Synthesis of hetero‐telechelic polymers by self‐polyaddition of monomers containing both oxetanyl and carboxyl groups

The synthesis and self‐polyaddition of new monomers, o‐, m‐, and p‐[(3‐ethyloxetane‐3‐yl)methoxyethyl]benzoic acid (o‐EOMB, m‐EOMB, and p‐EOMB) containing both oxetanyl groups and carboxyl groups were examined. The reactions of o‐EOMB, m‐EOMB, and p‐EOMB in the presence of tetraphenylphosphonium bromide as a catalyst in o‐dichlorobenzene at 150–170 °C resulted in self‐polyaddition to give the corresponding hetero‐telechelic polymers poly(o‐EOMB), poly(m‐EOMB), and poly(p‐EOMB) with M_ns = 14,500–33,400 in satisfactory yields. The M_n of poly(o‐EOMB) decreased at higher reaction temperatures than 150 °C, unlike those of poly(m‐EOMB) and poly(p‐EOMB), possibly due to inter‐ or intraester exchange side reactions. It was also found that the thermal properties and solubilities of these polymers were supposed with the proposed structures. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 7835–7842, 2008     

Aminimides derived from p‐substituted benzoylformic acid ester as thermal/photolatent bases and photoradical initiators

Derivatives of 1,1‐dimethyl‐1‐(2‐hydroxypropyl)amine benzoylformimide (BFI and 1a–c) were synthesized from 1,1‐dimethylhydrazine, propylene oxide, and p‐substituted benzoylformic acid ester, respectively, and their activity as thermal/photolatent bases and photoradical initiators was studied in detail. Their thermal decomposition activity increased by the electron‐donating substituents on the benzene ring, being in order of 1a (p‐NMe₂) > 1b (p‐MeO) > BFI (H) > 1c (p‐NO₂). Photolysis activities were also affected by the substituents, in the following order: 1b > BFI > 1a > 1c. Thermal and photoinduced base‐catalyzed polymerization of the epoxide/thiol system and photoradical polymerization of a vinyl monomer, 2‐hydroxylethyl methacrylate, were carried out by using the aminimides as latent initiators. Their activity as thermal base and photobase/radical initiators could be correlated to their thermal decomposition and the photolysis activity, respectively. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013, 51, 4292–4300     

Catalytic effect of dimethyl sulfoxide in the Cu(0)/tris(2‐dimethylaminoethyl)amine‐catalyzed living radical polymerization of methyl methacrylate at 0–90 °C initiated with CH3CHClI as a model compound for α,ω‐di(iodo)poly(vinyl chloride) chain ends

A variety of conditions, including catalysts [CuCl, CuI, Cu₂O, and Cu(0)], ligands [2,2′‐bipyridine (bpy), tris(2‐dimethylaminoethyl)amine (Me₆‐TREN), polyethyleneimine, and hexamethyl triethylenetetramine], initiators [CH₃CHClI, CH₂I₂, CHI₃, and F(CF₂)₈I], solvents [diphenyl ether, toluene, tetrahydrofuran, dimethyl sulfoxide (DMSO), dimethylformamide, ethylene carbonate, dimethylacetamide, and cyclohexanone], and temperatures [90, 25, and 0 °C] were studied to assess previous methods for poly(methyl methacrylate)‐b‐poly(vinyl chloride)‐b‐poly(methyl methacrylate) (PMMA‐b‐PVC‐b‐PMMA) synthesis by the living radical block copolymerization of methyl methacrylate (MMA) initiated with α,ω‐di(iodo)poly(vinyl chloride). CH₃CHClI was used as a model for α,ω‐di(iodo)poly(vinyl chloride) employed as a macroinitiator in the living radical block copolymerization of MMA. Two groups of methods evolved. The first involved CuCl/bpy or Me₆‐TREN at 90 °C, whereas the second involved Cu(0)/Me₆‐TREN in DMSO at 25 or 0 °C. Related ligands were used in both methods. The highest initiator efficiency and rate of polymerization were obtained with Cu(0)/Me₆‐TREN in DMSO at 25 °C. This demonstrated that the ultrafast block copolymerization reported previously is the most efficient with respect to the rate of polymerization and precision of the PMMA‐b‐PVC‐b‐PMMA architecture. Moreover, Cu(0)/Me₆‐TREN‐catalyzed polymerization exhibits an external first order of reaction in DMSO, and so this solvent has a catalytic effect in this living radical polymerization (LRP). This polymerization can be performed between 90 and 0 °C and provides access to controlled poly(methyl methacrylate) tacticity by LRP and block copolymerization. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 1935–1947, 2005     

Novel pyridinium salts as cationic thermal and photoinitiators and their photosensitization properties

Novel pyridinium salts [N‐(α‐phenylbenzyl)‐, N‐(1‐naphthylmethyl)‐, or N‐cinnamyl p‐ or o‐cyanopyridinium hexafluoroantimonates] were synthesized by the reaction of p‐ or o‐cyanopyridine and the corresponding bromides followed by anion exchange with KSbF₆. These pyridinium salts polymerized epoxy monomers at lower temperatures than previously reported for N‐benzyl‐2‐cyanopyridinium hexafluoroantimonate. The o‐substituted pyridinium salts showed higher activity than the p‐substituted ones, and the crosslinked epoxy polymers cured with these initiators showed higher glass‐transition temperatures. These pyridinium salts photoinitiated radical polymerization as well as cationic polymerization. The photopolymerization was accelerated by the addition of aromatic ketones as photosensitizers. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 1037–1046, 2002     

Helix‐sense‐selective copolymerization of triphenylmethyl methacrylate with chiral 2‐isopropenyl‐4‐phenyl‐2‐oxazoline

The asymmetric induction leading to a one‐handed helix was investigated in the anionic and radical copolymerization of triphenylmethyl methacrylate (TrMA) and (S)‐2‐isopropenyl‐4‐phenyl‐2‐oxazoline ((S)‐IPO), and highly isotactic copolymers with a reasonable optical activity were obtained. In the anionic copolymerization, the optical activity of the obtained copolymers depended on the polarity of solvents, and a highly optically active copolymer was produced in the copolymerization in toluene. The chiral oxazoline monomer functioned not only as a comonomer but also as a chiral ligand to endow the polymer with large negative optical rotation in the copolymerization with TrMA. The copolymers with small positive optical rotation were obtained in THF, indicating that IPO unit may work only as the chiral monomer that dictates the helical sense via copolymerization with TrMA. The isotacticity of the obtained copolymers depended on the contents of TrMA units in the copolymers, but was almost independent of the solvent for copolymerization. In the radical copolymerization, the obtained copolymers exhibited small optical activities. It seemed that the chiral monomer cannot induce one‐handed helical structure of TrMA sequences even if the sequences probably have a high isotacticity. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019 , 57, 441–447     

Asymmetric anionic polymerization of (2-fluorophenyl)(4-fluorophenyl)(2-pyridyl)methyl methacrylate leading to a helical polymer

A novel racemic methacrylate, (2-fluorophenyl)(4-fluorophenyl)(2-pyridyl)-methyl methacrylate¹ (2F4F2PyMA), was synthesized and polymerized with chiral complexes of N,N′-diphenylethylenediamine monolithium amide (DPEDA-Li) with (−)-sparteine (Sp), (2S, 3S)-(+)-2,3-dimethoxy-1,4-bis(dimethylamino)butane (DDB), and (S)-(+)-1-(2-pyrrolidinylmethyl)pyrrolidine (PMP) in toluene at −78°C. The monomer showed higher resistance against methanolysis compared with triphenylmethyl methacrylate (TrMA) and several other analogues. In the asymmetric anionic polymerization of 2F4F2PyMA, PMP was found to be a more effective chiral ligand than DDB and Sp and gave quantitatively an optically active polymer with nearly perfect isotacticity. Enantiomer selection was observed in the polymerization of racemic 2F4F2PyMA with the chiral lithium complexes. Chiral recognition ability of the optically active poly(2F4F2PyMA) was examined by an enantioselective adsorption experiment. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 2013–2019, 1998     

Synthesis of novel ionic polymers containing arsonic acid group

Synthesis of ortho‐ and para‐acryloylaminophenylarsonic acids (o‐AAPHA and p‐AAPHA) monomers and their homopolymers, useful as ion‐exchange materials, are reported. Both the monomers and homopolymers are synthesized with >90% yield. The structures of the new compounds are determined by NMR and FTIR spectroscopy. Molecular weights of the polymers are determined from light scattering measurements and found to be M_w = 38,759 g/mol for o‐AAPHA polymer and M_w = 31,347 g/mol for p‐AAPHA polymer. Good thermal stability of the new compounds derived from their intra‐ or intermolecular hydrogen bondings suggests their applications as proton‐exchange membrane at high temperatures. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 1627–1634, 2006     

Rare‐earth‐metal‐initiated polymerizations of (meth)acrylates and block copolymerizations of olefins with polar monomers

The organo‐rare‐earth‐metal‐initiated living polymerization of methyl methacrylate (MMA) was first discovered in 1992 with (C₅Me₅)₂LnR (where R is H or Me and Ln is Sm, Yb, Y, or La) as an initiator. These polymerizations provided highly syndiotactic (>96%) poly(methyl methacrylate) (PMMA) with a high number‐average molecular weight (M_n > 1000 × 10³) and a very narrow molecular weight distribution [weight‐average molecular weight/number‐average molecular weight (M_w/M_n) < 1.04] quantitatively in a short period. Bridged rare‐earth‐metallocene derivatives were used to perform the block copolymerization of ethylene or 1‐hexene with MMA, methyl acrylate, cyclic carbonate, or ?‐caprolactone in a voluntary ratio. Highly isotactic (97%), monodisperse, high molecular weight (M_n > 500 × 10³, M_w/M_n < 1.1) PMMA was first obtained in 1998 with [(Me₃Si)₃C]₂Yb. Stereocomplexes prepared by the mixing of the resulting syndiotactic and isotactic PMMA revealed improved physical properties. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 1955–1959, 2001     

Asymmetric polymerization of the mixture of TrMA and MMA initiated by chiral complexes

A mixture of triphenylmethyl methacrylate (TrMA) and methyl methacrylate (MMA) was polymerized with chiral anionic initiator, such as fluorenyl lithium(−)-sparteine [FlLi-(−)-Sp] and fluorenyl lithium-(+)-2S,3S-dimethoxy-1,4-bis(dimethylamino)butane [FlLi-(+)-DDB] in toluene at −78°C. The results show that after the stable helix formed, when FlLi-(+)-DDB was used as the initiator, TrMA and MMA could be copolymerized, whereas when FlLi-(−)-Sp was used, the two monomers tended to be selectively polymerized into two polymers. This phenomenon has been explained by the existence of helix-selective polymerization. © John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35 : 1925–1931, 1997     

Novel Copolymers of Halogen Ring Substituted 2-Cyano-3-Phenyl-2-Propen- Amides and Styrene

ABSTRACT

Electrophilic trisubstituted ethylene monomers, halogen ring substituted 2-cyano-3-phenyl-2-propenamides, RC₆H₄CH=C(CN) CONH₂ (where R is o-Cl, m-Cl, p-Cl, p-Br, and p-F) were prepared by Knoevenagel condensation. Novel copolymers of the propenamides and styrene were prepared at equimolar monomer feed composition by solution copolymerization in the presence of a radical initiator at 80°C. The order of reactivity (1/r ₁) for the monomers (M₁=styrene) was o-Cl (1.42) > p-F (1.19) > p-Cl (0.70) > m-Cl (0.60) > p-Br (0.44).     

New approach to block copolymerization of ethylene with polar monomers by the unique catalytic function of organolanthanide complexes

This paper describes the first examples of ABA‐ and AB‐type block copolymerizations of a nonpolar monomer, in this case ethylene, with polar monomers, such as methyl methacrylate (MMA), ϵ‐caprolactone (CL), and 2,2‐dimethyltrimethylene carbonate (DTC), initiated by the unique catalytic function of rare earth metal complexes [Sm(II) and Ln(III) (Ln = Y, Sm)] as initiators. The Sm(II) species conducts the ABA‐type triblock copolymerization, leading to poly(MMA‐co‐ethylene‐co‐MMA), poly(CL‐co‐ethylene‐co‐CL), or poly(DTC‐co‐ethylene‐co‐DTC) by the efficient catalysis of racemic Me₂Si(C₅H₂‐2‐Me₃Si‐4‐tBu)₂Sm(THF)₂ ( 1 ) or meso Me₂Si(Me₂SiOSiMe₂)(C₅H₂‐3‐tBu)Sm(THF) ( 2b ). The resulting block copolymers are completely insoluble in THF and CHCl₃, but the homopolymers of MMA, CL, and DTC are freely soluble in these solvents. TEM profiles provide direct evidence for the block copolymerizations, where the spheric morphology of homogeneously dispersed polar polymers was observed. Ln(III) species, such as racemic Me₂Si(C₅H₂‐2‐Me₃Si‐4‐tBuMe₂Si)YH ( 5 ) and Me₂Si(C₅H₂‐2‐Me₃Si‐4‐tBu)SmH ( 6 ), afford AB‐type block copolymers between ethylene and MMA or CL, whose TEM images reveal the homogeneous dispersion of poly(MMA) or poly(CL) units in the polyethylene region. The ABA‐ and AB‐type block copolymers demonstrate high break stress and high tensile modulus as compared with their corresponding blended polymers. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 4095–4109, 2000     

Reactivity of methacrylates in anionic copolymerization with methyl methacrylate by n-BuLi

Monomer reactivity ratios, r₁ and r₂ were determined in the anionic copolymerizations of methyl methacrylate (MMA, M₁) with ethyl (EtMA), isopropyl (i-PrMA), tert-butyl (t-BuMA), benzyl (BzMA), α-methylbenzyl (MBMA), diphenylmethyl (DPMMA), α,α-dimethylbenzyl (DMBMA), and trityl (TrMA) methacrylates (M₂) by use of n-BuLi as an initiator in toluene and THF at -78°C. The order of the reactivity of the monomers towards MMA anion was DPMMA > BzMA > MMA > EtMA > MBMA > i-PrMA > t-BuMA > TrMA > DMBMA in toluene and TrMA > BzMA > MMA > DPMMA > EtMA > MBMA > i-PrMA > DMBMA > t-BuMA in THF. Except for the extremely low reactivity of TrMA and DPMMA in toluene due to steric hindrance, the order was explained in terms of the polar effect of the ester groups. A linear relationship was found between log (1/r₁) and Taft's σ* values of the ester groups, where the ρ* value was 1.1. The plots of log (1/r₁) vs. the ¹H_a (cis to the carbonyl) and ¹³C_ß chemical shifts of the monomers were also on straight lines. The polymer obtained in the copolymerization of MMA with TrMA in toluene by n-BuLi at -78°C was a mixture of poly-MMA and a copolymer, suggesting that there exist two kinds of growing centers.     

Synthesis and activity of aryl benzyl methyl sulfonium salts as cationic initiators: Effect of substituent on aryl group

Benzyl o-, m-, and p-substituted phenyl methyl sulfonium salts ( 2b – 2g ) were synthesized and their activities as cationic initiators were evaluated in the bulk polymerization of phenyl glycidyl ether (PGE). Especially, their activities were estimated with respect to the effect of substituents on the aryl groups. In the polymerizations of PGE with a series of benzyl p-substituted phenyl methyl sulfonium salts, the order of their activities was found to be 2c (CH₃OCOO) > 2b (CH₃COO) > 2d (CH₃O) ～ 2a (HO). In particular, 2c was the most active initiator of all, capable of initiating the polymerization of PGE even at room temperature. In the polymerizations with 2a, 2e (m-Cl), 2f (o-CH₃), and 2g (m-CH₃), the activity of 2e was the highest of all while those of 2a, 2f , and 2g were almost the same. These results strongly suggested that the electron-withdrawing group placed on the aryl group undoubtedly enhanced the activity of the sulfonium salts as the cationic initiators.     

Antithetic function of alcohol in living cationic polymerization: From terminator/inhibitor to useful initiator

We employed alcohols as initiators for living cationic polymerization of vinyl ethers and p‐methoxystyrene, coupled with tolerant Lewis acid, borontrifluoride etherate (BF₃OEt₂), although they were known to be poisonous reagent to bring about chain‐breaking such as chain transfer/termination rather than such beneficial one for propagation and polymerization‐control. As well known, without assistance of additive, ill‐defined polymers with broad molecular weight distributions (MWDs) were produced. Even addition of conventional oxygen‐based bases, for example, ethyl acetate (AcOEt), 1,4‐dioxane (DO), tetrahydrofran (THF), and diethyl ether (Et₂O) was less efficient in this system to control molecular weights and MWDs (M_w/M_n > 2.0). In contrast, by addition of dimethyl sulfide (Me₂S), MWDs of the resultant polymers became much narrower (M_w/M_n < 1.23) and the number‐average molecular weight (M_n) increased in direct proportion to monomer conversion in agreement with the calculated values assuming that one alcohol molecule generates one polymer chain. Studying changed feed‐ratio of alcohol to monomer and structural analyses with NMR and MALDI‐TOF‐MS indicated that quantitative initiation from alcohol giving alkoxide counteranion. This system opens a new way to use a variety of alcohols as initiators, which would allow us to design variety of structures and functions of counteranion. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 4194–4201, 2009     

Studies in aryltin chemistry: Part 13. Spectroscopic and fungicidal studies of some m‐ and o‐substituted triaryltin acetates,oxides and hydroxides

The fungicidal activity of a series of aryltin com‐<?tw=99%>pounds, Ar₃SnOAc (Ar = m‐Tol (m−CH₃C₆H₄),<?tw>­3,5‐Xyl [3,5‐(CH₃)₂C₆H₃], o‐Tol (o−CH₃C₆H₄) or Mes [2,4,6‐(CH₃)₃C₆H₂]) and (Ar₃Sn)₂O [Ar = m‐Tol, m‐Anis (m‐CH₃OC₆H₄), or o‐Tol] as well as (Mes)₃SnOH, for which IR and NMR (¹¹⁹Sn) data are reported, has been assessed­by radial growth assays on Aspergillus niger, Botrytis cinera, Mucor hiemalis, Fusarium solani and Penicillium chrysogenum, and the results­are compared with those for the corresponding triphenyl‐ and tris (p‐tolyl)‐tin compounds. In general, sterically hindered systems (Ar =­Mes) which are unlikely to achieve a trigonal‐bipyramidal five‐coordinate geometry at tin­with oxygen atoms in the axial positions, are ineffective as fungicides. However the o‐tolyltin compounds, particularly the acetate, show some fungicidal activity. A larger size (m‐Anis) or number (3,5‐Xyl) of meta groups decreases fungicidal activity (to zero against P. chryso‐­genum) in comparison with (m‐Tol)₃SnX. Indeed, where test substances are inactive as fungicides, they promote the growth rate of P.chrysogenum by up to 60%. The steric effects implied by these data suggest that dimensions of active sites in the F₀ unit of the ATPase enzyme may differ significantly for each fungus studied. A model for the active site is proposed, based on the need of the Ar₃Sn⁺ unit first to be able to reach the active site and then to occupy it with the required five‐coordinate geometry so as to inhibit the activity of the ATPase enzyme. Copyright © 2000 John Wiley & Sons, Ltd.     

Atom transfer radical polymerization of methyl methacrylate catalyzed by cobalt catalyst system

A new catalyst system, CoCl₂/tris(2‐(dimethyl amino) ethyl)amine (Me₆ TREN), was used to catalyze the polymerization of methyl methacrylate (MMA) successfully through atom transfer radical polymerization mechanism. The control over the polymerization was not ideal, the molecular weight distribution of the resulting polymer (PMMA) was relatively broad (M_w/M_n = 1.63–1.80). To improve its controllability, a small amount of hybrid deactivator (FeBr₃/Me₆TREN or CuBr₂/Me₆TREN) was added in the cobalt catalyst system. The results showed that the level of control over the polymerization was significantly improved with the hybrid cobalt–iron (or cobalt–copper) catalyst system; the polydispersity index of the resulting polymer was reduced to a low level (M_w/M_n = 1.15–1.46). Furthermore, with the hybrid cobalt–iron catalyst, the dependence of the propagation rate on the temperature and the copolymerization of methacrylate (MA) with PMMA‐Br as macroinitiator were also investigated. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 5207–5216, 2005     

Stereocontrol in the free‐radical polymerization of methacrylates with fluoroalcohols

The free‐radical polymerization of methyl methacrylate (MMA), ethyl methacrylate (EMA), isopropyl methacrylate (IPMA), and tert‐butyl methacrylate (t‐BuMA) was carried out under various conditions to achieve stereoregulation. In the MMA polymerization, syndiotactic specificity was enhanced by the use of fluoroalcohols, including (CF₃)₃COH as a solvent or an additive. The polymerization of MMA in (CF₃)₃COH at −98 °C achieved the highest syndiotacticity (rr = 93%) for the radical polymerization of methacrylates. Similar effects of fluoroalcohols enhancing syndiotactic specificity were also observed in the polymerization of EMA, whereas the effect was negligible in the IPMA polymerization. In contrast to the polymerizations of MMA and EMA, syndiotactic specificity was decreased by the use of (CF₃)₃COH in the t‐BuMA polymerization. The stereoeffects of fluoroalcohols seemed to be due to the hydrogen‐bonding interaction of the alcohols with monomers and growing species. The interaction was confirmed by NMR measurements. In addition, in the bulk polymerization of MMA at −78 °C, syndiotactic specificity and polymer yield increased even in the presence of a small amount {[(CF₃)₃COH]/[MMA]_o < 1} of (CF₃)₃COH. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 4693–4703, 2000     

Asymmetric anionic polymerizations of 7‐(o‐substituted phenyl)‐2,6‐dimethyl‐1,4‐benzoquinone methides: Electrostatic interaction and steric,inductive, and resonance effects of the ortho‐substituent on the optical activity

7‐(o‐Substituted phenyl)‐2,6‐dimethyl‐1,4‐benzoquinone methides which have an electron‐donating methoxy‐(o‐OMe, 2a ) and methyl‐ (o‐Me, 2b ) substituents or an electron‐withdrawing cyano‐ (o‐CN, 2c ) and trifluoromethyl‐ (o‐CF₃, 2d ) substituents at the ortho‐position of the aromatic ring and 7‐(m‐substituted phenyl)‐2,6‐dimethyl‐1,4‐benzoquinone methide with an electron‐withdrawing trifluoromethyl‐ (m‐CF₃, 2e ) substituent at the meta‐position of the aromatic ring were synthesized, and their asymmetric anionic polymerizations using the complex of lithium 4‐isopropylphenoxide with (?)‐sparteine were carried out in toluene at 0 °C. The polymers with negative optical activity were obtained for all of five monomers, and their specific rotation values largely changed depending upon the substituents of the monomers. On the basis of the comparison of various substituents effects, it was found that the specific rotation of obtained polymers is significantly affected by the electronic effects such as inductive and resonance effects rather than the steric and electrostatic effects of the substituent. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55 , 1048–1058     

Arene Selectivity by a Flexible Coordination Polymer Host

The coordination polymers [Ag₄(O₂CCF₃)₄(phen)₃] ? phen ? arene ( 1? phen ? arene) (phen=phenazine; arene=toluene, p‐xylene or benzene) have been synthesised from the solution phase in a series of arene solvents and crystallographically characterised. By contrast, analogous syntheses from o‐xylene and m‐xylene as the solvent yield the solvent‐free coordination polymer [Ag₄(O₂CCF₃)₄(phen)₂] ( 2 ). Toluene, p‐xylene and benzene have been successfully used in mixed‐arene syntheses to template the formation of coordination polymers 1? phen ? arene, which incorporate o‐ or m‐xylene. The selectivity of 1? phen ? arene for the arene guests was determined, through pairwise competition experiments, to be p‐xylene>toluene≈benzene>o‐xylene>m‐xylene. The largest selectivity coefficient was determined as 14.2 for p‐xylene:m‐xylene and the smallest was 1.0 for toluene:benzene.     

Arenesulfonyl bromides: The second universal class of functional initiators for the metal‐catalyzed living radical polymerization of methacrylates,acrylates, and styrenes

The metal‐catalyzed living radical polymerization of methyl methacrylate, n‐butyl acrylate, and styrene, initiated with p‐toluenesulfonyl bromide and phenoxybenzene‐4,4′‐disulfonyl bromide and catalyzed with CuBr/2,2′‐bipyridine (bpy) and various self‐regulated Cu‐based catalytic systems such as Cu₂O/bpy, Cu₂S/bpy, Cu₂Se/bpy, and Cu₂Te/bpy, is reported. Similarities and differences between the arenesulfonyl chloride and arenesulfonyl bromide initiators are discussed. The arenesulfonyl bromide initiators require reduced reaction times to produce polymers in high conversions under milder reaction conditions than the corresponding arenesulfonyl chloride initiators. At the same time, they exhibit 100% initiator efficiency and generate polymers with narrow molecular weight distributions and functional chain ends. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 319–330, 2005