Swelling of poly(ethylene oxide) gel in aqueous solutions of sodium dodecyl sulfate with added sodium chloride

The swelling behavior of poly(ethylene oxide) (PEO) gels in aqueous solutions of sodium dodecyl sulfate (SDS) with and without NaCl was investigated. In the absence of NaCl, PEO gels with different degrees of cross-linking began to swell from a concentration lower than the critical micelle concentration (cmc) of SDS, then showed sigmoidal enhancements of swelling in a higher SDS concentration region until the degrees of swelling reached maximum values. The SDS concentration at which the swelling began to appear was in reasonable agreement with the critical aggregation concentration (cac) value reported for the aqueous PEO system. For the cases where NaCl was present, the swelling behavior of PEO gel was different from that when NaCl was absent in the following way. The concentrations where the swelling begins to appear, and hence those where the degree of swelling rises steeply, decreased with an increase in NaCl concentration. The ultimate degrees of swelling at higher concentration regions also decreased with an increase in the NaCl concentration. The lowering of the SDS concentrations at which the PEO gel began to swell is in line with the decreases in the cmc of SDS solutions containing NaCl and also with the decreases in the cac of PEO solution. Electronic Publication     

Interaction between poly(ethylene oxide) and sodium dodecyl sulfonate as studied by surface tension, conductivity, viscosity, electron spin resonance and nuclear magnetic resonance

The aggregation of sodium dodecyl sulfonate (AS) in aqueous solution containing various amounts of poly(ethylene oxide) (PEO) has been investigated by different experimental techniques. The experimental techniques include surface tension, conductivity, viscosity, electron spin resonance (ESR) and nuclear magnetic resonance (NMR). The critical aggregate concentration of AS on polymer strands as well as the concentration where the polymer becomes saturated with surfactant has been determined. Both ESR and NMR results indicate that the AS–PEO complex forms a more “open” structure and that PEO may penetrate into the interior of the micelles. Received: 22 October 1998 Accepted in revised form: 1 April 1999     

Bonding mechanisms and conformation of poly(ethylene oxide)-based surfactants in interlayer of smectite

A better understanding of the interactions between poly(ethylene oxide) (PEO)-based nonionic surfactants and smectite is important to fully comprehend the transport and the fate of nonionic surfactants in the environment and to design novel organo-clay composites. We studied the bonding between the surfactants and smectite and the molecular conformations of the surfactants in the interlayer of smectite. A reference polymer PEG and three nonionic surfactants—Brij 56, Brij 700, and PE-PEG—were intercalated into a smectite. The polymers and the composites were characterized with X-ray diffraction (XRD) and Fourier transform infrared (FT-IR) spectroscopy. The XRD and FT-IR results indicate that the bulk surfactants existed as crystalline materials at room temperature, and surfactant molecules had both helical/extended diblock and planar zigzag conformations. The surfactants intercalated smectite and expanded the d(001) spacing of smectite to nearly 1.8 nm. The shapes and positions of the IR bands of interlayer surfactants were similar to those of the melted (amorphous) bulk polymers: the wagging vibrations of the CH₂ merged to a single band at 1,350 cm⁻¹, the twisting bands of CH₂ had 9 cm⁻¹ or more blue shifts. These changes imply that the PEO segments of the surfactants existed with a distorted and extended conformation in the interlayer of smectite, and this extended conformation was an intermediate form of the helical and planar zigzag conformations. The molecular conformation of the interlayer surfactant was not affected by the seven types of exchangeable cations (Na⁺, K⁺, Ca²⁺, Mg²⁺, Cu²⁺, Ni²⁺, and H⁺) tested. There were 20 cm⁻¹ or more red shifts from the C–O–C stretching bands when the surfactants were adsorbed. The red shifts suggest that surfactants were bonded to smectite mainly through (1) H-bonding between oxygen atoms of the PEO segments and water molecules in hydration shells of the exchangeable cations, and (2) direct coordination or ion–dipole interaction between the oxygen atoms of the PEO segments and the exchangeable cations. With the extended conformation, the oxygen atoms of the PEO segments have maximum exposure to the bonding water molecules and exchangeable cations.     

Structure,rheology and electrospinning of zein and poly(ethylene oxide) in aqueous ethanol solutions

This study provided a clear correlation of the structure and rheology of solutions with the morphologies of EFM made up of proteins and polymers.     

阻抑褪色光度法测定水样中阴离子表面活性剂

在弱酸性的HCl-NaOAC缓冲介质中,溴化十六烷基吡啶(CPB)和曙红Y(EY)染料的混合溶液发生褪色,在该褪色的溶液中分别加入十二烷基硫酸钠(SDS)及十二烷基苯磺酸钠(SDBS)等阴离子表面活性剂(AS),溶液颜色发生改变,最大吸收波长都在514 nm处,并分别在548、546 nm处产生明显褪色。在吸收或褪色波长处,阴离子表面活性剂的浓度与增色或褪色程度呈良好线性关系,从而建立测定阴离子表面活性剂的光度法。在最大吸收波长处,SDBS体系、SDS体系中AS的浓度在0~2.06×10-5mol/L、0~2.63×10-5mol/L范围内遵守比尔定律,表观摩尔吸光系数分别为1.30×104、1.01×104L.mol-1.cm-1,检出限分别为8.14×10-7、9.96×10-7mol/L。若用双波长叠加,表观摩尔吸光系数达2.07×104、1.78×104L.mol-1.cm-1,检出限为4.82×10-7、8.34×10-7mol/L。方法具有较高的灵敏度和良好的选择性,用于水样中AS的测定。     

Synthesis and properties of segmented block copolymers based on mixtures of poly(ethylene oxide) and poly(tetramethylene oxide) segments

The synthesis and characterisation of segmented block copolymers based on mixtures of hydrophilic poly(ethylene oxide) and hydrophobic poly(tetramethylene oxide) polyether segments and monodisperse crystallisable bisester tetra-amide segments are reported. The PEO length was varied from 600 to 8000 g/mol and the PTMO length was varied from 650 to 2900 g/mol. The influence of the polyether phase composition on the thermal mechanical and the elastic properties of the resulting copolymers was studied.The use of high melting monodisperse tetra-amide segments resulted in a fast and almost complete crystallisation of the rigid segment. The copolymers had only one polyether glass transition temperature, which suggests that the amorphous polyether segments were homogenously mixed. Thermal analysis of the copolymers showed one polyether melting temperature that was lower than in the case of ideal co-crystallisation between the two polyether segments. However, at PEO or PTMO lengths larger than 2000 g/mol two polyether melting temperatures were observed. The copolymer with the best low temperature properties was based on a mixture of PEO and PTMO segments, both having a molecular weight of 1000 g/mol, at a weight ratio of 30/70.     

Polymer electrolyte for lithium batteries based on photochemically crosslinked poly(ethylene oxide) and ionic liquid

Polymer/ionic liquid composites were investigated as solvent-free electrolytes for lithium batteries. Ternary electrolytes based upon poly(ethylene oxide), an ionic liquid and a conducting salt were UV crosslinked with benzophenone as the photoinitiator. Crosslinking leads to an increase in mechanical stability of the PEO composites. This straight-forward process provides a way to increase the content of ionic liquid and thus to raise ionic conductivity without loss of mechanical stability. Impedance measurements showed that the ionic conductivity of the composites is not affected by the UV curing process. Moreover, the UV curing process causes a decrease in the degree of crystallinity in the PEO composites which contributes to an increase in ionic conductivity. The present work is related to safety issues of lithium batteries.     

Photodegradation studies of novel biodegradable blends based on poly(ethylene oxide) and pectin

Blends of two biodegradable polymers: natural pectin and synthetic poly(ethylene oxide) at different weight-ratios were obtained by physical mixing in aqueous solutions, and evaporation of the solvent. The macromolecular order in the composites was investigated by applying X-ray diffraction, while the surface morphology was observed using atomic force microscopy. The photooxidative degradation of the blends was studied by viscometry, FTIR spectroscopy and UV-vis spectroscopy. It has been found that the susceptibility of the studied composites to UV radiation depends on an appropriate ratio of components, and the most sensitive to UV-irradiation among the samples studied was the equal weight-ratio blend of poly(ethylene oxide)/pectin.     

Thermal degradation of poly(vinyl chloride)/poly(ethylene oxide) blends: Thermogravimetric analysis

Thermal stability of poly(vinyl chloride)/poly(ethylene oxide) (PVC/PEO) blends has been investigated by thermogravimetric analysis (TGA) in dynamic and isothermal heating regime. PVC/PEO blends were prepared by hot-melt extrusion (HME). According to TG analysis, PEO decomposes in one stage, while PVC and PVC/PEO blends in two degradation stages. In order to evaluate the effect of PEO content on the thermal stability of PVC/PEO blends, different criteria were used. It was found that thermal stability of PVC/PEO blends depends on the blend composition. The interactions of blends components with their degradation products were confirmed. By using multiple heating rate kinetics the activation energies of the PVC/PEO blends thermal degradation were calculated by isoconversional integral Flynn–Wall–Ozawa and differential Friedman method. According to dependence of activation energy on degree of conversion the complexity of degradation processes was determined.     

Structure and properties of new polyester elastomers composed of poly(trimethylene terephthalate) and poly(ethylene oxide)

Series of PTT-b-PEO copolymers with different composition of rigid PTT and PEO flexible segments were synthesized from dimethyl terephthalate (DMT), 1,3-propanediol (PDO), poly(ethylene glycol) (PEG, M_n = 1000 g/mol) in a two stage process involving transesterification and polycondensation in the melt. The weight fraction of flexible segments was varied between 20 and 70 wt%. The molecular structure of synthesized copolymers was confirmed by ¹H NMR and ¹³C NMR spectroscopy. The superstructure of these polymers was characterized by DSC, DMTA, WAXS and SAXS measurements. It was observed that domains of three types can exist in PTT-b-PEOT copolymers: semi-crystalline PTT, amorphous PEO rich phase (amorphous PEO/PTT blended phase) and semi-crystalline PEO phase. Semi-crystalline PEO phase was observed only at temperature below 0 °C for sample containing the highest concentration of PEO segment. The phase structure, thermal and mechanical properties are effected by copolymer composition. The copolymers containing 30÷70 wt% of PEO segment posses good thermoplastic elastomers properties with high thermal stability. Hardness and tensile strength rise with increase of PTT content in copolymers.     

Calorimetric investigation of temperature effect on the interaction between poly(ethylene oxide) and sodium dodecylsulfate in water

The interaction of four poly(ethylene oxides), with molar masses of 1500, 3350, 10 000 and 100 000 g mol⁻¹ with sodium dodecylsulfate, at 15, 25, 35 and 65 °C was investigated by isothermal titration calorimetry. No significant change of the critical aggregation concentration values or of the amount of surfactant bound was observed within this temperature range. The profiles for the variation of the observed enthalpies with surfactant concentration, however, are quite different for the four studied temperatures, what has been interpreted as a consequence of a change in the mode of poly(ethylene oxide) (PEO) interaction with sodium dodecylsulfate (SDS) micelles within this temperature range.     

Influence of water on the photodegradation of poly(ethylene oxide)

The UV-light degradation of polyethylene oxide (PEO) in aqueous solution was investigated operating under long wavelengths (λ > 300 nm) at 20 °C in different pH conditions varying from 2.3 to 12.0 and at two different concentrations. Thermo-oxidation experiments on PEO aqueous solution at 50 °C are also reported and compared to photo-oxidation results. The formation of oxidation products was followed by infrared analysis of deposits obtained by evaporation of aliquots of irradiated polymer solution. Photo-oxidation led to formates and esters but a third product was also identified, formic acid ions formed by partial hydrolysis of formates. The degradation of PEO in water led to the acidification of the aquatic medium. Size exclusion chromatography (SEC) was used to monitor the changes in molar weight and intrinsic viscosity with irradiation time. It was shown that the photo-oxidation produced a dramatic decrease of the average molar weights which is more important in acidic medium. Total organic carbon (TOC) measurements of the aged aqueous solutions showed that the mineralization of PEO could not be achieved in these photo-oxidative conditions.     

Preparation and ionic conductivity of poly(ethylene oxide) oligomers having thiolate groups on the chain ends

Poly(ethylene oxide) (PEO) oligomers having alkali metal thiolate groups on the chain ends (PEO _m -S⁻M⁺) were prepared as an ion conductive matrix. The molecular weight of the PEO part (m) and the content of the thiolate groups in the molecule were changed to analyze the effect of carrier ion concentration in the bulk. In a series of potassium salt derivatives, PEO₃₅₀-SK showed the highest ionic conductivity of 6.42 × 10⁻⁵ S/cm at 50 °C. In spite of a poor degree of dissociation which was derived from the acidity of the thiolate groups, PEO _m -SM showed quite high ionic conductivity among other PEO/salt hybrids. PEO _m -SM had glass transition temperatures (T _g) 20 °C lower than other PEO/salt hybrids. Lowering the T _g was concluded to be effective in providing higher ionic conductivity for PEO-based polymer electrolytes. Received: 30 April 1999 / Accepted: 20 June 1999     

Thermodynamic properties of surfactant sodium n-heptyl sulfonate in water and in aqueous solutions of poly(ethylene glycol) at different temperatures

The volumetric, compressibility and electrical conductivity properties of sodium n-heptyl sulfonate (C₇SO₃Na) in pure water and in aqueous poly(ethylene glycol) (PEG) solutions were determined at different temperatures below and above the micellar composition range. At each temperature, the infinite dilution apparent molar volumes of the monomer and micellar state of C₇SO₃Na in aqueous PEG solutions respectively are smaller and larger than those in pure water. However, the values of the infinite dilution apparent molar isentropic compressibility of both monomer and micellar states of C₇SO₃Na in aqueous PEG solutions are larger than those in pure water. Thermodynamic parameters of micellization of investigated surfactant in water and in aqueous solutions of PEG at different temperatures were estimated and it was found that the micelle formation process is endothermic and therefore, this process must be driven by entropy increase. The calculated Gibbs free energies of micellization for aqueous PEG solutions are more negative than those for pure water and become more negative by increasing temperature. The variation of the critical micelle concentration (CMC) of C₇SO₃Na in water and in aqueous PEG solutions with temperature was obtained and a comparison between the CMC of C₇SO₃Na obtained from different thermodynamic properties was also made.     

顺磁共振和紫外光谱法研究SDS-PEO体系的相互作用

合成更疏水的自旋探针4 羰基 2,2,6,6 四甲基哌啶氮氧自由基 2,4 二硝基苯腙.用顺磁共振（ESR）和紫外光谱法研究了十二烷基硫酸钠（SDS） 0.5 ％(w,质量分数)聚氧乙烯（PEO）体系的分子间相互作用. ESR结果表明,此水溶液体系的微极性随SDS浓度增大而减小,并且SDS与PEO聚集体具有更加紧密的堆积结构使其结合处具有较大的微粘性, SDS与PEO间的相互作用导致PEO分子链伸展. UV表明自旋探针分子可能靠近胶束的表面存在, 2,4 二硝基苯肼基团可能位于靠近SDS的硫酸根基团,定向于SDS胶束的表面,氮氧自由基基团短距离渗透到SDS胶束的碳氢核.     

Thermal and crystallization characteristics of poly(trimethylene terephthalate)/poly(ethylene naphthalate) blends

Poly(trimethylene terephthalate) (PTT)/poly(ethylene naphthalate) (PEN) blends were miscible in the amorphous state in all of the blend compositions studied, as evidenced by a single, composition-dependent glass transition temperature (T_g) observed for each blend composition. The variation in the T_g value with the blend composition was well predicted by the Gordon-Taylor equation, with the fitting parameter being 0.57. The cold-crystallization peak temperature decreased with increasing PTT content, while the melt-crystallization peak temperature decreased with increasing amount of the minor component. The subsequent melting behavior after both cold- and melt-crystallization exhibited melting point depression, in which the observed melting temperatures decreased with increasing amount of the minor component. During melt-crystallization, both components in the blends crystallized concurrently just to form their own crystals. The blend with 60% w/w of PTT exhibited the lowest total apparent degree of crystallinity.     

Compatibility and phase structure of binary blends of poly(lactic acid) and glycidyl methacrylate grafted poly(ethylene octane)

This work study is the compatibility, phase structure, and component interaction of poly(lactic acid) (PLA) and glycidyl methacrylate grafted poly(ethylene octane) (GMA-g-POE denoted as mPOE) blend by Fourier transform infrared (FTIR) spectra, dynamic mechanical analysis (DMA), scanning electron microscopy (SEM), and wide-angle X-ray diffraction (WAXD), respectively. All the binary blend compositions exhibit two distinct glass transition temperatures corresponding to the mPOE-rich and PLA-rich phases, respectively. Moreover, these two peaks approach each other with increasing mPOE content, indicating partial compatibility between the PLA and mPOE. Chemical reactions between the end carboxyl groups of the PLA and epoxy groups of the mPOE are considered as the driving force of the enhanced compatibility. They lead to an increase in viscosity of the blends and a decrease in the structural symmetry of PLA. This result brings about a decrease in the spherulite growth rate and the degree of crystallinity. Glass transition temperature (T_g) depression of mPOE is attributed to the negative pressure imposed on the dispersed rubber phase, resulting from differential contraction due to the thermal shrinkage mismatch upon cooling from the melt state. The negative pressure in the dispersed particles, in turn, would cause a dilational effect for the matrix ligament between the particles, and therefore increases the ductility and toughness of PLA.     

Effects of solvents on the crystallization of dilute poly(ethylene oxide) solutions

The crystallization kinetics of a poly(ethylene oxide) sample with molecular weight of 20 000 was studied in dilute solutions ofn-propanol,n-butanol andn-pentanol by dilatometric methods. The value of the Avrami exponent was observed to change with crystallization temperature in poorer solvents. The temperature coefficient of overall rate was analyzed according to the theory developed for polymer-diluent mixtures. Statistical analysis of data pertinent to overall rate temperature coefficient showed that the end surface free energy _en changes with the thermodynamic quality of the solvent. This is considered to be attributed to the loss in flexibility of polymer chains due to the intramolecular association displayed by poly(ethylene oxide) in its solutions of poor solvents.     

The Synthesis of Poly(ethylene oxide)-Block-Polybutylacrylate

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Thermal ageing of poly(ethylene oxide)/poly(3,4-ethylenedioxythiophene) semi-IPNs

The thermal stability study of a conducting semi-IPN has been reported. The thermo-oxidation of poly(ethylene oxide) (PEO)/poly(3,4-ethylenedioxythiophene) (PEDOT) semi-Interpenetrating Polymer Network (semi-IPN) was studied at 80 °C in open air. The degradation was followed by spectrophotometry in the visible and near infrared range, cyclic voltamperometry and thermogravimetric analysis. Fluorescence spectrophotometry allowed for the identification of OH by-product originated in the PEO network degradation by the use of a chemiluminescent probe, typically terephthalic acid. The formation of hydroxyl radicals damaged the PEDOT chains as checked by infrared spectroscopy. The mechanism of degradation is further confirmed (i) by introducing a radical scavenger or (ii) by performing a thermal ageing under inert atmosphere; in both cases the semi-IPN life-time is tremendously increased.