Atom Transfer Radical Polymerization Approach Research Articles

Mechanically Driven Atom Transfer Radical Polymerization by Piezoelectricity.

Targeting sustainable and eco-friendly polymer synthesis, we demonstrate here a synergistically catalyzed atom transfer radical polymerization (ATRP) induced and controlled by interplay between ball milling (BM) and piezoelectric nanoparticles (piezoNPs). BM-induced electron transfer can be achieved through piezoNPs deformation under impact force, serving as an external stimulus to mediate polymerization. The ppm level of copper loading is sufficient in fabrication of a polymer with well-defined molecular weight and low polydispersity. High-molecular-weight polymers ranging from 33 to 74 kDa were prepared successfully through DMSO-assisted grinding. Besides, its good performance on availability of water as liquid-assisted grinding additive, the recyclability of piezoNPs, and the formation of cross-linker-free composite resin make our ATRP approach a green and practical option alongside the existent heat-, electro-, and photo-induced methods.

Hybrid "Kill and Release" Antibacterial Cellulose Papers Obtained via Surface-Initiated Atom Transfer Radical Polymerization.

Infectious diseases triggered by bacteria cause a severe risk to human health. To counter this issue, surfaces coated with antibacterial materials have been widely used in daily life to kill these bacteria. The substrates enabled with a hybrid kill and release strategy can be employed not only to kill the bacteria but also to wash them using external stimuli (temperature, pH, etc.). Utilizing this concept, we develop thermoresponsive antibacterial-cellulose papers to exhibit hybrid kill and release properties. Thermoresponsive copolymers [p(NIPAAm-co-AEMA)] are grafted on cellulose papers using a surface-initiated atom transfer radical polymerization approach for bacterial debris release. Later for antibacterial properties, silver nanoparticles (AgNPs) are immobilized on thermoresponsive copolymer-grafted cellulose papers using electrostatic interactions. We confirm the thermoresponsive copolymer grafting and AgNP coating by attenuated total reflection Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, and scanning electron microscopy. Thermoresponsiveness and reusability of the modified cellulose papers are confirmed through water contact angle measurements. The interaction potency between AgNPs and modified cellulose is validated by inductively coupled plasma atomic emission spectroscopy analysis. Gram-negative bacteria Escherichia coli (E. coli DH5-α) is used to demonstrate antibacterial hybrid kill and release performance. Agar-diffusion testing demonstrates the antibacterial nature of the modified cellulose papers. The fluorescence micrograph reveals that modified cellulose papers can effectively release almost all the dead bacterial debris from their surfaces after thermal stimulus wash. The modified cellulose paper surfaces are expected to have wide applications in the field of exploring more antibacterial and smart surfaces.

Experimental Investigation of Methyl Methacrylate in Stirred Batch Emulsion Reactor: AGET ATRP Approach.

This study examines the ab initio emulsion atom transfer radical polymerization (ATRP) initiated by an eco-friendly reducing agent to produce poly(methyl methacrylate) (PMMA) polymer with controlled characteristics in a 2 L stirred batch reactor. The effect of the reaction temperature, surfactant concentration, monomer to water ratio, and stirring speed was thoroughly investigated. The results showed that PMMA coagulation becomes quite severe at a certain temperature threshold. However, the coagulation could be avoided at mild reaction temperature, since the outcomes showed that loading more surfactant to the system under high mixing speed has balanced the polymer mixture and yielded high monomer conversion. The PMMA product was analyzed by gravimetry and GPC measurements and after 5 h of polymerization at a reaction temperature of 50 °C, monomer conversion of 64.1% was obtained, and PMMA polymer samples produced had an average molar mass of 4.5 kg/mol and a polydispersity index of 1.17. The structure of the PMMA polymer was successfully proved by FTIR and nuclear magnetic resonance (NMR) spectroscopy. The results confirm the living feature of MMA AGET ATRP in emulsion medium and recommend further investigation for other types of surfactant.

Dual Stimuli-Responsive Block Copolymers for Controlled Release Triggered by Upconversion Luminescence or Temperature Variation.

An amphiphilic block copolymer (BCP) which contains both photoresponsive and thermoresponsive blocks was synthesized by the atom transfer radical polymerization approach. Meanwhile, a new core/shell type of the upconversion nanoparticle (UCNP) LiYF4:Yb3+0.25,Tm3+0.01@LiYF4:Yb3+0.2 was successfully synthesized. By encapsulating UCNPs inside the micelles of the BCP and incorporating Nile red (NR) into the UCNP@BCP hybrid nanoparticles as a model drug, controlled release of the drug by the dual-stimuli BCP could be studied. After exposing the UCNP-loaded micellar solution to near-infrared (NIR) light, it was found that the UV light pumped from UCNPs could disrupt the polymer micelles and the fluorescence intensity of NR decreased with the increase of the irradiation time of the NIR light. The thermoresponsive study indicated that the fluorescence intensity of NR decreased with the increase of temperature of the micellar solution because of the release of NR into water arising from the contraction of the amphiphilic BCP.

Preparation of a dual cored hepatoma-specific star glycopolymer nanogel via arm-first ATRP approach.

A reductase-cleavable and thermo-responsive star-shaped polymer nanogel was prepared via an “arm-first” atom transfer radical polymerization approach. The nanogel consists of a thermo- and redox-sensitive core and a zwitterionic copolymer block. The dual sensitive core is composed of poly(N-isopropylacrylamide) that is formed by disulfide crosslinking of N-isopropylacrylamide. The zwitterionic copolymer block contains a poly(sulfobetaine methacrylate) component, a known anti-adsorptive moiety that extends blood circulation time, and a lactose motif of poly(2-lactobionamidoethyl methacrylamide) that specifically targets the asialoglycoprotein receptors (ASGP-Rs) of hepatoma. Doxorubicin (DOX) was encapsulated into the cross-linked nanogels via solvent extraction/evaporation method and dialysis; average diameter of both blank and DOX-loaded nanogels was ~120 nm. The multi-responsiveness of nanogel drug release in different temperatures and redox conditions was assessed. After 24 h, DOX release was only ~20% at 30°C with 0 mM glutathione (GSH), whereas over 90% DOX release was observed at 40°C and 10 mM GSH, evidence of dual responsiveness to temperature and reductase GSH. The IC50 value of DOX-loaded nanogels was much lower in human hepatoma (HepG2) cells compared to non-hepatic HeLa cells. Remarkably, DOX uptake of HepG2 cells differed substantially in the presence and absence of galactose (0.31 vs 1.42 µg/mL after 48 h of incubation). The difference was non-detectable in HeLa cells (1.21 vs 1.57 µg/mL after 48 h of incubation), indicating that the overexpression of ASGP-Rs leads to the DOX-loaded lactosylated nanogels actively targeting hepatoma. Our data indicate that the lactose-decorated star-shaped nanogels are dual responsive and hepatoma targeted, and could be employed as hepatoma-specific anti-cancer drug delivery vehicle for cancer chemotherapy.

Preparation of Molecularly Imprinted Regenerated Cellulose Composite Membranes by Surface-Initiated Atom Transfer Radical Polymerization Method for Selective Recognition of Lysozyme

Novel types of polymeric membranes containing molecular recognition sites for selective recognition of lysozyme (Lyz) have been prepared using a surface-initiated atom transfer radical polymerization approach. The surface compositions of the regenerated cellulose (RC) membranes before and after polymerization were characterized by X-ray photoelectron spectroscopy analysis, which demonstrated that the molecular imprinting layer was successfully fabricated onto the surface of RC membranes. The selective recognition of Lyz molecularly imprinted membranes (Lyz–MIMs) for Lyz was evaluated by protein adsorption penetration tests. It was found that Lyz–MIMs have excellent adsorption capacity and specific recognition for Lyz adsorption from aqueous solutions. In the presence of competitive substances, a separation factor of 23.08 was achieved. The molecularly imprinted RC composite membrane is promising for separation and purification of specific protein compositions in biosamples. In addition, it may have good p...

Coupled atom transfer radical coupling and atom transfer radical polymerization approach for controlled grafting from poly(vinylidene fluoride) backbone

A new “grafting from” strategy for grafting of different monomers (methacrylates, acrylates, and acrylamide) on poly(vinylidene fluoride) (PVDF) backbone is designed using atom transfer radical coupling (ATRC) and atom transfer radical polymerization (ATRP). 4-Hydroxy TEMPO moieties are anchored on PVDF backbone by ATRC followed by attachment of ATRP initiating sites chosen according to the reactivity of different monomers. High graft conversion is achieved and grafting of poly(methyl methacrylate) (PMMA) exhibits high degree of polymerization (DPn = 770) with a very low graft density (0.18 per hundred VDF units) which has been increased to 0.44 by regenerating the active catalyst with the addition of Cu(0). A significant impact on thermal and stress–strain property of graft copolymers on the graft density and graft length is noted. Higher tensile strain and toughness are observed for PVDF-g-PMMA produced from model initiator but graft copolymer from pure PVDF exhibits higher tensile strength and Young's modulus. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014, 52, 995–1008

Covalent poly(methyl methacrylate) nanostructures on functionalized Si(100) surfaces

Material properties are strongly affected by the presence of surface chemical functionalities. In this study we show a platform for fabricating robust poly(methyl methacrylate) molecular architectures covalently bound to silylated Si(100) substrates, by an atom transfer radical polymerization approach. Infrared attenuated total reflectance spectra have shown increasing poly(methyl methacrylate) signals upon increasing reaction time and can be used to monitor the growth of these hybrid inorganic/organic structures. The chemical composition of these surface structures was investigated by X-ray photoelectron spectra. Surface morphology studies were carried out by atomic force microscopy and lithography. In our reaction conditions, the thickness of poly(methyl methacrylate) on Si(100) can be modulated in the nanometer range. Quantum mechanical DFT calculations have been performed to estimate the growth rate.

Crosslinked epoxy microspheres: Preparation, surface‐initiated polymerization, and use as macroporous silica porogen

AbstractIn this article, we report the preparation of crosslinked epoxy microspheres with diameters of 5–10 μm prepared via phase‐inverted phase separation induced by polymerization in the thermosetting blend of epoxy and poly(ε‐caprolactone). The surfaces of the epoxy microspheres were functionalized to bear 2‐bromopropionyl groups, which were further used as initiators to obtain poly(glycidyl methacrylate) (PGMA) grafted epoxy microspheres via the surface‐initiated atom transfer radical polymerization approach. The PGMA‐grafted epoxy microspheres were then employed to react with 3‐aminopropyltrimethoxylsilane (APTMS) to obtain the functionalized epoxy microspheres, the surface of which contained a great number of trimethoxysilane groups. A co‐sol–gel process between the APTMS‐functionalized epoxy microspheres and tetraethoxysilane was performed, and organic–inorganic glassy solids were obtained. The organic–inorganic glasses were used as precursors for accessing macroporous silica materials via pyrolysis at elevated temperatures. The hierarchical porosity of the resulting macroporous silica was investigated by means of field emission scanning electronic microscopy, transmission electronic microscopy, and surface‐area Brunauer–Emmett–Teller (BET) measurements. We found that the macroporous silica possessed BET surface areas in the range 183.9–235.2 m2/g, depending on the compositions of their precursors. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013

“One‐step” Preparation of Thiol‐Ene Clickable PEG‐Based Thermoresponsive Hyperbranched Copolymer for In Situ Crosslinking Hybrid Hydrogel

A well-defined poly(ethylene glycol) based hyperbranched thermoresponsive copolymer with high content of acrylate vinyl groups was synthesized via a "one-pot and one-step" deactivation enhanced atom transfer radical polymerization approach, which provided an injectable and in situ crosslinkable system via Michael-type thiol-ene reaction with a thiol-modified hyaluronan biopolymer. The hyperbranched structure, molecular weight, and percentage of vinyl content of the copolymer were characterized by gel permeation chromatography and (1)H NMR. The lower critical solution temperature of this copolymer is close to body temperature, which can result in a rapid thermal gelation at 37 °C. The scanning electron microscopy analysis of crosslinked hydrogel showed the network formation with porous structure, and 3D cell culture study demonstrated the good cell viability after the cells were embedded inside the hydrogel. This injectable and in situ crosslinking hybrid hydrogel system offers great promise as a new class of hybrid biomaterials for tissue engineering.

Nano-sized Li–Fe composite oxide prepared by a self-catalytic reverse atom transfer radical polymerization approach as an anode material for lithium-ion batteries

A novel Self-catalytic Reverse Atom Transfer Radical Polymerization (RATRP) approach that can provide the radical initiator and the catalyst by the system itself is used to synthesize a nano-sized Li–Fe composite oxide powder in large scale. Its crystalline structure and morphology have been characterized by X-ray diffraction and scanning electron microscopy. The results reveal that the composite is composed of nano-sized LiFeO 2 and Fe 3O 4. Its electrochemical properties are evaluated by charge/discharge measurements. The results show that the Li–Fe composite oxide is an excellent anode material for lithium-ion batteries with good cycling performance (1249 mAh g −1 at 100th cycle) and outstanding rate capability (967 mAh g −1 at 5 C). Such a self-catalytic RATRP approach provides a way to synthesize nano-sized iron oxide-based anode materials industrially with preferable electrochemical performance and can also be applied in other polymer-related area.

Highly Sensitive Detection of Protein Toxins by Surface Plasmon Resonance with Biotinylation-Based Inline Atom Transfer Radical Polymerization Amplification

Ultrasensitive detection of proteins is of great importance to proteomics studies. We report here a method to enhance detection sensitivity in surface plasmon resonance (SPR) spectroscopy by coupling a polymerization initiator to a biospecific interaction and inducing inline atom transfer radical polymerization (ATRP) for amplifying SPR response. Bacterial cholera toxin (CT) is chosen as the model protein that has been covalently immobilized on the surface for demonstrating the principle. The specific recognition is achieved by use of biotinylated anti-CT, which allows initiators with a biotin tag to be fixed at the protein binding site through a neutravidin bridge and triggers the localized growth of polymer brushes of poly(hydroxyl-ethyl methacrylate) (PHEMA) via an ATRP mechanism. To further enhance the signal, a second ATRP reaction is conducted that takes advantage of the hydroxyl groups of PHEMA brushes from the first step to form hyperbranched polymers onto the sensing surface. The two consecutive ATRP steps significantly improve SPR detection, allowing low amounts of CT that yield no direct measurement to be quantified with large signals. The resulting polymer film has been characterized by optical and atomic force microscopy. Ascorbic acid (AA) is employed as deoxygen reagent in the catalyst mixture that effectively suppresses oxygen interference, shortening the reaction time and making it possible for applying this ATRP approach to flow injection based SPR detection. A calibration curve of PHEMA amplification for CT detection based on surface coverage has been obtained that displays a correlation in a range from 8.23 x 10(-15) to 3.61 x 10(-12) mol/cm(2) with a limit of detection of 6.27 x 10(-15) mol/cm(2). The versatile biotin-neutravidin interaction used here should allow adaptation of ATRP enhancement to many other systems that include DNA, RNA, peptides, and carbohydrates, opening new avenues for ultrasensitive analysis of biomolecules with flow-injection assay and SPR spectroscopy.

Fabrication of hybrid nanocomposites with polystyrene and multiwalled carbon nanotubes with well-defined polystyrene via multiple atom transfer radical polymerization

The PS-grafted multiwalled carbon nanotubes (MWNTs) were produced by the bromo-ended PS (PS-Br) and pristine MWNTs in 1,2-dichlorobenzene at 110 °C for 72 h via atom transfer radical polymerization (ATRP). Bromo-ended PS (PS-Br) used as an initiator for the functionalization of MWNTs was synthesized with styrene by ATRP conditions using CuBr and N,N,N′,N′,N″-pentamethyldiethylenetriamine as catalyst. The PS-grafted MWNTs were fully characterized by 1H-NMR, FT-IR, DSC, TGA, and SEM. The PS-grafted MWNTs were found to be highly soluble in a variety of organic solvents. The PS was chemically attached to the surfaces of MWNTs via ATRP approach, and the grafting amount of PS was 40–90%. From TGA and DSC measurements, the PS-grafted MWNTs were decomposed at lower temperature compared to that of PS-Br, and the functionalization of MWNTs increased the glass-transition temperature (Tg) of the grafted PS. The PS/PS-grafted MWNTs nanocomposites were prepared with PS and PS-grafted MWNTs by solution mixing in dimethylformamide (DMF). The resulting nanocomposites were found to be the homogeneous dispersion of PS-grafted MWNTs in PS matrix via aromatic (π–π) interactions between PS and PS-grafted MWNTs as determined by SEM and TEM.

Poly(2‐(methacryloyloxy) ethyl phosphorylcholine)‐functionalized multi‐walled carbon nanotubes: Preparation, characterization, solubility, and effects on blood coagulation

AbstractWater‐soluble multi‐walled carbon nanotubes (MWNTs) were prepared via surface‐initiated atom transfer radical polymerization (ATRP) of 2‐(methacryloyloxy) ethyl phosphorylcholine (MPC) from carbon nanotubes (CNTs). The success of the surface functionalization of MWNTs with poly(2‐(methacryloyloxy) ethyl phosphorylcholine) (pMPC) was ascertained using fourier transform infrared spectrophotometry (FTIR), thermogravimetric analysis (TGA), hydrogen nuclear magnetic resonance (1H‐NMR), and transmission electron microscopy (TEM). Different from the results of the previous work, in our work, we demonstrate that the amount of pMPC on CNTs can be easily regulated by ATRP approach. In addition, from TGA results, a linear relationship between the weight loss fraction of MWNT‐pMPC and the weight of MPC fed and as high as 48.1% weight loss of MWNT‐pMPC (MWNTs grafted by pMPC) are observed. Through TEM, the core‐shell structure of MWNT‐pMPC is clearly observed, which is also different from the previous report. The pMPC‐modified MWNTs are highly soluble, which can also resist pH and saline concentration changes and remain stable in physiological environment. PMPC‐modified MWNT does not significantly affect the blood coagulation as demonstrated in plasma recalcification time (PRT) test. These highly soluble MWNTs are expected to enable their wide use in biomedical areas. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009

Novel synthesis of poly(methyl methacrylate) brush encapsulated silica particles

AbstractSilica (SiO2)‐crosslinked polystyrene (PS) particles possessing photofunctional N,N‐diethyldithiocarbamate (DC) groups on their surface were prepared by the free‐radical emulsion copolymerization of a mixture of SiO2 (diameter = 20 nm), styrene, divinyl benzene, 4‐vinylbenzyl N,N‐diethyldithiocarbamate (VBDC), and 2‐hydroxyethyl methacrylate with a radical initiator under UV irradiation. In this copolymerization, the inimer VBDC had the formation of a hyperbranched structure by a living radical mechanism. The particle sizes of such core–shell structures [number‐average particle diameter (Dn) = 35–40 nm] were controlled by the variation of the feed amounts of the monomers and surfactant, or emulsion system. The size distributions were relatively narrow (weight‐average particle diameter/Dn ≈ 1.05). These particles had DC groups on their surface. Subsequently, poly(methyl methacrylate) brush encapsulated SiO2 particles were synthesized by the grafting from a photoinduced atom transfer radical polymerization approach of methyl methacrylate initiated by SiO2‐crosslinked PS particles as a macroinitiator. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008

Architecture of Prototype Copolymer Brushes by Grafting-from ATRP Approach from Functionalized Alternating Comb-Shaped Copolymers

Atom transfer radical polymerization (ATRP) was applied to a novel synthesis of prototype copolymer brushes. The procedure included the following steps: (1) free-radical copolymerization of vinylbenzyl-terminated polystyrene (PS-VB) macromonomer and N-(4-hydroxyphenyl)maleimide gave well-defined alternating comb-shaped copolymers, (2) subsequent esterification reaction [N-(4-hydroxyphenyl)maleimide sites] of such comb-shaped copolymer with 2-bromoisobutyryl bromide yielded a comb-shaped polyinitiator, and (3) the grafting-from ATRP method of methyl methacrylate (MMA) using comb-shaped polyinitiator provided PS/poly(methyl methacrylate) (PMMA) alternating copolymer brushes. Dilute solution properties and morphological results of both comb-shaped polyinitiator and prototype copolymer brushes were investigated by static and dynamic light scattering and transmission electron microscopy. As a result, prototype copolymer brush composed of short aspect ratio changed the shape from ellipsoid to starlike conforma...

Synthesis of polymer particles possessing radical initiating sites on the surface by emulsion copolymerization and construction of core–shell structures by a photoinduced atom transfer radical polymerization approach

AbstractThe crosslinked polystyrene particles possessing photofunctional N,N‐diethyldithiocarbamate groups on their surface were prepared by free‐radical emulsion copolymerization of a mixture of styrene, divinylbenzene and 4‐vinylbenzyl N,N‐diethyldithiocarbamate with redox system as an initiator under UV irradiation. In this copolymerization, the inimer 4‐vinylbenzyl N,N‐diethyldithiocarbamate acted the formation of hyperbranched structures by living radical photopolymerization. The particle sizes (number‐average particle diameter = 214–523 nm) were controlled by varying the feed amount of surfactant and size distributions were relatively narrow. Subsequently, core–shell particles were synthesized by photoinduced atom transfer radical polymerization approach of methyl methacrylate initiated by photofunctional polystyrene particles as a macroinitiator. Such core–shell particles were stabilized sterically by grafted chains in organic solvents. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 1771–1777, 2007

Grafting Boron Nitride Nanotubes: From Polymers to Amorphous and Graphitic Carbon

In this article, using an atom transfer radical polymerization approach, for the first time polystyrene (PS) and polymethyl methacrylate (PMMA) were grafted covalently on boron nitride nanotubes (BNNTs). Then, a technique was developed to fabricate novel amorphous or graphitic carbon−BNNTs composites with a perfect physical contact between the two phases using the polymer-functionalized BNNTs. BNNTs−carbon-balls composite structures were first successfully fabricated. Other experimental route revealed that a C−BN compound nanotubular nanostructure can be fabricated by using polyvinyl pyrrolidone wrapped BNNTs as an effective precursor, which possess well-defined composition variations and a clear interface between the carbon and BN tubular fragments. The obtained polymer-functionalized BNNTs and carbon−BNNTs composites are useful for the mechanical enhancement of polymeric matrixes and in various electrochemical devices.

Front Cover: Macromol. Rapid Commun. 14/2005

Front Cover: Carbon spheres were covalently functionalized with polymers by using an in situ atom transfer radical polymerization approach, resulting in significantly improved dispersibility in organic solvents. SEM and TEM observations show a uniform distribution of the carbon spheres in the continuous polymer phase. Further details can be found in the Communication by Y. Z. Jin, C. Gao,* H. W. Kroto, and T. Maekawa on page 1133.

Constructing amphiphilic polymer brushes on the convex surfaces of multi-walled carbon nanotubes by in situ atom transfer radical polymerization

A fascinating nanoobject, amphiphilic polymer brushes with a hard core of multi-walled carbon nanotubes (MWNTs) and a relatively soft shell of polystyrene-block-poly(acrylic acid) (PS-b-PAA), was easily constructed by in situ atom transfer radical polymerization (ATRP) of styrene followed by tert-butyl acrylate on the modified convex surfaces of MWNTs (MWNT-PS) followed by hydrolysis of the grafted poly(tert-butyl acrylate) (PtBA) blocks. The structure and morphology of the as-prepared hybrid nanomaterials were characterized and confirmed by electron microscopy (TEM and SEM), nuclear magnetic resonance (NMR) spectrometry, and thermogravimetric analysis (TGA). The results showed that both styrene and acrylate types of ATRP-active vinyl monomers can be easily initiated and then propagated on the MWNT sidewalls via the in situ ATRP approach, and the length of the PtBA blocks increases with increasing tBA : MWNT-PS weight feed ratio. We believe that the breakthrough associated with formation of such a complex nanoobject would open a door for the fabrication of novel functional carbon nanotube-based nanomaterials or nanodevices with designable structure and tailor-made properties.