ARGET Atom Transfer Radical Polymerization Research Articles

Ferrocene-Modified Polyacrylonitrile-Containing Block Copolymers as Preceramic Materials.

In the pursuit of fabricating functional ceramic nanostructures, the design of preceramic functional polymers has garnered significant interest. With their easily adaptable chemical composition, molecular structure, and processing versatility, these polymers hold immense potential in this field. Our study succeeded in focusing on synthesizing ferrocene-containing block copolymers (BCPs) based on polyacrylonitrile (PAN). The synthesis is accomplished via different poly(acrylonitrile-block-methacrylate)s via atom transfer radical polymerization (ATRP) and activators regenerated by electron transfer ATRP (ARGET ATRP) for the PAN macroinitiators. The molecular weights of the BCPs range from 44 to 82 kDa with dispersities between 1.19 and 1.5 as determined by SEC measurements. The volume fraction of the PMMA block ranges from 0.16 to 0.75 as determined by NMR. The post-modification of the BCPs using 3-ferrocenyl propylamine has led to the creation of redox-responsive preceramic polymers. The thermal stabilization of the polymer film has resulted in stabilized morphologies based on the oxidative PAN chemistry. The final pyrolysis of the sacrificial block segment and conversion of the metallopolymer has led to the formation of a porous carbon network with an iron oxide functionalized surface, investigated by scanning electron microscopy (SEM), energy dispersive X-ray mapping (EDX), and powder X-ray diffraction (PXRD). These findings could have significant implications in various applications, demonstrating the practical value of our research in convenient ceramic material design.

A specific sensor system based on in-situ synthesis fluorescent polymers by ARGET ATRP achieving sensitive exosome detection

Exosomes, as a kind of tumor biomarker, are often found at elevated levels above normal in the blood of cancer patients, making highly sensitive exosome testing important for monitoring the development and progression of cancer. In this work, an ultra-sensitive and specific fluorescence method for exosome assays was constructed on the basis of atom transfer radical polymerization (ATRP) technique. Firstly, two recognition units, the CD63 aptamer and the EGFR antibody, can specifically bind to exosomes to form a sandwich structure, which endows the proposed sensor with excellent selectivity through two specific recognitions. Secondly, activator regenerated by electron transfer ATRP (ARGET ATRP) polymerization amplification method can introduce a huge amount of the fluorescent monomers into the sensing system, leading to a marked rise in sensitivity. Under optimal experimental conditions, a clear linear relationship between the logarithm of the fluorescence intensity and the concentration of exosomes in the range of 5 × 104 exosomes/mL to 5 × 109 exosomes/mL was obtained. The limit of detection (LOD) was as low as 11,610 exosomes/mL. Furthermore, this sensor exhibited good selectivity and stability, and excellent immunity to interference, providing a new method for the detection of exosomes. The exosome detection strategy used in this system provides a new idea for effective detection of lung cancer at an early stage.

Quaternization of Poly(2-diethyl aminoethyl methacrylate) Brush-Grafted Magnetic Mesoporous Nanoparticles Using 2-Iodoethanol for Removing Anionic Dyes

Magnetic mesoporous silica nanoparticles (Fe3O4-MSNs) were successfully synthesized with a relatively high surface area of 568 m2g−1. Fe3O4-MSNs were then modified with poly(2-diethyl aminoethyl methacrylate) (PDEAEMA) brushes using surface-initiated ARGET atom transfer radical polymerization (ATRP) (Fe3O4@MSN-PDMAEMA). Since the charge of PDEAEMA is externally regulated by solution pH, tertiary amines in the polymer chains were quaternized using 2-iodoethanol to obtain cationic polymer chains with a permanent positive charge (Fe3O4@MSN-QPDMAEMA). The intensity of the C−O peak in the C1s X-ray photoelectron spectrum increased after reaction with 2-iodoethanol, suggesting that the quaternization process was successful. The applicability of the synthesized materials on the removal of methyl orange (MO), and sunset yellow (E110) dyes from an aqueous solution was examined. The effects of pH, contact time, and initial dyes concentrations on the removal performance were investigated by batch experiments. The results showed that the Fe3O4@MSN-PDMAEMA sample exhibited a weak adsorption performance toward both MO and E110, compared with Fe3O4@MSN-QPDMAEMA at a pH level above 5. The maximum adsorption capacities of MO and E110 using Fe3O4@MSN-QPDMAEMA were 294 mg g−1 and 194.8 mg g−1, respectively.

Folic Acid-Terminated Poly(2-Diethyl Amino Ethyl Methacrylate) Brush-Gated Magnetic Mesoporous Nanoparticles as a Smart Drug Delivery System.

Currently, chemotherapy is an important method for the treatment of various cancers. Nevertheless, it has many limitations, such as poor tumour selectivity and multi-drug resistance. It is necessary to improve this treatment method by incorporating a targeted drug delivery system aimed to reduce side effects and drug resistance. The present work aims to develop pH-sensitive nanocarriers containing magnetic mesoporous silica nanoparticles (MMSNs) coated with pH-responsive polymers for tumour-targeted drug delivery via the folate receptor. 2-Diethyl amino ethyl methacrylate (DEAEMA) was successfully grafted on MMSNs via surface initiated ARGET atom transfer radical polymerization (ATRP), with an average particle size of 180 nm. The end groups of poly (2-(diethylamino)ethyl methacrylate) (PDEAEMA) brushes were converted to amines, followed by a covalent bond with folic acid (FA) as a targeting agent. FA conjugated to the nanoparticle surface was confirmed by X-ray photoelectron spectroscopy (XPS). pH-Responsive behavior of PDEAEMA brushes was investigated by Dynamic Light Scattering (DLS). The nanoparticles average diameters ranged from ca. 350 nm in basic media to ca. 650 in acidic solution. Multifunctional pH-sensitive magnetic mesoporous nanoparticles were loaded with an anti-cancer drug (Doxorubicin) to investigate their capacity and long-circulation time. In a cumulative release pattern, doxorubicin (DOX) release from nano-systems was ca. 20% when the particle exposed to acidic media, compared to ca. 5% in basic media. The nano-systems have excellent biocompatibility and are minimally toxic when exposed to MCF-7, and -MCF-7 ADR cells.

Catalytic Halogen Exchange in Miniemulsion ARGET ATRP: A Pathway to Well-Controlled Block Copolymers.

Halogen exchange in atom transfer radical polymerization (ATRP) is an efficient way to chain-extend from a less active macroinitiator (MI) to a more active monomer. This has been previously achieved by using CuCl/L in the equimolar amount to Pn -Br MI in the chain extension step. However, this approach cannot be effectively applied in systems based on regeneration of activators (ARGET ATRP), since they operate with ppm amounts of catalysts. Herein, a catalytic halogen exchange procedure is reported using a catalytic amount of Cu in miniemulsion ARGET ATRP to chain-extend from a less active poly(n-butyl acrylate) (PBA) MI to a more active methyl methacrylate (MMA) monomer. Influence of different reagents on the initiation efficiency and dispersity is studied. Addition of 0.1 m NaCl or tetraethylammonium chloride to ATRP of MMA initiated by methyl 2-bromopropionate leads to high initiation efficiency and polymers with low dispersity. The optimized conditions are then employed in chain extension of PBA MI with MMA to prepare diblock and triblock copolymers.

Preparation of hydrophobic tannins‐inspired polymer materials via low‐ppm ATRP methods

The novel hydrophobic coating material was received for the first time by a two‐step synthetic route. Firstly, the 15‐functional brominated macroinitiator was prepared by the esterification methodology. Next step covers synthesis of star‐like polymers by poly(n‐butyl acrylate) (PBA) arms polymerization via three low‐ppm atom transfer radical polymerization (ATRP) approaches including application of copper and silver wire in SARA and ARGET ATRP, respectively, as driving forces in redox cycle of catalyst, and an external stimulus in the form of electric current (seATRP) as the third approach in copper(II) regeneration system. As expected, the electrochemically mediated technique allows synthesis of tannic acid‐inspired coating polymers in precisely controlled manner during the entire polymerization process, proved by linear first‐order kinetics plot in contrast to above‐mentioned methods, low dispersity (Ð = 1.18) of star‐shaped polymers, and high efficiency of initiation (ƒ i = 81%) determined after detaching of polymers side arms. Macromolecules received by all low‐ppm ATRP solutions were characterized by preserved chain‐end functionality (theoretical dead chain fraction; DCFtheo <1%). Adhesive and hydrophobic properties of received polymer materials were investigated by contact angles (θ) and free surface energy (FSE) calculations. Prepared polymer films besides excellent hydrophobic properties have great potential as a self‐healing solution.

A Novel Strategy for the Synthesis of Amphiphilic and Thermoresponsive Poly(N-isopropylacrylamide)-b-Polystyrene Block Copolymers via ATRP.

A new synthetic approach is presented for the preparation of Poly(N-isopropylacrylamide-block-styrene) PNIPAM-b-PS via an Atom Transfer Radical Polymerization (ATRP) technique. The proposed method is based on application of 2-chloro-N-(2-hydroxyethyl)propanamide (NCPAE) as a bifunctional initiator, which enables ATRP of two monomers, differing in activity and polarity, into two stages. The synthesized copolymer molecules contain two well-defined polymer chains connected by a linker, which is a derivative of the proposed initiator. Using NCPAE led to PNIPAMs with well-planned molecular weight, low polydispersities (PDI=1.1÷1.3) and hydroxyl functionality. Activation of such blocks for initiation of styrene polymerization was performed using α-bromoisobutyryl bromide. After such a modification, the synthesized homopolymers acted as macroinitiators in ARGET ATRP and a well-defined polystyrene block, as the next one in the polymer chain was successfully formed. Both of the synthesized macromolecules, PNIPAM and PNIPAM-b-PS, exhibit a thermoresponsive behavior with explicit lower critical solution temperatures (LCST) in their aqueous solutions. The synthesized homopolymers and subsequently derived block copolymers were characterized using Size-Exclusion Chromatography, Differential Scanning Calorimetry, Dynamic Light Scattering, and NMR spectroscopy.

Polymer Architecture: Does It Influence Shear Stability?

Hyperbranched and linear poly(alkyl methacrylate)s with and without polycaprolactone segments were designed and prepared via a core-first strategy, and then evaluated with respect to their rheology and shear stability performance. The focus of this work was to study the effect of architecture on mechanical shear stability, as it relates to lubricant performance. The polymers were prepared from functionalized macroinitiators subsequently subjected to atom transfer radical polymerization (ATRP)/activators regenerated by electron transfer atom transfer radical polymerization (ARGET ATRP) conditions with dodecyl methacrylate and 2-ethylhexyl methacrylate mixtures. As expected, most compounds displayed an increased viscosity index along with increasing molecular weight. The inclusion of polycaprolactone appears to have enhanced the viscosity index in select samples. Although the hyperbranched polymers studied here varied in the number of arms from about 20 to 1 (linear), the data presented supports the empirical understanding that shear stability is mainly influenced by molecular weight and not architecture or topology. The polymers with caprolactone blocks and shorter methacrylate pendants demonstrated a positive effect on the shear stability, as in possessing the lowest permanent shear stability index, 4 times lower than other compounds included in this study as well as the benchmark.

ATRP-based synthesis and characterization of light-responsive coatings for transdermal delivery systems

The grafting of poly(hydroxyethylmethacrylate) on polymeric porous membranes via atom transfer radical polymerization (ATRP) and subsequent modification with a photo-responsive spiropyran derivative is described. This method leads to photo-responsive membranes with desirable properties such as light-controlled permeability changes, exceptional photo-stability and repeatability of the photo-responsive switching. Conventional track etched polyester membranes were first treated with plasma polymer coating introducing anchoring groups, which allowed the attachment of ATRP-initiator molecules on the membrane surface. Surface initiated ARGET–ATRP of hydroxyethylmethacrylate (where ARGET stands for activator regenerated by electron transfer) leads to a membrane covered with a polymer layer, whereas the controlled polymerization procedure allows good control over the thickness of the polymer layer in respect to the polymerization conditions. Therefore, the final permeability of the membranes could be tailored by choice of pore diameter of the initial membranes, applied monomer concentration or polymerization time. Moreover a remarkable switch in permeability (more than 1000%) upon irradiation with UV-light could be achieved. These properties enable possible applications in the field of transdermal drug delivery, filtration, or sensing.

Facile synthesis of ZnO-poly(2-hydroxyethyl methacrylate) nanocomposites by surface-initiated ARGET atom transfer radical polymerization.

The covalent attachment of poly(2-hydroxyethyl methacrylate) on ZnO nanoparticles (NPs) has been achieved by ARGET ATRP. The polymer chains were grown from the surface of ATRP-initiator modified ZnO NPs with a copper (II) catalyst under activation of zerovalent copper as a reducing agent. FT-IR, FE-SEM, TEM and TGA were employed for the characterization of the nanocomposites. GPC was used to determine the molecular weight and PDI of the cleaved polymer. The covalent attachment of polymer chains onto the surface of ZnO NPs was sufficiently confirmed by FT-IR. In addition, the formation of the polymer encapsulating ZnO cores was demonstrated from TEM and SEM images. It was found that the growing of polymer brushes from the ZnO surface could be induced even though the catalyst amount was reduced to 10 ppm without loss of inherent control manner. This report contributed to demonstrate the versatility and feasibility of ATRP-based surface-initiated polymerization for the preparation of inorganic/polymer nanocomposites.

Synthesis of Polyacrylonitrile by ARGET Atom Transfer Radical Polymerization in the Presence of Zinc Powder and Its Adsorption Properties after Modification

Zinc powder was used as both reducing agent and supplemental activator for atom transfer radical polymerization via activators regenerated by electron transfer (ARGET ATRP) to prepare polyacrylonitrile (PAN). Zinc powder was found to be an excellent additional agent with better controlled behavior, higher monomer conversion, and faster polymerization rate in comparison with ascorbic acid (VC). The effects of catalyst, ligand, and initiator on polymerization rate and molecular weight of PAN were investigated in detail. The resulting PAN was modified and employed as an adsorbent for removal of metal ions. Compared with Cu(II) and Pb(II), the modified PAN showed an excellent adsorption performance toward Hg(II).

Robust grafting of PEG-methacrylate brushes from polymeric coatings

A study is presented of the grafting of poly(ethylene glycol)methyl ether methacrylate (PEGMA) from polymeric macroinitiator films to form well-defined polymer brushes, using activators generated/regenerated by electron transfer (AGET/ARGET) atom transfer radical polymerization (ATRP). Polymer brush coatings can potentially be obtained on surfaces of virtually any shape and composition, because of the ease of conformal casting of the anchoring macroinitiator film. Polymer brush coatings are synthesized in a robust way, as ARGET and AGET ATRP require little to no deoxygenation and make use of stable catalysts. The monomer, catalyst, ligand and reducing agent concentrations, the amount and type of initiating moiety in the anchoring films, and the choice of solvents are optimized, resulting in control over the rate of reaction, and the molecular weight of poly(PEGMA). The best conditions are determined for the formation of a poly(PEGMA) brush with high grafting density, controlled thickness and “living” ends available for post-functionalization.

Preparation of a novel polymer monolith using atom transfer radical polymerization method for solid phase extraction

In this study, a novel polymer monolith based solid phase extraction (SPE) material has been prepared by two-step atom transfer radical polymerization (ATRP) method. Firstly, employing ethylene glycol dimethacrylate (EDMA) as a cross-linker, a polymer monolith filled in a filter head has been in-situ prepared quickly under mild conditions. Then, the activators generated by electron transfer ATRP (ARGET ATRP) was used for the modification of poly(2-(dimethylamino)ethyl-methacrylate) (PDMAEMA) on the monolithic surface. Finally, this synthesized monolith for SPE was successfully applied in the extraction and enrichment of steroids. The results revealed that ATRP can be developed as a facile and effective method with mild reaction conditions for monolith construction and has the potential for preparing monolith in diverse devices.

Recent Developments in Atom Transfer Radical Polymerization (ATRP): Methods to Reduce Metal Catalyst Concentrations

Atom transfer radical polymerization (ATRP) was initially developed in the mid-1990s, and with continued refinement and use has led to significant discoveries in new materials. However, metal contamination of the polymer product is an issue that has proven detrimental to widespread industrial application of ATRP. The laboratories of K. Matyjaszewski have made significant progress towards removing this impediment, leading the development of "activators regenerated by electron transfer" ATRP (ARGET ATRP) and electrochemically mediated ATRP (eATRP) technologies. These variants of ATRP allow polymers to be produced with great molecular weight and functionality control but at significantly reduced catalyst concentrations, typically at parts per million levels. This Concept examines these polymerizations in terms of their mechanism and outcomes, and is aimed at giving the reader an overview of recent developments in the field of ATRP.

Synthesis of polyacrylonitrile via ARGET ATRP using CCl4 as initiator

AbstractActivators regenerated by electron transfer (ARGET) for atom transfer radical polymerization (ATRP) of acrylonitrile (AN) was investigated using carbon tetrachloride (CCl4) as initiator, ferric trichloride anhydracs (FeCl3)/iminodiacetic acid (IDA) as catalyst system, L‐ascorbic acid (VC) as reducing agent, and N,N‐dimethylformamide (DMF) as solvent. Kinetic data of polymerization demonstrated the features of living/controlled free‐radical polymerization. The conversion of AN increased with the increasing concentration of CCl4, [FeCl3]/[IDA] catalyst system and VC. The molecular weight decreased with the increasing concentration of CCl4, [FeCl3]/[IDA] catalyst system and VC. The value of polydispersity index (PDI) increased with the increasing concentration of [FeCl3]/[IDA] catalyst system and VC, while the value of PDI decreased first and then increased with the increasing concentration of CCl4 and IDA. 1H‐NMR spectra of PAN further verified the features of living/controlled free radical polymerization of AN. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010

Grafting from Surfaces for “Everyone”: ARGET ATRP in the Presence of Air

Atom-transfer radical polymerization (ATRP) is one of the controlled/living radical polymerizations yielding well-defined (co)polymers, nanocomposites, molecular hybrids, and bioconjugates. ATRP, as in any radical process, has to be carried out in rigorously deoxygenated systems to prevent trapping of propagating radicals by oxygen. Herein, we report that ATRP can be performed in the presence of limited amount of air and with a very small (typically ppm) amount of copper catalyst together with an appropriate reducing agent. This technique has been successfully applied to the preparation of densely grafted polymer brushes, poly(n-butyl acrylate) homopolymer, and poly(n-butyl acrylate)-block-polystyrene copolymer from silicon wafers (0.4 chains/nm2). This simple new method of grafting well-defined polymers does not require any special equipment and can be carried out in vials or jars without deoxygenation. The grafting for "everyone" technique is especially useful for wafers and other large objects and may be also applied for molecular hybrids and bioconjugates.