High‐molecular‐weight polyacrylonitrile by atom transfer radical polymerization

A single‐pot atom transfer radical polymerization was used for the first time to successfully synthesize polyacrylonitrile with a molecular weight higher than 80,000 and a narrow polydispersity as low as 1.18. This was achieved with CuBr/isophthalic acid as the catalyst, 2‐bromopropionitrile as the initiator, and N,N‐dimethylformamide as the solvent. The effects of the solvent on the polymerization of acrylonitrile were also investigated. The induction period was shorter in N,N‐dimethylformamide than in propylene carbonate and toluene, and the rate of the polymerization in N,N‐dimethylformamide was fastest. The molecular weight of polyacrylonitrile agreed reasonably well with the theoretical molecular weight in N,N‐dimethylformamide. When chlorine was used in either the initiator or the catalyst, the rate of polymerization showed a trend of decreasing, and the molecular weight deviated from the theoretical predication significantly. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 3372–3376, 2006     

Atom transfer radical polymerizations of methyl methacrylate and styrene with an iniferter reagent as the initiator

Three novel iniferter reagents were synthesized and used as initiators for the polymerizations of methyl methacrylate (MMA) and styrene (St) in the presence of copper(I) bromide and N,N,N′,N″,N″‐pentamethyldiethylenetriamine at 90 and 115°C, respectively. All the polymerizations were well controlled, with a linear increase in the number‐average molecular weights during increased monomer conversions and relatively narrow molecular weight distributions (weight‐average molecular weight/number‐average molecular weight ≤ 1.36) throughout the polymerization processes. The polymerization rate of MMA was faster in bulk than that in solution and was influenced by the different polarities of the solvents. A slight change in the chemical structures of the initiators had no obvious effect on the polymerization rates of MMA and St. The initiator efficiency toward MMA was lower than that toward St. The results of ¹H‐NMR, matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrum analysis, and chain‐extension experiments demonstrated that well‐defined poly(methyl methacrylate) and polystyrene bearing photolabile groups could be obtained via atom transfer radical polymerization (ATRP) with three iniferter reagents as initiators. The polymerization mechanism for this novel initiation system was a common ATRP process. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Synthesis of crosslinked polyacrylonitrile via atom transfer radical polymerization with activators regenerated by electron transfer and use of the resin in mercury removal after modification

Crosslinked polyacrylonitrile (PAN) was synthesized with divinylbenzene as the crosslinker with an iron(III)‐mediated atom transfer radical polymerization method with activators regenerated by electron transfer. The polymerization exhibited first‐order kinetics with respect to the polymerization time. Hydroxylamine hydrochloride (NH₂OH·HCl) was used to modify the cyano groups of the crosslinked PAN to obtain amidoxime (AO) groups. The AO‐crosslinked PAN was used to remove Hg(II). The optimum pH, adsorption kinetics, and adsorption isotherms were investigated. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Atom transfer radical polymerization of lauryl methacrylate

The atom transfer radical polymerization (ATRP) of lauryl methacrylate (LMA) with an ethyl 2‐bromobutyrate/CuCl/N,N,N′,N″,N″‐pentamethyldiethylenetriamine initiation system was successfully carried out in toluene, and poly(lauryl methacrylate) with a low polydispersity (1.2 < weight‐average molecular weight/number‐average molecular weight < 1.5) was obtained. Plots of ln ([M])₀/([M]) versus time and plots of the molecular weight versus conversion showed a linear dependence, indicating a constant number of propagating species throughout the polymerization. The rate of polymerization was 0.56‐order with respect to the concentration of the initiator and 1.30‐order with respect to the concentration of the Cu(I) catalyst. In addition, the effect of the solvent on the polymerization was investigated, and the thermodynamic data and activation parameters for the solution ATRP of LMA were reported. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 1117–1125, 2003     

Preparation and characterization of proton‐conducting crosslinked diblock copolymer membranes

The synthesis and properties of crosslinked diblock copolymers for use as proton‐conducting membranes are presented. A polystyrene‐b‐poly(hydroxyl ethyl methacrylate) diblock copolymer at 56 : 44 wt % was sequentially synthesized via atom transfer radical polymerization. The poly(hydroxyl ethyl methacrylate) (PHEMA) block was thermally crosslinked by sulfosuccinic acid (SA) via the esterification reaction between  OH of PHEMA and  COOH of SA. Proton nuclear magnetic resonance and Fourier transfer infrared spectra revealed the successful synthesis of the diblock copolymer and the crosslinking reaction under the thermal condition of 120°C for 1 h. The ion‐exchange capacity continuously increased from 0.25 to 0.98 mequiv/g with increasing SA concentration because of the increasing number of charged groups in the membrane. However, the water uptake increased up to an SA concentration of 7.6 wt %, above which it decreased monotonically (maximum water uptake ∼ 27.6%). The membrane also exhibited a maximum proton conductivity of 0.045 S/cm at an SA concentration of 15.2 wt %. The maximum behavior of the water uptake and proton conductivity with respect to the SA concentration was considered to be due to a competitive effect between the increase of ionic sites and the crosslinking reaction according to the SA concentration. All the membranes were thermally quite stable at least up to 250°C, presumably because of the block‐copolymer‐based, crosslinked structure of the membranes. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2008     

Preparation and characterization of antifouling poly(vinylidene fluoride) blended membranes

Poly(vinylidene fluoride) (PVDF) membranes have been widely used in microfiltration and ultrafiltration because of their excellent chemical resistance and thermal properties. However, PVDF membranes have exhibited severe membrane fouling because of their hydrophobic properties. In this study, we investigated the antifouling properties of PVDF blended membranes. Antifouling PVDF blended membranes were prepared with a PVDF‐g‐poly(ethylene glycol) methyl ether methacrylate (POEM) graft copolymer. The PVDF‐g‐POEM graft copolymer was synthesized by the atom transfer radical polymerization (ATRP) method. The chemical structure and properties of the synthesized PVDF‐g‐POEM graft copolymer were determined by NMR, Fourier transform infrared spectroscopy, and gel permeation chromatography. To investigate the antifouling properties of the membranes, we prepared microfiltration membranes by using the phase‐inversion method, which uses various PVDF/PVDF‐g‐POEM concentrations in dope solutions. The pure water permeabilities were obtained at various pressures. The PVDF/PVDF‐g‐POEM blended membranes exhibited no irreversible fouling in the dead‐end filtration of foulants, including bovine serum albumin, sodium alginate, and Escherichia coli broth. However, the hydrophobic PVDF membrane exhibited severe fouling in comparison with the PVDF/PVDF‐g‐POEM blended membranes. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Synthesis of polyacrylonitrile via reverse atom transfer radical polymerization initiated by 1,1,2,2‐tetraphenyl‐1,2‐ethanediol/FeCl3/triphenylphosphine

FeCl₃ coordinated by triphenylphosphine was first used as the catalyst in the 1,1,2,2‐tetraphenyl‐1,2‐ethanediol‐initiated reverse atom transfer radical polymerization of acrylonitrile. A FeCl₃/triphenylphosphine ratio of 0.5 not only gave the best control of the molecular weight and its distribution but also provided a rather rapid reaction rate. The rate of polymerization increased with increasing polymerization temperature, and the apparent activation energy was calculated to be 62.4 kJ/mol. When FeCl₃ was replaced with CuCl₂, the reverse atom transfer radical polymerization of acrylonitrile did not show prominent living characteristics. To demonstrate the active nature of the polymer chain end, the polymers were used as macroinitiators to advance the chain‐extension polymerization in the presence of a CuCl/2,2′‐bipyridine catalyst system via a conventional atom transfer radical polymerization process. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 4041–4045, 2007     

Atom transfer radical polymerization of styrene using a copper catalyst with a pseudohalogen anion

Atom transfer radical polymerization has been a very useful method in the recent advances in controlled radical polymerization. It needs an activated alkyl halide as an initiator and a copper halide as a catalyst. This investigation reports the successful application of copper thiocyanate, a catalyst with a pseudohalide anion, in the presence of different ligands such as N,N,N=,N″,N?,N?‐hexamethyltriethylenetetramine (HMTETA), pentyl‐2‐pyridylmethaneimine, and substituted bipyridine in the atom transfer radical polymerization of styrene. Among the three ligands used, HMTETA was found to be very efficient. The polymers were characterized with ¹³C‐NMR, matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry, and gel permeation chromatography analysis. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 1418–1426, 2005     

Effects of the solvent polarity on the atom transfer radical polymerization of methyl methacrylate initiated by 4‐(chloromethyl)phenyltrimethoxysilane

The controllability of the atom transfer radical polymerization of methyl methacrylate in the polar solvent N,N‐dimethylformamide and the nonpolar solvent xylene with 4‐(chloromethyl)phenyltrimethoxysilane as an initiator and with CuCl/2,2′‐bipyridine and CuCl/4,4′‐di(5‐nonyl)‐2,2′‐bipyridine as catalyst systems was studied. Gel permeation chromatography analysis established that in the nonpolar solvent xylene, much better control of the molecular weight and polydispersity of poly(methyl methacrylate) was achieved with the CuCl/4,4′‐di(5‐nonyl)‐2,2′‐bipyridine catalyst system than with the CuCl/2,2′‐bipyridine as catalyst system. In the polar solvent N,N‐dimethylformamide, unlike in xylene, the polymerization was more controllable with the CuCl/2,2′‐bipyridine catalyst system than with the CuCl/4,4′‐di(5‐nonyl)‐2,2′‐bipyridine catalyst system. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 2751–2754, 2007     

Atom transfer radical polymerization of methyl methacrylate initiated with a macroinitiator of poly(vinyl acetate)

Well‐defined poly(vinyl acetate‐b‐methyl methacrylate) block copolymers were successfully synthesized by the atom transfer radical polymerization (ATRP) of methyl methacrylate (MMA) in p‐xylene with CuBr as a catalyst, 2,2′‐bipyridine as a ligand, and trichloromethyl‐end‐grouped poly(vinyl acetate) (PVAc–CCl₃) as a macroinitiator that was prepared via the telomerization of vinyl acetate with chloroform as a telogen. The block copolymers were characterized with gel permeation chromatography, Fourier transform infrared, and ¹H‐NMR. The effects of the solvent and temperature on ATRP of MMA were studied. The control over a large range of molecular weights was investigated with a high [MMA]/[PVAc–CCl₃] ratio for potential industry applications. In addition, the mechanism of the polymerization was discussed. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 1089–1094, 2006     

Living/controlled radical autopolymerization of styrene in the presence of CuCl2 and 2,2′‐bipyridine

The bulk autopolymerization of styrene (St) was successfully conducted in the presence of CuCl₂ and 2,2′‐bipyridine (bpy) at 110 and 130°C. We found that this polymerization was a living/controlled radical polymerization at a [St]₀/[CuCl₂]₀/[bpy]₀ ratio of 54:1:2.5. The resulting number‐average molecular weights linearly increased with conversion, and the polydispersity indices were very narrow (<1.5). The polymerization rate increased with temperature. Increasing the ratios (i.e., 129:1:2.5, 259:1:2.5, and 386:1:2.5) led to a decrease in the ability to control the autopolymerization of St, even uncontrolled polymerization (i.e., 643:1:2.5). The analysis of end groups by ¹H‐NMR indicated that the spontaneous generation of radicals from St were generated by a Mayo‐type process, and this living/controlled radical polymerization might have underwent a reverse atom‐transfer radical polymerization process. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 1532–1538, 2003     

N-(n-Alkyl)-2-pyridinemethanimine mediated atom transfer radical polymerization of lauryl methacrylate: Effect of length of alkyl group

The article describes the polymerization of lauryl methacrylate (LMA) using Cu(I)Br as catalyst for atom transfer radical polymerization in conjunction with N-(n-propyl) [PPMI]/(n-hexyl) [HPMI]/(n-octyl) [OPMI]-2-pyridinemethanimine as complex ligands. The polymerization of LMA was investigated in bulk and solution (toluene as solvent) using Cu(I)Br as catalyst, N-(n-alkyl)-2-pyridinemethanimine as ligands and ethyl-2-bromo isobutyrate (EBiB) as initiator. The ratio of LMA : CuBr : Ligand : EBiB was kept constant in all the polymerizations. In bulk polymerization, the solubility of the catalyst complex increased with increasing the length of alkyl chain on the ligand from propyl to octyl and also gave polymers with narrow molecular weight distribution. The PDI was further narrowed by using OPMI as ligand and toluene was used as solvent. The kinetics of polymerization was also analyzed and it clearly shows that % conversion increased with time. Increase in molecular weight with % conversion without affecting PDI clearly show that the system is living and living nature can be controlled by increasing the length of alkyl group. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

原子转移自由基乳液聚合研究进展

原子转移自由基聚合(ATRP)作为一种可控/活性聚合方法,可对聚合物结构进行精确控制;乳液聚合以水作为分散介质,具有经济、环保等特点。因此,乳液ATRP结合了两者的优点,具有工业化生产的潜力。首先分析了影响乳液ATRP的各种因素,然后综述了正向ATRP、RATRP(反向ATRP)、SR&NI ATRP(正向/反向同时进行的ATRP)和AGET ATRP(电子转移活化剂ATRP)等机制及研究进展,最后对乳液ATRP的发展方向进行了展望。     

Preparation and characterization of polyaniline N‐grafted with poly(ethyl acrylate) synthesized via atom transfer radical polymerization

Polyaniline (PANI) N‐grafted with poly(ethyl acrylate) (PEA) was synthesized by the grafting of bromo‐terminated poly (ethyl acrylate) (PEA‐Br) onto the leucoemeraldine form of PANI. PEA‐Br was synthesized by the atom transfer radical polymerization of ethyl acrylate in the presence of methyl‐2‐bromopropionate and copper(I) chloride/bipyridine as the initiator and catalyst systems, respectively. The leucoemeraldine form of PANI was deprotonated by butyl lithium and then reacted with PEA‐Br to prepare PEA‐g‐PANI graft copolymers containing different amounts of PEA via an N‐grafting reaction. The graft copolymers were characterized by Fourier transform infrared spectroscopy, elemental analysis, and thermogravimetric analysis. Solubility testing showed that the solubility of PANI in chloroform was increased by the grafting of PEA onto PANI. The morphology of the PEA‐g‐PANI graft copolymer films was observed by scanning electron microscopy to be homogeneous. The electrical conductivity of the graft copolymers was measured by the four‐probe method. The results show that the conductivity of the PANI decreased significantly with increasing grafting density of PEA onto the PANI backbone up to 7 wt % and then remained almost constant with further increases in the grafting percentage of PEA. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Preparation of SBS/poly(styrene–methyl methacrylate) thermoplastic interpenetrating polymer network

SBS as polymer I, poly(styrene–methyl methacrylate) polymerized by atom transfer radical polymerization as polymer II, and a thermoplastic interpenetrating polymer network of SBS/poly(styrene–methyl methacrylate) were prepared by the sequential method. The effects of the polymerization temperature, the composition of the catalyst, the ratio of the monomers studied, and the kinetics at 90°C were also investigated. It was shown that when polymerization was initiated by a BPO/CuCl/bpy (BPO:CuCl:bpy = 1:1:3) system at 90°C, the mass averaged molecular weight of the poly(styrene–methyl methacrylate) increased with monomer conversion, and the polydispersities were kept very low. Fourier transform infrared spectroscopy and gel permeation chromatogram showed that poly(styrene–methyl methacrylate) with low polydispersities had been synthesized. Thus, a thermoplastic interpenetrating polymer network comprised of both narrow molecular‐weight‐distribution components was successfully prepared. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 2007–2011, 2003     

Dynamic Monte Carlo Simulation of Atom‐Transfer Radical Polymerization

Summary: A dynamic Monte Carlo model was developed to simulate atom‐transfer radical polymerization (ATRP). The algorithm used to describe the polymerization includes activation, deactivation, propagation, chain transfer, and termination by combination and disproportionation reactions. Model probabilities are calculated from polymerization kinetic parameters and reactor conditions. The model was used to predict monomer conversion, average molecular weight, polydispersity and the complete molecular weight distribution at any polymerization time or monomer conversion. The model was validated with experimental results for styrene polymerization and compared with simulation results from a mathematical model that uses population balances and the method of moments. The simulations agree well with experimental and theoretical results reported in the literature. We also investigated the control volume size and number of iterations to reduce computation time while keeping an acceptable noise level in the Monte Carlo results.

Comparison of the chain length distribution of polystyrene made with ATRP and conventional free radical (CFR) polymerization at 50% conversion. The initiator to monomer ratios are 1:100 (ATRP left peak), 1:500 (ATRP right peak), and 1:1000 (CFR).     

Atom transfer radical polymerization of styrene with 2‐(1‐bromoethyl)‐anthraquinone as an initiator

2‐(1‐Bromoethyl)‐anthraquinone (BEAQ) was successfully used as an initiator in the atom transfer radical polymerization of styrene with CuBr/N,N,N′,N′,N″‐pentamethyldiethylenetriamine as the catalyst at 110°C. The polymerizations were well controlled with a linear increase in the molecular weights (M_n's) of the polymers with monomer conversion and relatively low polydispersities (1.1 < weight‐average molecular weight (M_w)/M_n < 1.5) throughout the poly merizations. The resultant polystyrene thus possessed one chromophore moiety (2‐ethyl‐anthraquinone) at the α end and one bromine atom at the ω end, both from the initiator BEAQ. The intensity of UV absorptions of the resultant polymers decreased with increasing molecular weights of the polymers. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 2081–2085, 2006     

Atom transfer radical bulk polymerization of methyl methacrylate under microwave irradiation

Microwave irradiation (MI) was applied to the atom transfer radical bulk polymerization of methyl methacrylate. The influence of the amount of the refluxing solvent used for controlling the polymerization temperature, irradiation power, irradiation time, and initiator concentration on the conversion, molecular weight, and molecular weight distribution of the polymers was studied with a benzyl chloride/cuprous chloride/2,2′‐bipyridyl initiation system and compared with the corresponding conventional heating (CH) process. In comparison with CH, the results can be summarized as follows. The polymerization rate for reaching 70% conversion increased 2.6–5.1 times under an irradiation power of 270–630 W. The apparent increasing rate constant was much larger than that with CH and increased with the irradiation power. MI produced a higher polymerization rate and conversion even if the concentration of the initiation system was very low (initial monomer concentration/initial initiator concentration = 200:0.33 mol/mol) and the polydispersity index (DI) was narrower; however, CH yielded almost no polymers. MI promoted the activities of the catalyst and monomer, and its initiation efficiency was higher than that with CH and increased with the irradiation power. MI obviously played an important role in promoting the polymerization rate of atom transfer radical polymerization (ATRP). MI reduced the concentration of the initiation system and perhaps made ATRP controlled (cf. uncontrolled ATRP with CH); at the same time, it made the DI values of the polymers narrower. In comparison with the initiation efficiencies found with benzyl bromide and 2,2′‐azobisisobutyronitrile used as initiators, the initiation efficiency with p‐toluene sulfonyl chloride used as an initiator was higher; moreover, DI was much narrower (1.17), and the polymerization rate was greater. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 1787–1793, 2003     

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

Silica (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 (D_n) = 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/D_n ≈ 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     

Atom transfer radical polymerization of n‐butyl methacrylate in an aqueous dispersed system

Atom transfer radical polymerization of n‐butyl methacrylate (BMA) was conducted in an aqueous dispersed system with different kinds of copper complexes. The partitioning behavior of the copper complexes, including CuCl/4,4′‐di(5‐nonyl)‐2,2′‐bipydine (dNbpy), CuCl₂/dNbpy, CuCl/2,2′‐bipydine (bpy), CuCl₂/bpy, CuCl/bis(N,N′‐dimethylaminoethyl)ether (bde), and CuCl₂/bde between the monomer (BMA), and water was studied in detail with ultraviolet‐visible spectroscopy. The results show that with a less hydrophobic ligand, such as bpy or bde, most of the Cu(I) or the Cu(II) complexes migrated from the BMA phase to the aqueous phase, the atom transfer equilibrium was destroyed, and the polymerization was nearly not controlled; it converted to classical emulsion polymerization. As to the very hydrophobic ligand dNbpy, although the partitioning study of the copper complexes indicated that not all the copper species were restricted to the organic phase, the linear correlation between the molecular weight and the monomer conversion and the narrow polydispersities confirmed that the polymerization was still quite well controlled. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 3175–3179, 2003