the creation of little pockets of mobility where PEO can move. The characteristic size of such confined islands of mobility might be estimated to be of approximately 1 nm. These findings are corroborated by the simulation study, which has been an essential support and guide in our data analysis procedure.

Miscible blend dynamics and the length scale of local compositions

AbstractWe consider the influence of a local, or effective, composition on dynamics in the miscible polymer blend PEO/PMMA. Quasielastic neutron scattering in combination with deuterium labeling is employed to determine characteristic relaxation times of the PEO component over spatial scales from 3 to 10 Å. Information about the distribution of relaxation times is obtained indirectly from the stretching parameters in a stretched exponential fit. We examine the behavior of these parameters with spatial scale and temperature, finding that their variation supports a distribution of PEO mobility in the blend which is far wider than pure PEO and narrows with decreasing temperature for small spatial scales. This is linked to the concept of local compositions defined over varying spatial scales, and indicates that the concept of a local composition, linked to PEO dynamics, is important in this system. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 2914–2923, 2005

Effect of aging on fractional crystallization of poly(ethylene oxide) component in poly(ethylene oxide)/poly(3‐hydroxybutyrate) blends

AbstractThe effect of aging on the fractional crystallization of the poly(ethylene oxide) (PEO) component in the PEO/poly(3‐hydroxybutyrate) (PHB) blend has been investigated. The partial miscibility of the PEO/PHB blends with high PEO molecular weight (Mv = 2.0 × 105 g/mol) was confirmed by differential scanning calorimetry (DSC) and dynamic mechanical thermal analysis. The fractional crystallization behavior of the PEO component in the PEO/PHB blends with low PEO content (not more than 30 wt% of PEO), before and after aging under vacuum at 25 °C for 6 months, were compared by DSC, fourier transform infrared microscopic spectroscopy, small angle X‐ray diffraction, and scanning electron microscopy. It was confirmed that nearly all the PEO components remain trapped within interlamellar regions of PHB for the PEO/PHB blends before aging. Under this condition, the crystallization of PEO is basically induced by much less active heterogeneities or homogeneous nucleation at high supercoolings. While, after the same PEO/PHB samples were stored at 25 °C in vacuum for 6 months, a part of the PEO component was expelled from the interlamellar region of PHB. Under this condition, the expelled PEO forms many separate domains with bigger size and crystallizes at low supercoolings by active heterogeneous nucleation, whereas the crystallization of PEO in the interlamellar region is still mainly induced by less active heterogeneities or homogeneous nucleation at extreme supercoolings. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 2665–2676, 2005

Structural Analysis of Hybrid Titania-Based Mesostructured Composites

High-optical-quality titania-based mesostructured films with cubic or 2D-hexagonal symmetry were fabricated by combining trifluoroacetate (TFA)-modified titanium precursors with amphiphilic triblock poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) (PEO-PPO-PEO) copolymers. The distribution, dynamics, and local environments of the TFA-modified titania, PEO, and PPO components of the hybrid were investigated. IR/Raman spectroscopy, in situ small-angle X-ray scattering, and transmission electron microscopy studies indicate that TFA coordinates the titanium center and forms a stable complex that is subsequently organized by the block copolymer species into ordered mesostructures. Solid-state NMR (19)F-->(1)H cross-polarization, (13)C{(1)H} two-dimensional heteronuclear correlation, and (1)H relaxation techniques were used to determine that PEO is predominantly incorporated within the TFA-modified titania, and that PPO environments encompass both microphase separated regions and interfacial regions composed of mixed PPO and TFA-modified titania. NMR (19)F multiple-quantum spin counting measurements suggest that -CF(3) groups of the trifluoroacetate ligands do not form clusters but instead randomly distribute within the inorganic component of the hybrid.

Nanocomposite polymer electrolyte comprising PEO/LiClO 4 and solid super acid: effect of sulphated-zirconia on the crystallization kinetics of PEO

A novel PEO-based nanocomposite polymer electrolyte is prepared by using solid super acid sulphated-zirconia ( SO 4 2 − - ZrO 2 , SZ) as the filler. Polarized optical microscopy (POM) and differential scanning calorimeter (DSC) results show that part of SZ particles may act as the nucleus of PEO spherulites and thus increase the amount of PEO spherulites. On the other hand, other SZ particles, which do not act as the nucleus, can restrain the recrystallization tendency of PEO chains through Lewis acid–base interaction and hence decrease the growth speed of PEO spherulites. As a result, the PEO component in PEO–LiClO 4–SZ can maintain a high amorphous state for a long time. The room temperature ionic conductivity of PEO–LiClO 4–SZ is relative high and stable compared with pristine PEO–LiClO 4, indicating that it is promising for all solid-state rechargeable lithium ion batteries.

Preparation and Properties of Crosslinked Polyurethane Containing Hydrophilic PEO Component for Biomaterials

A series of multiblock polyurethanes containing various poly(ethylene oxide) (PEO) contents (0-80 wt%) were prepared from hexamethylene diisocyanate (HDI)/ PEO / poly(tetramethylene oxide) (PTMO)/ polybutadiene diol (PBD)/ 1,4-butanediol (BD) and used as modifying additives (30 wt%) to improve the properties of biomedical grade PelletheneÒ. A hydrophilic PEO component was introduced by the addition of PEO-containing polyurethanes and dicumyl peroxide (DCP) as the crosslinking agents in a PelletheneÒ matrix. As the PEO content (PEO block length) increased, the hydrogen-bonding fraction of the crosslinked polyurethane also increased, indicating an increase in the phase separation with an increase in the PEO content in the crosslinked polyurethane. Using electron spectroscopy for a chemical analysis, the ratio of ether carbon to alkyl carbon in the crosslinked polyurethane film increased remarkably with an increase, in the PEO content. Meanwhile, the water contact angle of the crosslinked polyurethane film surfaces decreased with increasing PEO content. The water absorption and mechanical properties of the crosslinked polyurethane films increased with increasing and the platelet adhesion on the crosslinked polyurethane film surfaces decreased significantly. Accordingly, these results suggest that the crosslinked polyurethane containing a hydrophilic PEO component may be more effective for a biomaterial application that is in direct contact with blood.

AB Block-copolymers poly(oxyethylene)-blockpoly( dicyclohexyl itaconate): temperature dependence of the morphology

Abstract The paper deals with AB block-copolymers poly(oxyethylene)-blockpoly( dicyclohexyl itaconate) (POE/PDCHI) containing 2000 and 5000 g/mol of the flexible POE. The study aims at revealing the thermal effect on the copolymer morphology in the 20 - 200°C range. Optical microscopy investigations were performed. The results confirm our previous X-ray studies. A liquid crystalline state is observed in the 90 - 180°C range. It is characterized by birefringence and is determined by the chair-chair conformation, a dominating structure of the cyclohexyl rings. A condis-crystal state is observed at cooling in the interval 90°C to room temperature. It is characterised by a variety of cyclohexyl conformations and, therefore, by a lack of birefringence. The PEO component in the copolymer starts crystallising into small local spherulites at about room temperature. The results obtained allow the conclusion that the presence of PDCHI is a determining factor for the mesomorphic state of the copolymers discussed.

Interactions of Charged Porphyrins with Nonionic Triblock Copolymer Hosts in Aqueous Solutions

The extent and locus of solubilization of guest and self-assembling surfactant host molecules in aqueous solutions are influenced by a variety of hydrophobic and hydrophilic interactions, as well as by more specific interactions between the various species present. By using a combination of two-dimensional heteronuclear 13C[1H] NMR correlation experiments with pulsed-gradient NMR diffusion and proton cross-relaxation measurements, the locations and distributions of porphyrin guest molecules have been established unambiguously with respect to the hydrophobic and hydrophilic moieties of a triblock copolymer species in solution. The interactions of tetra(4-sulfonatophenyl)porphyrin with the poly(propylene oxide) (PPO) and the poly(ethylene oxide) (PEO) segments of amphiphilic PEO-PPO-PEO triblock copolymer species have been measured as functions of solution conditions, including temperature and pH. The porphyrin/PEO-PPO-PEO interactions are established to be selective and adjustable according to the different temperature-dependent hydrophilicities or hydrophobicities of the PEO and PPO triblock copolymer components. Furthermore, such interactions influence the self-assembly properties of the block-copolymer amphiphiles in solution by stabilizing molecular porphyrin/PEO-PPO-PEO complexes well above the critical micellization temperature of the triblock copolymer species under otherwise identical conditions.

Effects of Crystallization Condition of Poly(butylene succinate) Component on the Crystallization of Poly(ethylene oxide) Component in Their Miscible Blends

The crystallization behavior of the poly(ethylene oxide) (PEO) component in poly(butylene succinate) (PBS)/PEO blends with the middle PEO content was investigated as a function of isothermal crystallization temperature of the PBS component (TIC,PBS) using differential scanning calorimetry (DSC). It is found that the crystallization behavior of the PEO component in these blends is significantly affected by TIC,PBS. Small-angle X-ray diffraction (SAXS) measurements were performed to explore the origin of the TIC,PBS dependence of crystallization of PEO component. On the basis of the SAXS measurements and the results of our previous work [Macromolecules 2004, 37, 3337−3345], it is suggested that TIC,PBS controls the location distribution of the PEO component in the blends after the crystallization of the PBS component and thus significantly affects the crystallization behavior of PEO.

Nanoscale-Confined and Fractional Crystallization of Poly(ethylene oxide) in the Interlamellar Region of Poly(butylene succinate)

The miscibility, morphology, and crystallization behavior of the blend of poly(ethylene oxide) (PEO) and poly(butylene succinate) (PBS) have been investigated using differential scanning calorimetry, high-resolution solid-state 13C NMR spectroscopy, and wide- and small-angle X-ray diffraction. PEO and PBS are found to be miscible in the amorphous phase, and fractional crystallization of PEO component is observed in the blends with low PEO content. Also, it is revealed that the PEO component in the blend with less than 20 wt % PEO content is completely included in the region between PBS lamellae. On the basis of these results, the crystallization behavior of the PEO component has been analyzed and the origin of fractional crystallization has been explored. The blend system of PBS and PEO investigated here is the first instance of confined and fractional crystallization occurring in a miscible blend.

Properties of crosslinked blends of pellethene and multiblock polyurethane containing poly(ethylene oxide) for biomaterials

AbstractA series of multiblock polyurethanes, containing various poly(ethylene oxide) (PEO; number‐average molecular weight = 400–3400) contents (0–80 wt %) and prepared from hexamethylene diisocyanate/PEO/poly(dimethylsiloxane) diol/polybutadiene diol/1,4‐butanediol, were used as modifying additives (30 wt %) to improve the properties of biomedical‐grade Pellethene. Different molecular weights of PEO were used to keep poly(ethylene glycol) at a fixed molar content, if possible, although the PEO content, related to the PEO block length in the multiblock polyurethanes, was varied from 0 to 80 wt %. The hydrophilic PEO component was introduced through the addition of PEO‐containing polyurethanes and dicumyl peroxide as a crosslinking agent in a Pellethene matrix. As the PEO content (PEO block length) increased, the hydrogen‐bonding fraction of the crosslinked Pellethene/multiblock polyurethane blends increased, and this indicated an increase in the phase separation with an increase in the PEO content in the crosslinked Pellethene/multiblock polyurethane blends. According to electron spectroscopy for chemical analysis, the ratio of ether carbon to alkyl carbon in the crosslinked Pellethene/multiblock polyurethane blends increased remarkably with increasing PEO content. The water contact angle of the crosslinked Pellethene/multiblock polyurethane blend film surfaces decreased with increasing PEO content. The water absorption and mechanical properties (tensile modulus, strength, and elongation at break) of the crosslinked Pellethene/multiblock polyurethane blend films increased with increasing PEO content. The platelet adhesion on the crosslinked Pellethene/multiblock polyurethane blend film surfaces decreased significantly with increasing PEO content. These results suggest that crosslinked Pellethene/multiblock polyurethane blends containing the hydrophilic component PEO may have potential for biomaterials that come into direct contact with blood. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 2348–2357, 2004

Influence of 1-Pentanol on the Micellization of Poly(ethylene oxide)−Poly(propylene oxide)−Poly(ethylene oxide) Block Copolymers in Aqueous Solutions

The critical micellization temperature (CMT) of poly(ethylene oxide)−poly(propylene oxide)−poly(ethylene oxide) (PEO−PPO−PEO) block copolymers in water has been determined by using the temperature-dependent fluorescence intensity of pyrene. The CMT of Pluronic polymers in aqueous solutions is decreased by the addition of 1-pentanol. The thermodynamic parameters of micellization are obtained from the temperature derivatives of the ln(XCMC) (CMC = critical micellization concentration) values. The standard enthalpy and entropy of micellization for Pluronic polymers in water are increased with an increase of the 1-pentanol content. The more PEO component in the Pluronic polymer, the higher the changed values of micellization enthalpy and entropy. The solubilization of 1-pentanol in the micelles was used to explain the relationship between the changed values of thermodynamic parameters of micellization and the composition of Pluronic polymers, in which the water in the micellar cores is replaced by the solubilized 1-pentanol. The I1/I3 ratio of pyrene in aqueous Pluronic polymer solutions at temperatures below the CMT is decreased with an increase of the 1-pentanol concentration. A less polar microenvironment will be formed in the regions of unexpanded PPO coils when more 1-pentanol is added to the aqueous Pluronic polymer solution. The decrease of PPO solubility will result in the shift of CMT toward lower temperature.

Dynamic rheological analysis of a miscible blend showing strong interactions

The rheological behavior of miscible blends was studied through oscillatory shear measurements. Two miscible blends were selected to compare with athermal blending cases, i.e. the hydrogen bonding poly(4-vinyl phenol)/poly(ethylene oxide) (PVPh/PEO) blend and the weakly interacting polystyrene/poly(2,6-dimethyl-1,4-phenylene oxide) (PS/PPO) blend. The homopolymers and the blends were characterized over a wide experimental window using the time–temperature superposition principle.The horizontal shift factor, aT, does not vary appreciably with composition for PS/PPO, whereas a strong compositional dependence is observed for the PVPh/PEO blends. Additions of up to 30wt% of PEO to PVPh produce only minor changes in the value of rubber plateau modulus (GN0), while GN0 increases steadily after this concentration. The GN0 values follow athermal blending models [J. Polym. Sci., Part B: Polym. Phys. 25 (1987) 2511; J. Polym. Sci., Part B: Polym. Phys. 26 (1988) 2329] in the case of PS/PPO but not of PVPh/PEO. Values of η0b for PVPh/PEO blends were estimated from weighed relaxation spectra. The three measured parameters, aT, GN0 and η0 show a turning point around 20–30wt% of PEO, which corresponds to a 41–54mol% of PEO, in correlation with the previously reported observation of a maximum in the deformation-induced uniaxial orientation behavior of PEO component near this composition [Macromolecules 32 (1999) 8509].

A solid-state 13C NMR study on phase heterogeneity in the miscible blend of amorphous poly(benzyl methacrylate) with semicrystalline poly(ethylene oxide)

The rotating-frame spin–lattice relaxation time for protons, T 1 ρ ( 1H), was measured indirectly from 13C CP/MAS/DD NMR to probe possible molecular scales of heterogeneity in the miscible poly(benzyl methacrylate) (PBzMA)/poly(ethylene oxide) (PEO) blend over the whole composition range. According to the NMR results, only one phase was observed for the blends in which the PEO component is less than 16% (w/w). This miscible amorphous phase with PBzMA and PEO chains was mixed at the molecular level. Three phases were detected for the blends with PEO component >16%, containing one miscible homogenous PBzMA-rich phase, one constrained PEO phase and one crystalline PEO phase. The PEO component asymptotically increases in the miscible homogenous PBzMA-rich phase as the PEO composition increases. NMR analysis helped resolve the complex phase domains in the PBzMA/PEO blend that is composed of an amorphous mixture of PBzMA/PEO and crystalline PEO spherulite regions. The intra- and inter-lamellar domains in the PEO spherulites are influenced and complicated by the surrounding amorphous PBzMA/PEO mixture with varying composition.

Engineered collagen–PEO nanofibers and fabrics

Type I collagen-PEO fibers and non-woven fiber networks were produced by the electrospinning of a weak acid solution of purified collagen at ambient temperature and pressure. As determined by high-resolution SEM and TEM, fiber morphology was influenced by solution viscosity, conductivity, and flow rate. Uniform fibers with a diameter range of 100-150 nm were produced from a 2-wt% solution of collagen-PEO at a flow rate of 100 μl min-1. Ultimate tensile strength and elastic modulus of the resulting non-woven fabrics was dependent upon the chosen weight ratio of the collagen-PEO blend. 1H NMR dipolar magnetization transfer analysis suggested that the superior mechanical properties, observed for collagen-PEO blends of weight ratio 1 : 1, were due to the maximization of intermolecular interactions between the PEO and collagen components. The process outlined herein provides a convenient, non-toxic, non-denaturing approach for the generation collagen-containing nanofibers and non-woven fabrics that have potential application in wound healing, tissue engineering, and as hemostatic agents.

Ionomeric blends of poly(ethylene oxide) with poly(styrene-co-maleic anhydride) ionomer: Miscibility, crystallization, and melting behavior

The miscibility and crystallization behavior of poly(ethylene oxide) (PEO) and poly(styrene-co-maleic anhydride) ionomer (SMAI) blends were studied by the dynamic mechanical analysis (DMA) and differential scanning calorimetry (DSC). This study has demonstrated that the presence of ion–dipole interactions enhances the miscibility of otherwise immiscible polymers in the PEO and high molecular weight poly(styrene-co-maleic anhydride) (SMA). The effect of ion–dipole interactions on enhancing miscibility is confirmed by the presence of a single glass transition temperature (Tg) and a depression of the equilibrium melting temperature of the PEO component. The equilibrium melting temperature of PEO in the blends are obtained using Hoffman-Weeks plots. The interaction energy density, β, is calculated from these data using the Nishi-Wang equation. The results suggest that PEO and SMAI blends are thermodynamically miscible in the melt. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 1–7, 2000