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1.
Well‐defined amphiphilic A8B4 miktoarm star copolymers with eight poly(ethylene glycol) chains and four poly(ε‐caprolactone) arms (R‐8PEG‐4PCL) were prepared using “click” reaction strategy and controlled ring‐opening polymerization (CROP). First, multi‐functional precursor (R‐8N3‐4OH) with eight azides and four hydroxyls was synthesized based on the derivatization of resorcinarene. Then eight‐PEG‐arm star polymer (R‐8PEG‐4OH) was prepared through “click” reaction of R‐8N3‐4OH with pre‐synthesized alkyne‐terminated monomethyl PEG (mPEG‐A) in the presence of CuBr/N,N,N′,N″,N″′‐ pentamethyldiethylenetriamine (PMDETA) in DMF. Finally, R‐8PEG‐4OH was used as tetrafunctional macroinitiator to prepare resorcinarene‐centered A8B4 miktoarm star copolymers via CROP of ε‐caprolactone utilizing Sn(Oct)2 as catalyst at 100 °C. These miktoarm star copolymers could self‐assemble into spherical micelles in aqueous solution with resorcinarene moieties on the hydrophobic/hydrophilic interface, and the particle sizes could be controlled by the ratio of PCL to PEG. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013, 51, 2824–2833.  相似文献   

2.
Layered ZnO microspheric particles were prepared by the thermal decomposition of layered hydrozincite (LZnHC), which was synthesized from zinc nitrate and urea in a water/PEG400 mixture. The influence of the starting reagents, their concentrations, and the amount of PEG in the water/PEG400 mixture on the particle growth was observed. The chemical aspect of the particle growth was proposed in the frame of the partial charge model (PCM), and the formation of [Zn(OH)2(OH2)4]0 and [Zn(OH)(HCO3)(OH2)3]0 was predicted for the solid phase. The assumed growth mechanism, which follows the “nonclassical crystallization” concept of a self‐assembling mechanism, was observed in situ by small‐angle X‐ray scattering (SAXS) and predicts the rapid formation of approximately 6 nm sized building units. The size of these nano building units, stable only in the reaction medium, remains nearly constant during the synthesis, as the concentration of the nano building units increases throughout the reaction. The nano building units connect into leaves of LZnHC with a thickness of 20 nm. These leaves of LZnHC are further agglomerated into porous, microsphere‐like particles with sizes up to 4 μm.  相似文献   

3.
Poly(oxyethylene‐H‐phosphonate)s (POE‐H‐Ps), with different poly(oxyethylene) segment lengths, were synthesized via conventional two‐stage polycondensation reaction of dimethyl‐H‐phosphonate and poly(ethylene glycols) (PEGs), with nominal molecular weights of 400, 600, and 1000 Da. The changes in the composition of the reaction mixtures during the polycondensation process were followed by size‐exclusion chromatography (SEC) and NMR. It was found that the three PEG fragments yield reproducibly POE‐H‐Ps with the following molecular weights: ~3000 Da (PEG‐400), ~6000 Da (PEG‐600), and ~10,000 Da (PEG‐1000) as measured by SEC, NMR, and VPO. The hydrolytic behavior of POE‐H‐Ps upon storage and in aqueous media with pH 3, 7.4, and 8 was studied for the first time by a combination of NMR and SEC. It was found that the long‐term stability of the polymers in dry state depends on the length of the PEG fragments and decreased in the following order: POE‐H‐P(PEG‐1000) > POE‐H‐P(PEG‐600) > POE‐H‐P(PEG‐400). The hydrolytic transformation of the polymers in aqueous media is affected mostly by the pH of the solution. The degradation products are PEG fragments containing phosphonate end groups—an important prerequisite for the usage of the POE‐H‐Ps as nontoxic drug delivery vehicles and in vivo precursors for PEGylated prodrugs. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 4130–4139, 2008  相似文献   

4.
Palladium‐supported catalysts are complex assemblies with a challenging preparation. Minor changes in their preparation conditions can affect the activity, selectivity and lifetime of these catalysts. PdCuFe nanoparticle (NP) thin films were supported on reduced graphene oxide (RGO) by the reduction of the organometallic complex [PdCl2‌(cod)] (cod = cis ,cis ‐1,5‐cyclooctadiene), and [Cu(acac)2] and [Fe(acac)3] (acac = acetylacetonate) complexes at a toluene–water interface. We have investigated the application of the liquid–liquid interface method for preparing ultrathin films of catalysts and have evaluated the catalytic activity of the prepared NPs for the Sonogashira coupling reaction in micelle media. Also, we have investigated the effect of the addition of iron on the morphology, size and catalytic activity of PdCu/RGO NPs. Our study shows that both of the prepared catalysts (PdCu/RGO and PdCuFe/RGO) are efficient and recoverable catalysts for the Sonogashira carbon–carbon coupling reaction. This method has advantages compared to other routes, such as short reaction times, high to excellent yields, facile and low‐cost method for the preparation of the catalysts, and easy separation and reusability of the catalysts.  相似文献   

5.
Epoxide and aldehyde end‐functionalized poly(ethylene glycol)s (PEGs) (Mw = 400, 1000, 3400, 5000, and 20,000) were grafted to poly(ethylene terephthalate) (PET) film substrates that contained amine or alcohol groups. PET‐PAH and PET‐PEI were prepared by reacting poly(allylamine) (PAH) and polyethylenimine (PEI) with PET substrates, respectively; PET‐PVOH was prepared by the adsorption of poly(vinyl alcohol) (PVOH) to PET substrates. Grafting was characterized and quantified by the increase of the intensity of the PEG carbon peak in the X‐ray photoelectron spectra. Grafting yield was optimized by controlling reaction parameters and was found to be substrate‐independent in general. Graft density consistently decreased as PEG chain length was increased. This is likely due to the higher steric requirement of higher molecular weight PEG molecules. Water contact angles of surfaces containing long PEG chains (3400, 5000, and 20,000) are much lower than those containing shorter PEG chains (400 and 1000). This indicates that longer PEG chains are more effective in rendering surfaces hydrophilic. Protein adsorption experiments were carried out on PET‐ and PEG‐modified derivatives using collagen, lysozyme, and albumin. After PEG grafting, the amount of protein adsorbed was reduced in all cases. Trends in surface requirements for protein resistance are: surfaces with longer PEG chains and higher chain density, especially the former, are more protein resistant; PEG grafted to surfaces containing branched or network polymers is not effective at covering the underlying substrate, and thus does not protect the entire surface from protein adsorption; and substrates containing surface charge are less protein‐resistant. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 5389–5400, 2004  相似文献   

6.
Atom transfer radical emulsion polymerization of styrene using PEG‐Cl as macroinitiator under microwave irradiation was successfully conducted and monodispersed nanoparticles were prepared. The PEG‐Cl macroinitiator was synthesized, and confirmed by FTIR spectrum. The structure of the PEG‐b‐PSt diblock copolymer was characterized by 1H‐NMR and the number of styrene unit in the diblock copolymer was calculated. The morphology, size, and size distribution of the nanoparticles were characterized by transmission electron microscope (TEM) and photon correlation spectroscopy (PCS). The effects of the ratio of macroinitiator and monomer, the ratio of catalyst and macroinitiator on the size and size distribution of nanoparticles were investigated. It was found that the diameters of PEG‐b‐PSt nanoparticles prepared under microwave irradiation were smaller (<50 nm) and more monodispersed than those prepared with conventional heating. Moreover, with the increasing of the ratio of St/PEG‐Cl, the hydrodynamic diameters (Dh) of the nanoparticles increased and the poly index decreased, both Dh and poly index of the nanoparticles prepared under microwave irradiation were smaller then those prepared with conventional heating; as the concentration of catalyst increased, the Dh of the nanoparticles decreased and the poly index of the nanoparticles increased. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 481–488, 2008  相似文献   

7.
A photoresponsive microgel is designed by the combination of a noncovalent assembly strategy with a covalent cross‐linking method. End‐functionalized poly(ethylene glycol) with azobenzene [(PEG‐(Azo)2)] was mixed with acrylate‐modified β‐CD (β‐CD‐MAA) to form photoresponsive inclusion complex through host–guest interaction. The above photoresponsive complex was cross‐linked by thiol‐functionalized PEG (PEG‐dithiol) via Michael addition click reaction. The photoreversibility of resulted microgel was studied by TEM, UV–Vis spectroscopy, and 1H NMR measurements. The characterization results indicated that the reversible size changes of the microgel could be achieved by alternative UV–Vis irradiations with good repeatability.  相似文献   

8.
Copper‐catalyzed azide‐alkyne cycloaddition (CuAAC) was used to prepare glycosylated polyethylene (PE)–poly(ethylene glycol) (PEG) amphiphilic block copolymers. The synthetic approach involves preparation of alkyne‐terminated PE‐b‐PEG followed by CuAAC reaction with different azide functionalized sugars. The alkyne‐terminated PE‐b‐PEG was prepared by etherification reaction between hydroxyl‐terminated PE‐b‐PEG (Mn ~ 875 g mol?1) and propargyl bromide and azidoethyl glycosides were prepared by glycosylation of 2‐azidoethanol. Atmospheric pressure solids analysis probe‐mass spectrometry was used as a novel solid state characterization tool to determine the outcome of the CuAAC click reaction and end‐capping of PE‐b‐PEG by the azidoethyl glycoside group. The aqueous solution self‐assembly behavior of these amphiphilic glycosylated polymers was explored by TEM and dye solubilization studies. Carbohydrate‐bearing spherical aggregates with the ability to solubilize a hydrophobic dye were observed. The potential of these amphiphilic glycosylated polymers to self‐assemble via electro‐formation into giant carbohydrate‐bearing polymersomes was also investigated using confocal fluorescence microscopy. An initial bioactivity study of the carbohydrate‐bearing aggregates is furthermore presented. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013 , 51, 5184–5193  相似文献   

9.
Surface enrofloxacin‐imprinted magnetic nanoparticles were prepared for the selective recognition and fast separation of fluoroquinolones in human serum by surface‐initiated reversible addition fragmentation chain transfer polymerization. The surface morphology and imprinted behavior were investigated and optimized. The living/controlled nature of reversible addition‐fragmentation chain transfer polymerization reaction allowed the successful construction of well‐defined imprinted polymer layer outside the Fe3O4 core. Such molecularly imprinted polymers exhibited superparamagnetic properties and specific recognition toward fluoroquinolones. Combined with reversed‐phase high‐performance liquid chromatography, the prepared molecularly imprinted polymers were used for the selective enrichment and analysis of fluoroquinolones in human serum samples. The recoveries of four fluoroquinolones were 86.8–95.3% with relative standard deviations of 2.0–6.8% (n  = 3). Such magnetic molecularly imprinted polymers have great prospects in the separation and enrichment of trace analysts in complex biological samples.  相似文献   

10.
The diene‐based polymer nanoparticles represented by poly(butadiene‐co‐acrylonitrile) were prepared in the semibatch emulsion polymerization system using Gemini surfactant (GS) trimethylene‐1,3‐bis(dodecyldimethylammonium bromide) as the emulsifier. The nanoparticles within the range of 17–54 nm were achieved with narrow molecular weight and particle size distributions. A spherical morphology was observed for the produced nanoparticles. The effects of GS concentration on the particle size, molecular weight, polymerization conversion and solid content, and composition of copolymer were investigated. The semibatch process using monomeric and conventional surfactant sodium dodecyl sulfate (SDS) was compared. At the second stage of this study, the prepared unsaturated nanoparticles were employed as the substrates for the latex hydrogenation in the presence of Wilkinson's catalyst, that is, RhCl(P(C6H5)3)3. The effects of the particle size and catalyst concentration on the latex hydrogenation rate were investigated. The particle size is found to have a significant effect on the reaction rate. When the 17‐nm nanoparticles were used as the substrates, a high conversion of 95 mol % was obtained within 18 h using only 0.1 wt % RhCl(P(C6H5)3)3. The latex hydrogenation process was completely free of organic solvents. The present synthesis and following “green” hydrogenation process can be extended to latices made from semibatch emulsion containing other diene‐based polymers. This study shows great promise for decreasing the demanded quantity of expensive catalyst and eliminating the organic solvent in the hydrogenation process. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012  相似文献   

11.
A simple and fast synthetic route to ultra‐highly concentrated silver nanoparticles with long‐term stability by reducing AgNO3 with ascorbic acid in the presence of polyethyleneimine (PEI) as a stabilizer in an aqueous phase is reported. The concentration of silver precursor was as high as 2000 mm (200 g of Ag nanoparticle per liter of water) and the reaction time was less than 10 min. The resulting silver nanoparticles show long‐term stability after two months of storage at room temperature without any signs of particle aggregation or precipitation in an aqueous phase. The successful ligand exchange of PEI‐stabilized silver nanoparticles to polyethylene glycol (PEG) and polyvinylpyrrolidone (PVP) without particle aggregation is also demonstrated. In addition, the catalytic activities of silver nanoparticles stabilized by various stabilizers prepared by the ligand exchange method was investigated. The PEI‐stabilized silver nanoparticles exhibited a higher stability than those of PEG‐ and PVP‐stabilized silver nanoparticles in the diffusion‐controlled catalytic reduction of 4‐nitrophenol to 4‐aminophenol by NaBH4.  相似文献   

12.
In this research, the headspace solid‐phase microextraction (SPME) coupled with GC flame ionization detector was applied for the determination of some monocyclic aromatic amines in real water and urine samples. A sol–gel technique was applied for the preparation of the SPME fibers. Two different sol–gel coatings, (PEG and poly(ethylene glycol) modified with multi‐walled carbon nanotubes [PEG/CNTs]), were prepared and compared. Extraction efficiency of PEG/CNTs was better than PEG fiber in the same conditions. To obtain maximum extraction efficiency, some parameters such as desorption temperature and time, temperature and time of extraction, salt effect, pH, and stirring speed were investigated and optimized for PEG/CNTs fiber. Under optimized conditions, the LODs (S/N = 3) were in the range of 0.5–50 ng/L and limits of quantification (S/N = 10) were between 1 and 500 ng/L. Repeatability (n = 5) was in the range of 3.2–9.1% and reproducibility (n = 3) was obtained from 5.5 to 12.0%. The method was successfully applied to the analysis of real water and urine samples with recoveries from 63.7 to 97.0%.  相似文献   

13.
High loading of stable carbon black (CB) dispersion in organic solvent, PGMEA, was prepared by a ball‐milling process when using poly(styrene‐EHA‐HEMA)‐block‐poly(styrene‐EHA‐HEMA‐DMAEMA) (P(SEH)‐b‐P(SEHD)) as a dispersant. The P(SEH)‐b‐P(SEHD) containing P(SEH) as a steric chain and P(SEHD) as an anchoring chain was prepared by TEMPO‐mediated polymerization. The tertiary amine group of DMAEMA in P(SEHD) chain could be adsorbed onto CB by the interaction with the carboxylic acid group on surface of CB and the P(SEH) chain could provide sufficiently steric repulsion force to avoid the aggregation of CB. In addition, a photosensitive dispersant, P(SEH)‐b‐P(SEHD)C?C, containing the methacrylate double bond side group was also synthesized and was used to prepare stable CB dispersion in PGMEA. The effects of the molecular weight between steric and anchoring chains, the content of tertiary amine, and the amount of methacrylate double bond in the dispersant on the particle size of CB were investigated. Furthermore, the influences of various surface properties of CB, such as specific surface area, content of carboxylic acid group, and size of primary particle, on the particle size of CB in dispersion were also discussed. Finally, the photosensitivity of P(SEH)‐b‐P(SEHD)C?C/CB composite was monitored by a photodifferential scanning calorimeter. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 6185–6197, 2008  相似文献   

14.
The reaction of three types of carbon nanofibers (CNFs; platelet: CNF‐P, tubular: CNF‐T, herringbone: CNF‐H) with Ir4(CO)12 in mesitylene at 165 °C provided the corresponding CNF‐supported iridium nanoparticles, Ir/CNFs (Ir content=2.3–2.6 wt. %). Transmission electron microscopy (TEM) studies of these Ir/CNF samples revealed that size‐controlled Ir nanoparticles (average particle size of 1.1–1.5 nm) existed on the CNFs. Among the three Ir/CNF samples, Ir/CNF‐T showed an excellent catalytic activity and chemoselectivity towards hydrogenation of functionalized nitroarenes and imines; the corresponding aniline derivatives were obtained with high turnover numbers at ambient temperature under 10 atm of H2, and the catalyst is reusable. Ir/CNF‐T was also effective for the reductive N‐alkylation of anilines with carbonyl compounds.  相似文献   

15.
An efficient and environmentally friendly procedure for the one-pot synthesis of tetrahydropyrimidinones from aldehydes, β-diketones and urea/thiourea by using magnesium bromide as an inexpensive and easily available catalyst under solvent-free conditions was described. Compared with the classical Biginelli reaction conditions, this new method has the advantage of good to excellent yields (74%-94%) and short reaction time (45-90 min). The structure of the Biginelli reaction product from β-diketone, salicylaldehyde and urea has been proposed to possess an oxygen-bridge by cyclization (intramolecular Michael-addition).  相似文献   

16.
Liquid phase hydrogenolysis of ethyl lactate to 1,2‐propanediol was performed over silica supporting cobalt catalysts prepared by two different methods: precipitation‐gel (PG) technique and deposition‐precipitation (DP) procedure. The cobalt species (Co3O4/cobalt phyllosilicate) present in the corresponding calcined PG and DP catalysts were different as a consequence of the preparation methods, and Co OH Co olation and Si O Co oxolation molecular mechanisms were employed to elucidate the chemical phenomena during the different preparation procedures. In addition, the texture (BET), reduction behavior (TPR and in‐situ XRD), surface dispersion and state of cobalt species (XPS), and catalytic performance differ greatly between the samples. Because of small particle size, high dispersion of cobalt species and facile reducibility, the Co/SiO2 catalyst prepared by precipitation‐gel method presented a much higher activity than the catalyst prepared by deposition‐precipitation method. Metallic cobalt is assumed to be the catalytically active site for the hydrogenolysis reaction according to the catalytic results of both cobalt samples reduced at different temperatures and the structure changes after reaction.  相似文献   

17.
TiO2 nanocrystalline films were prepared from titanium tetra-n-butoxide modified with double hydrolysis inhibitors, acetylacetone and polyethylene glycol (PEG), in mixture of methanol and ethanol. The correlation among surface structure of the TiO2 films, preparation conditions, and photovoltaic properties of the solar cells using the TiO2 films was investigated. The particle size of the obtained TiO2 films was decreased as the PEG content increased. The nanostructured films with the narrow distribution of particle size could be prepared. The amounts of adsorbed dyes for these TiO2 films were larger than that without PEG. The performance of the solar cell fabricated using the TiO2 film improved as the amount of the PEG increased, and the solar cell using the TiO2 film prepared from the solution with 30 wt% PEG exhibited the highest performance.  相似文献   

18.
Several new macroinitiators and macromerinitiators (macroinimers) were synthesized and evaluated for the bulk polymerization of sytrene at 60°C. Macroinitiators were prepared from the reaction of 4,4′-dicyano-4,4′ azovaleryl chloride ( 1 ) with poly(ethylene glycol) (PEG) with a Mω of 400 and with either benzoyl chloride, acetyl chloride, phenyl isocyanate, or poly(ethylene glycol) oleyl ether. Macromer initiators were also prepared from the reaction of 1 with PEG having Mω values of 200, 400, 600, 1000, or 1500 and with 4-vinylbenzyl chloride. The bulk polymerization of styrene by macroinimers gave crosslinked styrene-PEG block copolymers, while the polymerization by macroinitiators gave soluble copolymers. The molecular weights of the styrene-PEG block copolymers obtained with macroinitiators having either oleyl, benzoyl, or phenyl urethane end groups were 22000–29000 g/mol. DSC measurements showed that the crosslinked block copolymers had crystalline PEG units with melting transitions ranging from 11–37°C. © 1994 John Wiley & Sons, Inc.  相似文献   

19.
Polymeric nanospheres consisting of poly(methyl methacrylate) (PMMA) cores and poly(ethylene glycol) (PEG) branches on their surfaces were prepared by free radical copolymerization of methyl methacrylate (MMA) with PEG macromonomers in ethanol/water mixed solvents. PEG macromonomers having a methacryloyl (MMA‐PEG) and p‐vinylbenzyl (St‐PEG) end group were used. It has become clear that the obtained polymer dispersions form three kinds of states, particle dispersion (milky solution), clear solution, and gel/precipitation. It was found that the reaction parameters such as MMA concentration, molecular weight, and concentration of PEG macromonomers, and water content can affect nanosphere formation in a copolymerization system. The water volume fraction of mixed ethanol/water solvents affected the particle size of the nanospheres. These differences in the formation of nanospheres were due to the solvophilic/solvophobic balance between the copolymers and solvents during the self‐assembling process of the copolymers. The sizes of nanospheres can be controlled by varying concentration of PEG macromonomer and water content in solvents. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 1811–1817, 2000  相似文献   

20.
α‐Butyl ω‐N, N‐dihydroxyethyl aminopropylpolymethylhydrosiloxane (PDMS), a monotelechelic polydimethylsiloxane with a diol‐end group, which is used to prepare siloxane–urethane dispersion, was successfully synthesized. Then, novel silicone‐based polyurethane (PU)‐dispersion was prepared by the addition polymerization of hexamethylene diisocyanate, to PDMS, polyethylene glycol (PEG) and dimethylol propionic acid. The goal of this study was to explore the potential use of polysiloxane–urethane in marine coatings in order to boost the flexibility, adhesion, erosion and foul‐release property with respect to PDMS/PEG ratio (PDMS wt%). The PDMS was characterized by Fourier‐transform infrared (FT‐IR), proton nuclear magnetic resonance and carbon‐13 nuclear magnetic resonance spectroscopic techniques. The results showed that each step was successfully carried out and the targeted products were synthesized in all cases. The structural elucidation of the synthesized waterborne PU and waterborne polysiloxane–urethane (WBPSU) was carried out by FT‐IR spectroscopic technique. Thermal properties of the resins were studied by using thermogravimetric analysis and differential scanning calorimetry. The antifouling property of the coatings was investigated by the immersion test under a marine environment for 90 days. The fouled area was calculated for all the samples, and the fouled area (%) decreased with increasing PDMS content. After 90 days, the lowest fouled area (6%) was observed in the sample using WBPSU2 (PDMS 4.48 wt%) among all of the samples. Copyright © 2012 John Wiley & Sons, Ltd.  相似文献   

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