再活化链式聚合

基于传统的链式聚合和逐步聚合二种高分子链增长过程,提出了再活化链式聚合。按此聚合机理,高分子的链增长是通过将一个非活性或睡眠状态的链(Mm)重新活化为活性种(Mm*),活性种再和一个单体(M)反应,生成一个较大分子量的休眠产物(Mm 1)来实现的。再活化链式聚合主要例子包括苯胺和或许其它芳香族单体的氧化聚合,活性自由基聚合,以及核酸和蛋白质合成中的生物聚合。     

正丁基锂四氢呋喃引发α-甲基苯乙烯阴离子平衡聚合动力学及反应机理研究

本文研究了以正丁基锂为引发剂,四氢呋喃为添加剂,环己烷为溶剂中的α-甲基苯乙烯阴离子平衡聚合动力学。讨论了体系中的反应活性种;提出了聚合机理;得到了聚合温度为20℃时的平衡单体浓度与活性种速率常数及添加剂浓度之间的关系式。     

正丁基锂/四氢呋喃引发丁二烯阴离子聚合动力学和活性种的研究

本文测定了正丁基锂/四氢呋喃(THF)引发丁二烯聚合反应速度和聚合物微观结构;讨论了体系的活性种,得到了聚合反应速度与单体浓度的关系:引发期为二级反应,增长期为一级反应。估算了活性种的活性;建立了结构动力学式并由此分析了不同活性种对聚合速度和聚合物结构的贡献。     

新引发体系引发MMA活性自由基聚合

近年来 ,关于活性自由基聚合的研究极为活跃 ,已经发现了多种基于增长链自由基被可逆钝化形成休眠种的活性自由基聚合方法[1,2 ] .它们主要包括引发转移终止剂 ( Iniferter) ,稳定自由基聚合( SFRP) ,原子转移自由基聚合 ( ATRP) ,可逆加成 -断链链转移聚合 ( RAFT)等 .其中 ATRP因其具有可聚合单体多 ,反应条件相对缓和等优点而成为该领域的研究热点 [3～ 5] .ATRP活性自由基聚合的实现主要是在过渡金属催化剂的作用下 ,通过循环往复的碳 -卤键的活化、加成、碳 -卤键的再形成而得到最终活性的聚合物 ,引发体系由引发剂、过渡金属…     

苯乙烯间规聚合催化剂进展

综述了苯乙烯间规聚合主催化剂的研究和开发状况。主要介绍茂、茚、多元稠合环，氟和非茂钛等较高活性催化剂的催化特性，从取代基的电子效应和空间效应以及活性种稳定性等方面阐述了不同催化剂的聚合活性差异。     

红外光谱法研究苯乙烯原子转移自由基聚合反应动力学

利用红外光谱法测定反应转化率研究原子转移自由基聚合反应动力学。在环己酮溶液中,以卤代烃为引发剂,过渡金属卤化物与配位剂２,２‘－联吡啶为催化体系,进行了苯乙烯聚合。分别就反应温度,反应物浓度和引发体系对苯乙烯聚合速率的影响进行了动力学测定,证实了原子转移自由基聚合具有活性聚合的特征,同时计算并讨论了苯乙烯原子转移自由基聚合反应的动力学数据。     

α-甲基苯乙烯与苯乙烯阴离子共聚合研究——Ⅰ.共聚反应动力学及机理

本文研究了以正丁基锂为引发剂、四氢呋喃为极性添加剂、在环己烷中进行α-甲基苯乙烯与苯乙烯阴离子共聚合。通过共聚反应动力学的研究,提出了聚合机理,求得了两种单体通过不同聚合活性种增长反应及解聚反应的速度常数及活性种间的络合平衡常数。     

氧对n-BuLi/THF引发丁二烯苯乙烯共聚合的影响

研究了氧分子与活性种快速失活的定量关系 ,二代杂质对活性种及聚合物微观结构的影响 .从聚合动力学及聚合物相对分子质量等方面来测定氧分子快速杀死活性种数 ,并考察了体系中氧产生的偶联反应及其对丁苯共聚物物理机械性能、动态力学性能及耐磨性能的影响 .结果表明 :氧对n BuLi THF体系丁苯共聚合有不利影响 .     

1996年聚合物化学进展

１聚合反应１９９６年在聚合物合成方面的主要特征是在“ＴｒｅｎｄｓｉｎＰｏｌｙｍｅｒＣｈｅｍｉｓｔｒｙ１９９５”中所述的“活性”自由基聚合和过渡金属催化聚合技术的优化。运用“活性”自由基聚合技术，即基于活性和休眠链端的交替反应，能够合成广范围的嵌段共聚物结构。这个范畴内可以看到两个主要方向：一方面是增加对非期望副反应的了解以及动力学对优化反应的贡献；另一方面用可控的自由基聚合，从商业上易得的单体合成过去从未得到过的聚合物。有若干综述一［１］论证了以氮氧化合物为基础的有控自由基聚合的进展，如ＴＥＭＰ…     

自由基活性聚合及其最新进展

本文介绍了实现自由基活性聚合的动力学、热力学条件及可能的途径。在这些条件下自由基保持稳定的低浓度，增长链自由基与休眠种处于动力学平衡动态，可有效地控制聚合反应，使聚合反应具有聚合物分子量随反应时间、单体转化率成线性增长关系及所得聚合物分子量分布较窄的特征，并且在加入第二单体时可继续生成嵌段共聚物。     

聚合氯化铝形态分布、分析和控制研究进展

Al^3 发生水解和聚合反应,形成多种形态。关于其形态分布与结构,目前存在两种观点,即六元环连续分布模式和聚十三铝模式。形态分析的方法,主要有NMR法、吸光光度法等。影响形态分布的因素,主要有反应物浓度、碱化度、碱液加入速度、加碱方式、混合状况等。     

The Investigation of Oxygen Absorption over LaOF by Means of Raman Spectroscopy

ＴｈｅＩｎｖｅｓｔｉｇａｔｉｏｎｏｆＯｘｙｇｅｎＡｂｓｏｒｐｔｉｏｎｏｖｅｒＬａＯＦｂｙＭｅａｎｓｏｆＲａｍａｎＳｐｅｃｔｒｏｓｃｏｐｙＺＨＯＵｍＸｉａｏ－ｐｉｎｇ,ＣＨＡＯＺｉ－ｓｈｅｎｇ,ＷＡＮＧＳｈｕｉ－ｊｕＷＡＮＨｕｉ－ｌｉｎａｎｄＴｓａｉＫ...     

Methodological aspects about in vitro evaluation of antioxidant properties

Several of the most commonly used methods for in vitro determination of antioxidant capacity are reviewed in the present paper. The chemical principles of methods based either on biological oxidants (peroxyl radical, superoxide radical anion, hydrogen peroxide, hydroxyl radical, hypochlorous acid, singlet oxygen, nitric oxide radical, and peroxynitrite) or on non-biological assays (scavenging of 2,2′-azinobis-(3-ethylbenzothiazoline-6-sulphonate) radical cation (TEAC assay), scavenging of 2,2-diphenyl-1-picrylhydrazyl radical (DPPH assay), ferric reducing antioxidant power (FRAP assay), Folin-Ciocalteu reducing capacity (FC assay), electrochemical total reducing capacity) are outlined and critically discussed. The scope of application, the advantages and shortcomings of each method are also highlighted.     

New N‐Containing Sesquiterpenes from Hainan Marine Sponge Axinyssa sp.

Three new N‐containing sesquiterpenes, isofarnesyl formamide ( 2 ), 7‐formamido‐7,8‐dihydro‐α‐bisabolane ( 3 ), 4,5‐epi‐10‐isothiocyanatoisodauc‐6‐ene ( 4 ), and a known sesquiterpene, farnesyl formamide ( 1 ), were isolated from the Hainan marine sponge Axinyssa sp. The structures of the new compounds were elucidated by detailed analyses of their spectroscopic data and by comparison of their NMR data with those of structurally related compounds.     

Mechanism of sensitivity difference between trivalent inorganic As species [As(III)] and pentavalent species [As(V)] with inductively coupled plasma spectrometry

The pentavalent inorganic arsenic (As) species [As(V)] is found to be 4% more sensitive than the trivalent species [As(III)] with inductively coupled plasma mass spectrometry (ICP-MS) and inductively coupled plasma optical emission spectrometry (ICP-OES). Although there was no sensitivity difference between As(III) and As(V) with atomic absorption spectrometry (AAS), electrothermal atomization atomic absorption spectrometry (ETAAS), X-ray fluorescence (XRF), and neutron activation analysis (NAA). The calibration solutions of As(III) and As(V) were gravimetrically prepared from the unique mother standard solution of JCSS As standard solution which is certified by Japan Calibration Service System (JCSS). Since it is essential to use the calibration solutions with exactly the same concentration of As in order to accurately compare the sensitivities between As(III) and As(V). The mechanisms of this sensitivity difference between them were investigated by ICP-MS and ICP-OES, and it elucidated that the formation rates of hydride polyatomic species of As were definitively different between As(III) and As(V) species in the plasma. This phenomenon directly affected their sensitivities with ICP-MS and ICP-OES.     

Enhanced Conversion Efficiency Enabled by Species Migration in Direct Solar Energy Storage

Solar energy can be stored via either an indirect route in which electricity is involved as an intermediate step, or a direct route that utilizes photogenerated charge carriers for direct solar energy conversion. In this study, we investigate the fundamental difference between the direct and indirect routes in solar energy conversion using a new photoelectrochemical energy storage cell (PESC) as a model device. This PESC centers on a liquid junction that utilizes CH₃NH₃PbI₃ perovskite to drive photoelectrochemical reactions of Benzoquinone (BQ) and Ferrocene (Fc) redox species. The experimental studies show that the equilibrium redox potentials are 0.1 V and −0.78 V (vs Ag/AgNO₃) for Fc⁺/Fc and BQ/BQ^.−, respectively, which would produce a theoretical open-circuit voltage of 0.88 V for the storage device. The physics-based computational analysis shows a relatively flat reaction rate distribution in the electrode for the indirect route; however, in the direct route the photoelectrochemical reaction rate is critically affected by electron concentration due to strong light absorption of the perovskite material, which has been shown to vary by at least 10-fold in the transverse direction across the photoelectrode. The drastic variation of reaction rate in the photoelectrode creates an electric field that is 7.5 times stronger than the bulk electrolyte, which causes the photo-converted reaction product (i. e., BQ^.−) to drift away from the photoelectrode thereby creating a constant reaction driving force. As a result, it has been shown that the intrinsic solar to chemical conversion (ISTC) efficiency improves by ∼40 % for the direct route compared to the indirect route at 0.05 mA/cm².     

L-谷氨酸、甘氨酸二元、三元体系中铽(Ⅲ)、钙(Ⅱ)的化学形态研究

在模拟生理条件下 (37℃ ,I=0 .1 5mol/ L Na Cl) ,用 p H电位法研究了铽 ( )、钙 ( )与 L-谷氨酸、甘氨酸二元、三元体系。确定了体系存在的物种 ,测定了体系中配合物的稳定常数。讨论了上述二元、三元体系中铽 ( )、钙 ( )的物种分布特点。     

无机氧化剂在光催化氧化技术中的应用

光催化氧化作为高级氧化技术的一种在环境保护领域具有重要的应用前景。就目前而言,量子效率低、反应速度慢等缺点制约了光催化氧化的应用。投加无机氧化剂能够通过抑制空穴电子对的复合及产生其它氧化物种等方式强化光催化、提高光催化效率,推进光催化在实际中应用的进程。本文较详细地阐述了不同无机氧化剂强化光催化的机理、研究进展,并对无机氧化剂在光催化氧化中的应用前景进行展望。     

Homo- and hetero-bridged mixed-valence dinuclear complexes which contain the fragment ‘Rh(C6F5)3’

The reaction of the anionic mononuclear rhodium complex [Rh(C₆F₅)₃Cl(Hpz)]^t- (Hpz = pyrazole, C₃H₄N₂) with methoxo or acetylacetonate complexes of Rh or Ir led to the heterodinuclear anionic compounds [(C₆F₅)₃Rh(μ-Cl)(μ-pz)M(L₂)] [M = Rh, L₂ = cyclo-octa-1,5-diene, COD (1), tetrafluorobenzobarrelene, TFB (2) or (CO)₂ (4); M = Ir, L₂ = COD (3)]. The complex [Rh(C₆F₅)₃(Hbim)]⁻ (5) has been prepared by treating [Rh(C₆F₅)₃(acac)]⁻ with H₂bim (acac = acetylacetonate; H₂bim = 2,2′-biimidazole). Complex 5 also reacts with Rh or Ir methoxo, or with Pd acetylacetonate, complexes affording the heterodinuclear complexes [(C₆F₅)₃Rh(μ-bim)M(L₂)]⁻ [M = Rh, L₂ = COD (6) or TFB (7); M = Ir, L₂ = COD (8); M = Pd, L₂ = η³-C₃H₅ (9)]. With [Rh(acac)(CO)₂], complex 5 yields the tetranuclear complex [{(C₆F₅)₃Rh(μ-bim)Rh(CO)₂}₂]₂₋. Homodinuclear Rh^III derivatives [{Rh(C₆F₅)₃}₂(μ-L)₂]^·- [L₂ = OH, pz (11); OH, S^tBu (12); OH, SPh (13); bim (14)] have been obtained by substitution of one or both hydroxo groups of the dianion [{Rh(C₆F₅)₃(μ-OH)}₂]²⁻ by the corresponding ligands. The reaction of [Rh(C₆F₅)₃(Et₂O)_x] with [PdX₂(COD)] produces neutral heterodinuclear compounds [(C₆F₅)₃Rh(μ-X)₂Pd(COD)] [X = Cl (15); Br (16)]. The anionic complexes 1–14 have been isolated as the benzyltriphenylphosphonium (PBzPh₃⁺) salts.