Surface initiated‐atom transfer radical polymerization of a sugar methacrylate on gold nanoparticles

For development of surface‐functionalized gold nanoparticles (GNPs) as cellular probes, we report herein the synthesis of glycoconjugates of GNPs with cyclic sugar methacrylate, 2‐lactobionamidoethyl methacrylate (LAMA). The strategy involves the attachment of an initiator on the nanoparticle surface followed by surface initiated‐atom transfer radical polymerization (SI‐ATRP) of LAMA. SI‐ATRP of LAMA was achieved by reacting a mixture of copper (I) bromide (CuBr), 2,2′‐bipyridine (bpy) and initiator‐bound GNPs in methanol at 20 °C for 12 h. The resultant GNP glycoconjugates were characterized using Fourier‐transform infrared (FT‐IR) spectroscopy, X‐ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM). The FT‐IR spectra of GNP glycoconjugates show IR peaks characteristic of LAMA demonstrating the formation of a LAMA layer on the GNPs' surface. The XPS spectrum of glycoconjugates shows signals due to the presence of carbon (C1s, 288 eV) and oxygen (O1s, 536 eV) along with gold (Au 4f, 100 eV; Au 4p, 743 eV). The increase in diameter of GNPs from 13 to 25 nm measured by SEM further confirms the presence of a LAMA layer on the surface of the GNPs. Considering the biological importance of glycoconjugates, such as cell recognition, cell adhesion and cell growth regulation, the method described herein would be beneficial in many areas such as pathogen detection and biosensors. Copyright © 2008 John Wiley & Sons, Ltd.     

Kinetic studies of surface‐initiated atom transfer radical polymerization in the synthesis of magnetic fluids

We present results from kinetic studies on the surface‐initiated atom transfer radical polymerization in the preparation of polymer brush‐coated magnetic particles from a heterogeneous system. It is shown that a controlled reaction behavior and a reproducible surface functionalization with end‐tethered polymers are achieved, although the reaction advances gradually from a biphasic solid–liquid mixture to a stable colloidal dispersion of the nanoobjects. Although the initiator‐functional magnetite nanoparticles initially form a precipitate, the formation of a polymer layer on the particle surface in the course of the reaction contributes to a sterical stabilization in dispersion. We thoroughly investigated the development of the initial heterogeneous system with time and in various concentration regimes by simultaneously monitoring the monomer conversion, molar mass, the hydrodynamic diameter of the nanoobjects, and the magnetite content of the dispersions at different reaction times. The results indicate first‐order chain growth kinetics with respect to the monomer and narrow molar mass distributions, demonstrating good control on the particle architecture. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2009     

Tailor‐made hybrid nanostructure of poly(ethyl acrylate)/clay by surface‐initiated atom transfer radical polymerization

Hybrid nanoarchitecture of tailor‐made Poly(ethyl acrylate)/clay was prepared by surface‐initiated atom transfer radical polymerization (SI‐ATRP), by tethering ATRP initiator on active hydroxyl group, present in surface as well as in the organic modifier of the clay used. Extensive exfoliation was facilitated by using these initiator modified clay platelets. Poly(ethyl acrylate) chains with controlled polymerization and narrow polydispersities were forced to be grown from within the clay gallery (intergallery) as well as from the outer surface (extragallery) of the clay platelets. The polymer chains attached onto clay surfaces might have the potential to provide the composites with enhanced compatibility in blends with common polymers. Attachment of the initiator on clay platelets was confirmed by Fourier transform infrared spectroscopy (FTIR), X‐ray photoelectron spectroscopy (XPS), elemental analysis, Wide‐angle X‐ray diffraction (WAXD), and microscopic analysis. Finally, end group analysis (by Matrix‐Assisted Laser Desorption Ionization Mass Spectrometry, and chain extension experiment) of the cleaved polymer and morphological study (by WAXD, Transmission Electron Microscopy), performed on the polymer grafted clays examined the effect of grafting on the efficiency of polymerization and the degree of dispersion of clay tactoids in polymer. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 5014–5027, 2008     

Reverse atom transfer radical polymerization of methyl methacrylate initiated by p‐chlorobenzenediazonium tetrafluoroborate

The controlled polymerization of methyl methacrylate (MMA) in bulk was initiated with p‐chlorobenzenediazonium tetrafluoroborate ( 1 ) and Cu(II) or Cu(I)/Cu(II)/N,N,N′,N″,N″‐pentamethyldietylene triamine (PMDETA) complex system at various temperatures (20, 60, and 90 °C). The proposed polymerization mechanism is based on the Meerwein‐type arylation reaction followed by a reverse atom transfer radical polymerization. In this mechanism, aryl radicals formed by the reaction with 1 and Cu(I) and/or PMDETA initiated the polymerization of MMA. The polymerization is controlled up to a molecular weight of 46,000 at 90 °C. Chain extension was carried out to confirm the controlled manner of the polymerization system. In all polymerization systems, the polydispersity index and initiator efficiency ranged from 1.10–1.57 to 0.10–0.21, respectively. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 2019–2025, 2003     

Kinetics of surface‐initiated atom transfer radical polymerization

Although atom transfer radical polymerization (ATRP) is often a controlled/living process, the growth rate of polymer films during surface‐initiated ATRP frequently decreases with time. This article investigates the mechanism behind the termination of film growth. Studies of methyl methacrylate and methyl acrylate polymerization with a Cu/tris[2‐(dimethylamino)ethyl]amine catalyst system show a constant but slow growth rate at low catalyst concentrations and rapid growth followed by early termination at higher catalyst concentrations. For a given polymerization time, there is, therefore, an optimum intermediate catalyst concentration for achieving maximum film thickness. Simulations of polymerization that consider activation, deactivation, and termination show trends similar to those of the experimental data, and the addition of Cu(II) to polymerization solutions results in a more constant rate of film growth by decreasing the concentration of radicals on the surface. Taken together, these studies suggest that at high concentrations of radicals, termination of polymerization by radical recombination limits film growth. Interestingly, stirring of polymerization solutions decreases film thickness in some cases, presumably because chain motion facilitates radical recombination. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 386–394, 2003     

Light‐driven atom transfer radical polymerization on supramolecular complexes of conjugated polymers and single‐walled carbon nanotubes

Previous approaches used to decorate latently reactive conjugated polymer‐coated carbon nanotube complexes have utilized “grafting‐to” strategies. Here, we coat the carbon nanotube surface with a conjugated polymer whose side chains contain the radical initiator, α‐bromoisobutyrate, which enables atom transfer radical polymerization (ATRP) from the polymer–nanotube surface. Using light to generate Cu(I) in situ, ATRP is used to grow narrow dispersity polymer chains from the polymer–nanotube surface. We confirm the successful polymerization of (meth)acrylates from the polymer–nanotube surface using a combination of gel permeation chromatography and infrared spectroscopy. Strikingly, we demonstrate that nanotube optoelectronic properties are preserved after radical‐mediated polymer grafting using Raman spectroscopy and photoluminescence mapping. Overall, this work elucidates a method to grow narrow dispersity polymer chains from the polymer–nanotube surface using light‐driven radical chemistry, with concurrent preservation of nanotube optoelectronic properties. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019, 57, 2015–2020     

Preparation of polymer‐grafted carbon black nanoparticles by surface‐initiated atom transfer radical polymerization

Pristine carbon black was oxidized with nitric acid to produce carboxyl group, and then the carboxyl group was consecutively treated with thionyl chloride and glycol to introduce hydroxyl group. The hydroxyl group on the carbon black surface was reacted with 2‐bromo‐2‐methylpropionyl bromide to anchor atom transfer radical polymerization (ATRP) initiator. The ATRP initiator on carbon black surface was verified by TGA, FTIR, EDS, and elemental analysis. Then, poly (methyl methacrylate) and polystyrene chains were respectively, grown from carbon black surface by surface‐initiated atom transfer radical polymerization (SI‐ATRP) using CuCl/2,2‐dipyridyl (bpy) as the catalyst/ligand combination at 110 °C in anisole. ¹H NMR, TGA, TEM, AFM, DSC, and DLS were used to systemically characterize the polymer‐grafted carbon black nanoparticles. Dispersion experiments showed that the grafted carbon black nanoparticles had good solubilities in organic solvents such as THF, chloroform, dichloromethane, DMF, etc. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 3451–3459, 2007     

Core‐shell structured poly(glycidyl methacrylate)/BaTiO3 nanocomposites prepared by surface‐initiated atom transfer radical polymerization: A novel material for high energy density dielectric storage

Core‐shell structured barium titanate‐poly(glycidyl methacrylate) (BaTiO₃‐PGMA) nanocomposites were prepared by surface‐initiated atom transfer radical polymerization of GMA from the surface of BaTiO₃ nanoparticles. Fourier transform infrared spectroscopy confirmed the grafting of the PGMA shell on the surface of the BaTiO₃ nanoparticles cores. Transmission Electron Microscopy results revealed that BaTiO₃ nanoparticles are covered by thin brushes (～20 nm) of PGMA forming a core‐shell structure and thermogravimetric analysis results showed that the grafted BaTiO₃‐PGMA nanoparticles consist of ～13.7% PGMA by weight. Upon incorporating these grafted nanoparticles into 20 μm‐thick films, the resultant BaTiO₃‐PGMA nanocomposites have shown an improved dielectric constant (ε = 54), a high breakdown field strength (～3 MV/cm) and high‐energy storage density ～21.51 J/cm³. AC conductivity measurements were in good agreement with Jonscher's universal power law and low leakage current behavior was observed before the electrical breakdown field of the films. Improved dielectric and electrical properties of core‐shell structured BaTiO₃‐PGMA nanocomposite were attributed to good nanoparticle dispersion and enhanced interfacial polarization. Furthermore, only the surface grafted BaTiO₃ yielded homogenous films that were mechanically stable. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 719–728     

Facile one‐pot method of initiator fixation for surface‐initiated atom transfer radical polymerization on carbon hard spheres

An efficient and novel one‐pot process is developed to immobilize the atom transfer radical polymerization (ATRP) initiators onto the surface of fully pyrolyzed carbon hard spheres (CHSs) via a radical trapping process from the in situ thermal decomposition of bis(bromomethylbenzoyl)peroxide. The CHSs do not require any additional preparative treatment prior to the initiator immobilization. Styrene and methyl methacrylate are polymerized onto initiator‐immobilized CHSs by surface‐initiated atomic transfer radical polymerization (SI‐ATRP). Samples are characterized using Fourier transform infrared, thermogravimetric analysis, scanning electron microscopy, and transmission electron microscopy. These methods of characterization confirmed that all the CHSs are coated with a uniform layer of grafted polymer. This efficient, one‐pot immobilization of ATRP‐initiators represents an exceptionally simple route for the rapid preparation of various polymer‐coated carbon‐based nanomaterials using SI‐ATRP. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013, 51, 3314–3322     

Novel UV initiator for functionalization of multiwalled carbon nanotubes by atom transfer radical polymerization applied on two different grades of nanotubes

A novel nonoxidative method for preparation of functionalized multiwalled carbon nanotubes (MWCNT) has been developed based on a UV sensitive initiator for atom transfer radical polymerization (ATRP). The method has been investigated with respect to ligands and polymerization time for the preparation of polystyrene functionalized MWCNT. It was found that pentamethyldiethylenetriamine (PMDETA) gave superior results with higher loading in shorter polymerization time. A comparative study of the method applied on two different grades of nonoxidized MWCNT has been performed, illustrating large differences in reactivity and polymer loading, underlining the importance of the choice of MWCNT starting material. In addition to styrene, also poly(ethylene glycol) methacrylate (PEGMA) was shown to polymerize from the surface of the MWCNT. Finally, initial results from composites of polystyrene or polyphenylenesulfide are presented. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2010     

Preparation of poly(styrene‐co‐acrylonitrile)‐grafted multiwalled carbon nanotubes via surface‐initiated atom transfer radical polymerization

The in situ grafting‐from approach via atom transfer radical polymerization was successfully applied to polystyrene, poly(styrene‐co‐acrylonitrile), and polyacrylonitrile grafted onto the convex surfaces of multiwalled carbon nanotubes (MWCNTs) with (2‐hydroxyethyl 2‐bromoisobutyrate) as an initiator. Thermogravimetric analysis showed that effective functionalization was achieved with the grafting approach. The grafted polymers on the MWCNT surface were characterized and confirmed with Fourier transform infrared spectroscopy and nuclear magnetic resonance. Raman and near‐infrared spectroscopy revealed that the grafting of polystyrene, poly(styrene‐co‐acrylonitrile), and polyacrylonitrile slightly affected the side‐wall structures. Field emission scanning electron microscopy showed that the carbon nanotube surface became rough because of the grafting of the polymers. Differential scanning calorimetry results indicated that the polymers grafted onto MWCNTs showed higher glass‐transition temperatures. The polymer‐grafted MWCNTs exhibited relatively good dispersibility in an organic solvent such as tetrahydrofuran. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 460–470, 2007     

Living radical graft polymerization of methyl methacrylate to polyethylene film with typical and reverse atom transfer radical polymerization

Nickel‐mediated atom transfer radical polymerization (ATRP) and iron‐mediated reverse ATRP were applied to the living radical graft polymerization of methyl methacrylate onto solid high‐density polyethylene (HDPE) films modified with 2,2,2‐tribromoethanol and benzophenone, respectively. The number‐average molecular weight (M_n) of the free poly(methyl methacrylate) (PMMA) produced simultaneously during grafting grew with the monomer conversion. The weight‐average molecular weight/number‐average molecular weight ratio (M_w/M_n) was small (<1.4), indicating a controlled polymerization. The grafting ratio showed a linear relation with M_n of the free PMMA for both reaction systems. With the same characteristics assumed for both free and graft PMMA, the grafting was controlled, and the increase in grafting ratio was ascribed to the growing chain length of the graft PMMA. In fact, M_n and M_w/M_n of the grafted PMMA chains cleaved from the polyethylene substrate were only slightly larger than those of the free PMMA chains, and this was confirmed in the system of nickel‐mediated ATRP. An appropriate period of UV preirradiation controlled the amount of initiation groups introduced to the HDPE film modified with benzophenone. The grafting ratio increased linearly with the preirradiation time. The graft polymerizations for both reaction systems proceeded in a controlled fashion. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 3350–3359, 2002     

Elucidation of the mechanism of surface‐initiated atom transfer radical polymerization from a diazonium‐based initiator layer

This study elucidates the influence of the atom transfer radical polymerization initiator structure, monolayer versus disordered multilayer, on the growth kinetics and the structural transition of poly(methyl methacrylate) (PMMA) brush layers. The multilayer initiator film, prepared by acylation of the electrografted 2‐phenylethanol layer using 2‐bromoisobutyryl bromide, consists of ～4.6 times more tert‐butyl bromide groups compared to monolayer initiator prepared by self assembly technique. The results demonstrate the formation of precursor complex between Cu^I catalyst and the bromine initiator as a prerequisite step before the onset of polymerization. Furthermore, the PMMA brushes formed by the polymerization from the multilayered initiator layer at 50 °C are 20‐fold thicker compared to the polymerization at 25 °C due to the swelling of the multilayered initiator film. In contrast, the thickness of the PMMA layer on the monolayer initiator is less affected by the polymerization temperature. By varying the initiator density on the surface, the solvent content in the PMMA layer is shown to vary from 15% to 94%, resulting in the transition from concentrated over semidiluted to diluted brushes. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

Atom transfer radical polymerization initiated by N‐bromosuccinimide

N‐Bromosuccinimide (NBS) was used as the initiator in the atom transfer radical polymerizations of styrene (St) and methyl methacrylate (MMA). The NBS/CuBr/bipyridine (bpy) system shows good controllability for both polymerizations and yields polymers with polydispersity indexes ranging from 1.18 to 1.25 for St and 1.14 to 1.41 for MMA, depending on the conditions used. The end‐group analysis of poly(MMA) and polystyrene indicated the polymerization is initiated by the succinimidyl radicals formed from the redox reaction of NBS with CuBr/bpy. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 5811–5816, 2004     

Copper catalyzed atom transfer radical copolymerization of glycidyl methacrylate and 2‐ethylhexyl acrylate

This investigation reports the atom transfer radical copolymerization (ATRcP) of glycidyl methacrylate (GMA) and 2‐ethylhexyl acrylate (EHA). Poly(glycidyl methacrylate) (PGMA) has easily transformable pendant oxirane group and poly(2‐ethylhexyl acrylate) (PEHA) has very low T_g. They are the important components of coating and adhesive materials. Copolymerization of GMA and EHA was carried out in bulk and in toluene at 70 °C at different molar feed ratios using CuCl as catalyst in combination with 2,2′‐bypyridine (bpy) as well as N,N,N′,N″,N″‐pentamethyl diethylenetriamine (PMDETA) as ligand. The molecular weight (M_n) and the polydispersity index (PDI) of the polymers were determined by GPC analysis. The molar composition of the copolymers was determined by ¹H NMR analysis. The reactivity ratios of GMA (r₁) and EHA (r₂) were determined using Finemann‐Ross and Kelen‐Tudos linearization methods and those had been compared with the literature values for conventional free radical copolymerization. The thermal properties of the copolymers were studied by DSC and TGA analysis. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 6526–6533, 2009     

Growth of poly(methyl methacrylate) brushes on silicon surfaces by atom transfer radical polymerization

Poly(methyl methacrylate) (PMMA) brushes are grown by surface‐initiated atom transfer radical polymerization on silicon surfaces at various polymerization temperatures. Kinetic studies show that the layer thickness scales linearly with the degree of polymerization of the polymers under some conditions, indicating a constant graft density of the surface‐attached chains. At high temperatures, the layer growth is a controlled process only for short reaction times, and after a rapid increase, the film growth levels off, and a constant thickness is obtained. At lower reaction temperatures, polymers with a lower polydispersity are obtained, but at the expense of a much slower growth rate. Accordingly, intermediate temperatures yield the highest film thickness on experimentally feasible timescales. The reinitiation of these surface‐grafted PMMA chains at room temperature to either extend the chains or grow a chemically different polyglycidylmethacrylate block demonstrates the presence of active ends and the living nature of the surface‐grafted PMMA chains. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 1758–1769, 2006     

Preparation of polystyrene-grafted titanate nanotubes by in situ atom transfer radical polymerization

This work successfully prepared nanohybrids by in situ atom transfer radical polymerization (ATRP) of styrene from titanate nanotubes (TNTs). Fourier-transform infrared (FT-IR), pronton nuclear magnetic resonance spectroscopy (1H NMR), and thermal gravimetric analysis (TGA) were used to verify the successful graft of polystyrene (PS) chains from TNTs. Transmission electron microscopy (TEM) dis-played that the obtained PS-g-TNTs nanohybrids had a core-shell structure of TNT core and PS shell. The grafted PS ...     

Synthesis of well‐defined hairy polymer microspheres by precipitation polymerization and surface‐initiated atom transfer radical polymerization

A variety of polymer microspheres were successfully synthesized by the surface‐initiated atom transfer radical polymerization (SI‐ATRP) of monomers by using monodisperse polymer microsphere having benzyl halide moiety as a multifunctional polymeric initiator. First, a series of monodisperse polymer microsphere having benzyl chloride with variable monomer ratio (P(St‐DVB‐VBC)) were synthesized by the precipitation polymerization of styrene (St), divinylbenzene (DVB), and 4‐vinylbenzyl chloride (VBC). Next, hairy polymer microspheres were synthesized by the surface‐initiated ATRP of various monomers with P(St‐DVB‐VBC) microsphere as a multifunctional polymeric initiator. The hair length determined by the SEC analysis of free polymer was increased with the increase of M/I. These hairy polymer microspheres were characterized by SEM, FT‐IR, and Cl content measurements. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019 © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019, 57, 1296–1304     

Bulk atom transfer radical polymerization of allyl methacrylate

A detailed investigation of the polymerization of allyl methacrylate, a typical unsymmetrical divinyl compound containing two types of vinyl groups, methacryloyl and allyl, with quite different reactivities, was performed with atom transfer radical polymerization (ATRP). Homopolymerizations were carried out in bulk, with ethyl‐2‐bromoisobutyrate as the initiator and with copper halide (CuX, where X is Cl or Br) with N,N,N′,N″,N″‐pentamethyldiethylenetriamine as the catalyst system. Kinetic studies demonstrated that during the early stages of the polymerization, the ATRP process proceeded in a living manner with a low and constant radical concentration. However, as the reaction continued, the increased diffusion resistance restricted the mobility of the catalyst system and interrupted the equilibrium between the growing radicals and dormant species. The obtained poly(allyl methacrylate)s (PAMAs) were characterized with Fourier transform infrared, ¹H NMR, and size exclusion chromatography techniques. The dependence of both the gel point conversion and molecular characteristics of the PAMA prepolymers on different experimental parameters, such as the initiator concentration, polymerization temperature, and type of halide used as the catalyst, was analyzed. These real gel points were compared with the ones calculated according to Gordon's equation under the tentative assumption of equal reactivity for the two types of vinyl groups. Moreover, the microstructure of the prepolymers was the same as that exhibited by those homopolymers prepared by conventional free‐radical polymerization; the fraction of syndiotactic arrangements increased as the reaction temperature was lowered. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 2395–2406, 2005     

Synthesis of 4-arm methyl methacrylate star polymer by atom transfer radical polymerization

The synthesis of 4-arm methyl methacrylate star polymer had been achieved successfully by atom transfer radical polymerization using CuCl as catalyst, 2, 2′-bipyridyl as ligand and pentaerythritol tetrakis (2-bromoisobutyrate) as the initiator. The star polymer was characterized by ¹H-NMR and GPC, by which the precise 4-arm structure of the PMMA was confirmed. __________ Translated from Journal of Shaanxi Normal University (Natural Science Edition), 2008, 36(2) (in Chinese)