超支化聚酯的改性及其结晶性能的研究

用十六酰氯和十八异氰酸酯分别对端羟基的超支化聚酯Boltorn^TMH20改性,可获得粉末状超支化低聚物,具有无定形“内核”及可结晶“外壳”的分子结构.实验结果表明,采用十八异氰酸酯改性的丙烯酸化超支化聚酯的熔点高于十六酰氯改性聚合物.     

超支化聚酯的合成与应用——纳米银粒子的制备与表征

超支化聚酯的合成与应用——纳米银粒子的制备与表征;超支化聚酯;纳米银;稳定剂;光还原     

超支化环糊精聚合物研究进展北大核心CSCD

超支化环糊精聚合物具备了超支化聚合物和环糊精各自的优点,两者的结合也为超支化环糊精聚合物带来了特殊的物理化学性质,现在已逐渐成为研究热点并在多个领域得到应用。本文简介了超支化聚合物和环糊精的基本特点,详细说明了超支化环糊精聚合物合成制备的方法,并从医药、生物学、新型材料、物化性质调控等方面介绍了超支化环糊精聚合物在近期的科研应用,最后总结了国内外发展情况,并结合现阶段研究,对超支化环糊精聚合物的发展前景进行展望。     

基于炔类单体的点击聚合制备超支化聚合物

超支化聚合物由于其独特的树枝状结构和物理化学性质,已经得到了广泛关注及应用.而基于炔类单体的点击聚合作为一类简单、高效的聚合反应已被广泛用于超支化聚合物的制备.本文对近5年利用叠氮-炔和巯基-炔点击聚合制备超支化聚合物的工作进行了简要综述.其中,Cu(I)催化的叠氮-炔点击聚合可制备1?4-立构规整的超支化聚三唑;Ru(II)催化的叠氮-炔点击聚合可制备1?5-立构规整的超支化聚三唑;活化的炔类单体和叠氮单体的无金属催化点击聚合可得到1?4-异构体含量高(高达91.7%)的超支化聚合物;而光引发?热引发及自发的巯基-炔点击聚合可制备含硫的超支化聚合物.此外,对所制备的超支化聚合物的功能和应用进行了简单介绍,最后还简单讨论了点击聚合制备超支化聚合物方面的可能发展方向.     

超支化聚(胺酯)的合成及其光固化性能研究

采用甲基丙烯酸酐直接改性和先以丁二酸酐或邻苯二甲酸酐酯化再以甲基丙烯酸缩水甘油酯改性所得到的甲基丙烯酸酯化超支化聚 (胺 酯 )齐聚物在光引发剂存在时紫外光辐照下发生快速聚合反应 ;反应速率和双键转化率随超支化分子的结构不同而变化 ;高度交联的涂膜具有较好的热学性能     

超支化聚合反应的多尺度模拟

超支化聚合物具有与树枝状大分子相似的物理和化学性质,其具有合成简单、分子量分布宽等突出特点,超支化聚合物分子的结构形成取决于聚合反应过程,本文介绍了超支化聚合反应模拟研究的最新进展.首先介绍了八位置键涨落粗粒化格子模型在超支化聚合反应模拟中的应用,该方法考虑了聚合物分子空间位阻效应、分子内成环和反应点活性等影响因素,从而可以模拟不同类型的超支化聚合反应;为了定量描述单体和聚合物分子结构,研究者进一步发展了杂化多尺度超支化聚合反应模拟方法,该方法通过玻尔兹曼反演迭代方法获取单体和聚合物特异性粗粒化力场,然后通过粗粒化分子动力学方法结合反应性Monte Carlo方法对特异性超支化聚合反应进行定量模拟.多尺度聚合反应模拟不仅可以精确计算超支化聚合物分子量、多分散性指数和支化度等一般性聚合物参数,还可以获取分子成环率、超支化大分子构象等重要分子结构信息,在超支化聚合反应基础研究与预测方面具有重要应用价值.     

超支化树脂改性UV固化粉末涂料

本文将超支化树脂(HBP)与UV固化粉末涂料相结合,研究了超支化树脂对该涂料的树脂体系玻璃化温度、流变性能及涂膜各项物理性能的影响.结果表明:添加改性与未改性超支化树脂都能降低树脂体系的玻璃化温度,改性超支化树脂不影响体系的流变性能及涂膜性能,未改性超支化树脂可以降低体系粘度但使涂膜性能变差.     

超支化PAMAM桥联乙烯齐聚用镍系催化剂的合成与表征

以系列直链脂肪胺为核的低代超支化聚酰胺-胺(PAMAM)和水杨醛为原料,通过席夫碱反应制备系列新型超支化PAMAM桥联水杨醛亚胺配体;以无水Ni Cl2为络合试剂,通过络合反应合成系列超支化PAMAM桥联镍催化剂,采用FT-IR和1H NMR证实合成的系列新型配体和镍系催化剂的结构与其理论结构相符.对系列超支化PAMAM桥联镍催化剂催化乙烯齐聚的性能进行了研究,结果表明,超支化PAMAM桥联镍系催化剂配体骨架烷基链长度对其催化活性和选择性影响较小,助催化剂和溶剂影响较大;倍半乙基氯化铝为助催化剂,甲苯为溶剂时,聚合活性较高,产物中C8以上的高碳产物的含量最高;其中以十四胺为核的超支化PAMAM桥联镍催化剂为主催化剂、倍半乙基氯化铝为助催化剂、甲苯为溶剂时,催化乙烯齐聚活性高达1.96×106 g/(mol·h),齐聚产物中C8以上的高碳产物含量为98.77%.     

超支化分子自组装形成纳米纤维的计算机模拟研究

利用分子动力学模拟方法,针对实验上的超支化分子建立其粗粒化模型,模拟研究了该超支化分子在水和空气的界面上形成Langmuir单分子层的过程,并分析了通过自组装形成的纤维的微观结构.该纤维是由单排超支化分子线性排列形成,超支化分子的末端碳链裸露在空气中,且处于伸展的竖起状态.调节末端支链的亲疏水性能够影响形成的自组装结构,末端支链越亲水,超支化分子越不容易形成一维纳米纤维结构.     

两亲性超支化聚合物的研究进展

两亲性超支化聚合物作为一种新型功能性材料.近年来引起了人们的广泛关注.两亲性超支化聚合物的合成丰要是利用不同亲水性的链段对超支化聚合物端基进行改性,或者首先在超支化聚合物末端产生活性位点,再利用超支化分f作为大分子引发剂引发烯类单体进行斤环聚合、原子转移自由基聚合等得到以超支化聚合物为核的两亲性超支化共聚物;这些分子由...     

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%.     

α-Amino acid derived enaminones and their application in the synthesis of N-protected methyl 5-substituted-4-hydroxypyrrole-3-carboxylates and other heterocycles

A new and simple synthesis of novel N-protected methyl 5-substituted-4-hydroxypyrrole-3-carboxylates, which exist in equilibrium with their 4-oxo tautomers, has been developed in two steps starting from N-protected α-amino acids. The key intermediates are enaminones, which can also be isolated, characterized, and used for the construction of other functionalized heterocycles, before they spontaneously decompose to pyrrole products. 4-Hydroxypyrroles are prone to partial aerial oxidation but can be efficiently alkylated or reduced to stable polysubstituted pyrrolidine derivatives.     

Specific intramolecular aromatic CH insertion of diazosulfonamides

The chemoselectivity in the intramolecular CH insertion of various diazosulfonamides has been experimentally studied. The results reveal that the aliphatic 1,4-, 1,5-, or 1,6-C(sp³)?H insertions of diazosulfonamides are not accessible, while the aromatic 1,5-C(sp²)?H insertion can be realized specifically by adjusting the diazo-adjacent group. In addition, the general chemoselectivities in the intramolecular CH insertions of diazosulfonyl compounds are summarized. Generally, diazosulfones undergo both aromatic 1,5-C(sp²)?H and aliphatic 1,5- and 1,6-C(sp³)?H insertions, while diazosulfonates undergo aliphatic 1,5- and 1,6-C(sp³)?H insertions. However, diazosulfonamides only undergo aromatic 1,5-C(sp²)?H insertion.     

N-Heterocyclic carbene-palladacyclic complexes: synthesis,characterization and their applications in the C-N coupling and α-arylation of ketones using aryl chlorides

N-Heterocyclic carbene-palladacyclic complexes 3 were successfully achieved in a one-pot procedure under mild conditions. The structure of 3a was unambiguously confirmed by X-ray single crystal diffraction and it was an active catalyst in the Buchwald-Hartwig amination and α-arylation of ketones even at very low catalyst loadings (0.01?mol%).     

Iodine-mediated oxidative Pictet-Spengler reaction using terminal alkyne as the 2-oxoaldehyde surrogate for the synthesis of 1-aroyl-β-carbolines and fused-nitrogen heterocycles

An efficient iodine-mediated oxidative Pictet-Spengler reaction in dimethyl sulphoxide (DMSO) using terminal alkynes as the 2-oxoaldehyde surrogate for the synthesis of aryl (9H-pyrido[3,4-b]indol-1-yl)methanones is described. The scope of the protocol includes the total synthesis of Fascaplysin, Eudistomins Y₁ and Y₂. The methodology is extended for preparing pyrrolo[1,2-a]-quinoxaline and indolo[1,5-a]quinoxaline derivatives. The utility of 1-aroyl-β-carbolines was demonstrated by performing palladium-catalyzed β-carboline directed ortho-C(sp2)-H functionalization of the phenyl ring with thiomethyl (SMe) group using DMSO as source and for accessing 4-aryl-canthin-6-ones.     

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.     

Facile synthesis of bicyclic 1-arylpyrazol-5-ones

In this Letter, we described a facile method for constructing fused bicyclic 1-arylpyrazol-5-one ring system. We employed various methylene-containing carboxylic acids as the substrates and proved that the pyrazolone ring closure requires activated methylene group in intermediate II. Accordingly, a series of structurally diversified, fused bicyclic 1-arylpyrazol-5-ones was prepared in moderate to high yields using the requisite substrates.     

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.     

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.