MoO_2Br_2体系催化丁二烯聚合中烯丙基卤素的作用

ＭｏＯ２Ｂｒ２－Ａｌ（ｉ－Ｂｕ）２ＯＰｈＣＨ３（－ｍ）体系催化丁二烯１，２－聚合过程中添加Ｃ３Ｈ５Ｘ（Ｘ＝Ｃｌ、Ｂｒ和Ｉ）对聚合物分子量有较好的调节作用，其中以Ｃ３Ｈ５Ｂｒ的调节作用最强，Ｍｎ从１７．５×１０５降至３．５×１０５，但对催化活性有一定的影响．在测定催化体系的ＵＶ光谱、（１３）Ｃ－ＮＭＲ谱、聚合活性和聚合动力学参数的基础上，讨论了Ｃ３Ｈ５Ｘ在催化体系中的行为．     

A new synthetic route to polycarbonate

A detailed study has been carried out on the new synthetic reaction of poly(p-xylylene carbonate) from potassium carbonate and p-xylylene dibromide by using a variety of crown ethers as a catalyst, which was recently found by the present authors. Crown ethers having 18-member ring showed the best catalytic property of the various crown ethers, and the reaction was conducted in various solvents at 50–160°C by using 18-crown-6-ether. Both the polymer yield and the molecular weight of the polymer increased in proportion to the amount of potassium carbonate, and they increased rapidly and reached constant values with increasing the concentration of 18-crown-6-ether. They also depended significantly upon the reaction temperature as well as the solvent used. A maximum yield with the highest molecular weight was obtained from the reaction at 100–120°C in diglyme solvent. The spectroscopic analysis of the polymer indicated that all the end groups of the resulting polymer had the structure of benzyl bromide. From these results, a plausible mechanism was proposed for the reaction. Similar reactions were also conducted by using several aliphatic dibromides, Br? (CH₂)_x? Br, in place of p-xylylene dibromide. The products were strongly dependent of the value of x: polycarbonate was obtained from dibromides with ≧4, and cyclic carbonates from dibromides with ≦3.     

Ring-opening polymerization of macrocyclic aryl ether ketone oligomers containing the 1,2-dibenzoylbenzene moiety

Facile ring-opening polymerization of cyclic aryl ether oligomers containing the 1,2-dibenzoylbenzene moiety to form high molecular weight linear polymers in the presence of a nucleophilic initiator is described. The polymerization can be initiated in the melt in the presence of a nucleophilic initiator such as potassium carbonate, cesium fluoride, and alkali phenoxides. Various alkali phenoxides were investigated as potential nucleophilic initiators. The polymerization reaction rate in the melt increases in the order of K⁺ > Na⁺ > Cs⁺, and in the order of ⁻OPhPhO⁻ > PhO⁻ > PhOPhO⁻ > PhPhO⁻. However, the polymerization in an aprotic dipolar solvent is faster in the presence of cesium phenoxide than in the presence of potassium phenoxide. Polymerization of the cyclic oligomers in solution demonstrates that the ring-opening polymerization proceeds via a chain-growth mechanism and involves a transetherification reaction between linear and cyclic aryl ether oligomers. The ring-chain equilibrium is much more favorable towards linear polymers. Since little or no ring strain exists in the cyclic system, the transetherification reactions are indiscriminate with regards to cyclic or linear chains and the interchain equilibration is also a facile process during polymerization. This intermolecular transetherification has been demonstrated by using low molecular weight aryl ethers to control the molecular weight of the polymer formed via ring-opening polymerization. © 1996 John Wiley & Sons, Inc.     

SYNTHESIS AND POLYMERIZATION OF OLIGO (OXYETHYLENE) MACROMONOMER

This paper reports the synthesis of methoxyoligo (oxyethylene) methacrylate (MEO_n , n is the repeating unit number of (CH_2CH_2O) in the macromonomer), and its polymerization in different solvents. MEO_n is prepared through such two independent reactions as (1) anionic polymerization of oxirane initiated by potassium alkoxide and (2) end-capping of methoxy oligo(oxyethylene) by methacrylic group. The n value can be conveniently controlled over the range of 5 ～30 by varying the molar ratio of oxirane to initiator and the molecular weight distribution of MEO_n be narrowed by increasing reaction time only in step (1). MEO_n thus obtained shows a rapid polymerization in water and benzene respectively, and both give water-soluble polymers as long as suitable conditions are used.     

SYNTHESIS AND CHARACTERIZATION OF FOUR-ARMED BLOCK POLY(STYRENE-b-p-NITROPHENYL METHACRYLATE)PREPARED BY THE ATRP METHOD*

A novel tetrafunctional initiator, C [CH_2O (CH_2)_3 OOCCH(Br)CH_3]_4 (1), was synthesized through the reaction oftetraol with α-bromopropionyl chloride, and then was used as initiator of atom transfer radical polymerization (ATRP) in thepreparation of 4-armed polystyrene (PSt) with narrow polydispersity. The structure, molecular weight and molecular weightdistribution (MWD) of each arm were studied by ~1H-NMR and GPC data of hydrolyzed products of the 4-armed PSt. TheATRP of St using 1/CuBr/bpy as initiator system is of "living" character based on the following evidence: narrow MWD,constant concentration of chain radical during the polymerization, control of molecular weight by the molar ratio of monomerconsumed to 1. The 4-armed poly(St-b-p-nitrophenyl methacrylate) [poly(St-b-NPMA)] was prepared by the ATRP ofNPMA using 4-armed PSt with terminal bromine as the initiator, and characterized by FT-IR, ~1H-NMR spectra and GPCcurves. The micelles with PSt as core, and PNPMA as shell were formed by dropping DMSO into a solution of 4-armedpoly(St-b-NPMA) in DMF, as proved by laser light scatter (LLS) method.     

Facile Synthetic Access to Rhenium(II) Complexes: Activation of Carbon–Bromine Bonds by Single‐Electron Transfer

The five‐coordinated Re^I hydride complexes [Re(Br)(H)(NO)(PR₃)₂] (R=Cy 1 a , iPr 1 b ) were reacted with benzylbromide, thereby affording the 17‐electron mononuclear Re^II hydride complexes [Re(Br)₂(H)(NO)(PR₃)₂] (R=Cy 3 a , iPr 3 b ), which were characterized by EPR, cyclic voltammetry, and magnetic susceptibility measurements. In the case of dibromomethane or bromoform, the reaction of 1 afforded Re^II hydrides 3 in addition to Re^I carbene hydrides [Re(?CHR¹)(Br)(H)(NO)(PR₃)₂] (R¹=H 4 , Br 5 ; R=Cy a , iPr b ) in which the hydride ligand is positioned cis to the carbene ligand. For comparison, the dihydrogen Re^I dibromide complexes [Re(Br)₂(NO)(PR₃)₂(η²‐H₂)] (R=Cy 2 a , iPr 2 b ) were reacted with allyl‐ or benzylbromide, thereby affording the monophosphine Re^II complex salts [R₃PCH₂R′][Re(Br)₄(NO)(PR₃)] (R′=? CH?CH₂ 6 , Ph 7 ). The reduction of Re^II complexes has also been examined. Complex 3 a or 3 b can be reduced by zinc to afford 1 a or 1 b in high yield. Under catalytic conditions, this reaction enables homocoupling of benzylbromide (turnover frequency (TOF): 3 a 150, 3 b 134 h^?1) or allylbromide (TOF: 3 a 575, 3 b 562 h^?1). The reaction of 6 a and 6 b with zinc in acetonitrile affords in good yields the monophosphine Re^I complexes [Re(Br)₂(NO)(MeCN)₂(PR₃)] (R=Cy 8 a , iPr 8 b ), which showed high catalytic activity toward highly selective dehydrogenative silylation of styrenes (maximum TOF of 61 h^?1). Single‐electron transfer (SET) mechanisms were proposed for all these transformations. The molecular structures of 3 a , 6 a , 6 b , 7 a , 7 b , and 8 a were established by single‐crystal X‐ray diffraction studies.     

Living radical polymerization of methyl methacrylate with a zerovalent nickel complex,Ni(PPh3)

A zerovalent nickel complex, Ni(PPh₃)₄, induced living radical polymerization of methyl methacrylate (MMA) in conjunction with an organic bromide as an initiator [R–Br: CCl₃Br, (CH₃)₂C(CO₂Et)Br, (CH₃)₂C(COPh)Br] in the presence of Al(Oi-Pr)₃ additive. The molecular weight distributions were narrow (M̄_w/M̄_n ∼ 1.2) throughout the reactions, and the number-average molecular weights (M̄_n) increased in direct proportion to monomer conversion. In contrast, the polymers obtained with CCl₄ in place of R–Br had broader MWDs (M̄_w/M̄_n > 2). The Al(Oi-Pr)₃ additive should be added for the smooth polymerizations of MMA to occur, similarly to those with a divalent nickel bromide, NiBr₂(PPh₃)₂. The Ni(PPh₃)₄-mediated living polymerization apparently proceeds via the activation of the C Br bond from the initiators R Br, assisted by the redox reaction of the complex between Ni(0) and Ni(I) species. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 3003–3009, 1999     

Living cationic polymerization of vinyl ether with a cyclic acetal group

The living cationic polymerization of 5‐ethyl‐2‐methyl‐5‐(vinyloxymethyl)‐1,3‐dioxane ( 1 ), a vinyl ether with a cyclic acetal unit, was investigated with various initiating systems in toluene or methylene chloride at 0 to ?30 °C. With initiating systems such as hydrogen chloride (HCl)/zinc chloride (ZnCl₂), isobutyl vinyl ether–acetic acid adduct [CH₃CH(OiBu)OCOCH₃]/tin tetrabromide (SnBr₄)/di‐tert‐butylpyridine (DTBP), and CH₃CH(OiBu)OCOCH₃/ethylaluminum sesquichloride (Et_1.5AlCl_1.5)/ethyl acetate (CH₃COOEt), the number‐average molecular weights (M_n's) of the obtained poly( 1 )s increased in direct proportion to the monomer conversion and produced polymers with relatively narrow molecular weight distributions [MWDs; weight‐average molecular weight/number‐average molecular weight (M_w/M_n) = 1.2–1.3]. To investigate the living nature of the polymerization with CH₃CH(OiBu)OCOCH₃/SnBr₄/DTBP, a second monomer feed was added to the almost polymerized reaction mixture. The added monomer was completely consumed, and the M_n values of the polymers showed a direct increase against the conversion of the added monomer, indicating the formation of a long‐lived propagating species. The glass transition temperature and thermal decomposition temperature of poly( 1 ) (e.g., M_n = 13,600, M_w/M_n = 1.30) were 29 and 308 °C, respectively. The cyclic acetal group in the pendants of the polymer of 1 could be converted to the corresponding two hydroxy groups in a 65% yield by an acid‐catalyzed hydrolysis reaction. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 4855–4866, 2007     

Living cationic polymerization of vinyl ethers with carboxylic acid/tin tetrahalide initiating systems. I. New initiating systems based on acetic acid and selection of Lewis acid and basic additive leading to living polymers with low polydispersity

Cationic polymerization of isobutyl vinyl ether (IBVE) with acetic acid (CH₃COOH)/tin tetrahalide (SnX₄: X = Cl, Br, I) initiating systems in toluene solvent at 0°C was investigated, and the reaction conditions for living polymerization of IBVE with the new initiating systems were established. Among these tin tetrahalides, SnBr₄ was found to be the most suitable Lewis acid to obtain living poly(IBVE) with a narrow molecular weight distribution (MWD). The polymerization with the CH₃COOH/SnBr₄ system, however, was accompanied with the formation of a small amount of another polymer fraction of very broad MWD, probably due to the occurrence of an uncontrolled initiation by SnBr₄ coupled with protonic impurity. Addition of 1,4-dioxane (1–1.25 vol %) or 2,6-di-tert-butylpyridine (0.1–0.6mM) to the polymerization mixture completely eliminated the uncontrolled polymer to give only the living polymer with very narrow MWD (M _w/M _n ≤ 1.1; M _w, weight-average molecular weight; M _n, number-average molecular weight). The M _n of the polymers increased in direct proportion to monomer conversion, continued to increase upon sequential addition of a fresh monomer feed, and was in good agreement with the calculated values assuming that one CH₃COOH molecule formed one polymer chain. Along with these results, kinetic study and direct ¹H-NMR observation of the living polymerization indicated that CH₃COOH and SnBr₄ act as so-called “initiator” and “activator”, respectively, and the living polymerization proceeds via an activation of the acetate dormant species. The basic additives such as 1,4-dioxane and 2,6-di-tert-butylpyridine would serve mainly as a “suppressor” of the uncontrolled initiation by SnBr₄. The polymers produced after quenching the living polymerization with methanol possessed the acetate dormant terminal and they induced living polymerization of IBVE in conjunction with SnBr₄ in the presence of 1,4-dioxane. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 3173–3185, 1998     

Isolation and identification of cyclic oligomers of the poly(ethylene terephthalate)–poly(ethylene isophthalate) copolymer

New cyclic oligomers of the copolymer of poly(ethylene terephthalate) (PET) and poly(ethylene isophthalate) (PEI) were isolated and identified. A condensation polymerization was carried out at a high temperature, and the solid‐state polymerization that followed yielded the high molecular weight polymer. The oligomers were extracted from the high molecular weight PET–PEI copolymer and separated with preparative high performance liquid chromatography techniques. Their chemical structures and properties were analyzed and determined by ¹H NMR, differential scanning calorimetry, and mass spectroscopy. The oligomers observed at early retention times were a cyclic dimer and cyclic trimers and consisted of [GT]₃, [GI]₂, [GI]₃, [GT]₂[GI]₁, and [GT]₁[GI]₂. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 881–889, 2003     

Effect of variation of [PMDETA]0/[Cu(I)Br]0 ratio on atom transfer radical polymerization of n‐butyl acrylate

A kinetic study was conducted to examine the effect of varying the ratio of ligand to transition metal in a Cu(I)Br/N,N,N′,N″,N″‐pentamethyldiethylenetriamine (PMDETA) catalyst system for atom transfer radical polymerization (ATRP) of n‐butyl acrylate (nBA) using methyl 2‐bromopropionate as the initiator. Experimental molecular weights were higher than theoretical when low molecular weight polymers were targeted at low ratios of [PMDETA]₀/[Cu(I)Br]₀ (< 1), indicating inefficient initiation/deactivation. A downward curvature in the plot of M_n versus conversion was observed at high monomer conversion when targeting high molecular weight polymers. This deviation became more significant when an excess of ligand was used, indicating a contribution of chain transfer to ligand. The maximum rate of polymerization was obtained at [PMDETA]₀/[Cu(I)Br]₀ ≈ 0.5 for bulk ATRP of nBA; however for polymerization in the presence of 10 vol% DMF, the maximum appeared at the ratio ≈ 1:1. Addition of acetone or DMF improved solubility of Cu(II) complex, which consequently improved the level of control over the polymerization at low ratios of [PMDETA]₀/[Cu(I)Br]₀, but also reduced the reaction rate. The polymerization rate increased with temperature, but at the expense of increased polydispersities. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 3285–3292, 2004     

Bismuth halide‐catalyzed polymerizations of ε‐caprolactone

In contrast to BiF₃, the other three Bi‐halides catalyzed the ring‐opening polymerization of ε‐caprolactone (ε‐CL) in bulk. A temperature of 140 °C was found to be advantageous for rapid polymerization and optimum molecular weights. At this temperature, the reactivity of the catalysts increases in the order BiCl₃ < BiBr₃ < BiJ₃. Variation of the monomer‐catalyst ratio (M/C) yielded number‐average molecular weights (M_ns) up to 80,000 Da (corrected SEC data, 120,000 Da uncorrected), but a proper control of the M_ns was not achieved. In addition to CH₂? OH endgroups, CH₂Cl, CH₂Br, and CH₂J endgroups were detected, but no evidence for a cationic polymerization mechanism was found. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 7483–7490, 2008     

Polymerization of phenylacetylene catalysed by RhTp(cod) and RhBp(cod) in ionic liquids: effect of alcohols and of tetraammonium halides

RhTp(cod) ( 1 ) and RhBp(cod) ( 2 ), almost inactive in CH₂Cl₂, became good catalysts of phenylacetylene polymerization in ionic liquids ([bmim]Cl, [bmim]BF₄: bmim = 1‐butyl‐3‐methylimidazolium, [mokt]BF₄: mokt = 1‐methyl‐3‐oktylimidazolium, [bumepy]BF₄: 1‐butyl‐4‐methylpyridinium) and in CH₂Cl₂ in the presence of tetraammonium halides ([R₄N]X, R = Bu, Et; X = Cl, Br). The highest yields of polyphenylacetylene with catalyst 1 were obtained in [bmim]Cl at 65°C (64% after 2 h) and in [mokt]BF₄ at 20°C (56% after 24 h). In alcohols (CH₃OH, (CH₃)₂CHOH, (CH₃)₃COH) as solvents, up to 100% of the polymer was produced. When a mixture of an ionic liquid and CH₃OH was used as the reaction medium, the polymer yield was similar to the yield achieved in an ionic liquid only, but the molecular weight increased remarkably. Tetraammonium salts, [R₄N]X, are co‐catalysts for 1 , and the yield of the polymer increased in the order [Et₄N]Br < [Bu₄N]Br < [Et₄N]Cl < [Bu₄N]Cl. Polymers with molecular weights from 6900 to 38 800 Da were obtained with catalyst 2 in [R₄N]Br or [R₄N]Cl, whereas in ionic liquids ([bmim]Cl, [bmim]BF₄) the corresponding molecular weights were higher, from 51 300 to 60 300 Da. Copyright © 2004 John Wiley & Sons, Ltd.     

Investigation of Mizoroki‐Heck coupling polymerization as a catalyst‐transfer condensation polymerization for synthesis of poly(p‐phenylenevinylene)

Mizoroki‐Heck coupling polymerization of 1,4‐bis[(2‐ethylhexyl)oxy]‐2‐iodo‐5‐vinylbenzene ( 1 ) and its bromo counterpart 2 with a Pd initiator for the synthesis of poly(phenylenevinylene) (PPV) was investigated to see whether the polymerization proceeds in a chain‐growth polymerization manner. The polymerization of 1 with ^tBu₃PPd(Tolyl)Br ( 10 ) proceeded even at room temperature when 5.5 equiv of Cy₂NMe (Cy = cyclohexyl) was used as a base, but the molecular weight distribution of PPV was broad. The polymerization of 2 hardly proceeded at room temperature under the same conditions. In the polymerization of 1 , PPV with H at one end and I at the other was formed until the middle stage, and the polymer end groups were converted into tolyl and H in the final stage. The number‐average molecular weight (M_n) did not increase until about 90% monomer conversion and then sharply increased after that, indicating conventional step‐growth polymerization. The occurrence of step‐growth polymerization, not catalyst‐transfer chain‐growth polymerization, may be interpreted in terms of low coordination ability of H‐Pd(II)‐X(^tBu₃P) (X = Br or I), formed in the catalytic cycle of the Mizoroki‐Heck coupling reaction, to π‐electrons of the PPV backbone; reductive elimination of H‐X from this Pd species with base would take place after diffusion into the reaction mixture. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 543–551     

Poly(methylene sebacate): Synthesis and characterization

The synthesis of poly(methylene sebacate) was carried out via the reaction of cesium sebacate with bromochloromethane in N-methylpyrrolidone over a range of temperatures (55–130°C). A number of polymers having limiting viscosity numbers in the range of 0.29–0.94 dL g^?1 (CHCl₃; 25°C) were characterized by elemental analyses, ¹H- and ¹³C-NMR, DSC, and GPC techniques. The polymerization was found to be very rapid at 100°C, being complete in ca. 15 min. and was relatively insensitive to the stoichiometric ratio of the monomers. As high molecular weight polymers were produced without the quantitative conversion of the reactants, the polymerization is considered to be occurring by an interfacial mechanism.     

Kinetics of the reactions of Cl atoms with CH3Br and CH2Br2

The rate coefficients for the reactions of Cl atoms with CH₃Br, (k₁) and CH₂Br₂, (k₂) were measured as functions of temperature by generating Cl atoms via 308 nm laser photolysis of Cl₂ and measuring their temporal profiles via resonance fluorescence detection. The measured rate coefficients were: k₁ = (1.55 ± 0.18) × 10^?11 exp{(?1070 ± 50)/T} and k₂ = (6.37 ± 0.55) × 10^?12 exp{(?810 ± 50)/T} cm³ molecule^?1 s^?1. The possible interference of the reaction of CH₂Br product with Cl₂ in the measurement of k₁ was assessed from the temporal profiles of Cl at high concentrations of Cl₂ at 298 K. The rate coefficient at 298 K for the CH₂Br + Cl₂ reaction was derived to be (5.36 ± 0.56) × 10^?13 cm³ molecule^?1 s^?1. Based on the values of k₁ and k₂, it is deduced that global atmospheric lifetimes for CH₃Br and CH₂Br₂ are unlikely to be affected by loss via reaction with Cl atoms. In the marine boundary layer, the loss via reaction (1) may be significant if the Cl concentrations are high. If found to be true, the contribution from oceans to the overall CH₃Br budget may be less than what is currently assumed. © 1994 John Wiley & Sons, Inc.     

NEW NONGEMINAL CYCLOPHOSPHAZENES

A series of new nongeminally-substituted cyclic phosphazenes with various substituents has been prepared via deprotonation-substitution reactions at the Me groups of both the cis and trans isomers of [(Me)(Ph)PN] ₃ . Treatment of [(Me)(Ph)PN] ₃ with n-BuLi followed by reaction with organic electrophilic reagents affords a variety of cyclic derivatives, [(RCH ₂ )(Ph)PN] ₃ , [R = Me, Cl, Br, I, (CH ₂ ) ₂ Br, CH ₂ CH═CH ₂ , SR, C(═O)OLi, C(═O)OMe, C(═O)OEt]. The structures of theses cis cyclic phosphazenes, which were obtained by x-ray diffraction, illustrate the basket-like shape of the molecules. Heating the cis and trans isomers of the parent [(Me)(Ph)PN] ₃ produced mixtures of cyclic trimers and tetramers. The latter were isolated and characterized by x-ray crystallography. Nanoparticles of gold and silver were prepared by reduction of metal salts with a reducing agent in the presence of selected trimers.     

Investigation of catalyst‐transfer condensation polymerization for the synthesis of n‐type π‐conjugated polymer,poly(2‐dioxaalkylpyridine‐3,6‐diyl)

Kumada‐Tamao coupling polymerization of 6‐bromo‐3‐chloromagnesio‐2‐(3‐(2‐methoxyethoxy)propyl)pyridine 1 with a Ni catalyst and Suzuki‐Miyaura coupling polymerization of boronic ester monomer 2 , which has the same substituted pyridine structure, with ^tBu₃PPd(o‐tolyl)Br were investigated for the synthesis of a well‐defined n‐type π‐conjugated polymer. We first carried out a model reaction of 2,5‐dibromopyridine with 0.5 equivalent of phenylmagnesium chloride in the presence of Ni(dppp)Cl₂ and then observed exclusive formation of 2,5‐diphenylpyridine, indicating that successive coupling reaction took place via intramolecular transfer of Ni(0) catalyst on the pyridine ring. Then, we examined the Kumada‐Tamao polymerization of 1 and found that it proceeded homogeneously to afford soluble, regioregular head‐to‐tail poly(pyridine‐2,5‐diyl), poly(3‐(2‐(2‐(methoxyethoxy)propyl)pyridine) (PMEPPy). However, the molecular weight distribution of the polymers obtained with several Ni and Pd catalysts was very broad, and the matrix‐assisted laser desorption ionization time‐of‐flight mass spectra showed that the polymer had Br/Br and Br/H end groups, implying that the catalyst‐transfer polymerization is accompanied with disproportionation. Suzuki‐Miyaura polymerization of 2 with ^tBu₃PPd(o‐tolyl)Br also afforded PMEPPy with a broad molecular weight distribution, and the tolyl/tolyl‐ended polymer was a major product, again indicating the occurrence of disproportionation. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

Nonstoichiometric polycondensation I. synthesis of polythioether from dibromomethane and 4,4′-thiobisbenzenethiol

High molecular weight poly(phenylene thioether) ( 3 ) was successfully obtained by the polycondensation of 4,4′-thiobisbenzenethiol ( 1 ) and dibromomethane ( 2 ) with a variety of feed ratios in the presence of 1,8-diazabicyclo[5,4,0]undec-7-ene (DBU) in 1-methyl-2-pyrrolidinone (NMP) at 75°C. The resulting polymer showed the maximum inherent viscosity (η_inh) of 0.50 dL/g in 4 h when 1.5 equivalents excess of 2 was used. The model reaction using benzenethiol ( 4 ) and dichloromethane ( 5 ) in the presence of DBU in deuterated dimethylsulfoxide (DMSO-d₆) at 25°C indicated that the rate of the second nucleophilic displacement reaction (k₂) is 61 times faster than that of the first one (k₁). The maximum of theoretical molecular weights calculated at various stoichiometric imbalance (S) under the condition of k₂/k₁ = 61 showed a good agreement with the experimental molecular weights at specific polymerization times.     

A Copper-Based Reverse ATRP Process for the Living Radical Polymerization of 4-Vinylpyridine: Discussion on Optimum Reaction Conditions

In this original experiment, reverse atom transfer radical polymerization technique using CuCl₂/hexamethyl tris[2-(dimethylamino)ethyl]amine (Me₆-TREN) as catalyst complex was applied to living radical polymerization of 4-vinylpyridine (4VP) with azobisisobutyronitrile (AIBN) as initiator. N,N-Dimethylformamide was used as solvent to improve the solubility of the reaction system. The polymerization not only showed the best control of molecular weight and its distribution, but also provided a rather rapid reaction rate with the molar ratio of [4VP]:[AIBN]:[CuCl₂]:[Me₆-TREN] = 400:1:2:2. The rate of polymerization increased with increasing the polymerization temperature and the apparent activation energy was calculated to be 51.5 kJ· mol¹. Use of Cl as the halogen in copper halide had many advantages over the use of Br. The resulting poly(4-vinylpyridine) was successfully used as the macroinitiator to proceed the block polymerization of styrene in the presence of CuCl/Me₆-TREN catalyst complex via a conventional ATRP process in DMF.