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1.
In order to prepare flexible and ion conductive deoxyribonucleic acid (DNA) films without phase separation, DNA was modified with poly(ethylene oxide) (PEO). PEOs with molecular weight of 150 to 2000 were fixed to the amino groups of nucleic acid bases in DNA (PEO‐DNA). Brittle DNA films turned flexible after PEO modification, and the highest ionic conductivity was obtained when PEO with molecular weight of 1000 was modified. Though Na+, counter cation of phosphate group, was expected to migrate in these PEOx‐DNA hybrids as a carrier ion, ionic conductivity was only 1.3 × 10?6 S cm?1. Addition of salts to PEO1000‐DNA considerably improved the ionic conductivity, and sodium bis(trifluoromethanesulfonyl)imide (NaTFSI) was the best salt for this purpose. When NaTFSI, 5 mol% to the oxyethylene (OE) unit, was mixed with PEO1000‐DNA, the highest ionic conductivity of 1.77 × 10?5 S cm?1 was observed at 30°C. Copyright © 2004 John Wiley & Sons, Ltd.  相似文献   

2.
用自然白光代替偏振光在显微镜下观察聚氧乙烯球晶的生长过程, 可以更清晰地看到彩色环形条纹的形成. 当成长中的二维球晶相互碰撞后, 被挤出的熔体改变球晶的原有结晶方向, 流向饼形球晶中央而在其表面上逆向结晶, 由于被挤出的熔体数量有限, 晶层的厚度逐渐减小, 在盖玻片下方形成一个盘状的楔形真空间隙. 此间隙导致彩色环状干涉条纹的形成. 实验用肉眼直接观察到二维球晶在生长过程中结晶方式的变化, 为二次结晶理论的发展提供了实验依据.  相似文献   

3.
The redox reaction of poly(ethylene oxide) (PEO)-modified hemoglobin (PEO–Hb) was analyzed in PEO oligomers with cyclic voltammetry. The PEO–Hb was made soluble in PEO with molecular weight of 200 (PEO200) containing 0.5 M KCI. Quasi-reversible redox signals of PEO–Hb were obtained by using an indium tin oxide (ITO) glass working electrode. PEO–Hb, cast on the ITO electrode, also showed the redox response in PEO with molecular weight of 400 (PEO400). The peak current of PEO–Hb on the ITO electrode gradually increased during potential cycling. The effect of the scan rate on the quantity of electricity (Q) was analyzed after the peak current reached a constant value. The constant Q value was observed at the scan rate ranging from 30 to 500 mV/sec. The number of reactive PEO–Hb molecules was estimated from this constant Q-value. It was suggested that the electron transfer was carried out at the first layer of the PEO–Hb which was in direct contact with the ITO electrode. The quantity of electricity of PEO–Hb increased when the ITO electrode was first washed in an aqueous medium with ultrasonicator. This strongly suggested that the more effective surface area of the ITO electrode turned to be covered with PEO–Hb when the microporous region of the ITO particles was more hydrated.  相似文献   

4.
Aqueous solutions of a poly(ethylene oxide)–poly(propylene oxide)–poly(ethylene oxide) triblock copolymer, Pluronic F108 (PEO133PPO50PEO133), ranging from 1 to 35 wt %, were studied with differential scanning microcalorimetry and rheology. The thermoreversible micellization and gelation were examined through a heating process and a subsequent cooling process at a fixed rate of 1 °C/min. The critical micellization temperature (CMT), determined by the onset temperature of the endothermic peak in the heating process, was a decreasing function of the F108 concentration. A small secondary endothermic peak appeared only when the polymer concentration was 22.5 wt % or higher, indicating that there was a sol–gel transition but that the gelation was a nearly athermic process. Upon heating, an abrupt increase was observed in both the dynamic storage modulus (G′) and dynamic loss modulus (G″) within a narrow temperature range. TG′, the temperature for the transition in G′, was a linear decreasing function of the polymer concentration and different from CMT. TG′ tended to approach CMT with an increasing F108 concentration. Beyond this transition, G′ reached a plateau, and the plateau increased in height and broadened with the polymer concentration. The value of G′ at 70 °C (G70) could be approximately scaled with concentration c by G70c7.3. In addition, the definition for a gel to obey G′ > G″ was valid only when c was greater than 22.5 wt %, and this was in agreement with the secondary endothermic peak found with differential scanning calorimetry. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 2014–2025, 2004  相似文献   

5.
An amphiphilic multiblock copolymer [poly(ethylene oxide)‐b‐polystyrene]n [(PEO‐b‐PS)n] is synthesized by using trithiocarbonate‐embedded PEO as macro‐RAFT agent. PEO with four inserted trithiocarbonate (Mn = 9200 and Mw/Mn = 1.62) groups is prepared first by condensation of α, ω‐dihydroxyl poly(ethylene oxide) with S, S′‐Bis(α, α′‐dimethyl‐α″‐acetic acid)‐trithiocarbonate (BDATC) in the presence of pyridine, then a series of goal copolymers with different St units (varied from 25 to 218 per segment) are obtained by reversible addition‐fragmentation chain transfer (RAFT) polymerization. The synthesis process is monitored by size exclusion chromatography (SEC), 1H NMR and FT‐IR. The self‐assembled morphologies of the copolymers are strongly dependent of the length of PS block chains when the chain length of PEO is fixed, some new morphologies as large leaf‐like aggregates (LLAs), large octopus‐like aggregates (LOAs), and coarse‐grain like micelles (CGMs) are observed besides some familiar aggregates as large compound vesicles (LCVs), lamellae and rods, and the effect of water content on the morphologies is also discussed. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 6071–6082, 2006  相似文献   

6.
Using core‐first strategy, the amphiphilic A4B4 star‐shaped copolymers [poly(ethylene oxide)]4[poly(ε‐caprolactone)]4 [(PEO)4(PCL)4], [poly(ethylene oxide)]4[poly(styrene)]4 [(PEO)4(PS)4], and [poly(ethylene oxide)]4[poly(tert‐butyl acrylate)]4 [(PEO)4(PtBA)4] were synthesized by mechanisms transformation combining with thiol‐ene reaction. First, using a designed multifunctional mikto‐initiator with four active hydroxyl groups and four allyl groups, the four‐armed star‐shaped polymers (PEO‐Ph)4/(OH)4 with four active hydroxyl groups at core position were obtained by sequential ring‐opening polymerization (ROP) of ethylene oxide monomers, capping reaction of living oxyanion with benzyl chloride, and transformation of allyl groups into hydroxyl groups by thiol‐ene reaction. Then, the A4B4 star‐shaped copolymers (PEO)4(PS)4 or (PEO)4(PtBA)4 were obtained by atom transfer radical polymerization (ATRP) of styrene or tert‐butyl acrylate (tBA) monomers from macroinitiator of (PEO‐Ph)4/(Br)4, which was obtained by esterification of (PEO‐Ph)4/(OH)4 with 2‐bromoisobutyryl bromide. The A4B4 star‐shaped copolymers (PEO)4(PCL)4 were also obtained by ROP of ε‐caprolactopne monomers from macroinitiator of (PEO‐Ph)4/(OH)4. The target copolymers and intermediates were characterized by size‐exclusion chromatography, matrix‐assisted laser desorption/ionization time‐of‐flight mass spectroscopy, and nuclear magnetic resonance in detail. This synthetic route might be a versatile one to various AnBn (n ≥ 3) star‐shaped copolymers with defined structure and compositions. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013 , 51, 4572–4583  相似文献   

7.
曲晓刚  杨辉 《电化学》1998,4(3):260-264
本文报道了细胞色素C在聚乙烯氧化物修饰的金电极上的直接电化学行为,发现PEO是细胞色素C电化学反应的促进剂,PEO修饰膜的形态对细胞色素C电化学反应的可逆性有较大的影响。  相似文献   

8.
Motion of chains of poly(ethylene oxide) within the interlayer spacing of 2:1 phyllosilicate/montmorillonite was studied with 1H and 13C NMR spectroscopy. Measurements of the 1H NMR line widths and relaxation times across a large temperature range were used to determine the effect of bulk thermal transitions on polymer chain motion within the nanocomposites. The results were consistent with previous reports of low apparent activation energies of motion. Details of the frequency and geometry of motion were obtained from a comparison of the 13C cross‐polarity/magic‐angle spinning spectra and relaxation times of the nanocomposite with those of the pure polymer. © 2001 John Wiley & Sons, Inc. J Polym Sci Part B: Polym Phys 39: 1678–1685, 2001  相似文献   

9.
The copolymer of polystyrene‐block‐poly(ethylene oxide)‐block‐poly (tert‐butyl acrylate) (PS‐b‐PEO‐b‐PtBA) was prepared, the synthesis process involved ring‐opening polymerization (ROP), nitroxide‐mediated polymerization (NMP), and atom transfer radical polymerization (ATRP), and 4‐hydroxyl‐2,2,6,6‐tetramethylpiperidinyl‐1‐oxy (HTEMPO) was used as parent compound. The PEO precursors with α‐hydroxyl‐ω‐2,2,6,6‐tetramethylpiperidinyl‐1‐oxy end groups(TEMPO‐PEO‐OH) were first obtained by ROP of EO using HTEMPO and diphenylmethylpotassium (DPMK) as the coinitiator. The TEMPO at one end of PEO chain mediated the polymerization of St using benzoyl peroxide as initiator. The resultant PS‐b‐PEO‐OH reacted further with 2‐bromoisobutyryl bromide and then initiated the polymerization of tBA in the presence of CuBr and PMDETA by ATRP. The ternary block copolymers PS‐b‐PEO‐b‐PtBA and intermediates were characterized by gel permeation chromatography, Fourier transform infrared, and nuclear magnetic resonance spectroscopy in detail. Differential scanning calorimetry measurements confirmed that the PS‐b‐PEO‐b‐PtBA with PEO as middle block can weaken the interaction between PS and PtBA blocks, the glass transition temperature (Tg) for two blocks were approximate to their corresponding homopolymers comparing with the PEO‐b‐PS‐b‐PtBA with PEO as the first block. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 2624–2631, 2008  相似文献   

10.
Blends of polystyrene (PS) and poly(styrene-b-ethylene oxide) (PS-b-PEO) were cast from a ternary solvent mixture containing 85% toluene, 10% tetrahydrofuran, and 5% methanol under conditions that favor crystallization of the PEO phase. Electric fields (2–14 kV/cm) were applied during casting to explore the possibility of morphology control by the field. It was observed that films cast in the absence of an electric field, in the temperature range of 0–25°C, from solutions initially cooled to 0°C were translucent. Their transmission electron micrographs exhibited thread-like, fibrillar structures. Micrographs of films cast in dc fields of 2–14 kV/cm at 16.3 ± 0.4°C also showed fibrillar structures, with the fibrils in the presence of fields greater than 8 kV/cm being substantially oriented in the field direction. We suggest that the morphologies developed under these conditions result from crystallization from preexisting crystal nuclei in the cooled solutions with the fibrillar crystals being oriented by the electric field. This method provides a possible way of processing anisotropic polymer blends. © 1996 John Wiley & Sons, Inc.  相似文献   

11.
Adsorption of cytochrome c (Cyt c) on a gold nanoparticle – modified gold electrode was studied by using cyclic voltammetry, electrochemical impedance spectroscopy and chronopotentiometry in a phosphate buffer solution. It is shown that the charge transfer resistance is directly proportional to the amount of adsorbed Cyt c. The effects of temperature and time on the course of adsorption were also studied. The trends obtained in ΔGADS showed that Cyt c was found to have a smaller affinity for the modified electrode as indicated by their smaller negative ΔGADS values.  相似文献   

12.
The dendrimer‐like copolymers [PEEGE‐(PS/PEO)]n (n ≥ 2) based on the star[Polystyrene‐Poly(ethylene oxide)‐Poly(ethoxyethyl glycidyl ether)] [star(PS‐PEO‐(PEEGE‐OH))] terpolymers were synthesized by click chemistry. First, the star‐shaped copolymers star[PS‐PEO‐(PEEGE‐Alkyne)] (also termed as [PEEGE‐(PS/PEO)]1) were synthesized by the reaction of hydroxyl end group at PEEGE arm (on star[PS‐PEO‐(PEEGE‐OH)]) with propargyl bromide. Then, the small molecule 1,4‐diazidobutane (DAB) with two azide groups and pentaerythritol tetrakis (2‐azidoisobutyrate) (PTAB) with four azide groups were synthesized and reacted with [PEEGE‐(PS/PEO)]1 by the click chemistry for dendrimer‐like [PEEGE‐(PS/PEO)]2 and [PEEGE‐(PS/PEO)]4, respectively. However, in the latter case, only the [PEEGE‐(PS/PEO)]3 was formed as the main product because of the steric effect. The final dendrimer‐like [PEEGE‐(PS/PEO)]n copolymers were characterized by SEC and 1H‐NMR in detail. Comparing with the SEC of their precursor [PEEGE‐(PS/PEO)]1, the curves of [PEEGE‐(PS/PEO)]2 was shifted to the shorter elution time, while that of [PEEGE‐(PS/PEO)]n (n ≥ 3) was shifted to the longer elution time, which was attributed to the different hydrodynamic volume derived from their separate structures and compositions in THF solution. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 4800–4810, 2009  相似文献   

13.
The eight‐shaped poly(ethylene oxide) (PEO) is synthesized by a combination of Glaser coupling with ring‐opening polymerization (ROP). Firstly, the star‐shaped (PEO‐OH) 4 is synthesized by ROP of ethylene oxide (EO) using pentaerythritol as an initiator and diphenylmethyl potassium (DPMK) as a deprotonated agent, and then the alkyne group is introduced onto the PEO arm‐end to give (PEO‐Alkyne) 4 in a NaH/tetrahydrofuran (THF) system. The intramolecular cyclization is carried out by a Glaser coupling reaction in a pyridine/CuBr/N,N,N′,N″,N″‐pentamethyldiethylenetriamine (PMDETA) system at room temperature in an air atmosphere, and eight‐shaped PEO was formed with high efficiency (almost 100%). The target polymers and intermediates were well characterized by SEC, MALDI‐TOF MS, 1H NMR and FT‐IR in detail.

  相似文献   


14.
Colloidal stabilization of nanoparticle dispersions is central to applications including coatings, mineral extraction, and dispersion of oil spills in oceanic environments, which often involves oil-mineral-aggregates (OMAs). We have an ongoing interest in the modulation of amphiphile micellization and adsorption behavior in aqueous colloidal dispersions in the presence of various additives. Here we evaluate the effect of added salts CaCl2, MgCl2, and NaCl on the micellization and adsorption behavior of the poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) triblock copolymer Pluronic P105 (EO37PO56EO37). In 0.10 wt% silica nanoparticle (10.6 nm average diameter) dispersion, adsorbed block copolymer layer formation begins at a critical surface micelle concentration (csmc) of 0.02 wt%, well below the critical micellization concentration of Pluronic P105 in water. Dye solubilization experiments demonstrate an increase in the csmc upon addition of each salt. Each added salt reaches a level of maximum effectiveness in its ability to disfavor Pluronic P105 adsorption at the silica surface. These peak levels occur at concentrations of 0.005, 0.03, and 0.05 M for CaCl2, MgCl2, and NaCl, respectively, in the presence of 0.10 wt% silica nanoparticles. We explain these results in the context of an electrostatic displacer mechanism and discuss possible connections to OMA-dispersant formation.  相似文献   

15.
The tadpole‐shaped copolymers polystyrene (PS)‐b‐[cyclic poly(ethylene oxide) (PEO)] [PS‐b‐(c‐PEO)] contained linear tail chains of PS and cyclic head chains of PEO were synthesized by combination of Glaser coupling with living anionic polymerization (LAP) and ring‐opening polymerization (ROP). First, the functionalized polystyrene‐glycerol (PS‐Gly) with two active hydroxyl groups at ω end was synthesized by LAP of St and the subsequent capping with 1‐ethoxyethyl glycidyl ether and then deprotection of protected hydroxyl group in acid condition. Then, using PS‐Gly as macroinitiator, the ROP of EO was performed using diphenylmethylpotassium as cocatalyst for AB2 star‐shaped copolymers PS‐b‐(PEO‐OH)2, and the alkyne group was introduced onto PEO arm end for PS‐b‐(PEO‐Alkyne)2. Finally, the intramolecular cyclization was performed by Glaser coupling reaction in pyridine/Cu(I)Br/N,N,N′,N″,N″‐pentamethyldiethylenetriamine system under room temperature, and tadpole‐shaped PS‐b‐(c‐PEO) was formed. The target copolymers and their intermediates were well characterized by size‐exclusion chromatography, proton nuclear magnetic resonance spectroscopy, and fourier transform infrared spectroscopy in details. The thermal properties was also determined and compared to investigate the influence of architecture on properties. The results showed that tadpole‐shaped copolymers had lower Tm, Tc, and Xc than that of their precursors of AB2 star‐shaped copolymers. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012  相似文献   

16.
We employ atomistic computer modeling to investigate the structure and morphology of poly(ethylene oxide) (PEO) chains confined in 1-nm slit pores defined by montmorillonite silicate layers. Molecular dynamics computer simulations reveal the Li+ cations to be located in the immediate vicinity of the silicate surfaces and PEO to adopt highly amorphous conformations in a liquidlike bilayer across the slit pores. Despite the orienting influence of the parallel stacked silicate walls, PEO shows no indication of crystallinity or periodic ordering; in fact, for all temperatures simulated, it is less ordered than the most disordered bulk PEO system. These amorphous PEO film configurations are attributed to the combination of severe spatial confinement and the strong coordination of ether oxygens with the alkali cations present in the interlayer gallery. These conclusions challenge the picture traditionally proposed for intercalated PEO, but they agree with a plethora of experimental observations. Indicatively, the simulation predictions are confirmed by wide-angle neutron scattering and differential scanning calorimetry experiments on PEO/montmorillonite intercalates. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 3285–3298, 2003  相似文献   

17.
Hydrophobically modified polyacrylamide (PAAm) was prepared by grafting PAAm with block copolymer of poly(ethylene oxide) and poly(propylene oxide), PEO‐PPO‐PEO, by melt method in the presence of benzoyl peroxide as initiator. The chemical structure of the graft copolymer was determined by FTIR and 1HNMR analyses. The surface tension, critical micelle concentration, and surface activities were determined at different temperatures. Surface parameters such as surface excess concentration (Γmax), the area per molecule at interface (Amin), and the effectiveness of surface tension reduction (ΠCMC) were determined at different temperatures from the adsorption isotherms of the prepared surfactants. The prepared surfactant was tested as emulsifier for water with xylene, cyclohexane, or petroleum crude oil synthetic emulsions. Copyright © 2010 John Wiley & Sons, Ltd.  相似文献   

18.
A novel amphiphilic branch‐ring‐branch tadpole‐shaped [linear‐poly(ε‐caprolactone)]‐b‐[cyclic‐poly(ethylene oxide)]‐b‐[linear‐poly(ε‐caprolactone)] [(l‐PCL)‐b‐(c‐PEO)‐b‐(l‐PCL)] was synthesized by combination of glaser coupling reaction with ring‐opening polymerization (ROP) mechanism. The self‐assembling behaviors of (l‐PCL)‐b‐(c‐PEO)‐b‐(l‐PCL) and their π‐shaped analogs of poly(ε‐caprolactone)/poly(ethylene oxide)]‐b‐poly(ethylene oxide)‐b‐[poly(ε‐caprolactone)/poly(ethylene oxide) with comparable molecular weight in water were preliminarily investigated. The results showed that the micelles formed from the former took a fiber look, however, that formed from the latter took a spherical look. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012  相似文献   

19.
The effects of the lamellar growth direction, extinction rings, and spherulitic boundaries of poly(butylene succinate) (PBSU) on the spherulitic growth of poly(ethylene oxide) (PEO) were investigated in miscible blends of the two crystalline polymers. In the crystallization process from a homogeneous melt, PBSU first developed volume‐filling spherulites, and then PEO spherulites nucleated and grew inside the PBSU spherulites. The lamellar growth direction of PEO was identical with that of PBSU even when the PBSU content was about 5 wt %. PEO, which intrinsically does not exhibit banded spherulites, showed apparent extinction rings inside the banded spherulites of PBSU. The growth rate of a PEO spherulite, GPEO, was influenced not only by the blend composition and the crystallization temperature of PEO, but also by the growth direction with respect to PBSU lamellae, the boundaries of PBSU spherulites, and the crystallization temperature of PBSU, TPBSU. The value of GPEO first increased with decreasing TPBSU when a PEO spherulite grew inside a single PBSU spherulite. Then, GPEO decreased when TPBSU was further decreased and a PEO spherulite grew through many tiny PBSU spherulites. This behavior was discussed based on the aforementioned factors affecting GPEO. © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 47: 539–547, 2009  相似文献   

20.
A versatile approach to control the localization of cellulose nanocrystal (CNC) in PLA/PA11 blends is presented. A PEO/CNC mixture with a high level of CNC dispersion is prepared through a combination of high pressure homogenization and freeze‐drying. The prepared PEO/CNC mixture is then incorporated into the PLA/PA11 blends using two different strategies. Typically for CNC/PLA/PA11, the CNCs selectively localize in PA11. However, PEO‐coated CNC particles segregate into PLA irrespective of whether the PEO/CNC mixture is premixed with PLA or PA11. It is suggested that a strong interaction between PEO and CNC particles combined with the PLA/PEO miscibility facilitates the localization of PEO‐coated CNC in the PLA. The localization of PEO‐coated CNC in the PLA has no effect on the morphology of the PLA‐5PEO/PA11 with matrix/dispersed phase form. However, 2 wt % PEO‐coated CNC in the co‐continuous (PLA‐5PEO)/PA11 50/50 vol % blend diminishes the phase thickness from 11 ± 1 to 4 ± 1.5 μm. This is attributed to a retarded relaxation of the PLA phase. This work outlines a strategy to control the CNC localization into a given polymeric phase in a binary polymer–polymer mixture. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2018 , 56, 576–587  相似文献   

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