Atom Transfer Radical Precipitation Polymerization Research Articles

Molecularly Imprinted Nanoparticles Synthesized by Electrochemically Mediated Atom Transfer Radical Precipitation Polymerization

AbstractNanometer molecularly imprinted polymers (nano‐MIPs) spherical particles with specific recognition of sialic acid (SA) are synthesized by electrochemically mediated atomic transfer radical polymerization combined with the precipitation method. SA is used as template molecules,4‐vinylphenylboronicacid as functional monomer, and ethylene glycol dimethacrylate as the crosslinking agent. The successful synthesis of spherical nano‐MIPs is verified by Fourier transform infrared spectroscopy, scanning electron microscope, and Malvern particle size instruments. The effects of the potential adjustment on the morphology, size, and particle size distribution of MIP particles are further investigated. By adjusting the potential for polymerization, nanoparticles with average sizes of 160.32, 275.87, and 331.99 nm are obtained. The recognition performance of nano‐MIPs for SA is characterized by a UV–vis spectrophotometer and the satisfactory imprinting factor is 1.54.

Controlled preparation of molecularly imprinted polymer microspheres with surface uncrosslinked glycoprotein binding cavities

Molecularly imprinted polymers (MIPs) are synthetic receptors with tailor-made recognition sites for target molecules. Their high affinity and selectivity, excellent stability, easy preparation, and low cost make them promising substitutes to biological receptors (e.g., antibody and enzyme) in many applications where molecular recognition is important. Despite significant progress made in the imprinting of small templates, the imprinting of biomacromolecules (e.g., proteins) remains a big challenge because of their large sizes, complexed structures, and conformational variability. These inherent characteristics of biomacromolecules lead to many significant problems for the resulting macromolecularly imprinted polymers (mMIPs) such as laborious removal of large templates and their slow access to the binding sites. Recent years have witnessed much efforts being devoted to the development of mMIPs due to their great potential in proteome analysis, clinical diagnostics, and biomedicine. So far, some useful strategies have been developed for the imprinting of proteins, mainly including the bulk polymerization method, epitope imprinting strategy, and surface imprinting approach. Among them, the surface imprinting approach has been most widely used because it can readily lead to mMIPs with higher efficiency for removing large templates and more rapid template binding kinetics. Nevertheless, the presently developed mMIPs normally have crosslinked template binding sites, whose rigid structures might have negative influence on the removal of large templates and template binding kinetics. In this sense, the development of mMIPs with more flexible biomacromolecular binding cavities (e.g., uncrosslinked ones) should be useful for solving the above problems. To our knowledge, however, only rather limited numbers of publications relating to mMIPs with uncrosslinked binding sites have been disclosed, which are all based on the use of self-assembled monolayer strategy. The development of versatile new approaches for preparing mMIPs with uncrosslinked binding sites and good molecular imprinting effect is still highly desirable. We demonstrate a facile and efficient new approach for the controlled preparation of MIP microspheres with surface uncrosslinked glycoprotein binding sites. It involves the first one-pot synthesis of uniform “living” polymer microspheres with both surface-bound epoxy groups and alkyl halide groups (i.e., atom transfer radical polymerization (ATRP)-initiating groups) via atom transfer radical precipitation polymerization, their surface modification with 3-aminophenylboronic acid (APBA) for introducing surface phenylboronic acid moieties and surface immobilization of a glycoprotein (ovalbumin (OVA)), subsequent use of the “living” polymer microspheres with surface-immobilized OVA as the ATRP initiator for the controlled grafting of poly( N -isopropylacrylamide) (PNIPAAm) brushes, and final removal of OVA. A series of MIP microspheres with surface uncrosslinked OVA binding sites were readily obtained following the above procedure by just changing the polymerization time for grafting PNIPAAm brushes, and their morphologies, chemical structures, surface hydrophilicity, water dispersion stability, and template binding properties were characterized in detail. The experimental results demonstrated that the above approach could effectively provide MIPs with excellent recognition ability toward OVA in the aqueous medium. The surface hydrophilicity and water dispersion stability of MIP microspheres were largely improved due to their surface-grafting of hydrophilic polymer brushes. Moreover, the chain length of PNIPAAm brushes showed significant influence on the template binding properties of MIP microspheres, and the best template binding capacity and specific binding were achieved for MIPs only when the thickness of PNIPAAm layers was close to the total length of the diameter of OVA plus the length of the surface-attached phenylboronic acid unit. Furthermore, the optimal MIP also exhibited good selectivity toward OVA over other proteins. The strategy presented here paves a new way for controlled and efficient preparation of glycolprotein-imprinted polymer microspheres with good molecular recognition capability.

Solid-phase extraction of aflatoxins using a nanosorbent consisting of a magnetized nanoporous carbon core coated with a molecularly imprinted polymer.

A core consisting of nanoporous carbon (MNPC) and magnetized with Co3O4 was coated with a molecularly imprinted polymer (MIP) by atom transfer radical precipitation polymerization. Ethyl 3-coumarincarboxylate was used as a pseudo-template to give a MIP that has a fairly specific recognition capability for aflatoxins. Batch rebinding studies were carried out to determine the specific adsorption equilibrium and specific recognition. Extraction is achieved in a single step by mixing and vortexing the sample extract with the Co-MNPC@MIP. The loaded nanosorbent was then magnetically separated and eluted with acetonitrile/water (6/4, v/v). The aflatoxins were then quantified by HPLC. Under optimal conditions, the detection limits for aflatoxins typically are 0.05-0.07ngmL-1, recoveries from spiked corn are found to be 75.1 to 99.4%, and relative standard deviations range from 1.7 to 5.1 (n= 6). Graphical abstract Poly(methacrylic acid) was imprinted with the pseudo-template ethyl 3-coumarincarboxylate by atom transfer radical precipitation polymerization on the surface of cobalt-derived magnetic nanoporous carbon (Co-MNPC). This nanosorbent was used for the magnetic solid phase extraction of aflatoxins, followed by HPLC analysis.

Selective recognition and preliminary separation of hepatoprotective component silybin from milk thistle seeds by the prepared core–shell magnetic molecularly imprinted polymer

Using hepatoprotective component silybin as the template, MAA as the functional monomer, EGDMA as the cross linker, acetonitrile as the solvent, and Fe3O4 as the magnetic substrate, the silybin magnetic molecularly imprinted polymer(S-MIP) was successfully prepared by the reverse atom transfer radical precipitation polymerization(RATRP), and non-ion imprinted polymer(NIP) was also synthesized by the same procedure only in the absence of silybin. On the basis of computer simulation and L9(34) orthogonal array design matrix, the optimal preparation conditions were finally obtained as follows that the molar ratio of silybin, MAA, and EGDMA was 1:5:60. The prepared materials were respectively characterized by SEM, XRD, FT-IR, VSM and TGA, and the kinetic analyses explored that the adsorption process of S-MIP was better describled by the pseudo-second order kinetic equation, meanwhile, scatchard analysis illustrated that the heterogeneous binding sites existed in S-MIP. Both the selectivity factor α (2.232) and the relative selectivity factor β (2.201) of S-MIP showed the aim material had the excellent specific recognition capacity and selection adsorption property to silybin. Additionally, the recycling reuse experiments explored S-MIP was of a good stability and could be used repeatedly at least five times with only 15.8% decrease of adsorption capacity when applied in the fifth experiment, and the evaluation experiments by HPLC for silybin extraction from the medicinal herb milk thistle seeds indicated that S-MIP had the potential application in separating the natural hepatoprotective component silybin from the herbal plants.

A fluorescent molecularly imprinted polymer sensor synthesized by atom transfer radical precipitation polymerization for determination of ultra trace fenvalerate in the environment

In this study, novel fluorescence molecularly imprinted polymers (FMIPs) were prepared via atom transfer radical precipitation polymerization (ATRPP) for the optical detection of trace fenvalerate (FE).

Preparation of Magnetic Imprinted Core–Shell Particles Through Reverse Atom Transfer Radical Precipitation Polymerization for Selective Removal of Sulfamethazine

Preparation of Magnetic Imprinted Core–Shell Particles Through Reverse Atom Transfer Radical Precipitation Polymerization for Selective Removal of Sulfamethazine

Preparation and evaluation of chiral selective cation-exchange PMMA–PNIPAm thermal-sensitive membranes

Selective cation-exchange membranes are placing a key role in separation processes. The application of selective cation-exchange membranes is wide since there are many kinds of mixtures needed to be separated for reuse. In this study, a facile and efficient one-pot approach was used to obtain monodispersed methyl methacrylate–N-isopropyl acrylamide (MMA–NIPAm) polymer by atom transfer radical precipitation polymerization (ATRPP) and then MMA–NIPAm chiral selective separation membranes were prepared for separating racemic equol. Firstly, using dodecylbenzenesulfonyl chloride (DBSC) as the initiator, bipyridine (bipy)/CuCl as the catalyst system, acetonitrile as the solvent, and S-equol as template molecule by which a MMA–NIPAm copolymer was synthesized and it was characterized by TEM, FTIR, TGA, UV–vis absorption spectrum, and dynamic layer scattering analysis. Lastly, MMA–NIPAm chiral separation membranes were prepared by casting 3 wt% of MMA–NIPAm copolymer dimethyl formamide (DMF) solution on a rimmed glass plate and evaporated the solvent completely at 100 °C under vacuum. Then, the PMMA–PNIPAm chiral selective cation-exchange membranes were prepared by immersing in methanol/acetic acid (95:5, v/v) to remove the template molecules. Most worthy of mention was that the prepared chiral selective separation membranes could separate S-equol and R-equol from the mixture of racemic equol. In application of a thermo-responsive monomer, the separation ability of the prepared PMMA–PNIPAm chiral separation membranes could be tunable according to environment temperature changes.

Preparation of silica-based surface-imprinted core–shell nanoadsorbents for the selective recognition of sulfamethazine via reverse atom transfer radical precipitation polymerization

In this work, core–shell-structured silica-based surface molecularly imprinted nanoadsorbents (SMIPs) were prepared using a facile and general method that combined reverse atom transfer radical precipitation polymerization (RATRPP) and a surface imprinting nanotechnique. The resulting nanoadsorbents were then used to improve selective recognition and achieve the rapid removal of sulfamethazine (SMZ) from water. A modified one-step Stober method was used to prepare monodisperse vinyl-functionalized silica spheres 250 nm in size. Subsequently, an imprinted polymer nanoshell (only 25 nm thick) was uniformly coated onto the surfaces of the hybrid silica spheres in a two-step polymerization process. The characteristics (i.e., isotherms, kinetics, and mechanism) of the adsorption of SMZ onto SMIPs from aqueous solution were systematically studied using batch experiments. The adsorption capacity increased with increasing initial concentration and contact time. The nonlinear Langmuir, Freundlich, and Temkin models were used to analyze equilibrium data, and these data were found to be best represented by the Langmuir isotherm, which yielded a high maximum monolayer adsorption capacity of 76.34 μmol g−1 due to the effective sites located in the thin imprinted nanoshell. The adsorption process rapidly reached equilibrium and the data were best described by a pseudo-second-order rate model. The adsorption mechanism was mainly governed by intraparticle diffusion. The SMIPs adsorbed more SMZ than nonimprinted nanoadsorbents did, and they adsorbed much more of the template than other antibiotics, suggesting that the SMIPs show excellent selective recognition. Reusable SMIPs were shown to be a potentially efficient nanoadsorbent for the selective and fast removal of antibiotic residues from aqueous environments.

Surface imprinted core‐shell nanorod with ultrathin water‐compatible polymer brushes for specific recognition and adsorption of sulfamethazine in water medium

ABSTRACTA surface imprinted core‐shell nanorod with water‐compatible property was first prepared, using a two‐step “living” polymerization technique, with magnetic attapulgite (MATP) as core, and it was applicable in the enhanced selective removal of sulfamethazine residue from pure water environments. MATP was synthesized by an impregnation and pyrolysis method, and polymerable group was subsequently attached onto the surface. The imprinted polymer nanoshell (13 nm) with the “living” fragments was formed via a reverse atom transfer radical precipitation polymerization, avoiding the tedious graft of initiator and providing the easy‐accessible imprinted sites. Ultrathin hydrophilic polymer brushes (2.0 nm) were surface‐grafted to improve their water‐compatibility. The nanoadsorbent exhibited good thermal stability, magnetism, and hydrophilicity through characterization. The nanoadsorbent showed large adsorption capacity toward sulfamethazine from water, which increased with the increase of contact temperature. Langmuir isotherm fitted the equilibrium data better, and the kinetic data (within 45 min) were well‐analyzed by the pseudo‐second‐order kinetic model. Also, the specific adsorption property of the nanoadsorbent was greatly improved through the surface‐grafting, which exhibited excellent selectivity to sulfamethazine compared with other reference antibiotics. Efficient magnetic separation and good reuse of the nanoadsorbent provided the potential possibility for selective recognition and fast removal of antibiotic pollutions from water environments. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 40854.

Efficient one-pot synthesis of uniform, surface-functionalized, and “living” polymer microspheres by reverse atom transfer radical precipitation polymerization

A facile, general, and efficient one-pot approach to obtain uniform, highly cross-linked, surface-functionalized, and “living” polymer microspheres by reverse atom transfer radical precipitation polymerization (RATRPP) is described for the first time, which is easily realized by introducing reverse atom transfer radical polymerization (reverse ATRP) mechanism into precipitation polymerization system. The polymerization parameters including stirring rate, polymerization temperature, monomer loading, initiator concentration, and polymerization scale and time showed considerable influence on the yields and morphologies of the polymer microspheres, which makes it convenient to tailor the particle sizes by tuning polymerization conditions. The general applicability of RATRPP was verified by preparing some uniform functional copolymer microspheres with incorporated 4-vinylpyridine, glycidyl methacrylate, and 2-hydroxyethyl methacrylate. Moreover, the resulting polymer microspheres proved to be “living” by their direct grafting of hydrophilic polymer brushes via surface-initiated ATRP. Furthermore, a mixed particle growth mechanism is proposed for RATRPP (i.e., a combined “grafting from” and “grafting to” mechanism works prior to the consumption of the conventional initiator and a “grafting from” mechanism is dominant afterwards), which is quite different from the “grafting to” particle growth mechanism in the traditional precipitation polymerization and “grafting from” mechanism in the normal ATRPP.

Magnetic and hydrophilic imprinted particles via ATRP at room temperature for selective separation of sulfamethazine

In this work, a facile route to prepare hydrophilic molecularly imprinted particles with magnetic susceptibility (MMIPs) was first reported via atom transfer radical precipitation polymerization (ATRPP) in a methanol/water solvent at low temperature (298 K), which can be considered as an environment-friendly system. During the process, 2-hydroxyethyl methacrylate and N, N-methylenebisacrylamide monomers were added to improve the hydrophilicity of the polymers. The obtained materials were characterized in detail by X-ray diffraction, transform infrared spectroscopy, thermogravimetric analysis, vibrating sample magnetometer, scanning electron microscopy and transmission electron microscopy, and then used for the selective separation of sulfamethazine (SMZ) from aqueous medium. The images showed Fe3O4 nanoparticles that were successfully embedded into the polymer particles with the size ranging from 450 to 650 nm, which exhibited great superparamagnetic susceptivity and high thermal stability. Batch adsorption experiments were performed to determine specific adsorption equilibrium, kinetics, and selective recognition and separation. The effect of the ratio of the double monomers used in the adsorption property was also studied. The equilibrium data of MMIPs toward SMZ was well fitted by the Langmuir isotherm model, and the maximum adsorption capacity estimated was 66.67 μmol g−1. The adsorption kinetics rapidly achieved equilibrium within 1.0 h and was well described by the pseudo-second-order model. The MMIPs synthesized showed outstanding affinity and selectivity toward SMZ over structurally analogous antibiotics and easily achieved magnetic separation under an external magnetic field. In addition, the adsorption performance of the resulting MMIPs was no obviously decreased at least six repeated cycles.

Azobenzene-Containing Molecularly Imprinted Polymer Microspheres with Photo- and Thermoresponsive Template Binding Properties in Pure Aqueous Media by Atom Transfer Radical Polymerization

A facile, general, and highly efficient approach to obtain azobenzene (azo)-containing molecularly imprinted polymer (MIP) microspheres with both photo- and thermoresponsive template binding properties in pure aqueous media is described for the first time, which involves the first synthesis of "living" azo-containing MIP microspheres with surface-immobilized alkyl halide groups via atom transfer radical precipitation polymerization (ATRPP) and their subsequent modification via surface-initiated atom transfer radical polymerization (ATRP) of N-isopropylacrylamide (NIPAAm). The successful grafting of poly(NIPAAm) (PNIPAAm) brushes onto the obtained MIP microspheres was confirmed by FT-IR, SEM, water dispersion stability and static contact angle studies, and template binding experiments. The introduction of PNIPAAm brushes onto the azo-containing MIP microspheres significantly improved their surface hydrophilicity and imparted thermoresponsive properties to them, leading to their pure water-compatible and thermoresponsive template binding properties. In addition, the binding affinity of the imprinted sites in the grafted azo-containing MIP microspheres was found to be photoresponsive toward the template in pure water, and this photoregulation process proved to be highly repeatable under photoswitching conditions.

Ambient temperature synthesis of narrow or monodisperse, highly cross-linked, and “living” polymer microspheres by atom transfer radical precipitation polymerization

A facile ambient temperature atom transfer radical precipitation polymerization (ATRPP) approach is developed for the efficient one-pot synthesis of narrow or monodisperse, highly cross-linked, and “living” polymer microspheres under mild reaction conditions. The simple introduction of an atom transfer radical polymerization (ATRP) mechanism into a precipitation polymerization system, together with the rational use of polar alcoholic solvents, allows the direct ambient temperature preparation of uniform “living” polymer microspheres with their number-average diameters ranging from 0.36–1.95 μm and their particle size distributions being typically less than 1.01. The polymerization parameters (including the monomer loading, polymerization time, and kind of alcoholic solvent) proved to have a pronounced influence on the yields and morphologies of the polymer microspheres, which makes it very convenient to tailor the particle sizes by tuning the polymerization conditions. The general applicability of ambient temperature ATRPP was demonstrated by its successful application in a range of alcoholic solvents as well as its versatility in the synthesis of a series of uniform copolymer microspheres of different monovinyl functional monomers (4-vinylpyridine, glycidyl methacrylate, methyl methacrylate, and 2-hydroxyethyl methacrylate) with ethylene glycol dimethacrylate. In addition, the “livingness” of the resulting polymer microspheres was confirmed by their direct grafting of hydrophilic polymer brushes via surface-initiated ambient temperature ATRP, leading to advanced functional polymer microspheres with significantly improved surface hydrophilicity.

Narrow or Monodisperse, Highly Cross-Linked, and “Living” Polymer Microspheres by Atom Transfer Radical Precipitation Polymerization

A facile, general, and efficient one-pot approach to obtaining narrow or monodisperse, highly cross-linked, surface-functionalized, and “living” polymer microspheres with uniformly cross-linked structures by atom transfer radical precipitation polymerization (ATRPP) is described for the first time. The simple introduction of atom transfer radical polymerization (ATRP) mechanism into precipitation polymerization system allows the direct generation of uniformly cross-linked “living” polymer microspheres with their number-average diameters ranging from 0.73 to 3.25 μm and their polydispersity indices being typically lower than 1.01. The polymerization parameters (including stirring rate, monomer loading, initiator and catalyst concentrations, molar ratio of cross-linker to monovinyl functional comonomer, and polymerization scale and time) have proven to show significant influence on the morphologies of the resulting polymer microspheres, which makes it very convenient to control the particle sizes by easily tuning the reaction conditions. The general applicability of ATRPP was demonstrated by synthesizing a series of uniform functional copolymer microspheres with different incorporated functional comonomers (i.e, 4-vinylpyridine, acrylamide, and 2-hydroxyethyl methacrylate). Moreover, the “livingness” of the resulting polymer microspheres was confirmed by their direct grafting of hydrophilic polymer brushes via surface-initiated ATRP under mild reaction conditions. Furthermore, a “grafting from” particle growth mechanism is proposed for ATRPP, which is considerably different from the “grafting to” particle growth mechanism in the traditional precipitation polymerization.

Preparation of molecularly imprinted polymer microspheres via atom transfer radical precipitation polymerization

AbstractThe first combined use of atom transfer radical polymerization (ATRP) and precipitation polymerization in the molecular imprinting field is described. The utilized polymerization technique, namely atom transfer radical precipitation polymerization (ATRPP), provides MIP microspheres with obvious molecular imprinting effects towards the template, fast template binding kinetics and an appreciable selectivity over structurally related compounds. The living chain propagation mechanism in ATRPP results in MIP spherical particles with diameters (number‐average diameter Dn ≈ 3 μm) much larger than those prepared via traditional radical precipitation polymerization (TRPP). In addition, the MIP microspheres prepared via ATRPP have also proven to show significantly higher high‐affinity binding site densities on their surfaces than the MIP generated via TRPP, while the binding association constants Ka and apparent maximum numbers Nmax of the high‐affinity sites as well as the specific template bindings are almost the same in the two cases. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 3257–3270, 2009