结晶3,4-聚异戊二烯的合成

<正> 非结晶的3,4-聚异戊二烯的合成已有一些报道,本文则采用合铁的三元催化体系:三乙酰基丙酮铁-含氮给电子试剂-三异丁基铝,可使异成二烯聚合得到高3,4-链节含量,高分子量以及高熔点的结晶聚合物。 1.试剂及聚合反应 异戊二烯为聚合级产品,用前经常压蒸馏除去阻聚剂后,用活性氧化铝浸泡48小时     

敏化的3,4-聚异戊二烯-2,6-双(4’-叠氮苄叉)环己酮体系的光交联反应研究

本文对二苯甲酮敏化前后3,4-聚异戊二烯-2,6-双(4′-叠氮苄叉)环己酮体系的光交联反应进行了研究。证明了该体系的光交联反应以双氮烯和被二苯甲酮活化的大分子的外双键加成为主。     

聚-3,4异戊二烯的x-射线研究

对聚异戊二烯的研究一直很活跃。含3,4-链节70%左右的晶性聚3,4-异戊二烯(3,4-PⅠ),是适用于室温下较理想的吸振材料,其晶体结构尚未见报导。     

氢醌对3,4-聚异戊二烯-2,6-双(4’-叠氮苄叉)环己酮体系的光交联反应的影响

关于聚二烯烃-双叠氮型感光性高分子的光交联反应机理,目前有Hepher的自由基机理和的非自由基机理之争。为了对该体系的光交联反应有更加本质的了解,我们对含氢醌的该感光性高分子进行光照,在对反应产物的分析中发现有苯醌和2,6-双(4’-氨基苄叉)环己酮存在,证明氢醌对活性双氮烯有猝灭作用。通过对光交     

3,4-聚异戊二烯的磺化反应及其离聚体的结构研究

本工作合成了磺化的3,4-聚异戊二烯及其离子聚合体,IR和NMR谱图证明对3,4-聚异戊二烯的磺化反应是成功的,并且磺酸基团主要与3,4-链节的侧基双键发生反应。WAXD对磺化3,4-聚异戊二烯及其离聚体的研究表明,磺化度的增加使离聚体的结晶能力降低,SAXS结果表明,在离子含量为3.29mol％的离聚体中,未观察到离子簇聚集,只观察到多重离子对的散射。     

氢醌对3,4-聚异戊二烯-2,6-双(4′-叠氮苄叉)环己酮体系的光交联反应的影响

关于聚二烯烃-双叠氮型感光性高分子的光交联反应机理,目前有Hepher的自由基机理和的非自由基机理之争。为了对该体系的光交联反应有更加本质的了解,我们对含氢醌的该感光性高分子进行光照,在对反应产物的分析中发现有苯醌和2,6-双(4′-氨基苄叉)环己酮存在,证明氢醌对活性双氮烯有猝灭作用。     

3,4-聚异戊二烯的合成及其结构与性能的表征

近二十多年来,在异戊二烯的络合催化聚合中,由Ni、Co、Ti及稀土等过渡金属元素络合物组成的催化体系,研究报道得很多,有些已投入工业生产。但由最常见的过渡金属元素铁络合物组成的催化体系,对异成二烯的聚合却不多见。     

~(13)C-NMR研究3,4-聚异戊二烯的序列分布

Fe(acac)_3-Phen-AlEt_3 催化体系可使异戊二烯聚合成以 3,4-链节为主具有一定结晶性能的聚异戊二烯。本文对该聚合物的~(13)C-NMR 谱进行了全分析,研究了序列分布、微观结构。结果表明不同方法求得的微观结构含量很好地一致,说明对~(13)C-NMR 谱峰归属的正确性。并指出顺-1,4/3,4-序列中存在着头-头,尾-尾的连接方式,3,4-嵌段链节不足够长及存在反节可能是结晶度不太高的主要原因。     

稀土催聚顺-1,4-聚异戊二烯的表征

稀土催化聚合的顺-1,4-聚异戊二烯(Ln—PIR)的顺式含量比天然橡胶(NR)略低,其长链分子无支化.Ln—PIR生胶本体结晶的Avrami指数n值高达7以至8.与Ti-PIR及NR相同,松弛模量依赖于缠结链段的分子量.屈服过程的开始与链的解缠结的开始相当,两个过程的活化能各约为8KJ/mol.,不论是屈服或缠结的出现,用屈服强度法与应力松弛法这两种独立方法所测得的临界分子量Mc值等于(5.4±0.2)×104,此值又与用折合屈服强度法所求得的Mc值相当.     

高反式1,4-聚异戊二烯合成的新方法

<正> 反1,4-链节含量接近100％的聚异戊二烯(TPI)具有天然杜仲胶或古塔胶的结构和性能,结晶熔点60—65℃,被认为是作为形状记忆功能材料,如医用矫形材料、各种温敏变形材料的最理想聚合物。关于TPI的合成路线,国外报道主要有V体系(VCl_3/AlEt_3及其负载改性型)和V-Ti混合体系(VCl_3/β-TiCl_3/AlEt_3和Ti(OR)_4/     

Formation of Reaction Mixture in the Course of Preparation of cis-1,4-Polyisoprene in the Turbulent Mode

The effect of a piperylene modification of Ziegler-Natta catalytic systems was studied by sedimentation analysis in the gravity field. The rate of isoprene polymerization was analyzed as influenced by additional crushing of catalyst particles and formation of uniform reaction mixture in mixing of the initial components in a tubular turbulent prereactor of the diffuser-confuser design.     

The Haloform Reaction in the Presence of Cyclodextrins

Cyclodextrins act as inverse phase transfer catalystsin the oxidation of methyl ketones by hypochloride(the haloform reaction). The reaction is affected by thechoice and the amount of cyclodextrin. The reactionproceeds under mild reaction conditions and itprovides only the corresponding carboxylic acid asreaction product. No organic solvent is required.     

Photosynthetic Antenna–Reaction Center Mimicry by Using Boron Dipyrromethene Sensitizers

Various molecular and supramolecular systems have been synthesized and characterized recently to mimic the functions of photosynthesis, in which solar energy conversion is achieved. Artificial photosynthesis consists of light‐harvesting and charge‐separation processes together with catalytic units of water oxidation and reduction. Among the organic molecules, derivatives of BF₂‐chelated dipyrromethene (BODIPY), “porphyrin’s little sister”, have been widely used in constructing these artificial photosynthetic models due to their unique properties. In these photosynthetic models, BODIPYs act as not only excellent antenna molecules, but also as electron‐donor and ‐acceptor molecules in both the covalently linked molecular and supramolecular systems formed by axial coordination, hydrogen bonding, or crown ether complexation. The relationships between the structures and photochemical reactivities of these novel molecular and supramolecular systems are discussed in relation to the efficiency of charge separation and charge recombination. Femto‐ and nanosecond transient absorption and photoelectrochemical techniques have been employed in these studies to give clear evidence for the occurrence of energy‐ and electron‐transfer reactions and to determine their rates and efficiencies.     

Synthesis of 3,4-Dihydroquinazolines in the Reaction of o-Aminophenyldiphenylcarbinol with Nitriles

The reaction of o-aminophenyldiphenylcarbinol with nitriles of various structure in the presence of perchloric acid has been investigated. Optimal conditions have been developed for the synthesis of 3,4-dihydroquinazolinium perchlorates, from which the corresponding 3,4-dihydroquinazolines are obtained by treatment with bases. Certain compounds with an active methylene group bound directly to the heterocycle are able to exist in tautomeric forms with migration of the multiple bond into an exocyclic position.     

Reaction of 3,4-dichlorocaranes with nucleophilic reagents

Conclusions 3,4-Dichlorocarane when subjected to acetolysis undergoes rearrangements that are characteristic for the carane system: ⁴-carene-p-1, 5-menthadiene, caraneethylbicyclohexane, and caranemethyl-isopropenylbicyclohexane.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 2, pp. 388–393, February, 1972.     

Thermal Decomposition Reaction of Ferrocene in the Presence of Oxalic Acid

Thermal decomposition of ferrocene [(C₅H₅)₂Fe] in the presence of oxalic acid [(COOH)₂·2H₂O] samples—prepared by grinding the mixtures of ferrocene and oxalic acid at different weight ratios—is reported in this work. It presents a mathematical analysis of nonisothermal thermogravimetric data using multiheating rates to estimate reaction kinetics as well as thermodynamic parameters. Model‐free (integral isoconversional) methods are employed to analyze thermogravimetric data. The most probable reaction mechanisms for thermal reactions have been identified. Based on the values of the activation energy E_α* and reaction rate A_α for different steps of decomposition, the values of ΔS *, ΔH *, and ΔG * for the formation of activated complex from the precursor are estimated. Besides, this work has proposed reaction pathways indicating the formation of hematite (α‐Fe₂O₃) as the solid end‐product of thermal decomposition of the samples.     

Reaction of Organylchlorosilanes with Dimethyl Sulfoxide in the Presence of Octamethyltrisiloxane

Dichloro(methyl)(vinyl)silane reacts with DMSO in the presence of octamethyltrisiloxane to form cyclooligomethyl(vinyl)siloxanes(MeViSiO) _n (n = 3-6). The reaction involves disproportionation of octamethyltrisiloxane into hexamethyldisiloxane and decamethyltetrasiloxane. Along with the latter two products, insertion products of methyl vinyl silanone into both permethyloligosiloxanes were identified. Alkyltrichlorosilanes RSiCl₃ (R = Me, Et) react with DMSO in the presence of octamethyltrisiloxane to form cyclic oligoalkyltrichlorosiloxanes (RClSiO) _m (m = 3-6).     

Reaction of Some Terpenoids with Malononitrile in the Presence of Hydrotalcite

α-Ionone and 5,5,8-trimethyl-3,7-nonadien-2-one react with malononitrile in the presence of specially prepared hydrotalcite to afford the corresponding Knoevenagel condensation products with high yield and selectivity.__________Translated from Zhurnal Organicheskoi Khimii, Vol. 41, No. 6, 2005, pp. 859–863.Original Russian Text Copyright © 2005 by Khomenko, Volcho, Toktarev, Echevskii, Salakhutdinov, Barkhash.