Polyethylene Oxide Polymer Research Articles

Coarse-Grained Force Field for Polyethylene Oxide and Polyethylene Glycol Aqueous Solutions Based on a Polarizable Water Model

A new, accurate and transferable coarse-grained (CG) force field (FF) for polyethylene oxide (PEO) and polyethylene glycol (PEG) aqueous solutions based on a polarizable CG water (PCGW) model is developed in this work. A PCGW bead, which represents four water molecules, is modeled as two charged dummy particles connected by two constrained bonds to a central neutral particle; a PEO or PEG oligomer is modeled as a chain with repeated middle beads (PEOM) representing diether groups and two terminal beads (PEOT or PEGT) of a different type compared to PEOM. To describe nonbonded van der Waals interactions, a piecewise Morse potential with four tunable parameters is used. The force parameters are automatically and rigorously optimized by a meta-multilinear interpolation parameterization (meta-MIP) algorithm to simultaneously match multiple thermodynamic properties, including the density, heat of vaporization, vapor-liquid interfacial tension, and solvation free energy of the pure PEO or PEG oligomer bulk system as well as the mixing density and hydration free energy of the oligomer/water binary mixture. Additional thermodynamic and structural properties for longer PEO and PEG polymer aqueous solutions, such as the self-diffusion coefficient, radius of gyration, and end-to-end distance, are predicted to test the accuracy and transferability of this new CG FF. Based on the PCGW model, the presented FF optimization algorithm and strategy can be extended to more complex polyelectrolytes and surfactants.

Design and Optimization of a Polyethylene Oxide-Based Matrix Tablet of Metoprolol Succinate Using Design Expert Software

Hypertension is a common lifestyle disorder, the prevalence of which advances with age. In the case of antihypertensive therapy, patient compliance is hampered, especially in geriatric patients, if the dose is b.i.d or more, as it is difficult for the patient to remember and take medicine at a scheduled time. The present study involves the fabrication of a sustained-release matrixdesigned tablet using a combination of polyethylene oxide (PEO) polymers and metoprolol succinate as the model drug. The tablet is optimized and evaluated for its in-vitro release using the Design expert software. Polyethylene oxide is a non-ionic hydrophilic polymer which is directly compressible. Polyox WSR 301 and 303 grades have been used in the study to get the desired sustained release of 12 h. The formulations were analysed for various pre-compression and post-compression characteristics. The polymers Polyox WSR 301 and 303 influence drug release are measured using a 32 factorial design where the concentration of drug released at various time points has been analysed statistically as a response. Response surface plots demonstrate and depict the effect of the variables, thus aiding in optimization. All the formulated batches exhibited acceptable pre and post-compression characteristics. The optimized formulation M05 showed a sustained drug release up to a 12 h period. Thus polyethylene oxide can be used as an excellent sustained-release matrix polymer due to its ability to gel and prolong drug release from a matrix. Due to their molecular weight, a combination of two grades of polyethylene oxide helps reinforce the drug release.

A room temperature rechargeable Li2O-based lithium-air battery enabled by a solid electrolyte.

A lithium-air battery based on lithium oxide (Li2O) formation can theoretically deliver an energy density that is comparable to that of gasoline. Lithium oxide formation involves a four-electron reaction that is more difficult to achieve than the one- and two-electron reaction processes that result in lithium superoxide (LiO2) and lithium peroxide (Li2O2), respectively. By using a composite polymer electrolyte based on Li10GeP2S12 nanoparticles embedded in a modified polyethylene oxide polymer matrix, we found that Li2O is the main product in a room temperature solid-state lithium-air battery. The battery is rechargeable for 1000 cycles with a low polarization gap and can operate at high rates. The four-electron reaction is enabled by a mixed ion-electron-conducting discharge product and its interface with air.

Variation in the Optical Properties of PEO-Based Composites via a Green Metal Complex: Macroscopic Measurements to Explain Microscopic Quantum Transport from the Valence Band to the Conduction Band.

In this study, a green chemistry method was used to synthesize polymer composites based on polyethylene oxide (PEO). The method of the remediation of metal complexes used in this study is an environmentally friendly procedure with a low cost. Zinc metal ion (Zn2+)-polyphenol (PPHNL) complexes were synthesized for two minutes via the combination of a black tea leaf (BTL) extract solution with dissolved Zn-acetate. Then, UV-Vis and FTIR were carried out for the Zn-PPHNL complexes in a liquid and solid. The FTIR spectra show that BTLs contain sufficient functional groups (O-H, C-H, C=O, C=C, C-O, C-N, and N-H), PPHNL, and conjugated double bonds to produce metal complexes by capturing the cations of Zn-acetate salt. Moreover, FTIR of the BTL and Zn-PPHNL complexes approves the formation of the Zn-PPHNL complex over the wide variation in the intensity of bands. The UV absorption spectra of BTL and Zn-PPHNL indicate complex formation among tea PPHNL and Zn cations, which enhances the absorption spectra of the Zn-PPHNL to 0.1 compared to the figure of 0.01 associated with the extracted tea solution. According to an XRD analysis, an amorphous Zn-PPHNL complex was created when Zn2+ ions and PPHNL interacted. Additionally, XRD shows that the structure of the PEO composite becomes a more amorphous structure as the concentration of Zn-PPHNL increases. Furthermore, morphological study via an optical microscope (OM) shows that by increasing the concentration of Zn-PPHNL in a PEO polymer composite the size of the spherulites ascribed to the crystalline phase dramatically decreases. The optical properties of PEO: Zn-PPHNL films, via UV-Vis spectroscopy, were rigorously studied. The Eg is calculated by examining the dielectric loss, which is reduced from 5.5 eV to 0.6 eV by increasing the concentration of Zn-PPHNL in the PEO samples. In addition, Tauc's form was used to specify the category of electronic transitions in the PEO: Zn-PPHNL films. The impact of crystalline structure and morphology on electronic transition types was discussed. Macroscopic measurable parameters, such as the refractive index and extinction coefficient, were used to determine optical dielectric loss. Fundamental optical dielectric functions were used to determine some key parameters. From the viewpoint of quantum transport, electron transitions were discussed. The merit of this work is that microscopic processes related to electron transition from the VB to the CB can be interpreted interms of measurable macroscopic quantities.

Synthesis and Characterization of Rare Earth Doped Ferrite / Polyethylene Oxide Nanocomposites

Nano-sized Li0.5Ni0.48Tb0.02Dy0.1Fe1.9O4 spinel ferrite nanoparticles were synthesized employing the micro-emulsion synthesis method. Polyethylene oxide was prepared through in-situ polymerization route. The ferrite-polymer nanocomposites have been synthesized by combining Li0.5Ni0.48Tb0.02Dy0.1Fe1.9O4 ferrite with polyethylene oxide polymer. Spectral, structural, morphological, and dielectric properties of the prepared nano-ferrite powders as well as nanocomposites were investigated by “X-ray diffraction analysis” (XRD), “scanning electron microscopy” (SEM), “Fourier transform infrared spectroscopy” (FTIR) and dielectric measurements. XRD analysis confirmed the synthesis of single-phase spinel structure only. The dielectric parameter was augmented with an increase of ferrite amount. FTIR spectra confirmed the existence of interactions between polyethylene oxide and ferrite particles. SEM study revealed that the nanocomposites comprised core/shell structure and inhomogeneous distribution of grain size. The dielectric parameters such as “real part of dielectric constant” (?), “imaginary part of dielectric constant” (?"), “tan loss”, “AC conductivity” and “quality factor” were investigated in the required range of frequency; that is, 1 MHz – 3 GHz. The peaking behavior has been observed for real (??) and “imaginary (???) parts of dielectric constant” and “dielectric loss” (tan?). “The peaking behavior” was detected beyond 1.5 GHz. A decrease in “the dielectric constants” and “dielectric loss” was found to with the increasing frequency. Dielectric parameters have been well elucidated by explaining “Debye-type relaxation model” in agreement with two layer “Koop's phenomenological theory”. The present investigated samples might have potential applications in high frequency.

Determining critical overlap concentration of polyethylene oxide to support excipient safety assessment of opioid products

Intravenous administration of abuse-deterrent opioid products poses high safety risks, in part due to the presence of high molecular weight polymeric excipients. Previous in vivo studies in animal models have shown that the higher molecular weight (Mw) polymeric excipients like polyethylene oxide (PEO) were directly linked to such adverse responses as intravenous hemolysis and kidney damage. PEO polymers have been widely used in abuse-deterrent formulations (ADF) of opioid products, adding to concerns over the general safety of the opioid category due to the unknown safety risk from abuse via unintended routes. The current study focused on the determination of the critical overlap concentration (c*) at various PEO molecular weights to aid in explaining differences in observed adverse responses from previous animal studies on the intravenous administration of PEO solutions. Adverse in vivo responses may be related to the viscoelastic regime of the polymer solution, which depends not only on Mw but also on concentration. Having a localized polymer concentration in the blood above the c*, i.e., the transition from the dilute to semi-dilute entangled viscoelastic regime, may influence the flow behavior and interactions of cells in the blood. The relationship of c* to this combination of physical, chemical, and rheological effects is a possible driving force behind adverse in vivo responses.

Stability of Abuse-deterrent properties of PEO-based Abuse-deterrent formulation

Abuse of opioid drug products is a national health crisis in the US. To deter abuse, a number of drug products with abuse-deterrent (AD) properties have been approved by the US Food and Drug Administration (FDA). For abuse deterrence, it is critical to maintain the AD properties during the product shelf life. However, no information on the stability of AD properties during product shelf life is publicly available. In this study, stability of AD properties of surrogate AD formulation (ADF) of opioid active pharmaceutical ingredients (APIs) were studied. Surrogate extended release (ER) AD tablets were prepared by direct compression using Diltiazem HCl (model drug), polyethylene oxide (PEO WSR 301) polymer and magnesium stearate followed by curing at 70 °C for 30 mins. The stability studies were conducted at 25 °C/60 % RH and 40 °C/75 % RH storage conditions for 12 months (M) and 6 months (M), respectively. In vitro characterization and evaluation of AD properties of tablets were performed. As anticipated, the curing process increased the crushing strength of the tablets. However, the tablets could still be manipulated and compromised leading to an enhancement in the amount of drug extracted in solvents (e.g., water, alcohol), regardless of extraction temperature as well as tablet storage condition and time. Furthermore, the granule particle size as well as viscosity in water of manipulated samples were found to be lower for tablets stored at 25 °C/60 % RH or 40 °C/75 % RH for 12 M or 3 M/6M, respectively. The changes in AD properties eased the syringeability of hydrated samples and ultimately led to the withdrawal of higher amounts of drug into the syringe, thereby, impacting the abuse deterrence potential of the formulation by an IV route. These data demonstrated that the stability of AD properties (i.e., granule particle size, viscosity and syringeability-injectability) of PEO-based tablets was dependent on the storage condition. In conclusion, the design of AD formulation and setting of product quality profile should take into consideration the stability of AD properties during the product shelf life.

Anisotropic flocculation in shear thickening colloid-polymer suspension via simultaneous observation of rheology and X-ray scattering

A shear thickening fluid, showing a significant increase in viscosity under shear stress, is a promising material for shock absorption applications. Colloidal dispersions of silica nanoparticles and polyethylene oxide polymers with large molecular weights also exhibit a shear thickening phenomenon, which is manifested by a transformation from liquid to gel, called shake-gel. To understand the gelation mechanism, small-angle X-ray scattering (SAXS) and ultra-small-angle X-ray scattering (USAXS) were performed with an X-ray transmission cell, which was used as a Couette cell in a rheometer. This setup enables simultaneous rheological measurements with SAXS and USAXS, providing real-time observation of the change from liquid to gel. An anisotropic increase of the scattering spectra indicated the formation of aligned floc structures. This result implies that a polymer chain recombined the network and transformed into the large flocs aligned in the flow direction. Additionally, the shifted peaks from the silica cluster indicated that the aligned flocs were compressed by the shear stress. The present work paves the way for the advanced design of shake-gel materials.

Highly conducting ionic liquid doped polymer electrolyte for energy storage applications

The main aim of the present work is to optimize highly conducting solid polymer electrolyte by doping of ionic liquid in Poly-ethylene oxide (PEO) polymer complexed Sodium Iodide (NaI) matrix. Solution casting method has been used to synthesis solid polymer electrolyte. Electrical, thermal, structural, and optical studies confirm the homogenous complexation of polymer electrolyte with ionic liquid. Furthermore, the electric double-layer capacitors (EDLCs) device and Dye Sensitized Solar Cell (DSSC) has been developed using high conducting ionic liquid (IL) polymer electrolyte with maximum conductivity, demonstrating that ionic liquids have a potential possibility to choose as electrolyte in developed energy devices.

Incorporating 2D γ-Al2O3 nanosheets into the flexible PEO-based solid electrolyte for lithium metal batteries

Solid polymer electrolytes using polyethylene oxide (PEO) are promising for boosting the safety of lithium metal batteries (LMBs), but suffer from low ionic conductivity due to high crystallinity and poor segment motion of PEO. Adding plasticizers like succinonitrile (SN) is one of the solutions to improve the ionic conductivity of PEO, but it sacrifices the cycle performances of LMBs. In addition, the ability to conduct lithium ions of PEO-SN matrixes is yet to be improved. Herein, two-dimensional γ-Al2O3 nanosheets are first introduced into the PEO-SN matrix to facilitate the long-range migration of lithium ions and improve the electrochemical properties of PEO-SN matrix, realizing the new design of traditional materials. The mechanism between γ-Al2O3 nanosheets and the polymer matrix is discussed. The addition of γ-Al2O3 nanosheets improves the ionic conductivities and cycle performances of PEO-LiTFSI-SN (PLS) electrolytes. In specific, the ionic conductivity at 25 °C of the PEO-LiTFSI-SN-Al2O3 nanosheet (PLS-A) electrolyte is up to 2.02 × 10−4 S cm−1. Meanwhile, the electrochemical properties of Li/PLS-A/LiFePO4 are tested, with a low overpotential change of 0.06 V, coulombic efficiency above 99.6%, and capacity retention of 95% at 0.5C and 60 °C after 50 cycles. The solid electrolyte system provides a feasible strategy for the application of 2D nanofillers in PEO polymer electrolytes.

Conductivity Study on Proton-Conducting Nanocomposite Plasticized Polymer Electrolytes: A Review

Abstract:This paper reviews proton-conducting polymer electrolytes comprising different polymers, salts, and acids. The ionic conductivity of plasticized polymer electrolytes has been found to increase with the addition of plasticizers due to the dissociation of ion aggregates or undissociated salt/acid present in the electrolytes, i.e., σ (plasticized polymer electrolytes) > σ (unplasticized polymer electrolytes). Proton-conducting nonaqueous nanocomposite plasticized polymer electrolytes containing poly(vinylidene fluoride-co-hexafluoropropylene) (PVdF-HFP), polymethylmethacrylate (PMMA), polyethylene oxide (PEO) polymers; different ammonium salts and acids as proton conductors; ethylene carbonate (EC), propylene carbonate (PC), dimethylformamide (DMF), dimethylacetamide (DMA), dimethyl carbonate (DMC), diethyl carbonate (DEC) as plasticizers; fumed silica and alumina as nano-fillers have been discussed in details. Conductivity studies (effect of salt/acid, effect of plasticizers, effect of nano-fillers, and effect of temperature), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and differential scanning calorimetry/thermal gravimetric analysis (DSC/TGA) studies for these electrolytes have been discussed and reported in the paper. Nanocomposite plasticized polymer electrolytes showed high ionic conductivity (in the order of 10-1 to 10-2 S/cm) at room temperature along with good thermal and mechanical stability due to the simultaneous addition of both plasticizers and nano-fillers. These nanocomposite polymer electrolytes are the best candidates for use in various electrochemical devices like solid-state batteries, fuel cells, supercapacitors, sensors, separators, and other electrochromic devices.

Oily phase migration control at the interface of hydrophobic/hydrophilic polymer blends

The introduction of oily liquid in polymer blends by extrusion remains a challenge as it is limited by the affinity of the oil with the different phases of the blend. In this work, we investigate the influence of the addition of oils in a hydrophobic polyethylene-co-octene (PE)/hydrophilic polyethylene oxide (PEO) polymer blend prepared in the molten state. Four oils with different viscosities and polarities were selected: hazelnut oil, castor oil and two silicon oils. Using surface tension measurements and microscopy observation of the morphology, we show that the phase in which the oil stays is mainly driven by surface tension; however, it appears that viscosity influences the mobility of the oil through the phases. The application of the spreading coefficient theory to this solid-liquid system is new and brings a better understanding of the phenomenon. By substituting PE by polycaprolactone (PCL), we also show that the modification of the surface tension between matrix polymers without significantly changing the viscosity and elasticity ratios helps control the localization of the oils at the interface. These results are a first step towards in-situ encapsulation of lipophilic additives in immiscible polymer blends.

Laser beam power attenuation characteristics for pure polyethylene oxide polymer with different thickness

This paper reports experimental investigations of the effects of various parameters on visible laser beam attenuation characteristics for organic pure polyethylene oxide (PEO) thin films. The pure PEO thin films with various thicknesses were prepared using the solution casting method. The attenuation characteristics of the prepared pure PEO were investigated using diode pumped solid state (DPSS) laser (with wavelength 532 nm), and He–Ne laser (with wavelength 632.8 nm). For both laser systems the influences of different control parameters (including linear, circular polarization states of the laser output, the separation distance between the thin films and the optical detector, and the laser beam incidence angle on thin films) on laser beam power attenuation were obtained. The DPSS laser beam output power with linear polarization has greater attenuation characteristics than other control parameters used in this work.

Improving Li-ion interfacial transport in hybrid solid electrolytes.

The development of commercial solid-state batteries has to date been hindered by the individual limitations of inorganic and organic solid electrolytes, motivating hybrid concepts. However, the room-temperature conductivity of hybrid solid electrolytes is still insufficient to support the required battery performance. A key challenge is to assess the Li-ion transport over the inorganic and organic interfaces and relate this to surface chemistry. Here we study the interphase structure and the Li-ion transport across the interface of hybrid solid electrolytes using solid-state nuclear magnetic resonance spectroscopy. In a hybrid solid polyethylene oxide polymer-inorganic electrolyte, we introduce two representative types of ionic liquid that have different miscibilities with the polymer. The poorly miscible ionic liquid wets the polymer-inorganic interface and increases the local polarizability. This lowers the diffusional barrier, resulting in an overall room-temperature conductivity of 2.47 × 10-4 S cm-1. A critical current density of 0.25 mA cm-2 versus a Li-metal anode shows improved stability, allowing cycling of a LiFePO4-Li-metal solid-state cell at room temperature with a Coulombic efficiency of 99.9%. Tailoring the local interface environment between the inorganic and organic solid electrolyte components in hybrid solid electrolytes seems to be a viable route towards designing highly conducting hybrid solid electrolytes.

An asymmetric bilayer polymer-ceramic solid electrolyte for high-performance sodium metal batteries

Manufacturing an excellent solid electrolyte compatible with a high-voltage cathode is viewed as a critical tactic for improving the energy density of solid-state sodium-ion batteries (SSIBs). A novel asymmetric bilayer solid electrolyte of the PEO-SN-NaClO4|NZSP-NSO with an anti-reduction PEO-SN-NaClO4 layer close to the Na side is constructed by solution casting. The ionic conductivity is enhanced by using succinonitrile (SN) in polyethylene oxide (PEO) polymer electrolyte. The anti-oxidation layer of Na3Zr2Si2PO12 with Na2SiO3 (NZSP-NSO) is served as the support of the membrane on the cathode, which could improve the interface compatibility and electrochemical performance of SSIBs. The asymmetric bilayer solid electrolyte simultaneously features a wide electrochemical stability window (4.65 V vs. Na+/Na) and a high conductivity (2.68 × 10–4 S cm−1). Furthermore, the solid electrolyte demonstrates stable Na plating/stripping over 700 h and remarkably improves cycling stability in Na/Na3V2(PO4)3 batteries with an ultra-high capacity retention of 99.6% after 100 cycles at 50 °C and 0.5 C. This study provides an effective strategy for designing asymmetric high sodium ion conductivity solid-state electrolytes for high-performance SSIBs.

Hybrid electrospun scaffold loaded with Argireline acetate and Dexpanthenol for skin regeneration

Tissue engineering provides novel methods for a wide variety of skin injuries, among which, the electrospun nanofibers have attracted special attention for wound dressing fabrications. In this research, we have fabricated scaffolds based on Poly l-lactic acid (PLLA) and Polyethylene oxide (PEO) polymers and have loaded the hybrid PLLA/PEO with active substances, Argireline and Dexpanthenol. The five categories of nanofiber scaffolds were prepared by electrospinning: (1) PLLA, (2) PLLA/PEO hybrid scaffold, (3) PLLA/PEO hybrid scaffold loaded with Argireline (PLLA/PEO/A), (4) PLLA/PEO hybrid scaffold loaded with Dexpanthenol (PLLA/PEO/D), (5) PLLA/PEO hybrid scaffold loaded with Argireline and Dexpanthenol (PLLA/PEO/A/D). Our SEM analysis of the electrospun nanofibers shows that all nanofibers are bead-free and are in the range of 200–600 nm. The static water contact angle measurements via the sessile drop method have shown a transition from a hydrophobic surface for the PLLA scaffold (CA = 118.43 ± 1.6°) to a hydrophilic surface for PLLA/PEO hybrid scaffold (CA = 35.5 ± 2.8°). The addition of Argireline, Dexpanthenol, and a mixture of both has been shown to improve this wettability even further. The electrospun nanofiber scaffolds were further analyzed for their air permeability, and mechanical properties. The cytocompatibility analysis indicated superior performance for PLLA/PEO loaded with both Argireline and Dexpanthenol. The in-vivo analysis was conducted on the second-degree burn rat models in six different studied groups: 1-healthy rat, 2-negative control, and rats treated with 3-PLLA/PEO, 4-PLLA/PEO/A, 5-PLLA/PEO/D, and 6-PLLA/PEO/A/D. The wound area reduction was assessed on day 3, day 7, and day 14 in all groups along with the histology analysis based on hematoxylin/eosin. Our results show that rats treated with PLLA/PEO/A/D not only have a great reduction in the wound area, but their histology analysis demonstrates high angiogenesis and collagen formation, and epithelialization. We believe the existence of both active substances has a synergic effect on the wound healing process.

Ionic liquid doped solid polymer electrolyte: Synthesis, characterization and applications ICSEM-2021

In this paper, we have used polymer polyethylene oxide as a host matrix and novel electrolyte ionic liquid 1-ethyl-3-methylimidazolium tricyanomethanide as an dopant to increase ionic mobility. Different characterization techniques like Electrochemical impedance spectroscopy, dielectric measurement, Fourier transform, X-ray diffraction, polarized optical microscopy, thermogravinometric analysis were used to identify the electrical, optical, structural and thermal properties. A laboratory scale supercapacitor has been fabricated using optimized solid polymer electrolyte film as an electrolyte and porous carbon derived from corn starch which shows a specific capacitance 13.6 F/g at 50 mV/s scan rate.

Mechanical scission of a flexible polymer (polyethylene oxide) under highly turbulent flows through abrupt contractions

We analyze the polymer scission of a flexible polymer (polyethylene oxide) in a turbulent flow in pipelines, including abrupt contractions. The role played by these local occurrences is studied for an extensive range of concentrations and molecular weight over time (passes through our system). We pointed that the final value of the drag reduction parameter (DR) is independent of the initial value of molecular weight. This behavior is different for flows in straight tubes in the absence of local occurrences. We propose a model for DR as a function of concentration, molecular weight, contraction rate, and the number of passes through the system. We also showed that the fall of DR is linearly dependent on the molecular weight decrease.

Evidence of Many-Body Interactions in the Virial Coefficients of Polyelectrolyte Gels.

Simulation studies of aqueous polymer solutions, and heuristic arguments by De Gennes for aqueous polyethylene oxide polymer solutions, have suggested that many-body interactions can give rise to the ‘anomalous’ situation in which the second osmotic virial coefficient is positive, while the third virial coefficient is negative. This phenomenon was later confirmed in analytic calculations of the phase behavior and the osmotic pressure of complex fluids exhibiting cooperative self-assembly into extended dynamic polymeric structures by Dudowicz et al. In the present study, we experimentally confirm the occurrence of this osmotic virial sign inversion phenomenon for several highly charged model polyelectrolyte gels (poly(acrylic acid), poly(styrene sulfonate), DNA, hyaluronic acid), where the virial coefficients are deduced from osmotic pressure measurements. Our observations qualitatively accord with experimental and simulation studies indicating that polyelectrolyte materials exhibit supramolecular assembly in solution, another symptomatic property of fluids exhibiting many-body interactions. We also find that the inversion in the variation of the second (A2) and third (A2) virial coefficients upon approach to phase separation does not occur in uncharged poly(vinyl acetate) gels. Finally, we briefly discuss the estimation of the osmotic compressibility of swollen polyelectrolyte gels from neutron scattering measurements as an alternative to direct, time-consuming and meticulous osmotic pressure measurements. We conclude by summarizing some general trends and suggesting future research directions of natural and synthetic polyelectrolyte hydrogels.

Atomistic molecular dynamics in polyethylene oxide and polymethyl methacrylate blends having significantly different glass transition temperatures

AbstractThe highly asymmetric polymer blends, polyethylene oxide and polymethyl methacrylate systems, having extraordinary different original glass transition temperature (Tg) values, have been examined by the fully atomistic molecular dynamics simulations. We have determined densities against temperatures after establishing the conditions of models to clarify the composition‐dependent behavior of the systems. The relations show the intermediate region in addition to the Tg1 and Tg2, the high and low‐temperature Tg values, respectively. The trend found in the polymer blends is reproduced well from the weighted sum of plots for both homopolymers by assuming the additivity of local volumes. The dynamics of the polymer blend exhibited similar behavior with ionic systems but with different time scales. These results open new understandings for the physical meanings of the Tg in polymer blends and their relation with dynamics.