This paper presents the synthesis and characterization of d ‐fructose modified poly(ethylene glycol) (Fru‐PEG) and fructose modified poly(ethylene glycol)‐block‐poly(ethyl hexyl glycidyl ether) (Fru‐PEG‐b‐PEHG) that are both prepared by initiation with isopropyliden protected fructose, followed by deprotection of the sugar. The block copolymers are self‐assembled into micelles, and are subsequently characterized by cryo‐TEM and dynamic light scattering. The fluorescent dye Nile red is encapsulated as a model hydrophobic compound and fluorescent marker to perform initial uptake tests with breast cancer cells. The uptake of sugar and nonsugar decorated micelles is compared. 相似文献
The properties of track membranes (TM) based on poly(ethylene terephthalate) (PETP) and polypropylene (PP) and modified by
radiation-induced graft polymerization of 2-methyl-5-vinylpyridine (MVP) andN-isopropylacrylamide (NIPAA) were studied. The rate of grafting and the limiting degree of grafting increase linearly as the
pore diameter of TM increases. The gasdynamic and hydrodynamic pore diameters of modified TM were determined. The dependence
of water permeability of TM modified by grafting with poly(2-methyl-5-vinylpyridine) (PMVP) on the degree of grafting passes
through a maximum, which, according to the data of wetting angle measurements, corresponds to the maximum hydrophilicity.
The negative χ-potential of TM changes sign after modification by grafting with PMVP. Thermosensitive TM based on PETP and
PP were prepared by radiation-induced graft polymerization of NIPAA. The structure of modified TM was studied by electron
microscopy and atomic force microscopy.
Translated fromIzvestiya Akademii Nauk, Seriya Khimicheskaya, No. 5, pp. 858–864, May, 2000. 相似文献
Poly(ethylene terephthalate) (PET)/montmorillonite (MMT) nanocomposite was prepared by the direct polymerization with MMTs modified with variable content of antimony acetate (Sb(OAc)3), which was also used as catalyst polymerization. The modified MMTs (AS‐Sb‐MMT) were prepared by intercalating both Sb(OAc)3 and amphoteric surfactant (AS) into MMT layers. Nine kinds of Sb‐MMTs [MMT treated with Sb(OAc)3] with different Sb content were obtained, but only six kinds of PET/MMT nanocomposites could be prepared. ICPAES was used to characterize Sb content of modified MMT, XRD was used to characterize interlayer spacing, IR spectroscopy was used to characterize composition change of Sb catalyst in modified MMT and TEM was used to investigate micromorphology of PET/MMT nanocomposites. Several results are obtained, i.e., (a) Sb content of Sb‐MMT is affected by both drying temperature and washing‐drying sequence, (b) compared with Na‐MMT (unmodified MMT), the change in the interlayer spacing of Sb‐MMT is attributed to the solvent ethylene glycol (EG) rather than the intercalated or absorbed Sb(OAc)3, (c) based on this, a model is developed to describe the swelling of Na‐MMT and modified MMT by EG and the effect of drying temperature on the interlayer spacing, (d) exfoliation state of MMT in PET matrix of nanocomposites is controlled not only by Sb content and interlayer spacing, but also by the composition of Sb catalyst in modified MMT. 相似文献
In co[poly(ethylene terephthalate)-p-oxybenzoate] containing 30 mole % oxybenzoate units, the ethylene terephthate units crystallize. The copolymer melts in the temperature range 180–210°C to form a nematic phase which, at a higher temperature, transforms to an isotropic liquid. The latent heat of the first transition is 5 cal/g, and the thermodynamic melting temperature, 247°C, is essentially that expected for a random copolymer of this composition. The nematic → isotropic transition occurs at 244°C, with an enthalpy change of 3.2 cal/g (10% of the heat of fusion of poly(ethylene terephthalate)). We conclude that semiflexible polymers form a nematic phase which is rather highly disordered. The model of the nematic phase treated by Flory is modified to increase its entropy through incorporation of chain bends (which must be correlated in position and direction with those in neighboring molecules). This increases the chain extension, as measured by the fraction (1–f) of collinear chain bonds, required to form the nematic phase. For binary polymer-solvent systems, an appropriate scaling of f values leaves the phase diagram as predicted by Flory's treatment essentially unchanged. 相似文献
Surfaces of commercial polyurethanes (PUs) were modified by poly(ethylene oxide) (PEO) grafting and/or heparin immobilization or sulfonation to investigate the effect to antithrombogenicity. The hydrophilicity of the modified PUs surface was significantly increased. All the PEO-grafted PU surfaces displayed very little platelet adhesion and activation. The coupled heparin or sulfonate at the end of PEO exhibited anticoagulant activity to extend APTT. Lowering in vitro platelet adhesion of modified PUs led to a prolongation in the ex vivo occlusion time. In particular, the sulfonated PU-PEO surface showed the most enhanced blood compatibility due to the synergistic effects of PEO and SO3 groups. 相似文献
The surface free energy of modified silica fillers and poly(ethylene terephthalate) (PET) fibers was analyzed by inverse
gas chromatography in order to investigate the relationship between their surface characteristics and the performance of the
composite formed from these materials. The adsorption isotherms of n-heptane and 1-propanol were determined by the elution-peak-maximum method. The dispersive and polar components of the surface
free energy were determined by use of the Young–Dupré equation and the Fowkes equation on the basis of the saturated spreading
pressure derived from the Gibbs adsorption equation. The acidity and the basicity of the surface were estimated by the specific
retention volume of each probe molecule with different donor number and acceptor number. It was found that the dispersive
component of the surface free energy for modified silica fillers was mostly lower than that for original silica filler. The
polar component of the surface free energy for ethylene glycol modified silica filler became large, while that for n-butanol modified silica filler decreased remarkably. It was also found that original silica filler exhibited high acidity,
while modified silica fillers exhibited low acidity. Although these methods have been applied to PET fibers, the surface free
energy could not be determined quantitatively because of the surface change during the pretreatment of PET fibers. It was
observed that the polar component of the surface free energy decreased when the pretreatment was made at a temperature higher
than the glass-transition temperature of PET. It became clear that the interaction between modified silica fillers and PET
fibers correlated well with the basicity of the fillers, but not with their acidity.
Received: 18 October 1999 Accepted: 8 February 2000 相似文献
This paper reports a novel enzyme‐immobilization method for the direct electron transfer (DET) reaction of ascorbate oxidase from Acremonium sp. HI‐25 (ASOM). ASOM was adsorbed onto a gold electrode modified with a self‐assembled monolayer (SAM) of alkanethiol derivatives and immobilized by a cationic polymer membrane and anionic ω‐carboxyalkanethiol combined system. The redox responses of the immobilized ASOM were investigated by cyclic voltammetry. We found that the DET reaction of ASOM was facilitated by this novel immobilization. On the other hand, the redox responses of poly(ethylene oxide) (PEO)‐modified ASOMs were also investigated. ASOM was modified with two types of PEO which possess straight chain‐shaped (PEO2000) or comb‐shaped conformation (PM67). As a result, the DET reactions of PEO‐modified ASOMs were also facilitated by this immobilization method. We concluded that this immobilization method is effective for promoting the DET reaction of ASOMs. 相似文献
Copolymers of styrene with vinylphenyl trifluoromethyl carbinol, p-vinylphenyl trifluoromethyl carbinol, vinylphenyl hexafluorodimethyl carbinol, and p-vinylphenol are conditionally compatible with poly(ethylene oxide), depending on their composition and blending ratios, whereas copolymers of styrene and vinylphenyl methyl carbinol are much less compatible with poly(ethylene oxide), as determined by Tg criteria and differential scanning calorimetry. The crystallinity of poly(ethylene oxide) is changed in the copolymer/poly(ethylene oxide) blends, as indicated by depressions of the poly(ethylene oxide) melting point. Hydrogen-bond formation has been studied in two selected blends by infrared (IR) spectroscopy. Hydrogen bonding dissociation and reassociation as a function of temperature are reported. The conformation changes of poly(ethylene oxide) in the blends, the interaction between copolymer and poly(ethylene oxide) as well as in the reference blend, polystyrene/poly(ethylene oxide), are also investigated. 相似文献
Inclusion complexes of poly(ethylene oxide) with α-cyclodextrin are the key compounds in the synthesis of polyrotaxanes. These
complexes prepared in aqueous solutions contain free cyclodextrin, which cocrystallizes with the major reaction product. These
complexes dissociate upon dissolution in DMF and DMSO to form cyclodextrin and pseudopolyrotaxanes with a low cyclodextrin
content. Polyrotaxane was synthesized with the use of poly(ethylene oxide)-α,ω-bis-amine as a linear component. The end-groups
of the polymer in the inclusion complex were modified by the reaction with 2,4-dinitrofluorobenzene. A procedure was developed
for purification of a polyrotaxane with high cyclodextrin content.
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Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 8, pp. 1914–1918, August, 2005. 相似文献
The bis(ethylene)ketal of p-benzoquinone ( 6 ) has been prepared from the bis(ethylene)ketal of cyclohexane-1,4-dione ( 3 ) by bromination with bromine in ether followed by dehydrobromination with potassium t-butoxide. Two intermediate dibromides ( 4 and 5 ) were isolated and their constitutions as well as their configurations determined from spectroscopic properties. Partial hydrolysis of 6 furnished the mono(ethylene)ketal of p-benzoquinone ( 9 ), which was converted stereospecifically to syn-bishomoquinone ( 2 ) by the double addition of sodium dimethylsulfoxonium-methylide. The intermediate mono(ethylene)ketals of syn-bishomoquinone ( 11 ) as well as of the mono(methylene) addition product ( 10 ) were also isolated. 相似文献
Summary: A tandem catalytic system, composed of (η5‐C5H4CMe2C6H5)TiCl3 ( 1 )/MMAO (modified methyl aluminoxane) and [(η5‐C5Me4)SiMe2(tBuN)]TiCl2 ( 2 )/MMAO, was applied for the synthesis of ethylene–hex‐1‐ene copolymers with ethylene as the only monomer stock. During the reaction, 1 /MMAO trimerized ethylene to hex‐1‐ene, while 2 /MMAO copolymerized ethylene with the in situ produced hex‐1‐ene to poly(ethylene–hex‐1‐ene). By changing the catalyst ratio and reaction conditions, a series of copolymer grades with different hex‐1‐ene fractions at high purity were effectively produced.
The overall strategy of the tandem 1 / 2 /MMAO catalytic system. 相似文献