氢键诱导的可控自由基聚合

氢键是一种非共价键的分子间相互作用,在超分子构建和功能材料合成领域已经得到广泛运用。氢键作用也被应用于可控自由基聚合体系中,以实现对分子量、立构规整性以及序列分布的微结构精密调控。近年来的研究结果表明,氢键诱导作用可提高聚合物分子量控制及聚合物的间同立构规整度;并且,当使用氟醇作为氢键供体溶剂,分别以甲基丙烯酸甲酯(MMA),4-乙烯基吡啶(4VP)和2-乙烯基吡啶(2VP)为单体进行的可控自由基聚合,氢键作用改变了共聚单体的序列分布,证明了氢键诱导下的单体双键活化作用。这为利用分子间非共价键诱导构建聚合物微结构的精密合成提供了新的策略。     

含甲氧基偶氮苯液晶基元超分子的相行为研究

氢键是分子聚集和识别过程中的重要相互作用,利用分子间氢键,可设计并制备各种超分子体系材料,1989年,Kato等报道了吡啶基和羧酸基通过分子间氢键相互作用形成扩展液晶基元,得到了液晶稳定性增强的超分子液晶复合体系及侧链超分子液晶聚合物;同时,Lehn等报道了带脲嘧啶基和2,6-二酰胺吡啶基两种互补官能团的分子通过三重氢键缔合形成的主链超分子液晶。从此,迅速而广泛的开展利用氢键组装的超分子液晶体系的研究,并已组装合成出低分子型、     

氰基二苯乙烯基超分子聚合物的构筑与光响应行为

通过在氰基二苯乙烯基元上引入氢键识别位点，驱使单体分子之间产生氢键与π-π堆积作用力的高效加合，构建了具有“成核-链增长”机制的超分子聚合物。通过获取组装热力学参数，揭示了酰胺及脲等不同氢键结构对于超分子聚合行为的影响规律。进一步利用超分子聚合态对于氰基二苯乙烯基元的限域效应，光照条件下特异性获得[2+2]环加成产物。与之相比，单体态时氰基二苯乙烯基元倾向于发生Z/E光异构化反应。这一研究结果可为多路径光化学反应的高效调控提供新的思路。     

酰胺水化作用的富里埃红外光谱研究及其SCFPPP计算

本文用富里埃红外光谱仪研究了酰胺水化作用引起的红外光谱变化。用SCFPPP方法对五种酰胺进行了计算。含水酰胺的羰基伸缩振动频率向低波数的位移与酰胺和水分子间的氢键强度成正比。其氢键强度与羰基上氧原子的净电荷密度成正比,与酰胺分子的HOMO轨道能量成反比。     

液晶性芳香酰胺化合物的合成

合成了一系列炖粹以酰胺基为中心桥键的刚性芳香酰胺小分子化合物，并对其作了表征，发现其中有些化合物具有液晶性。酰胺键之间能形成很强的分子间氢键，使芳香酰胺小分子化合物的熔点很高，难于形成液成液晶态。研究发现，如果在这类化合物的中心苯环上引入合适的取代基以减弱分子间氢键，同时引入合适的末端基时，则可使芳香酰胺化合物生成液晶相的能力增强。     

聚合物在荧光检测领域的应用

聚合物是由一种或几种重复单体以共价键连接形成的大分子化合物, 它不仅能够保持单体的性质, 而且由于聚合后单体间的协同作用, 使其表现出独特的性能. 聚合物作为基础材料在荧光检测领域得到广泛应用. 聚合物通过氢键作用、 亲疏水作用及范德华力等分子间相互作用, 实现了对特定目标物的选择性识别; 通过信号转换和放大功能, 可以将分子识别作用转化为荧光信号; 可以作为骨架连接多个识别单元, 通过多价结合作用等提高识别目标物的能力, 或连接不同的功能单元, 构建多功能的分子器件. 本文对聚合物在荧光检测领域的应用进行了概述.     

苄嘧磺隆印迹聚合物的波谱分析及吸附性能研究

以苄嘧磺隆为模板分子, α-甲基丙烯酸为功能单体, 三甲氧基丙烷三甲基丙烯酸酯为交联剂, 二氯甲烷为致孔剂, 在20 ℃温度下, 采用紫外引发沉淀聚合方法制备了苄嘧磺隆分子印迹聚合物. 紫外光谱和核磁共振氢谱实验提示了聚合前模板分子与功能单体之间的相互作用主要是分子间氢键, 分子间氢键相互作用能和双氢键的键距由Hyperchem 7.0和Gaussian 03W软件分别计算为: －28.6163 kJ/mol和0.179～0.181 nm. 制备的印迹聚合物在高效液相色谱和吸附动力学实验中都表现出对模板分子有较强的吸附作用.     

用红外光谱技术研究氢键的键合方式

氢键的形成能够使参与形成氢键的原化学键力常数降低,吸收频率移向低波数方向,同时吸收强度增加。为了介绍怎样利用红外光谱技术研究氢键的键合方式,本文以联酰胺衍生物为例,主要运用变温红外光谱技术分析NH伸缩振动波数、强度以及形成氢键的键长随温度的变化来研究羰基(C O)与氨基(H—N)之间的氢键形式。结果表明,本文举例中联酰胺基团中的C O与H—N以分子间氢键形式存在。     

超分子聚合机理

与共价键聚合物由单体(M1)通过共价键连接不同,超分子聚合物是由单体(M2)通过非共价键连接而成的长链大分子。聚合包括分子聚合和超分子聚合。超分子聚合描述M2通过非共价键自组装形成超分子聚合物的过程,涉及氢键、π-π堆砌型和立体匹配等驱动力以及分子识别、协同性等特征,与M1通过共价键形成聚合物的过程(分子聚合)不同。为了理解超分子聚合物链结构形成机理,本文分析和讨论超分子聚合的三个主要机理:(1)线性链生长;(2)螺旋链生长;(3)拓扑链生长。     

司它夫定分子烙印聚合物对模板分子的烙印效果研究

以抗爱滋病药物司它夫定为模板分子,甲基丙烯酸为功能单体,二甲基丙烯酸乙二醇酯为交联剂,用本体聚合法制备了分子烙印聚合物.本文考察了不同聚合条件和不同的单体与模板分子物料配比对产物分子烙印聚合物的吸附性能的影响.     

pH对丙烯酸-丁烯醛共聚合反应的影响

具有功能基的聚合物因其所具备的特殊性能而获得越来越多的应用[1] .带醛基的聚合物可在室温下很容易与酶、抗体、抗原、蛋白质、细胞等含氨基的生物高分子反应 ,生成Ｓｃｈｉｆｆ碱 ,将这些生物高分子共价偶联到聚合物上 ,并能保持它们绝大部分的生物活性 ,因而在免疫分析、生物化学、生物医学等领域有着广泛的应用前景[2～ 4 ] .然而 ,到目前为止 ,带醛基的聚合物的合成研究主要集中在丙烯醛的均聚及共聚反应[5～ 8] ,而对其它不饱和醛的聚合研究报道很少 .但是由于丙烯醛聚合物分子链上相邻的醛基极易形成缩醛或半缩醛而使自由醛基的数量…     

甲基丙烯酸三乙基锡酯的聚合反应动力学的研究

<正> 有机锡聚合物可以用于防污涂料,与低分子有机锡化合物相比,具有低环境污染、长效等特点。近年来,人们对有机锡单体的合成、纯化、聚合和共聚合进行了研究,但有关动力学的研究报道甚少,而甲基丙烯酸三乙基锡酯(TETM)的聚合动力学未见报道。     

Photochromism of 2-(2,4-dinitrobenzyl)benzimidazole in solution

Spectral and kinetic parameters of photochromic 2-(2,4-dinitrobenzyl)benzimidazole in various solvents were studied by flash photolysis. The absorption band of the photoinduced colored form of 2-(2,4-dinitrobenzyl)benzimidazole shifts red with rise in the relative dielectric constant of the solvent. The rate of bleaching of the photoinduced species in ethanol, propan-2-ol, acetone, acetonitrile, and dimethyl sulfoxide is lower by 2–3 orders of magnitude than in benzene, toluene, and hexane due to formation of intermolecular hydrogen bond with the solvent.     

甲基丙烯酸羟丙酯催化链转移聚合及其催化剂链转移常数的变化

采用COBF[bis(aqua)bis((difluoroboryl)dimethylglyoximato)cobalt(II)为催化剂,AIBN为引发剂,60℃下进行甲基丙烯酸β-羟丙酯的催化链转移自由基本体聚合,得到了端基含有双键的低分子量聚合物.分别用Mayo方程法和链长分布(CLD)方程法测算反应过程中催化剂的链转移常数,发现随着反应的进行,催化剂的链转移能力逐渐下降,表观链转移常数Csapp从反应初期的2000左右下降到600左右.这主要是由于反应初期形成了部分比较稳定的碳钴键,导致Csapp在一开始迅速下降,然后趋于缓慢;反应至中后期,由于粘度效应,表观链转移常数进一步降低到300以下.研究进一步发现,由CLD方程法所得的表观链转移常数值普遍低于由Mayo方程法所得的值,且高转化率时误差更大.这是因为GPC测得的是累积产物的分子量分布,对于中、高转化率情况,有必要将其转化为瞬时产物的值.由于累积产物的数均聚合度转化为瞬时产物的数均聚合度相对容易,因而Mayo方程法较适合于测算中、高转化率时的表观链转移常数.     

ε-己内酯负离子聚合过程烷氧基锂活性种的缔合

本文以粘度法研究在苯溶剂中,ε-己内酯负离子开环聚合过程,增长链活性种烷氧基锂(—O~-Li~+)的缔合,发现己内酯活性种的缔合和一般非极性单体不同,前者在聚合过程中(单体消耗完以前)并不发生缔合。在单体消耗完以后,聚己内酯活性种才确实以缔合体的形式存在。这是由于内酯本身贡献了强的溶剂化作用。     

Vinyl Polymerization. CLXVII. Vinyl Polymerization Initiated with p-Methoxy p′-nitrobenzoyl Peroxide

It was described in the literature that p-methoxy-p′-nitrobenzoyl peroxide decomposed homolytically in benzene, but heterolytically in acetone. However, in the present study the polymerizations of styrene and acrylonitrile were found to proceed always through radical mechanism in benzene, dimethylformamide, or acetone. And in the above various solvents, the rate of polymerization was found to be almost equal.     

Thermal polymerization of styrene in the presence of some ferrocene derivatives. II. Low concentrations of vinylferrocene and ethylferrocene

Styrene has been polymerized thermally at 60°C in the presence of low concentrations of vinylferrocene and in the presence and absence of 2,2′-azobisisobutyronitrile (AIBN). The polymerizations were studied in bulk and also in benzene solution. The thermal polymerization of styrene in the presence of ethylferrocene, but without added AIBN or solvent, was also examined. The bulk polymerizations exhibited high initial rates of polymerization followed by a decrease in rate. Initial rates of polymerization for bulk polymerizations in the absence of AIBN have been interpreted by means of a kinetic scheme involving propagation with styrene participating in a specific interaction with the ferrocene derivative and some kinetic parameters associated with this scheme have been evaluated. The decrease in the rate of polymerization is due to the formation of a retarder. The benzene solution polymerizations fitted a simple kinetic scheme and the transfer constant for vinylferrocene with respect to polystyryl radicals C_s, has been evaluated as 1.98 × 10^?3.     

聚乙烯醇对N-取代丙烯酰胺聚合反应的影响以及它们间相互作用的研究

在前文研究聚乙烯醇(PVA)对丙烯酰胺聚合反应效应的基础上,本文进一步研究了PVA对N-取代丙烯酰胺衍生物聚合反应的影响。发现PVA对N-甲基丙烯酰胺的聚合反应亦有减速作用,且减速程度与添加的PVA量间有一定量关系。而PVA对N,N-二甲基丙烯酰胺的聚合反应就无此效应。为考察PVA同丙烯酰胺AM类单体间的相互作用,进行了粘度测定,并采用(化学电离)质谱的方法证实了AM及N-甲基丙烯酰胺同1,3-丙二醇间所存在的分子缔合作用。对缔合物的形或模式进行了探讨。     

Analysis of the structures,energetics, and vibrational frequencies for the hydrogen-bonded interaction of nucleic acid bases with Carmustine pharmaceutical agent: a detailed computational approach

In the present study, it is attempted to scrutinize the hydrogen bonding interaction between Carmustine drug and DNA pyrimidine bases by means of density functional theory calculations regarding their geometries, binding energies, vibrational frequencies, and topological features of the electron density in the gas phase and the water solution. Based on the density functional theory results, it is found that the process of intermolecular interaction between Carmustine drug and nucleobases is exothermic and all of the optimized configurations are stable. Furthermore, the negative stability energy represented by a polarizable continuum model shows the significant increase in the solubility of the nucleobase after hydrogen bonding intermolecular interaction in the presence of water solvent. It is also found that the intermolecular hydrogen bonds between drug and the nucleobases play the significant role in the stability of the physisorption configurations. Hydrogen bond energies for hydrogen-bonded complexes are obtained from Espinosa method and the atoms-in-molecules theory are also applied to get a more precise insight into the nature of the intermolecular hydrogen bond interactions.     

Polymerization of 2‐hydroxyethyl acrylate in bulk and solution by chemical initiator and by ATRP method

In this study, 2‐hydroxyethyl acrylate (HEA) was polymerized to obtain polymers that can be used as hydrogel and copolymerized for biomedical applications. Bulk, solution, and atom transfer radical polymerization (ATRP) techniques at different temperatures were applied. The polymerization in bulk form was carried out in vacuum and in open atmosphere. The polymerization curves showed autoacceleration mechanism and the limiting conversion was 100%. The polymers obtained were insoluable in most common solvents because of high molecular weights and strong intermolecular hydrogen bonding. They absorb more than 30% (w/w) water as hydrogel. To decrease the molecular weight and obtain soluble polymers, HEA was polymerized in solution by ATRP method, which also gave insoluble hydrogel type polymers. The activation energy for bulk polymerization was 155.8 kJ/mol, which is very high for a free radical polymerization. This is due to the high degree of intermolecular hydrogen bonding, which was also supported by FTIR and TGA analysis. The polymers were characterized by FT‐IR, DSC, TGA, and ¹H NMR techniques. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 3957–3965, 2005