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).     

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.     

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.     

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.     

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。     

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 core-shell nanoparticles using organic surface-functionalized gold and Au@SiO2 nanoparticles as multifunctional initiators in atom transfer radical polymerization

Gold and Au@SiO2 nanoparticles were synthesized and surface-functionalized by initiators for atom transfer radical polymerization (ATRP), either using a thiol or a trialkoxysilane anchor group for the immobilization of the initiating functionality. The thus obtained initiator-capped gold systems were applied in polymerizations of various monomers, such as styrene, methacrylic acid trimethyloxysilyl propylester and isoprene and copolymers thereof. The final inorganic-organic core-shell nanoparticles were characterized applying different techniques such as electron microscopy and light scattering. Kinetic studies of the polymerizations revealed that they were highly controlled and therefore the thickness of the polymer shell could be easily adjusted. The obtained nanoparticles formed stable suspensions in various organic solvents and can therefore be used as building blocks for polymer nanocomposites.     

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.     

Preparation of silica hollow fibers by surface-initiated atom transfer radical polymerization from electrospun fiber templates

Silica hollow fibers were produced by surface-initiated atom transfer radical polymerization (ATRP) from poly(methyl methacrylate-co-vinylbenzyl chloride) (P(MMA-co-VBC)) electrospun fibers combined with sol-gel process and subsequent calcination. Fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), transmission electron microscopy (TEM), thermal gravimetric analysis (TGA), X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD) were used to characterize the intermediate products and the silica hollow fibers. The resulting silica hollow fibers are of high purity with amorphous morphology. The thickness of the hollow fibers is approximately 0.25 µm.     

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。     

"Hairy" single-walled carbon nanotubes prepared by atom transfer radical polymerization

"Hairy nano-objects" are hybrid nanostructures comprising a core surrounded by a "hairlike" corona of flexible polymer chains, the role of which is typically to improve the solubility of the core material or to improve its dispersability and adhesion in other polymer matrices. Both aspects could be particularly useful with carbon nanotubes, especially in their applications as reinforcing agents. The controlled synthesis of hairy carbon nanotubes is accomplished by chemical modification with 2-bromopropionate followed by extension with poly(n-butyl acrylate) through atom transfer radical polymerization. The obtained hairy nanotubes are visualized at nearly molecular resolution with tapping-mode atomic force microscopy, providing insight into the uniformity of grafted chain lengths and grafting density. The grafting densities vary from approximately 1.0-10.0 chains nm(-1) along the nanotubes. Such a wide range of grafting density may indicate some chemical heterogeneity along and between the nanotubes; it may be also an indication of the challenges associated with carrying out chemical modification of nano-objects having high tendency to aggregate.     

Surface modification of glycidyl-containing poly(methyl methacrylate) microchips using surface-initiated atom-transfer radical polymerization

Fabrication of microfluidic systems from polymeric materials is attractive because of simplicity and low cost. Unfortunately, the surfaces of many polymeric materials can adsorb biological samples. Therefore, it is necessary to modify their surfaces before these polymeric materials can be used for separation and analysis. Oftentimes it is difficult to modify polymeric surfaces because of their resistance to chemical reaction. Recently, we introduced a surface-reactive acrylic polymer, poly(glycidyl methacrylate-co-methyl methacrylate) (PGMAMMA), which can be modified easily and is suitable for fabrication of microfluidic devices. Epoxy groups on the surface can be activated by air plasma treatment, hydrolysis, or aminolysis. In this work, the resulting hydroxyl or amino groups were reacted with 2-bromoisobutylryl bromide to introduce an initiator for surface-initiated atom-transfer radical polymerization (SI-ATRP). Polyethylene glycol (PEG) layers grown on the surface using this method were uniform, hydrophilic, stable, and resistant to protein adsorption. Contact angle measurement and X-ray photoelectron spectroscopy (XPS) were used to characterize activated polymer surfaces, initiator-bound surfaces, and PEG-grafted surfaces. We obtained excellent capillary electrophoresis (CE) separations of proteins and peptides with the PEG-modified microchips. A separation efficiency of 4.4 x 10(4) plates for a 3.5 cm long separation channel was obtained.     

Anticoagulant surface of 316 L stainless steel modified by surface-initiated atom transfer radical polymerization

Polished 316 L stainless steel (SS) was first treated with air plasma to enhance surface hydrophilicity and was subsequently allowed to react with 2-(4-chlorosulfonylphenyl)ethyltrimethoxysilane to introduce an atom transfer radical polymerization (ATRP) initiator. Accordingly, the surface-initiated atom transfer radical polymerization of polyethylene glycol methacrylate (PEGMA) was carried out on the surface of the modified SS. The grafting progress was monitored by water contact angle measurements, X-ray photoelectron spectroscopy and atomic force microscopy. The polymer thickness as a function different polymerization times was characterized using a step profiler. The anticoagulative properties of the PEGMA modified SS surface were investigated. The results showed enhanced anticoagulative to acid-citrate-dextrose (ACD) blood after grafting PEGMA on the SS surface.     

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.     

Controlled fabrication of theophylline imprinted polymers on multiwalled carbon nanotubes via atom transfer radical polymerization

Theophylline imprinted polymers were synthesized on the surface of multiwalled carbon nanotubes via atom transfer radical polymerization using brominated multiwalled carbon nanotubes as an initiator. The nanotube-based initiator was prepared by directly reacting acyl chloride-modified multiwalled carbon nanotubes with 2-hydroxylethyl-2'-bromoisobutyrate. The grafting copolymerization of 2-hydroxyethyl-2-methyl-2-propenoate and ethylene glycol dimethacrylate in the presence of template theophylline led to thin molecularly imprinted polymer films coating multiwalled carbon nanotubes. The thickness of molecularly imprinted polymer films prepared in this study was about 5 nm as determined by transmission electron microscopy. Fourier-transform infrared spectroscopy was utilized to follow the introduction of initiator groups as well as polymers on the carbon nanotube surfaces. Thermogravimetric analysis indicated that the molecularly imprinted polymers were successfully grown from the carbon nanotube surfaces, with the final products having a polymer weight percentage of ca. 50 wt%. The adsorption properties, such as adsorption dynamics, special binding and selective recognition capacity, of the as-prepared molecularly imprinted polymer films were evaluated. The results demonstrated that the composite of molecularly imprinted polymers and multiwalled carbon nanotubes not only possessed a rapid dynamics but also exhibited a good selectivity toward theophylline, compared to caffeine.     

原子转移自由基聚合与高分子膜亲水化/功能化构造

原子转移自由基聚合(ATRP)对膜的亲水化/功能化改性包括对膜基体材料的共聚改性和对膜的表面改性.膜基体材料的改性最多见于PVDF为主链的两亲性聚合物.ATRP对膜的表面改性尤其是膜的表面引发方法,可实现将不同功能性单体接枝到聚合物膜表面,得到了抗污染能力强,生物相容性好,开关响应迅速等多种功能性表面层.直接的表面引发改性是一种高效,灵活的表面修饰/功能化方法,也是目前应用最广泛的改性技术.