Anionic living polymerization of styrenes containing electron-withdrawing groups

Six styrene derivatives containing electron-withdrawing groups were synthesized and polymerized with anionic initiators in THF to afford stable anionic living polymers. The electron-withdrawing substituents are N,N-dialkylamide(1), N-alkylimino(2), oxazoline(3), tert-butyl ester(4), N,N-dialkylsulfonamide(5) and cyano(6) moieties. The polymers obtained have predictable molecular weights and narrow molecular weight distributions. The respective postpolymerizations proceeded with quantitative efficiency indicating that each polymer chain end retained the propagating reactivity. However, the resulting living polymers could not initiate the polymerizations of styrene and isoprene. On the other hand, the styrene derivatives(5 and 6) were polymerized with weak nucleophilic initiators, such as living polymer of tert-butyl methacrylate. These results suggest that the electron-withdrawing groups stabilize the living ends and also activate the respective monomers for anionic polymerization. The substitution effect reflects on the ¹³C NMR chemical shift of β-carbon of each vinyl group. The signal of the β-carbon appeared at lower magnetic field than that of styrene indicating electron deficiency on the carbon-carbon double bond of these monomers.     

Effects of initiators and photo-acid generators on nitroxide-mediated photo-living radical polymerization of methyl methacrylate

The effects of the structure of initiators and photo-acid generators on the nitroxide-mediated photo-living radical polymerization of methyl methacrylate were explored. The bulk polymerization was performed at room temperature using nine different initiators in the presence of (4-tert-butylphenyl)diphenylsulfonium triflate as the photo-acid generator. 2,2′-Azobisisobutyronitrile, 2,2′-azobis(2,4-dimethylvaleronitrile), dimethyl 2,2′-azobis(2-methylpropionate), and 2,2′-azobis(N-butyl-2-methylpropionamide) produced the polymers with a molecular weight distribution (MWD) around 1.6, while the racemic- and meso-(2RS,2′RS)-azobis(4-methoxy-2,4-dimethylvaleronitrile) provided a 1.4 MWD. 2,2′-Azobis(2-methylbutyronitrile), 1,1′-azobis(cyclohexane-1-carbonitrile), and 1-(cyano-1-methylethoxy)-4-methoxy-2,2,6,6-tetramethylpiperidine produced a broad MWD over 4.0. The structure of the photo-acid generator also had an influence on the molecular weight control. The photo-acid generator of sulfonium salts supporting the alkyl, methoxy, phenoxy, methylthio, and tert-butoxycarbonylmethoxy groups, coupled with halogens with the exception of the iodide had no effect on the MWD. On the other hand, the salts containing the iodide, phenylthio, and naphthyl groups produced polymers with broad MWDs and with uncontrolled high molecular weights.     

Anionic polymerization. IV. Effect of crown ethers on alkylsodium initiator

The polymerization of butadiene and copolymerization of butadiene-styrene with alkylsodium catalyst modified by crown ethers in hydrocarbon solvent has been investigated. This catalyst system produced polybutadiene of high viscosity (2.0–5.0) and high vinyl content (80%) in high conversion (75–95%). These results are in contrast to those obtained with aliphatic ether-modified alkylsodium polymerization which typically gives products of low molecular weight and at low conversion. The copolymerization of butadiene-styrene with alkylsodium catalyst modified by crown ethers gave a copolymer which did not contain block styrene. Although the copolymer did not contain block styrene, there was an unusually high level of incorporation of styrene in the copolymer at low conversion. This behavior is quite different from either modified organolithium or unmodified organosodium initiators, in which the styrene is uniformly and randomly incorporated along the chain.     

Branched polymers through redox emulsion polymerization using peroxide monomer as the branching agent

Redox emulsion polymerization to branched vinyl polymers in the presence of 2-(tert-butylperoxy)ethyl methacrylate (BPEMA), ferrous sulfate, and sodium formaldehyde sulfoxylate (SFS) is reported in this paper. The peroxide monomer BPEMA containing alkyl peroxide was designed for high stability during preparation and storage. Nuclear magnetic resonance spectroscopy (NMR), Raman, and triple-detection size-exclusion chromatography (TD-SEC) measurements were used to reveal the polymerization procedure and provide evidence of branching structure. In the case of polymerization at St₁₀₀-BPEMA_1.0-FeSO_{4 0.5}-SFS_0.2, the molecular weight increased and decreased with conversion below and above 75% monomer conversion, respectively. The decreasing of molecular weight with monomer conversion came from the increased viscosity of the micelle, which makes it difficult for the formed macromolecules containing vinyl group to participate into polymerization. Finally, the molecular weight reached a value of M_{n. SEC} = 439,200 g/mol at 92.2% conversion. In addition, the Zimm branching factor, g', also decreased and increased with conversion below and above 60% conversion, respectively, and then the g' finally attends a value of 0.41, showing high degree of branching. Branched poly(methyl methacrylate) was also prepared through this strategy, showing a versatile approach to branched vinyl polymers.     

Anionic ring‐opening polymerization of a five‐membered cyclic carbonate having a glucopyranoside structure

Anionic ring‐opening polymerizations of methyl 4,6‐O‐benzylidene‐2,3‐O‐carbonyl‐α‐D ‐glucopyranoside (MBCG) were investigated using various anionic polymerization initiators. Polymerizations of the cyclic carbonate readily proceeded by using highly active initiators such as n‐butyllithium, lithium tert‐butoxide, sodium tert‐butoxide, potassium tert‐butoxide, and 1,8‐diazabicyclo[5.4.0]undec‐7‐ene, whereas it did not proceed by using N,N‐dimethyl‐4‐aminopyridine and pyridine as initiators. In a polymerization of MBCG (1.0 M), 99% of MBCG was converted within 30 s to give the corresponding polymer with number‐averaged molecular weight (M_n) of 16,000. However, the M_n of the polymer decreased to 7500 when the polymerization time was prolonged to 24 h. It is because a backbiting reaction might occur under the polymerization conditions. © 2013 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013     

Preparation and polymerization of methylenecyclobutene and 1-methyl-3-methylenecyclobutene

Methylenecyclobutene (MCB) and 1-methyl-3-methylenecyclobutene (MMCB) were synthesized, characterized, and polymerized by anionic and cationic initiators. Structural analyses of the polymers were carried out by infrared and NMR spectros-copy. The cationic polymerization of MCB appeared to proceed entirely by a 1,5-propagation mechanism to form low molecular weight polymers in low yields. Anionic polymerization of this monomer, on the other hand, proceeded primarily through a 1,2-propagation path, again forming only low molecular weight polymeric products in low yield. In contrast to MCB, the methyl-substituted monomer, MMCB, polymerized readily with cationic initiators to produce unusually high molecular weight polymers in high conversions. On the basis of both infrared and NMR spectroscopic analyses, it was concluded that the polymers also contained essentially only 1,5-addition repeating units. Anionic initiators such as n-BuLi were unable to induce polymerization of this monomer, but polymerization by Ziegler-Natta catalysts proceeded readily to yield polymers virtually identical in structure and molecular weight to those obtained with cationic initiators.     

Atom transfer radical polymerization of cyclohexyl methacrylate at a low temperature

The atom transfer radical polymerization of cyclohexyl methacrylate (CHMA) is reported. Controlled polymerizations were performed with the CuBr/N,N,N′,N″,N″‐pentamethyldiethylenetriamine catalytic system with ethyl 2‐bromoisobutyrate as the initiator in bulk and different solvents (25 vol %) at 40 °C. The polymerization of CHMA in bulk resulted in a controlled polymerization, although the concentration of active species was relatively elevated. The addition of a solvent was necessary to reduce the polymerization rate, which was dependent on the dipole moment. Well‐controlled polymers were obtained in toluene, diphenyl ether, and benzonitrile solutions. Poly(cyclohexyl methacrylate) as a macroinitiator was used to synthesize the poly(cyclohexyl methacrylate)‐b‐poly(tert‐butyl methacrylate) block copolymer, which allowed a demonstration of its living character. In addition, two difunctional initiators, 1,4‐bis(bromoisobutyryloxy) benzene and 1,2‐bis(bromoisobutyryloxy) ethane, were used to initiate the atom transfer radical polymerization of CHMA. The experimental molecular weights of the obtained polymers were very close to the theoretical ones. These, along with the relative narrow molecular weight distributions, indicated that the polymerization was living and controlled. For confirmation, two different poly(tert‐butyl methacrylate)‐b‐poly(cyclohexyl methacrylate)‐b‐poly(tert‐butyl methacrylate) triblock copolymers were also synthesized. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 71–77, 2005     

Selective vinyl cationic polymerization of monomers with two cationically polymerizable groups. IV. New initiating systems for selective and living polymerization of p-isopropenylphenyl glycidyl ether

A variety of cationic initiators were employed for p-isopropenylphenyl glycidyl ether (IPGE), an α-methylstyrene derivative with an epoxy pendant, and optimum initiators and reaction conditions were evaluated in terms of its selective vinyl polymerization and living polymerization. Despite the coexistence of two cationically polymerizable groups in IPGE, binary initiating systems (HI, CF₃COOH, or CH₃CH(OiBu)-OCOCH₃, each coupled with ZnI₂) and sulfonic acids (CF₃SO₃H and CH₃SO₃H) selectively polymerized the vinyl group of IPGE in CH₂Cl₂ at ?78°C to produce soluble polymers with epoxy pendant groups in high yield. Metal halides (BF₃OEt₂ and AlEtCl₂) polymerized both the vinyl and epoxy groups of IPGE to give crosslinked insoluble polymers. In contrast, under these conditions, the HI/ZnI₂ system also led to a long-lived polymer, the molecular weight of which increased upon addition of a fresh feed of monomer to a completely polymerized reaction mixture, whereas the use of other initiators resulted in nonliving polymers. At higher temperatures (?40 and ?15°C), soluble poly(IPGE) was also obtained with HI/ZnI₂, but the polymer yield decreased with raising temperature, because of the occurrence of termination reaction.     

RAFT polymerization of alternating styrene‐pentafluorostyrene copolymers

Reversible addition‐fragmentation chain‐transfer (RAFT) polymerization was used to control the alternating copolymerization of styrene and 2,3,4,5,6‐pentaflurostyrene. The RAFT polymerization yields a high degree of control over the molecular weight of the polymers and does not significantly influence the reactivity ratios of the monomers. The controlled free‐radical polymerization could be initiated using AIBN at elevated temperatures or using a redox couple (benzoyl peroxide/N,N‐dimethylaniline) at room temperature, while maintaining control over molecular weight and dispersity. The influence of temperature and solvent on the molecular weight distribution and reactivity ratios were investigated. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 1555–1559     

Anionic polymerization of N,N‐dialkyl‐2‐methylenebut‐3‐enamide: Effect of alkyl substituents on polymerization behavior

Anionic polymerizations of three 1,3‐butadiene derivatives containing different N,N‐dialkyl amide functions, N,N‐diisopropylamide (DiPA), piperidineamide (PiA), and cis‐2,6‐dimethylpiperidineamide (DMPA) were performed under various conditions, and their polymerization behavior was compared with that of N,N‐diethylamide analogue (DEA), which was previously reported. When polymerization of DiPA was performed at ?78 °C with potassium counter ion, only trace amounts of oligomers were formed, whereas polymers with a narrow molecular weight distribution were obtained in moderate yield when DiPA was polymerized at 0 °C in the presence of LiCl. Decrease in molecular weight and broadening of molecular weight distribution were observed when polymerization was performed at a higher temperature of 20 °C, presumably because of the effect of ceiling temperature. In the case of DMPA, no polymer was formed at 0 °C and polymers with relatively broad molecular weight distributions (M_w/M_n = 1.2) were obtained at 20 °C. The polymerization rate of PiA was much faster than that of the other monomers, and poly(PiA) was obtained in high yield even at ?78 °C in 24 h. The microstructure of the resulting polymers were exclusively 1,4‐ for poly(DMPA), whereas 20–30% of the 1,2‐structure was contained in poly(DiPA) and poly(PiA). © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 3714–3721, 2010     

Ultrafast organocatalytic ring-opening polymerization of N-sulfonyl aziridine in the melt

An ultrafast approach for controlled synthesis of well-defined polysulfonamides is established through organocatalytic anionic ring-opening polymerization (ROP) of N-sulfonyl aziridine in the melt. Several different organobases are investigated, and it is found that N,N,N′,N″,N″-pentamethyldiethylenetriamine (PMDETA) catalyzed ROP of 2-methyl-N-tosylaziridine (TsMAz) gives the desired polymer, while 1,4-diazabicyclo[2.2.2]octane (DABCO) and 1,8-diazabicyclo[5.4.0]-undec-7-ene (DBU) initiate the polymerization along with initiator to produce uncontrolled polymers. Using PMDETA as the catalyst, poly(2-methyl-N-tosylaziridine) with molecular weight over 100 kg/mol can be synthesized in less than 90 s. Various initiators, including carboxylic acid, N-sulfonyl amide, unactivated amine, phenol, and thiol, are applicable for this protocol to give the molecular weight and end-group controlled polymers under the open-flask condition. Combining this ultrafast ROP with ring-opening metathesis polymerization (ROMP), a brush copolymer is facile synthesized. This approach allows the ultrafast metal-free synthesis of polysulfonamide and expands the scope of initiators for the ROP of N-sulfonyl aziridines.     

Anionic polymerization of acrylates. XI. Effect of composition and ageing of the Li ester enolate/tert‐butoxide initiating complex on the anionic polymerization of methyl methacrylate and 2‐ethylhexyl acrylate

The article presents the results of (meth)acrylate polymerization in THF initiated with various complexes of methyl 2‐lithioisobutyrate (MIB‐Li) and lithium tert‐buioxide (t‐BuOLi), prepared from the components in mole ratios 1:3, 1:6 and 1:10 in THF and aged for various time periods and at various temperatures. In dependence on the component ratio, temperature and storage time, the mixtures form cubic cross‐aggregates with MIB‐Li/t‐BuOLi mole ratios 3:1, 2:2 and 1:3 which exhibit different behavior when used as initiators. It was found that the way of synthesis of the complex and its structure not only affect the kinetics of polymerization but also distinctly change the microstructure of the formed polymers.     

Cationic polymerization of isobutyl vinyl ether initiated with transition‐metal ate complexes

The cationic polymerization of isobutyl vinyl ether was examined with transition‐metal ate complexes with trityl cation as initiators. The initiators were generated by the reaction of triphenylmethyl chloride [trityl chloride (TrCl)] with ate complexes of Nb, Mo, and W with lithium cation, which were obtained in situ by the reaction of the transition‐metal halides with anionic reagents (organolithium or lithium amide). When the polymerization was initiated with a mixture of TrCl and Li⁺[NbH₅(NnBuPh)]^?, the resulting poly(isobutyl vinyl ether)s had narrow molecular weight distributions (weight‐average molecular weight/number‐average molecular weight = 1.13–1.20). Although the polymerization was supposed to be initiated by the electrophilic attack of the trityl cation, matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry analysis of the resulting poly(isobutyl vinyl ether)s revealed the presence of H at the α‐chain end. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 2636–2641, 2006     

Stereoregulation in cationic polymerization by designed Lewis acids. II. Effects of alkyl vinyl ether structure

Stereoregulation in the cationic polymerization of various alkyl vinyl ethers was investigated with bis[(2,6‐diisopropyl)phenoxy]titanium dichloride ( 1 ; catalyst) in conjunction with the HCl adduct of isobutyl vinyl ether as an initiator in n‐hexane at −78 °C. The tacticities depended on the substituents of the monomers. Isobutyl and isopropyl vinyl ethers gave highly isotactic polymers (mm = 83%), whereas tert‐butyl and n‐butyl vinyl ethers resulted in lower isotactic contents (mm ∼ 50%) similar to those for TiCl₄, a conventional Lewis acid, thus indicating that the steric bulkiness of the substituents was not the critical factor in stereoregulation. A statistical analysis revealed that the high isospecificity was achieved not by the chain end but by the catalyst 1 or the counteranion derived therefrom. © 2001 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 39: 1060–1066, 2001     

Azobenzene‐based initiator for atom transfer radical polymerization of methyl methacrylate

2‐Bromopropionic acid 2‐(4‐phenylazophenyl)ethyl ester, 2‐bromopropionic acid 6‐(4‐phenylazophenoxy)hexyl ester (BPA₆), 2‐bromopropionic acid‐(4‐phenylazoanilide), and 2‐bromopropionic acid 4‐[4‐(2‐bromopropionyloxy)phenylazo]phenyl ester (BPPE) were used as initiators with monofunctional or difunctional azobenzene for the heterogeneous atom transfer radical polymerization of methyl methacrylate with a copper(I) chloride/N,N,N′,N″,N″‐pentamethyldiethylenetriamine catalytic system. The rates of polymerizations exhibited first‐order kinetics with respect to the monomer, and a linear increase in the number‐average molecular weight with increasing monomer conversion was observed for these initiation systems. The polydispersity indices of the polymer were relatively low (1.15–1.44) up to high conversions in all cases. The fastest rate of polymerization and the highest initiation efficiency were achieved with BPA₆, and this could be explained by the longer distance between the halogen and azobenzene groups and the better solubility of the BPA₆ initiator. The redshifting of the UV absorptions of the polymers only occurred for the BPPE‐initiated system. The intensity of the UV absorptions of the polymers were weaker than those of the corresponding initiators in chloroform and decreased with the increasing molecular weights of the polymers in all cases. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 2358–2367, 2005     

Selective vinyl cationic polymerization of monomers with two cationically polymerizable groups. II. p-vinylphenyl glycidyl ether: An epoxy-functionalized styrene

p-Vinylphenyl glycidyl ether (VPGE), a styrene derivative with an epoxy pendant, was polymerized by various cationic initiators, and its selective vinyl polymerization was investigated at low temperatures below ?15°C. BF₃OEt₂ (a metal halide) and CF₃SO₃H (a strong protonic acid) polymerized both vinyl and epoxy groups of VPGE, and produced cross-linked insoluble polymers. The HI/I₂ initiating system and iodine, in contrast, polymerized its vinyl group in polar solvents (CH₂Cl₂ and nitroethane) highly selectively in the temperature range of ?15 to ?40°C to give soluble polymers with a polystyrene backbone and epoxy pendants; however, under these conditions, 10–15% of the epoxy groups of the polymers were consumed during the polymerization by the reaction with the growing species. The polymerization by HI/I₂ in CH₂CI₂ involved a long-lived propagating species, as indicated by a progressive increase in the molecular weight (M?_n) of the polymers with monomer conversion and their fairly narrow molecular weight distributions (M?_w/M?_n ～ 1.6). The differences between the polymerizations of VPGE and p-isopropenylphenyl glycidyl ether, an α-methylstyrene-type counterpart of VPGE, were also discussed with an emphasis on the effects of the α-methyl group in the latter monomer.     

Laccase-catalyzed polymerization of acrylamide

Enzymatic polymerization of acrylamide was carried out in water. Laccase, a copper-containing oxidoreductase derived from Pycnoporus coccineus, induced the polymerization at relatively low temperature (50°C) to give a polymer of high molecular weight. In the presence of 2,4-pentanedione, laccase efficiently mediated the vinyl polymerization at room temperature.     

Emulsion polymerization and copolymerization of vinyl benzoate

Emulsion polymerization of vinyl benzoate and its copolymerization with vinyl acetate or styrene are described. The effect of the potassium persulfate initiator, and the sodium lauryl sulfate emulsifier concentration on the rate of vinyl benzote homopolymerization and the molecular weight of the polymers was determined. In copolymerization with vinyl benzoate, both comonomers, vinyl acetate and styrene, decrease the initial polymerization rate. With increasing amounts of styrene in the comonomer mixture the polymerization rate increases but with vinyl acetate an opposite effect is observed. Reactivity ratios of copolymerizations were determined. For the vinyl benzoate [M₁]-styrene [M₂] comonomer system a r₁ = 0.03 and a r₂ = 29.58 and for vinyl benzoate [M₁]-vinyl acetate [M₂], a r₁ = 1.93 and a r₂ = 0.20 was obtained. From the vinyl benzoate-styrene reactivity ratios the Qe parameters were calculated.     

End-Functionalized polymers by living cationic polymerization. IV. Poly(vinyl ethers) with acidic or basic terminal groups by functional initiator method

Carboxylic acid or primary amine-terminated poly(isobutyl vinyl ethers) were synthesized by living cationic polymerizations with functionalized initiators (CH₃CHIO? CH₂CH₂ ? X; X: that are the adducts of the corresponding vinyl ethers (CH₂ ? CH ? OCH₂CH₂? X) with hydrogen iodide. In the presence of iodine, these initiators induced living cationic polymerization of isobutyl vinyl ether to give polymers with the α-end group of X originating from the initiators. The polymer molecular weights were regulated by the monomer to initiator feed ratio and the molecular weight distributions were very narrow (M _w/M _n ≤ 1.15). Subsequent deprotection of the terminal group X led to polymers with a terminal carboxylic acid or primary amine. ¹H- and ¹³C-NMR analyses showed that the end functionalities of these polymers were all close to unity.     

Effect of acetylene on the γ-radiation-induced polymerization of ethylene

The effects of acetylene on the γ-radiation-induced polymerization of ethylene were studied from the viewpoint of the gaseous products and polymer structure. The experiments were carried out under a pressure of 400 kg/cm²; the temperature was 30°C; the does rate was 1.1 × 10⁵ rad/hr; and the acetylene content was 0–20%. The solid polymer was obtained in the polymerization of ethylene containing 2.2% acetylene, while the monomer containing 19.7% acetylene gave a yellowish viscous oil. The polymer yield and molecular weight decreased remarkably with acetylene content. The main gaseous product was hydrogen, and trace amounts of butane, butene-1, butadiene-1,3, and benzene and its derivatives were also observed. The rate of formation of hydrogen was almost independent of acetylene content and there was no difference in acetylene contents before and after the irradiation was found. The infrared spectra of the polymers showed the presence of vinylidene, trans-vinylene, and terminal vinyl unsaturations, 1,4-disubstituted benzene, and carbonyl groups. The contents of trans-vinylene, terminal vinyl, and methyl groups increased with acetylene content, and that of vinylidene was independent of acetylene content. The monomer reactivity ratios of ethylene and acetylene were evaluated as 45.5 and 66.0, respectively. On the basis of the results, the effects of acetylene on the γ-radiation-induced polymerization of ethylene were discussed.