Facilely dispersible magnetic nanoparticles prepared by a surface-initiated atom transfer radical polymerization

Facilely dispersible magnetic nanoparticles (Fe₃O₄) prepared by a surface-initiated atom transfer radical polymerization (ATRP) of poly (ethylene glycol) methyl ether monomethacrylate (PEGMA) are reported. The initiator of 2-bromoisobutyrate (BIB) for ATRP was immobilized onto the surface of Fe₃O₄ nanoparticles by the reaction between 2-bromoisobutyryl bromide (BIBB) and the hydroxyl group on the nanoparticles. The results indicated that the poly(poly(ethylene glycol) monomethacrylate) (PPEGMA) was successfully grafted onto the surface of the magnetic nanoparticles. The core-shell nanoparticles with particle size of ≈ 20 nm in water (about 20 mg/mL) are facilely dispersible and can be easily captured by a magnet with magnetic field of 2000 G.     

Surface-initiated atom transfer radical polymerization of methyl methacrylate from magnetite nanoparticles at ambient temperature

The synthesis of methyl methacrylate (MMA) brush from the surface of magnetite nanoparticles (core-shell structure), from initiator moieties anchored covalently to the nanoparticles, via room temperature atom transfer radical polymerization (ATRP) is described. The surface-initiated polymerization was carried out from a surface-confined initiator containing a 2-bromoisobutyrate moiety with Cu(I)Br/PMDETA catalytic system. The initiator moiety was covalently anchored to the nanoparticles via a two step modification reaction scheme. Controlled polymerization was observed if ethyl-2-bromoisobutyrate (2-EiBrB) was added as a free/sacrificial initiator. A linear increase of molecular weight and a narrow molecular weight distribution of the PMMA formed in solution, provide evidence for a controlled surface-initiated polymerization, leading to surface-attached polymer brushes under mild conditions. The grafted PMMA provides good stability and dispersibility for the nanoparticles in organic solvents.     

Synthesis of biomimetic poly[2-(methacryloyloxy)ethyl phosphorycholine]-coated magnetite nanoparticles via surface-initiated atom transfer radical polymerization

Modification of magnetite nanoparticles with biomimetic poly[2-(methacryloyloxy)ethyl phosphorycholine] (poly(MPC)) via surface-initiated atom transfer radical polymerization (ATRP) was carried out. Fourier transform infrared (FT-IR) spectroscopy, thermogravimetric analyses (TGA) and zeta potential studies indicated that well defined poly (MPC) was successfully grafted on the surface of magnetite nanoparticles. X-ray diffraction results showed the structure of magnetite nanoparticles after surface modification was not changed. The poly (MPC)-coated magnetite nanoparticles had a mean transmission electron microscopy (TEM) diameter of 11 +/- 1.5 nm. The resulting nanomaterials were superparamagnetic at room temperature, exhibited good colloidal stability in aqueous media and good responsibility to magnetic field. Such magnetite nanoparticles with biomimetic surface have potential application in prolonging circulation time in vivo.     

Synthesis of Fe3O4@PbS hybrid nanoparticles through the combination of surface-initiated atom transfer radical polymerization and acidolysis by H2S

A versatile approach to fabricate nanoparticles with multiple functionalities through the combined use of both surface-initiated ATRP and acidolysis by H2S techniques was demonstrated. The hybrid nanoparticles exhibited the core-shell structure having the magnetite nanoparticles as the core and the polymethacrylate as the shell with PbS nanoparticles distributing in the shell. The structure and morphology of the synthesized nanoparticles were characterized using Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD) and transmission electron microscopy (TEM). The optical and magnetic properties of the nanoparticles were investigated by UV-Vis spectroscopy, photoluminescence spectroscopy and vibrating sample magnetometer (VSM), respectively. It is observed that the absorption and emission behaviors of the Fe3O4@PbS hybrid nanoparticles were seriously influenced by the ATRP time and the reaction time with H2S. The saturated magnetization (Ms) decreased with the increase of ATRP time due to the formation of thicker shells coating on the surfaces of magnetite nanoparticles.     

电子转移活化再生催化剂原子转移自由基聚合(ARGET ATRP)的研究进展

ARGET ATRP可将反应中催化剂用量降至ppm级,是目前最具工业化应用前景的原子转移自由基聚合(ATRP)之一。综述了ARGET ATRP的反应机理、引发剂、催化体系、还原剂、反应条件及其在污水处理、纤维素改性、燃料电池方面的应用,并对ARGET ATRP技术的前景进行了展望。     

Poly(n-isopropylacrylamide)-based hydrogel coatings on magnetite nanoparticles via atom transfer radical polymerization

Core magnetite (Fe(3)O(4)) nanoparticles have been functionalized with a model intelligent hydrogel system based on the temperature responsive polymer poly(n-isopropyl acrylamide) (PNIPAAm) to obtain magnetically responsive core-shell nanocomposites. Fe(3)O(4) nanoparticles were obtained from a one-pot co-precipitation method which provided either oleic acid (hydrophobic) or citric acid (hydrophilic) coated nanoparticles. Subsequent ligand exchange of these coatings with various bromine alkyl halides and a bromo silane provided initiating sites for functionalization with NIPAAm using atom transfer radical polymerization (ATRP). The bromine alkyl halides that were used were 2-bromo-2-methyl propionic acid (BMPA) and 2-bromopropionyl bromide (BPB). The bromo silane that was used was 3-bromopropyl trimethoxysilane (BPTS). The intelligent polymeric shell consists of NIPAAm crosslinked with poly(ethylene glycol) 400 dimethacrylate (PEG400DMA). Fourier transform infrared (FTIR) spectroscopy, thermogravimetric analysis (TGA), and transmission electron microscopy (TEM) were used to confirm the presence of the polymeric shell. Dynamic light scattering (DLS) was used to characterize the nanocomposites for particle size changes with temperature. Their magnetic and temperature responsiveness show great promise for further biomedical applications. This platform for functionalizing magnetic nanoparticles with intelligent hydrogels promises to impact a wide range of medical and biological applications of magnetic nanoparticles.     

Template guided self-assembling two-dimensional array of Au@SiO2 core-shell nanoparticles for room-temperature single electron transistors

The composite nanoparticles of a gold core capped by a SiO2 shell with well-controlled thickness have been synthesized and fabricated into two-dimensional array on silicon surface by a simple self-assembly method combined with an AFM nanolithography technique. Current-voltage measurements of the Au@SiO2 composite nanoparticles (shell thickness of 6 nm) show a well-pronounced Coulomb staircase with a period of 300 mV at room temperature, demonstrating single electron transistor behavior. The step width of the Coulomb staircase can be tuned by controlling the thickness of SiO2 shell. The tunable single electron tunneling properties make the 2D array of Au@SiO2 composite nanoparticles an ideal candidate for planar single electron transistor devices.     

Detection of DNA point mutation by atom transfer radical polymerization

We report here a new DNA detection method in which polymer growth in atom transfer radical polymerization (ATRP) is used as a means to amplify detection signals. In this method, DNA hybridization and ligation reactions led to the attachment of ATRP initiators on a solid surface where specific DNA sequences were located. These initiators subsequently triggered the growth of poly(hydroxyethyl methacrylate) (PHEMA) at the end of immobilized DNA molecules and formed polymer brushes. The formation of PHEMA altered substrate opacity, rendering the corresponding spots readily distinguishable to the naked eye. A second ATRP reaction to form branched polymers on the surface drastically improved the visibility of DNA hybridization and significantly shortened the detection time. The resulting polymer film was characterized using infrared spectroscopy, ellipsometry, contact angle measurements, and atomic force microscopy. Direct visualization of 1 fmol of target DNA molecules of interest was demonstrated. A proof-of-principle experiment to detect DNA point mutation was conducted. The perfectly matched DNA targets were distinctively differentiated from those with mutations. The demonstrated capability to detect DNA mutation with direct visualization laid the groundwork for the future development of detector-free testing kits in single-nucleotide polymorphism screenings.     

Synthesis of thermoresponsive silica nanoparticle/PNIPAM hybrids by aqueous surface-initiated atom transfer radical polymerization

This paper described the synthesis of a novel kind of thermoresponsive silica nanoparticle/PNIPAM hybrids by aqueous surface-initiated atom transfer radical polymerization at room temperature. These resulting hybrid particles were characterized by FT-IR, XPS, TEM, TGA and variable temperature DLS which indicated that they owned both core/shell structures and thermoresponsiveness.     

ATRP法制备聚甲基丙烯酸2,2,2-三氟乙酯-b-聚苯乙烯嵌段共聚物的研究

用α-溴代丙酸乙酯(EPN-B)/氯化亚铜(CuCl)/联二吡啶(bpy)作为ATRP催化引发体系,环己酮为溶剂,进行甲基丙烯酸2,2,2-三氟乙酯(TFEMA)的原子转移自由基聚合(ATRP),得到单分散PTFEMA-X预聚体.并以此预聚体为大分子引发剂引发苯乙烯聚合,得到分子质量可控、分子质量分布窄的聚甲基丙烯酸2,2,2-三氟乙酯-b-聚苯乙烯嵌段共聚物,考察了大分子引发剂的分子质量、配位剂等对聚合过程的影响.并用1H-NMR、FTIP、GPC、DSC等时产物的结构与性能进行了表征.     

Preparation of polymer nanocomposites of core-shell structure via surface-initiated atom transfer radical polymerizations

Polymer nanocomposites of core-shell structure were prepared by grafting poly(tert-butyl acrylate) (Pt-BA) from SiO₂ nanoparticle via the surface-initiated polymerization (SIP) strategy. This new organic inorganic hybrid particle has been extensively characterized by XPS (X-ray Photoelectron Spectroscopy), SEM (Scanning Electron Microscopy), TEM (Transmission Electron Microscopy), and TGA (ThermoGravimetric Analysis).     

Fabrication of hollow polyelectrolyte nanospheres via surface-initiated atom transfer radical polymerization

Novel polyelectrolyte-grafted core-shell organic/inorganic hybrid nanospheres which possess hard backbone of silica nanoparticles and soft shell of cross-linked poly(ionic liquids) (PILs) have been synthesized via a surface-initiated atom transfer radical polymerization (SI-ATRP). After removal of the core templates of the core-shell nanospheres, nearly monodispersed hollow polyelectrolyte nanospheres were obtained. Various characterization techniques including FT-IR, XPS, and TEM were used to characterize the resulting core-shell and hollow polyelectrolyte nanospheres. The results showed that the hollow nanosphere has a hollow core of an average diameter of ca. 200 nm with a shell thickness of ca. 25 nm. The obtained hollow polyelectrolyte nanospheres could be applied in release-control systems.     

ATRP表面接枝在功能膜制备中的应用

ATRP表面引发接枝聚合是功能膜制备中一个重要而有效的方法.近年来,随着原子转移自由基聚合(ATRP)研究的快速发展,将ATRP应用于功能膜制备的研究已取得了显著的进展.详细介绍了在膜表面固定ATRP引发剂的方法及将ATRP表面接枝法应用于制备抗污染能力强,抗菌性好,环境响应迅速等多种功能性膜方面的研究进展情况.     

Chemical stabilization of gold coated by silver core-shell nanoparticles via electron transfer

Silver nanoparticles are notoriously susceptible to oxidation, yet gold nanoparticles coated in silver exhibit a unique electronic interaction that occurs at the interface of the two metals, leading to enhanced stability properties for the silver shell. In order to probe the phenomenon, the stability of gold nanoparticles coated by silver was studied in the presence of various chloride-containing electrolytes. It was found that a critical silver shell thickness of approximately 1 nm exists that cannot be oxidatively etched from the particle surface: this is in contrast to the observation of complete oxidative etching for monometallic silver nanoparticles. The results are discussed in terms of particle composition, structure and morphology before and after exposing the particles to the electrolytes. Raman analysis of the reporter molecule 3-amino-1,2,4-triazole-5-thiol adsorbed on the particle surface illustrates the feasibility of using gold coated by silver nanoparticle probes in sensing applications that require the presence of high levels of salt. The results provide insight into the manipulation of the electronic and stability properties for gold- and silver-based nanoparticles.     

乙基纤维素接枝偶氮苯聚合物的合成与研究

通过原子转移自由基聚合(ATRP)技术合成乙基纤维素接枝偶氮苯聚合物.以功能化乙基纤维素作为大分子引发剂,在CuBr/N,N,N′,N″,N″-五甲基二亚乙基三胺(PMDETA)催化体系下,以苯甲醚为溶剂,引发对甲氧基偶氮苯单体6-[4-(4-甲氧基苯基偶氮)酚氧基]己基甲基丙烯酸酯(MMAzo)的ATRP反应,构筑接枝共聚物.通过多种手段接枝共聚物结构、热行为与液晶性进行表征.接枝共聚物在紫外-可见光照射下发生可逆的顺反异构化反应,具有作为光学材料的潜力.     

Based on atom transfer radical polymerization method preparation of fluoropolymer superhydrophobic films

A facile process for the one-step preparation of a fluoropolymer superhydrophobic polymer-coated surface under an ambient atmosphere was reported in this study. The block copolymer of polystyrene-block-poly (2,2,3,4,4,4-hexafluorobutyl-methacrylate), synthesized by atom transfer radical polymerization, was dissolved in a selective solvent. With the evaporation of the solvent, the block copolymer self-assembled into core/shell micelles, forming a grain-structured superhydrophobic film. The contact angle and sliding angle of the film were measured as 152.3° and 9.2°, respectively, demonstrating excellent superhydrophobic property and stability. The superior performance should ascribe to the introducing fluorine into the copolymer and the grain-like rough morphology of the film.     

原子转移自由基聚合用于聚砜膜的疏水改性研究

利用原子转移自由基聚合(ATRP)方法,将疏水单体2,2,2-三氟乙基甲基丙烯酸酯(TFEMA)接枝到氯甲基化聚砜(CMPSF)材料上,得到不同反应时间的接枝共聚物PSF-g-PTFEMA,并用FT-IR、19F-NMR对产物的结构进行了表征。最后,采用涂覆法对PSF膜表面进行改性,通过测定涂覆后的膜表面静态水接触角,考察了接枝产物对膜的疏水性能的影响。     

Synthesis and self-assembly of pH-responsive chitosan graft copolymer by the combination of atom transfer radical polymerization and click chemistry

Amphiphilic chitosan-graft-poly(2-(N,N-diethylamino)ethyl methacrylate)-block-poly(ethylene oxide) (CS-g-(PDEAEMA-b-PEO)) copolymer was synthesized by the combination of atom transfer radical polymerization (ATRP) and click chemistry. The copolymer was characterized by ¹H NMR spectrum. The self-assembly and pH-responsive properties of CS copolymer were investigated by TEM, DLS, and transmittance in water. The micelle sizes can be adjusted through the alteration of the pH values of solutions. The presence of PEO segments can improve the hydrophilicity of the copolymer and avoid the excessive aggregation of the micelles. CS-g-(PDEAEMA-b-PEO) copolymer has both the unique properties of PDEAEMA-b-PEO and chitosan, and will have the potential applications in biomedical field.     

Surface-initiated atom transfer radical polymerization (SI-ATRP) of styrene from chitosan particles

Polystyrene grafted chitosan particles (PS-Chitosan) were successfully prepared by the surface-initiated atom transfer radical polymerization (SI-ATRP) of styrene from the macroinitiators, bromo-acetyl chitosans with their surface amino and hydroxyl groups, in toluene system with the catalysts of 1,10-phenanthroline and Cu(I)Br. The conversion of monomer (C%) and the percentage of grafting (PG%) increased with the increasing of the polymerizing time and they reached 5.31% and 19.12% after a polymerizing time of 5 h, respectively. The products were characterized by elemental analysis (EA), Fourier transform infrared (FTIR), differential scanning calorimetry (DSC) and X-ray diffraction (XRD).