Effect of cobalt(III) 1-nitroso-2-naphtholate on free-radical polymerization to vinyl monomers

It has been shown that, at 70°C, cobalt(III) 1-nitroso-2-naphtholate inhibits the free-radical polymerization of styrene, methyl methacrylate, butyl methacrylate, and butyl acrylate. The induction period linearly increases with complex concentration. The polymerization of styrene (120°C) carried out in the presence of cobalt(III) 1-nitroso-2-naphtholate shows typical features of pseudoliving polymerization, namely, linear ln[M]₀/[M]-time and molecular mass-conversion plots. When the monomers are allowed to stand with a complex (7 × 10^?3 mol/l) and an initiator (5 × 10^?3 mol/l) for 1 day at 20°C, the ESR signal corresponding to the nitroxide radical appears. In the course of polymerization, the signal disappears, indicating the consecutive transformation of the cobalt(III) 1-nitroso-2-naphtholate radical into the macronitroxide adduct. Polystyrene samples isolated at various conversions initiate the secondary polymerization of styrene and its block copolymerization with methyl methacrylate.     

Cobalt complex bearing β‐ketoamine ligand: syntheses,structure, catalytic behavior for styrene and methyl methacrylate polymerization

Cobalt complex based on β‐ketoamine ligand [(Z)‐4‐((2,5‐dimethylphenylamino) (phenyl)methylene)‐3‐methyl‐1‐phenyl‐1H‐pyrazol‐5(4H)‐one] was successfully synthesized. The produced catalyst showed satisfactory activities in the cobalt‐mediated radical polymerization of styrene and methyl methacrylate with the common initiator of AIBN. The resulting polymerizations have the characteristics of living radical polymerization and displayed a nearly linear correlation between the number‐average molecular weight and monomer conversion. Low polydispersity was obtained for all polymerizations, and the polydispersity index decreased with the increase of conversion. These improvements facilitate the implementation of styrene and methacrylate cobalt‐mediated radical polymerization, and open the door to the scale‐up of the process. Copyright © 2014 John Wiley & Sons, Ltd.     

The use of the DPE radical polymerization method for the synthesis of chromophore-labelled polymers and block copolymers

Two analogues of diphenylethene carrying phenanthrene (1-(9-phenanthryl)-1-phenylethene (PPE)) and anthracene (1-(2-anthryl)-1-phenylethene (APE)) units were used in radical polymerization of styrene (St) and methyl methacrylate (MMA) at 80 °C using AIBN as initiator. Because of the nature of the polymerization, the resulting polymers possess the corresponding chromophoric groups. Using the methodology of a DPE system, these labelled polymers were further used for the synthesis of block copolymers. In this way poly(methyl methacrylate)-b-poly(styrene) and poly(methyl methacrylate)-b-poly(acrylonitrile) with molar masses of 60,000-90,000 g/mol were synthesized. Incorporation of the chromophoric groups into both homo- and block copolymers was confirmed by spectral measurements.     

Poly(propylene imine) dendrimers as hydrogen donor in Type II photoinitiated free radical polymerization

Three generations of poly(propylene imine) dendrimers, namely (PPI-16, PPI-32 and PPI-64; 16, 32 and 64 for generations 3, 4 and 5, respectively) were used as hydrogen donors in photoinitiated free radical polymerization of methyl methacrylate by using one of the following photosensitizers; benzophenone and thioxanthone. The effect of generation number of the dendrimer on photoinitiation efficiency and molecular weight of the resulting polymers was investigated. Glass transition temperatures and particle size measurements of the resulting polymers indicated the presence of nearly stretched polymer chains around the dendrimers. The location of hydrogen donating sites was evaluated by photolysis studies in the absence of monomer by using a stable radical namely, 2,2,6,6-tetramethylpiperidine-N-oxyl free radical (TEMPO) and showed that hydrogen abstraction occurs from the inner tertiary amino groups. The TEMPO attached dendrimers were further used in the nitroxide mediated radical polymerization (NMP) of styrene to yield star polymers.     

Thermal stability and high glass transition temperature of 4-chloromethyl styrene polymers bearing carbazolyl moieties

A new styrene derivative monomer, 4-(N-carbazolyl)methyl styrene (CzMS), was synthesized by reacting 4-chloromethyl styrene with carbazole in the presence of sodium hydride. Then, CzMS was homopolymerized and copolymerized with different monomers such as methyl methacrylate (MMA), ethyl methacrylate (EMA), methyl acrylate (MA), ethyl acrylate (EA) and n-butyl acrylate (BA) by free radical polymerization method in N,N-di-methylformamide (DMF) solution at 70 ± 1 °C using azobisisobutyronitrile initiator to give the copolymers I-V in good yields. The structure of all the resulted polymers was characterized and confirmed by FT-IR, ¹H NMR and ¹³C NMR spectroscopic techniques. The average molecular weight and glass transition temperature of polymers were determined using gel permeation chromatograph (GPC) and differential scanning calorimeter (DSC) instruments, respectively. It was found that these polymers with carbazole moieties have high thermal stability and the presence of bulk carbazole groups in polymer side chains leads to an increase in the rigidity and glass transition temperature of polymers.     

Reverse atom transfer radical polymerization of vinyl monomers with Fe[SC(S)NEt2]3 alone as the catalyst

The living radical polymerization of methyl methacrylate and styrene was successfully carried out with diethyl 2,3‐dicyano‐2,3‐diphenylsuccinate (DCDPS)/ferric tri(diethyldithiocarbamate) as a novel reverse atom transfer radical polymerization initiation system in which DCDPS was a hexa‐substituted ethane‐type thermal iniferter, DC was a diethyldithiocarbamate group, and no additional ligands such as nitrogen‐ or phosphine‐based compounds were required. The bulk polymerization of methyl methacrylate was carried out at 95 °C, and that of styrene was carried out at 120 °C. Poly(methyl methacrylate) and polystyrene (PSt) with high molecular weights and quite narrow molecular weight distributions (as low as 1.09 for PSt) were obtained. ¹H NMR spectroscopy revealed the presence of an α‐(carbethoxycyanophenyl)methyl group from the initiator and an ω‐DC group from the catalyst in the obtained polymers. Various chain‐extension reactions under UV light or thermal treatments were successfully conducted to prove the presence and efficient reinitiating of the ω‐DC group. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 3464–3473, 2001     

Controlled radical polymerization of methacrylates of various structures in the presence of the AIBN-FeCl3-N,N-dimethylformamide catalytic system

The controlled radical polymerization of methyl methacrylate, 2-ethoxyethyl methacrylate, and tert-butyl methacrylate conducted via atom-transfer radical polymerization in the presence of the AIBN-FeCl₃· 6H₂O-N,N-dimethylformamide catalytic system is studied. For all the systems under study, the rate of reaction is first order with respect to the monomer concentration. The number-average molecular mass of the polymers linearly increases with conversion, and their polydispersity indexes are below 1.6. The rate of polymerization decreases in the following sequence: 2-ethoxyethyl methacrylate > methyl methacrylate > tert-butyl methacrylate. The presence of ω-terminal chlorine atoms in polymer macromolecules is confirmed by ¹H NMR spectroscopy and through the block copolymerization of methyl methacrylate with a poly(ethoxyethyl methacrylate)-based macroinitiator.     

Use of the NiBr2(PPh3)2/Zn catalytic system for homo- and copolymerization of styrene and methyl methacrylate

The regularities of methyl methacrylate and styrene (co)polymerization in the presence of catalytic systems based on a Ni(II) complex combined with zinc and an aryl halide have been studied. The effects of temperature and catalytic system components on conversion are established. The molecular masses of the polymers linearly increase with monomer conversion, thus suggesting the controlled character of the polymerization. Reactivity ratios are calculated for methyl methacrylate-styrene copolymerization (r _MMA = 0.45, r _styrene = 1.70) in the presence of NiBr₂(PPh₃)₂/Zn/PhI. The rate of copolymerization is shown to decrease with an increase in methyl methacrylate concentration. The scheme of the process is proposed based on an analysis of the experimental and literature data.     

Polymerization of styrene and methyl methacrylate in the presence of 2,2-diethyl-4,5,5-trimethyl-2,5-dihydroimidazol-1-oxyl

The polymerization of styrene and methyl methacrylate in the presence of 2,2-diethyl-4,5,5-trimethyl- 2,5-dihydroimidazol-1-oxyl has been studied. It has been demonstrated that the nitroxyl radical makes it possible to control chain propagation in the polymerization of styrene and to synthesize polymers with relatively low polydispersity coefficients (<1.4). The polymerization of methyl methacrylate in the controlled mode cannot be performed because of the occurrence of a side reaction related to hydrogen atom transfer.     

Polymerization of methyl methacrylate and styrene in the presence of polyimides containing aliphatic moieties in the backbone

The radical homopolymerization of methyl methacrylate and styrene in the presence of polyimide that contains aliphatic moieties and is dissolved in the monomer is studied. The viscosity characteristics, heat resistances, and thermal stabilities of the resulting polymers and their solubilities in organic solvents are examined. It is found that the products of radical polymerization are polyimide-poly(methyl methacrylate) and polyimide-polystyrene copolymers, whose properties differ from those of the respective unmodified polymerization and polycondensation polymers.     

Multifunctional ATRP initiators: Synthesis of four‐arm star homopolymers of methyl methacrylate and graft copolymers of polystyrene and poly(t‐butyl methacrylate)

Tetrakis bromomethyl benzene was used as a tetrafunctional initiator in the synthesis of four‐armed star polymers of methyl methacrylate via atom transfer radical polymerization (ATRP) with a CuBr/2,2 bipyridine catalytic system and benzene as a solvent. Relatively low polydispersities were achieved, and the experimental molecular weights were in agreement with the theoretical ones. A combination of 2,2,6,6‐tetramethyl piperidine‐N‐oxyl‐mediated free‐radical polymerization and ATRP was used to synthesize various graft copolymers with polystyrene backbones and poly(t‐butyl methacrylate) grafts. In this case, the backbone was produced with a 2,2,6,6‐tetramethyl piperidine‐N‐oxyl‐mediated stable free‐radical polymerization process from the copolymerization of styrene and p‐(chloromethyl) styrene. This polychloromethylated polymer was used as an ATRP multifunctional initiator for t‐butyl methacrylate polymerization, giving the desired graft copolymers. © 2001 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 39: 650–655, 2001     

Cobalt and manganese complexes with redox-active ligands in polymerization of acrylonitrile and methyl methacrylate

The influence of bis[4,6-di-tert-butyl-N-(2,6-dimethylphenyl)-o-iminobenzosemiquinonato]cobalt(ii) and 4,6-di-tert-butyl-N-(2,6-diisopropylphenyl)-o-iminobenzosemiquinonato]-[4,6-di-tert-butyl-N-(2,6-diisopropylphenyl)-o-amidophenolate]manganese(iii) on polymerization of methyl methacrylate and acrylonitrile in the presence of azobisisobutyronitrile (as a traditional radical initiator) and alkyl halides (used for initiation of controlled atom transfer radical polymerization process) was studied. The effect of the nature of the activating agents (amines) and the temperature conditions on the overall polymerization rate of the indicated monomers, as well as molecular weight characteristics of the synthesized polymers, were analyzed. The optimal conditions for the synthesis of polyacrylonitrile and poly(methyl methacrylate) with a relatively narrow molecular weight distribution were selected.     

N‐Bromosuccinimide as a thermal iniferter for radical polymerization

N‐Bromosuccinimide (NBS) was used as a thermal iniferter for the initiation of the bulk polymerizations of methyl methacrylate, methyl acrylate, and styrene. The polymerizations showed the characteristics of a living polymerization: both the yields and the molecular weights of the resultant polymers increased linearly as the reaction time increased. The molecular weight distributions of the polymers were 1.42–1.95 under the studied conditions. The resultant polymers could be used as macroiniferters to reinitiate the polymerization of the second monomer. The copolymers poly(methyl methacrylate)‐b‐polystyrene and polystyrene‐b‐poly(methyl methacrylate) were obtained and characterized. End‐group analysis of the resultant poly(methyl methacrylate), poly(methyl acrylate), and polystyrene confirmed that NBS behaved as a thermal iniferter. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 2567–2573, 2005     

Radical polymerization in the presence of vinyl-substituted transition metal β-diketonates

The influence of vinyl-substituted cobalt(II), copper(II), nickel(II), and iron(II) β-diketonates on radical polymerization of methyl methacrylate and styrene was studied.     

Preparation of polyethylene block copolymers by a combination of postmetallocene catalysis of ethylene polymerization and atom transfer radical polymerization

The synthesis of block copolymers consisting of a polyethylene segment and either a poly(meth)acrylate or polystyrene segment was accomplished through the combination of postmetallocene-mediated ethylene polymerization and subsequent atom transfer radical polymerization. A vinyl-terminated polyethylene (number-average molecular weight = 1800, weight-average molecular weight/number-average molecular weight =1.70) was synthesized by the polymerization of ethylene with a phenoxyimine zirconium complex as a catalyst activated with methylalumoxane (MAO). This polyethylene was efficiently converted into an atom transfer radical polymerization macroinitiator by the addition of α-bromoisobutyric acid to the vinyl chain end, and the polyethylene macroinitiator was used for the atom transfer radical polymerization of n-butyl acrylate, methyl methacrylate, or styrene; this resulted in defined polyethylene-b-poly(n-butyl acrylate), polyethylene-b-poly(methyl methacrylate), and polyethylene-b-polystyrene block copolymers. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 496–504, 2004     

Synthesis of homopolymers and block copolymers of methyl methacrylate and styrene in the presence of bis(3,6-ditert-butylcatecholato)tin(IV) ditetrahydrofuranate

The specific features of synthesis of poly(methyl methacrylate) and polystyrene in the presence of bis(3,6-ditert-butylcatecholato)tin(IV) ditetrahydrofuranate were studied. It was found that the catecholate tin complex can efficiently influence both the kinetic parameters of radical polymerization of the monomers and molecular mass characteristics of the product polymers. With the use on macroinitiators obtained in the presence of bis(3,6-ditert-butylcatecholato)tin(IV) ditetrahydrofuranate, block copolymers were synthesized.     

Polymerization of coordinated monomers. X. Kinetic study of alternating copolymerization of methyl methacrylate and styrene with stannic chloride in dichloroethane

The alternating copolymerization of methyl methacrylate with styrene with the use of stannic chloride was kinetically examined at ?20°C in 1,2-dichloroethane both under photoirradiation and with radical initiator (2:1 tri-n-butylboron-benzoyl peroxide system). At conversions lower than 7%, the conversion increases linearly to the polymerization time, whereas the degree of polymerization is constant irrespective of the polymerization time. The alternating copolymerizations are 1.5 order and the 1.0 order reactions with respect to the ternary molecular complex composed of stannic chloride, methyl methacrylate, and styrene, under photoirradiation and with initiator, respectively. The linear dependences of the rates upon the 0.5 order of the intensity of the incident light and upon the 1.0 order of the concentration of tri-n-butylboron indicate a bimolecular termination. The rate normalized by the 1.5 order of the concentration of the coordinated methyl methacrylate and the rate normalized by the concentration of the coordinated methyl methacrylate are proportional to the 1.5 and 1.0 orders of the charged concentration of styrene, for the copolymerizations under photoirradiation and with initiator, respectively. The kinetic results in the 1,2-dichloroethane solution are quite consistent with those in the toluene solution. The alternating copolymerization mechanism, in which the ternary molecular complex predominantly homopolymerizes as a monomer unit, is confirmed.     

New ligands for atom‐transfer radical polymerization

A new type of ligands based on organic acids, such as acetic acid, iminodiacetic acid, succinic acid and isophthalic acid, has been successfully employed in the iron‐mediated atom‐transfer radical polymerization (ATRP) of vinyl monomers, such as styrene (St) and methyl methacrylate (MMA). The systems containing different organic acids can react at 250°C to 1300°C in “living”/controlled radical polymerizations giving polymers with relatively narrow molecular weight distributions (M_w/M_n = 1.2–1.5). ¹H NMR spectroscopy has been used to study the structure of the resulting polymers. Block copolymers were synthesized to confirm the ìlivingî nature of the system. The measured molecular weights are close to the calculated values for the polymerization of MMA and are somewhat lower than the theoretical ones for styrene.     

活性正离子聚合与原子转移自由基聚合转换合成聚β-蒎烯接枝共聚物

通过活性正离子聚合与原子转移自由基聚合(ATRP)转换合成了β-蒎烯与甲基丙烯酸甲酯(MMA)、丙烯酸丁酯(BA)、苯乙烯(St)的新型接枝共聚物.首先以α-氯代乙苯/TiCl4/Ti(OiPr)4/nBu4NCl体系引发β-蒎烯活性正离子聚合,合成预定分子量大小和窄分子量分布的聚β-蒎烯,然后经N-溴代琥珀酰亚胺(NBS)定量溴化,得到溴化聚β-蒎烯大分子引发剂(Br/β-蒎烯链节摩尔比为0.5).然后将该大分子引发剂与溴化亚铜(CuBr)/2,2′-联吡啶(bpy)复合,引发MMA、BA、St进行ATRP接枝聚合.接枝反应显示一级动力学特征,且产物的分子量及分子量分布可控,表明上述ATRP接枝聚合反应具有可控聚合特征.接枝产物的结构经1H-NMR分析得到进一步证实.     

A new form of controlled growth free radical polymerization

A new form of controlled growth free radical polymerization leading to narrow polydispersity polymers and/or block copolymers is described. The process is based on the polymerization of monomers in the presence of macromonomers of general structure CH₂=C(Z)CH₂(A)_n [(A)_n= radical leaving group, Z = activating group] and displays many of the characteristics of living polymerizations. The process is most suited to methacrylic monomers but with the appropriate choice of reaction conditions (high temperatures and/or low conversions) it can also be applied to acrylic and styrenic monomers. The macromonomers are conveniently prepared by catalytic chain transfer to alkyl cobalt(III) complexes or by addition-fragmentation chain transfer. The factors which determine the efficiency of cobalt complexes for molecular weight reduction in free radical emulsion and solution polymerization of methyl methacrylate are also discussed.