原子转移自由基聚合接枝改性木质素

木质素是仅次于纤维素的第二大生物质资源, 是自然界中唯一的可再生芳香族化合物资源。长久以来, 木质素的难以充分利用是掣肘生物化工产业的一个重大问题。近年来, 原子转移自由基聚合接枝改性成为木质素高值化利用的一个重要方法, 可制备获得不同结构、性能各异的木质素接枝改性材料。本文从单体种类、催化剂、材料的结构与性能等方面, 介绍了原子转移自由基聚合接枝改性木质素的研究进展, 并对该领域的发展前景与挑战进行了探讨。     

基于ATRP接枝改性木质素的研究进展

木质素是仅次于纤维素的第二大可再生生物质资源,也是一种环境友好的有机高分子材料.原子转移自由基聚合(atom transfer radical polymerization,ATRP)是近年来迅速发展并有着重要应用价值的一种"活性"/可控自由基聚合技术.本文结合本课题组目前的研究工作和近几年的相关报道,简述了ATRP在木质素接枝共聚方面的最新研究进展.综述了采用ATRP对木质素接枝共聚改性的方法,并采用该方法在木质素表面接枝不同功能性单体,赋予木质素表面温敏性、离子响应性、气体开关和基因传递等多种特殊性能的研究概况.最后介绍了AGET ATRP(activators generated by electron transfer ATRP)在木质素接枝共聚反应中的应用.     

生物医用材料表面光引发活性接枝聚合研究新进展

表面接枝聚合改性已经成为提升生物医用材料性能的最重要方法之一.参比其他活性接枝聚合方法,光引发活性接枝聚合因其独特的优势已被越来越广泛地应用于生物医用材料表面改性.根据光引发剂的类型,目前应用最多的光引发活性接枝聚合的引发体系主要有3种:光引发-转移-终止剂介导的聚合引发体系、二苯甲酮及其衍生物引发体系、硫杂蒽酮类引发...     

表面光接枝聚合反应新进展

表面性能对高分子材料应用至关重要,但多数聚烯烃材料表面惰性,需对表面进行改性或功能化．紫外光引发表面光接枝聚合反应具有诸多优势,因而获得广泛应用．作者以本实验室近年的研究为基础,结合这一领域国际上的部分重要研究成果,概述了实施表面光接枝聚合反应的一些新方法：控制,活性表面光接枝聚合、自引发光接枝聚合、暗区表面光接枝聚合、表面光接枝-交联聚合以及表面小分子光化学反应等．     

聚乳酸接枝改性纳米生物玻璃/PLGA复合材料的制备、表面性质及生物活性

以丙交酯开环聚合原位接枝改性的纳米生物玻璃(PLLA-g-BG)与聚丙交酯-乙交酯(PLGA)复合材料为研究对象, 采用TGA, ESEM和EDX分析其接枝率, 粒子分散性和表面元素分布, 通过将兔成骨细胞种植于材料膜表面进行体外培养, 采用荧光染色法、NIH Image J图像分析软件、MTT法和流式细胞术等手段检测细胞在材料表面的平均黏附数量、扩展面积比、增殖能力和细胞周期的变化, 综合评价新型改性纳米复合材料的生物相容性和生物活性. 结果表明, 聚乳酸表面接枝改性可明显改善纳米生物玻璃粒子的团聚; PLGA中掺入一定比例的改性PLLA-g-BG可明显促进兔成骨细胞的黏附、扩展与增殖; 改性纳米生物玻璃的应用可提高生物可降解聚酯材料的生物相容性和生物活性.     

木质素磺酸镁接枝丙烯酰胺的影响因素

天然高分子化合物木质素是木材水解工业和造纸工业的副产物。早期人们在研究纤维素同甲基丙烯酸甲酯、丙烯腈的接枝反应中时发现了木质素的接枝反应活性[1],Meisterh和Patil[2]则实现了将—CONH2接枝于木质素的设想,雷中方[3]等研究了木质素同具有较好吸附能力的—CONH2的接枝改性,并讨论了改性产物的水处理性能,他们所用的木质素是采用酸析法从碱法草浆黑液中提取的。本文以酸法制浆的红液 木素磺酸镁为原料,合成了木质素 丙烯酸胺接枝共聚物,并对接枝聚合过程中的引发体系、引发剂浓度、反应温度、木素与单体用量比、固液比等影…     

聚丙烯表面接枝改性络合金的研究

探索了一种通过聚丙烯(PP)改性来络合金金属的新途径.首先在PP膜上经紫外光引发实施丙烯酸的接枝聚合反应,得到表面带—COOH基团的改性PP膜;再用负离子开环聚合的方法在改性后的PP膜上接枝尼龙6.上述处理后的膜表面含有大量O、N的功能基团,故可将此膜用于对溶液中金的络合.利用ATR、SEM、XPS等技术对改性及络合进行了表征.实验结果表明,此方法制备的PP膜对金的络合效果明显.     

单电子转移活性自由基聚合特点及应用

近十年来,单电子转移活性自由基聚合(SET-LRP)技术作为一种新的活性聚合方法,在高分子聚合及改性研究领域得到广泛应用。本文首先通过与其它活性聚合方法比较,对SET-LRP技术具有的一些明显的优点及缺点进行了分析;然后对近年来利用SET-LRP技术,制备多嵌段共聚物、星型及支化聚合物、环状聚合物的典型研究进行了报道,最后综述了SET-LRP技术在固体材料表面改性方面的应用,如在无机材料表面进行高分子合成,以及在聚合物胶乳表面进行有机小分子接枝等。     

表面光接枝原理,方法及应用前景

介绍了表面光接枝的原理,方法和应用前景,表面光接枝主要是用芳酮引发有机材料产生表面自由基,从而引发单体聚合生成表面接枝链。实施方法有气相法,液相法和连续液相法。表面光接枝应用领域广泛,可用于聚合材料的表面改性以及表面功能化。     

木质素接枝偶氮苯液晶聚合物的合成与表征及光响应性能研究

以天然高分子木质素为原料,通过亲核取代反应将木质素改性成为大分子引发剂,引发偶氮苯单体的原子转移自由基聚合(ATRP),得到一系列木质素基光响应聚合物.接枝后的木质素的热稳定性明显改善,且平均接枝率达到72.8%时才能表现出液晶行为.小角X射线散射和偏光显微镜的结果表明所形成的液晶相为近晶C型,层间距为3.21nm.在此基础上,用紫外-可见吸收光谱(UV-Vis)对木质素基液晶聚合物的光响应性进行研究,发现溶液中的光响应性比膜状态的光响应速率快.在紫外光的辐照下,木质素基液晶聚合物表现出快速的光致液晶-各向同性相变行为.     

二氧化碳和丙烯直接合成甲基丙烯酸的NiPMo/TiO2催化剂的研究

用溶胶-凝胶法以磷钼酸(MPA)的镍盐溶液水解钛酸四丁酯制备了NiPMo/TiO2催化剂.使用ICP、 XRD、 TG-DTA、 IR、 TPD-MS和微反应技术研究了催化剂的化学组成、热稳定性、化学吸附性质和催化反应性能.杂多钼酸盐与TiO2通过O2-在TiO2表面发生了键合.在623 K下,杂多阴离子仍保持原有的Keggin结构.CO2在Lewis酸位Ni(Ⅱ)和Lewis碱位Ni-O-Mo的桥氧协同作用下生成CO2卧式吸附态Ni(Ⅱ)←O-(CO)←(O--Ni).丙烯有多种吸附态在催化剂上吸附.在563 K、 1 MPa和空速1500 h-1的反应条件下,丙烯的摩尔转化率为3.2%,产物MAA选择性为95%.     

Toward new camptothecins. Part 6: Synthesis of crucial ketones and their use in Friedländer reaction

In the context of the preparation of camptothecin and luotonin A analogs, the synthesis of some key keto-precursors and their use in Friedländer condensation are described. This paper also focuses on the stability of these keto intermediates and emphasizes the major differences between indolizinones and pyrroloquinazolinones series. Noteworthy is also the report of some original structures isolated as by-products of some experiments.     

CoFe2O4自形成磁性液体场致结构化对磁化的影响

The Langevin paramagnetic theory can’t describe the relation between magnetization of ferrofluids and applied magnetic field. The structuralization of ferrofluids, which is considered the main influence factor of the magnetization, is regarded. The part of magnetization works is deposited when the structure is forming. This action influences the magnetization of ferrofluids directly or indirectly. On the base of the “compressing” model, the Langevin function that usually describes the magnetization of ferrofluid is modified, and a well-fitted curve is obtained. An equation of the relation between the equivalent volume fraction after being “compressed” and the intensity of magnetic field is discovered, which approximately describes the process of magnetization. The relation between the approximate initial susceptibility and the volume fraction can be obtained from modified formula.     

KMnO4-mediated oxidative CN bond cleavage of tertiary amines: Synthesis of amides and sulfonamides

KMnO₄-mediated oxidative CN bond cleavage of tertiary amines producing secondary amine was introduced, which was trapped by electrophiles (acyl chloride and sulfonyl chloride) to form amides and sulfonamides. The reaction could take place at mild condition, tolerating a wide range of function groups and affording products in moderate to excellent yields.     

Highly regioselective Buchwald–Hartwig amination at C-2 of 2,4-dichloropyridine enabling a novel approach to 2,4-bisanilinopyridine (BAPyd) libraries

The highly regioselective Buchwald–Hartwig amination at C-2 of the cheap and readily accessible reagent, 2,4-dichloropyridine with a range of anilines and heterocyclic amines is described. This new methodology is robust and provides a facile access to 4-chloro-N-phenylpyridin-2-amines on 0.25 mol scale. These intermediates undergo a further Buchwald–Hartwig amination at higher temperature to enable rapid exploration of the chemical space at C-4 and to provide a library of 2,4-bisaminopyridines.     

Chemistry of heterocyclic compounds at the A. E. Favorsky Irkutsk Institute of Chemistry, Siberian Branch of the Russian Academy of Sciences, over 50 years (Review)

The review contains a concise historical account and information on the most significant researches undertaken by the staff at the A. E. Favorsky Irkutsk Institute of Chemistry, Siberian Branch of the Russian Academy of Sciences on the Chemistry of Heterocyclic Compounds. Dedicated to Academician of the Russian Academy of Sciences B. A. Trofimov on his 70th jubilee. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 10, pp. 1443–1502, October, 2008.     

Sulfur-directed metal-free and regiospecific methyl C(sp3)–H imidation of thioanisoles

Regiospecific and direct imidation of the methyl C(sp³)–H bond of thioanisoles is realized under mild and metal-free conditions with N-fluorobis(benzenesulfonyl)imide as an oxidant and nitrogen source. Proposed mechanism suggests that thionium ion intermediates and a Pummerer-type reaction are involved. The imidation has advantages such as high step-economy, excellent functionality tolerance, and regiospecificity, giving structurally diverse imidation products.     

Selective syntheses of 2H-1,3-oxazines and 1H-pyrrol-3(2H)-ones via temperature-dependent Rh(II)-carbenoid-mediated 2H-azirine-ring expansion

The Rh(II)-catalyzed reaction of 2-carbonyl-substituted 2H-azirines with ethyl 2-cyano-2-diazoacetate or 2-diazo-3,3,3-trifluoropropionate provides an easy access to 2H-1,3-oxazines and 1H-pyrrol-3(2H)-ones. These compounds can be selectively prepared from the same starting material using temperature as the only varied parameter. The 2-azabuta-1,3-diene intermediate, a common precursor for both heterocyclic products, isomerizes into 2H-1,3-oxazine under kinetic control, while 1H-pyrrol-3(2H)-one is the sole product of the reaction at elevated temperatures. According to DFT-calculations a one-atom oxazine ring contraction involving ring-opening to a 2-azabuta-1,3-diene intermediate, followed by a 1,5- and 1,2-prototropic shift leads to the consecutive formation of imidoylketene and azomethine ylide, which then further undergo cyclization to the pyrrole derivative.     

Synthesis of 1-benzyloxypyrazin-2(1H)-one derivatives

Different approaches for the synthesis of 1-benzyloxypyrazin-2(1H)-one derivatives from simple amino acids have been investigated. A library of 33 precursors for the preparation of N-hydroxy pyrazinones was obtained in moderate to good yields.