Abstract Poly(methyl methacrylate) in the brush form is grown from the surface of magnetite nanoparticles by ambient temperature atom transferradicalpolymerization (ATATRP) using a phosphonic acid based initiator. The surface initiator was prepared by the reaction of ethylene glycol with 2-bromoisobutyrl bromide, followed by the reaction with phosphorus oxychloride and hydrolysis. This initiator is anchored to magnetite nanoparticles via physisorption. The ATATRP of methyl methacrylate was carried out in the presence of CuBr/PMDETA complex, without a sacrificial initiator, and the grafting density is found to be as high as 0.90 molecules/nm 2 . The organic–inorganic hybrid material thus prepared shows exceptional stability in organic solvents unlike unfunctionalized magnetite nanoparticles which tend to flocculate. The polymer brushes of various number average molecular weights were prepared and the molecular weight was determined using size exclusion chromatography, after degrafting the polymer from the magnetite core. Thermo- gravimetric analysis, X-ray photoelectron spectra and diffused reflection FT-IR were used to confirm the grafting reaction. Keywords Magnetite nanoparticles Organic–inorganic hybrid material Phosphonic acid initiator ATRP Stable dispersion
combination of the surface-initiated atom transferradicalpolymerization (SI-ATRP) technique and ultraviolet irra- diated crosslinking techniques. Functionalized silica nanoparticles (BrA-SNs) were used as the macroinitiators for the SI-ATRP and the sacrificial silica nanoparticle templates. The strategy developed is expected to be extended to other polymers to prepare various crosslinked polymeric nanocapsules.
Abstract: The long chain vinyl end-functional polystyrene has been synthesized in bulk polymerization method using atom transferradicalpolymerization (ATRP) with Undecenyl-2-Bromopropionate (UnBP) and CuCl/bypyridine catalytic system. The polymerizations demonstrate an increase in molecular weight and conversion in direct proportion to the polymerization time by consumed monomer which exhibited first-order kinetics. This study concludes the simple kinetics of polystyrene synthesized by ATRP using initiator and ligand-to-copper(I) halide was found to be 1:2:1, which tentatively indicates that the coordination sphere of the active copper(I) center contains two bipyridine ligands. The propagation rate has been investigated for long range of time for ensuring that the rate of radical combination or disproportionation is sufficiently less.
We report on the grafting of poly(methyl methacrylate) (PMMA) onto the surface of high-density functionalized graphene oxides (GO) through controlled radicalpolymerization (CRP). To increase the density of surface grafting, GO was first diazotized (DGO), followed by esterification with 2-bromoisobutyryl bromide, which resulted in an atom transferradicalpolymerization (ATRP) initiator-functionalized DGO-Br. The functionalized DGO-Br was characterized by X-ray photoelectron spectroscopy (XPS), Raman, and XRD patterns. PMMA chains were then grafted onto the DGO-Br surface through a ‘ grafting from ’ technique using ATRP. Gel permeation chromatography (GPC) results revealed that polymerization of methyl methacrylate (MMA) follows CRP. Thermal studies show that the resulting graphene-PMMA nanocomposites have higher thermal stability and glass transition temperatures (T g ) than those of pristine PMMA.
Various monomer classes such as styrenes, (meth)acrylates, (meth)acrylamides, dienes, acrylonitrile, and other functional monomers, have been successfully polymerized using ATRP. Generally, ATRP are carried out at high temperatures in bulk, aqueous or non-aqueous media. ATRP is particularly effective for hydrophilic monomers in aqueous media under mild conditions or at room temperature. 12 Based on the above literature findings, the present investigation has been focused to study the kinetics, synthesis, and characterization of homo and block copolymers by controlled/"living" atom transferradicalpolymerization technique. Accordingly, the present work consists of three parts: # Kinetics, synthesis and characterization of glycidyl methacrylate at ambient temperature by using copper(I)/N-alkyl-2-pyridylmethanimine ligands. The characterization of the polymers was carried out by FT-IR, 1 H & 13 C NMR, GPC, ESI MS, TG/DTA and DSC. # Kinetics, synthesis and characterization of t-butyl methacrylate by atom transferradicalpolymerization. The diblock copolymers of PSt-b-Pt-BMA were synthesized by using PSt macroinitiator. The homopolymer, diblock copolymer, and their hydrolyzed products were characterized by FT-IR, 1 H & 13 C NMR, GPC, TG/DTA, and DSC. # Kinetics, synthesis and characterization of amphiphilic poly(ethylene oxide) block copolymers by atom transferradicalpolymerization. The macroinitiators and their block copolymers were characterized by FT-IR, 1 H & 13 C NMR, MALDI TOF-MS, GPC, TG/DTA, DSC and SEM. PART I Kinetics, Synthesis and Characterization of Glycidyl Methacrylate by Atom TransferRadicalPolymerization A series of Schiff base ligands were prepared by condensation of primary amines with pyridine-2-carboxaldehyde, in quantitative yield with relatively short reaction times. The presence of characteristic absorption band around 1650 cm -1 (CH=N) and disappearance of ester group (1712 cm -1 ) in FT-IR spectroscopy
Abstract Thermosensitive nanocables consisting of Au nanowire cores and poly(N-isopropylacrylamide) sheaths (denoted as Au/PNIPAAm) were synthesized by surface- initiated atom transferradicalpolymerization (SI-ATRP). The formation of PNIPAAm sheath was verified by Fourier transform infrared (FTIR) and hydrogen nuclear magnetic resonance ( 1 H NMR) spectroscopy. Transmission electron microscope (TEM) results confirmed the core/shell struc- ture of nanohybrids. The thickness and density of PNIPAAm sheaths can be adjusted by controlling the amount of cross-linker during the polymerization. Signa- ture temperature response was observed from Au/cross- linked-PNIPAAm nanocables. Such smart nanocables show immense potentials as building blocks for novel thermosensitive nanodevices in future.
Abstract: Surface initiated atom transferradicalpolymerization (SI-ATRP) is one of the most versatile technique to modify the surface properties of material. Recent developed metal free SI- ATRP makes such technique more widely applicable. Herein photo-induced metal-free SI-ATRP of methacrylates, such as methyl methacrylate, N-isopropanyl acrylamide, and N,N- dimethylaminoethyl methacrylate, on the surface of SBA-15 was reported to fabricate organic- inorganic hybrid materials. SBA-15 based polymeric composite with adjustable graft ratio was obtained. The structure evolution during the SI-ATRP modification of SBA-15 was monitored and verified by FT-IR, XPS, TGA, BET, and TEM. The obtained polymeric composite showed enhanced adsorption ability for the model compound toluene in aqueous. This procedure provides a low cost, ready availability, and facile modification way to synthesize the polymeric composites without the contamination of metal.
Cellulose by far is the most abundant natural polymer that exists on this planet and presents scientists with the advantage to utilize it as an inexhaustible source of raw material in the synthetic development of environmentally friendly and biocompatible products. Due to its availability and low cost, cellulose and its derivatives are extensively used in industries consisting of textiles, plastics, wood and paper products, coatings, and pharmaceuticals among others. Its structural framework consists of extensive intra and intermolecular hydrogen bonding that makes it completely insoluble in normal aqueous solvents and solutions. Cellulose fibrils contain highly crystalline regions that co-exist with amorphous regions, which has a capacity of holding relatively large amounts of water, thus making it a very hygroscopic molecule. These crystalline regions can be conveniently separated from the low order regions to form rod-like cellulose microcrystallites. The rod-like particles can be coupled with various synthetic polymer structures forming hybrid copolymer blocks that display properties of amphiphiles. Atom TransferRadicalpolymerization, a controlled radicalpolymerization process, is used an effective tool to bridge this carbohydrate molecule with a synthetic macromolecule to generate a hybrid amphiphilic copolymer block that can aggregate in aqueous environments to form micelles.
This investigation indicates the ability to selectively graft glycidyl methacrylate (GMA) only from the external surface of regenerated cellulose (RC) ultrafiltration (UF) membranes using activator generated electron transfer (AGET) atom transferradicalpolymerization (ATRP). This controlled polymerization resulted in epoxy functionalized polymer brush ends. Further reaction of the terminal epoxy groups provides a flexible platform to introduce desired functionalities either by electrophilic or nucleophilic epoxy ring opening. Selective grafting from the external membrane surface was achieved by using an appropriate pore filling solvent prior to modification. A high viscosity pore filling solvent that is immiscible with the reactive monomer solution used during surface modification was the most effective in supressing grafting from the internal pore surface. The effects of grafting on membrane performance were evaluated by determining water permeability and protein rejection.
used to graft polymer from the substrate. However, the most easy and successful one in producing well defined polymer with controlled polydispersities and predeter- mined molecular weight is the surface-initiated atom transferradicalpolymerization technique (SI-ATRP) . This approach allows the synthesis of uniform polymer layers of high grafting density, with tunable thicknesses via molecular weight control on surface. Recently, sur- face-initiated atom transferradicalpolymerization (SI-ATRP) has been demonstrated as a useful tool for modification of different substrates such as silica, mont- morillonite clay (MMT), gold surface, polymer films, silicon wafers, metal/metal oxide, paper or glass, latexes and carbon nanotubes (CNTs) affording various polymer brushes with desired structures, properties, morphologies and functions with high applicable values [7,8]. Glyco- polymers are polymers with pendant saccharide residues which are characterized by their high hydrophilicity and water solubility so they can be used for specialized ap- plications, such as artificial materials for a number of biological, pharmaceutical and biomedical uses . Re- cently, glycopolymers have attracted much attention as a model system to study the specific molecular recognition functions of carbohydrate and their possible applications in biomedical materials and biosensors after the immobi- lization [10,11]. Consequently, due to their importance as
Cellulose was modified by polystyrene (PS) and polyacrylonitrile (PAN) via free radical and living radicalpolymerization, and then cellulose was used as the matrix in the preparation of polymer/clay nanocomposite, through a solution intercalation method. For this purpose, first, the graft polymerization of styrene (St) onto cellulose fibers was performed by using suspension polymerization and the free- radicalpolymerization technique in the presence of potassium persulfate (PPS). Second, the synthesized cellulose-graft-polystyrene was brominated by N-bromosuccinimide (NBS) to obtain polymers with bromine a group. Third, the brominated cellulose fibers were used as macroinitiators in the atom transferradicalpolymerization (ATRP) of acrylonitrile (AN) in the presence of CuCl / 2, 2’-bipyridine (Bpy) catalyst system in THF solvent at 90˚C to prepare the cellulose-graft-polystyrene-graft-polyacrylonitrile. Forth, for preparing the modified clay, Na-MMT was mixed with hexadecyl trimethyl ammonium chloride salt. Finally, cellulose-graft-polystyrene–graft–polyacrylonitrile/organoclay bionanocomposite was prepared in CCl 4 by a solution intercalation method. Then, the structure of the obtained terpolymer was investigated by FT-IR, DSC, TGA, XRD, and SEM techniques. Moreover, the structure of the bionanocomposite was probed by XRD, SEM, and TEM images.
These data show that the azide end-capping reaction is highly effective as a means of terminating the ATRP process. When the surface is treated with an initiator, a small amount of derivatization of the azide occurs, but there is nevertheless a marked difference between the results for samples C and D. However, while this approach successfully yields brush copolymers, it does not provide spatial control over the location of growth of the second polymer. The feasibility of protecting the amine group, prior to the second polymerization stage, was thus explored. The goal was to enable spatially selective introduction of initiator after the conversion of the azide end-cap to an amine.
The polymerization-based DNA detection on strip test involves three steps: 1) immobilization of capture probe; 2) hybridization of target sequence and detection probes; 3) Amplification-by-polymerization and visualization. The thermofix method and streptavidin- biotin interaction were tested for immobilization of DNA capture probe on membrane. The thermofix method was adapted in this research due to higher immobilization efficiency (verified by the afterwards polymerization). For the signal amplification, pSPM grafted from PLL macroinitiators was adapted as the amplification method because it allows direct visualization of DNA detection on nylon membrane after short staining. Continuous work on assembling optimized conditions for complete DNA hybridization tests is yet to be carried out. The optimization of DNA hybridization condition on nitrocellulose membrane has been investigated extensively. 14 DNA hybridization on nylon membrane especially involving PLL has not been reported so far. For example, the hybridization of DNA/PLL complex with capture probe may be different from the hybridization of DNA alone with capture probe. A few challenges envisioned include: steric hindrance from the use of that may reduce capturing efficiency of target DNA and nonspecific aggregation of PLL-DNA complexes that decreases the mobility of target DNA. Applying target DNA and PLL macroinitiators separately help avoid this problem at the expense of additional application step. Alternatively, selecting appropriate solvent system or adding surfactant could be studied to optimize the hybridization of DNA/PLL complex with capture probe.
As for metal catalysts, a complex of a copper (I) halide and 2,2’-bipyridyl is the most widely used catalyst. 104, 105 The catalyst undergoes a one-electron oxidation with concomitant abstraction of a halogen atom from a substrate. Ni, 106 Pd, 107 Ru, 108 Fe, 109 and other metals 110 have been used as well. So far, the copper-based ATRP system has been adapted successfully for the controlled/living polymerization of styrenes, acrylates, methacrylates, acrylonitrile, and other monomers. The current generation of catalyst systems is not sufficiently efficient to polymerize less reactive monomers, such as ethylene, a-olefins, vinyl chloride, and vinyl acetate, which produce non-stabilized, highly reactive radicals. Acrylic and methacrylic acid cannot be polymerized with currently available ATRP catalysts, because these monomers react rapidly with the metal complexes to form metal carboxylates which are inefficient deactivators and cannot be reduced to active ATRP catalysts.
Atom transferradicalpolymerization is acknowledged to be among the methods of controlled radical polymeriza- tion; it is a simple technique of well-defined polymers synthesis with predetermined molecular weights and a narrow molecular weight distribution (MWD) [1-5]. In comparison with other methods of controlled radical po- lymerization, ATRP has several advantages such as a broad spectrum of polymerizable monomers and avail- able of initiators as well as the possibilities of the process performance over a wider temperature span and in the different solvents [5,6].
Triphosgene (Aldrich, 99%), 1,1,4,7,7-pentamethyldiethylenetriamine (PMDETA, Aldrich, 99%), ether absolute (A.R. grade), dichloromethane (A.R. grade), iso- propanol (A.R. grade) were all purchased from Meryer Chemical Technology Co., Ltd. N,N-dimethylformamide (DMF, A.R. grade), and the other normal solvents were purchased from Shanghai Chemical Reagent and purified by con- ventional procedures if needed. There were also some materials prepared and processed in our laboratory. CuCl (Shanghai Chemical Reagent, A.R. grade) was purified by stirring in glacial acetic acid overnight, filtered, washed with ethanol, and then dried in a vacuum oven at 60 C overnight. γ -Benzyl-L-glutamate was synthesized from L-glutamic acid (Sinopharm Chemical Reagent Co., Ltd., B.R. grade) and benzyl alcohol (Sinopharm Chemical Reagent Co., Ltd., A.R. grade) ac- cording to literatures. Poly ( γ -benzyl-L-glutamate) was synthesized by ring-opening polymerization (ROP) of γ -benzyl-L-glutamate N-carboxyanhydride from the monomer of γ -Benzyl-L-glutamate. P4VP (Poly-4-vinylpyridine) was synthe- sized from 4-vinylpyridine (Aladdin, 97%) monomer based on atom transferradicalpolymerization (ATRP). P4VP-b-PBLG diblock copolymer was synthe- sized from Poly-4-vinylpyridine and PBLG through Click Chemistry.
Some vinyl polymers/montmorillonite nanocomposites were prepared via in-situ-atom transferradicalpolymerization (ATRP) in presence of clay. Methyl methacrylate, styrene and n-butyl methacrylate were involved in the formation of such polymeric nanocomposites. Their dielectric properties were extensively studied to invest them in the a.c. power applications. Several dielectric parameters such as dielectric constant loss (ε") and a.c. conductivity (σ) were measured at both different frequencies (0.1 Hz to 100 KHz) and temperature ranged from (20˚C to 90˚C). From the dielectric re- sults, it was realized that the dielectric a.c. conductivity was enhanced by increasing the temperature for the four pre- pared polymer nanocomposites.
de (4) has been prepared according to the procedure described elsewhere. Compound 4 was successfully po- lymerized by surface initiated atom transferradicalpolymerization (ATRP) from the initiator grafted silica particles (sil-poly4). It was also telomerized with 3-mercaptopropyltrimethoxysilane (MPS) and the telomer (T4) was grafted on to silica (sil-T4). TGA and elemental analysis measurement revealed that higher amount of polymer can graft by ATRP process than that of “grafting to” strategy. The results of 13 C CP/MAS NMR measurement showed that the N-alkyl chain of the grafted polymers for both sil-poly4 and sil-T4 remained as less ordered gauche conformational form on silica surface and no inversion to trans form was occurred until temperature is increased up to 50˚C. The retention of alkylbenzene samples showed that sil-poly4 prepared by “grafting from” method yielded extremely higher retention than conventional C 18 phase however, sil-T4
The controlled/living radicalpolymerization (CLRP) has been an indispensable technique to design and create highly functional and efficient materials supporting today’s cutting-edge technologies in many fields, such as drug and gene deliveries - and anti-bacterial treatment  in medical care, photolithography in electronics -, water purification in environmental engineering , and surface modifications of wettability in the tex- tile and vehicle industries -. The significance of the CLRP is the improvement of the functions by un- ifying the physical properties based on strict control of the molecular weight related to the structure of the po- lymers. Many CLRP systems have been established using various catalysts to provide well-controlled molecular weight polymers; e.g., the atom transferradicalpolymerization (ATRP)  , reversible addition-fragmen- tation chain transfer (RAFT) , organoheteroatom-mediated polymerization , nitroxide-mediated polyme- rization (NMP) , iniferter polymerization , and iodide transferpolymerization  . These thermal CLRPs produced a number of architectures with precisely controlled structures including supra molecules with high dimensional structures.