Reverse Atom Transfer Radical Polymerization Research Articles

Modern trends in controlled synthesis of functional polymers: fundamental aspects and practical applications

Major trends in controlled radical polymerization (CRP) or reversible-deactivation radical polymerization (RDRP), the most efficient method of synthesis of well-defined homo- and copolymers with specified parameters and properties, are critically analyzed. Recent advances associated with the three classical versions of CRP: nitroxide mediated polymerization, reversible addition-fragmentation chain transfer polymerization and atom transfer radical polymerization, are considered. Particular attention is paid to the prospects for the application of photoinitiation and photocatalysis in CRP. This approach, which has been intensively explored recently, brings synthetic methods of polymer chemistry closer to the light-induced processes of macromolecular synthesis occurring in living organisms. Examples are given of practical application of CRP techniques to obtain industrially valuable, high-tech polymeric products.The bibliography includes 429 references.

Development of Environmentally Friendly Atom Transfer Radical Polymerization.

Atom transfer radical polymerization (ATRP) is one of the most successful techniques for the preparation of well-defined polymers with controllable molecular weights, narrow molecular weight distributions, specific macromolecular architectures, and precisely designed functionalities. ATRP usually involves transition-metal complex as catalyst. As the most commonly used copper complex catalyst is usually biologically toxic and environmentally unsafe, considerable interest has been focused on iron complex, enzyme, and metal-free catalysts owing to their low toxicity, inexpensive cost, commercial availability and environmental friendliness. This review aims to provide a comprehensive understanding of iron catalyst used in normal, reverse, AGET, ICAR, GAMA, and SARA ATRP, enzyme as well as metal-free catalyst mediated ATRP in the point of view of catalytic activity, initiation efficiency, and polymerization controllability. The principle of ATRP and the development of iron ligand are briefly discussed. The recent development of enzyme-mediated ATRP, the latest research progress on metal-free ATRP, and the application of metal-free ATRP in interdisciplinary areas are highlighted in sections. The prospects and challenges of these three ATRP techniques are also described in the review.

Comparison of Long-Term Stability of Initiating Monolayers in Surface-Initiated Controlled Radical Polymerizations.

The reproducibility of polymer brush synthesis via surface-initiated controlled radical polymerization is interrogated. Experiments compare the stability of initiating monolayers for surface-initiated (SI) reversible addition-fragmentation chain transfer polymerization (SI-RAFT) and SI atom transfer radical polymerization (SI-ATRP). Initiator-functionalized substrates are stored under various conditions and grafting densities of the resulting polymer brush films are determined via in situ ellipsometry. Decomposition of one of the examined SI-RAFT initiators results in limited reproducibility for polymer brush surface modification. In contrast, initiators for SI-ATRP show excellent stability and reproducibility. While both techniques bring inherent benefits and limitations, the described findings will help scientists choose the most efficient technique for their goals in chemical and topographical surface modification.

Copolymerization of Styrene and [Poly(ethylene glycol) methyl ether] Methacrylate using Reverse Atom Transfer Radical Polymerization

Copolymerization of Styrene and [Poly(ethylene glycol) methyl ether] Methacrylate using Reverse Atom Transfer Radical Polymerization

Synthesis of norbornene/divinylbenzene copolymers catalyzed by anilinonaphthoquinone‐ligated nickel complexes and their applications for the synthesis of graft polymers

AbstractThe copolymerization of norbornene (NB) and divinylbenzene (DVB) was carried out using anilinonaphthoquinone‐ligated nickel complexes of the type [Ni(C10H5O2NAr)(Ph)(PPh3)] (1a: Ar = C6H3‐2,6‐ iPr; 1b: Ar = C6H2‐2,4,6‐Me; 1c: Ar = C6H5) with modified methylaluminoxane (MMAO) as a cocatalyst. The DVB content was varied (5–25 mol%) and the resulting copolymers exhibited number‐average molecular weights (Mn) of 40,000–69,000 g/mol with polydispersities (PDI = 1.5–1.8). The styryl group of the NB/DVB copolymer was used for grafting poly(methyl methacrylate) by reverse atom transfer radical polymerization using azobisisobutyronitrile in the presence of copper chloride and bipyridine.

High-flux, high-selectivity loose nanofiltration membrane mixed with zwitterionic functionalized silica for dye/salt separation

A kind of charged nano-material SiO2-SBMA was prepared by reverse atom transfer radical polymerization (RATRP) with nano SiO2 and 2-methacryloyloxy ethyl dimethyl (3-sulfopropyl)-ammonium hydroxide sulfobetaine methacrylate (SBMA). This material was dispersed with polyvinylpyrrolidone (PVP) and polyethersulfone (PES) in N, N-dimethylacetamide (DMAc) to obtain a casting solution, with which the loose nanofiltration (NF) membrane SiO2-PSBMA/PES was constructed using phase inversion on a sheet of glass with the automatic film applicator. The membrane structure and separation performance were investigated. The results indicated that the surface roughness, hydrophilicity, pure water flux and permeability selectivity of the loose NF membrane all improved. When the addition amount of SiO2-PSBMA was 0.5%, the order for retention of inorganic salts was R (Na2SO4) > R (NaCl) > R (MgCl2), which exhibited typical characteristics of the negatively charged membrane. At 0.4 MPa, the rejection of the membrane for Na2SO4 was 11.4%. The rejection of reactive black 5 (RB5) and reactive green 19 (RG19) were 97.9% and 99.0%, and the corresponding permeation flux were 32.3 L m−2 h−1 bar−1 and 28.1 L m−2 h−1 bar−1, respectively. The prepared membrane had higher flux and selectivity in dye wastewater treatment and was expected to be used in the treatment of salt-containing dye wastewater.

Non-isothermal decomposition kinetics of in-chain functionalized poly(MMA-co-ethylene)

Efficient incorporation of polar monomers in polyolefin can lead to many desirable properties in the parent chain. Herein, we report the synthesis of ethylene and methyl methacrylate (MMA)-based copolymers by transition metal-catalysed reverse atom transfer radical polymerization technique with controlled ethylene feed pressure. Successful copolymerization was confirmed by 1H nuclear magnetic resonance analysis. With increasing polymerization time, resultant copolymers exhibit bimodal molecular weight distributions with controlled high molecular weight component and less-controlled low molecular weight component as confirmed by size-exclusion chromatography analysis. Morphological and crystal structures of the copolymer were established using scanning electron microscope and X-ray diffraction analysis, respectively. Thermogravimetric analysis of the copolymer under non-isothermal condition shows a two-step decomposition process with the major decomposition in the range of 320–450 °C. Based on approaches of Friedman and Flynn–Wall–Ozawa, model-free multivariate nonlinear regression analyses were performed to find out the formal mechanisms, kinetic model and its corresponding kinetic triplets. The results revealed the nth-order (Fn) mechanism responsible for the decomposition of the copolymer. The estimated kinetic parameters for the decomposition of poly(MMA-co-ethylene) copolymer were Ea= 227.80 kJ mol−1 and A = 6.76 × 1015 s−1.

Silica aerogel-filled PMMA by in situ reverse atom transfer radical polymerization: kinetics and thermal studies

Hydrophobically modified silica aerogel nanoparticles (H-SiANp) were used for in situ polymerization of methyl methacrylate by reverse atom transfer radical polymerization to synthesize well-defined PMMA nanocomposites. Inherent characteristics of the prepared H-SiANp were evaluated by nitrogen adsorption/desorption isotherms, SEM, and TEM. Conversion and molecular weight determinations were carried out using GC and SEC, respectively. Addition of 3 mass% of the H-SiANp leads to decrement of conversion from 92 to 74%. Molecular weight of poly (methyl methacrylate) chains also decreases from 19,737 to 15,662 g mol−1 by addition of only 3 mass% H-SiANp; however, PDI values increase from 1.36 to 1.82. Linear increase of ln(M0/M) with time for all the samples shows that polymerization proceeds in a living manner. In addition, suitable agreement between theoretical and experimental molecular weight in combination with low PDI values can appropriately demonstrate the living nature of the polymerization. TG results indicate that by increasing H-SiANp content, improvements in thermal stability of the nanocomposites were obtained. DSC results show a decrease in glass transition temperature from 87.4 to 80.9 °C by addition of 3 mass% H-SiANp.

Synthesis of PAN with adjustable molecular weight and low polydispersity index (PDI) value via reverse atom transfer radical polymerization

ABSTRACTThe reverse atom transfer radical polymerization (RATRP) of acrylonitrile (AN) was carried out in N, N-dimethylformamide (DMF) with AIBN as initiator, FeCl3•6H2O/triphenylphosphine (PPh3) and FeCl3•6H2O/pentamethyldle-thylenetrlamlne (PMDETA) as catalytic systems, respectively. Effect of reaction time and initiator concentration on polymerization rate, molecular weight and molecular weight distribution were investigated in detail. The Fourier transform infrared spectrometer (FTIR) and 1H nuclear magnetic resonance spectroscopy (1HNMR) were employed to analyze the chain end of the PAN. Gel permeation chromatography (GPC) was applied to measure the molecular weight and polydispersity index (PDI) of PAN. The polymerization demonstrated a typical pseudo first-order kinetics characteristics as evidenced by the number-average molecular weights (Mn) increasing linearly with monomer conversion; the Mn decreasing with the increasing of the initiator concentration. Meanwhile, the low PDI value (<1.2) indicated the controllability of polymerization.

Antifouling Surfaces Based on Fluorine-Containing Asymmetric Polymer Brushes: Effect of Chain Length of Fluorinated Side Chain.

The influence of chain length of a fluorinated side chain of an asymmetric polymer brush with poly(ethylene glycol) (PEG) side chains on the antifouling property was systematically investigated so as to obtain more knowledge for deepening our understanding of the structure-(antifouling)-property relationship of asymmetric polymer brush. A series of asymmetric polymer brushes, consisting of hydrophobic poly(pentafluoropropyl methacrylate) (PPTFMA) side chains with the number of repeat units of pentafluoropropyl methacrylate (PTFMA) ranging from 8 to 42 and hydrophilic PEG side chains, was first synthesized by sequential reversible addition-fragmentation chain transfer (RAFT) polymerization and atom transfer radical polymerization (ATRP). Subsequently, thin films were prepared by spin-casting the solution of these brushes onto indium tin oxide (ITO) and SiO2 substrates. Water contact angle analysis showed that the hydrophobicity of the film surface increased with the length of PPTFMA side chain. The atomic force microscopy (AFM) measurement demonstrated that these films had a roughness of <3 and <10 nm onto ITO glass and SiO2 substrates, respectively. The antifouling behaviors of these films in bovine serum albumin (BSA) solution were evaluated by quartz crystal microbalance (QCM), which showed that the asymmetric brush surfaces had considerable antifouling performance with less protein adsorption in comparison with the bare surface. In addition, the films made from polymer brushes with shorter PPTFMA side chains exhibited better antifouling and fouling-release behaviors.

IronIII Half Salen Catalysts for Atom Transfer Radical and Ring-Opening Polymerizations.

A series of monometallic pentacoordinate FeIII chloride complexes have been prepared and characterized by high-resolution mass spectrometry and elemental analysis. X-ray diffraction analysis showed that the bis-chelated FeIII complexes bear distorted trigonal bipyramidal geometries. The air- and moisture-stable FeIII complexes were screened as mediators in the reverse atom transfer radical polymerization (ATRP) of styrene and methyl methacrylate. Moderate to excellent control was achieved with dispersities as low as 1.1 for both poly(methyl methacrylate) and polystyrene. Kinetic studies showed living characteristics, and end group analysis revealed the presence of olefin-terminated polymer chains, suggesting catalytic chain transfer as a competing polymerization mechanism. Although the catalysts are not the fastest Fe ATRP mediators, they are robust and flexible. Using propylene oxide as an initiator, the complexes were active catalysts for the ring-opening polymerization of rac-lactide with moderate control. While the addition of propylene oxide has been reported as an efficient method of converting a metal–halide bond to a metal–alkoxide bond in situ, we show herein that this initiation mechanism can limit polymerization reproducibility and introduce an induction period.

Zwitterionic functionalized MoS2 nanosheets for a novel composite membrane with effective salt/dye separation performance

Polyethersulfone (PES) has been widely used as an ultrafiltration (UF) or nanofiltration (NF) membrane material in multiple industrial fields. But PES is hydrophobic in nature and easily contaminated. Thus, it is necessary to modify the PES membrane surface by physical or chemical methods for improving its hydrophilicity and other function. Herein, MoS2 modified by zwitterionic 2-methacryloyloxy ethyl dimethyl (3-sulfopropyl)-ammonium hydroxide sulfobetaine methacrylate (MoS2-PSBMA) was synthesized with a reverse atom transfer radical polymerization method (RATRP) and used to prepare MoS2-PSBMA/PES composite membranes via conventional phase inversion. The effect of MoS2-PSBMA content on the structure and properties was investigated by SEM, FT-IR, AFM and contact angle measurements. It was found that the hydrophilicity of the composite membrane increased with the content of zwitterionic functionalized MoS2nanosheets. Moreover, the composite membranes possessed a higher water flux (108.3 L m−2 h−1 at 0.6 MPa) and dye retention, 98.2% for Reactive Black 5% and 99.3% for Reactive Green 19. However, the rejection of Na2SO4, MgCl2 NaCl and MgSO4 was low, i.e., 2.2%, 1.2%, 1.1% and 0.3%, respectively. In summary, the synthesized composite membrane exhibited high selectivity for dye/inorganic salts and had a large potential for dye waste water treatment.

A Plasma-Initiated Graft Polymerization of Methyl Methacrylate in the Presence of a Reverse ATRP Catalyst

A plasma-initiated graft polymerization of methyl methacrylate (MMA) was carried out on the high-density polyethylene (HDPE) surface in the presence of the reverse atom transfer radical polymerization (RATRP) catalyst of CuCl2/2,2′-bipyridine (bpy). The polymerization kinetics presented a linear relation with polymerization time. A well-defined PMMA brush was fabricated on the surface, evidenced by the linear growth of molecular weights with conversions and narrow polymer dispersity (Ð = 1.31). Graft amounts were indicated to increase proportionally with the increase of conversions and molecular weights. Subsequently, a solvent-responsive surface was prepared by the block copolymerization of 2-hydroxyethyl methacrylate (HEMA) on the PMMA grafted surface. The polymerization is suggested to proceed via a RATRP mechanism, when plasma radicals could behave similarly as conventional radicals in forming dormant species.

Grafting strategies for the synthesis of active DNase I polymer biohybrids

Protein polymer hybrids play an increasingly important role in therapeutics and biocatalysis. Synthesis of these biohybrids can be achieved by either the grafting-from or grafting-to strategy and are generally thought to be interchangeable. Therefore, when choosing between these two strategies the decision is usually based on polymer accessibility and purification preference. However, in this study, we demonstrated that the choice of the polymer ligation strategy played a significant role in the stability and bioactivity of the final hybrid. Our goal was to prepare a thermally stable DNase I polymer hybrid by utilizing either synthetic strategies. We found that the grafting-from strategy using reversible addition-fragmentation chain transfer polymerization (RAFT) or atom transfer radical polymerization (ATRP) yielded DNase I biohybrids with no activity. Control reactions were used to demonstrate inherent protein deactivation caused by the grafting-from conditions for either ATRP or RAFT polymerization. The grafting-to method yielded active and thermally stable DNase I biohybrids.

The Synthesis of Poly(2,6-dimethyl-1,4-phenylene oxide)/Polymethylmethacrylate Alloy in Aqueous Medium via a One-Pot Method

An environmentally friendly one-pot synthetic method based on green chemistry was developed to prepare thermodynamically partially compatible poly(2,6-dimethyl-1,4-phenylene oxide)/poly(methylmethacrylate) (PPO/PMMA) alloy in water. The oxidative polymerization of 2,6-dimethylphenol in alkaline aqueous solution was firstly conducted and then methyl methacrylate (MMA) was added into the reactor before the end of polymerization. MMA could penetrate into PPO particles and then in situ reverse atom transfer radical polymerization (RATRP) of methyl methacrylate was initiated by 2,2'-azobis[2-(2-imidazolin-2-yl)propane] dihydrochloride after the oxidative polymerization. Both the oxidative polymerization of 2,6-dimethylphenol and RATRP of methyl methacrylate were catalyzed by the complex of CuCl2 and 4-dimethylaminopyridine. Finally, thermodynamically partially compatible PPO/PMMA alloy was successfully prepared which possessed a multi-layer core-shell structure with two polymers embedded in each other.

Sequential synthesis of well-defined poly(vinyl acetate)-block-polystyrene and poly(vinyl alcohol)-block-polystyrene copolymers using difunctional chloroamide-xanthate iniferter

The sequential synthesis of well-defined poly(vinyl acetate)-block-polystyrene copolymer (PVAc-b-PS) and poly(vinyl alcohol)-block-polystyrene copolymer (PVA-b-PS) is challenging due to inactive vinyl acetate monomer and active styrene monomer. In this study, sequential polymerizations of vinyl acetate and styrene monomer were carried out by reversible addition-fragmentation chain transfer (RAFT) and atom transfer radical polymerization (ATRP) using an innovative amide based difunctional chloroamide-xanthate iniferter [S-(1-((3-(2-chloropropanamido)propyl) amino)-1-oxopropan-2-yl) O-ethyl xanthate]. Synthesized difunctional iniferter was very stable under basic condition and allowed the sequential reactions without chain-end modification and purification steps. Synthesized iniferter was first used for xanthate-mediated RAFT polymerization of VAc, followed by ATRP of styrene to achieve controlled molecular weight of PVAc-b-PS with lower polydispersity (≤1.3). Then, PVAc-b-PS was successfully converted to the corresponding PVA-b-PS by hydrolysis. Synthesized block copolymers were characterized by size exclusion chromatography, nuclear magnetic resonance spectroscopy, transmission electron microscopy, and dynamic light scattering.

Correlation of reactivity ratios, transition-metal salts and ester hydrolysis to radical polymerization of electron-deficient comonomers with 2-(N,N-dimethylamino)ethyl methacrylate as the inimer

The radical copolymerization of 2-(N,N-dimethylamino)ethyl methacrylate (DMAEMA, M1) as the inimer and electron-deficient monomers (M2, including methyl methacrylate (MMA), acrylamide (AAm) and N,N-dimethylacrylamide (DMAAm)) with transition-metal salts (such as copperII and ironIII) as the oxidizing agent was correlated to their reactivity ratios (r1 and r2), counterions to transition-metal salts and ester hydrolysis of DMAEMA with an objective to obtain high-molecular weight (MW) branched polymers. As r1 ≈ r2 ≈ 1.0, primary chain initiation occurred even at high MMA conversion during CuSO4-DMAEMA redox-initiated radical polymerization of MMA, and thus the polymerization failed to form high-MW branched PMMA free from linear analogues. As r1 > 1.0 > r2, DMAEMA was preferentially converted into -DMAEMA- units during Fe(NO3)3-DMAEMA redox-initiated aqueous radical polymerization of AAm/DMAAm, but N,N-dimethylaminoethanol formed via hydrolysis led to lower-MW chains. Under optimal conditions with minimum hydrolysis, FeCl3-DMAEMA redox-initiated aqueous radical polymerization of DMAAm proceeded via redox-initiated reverse atom transfer radical polymerization (ATRP) generating DMAEMA-terminated chains with a carbon-chloride terminal. FeII-catalyzed self-condensing ATRP led to high-MW branched PDMAAm even under aerobic conditions.

Investigation of the effect of mesoporous diatomaceous earth particles on RATRP of styrene and butyl acrylate

Mesoporous diatomite nanoplatelets were employed to prepare various poly (styrene-co-butyl acrylate)/diatomite nanocomposites by in situ reverse atom transfer radical polymerization of styrene and butyl acrylate. Fourier-transform infrared spectroscopy, thermogravimetric analysis (TGA), and nitrogen adsorption/desorption isotherm were employed for evaluating some properties of the pristine diatomite nanoplatelets. Evaluation of pore size distribution and morphological studies were also performed by scanning and transmission electron microscopy. Conversion and molecular weight determinations were carried out using gas and size exclusion chromatography, respectively. Addition of 3 wt% pristine mesoporous diatomite nanoplatelets leads to an increase in conversion from 77% to 92%. Molecular weight of poly (styrene-co-butyl acrylate) chains increases from 17,348 g mol−1 to 21,346 g mol−1 with the addition of 3 wt% pristine mesoporous diatomite nanoplatelets; however, polydispersity index values increases from 1.38 to 1.65. Increasing thermal stability of the nanocomposites is demonstrated by TGA. Differential scanning calorimetry shows an increase in glass transition temperature from 35.5°C to 39.4°C with the addition of 3 wt% mesoporous diatomite nanoplatelets.

Anticoagulant polyurethane substrates modified with poly(2-methacryloyloxyethyl phosphorylcholine) via SI-RATRP.

A novel catalyst system of Reverse Atom Transfer Radical Polymerization (RATRP) to prepare Polyurethane (PU) films modified by poly(2-methacryloyloxyethyl phosphorylcholine) (pMPC) was studied in this article. In this system, PU film was pretreated by LaCl3/CA ethanol solution to obtain a hydrated surface allowing more initiators to be immobilized on it. Moreover, complexes composed of silane coupling agent 3-chloropropyltrimethoxysilane (CPTM), chlorhexidine acetate (CA) and lanthanum(III) worked as ligands of copper ions as a whole during RATRP process. PU films before and after modification were characterized by X-ray photoelectron spectroscopy (XPS) and static contact angle (SCA) to confirm that pMPC chains were successfully grafted from the substrates. Results of Plasma recalcification time assay, platelet adhesion test indicated excellent blood compatibility. Furthermore, the antibacterial activity of the material have been improved which proved by adhesion test of E.coil.

Mathematical modeling of reverse atom transfer radical polymerization in miniemulsion

In this work, we study the reverse atom transfer radical polymerization in miniemulsion using a water-soluble initiator. This study is motivated by the technological advantages of performing polymerizations in dispersed systems, and the attractive possibilities of controlled radical polymerization techniques to produce tailor made polymers. A mathematical model for this system is presented. The model predicts average molecular properties as well as the full molecular weight distribution (MWD) for different experimental conditions. The method of moments is applied for calculating average properties and the probability generating function (pgf) technique is used to model the MWD. The model is based on the mass balance equations of the reacting species. It takes into account the reactions in both the aqueous and organic phases and the mass transfer between them. Predicted conversions, average molecular weights, polydispersity indexes and MWDs for different experimental conditions agree well with experimental data reported in the literature.