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Scanning tunnelling microscopy revealed that the in situ metal coordination of a rufigallol derivative at the solid/liquid interface enables the formation of a well-organized columnar structure.

Various copolymers incorporated with β-substituted acrylates, such as alkyl crotonates (e.g., methyl crotonate (MC), ethyl crotonate (EC), isopropyl crotonate (iPC), and n-butyl crotonate (nBC)) and methyl cinnamate (MCin), were synthesized by group-transfer polymerization (GTP) using a silicon-based Lewis acid catalyst. In addition to β-substituted acrylates, α-substituted acrylates (e.g., methyl methacrylate (MMA) and n-butyl methacrylate (nBMA)) were examined as comonomers. Proton nuclear magnetic resonance (1H NMR) spectroscopy and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF-MS) characterizations of the obtained copolymers revealed that each monomer component was incorporated sufficiently. The thermal stabilities of the resulting copolymers were investigated by dynamic mechanical analysis (DMA), indicating that the glass-transition temperature (Tg) of the copolymers can be widely varied over a relatively high-temperature range by selecting the optimal comonomer. More specifically, the Tg values of poly(MC-random-EC) (MC/EC molar ratio = 50/50), poly(MC-random-nBC) (MC/nBC molar ratio = 50/50), poly(MC-random-MCin) (MC/MCin molar ratio = 54/46), and poly(nBC-random-MCin) (nBC/MCin molar ratio = 56/44) were 173, 130, 216, and 167 °C, respectively. The copolymerization of β-substituted acrylates (i.e., crotonates and a cinnamate) using an organo-catalyzed group-transfer polymerization system with N-(tert-butyldimethylsilyl)bis(trifluoromethanesulfonyl)imide (Tf2NSitBuMe2) and 1-methoxy-1-(tert-butyldimethylsiloxy)-2-methyl-1-propene (tBuMe2SKA) was investigated. The tert-butyldimethylsilyl moiety served as an effective means for suppressing the termination reactions of the GTP system. One-stage and two-stage copolymerization strategies employing different monomer feed methods were evaluated and gave random and block copolymers, respectively. The glass-transition temperatures of the prepared copolymers varied significantly depending on the comonomer used during the synthesis.

Poly(ethyl crotonate)s (PECs), possessing various disyndiotacticities, were synthesized by group-transfer polymerization using several silicon Lewis acid catalysts like N-(trialkylsilyl)bis(trifluo...

Biomass-based copolymers with alternating ricinoleic acid and 4-hydroxycinnamic acid derivatives (p-coumaric acid, ferulic acid, and sinapinic acid) exhibit a repeating structure based on soft and hard segments, derived from ricinoleic and 4-hydroxycinnamic acids, respectively. To achieve this alternating sequence, copolymers were synthesised by the self-condensation of hetero-dimeric monomers derived by the pre-coupling of methyl ricinolate and 4-hydroxycinnamic acid. The glass transition temperature (Tg) was observed to increase as the number of methoxy groups on the main chain increased; the Tg values of poly(coumaric acid-alt-ricinoleic acid), poly(ferulic acid-alt-ricinoleic acid), and poly(sinapinic acid-alt-ricinoleic acid) are −15 °C, −4 °C, and 24 °C respectively, 58 °C, 69 °C, and 97 °C higher than that of poly(ricinoleic acid). The polymers were processed into highly flexible, visually transparent films. Among them, poly(sinapinic acid-alt-ricinoleic acid) bearing two methoxy groups on each cinnamoyl unit, is mechanically the strongest polymer, with an elastic modulus of 126.5 MPa and a tensile strength at break of 15.47 MPa.

Kinetic modeling is effective in the development of efficient and manageable polymerization systems. Herein, a kinetic model of the group-transfer polymerization (GTP) of an alkyl crotonate using a silicon Lewis acid catalyst having a trialkylsilyl (trimethylsilyl, triethylsilyl, tert-butyldimethylsilyl, or triisopropylsilyl) moiety and various silyl ketene acetals with a corresponding trialkylsilyl moiety as an initiator is developed to understand the polymerization mechanism. The kinetic model quantitatively verifies proposed elementary reactions. When using a trimethylsilyl moiety, the activation energy of the cyclization reaction (a well-known termination reaction in GTP; Ec = 37.8 kJ mol−1) exceeds that of the propagation reaction (Ep = 28.6 kJ mol−1). This reveals that termination reactions are accelerated more than propagation reactions at high temperatures. In addition, comparison of various trialkylsilyl moieties confirmed that the greater bulkiness of the alkyl substituent on the silyl group increases the ratio of the activation energies of the cyclization and propagation reactions.

Cinnamic monomers, which are useful chemicals derived from biomass, contain α,β-unsaturated carbonyl groups with an aromatic ring at the β-position. Homopolymers synthesized by addition polymerization of these compounds are expected to be innovative bio-based polymer materials, as they have both polystyrene and polyacrylate structures. However, polymerization of these compounds by many methods is challenging, including by radical methods, owing to steric hindrance of the substituents and delocalization of electrons throughout the molecule via unsaturated π-bonding. Herein we report that homopolymers of these compounds with molecular weights (Mn) of ~18,100 g mol−1 and controlled polymer backbones can be synthesized by the group-transfer polymerization technique using organic acid catalysts. Additionally, these homopolymers are shown to have high heat resistance comparable to that of engineering plastics. Overall, these findings may open up possibilities for the convenient homopolymerization of cinnamic monomers to produce high-performance polymer materials. Cinnamic acid and related monomers are challenging to polymerise but offer interesting features combining structural elements of both acrylates and styrenes. Here homopolymers of cinnamic monomers are obtained by group transfer polymerisation under mild conditions.

Various poly(alkyl crotonate)s (PRCrs) were synthesized by group-transfer polymerization (GTP) using organic superacid catalysts such as 1-[bis(trifluoromethanesulfonyl)methyl]-2,3,4,5,6-pentafluorobenzene (C6H5CHTf2) and 1-trimethylsiloxyl-1-methoxy-2-methyl-1-propene (MTS) as an initiator. Under the optimized reaction conditions, the corresponding poly(ethyl crotonate) (PEtCr) was obtained with a narrow molecular weight distribution (MWD = 1.14) in quantitative yield (>99%). The thermal stabilities of the PRCrs obtained by organic acid-catalyzed GTP were generally superior to those of poly(alkyl methacrylate)s. The glass-transition temperature (Tg) of poly(methyl crotonate) (PMeCr) (122 °C) was higher than that of poly(methyl methacrylate) (PMMA) prepared by GTP (104 °C). The 5% weight loss temperature (Td5) of PMeCr (359 °C) was also higher than that of PMMA (304 °C). The values of the total light transmittance (Tt) (reaching 91.9%) and haze (

Four types of plastic films, polyethylene, polyvinylidene chloride, polyvinyl chloride, and a laminated film, and two types of rubber gloves, latex and nitrile, were examined. Small pieces of filter paper were covered with these materials, and a drop containing 100 kBq ofOur evaluation revealed that, when

The synthesis of cyclic thiocarbonates by the cycloaddition of carbon disulfide (CS2) to thiiranes in the presence of silica-immobilized amine catalysts was investigated. The catalytic activities of the silica-immobilized catalysts toward the synthesis of cyclic thiocarbonates were higher than the activities of their homogeneous counterparts. The silica-supported catalysts strongly accelerated the cycloaddition of CS2 to thiiranes, and the pseudo-first-order rate constant of the silica-immobilized catalyst was about 430 times larger than that of the corresponding homogeneous catalyst. The coexistence of the molecular catalyst species and the neighboring surface silanols on the catalyst support was found to be key to the reaction acceleration. In addition to providing improved catalytic activity, the solid-supported catalysts were also shown to be recyclable and reusable for at least five cycles.

A bis(tri-n-butylphosphine)palladium ((nBu3P)2Pd) complex was shown to catalyze the cyclization of arylallenes with carbon dioxide to yield six-membered lactones. The stoichiometric reaction of a (Me3P)2Pd complex with 1 equiv of arylallenes, followed by treatment with CO2, resulted in the formation of five-membered palladalactones, the structures of which were fully characterized by X-ray crystallography, NMR, IR, HRMS, and elemental analysis.

Pt nanoparticles were immobilized inside a microreactor to catalyze the hydrogenation of nitrobenzene to aniline. Catalyst support layers were provided on the inner wall of the microreactor to enhance the adsorption and reaction of the Pt nanoparticles. Using this immobilization method, the Pt nanoparticles inside the microreactor exhibited a good catalytic activity and also were easily regenerated even after they were deactivated. During a 14-h continuous experiment, the average yield of aniline was higher than 92% for 50 mM initial nitrobenzene concentration with the retention time of 12 s. This is equivalent to a turnover frequency of 3200 h−1. The deactivation mechanism of the Pt nanoparticles was also discussed in a long-time reaction.

A series of Pd catalysts supported on various silicas including mesoporous silica and non-porous silica was prepared in order to elucidate activity controlling factors for the selective hydrogenation of 1-nitrohexane to N-hexyl hydroxylamine (nHex-NHOH). The Pd on silica (5 wt.%) catalysts were characterized by XRD, N2 adsorption/desorption, and CO chemisorption. The hydrogenation was done in isopropyl alcohol under 1 bar of H2 at room temperature. The Pd catalysts supported on non-porous silica or silicas that possessed large pores efficiently produced nHex-NHOH in high yields, presumably because the influence of pore diffusion was small. Additionally, the catalytic activity strongly depended on the Pd dispersion: the activity generally decreased with the increased Pd dispersion (or the decreased Pd particle size). On the other hand, the yield of nHex-NHOH was little affected by the initial oxidation state of surface Pd before hydrogenation.

The acid−base reaction between lanthanide tris(alkyl) complexes Ln(CH2SiMe3)3(THF)2 and 2 equiv of HC5Me4SiMe3 in THF or hexane at room temperature resulted in the formation of metallocene complexes [(η5:η1-C5Me4SiMe2CH2)Ln(C5Me4SiMe3)(THF)] (Ln = Y (1a), Nd (1b), Sm (1c), Dy (1d), Lu (1e)), in which the metal center is bonded to one C5Me4SiMe3 ligand in a normal η5-form and to the other in a μ-η5:η1-chelate fashion through metalation of a methyl group of the SiMe3 substituent. Hydrogenolysis of 1a−e in toluene at room temperature afforded the corresponding metallocene terminal hydride complexes [(C5Me4SiMe3)2LnH(THF)] (Ln = Y (2a), Nd (2b), Sm (2c), Dy (2d), Lu (2e)). Complexes 2a,d,e were isolated and structurally characterized by X-ray analysis, whereas 2b,c, which possess larger metal ions, existed only in solution in the presence of H2. The reaction of the yttrium hydride complex 2a with 1 equiv of p-methoxyphenylisocyanide yielded the ethylene diamido complex [(C5Me4SiMe3)2YN(Ar)(CH═)]2 (Ar = C6H4-O...

オレフィン部位に加えて, 累積する二重結合やシクロプロパン環のような反応基をもった化合物 (アレン・メチレンシクロプロパン) は, 通常のオレフィンに比べて高い反応性を示し, 新しい単量体として非常に興味深い. 本研究では, このようなポテンシャルの高い単量体の遷移金属触媒重合について検討した. メチレンシクロプロパンは, パラジウム錯体触媒により開環重合することがわかった. 得られたポリマーはexo-メチレン基を有しており, 頭尾結合は非常によく制御されていた. ニッケル錯体を用いた場合には, 重合はシクロプロパンの開環をまったく伴わずに進行し, シクロプロピリデン基を側鎖に有するポリマーを与えた. パラジウム錯体はメチレンシクロプロパンと一酸化炭素との共重合にも有効であり, エノン構造を有する交互共重合体を与えた. 生長末端への単量体の挿入段階がポリマー構造制御の鍵であることが示唆された. アリールアレンとRhH (PPh3) 4との反応で得られるアリルロジウム錯体は常温・常圧で一酸化炭素とアリールアレン・アルキルアレンとのリビング交互共重合を起こした. 得られるポリケトンはエノン構造を有しており, 位置選択性や二重結合における配置は非常によく制御されていた. アリルロジウム錯体はアゾベンゼン構造を有するアレンと一酸化炭素との交互共重合にも有効であり, 液晶性ポリケトンが得られた.

1, 3-シクロヘキサジエン (CHD) の重合に対し, ビスアリルニッケルプロミド (ANiBr) とメチルアルミノキサン (MAO) からなる2成分触媒が, 極めて高活性であることを見いだした. 特に, oジクロロベンゼンおよびシクロヘキサン中では, 室温で重合はいずれも瞬時に完了し, 88～96%の高取率で白色粉末状のポリマーが得られた. 種々のホウ素化合物にも顕著な共触媒効果があり, 例えば, ANiBrに対しLiB (C6F5) 4を0.2当量加えただけで, 90%を超える重合収率が達成された. 単離したNi錯体との比較から, カチオン性のアリルニッケルが真の重合活性種と推定される. 生成したポリ (CHD) は有機溶媒に不溶不融であったが, 共重合体のNMR解析の結果, 1, 4一結合のみで構成されていることが明らかとなった. さらに, COMPASS Force Fieldを使った分子動力学計算により, シスーシンジオタクチック構造のみが, ポリ (CHD) の実測X線回折パタンを再現できることがわかった. ANiBr以外のNi錯体を検討した結果, 配位子の立体障害がCHDの重合速度, 収率に強い影響を与えることがわかった. 一方, 生成ポリマーの位置/立体構造に大きな変化は認められなかった. 続いて, 1, 3-ブタジエン (BD) との共重合についても詳しく検討した. CHD-BD共重合体は, 30mol%のBD単位が含まれていても結晶性を示し, BD導入量を変えることで, 融点, ガラス転移点が制御できた. また, 1) 共重合反応性はCHDがBDよりも高い, 2) CHD単位増加に連動してBD単位のトランス/シス比が増加する, ことも明らかにした.

Substitued 1,2-dienes such as cyclohexylalene (3-phenylpropyl)allene, 1,1-dimethylallene, 1-methyl-1-phenylallene, 4(t-butyl)phenoxyallene and (4-allenyloxy)azobenzene underwent alternating copolymerization with carbon monoxide (at approximately 1.05 atm) in the presence of a catalytic amount of Rh-complex, Rh[n 3 -CH(Ar)C{C(=CHAr)CH 2 C(=CHAr)-CH 2 CH 2 -CH=CHAr}CH 2 ](PPh 3 ) 2 (A, AR=C 6 H 4 OMe-p), to produce unsaturated polyketones {-CO-C(=CRR')-CH 2 -} n (R,R'=H, cyclo-C 6 H 11 ;H, (CH 2 ) 3 Ph; Me, Me; Me, Ph; H, OC 6 H 4 -t-Bu-4;H, OC 6 H 4 -N=N-C 6 H 5 ). NMR spectra indicated that the polymers are mainly composed of the repeating units formed via insertion of 2,3-bond of allene monomer and carbon monoxide into the polymer end. The polyketone prepared from 4-(allenyloxy)azobenzene and carbon monoxide was not fully characterized by NMR due to its low solubility in organic solvents. Molecular weights Mn (determined by GPC, based on polystyrene standards) of the five soluble polymers range from 7 200 to 27 700. Plotting molecular weights of the polyketones during polymerization showed a significant difference in the reaction rates depending on the allene monomers; the polymerization rate decreases in the order 1,1-dimenthylalene>phenylallene>cyclohexylallene. Copolymerization of mixtures of 4-(allenyloxy)azobenzene and 4-(t-butyl)phenoxyallene with carbon monoxide afforded soluble random copolyketones with Mn = 11 100-15 400.

Copolymerization of (4-hexylphenyl)allene and of (4-dodecylphenyl)allene with carbon monoxide (1 atm) catalyzed by Rh[η3-CH(Ar′)C{C(CHAr′)CH2C (CHAr′)CH2CH2CHCHAr′}CH2](PPh3)2 (A; Ar′ = C6H4OMe-p) gives the corresponding polyketones: I-[—CO—C(CHAr)—CH2—]n [1: Ar = C6H4C6H13-p, 2 : Ar = C6H4C12H25-p; I = CH2C(CHAr′)C(CHAr′)CH2C(CHAr′)CH2CH2CHCHAr′]. Molecular weights of the polyketone prepared from (4-hexylphenyl)allene and CO are similar to the calculated from the monomer to initiator ratios until the molecular weight reaches to 45,000, indicating the living polymerization. Melting points of the polyketones I-[—CO—C(CHC6H4R-p)—CH2—]n (n = ca. 100) increase in the order R = C12H25 < C6H13 < C4H9 < CH3 < H. Block and random copolymerization of phenylallene and (4-alkylphenyl)allene with carbon monoxide gives the new copoly- ketones. The polymerization of a mixture of (4-methylphenyl)allene and smaller amounts of bis(allenyl)benzene under CO afforded the polyketone with a crosslinked structure. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 1505–1511, 2000

α,ω-Diols with long carbon chains, HO(CH2)12O(CH2)12OH, HO(CH2)12O(CH2)12O(CH2)12OH, and HO(CH2)mOC6H4O(CH2)mOH (m =6, 12), reacted with diisocyanates to give the corresponding poly(urethane)s in 87–99% yields. Structure of the polyurethane was confirmed by 1H and 13C NMR spectroscopy. IR absorbance due to ν(C=O) vibration of the polymers obtained from hexamethylene diisocyanate was observed at lower wavenumber than that of the polymers from aromatic diisocyanates. Melting point of the poly(urethane)s decreased with increase in flexibility of the polymer chain.

NaH promoted coupling reaction of HO(CH2)12O–TBDMS (1, TBDMS=SiMe2(t-Bu)) and Br(CH2)12O–TBDMS (2) followed by deprotection of the organosilyl groups affords HO(CH2)12O(CH2)12OH (5). 1,12-Dodecanediol reacts with an excess amount of 2 in the presence of NaH to give TBDMS–O(CH2)12O(CH2)12O(CH2)12O–TBDMS (6) which is turned into HO(CH2)12O(CH2)12O(CH2)12OH (7) by removal of the protecting groups. Similar 1 : 2 condensation of hydroquinone with 2 and with Br(CH2)6O–TBDMS (3) leads to formation of the corresponding α,ω-diols, HO(CH2)12OC6H4O(CH2)12OH (9) and HO(CH2)6OC6H4O(CH2)6OH (11), respectively. The four new long α,ω-diols are isolated and characterized by means of IR and NMR spectroscopy as well as elemental analyses. Polyaddition reactions of 5, 7, 9, and 11 to 1,3-bis(isocyanatomethyl)benzene and 1,1′-methylenebis[4-isocyanatobenzene] give the corresponding poly(urethane)s in high yields. The obtained polymers, which were characterized by IR and NMR spectroscopy, have molecular weights over 20000 as d...

Progress for two or three decades in Pd complexpromoted alternating copolymerization of alkenes with carbon monoxide has enabled many polyketones to be synthesized with regulated structures and molecular weights.

Quaternary ammonium- and amino-functionalized silica catalysts have been prepared for the selective synthesis of cyclic sulfites from epoxides and sulfur dioxide, demonstrating the effects of immobilizing the homogeneous catalysts on silica. The cycloaddition of sulfur dioxide to various epoxides was conducted under solvent-free conditions at 100 °C. The quaternary ammonium- and amino-functionalized silica catalysts produced cyclic sulfites in high yields (79-96 %) that are comparable to those produced by the homogeneous catalysts. The functionalized silica catalysts could be separated from the product solution by filtration, thereby avoiding the catalytic decomposition of the cyclic sulfite products upon distillation of the product solution. Heterogenization of a homogeneous catalyst by immobilization can, therefore, improve the efficiency of the purification of crude reaction products. Despite a decrease in catalytic activity after each recycling step, the heterogeneous pyridine-functionalized silica catalyst provided high yields after as many as five recycling processes.

Various substituted nitroaromatics were successfully hydrogenated to the corresponding N-aryl hydroxylamines in excellent yields (up to 99%) using supported platinum catalysts such as Pt/SiO2 under a hydrogen atmosphere (1 bar) at room temperature. The key to the fast and highly selective formation of hydroxylamines is the addition of small amounts of amines such as triethylamine and dimethyl sulfoxide; amines promote the conversion of nitroaromatics, while dimethyl sulfoxide inhibits further hydrogenation of hydroxylamines to anilines. The promotive effect depends on which type of amine and primary amine was most effective. The hydrogenation efficiently proceeded in common organic solvents, including isopropanol, diethyl ether, and acetone. This methodology should extend the application range of conventional solid catalysts to fine chemicals synthesis.

Various substituted nitroaromatics were successfully hydrogenated to the corresponding N-aryl hydroxylamines in excellent yields (up to 99%) using supported platinum catalysts such as Pt/SiO2 under a hydrogen atmosphere (1 bar) at room temperature. The key to the fast and highly selective formation of hydroxylamines is the addition of small amounts of amines such as triethylamine and dimethyl sulfoxide; amines promote the conversion of nitroaromatics, while dimethyl sulfoxide inhibits further hydrogenation of hydroxylamines to anilines. The promotive effect depends on which type of amine and primary amine was most effective. The hydrogenation efficiently proceeded in common organic solvents, including isopropanol, diethyl ether, and acetone. This methodology should extend the application range of conventional solid catalysts to fine chemicals synthesis.