Identification of relaxation processes in pure polyethylene oxide (PEO) films by the dielectric permittivity and electric modulus formalisms

The ac‐impedance of bulk‐like films of pure polyethylene oxide (PEO) polymer was measured as a function of frequency f in the range 0.1 to 10⁷ Hz at various constant temperatures T (155 − 330 K ). The as‐measured data were analyzed by electric permittivity and modulus formalisms to unveil which dielectric and conductive relaxation processes were responsible for their relaxation behavior below/above glass transition temperature T_g of pure PEO polymer. At T > T_g , none of the α ‐, β ‐, or γ ‐relaxations could be inferred for studied pure PEO films from frequency variation of measured imaginary part ε′′(f, T) of complex dielectric permittivity , as low‐frequency losses masked real dielectric contribution to the measured ε′′(f, T) at low frequencies and high temperatures. However, at T < T_g , a broad, relaxation process has been observed in the high‐frequency part of their isothermal ε′′(f, T) − f spectra, which can be related to the β ‐ or γ ‐dielectric relaxation process. Nonlinear regressions of the measured ε′′(f, T) − f data for T < T_g yielded moral fits to a simple addition of a Havriliak‐Negami function, and a Bergman‐loss Kohlrausch‐Williams‐Watts‐type function, with the relaxation time τ_max(T) obtained from Havriliak‐Negami‐fitting parameters, was found to follow a thermally activated Arrhenius‐like relaxation behavior. Conversely, representation of the imaginary part M′′(f, T > T_g) − f spectra of complex electric modulus was found to depict 2 overlapped relaxation processes, which were detached well by a nonlinear regression of a simple superposition of 2 different M′′(f)  expressions having the form of the universal Bergman loss function, where it was found that the relaxation time is also thermally activated.     

Specific interactions in blends of poly(ethylene oxide) and poly(bisphenol A-co-epichlorohydrin): FTIR and thermal study

Blends of poly(ethylene oxide) (PEO) of high molecular weight with poly(bisphenol A-co-epichlorohydrin) (PBE) with high epoxy equivalent were studied spectroscopically, thermally and morphologically. As similar systems of low molecular weight, a single T_g was observed for all blends, indicating miscibility. A progressive decrease in the degree of crystallinity and in the size of the PEO spherulites as the PBE is added is also observed. Quantitative analysis from FTIR spectra provided determination of specific interactions between the constituents and their variation with PEO content. Simulations were performed utilising the spectra of the pure polymers to confirm that the observed changes in the experimental spectra of the blends were due to interaction between the polymers.     

两亲性嵌段聚醚酯在空气-水界面上的Langmuir单分子膜

聚醚酯是一种新型弹性材料,目前已成为工业化产品[1].对这种嵌段聚醚酯的合成和弹性行为[2]、熔体的流变性能[3]、以及纤维在拉伸状态下的聚集态结构和分子运动[4]已有一些报道.     

Study on Synthesis of Star‐Shaped Poly(ethylene oxide) by Atom Transfer Radical Polymerization

Star‐shaped poly(ethylene oxide) (PEO) was prepared by atom transfer radical polymerization (ATRP) with a 2‐bromoisobutyryl PEO ester as a macroinitiator. Divinylbenzene (DVB) and ethylene glycol dimethacrylate were employed as the coupling reagents. Several factors pertinent to star polymer formation are: type of coupling reagents and solvents, feed ratio of DVB to the macroinitiator, and reaction time. These were studied and used to optimize the star formation process. The optimum yield of star polymer was ca. 90–98%.     

Multi-step sol-gel process and its effect on the morphology of polyethylene oxide (PEO)/SiO2 anion-exchange hybrid materials

Polyethylene oxide (PEO)/SiO₂ anion-exchange hybrid materials were prepared through the sol-gel process of alkoxysilane functionalized PEO-1000 (PEO-[Si(OCH₃)₃]₂) and N-[3-(trimethoxysilyl)propyl] ethylene diamine (A-1120). The influence of the multi-step sol-gel processing procedure, i.e. the pre-hydrolysis of either of the two precursors on the homogeneity of the hybrid materials was investigated. Results showed that the sol-gel reaction of A-1120 and PEO-[Si(OCH₃)₃]₂ from the same time would result in hybrid materials with the highest homogeneity, and pre-hydrolysis of A-1120 or PEO-[Si(OCH₃)₃]₂ could only decrease the materials’ compatibility.     

A novel PEO-based composite solid-state polymer electrolyte with methyl group-functionalized SBA-15 filler for rechargeable lithium batteries

Functionalized molecular sieve SBA-15 with trimethylchlorosilane was used as an inorganic filler in a poly(ethyleneoxide) (PEO) polymer matrix to synthesize a composite solid-state polymer electrolyte (CSPE) using LiClO₄ as the doping salts, which is designated to be used for rechargeable lithium batteries. The methyl group-functionalized SBA-15 (^fSBA-15) powder possesses more hydrophobic characters than SBA-15, which improves the miscibility between the ^fSBA-15 filler and the PEO matrix. The interaction between the ^fSBA-15 and PEO polymer matrix was investigated by scanning electron microscopy, X-ray diffraction, and differential scanning calorimetry. Linear sweep voltammetry and electrochemical impedance spectroscopy were employed to study the electrochemical stability windows, ionic conductivity, and interfacial stability of the CSPE. The temperature dependence of the change of the PEO polymer matrix in the CSPE from crystallization to amorphous phase was surveyed, for the first time, at different temperature by Fourier transform infrared emission spectroscopy. It has demonstrated that the addition of the ^fSBA-15 filler has improved significantly the electrochemical compatibility of the CSPE with a lithium metal electrode and enhanced effectively the ion conductivity of the CSPE. Dedicated to Professor Oleg Petrii on the occasion of his 70th birthday on August 24th, 2007.     

Inverse gas chromatographic characterization of triblock copolymer of polystyrene–poly(ethylene oxide)–polystyrene

The thermodynamic properties of triblock copolymer of polystyrene–poly (ethylene oxide)–polystyrene (PS‐b‐PEO‐b‐PS) were investigated by means of inverse gas chromatography (IGC) using 15 different kinds of solvents as the probes. Some thermodynamic parameters, such as specific retention volume, molar heats of sorption, weight fraction activity coefficient, Flory‐Huggins interaction parameter, partial molar heats of mixing and solubility parameter were obtained to judge the interactions between PS‐b‐PEO‐b‐PS polymers and solvents and the solubility of the polymers in these solvents. It was found that increasing PEO content in PS‐b‐PEO‐b‐PS resulted in the increase in the solubility of PS‐b‐PEO‐b‐PS in alkanes and acetates solvents, but the solubility in alcohols had no change, and more PEO content in polymer caused a small decrease in the solubility parameter of PS‐b‐PEO‐b‐PS polymer, © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 2015–2022, 2007     

Synthesis and interfacial properties of novel cationic polyelectrolytes with brush-on-brush structure of poly(ethylene oxide) side chains

Novel cationic polyelectrolytes with a brush-on-brush structure of poly(ethylene oxide) (PEO) side chains and a charge-containing polyacrylate backbone were synthesized. The PEO side chains were not directly attached to the backbone but via polymethacrylate spacers, thus locating the PEO chains a distance away from the charged units of the backbone. The cationic brush-on-brush polyelectrolytes with high density of PEO chains showed a strong affinity to silica surfaces, provided the backbone charge density was high enough. The adsorption of these polymers was studied by QCM-D giving very high sensed mass, 20 mg/m². It was shown by direct force measurements that protective surface layers were formed by the novel polyelectrolytes, generating strongly repulsive steric forces, which provided an effective barrier against flocculation. The adsorbed layer was sufficiently robust to withstand sliding experiments under a pressure of up to 35 MPa. The friction force in water was very low, and the lubrication was characterized by a friction coefficient in the range of 0.02-0.06.     

Solubility and partial molar volume of carbon dioxide and ethane in crosslinked poly(ethylene oxide) copolymer

Experimental solubility and sorptive dilation data are reported for carbon dioxide and ethane in a crosslinked poly(ethylene oxide) (XLPEO) rubbery copolymer. Five different temperatures (253 ≤ T(K) ≤ 308) were considered, with a maximum gas pressure of 2.09 MPa (20.6 atm). The polymer was prepared by photopolymerization of a solution containing 70 wt % poly(ethylene glycol) methyl ether acrylate (PEGMEA) and 30 wt % poly(ethylene glycol) diacrylate (PEGDA). Sorption isotherms were described by the Flory‐Huggins model. For each gas, the Flory‐Huggins interaction parameter was a decreasing function of temperature and did not show a composition dependence. Dilation and sorption data were combined to calculate the partial molar volume (PMV) of the gases in the polymer, which was an increasing function of temperature. Based on a comparison with literature data for a XLPEO homopolymer prepared from pure PEGDA over the same range of operating conditions, an effect of the network composition on both gas solubility and PMV was found. © 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 48: 456–468, 2010     

Polymer blend/organoclay nanocomposite with poly(ethylene oxide) and poly(methyl methacrylate)

A series of polymer blend/organoclay nanocomposite at a fixed blending ratio was prepared using equal ratio of poly(ethylene oxide) (PEO) and poly(methyl methacrylate) (PMMA) via solvent casting method. With respect to nanoscale internal structure, we found that PMMA chains have better affinity with organoclay than PEO, based on the results from X-ray diffraction. Direct visualization via transmission electron microscopy (TEM) also supported the better affinity of PMMA with organoclay by indicating the existence of hybrid structures of mainly intercalated but with some exfoliated forms. The miscible nature of the blend and homogeneous dispersion state of layered silicate in the blend system were investigated via the microscopic fractured surface morphologies. From rheological measurements (storage and loss modulus), we discovered the role of the physical network structure between polymer and organoclay to be a main factor for the enhancement of elastic properties.