可描述硅橡胶弹性的理论模型

硅橡胶是一类应用广泛的弹性体材料.然而由于其复杂的三维网络结构,难以实现硅橡胶的理性设计.本研究尝试从单分子弹性入手来建立从硅橡胶微观力学性质到宏观性能之间的关联.首先,通过基于原子力显微镜的单分子力谱实验测量了甲基乙烯基硅橡胶中2个主成分(硅氧烷链和碳-碳链)的单链弹性(包含熵弹性和焓弹性).随后,利用量子力学计算得出上述2种分子链的理论单链弹性.硅氧烷链和碳-碳链的实验曲线均能与理论曲线很好地重合,表明已成功获取了这2种分子链在准无扰环境中的基准弹性.然后,2个主成分的基准弹性同时被整合到传统的橡胶统计学模型中.最终,通过参数可调的新橡胶弹性模型(称作TCQMG模型)描述了3种不同硅橡胶在整个形变范围内的力学性能.此外,借助TCQMG模型模拟了多个交联网络参数对于硅橡胶力学性能的影响,且模拟结果符合实验结果.该模型不仅有助于理解硅橡胶的复杂交联网络结构,还能够为新型硅橡胶的理性设计提供指导.考虑到硅橡胶与其他弹性体在交联网络结构上的相似之处,TCQMG模型有望用于描述这些弹性体的宏观力学性能.     

脂肪族α-氨基酸疏水自缔合作用的流动微量热法研究

建立了水溶液中脂肪族α- 氨基酸疏水自缔合相互作用的化学模型, 根据模型方程对由精密流动微量热法测得的α- 氨基酸水溶液的稀释焓数据进行回归分析, 得到等步自缔合作用的平衡常数(K)、焓变(ΔHm)和熵变(ΔSm)等热力学参数, 发现焓、熵之间存在很好的补偿关系. 同时计算了溶液中水的偏摩尔过量熵(SE1), 并根据脂肪族α- 氨基酸的水化模型对结果进行了讨论. 建立的化学模型参数能在一定程度上解释McMillan- Mayer模型中的同系焓作用系数的物理意义.     

端羟基聚丁二烯与2,6-甲苯二异氰酸酯固化网络 弹性力学性质的分子模拟

采用最大熵模型, 构建了HTPB预聚物的最可几结构. 考察了HTPB (nC＝9)与TDI全混合以及半混合的两种固化建模方式. 分子动力学模拟得到的HTPB (nC＝9)-TDI固化网络的N—N径向分布函数显示半混模式比全混模式的结构更均匀. 采用分子动力学动态模拟与静态拉伸方法对HTPB (nC＝9)-TDI固化网络进行弹性力学性质的模拟计算. 比较了半混和全混模式对拉伸模量计算的影响, 表明半混模式得到的固化网络能得到合理的模拟结果. 初步表明最大熵模型在研究HTPB固化问题上静态或动态模拟结果都具有唯象可行性.     

二甲基硅氧烷甘醇乙酸基共聚物水溶液的表面活性

通过表面张力的测定, 考察了不同无机盐和温度对二甲基硅氧烷甘醇乙酸基共聚物(PSEP)表面活性的影响, 进而研究PSEP在不同介质中胶束形成热力学性质. 研究表明, NaCl、NaBr和CaCl2的存在可提高PSEP的表面活性. 而且, PSEP的胶束化焓变对熵变呈线性相关, 说明存在焓/熵补偿现象.     

橡胶弹性模型的新进展

传统橡胶弹性模型存在一定的局限性,例如不能真实地反映橡胶的交联网络结构,不能解释多个网络结构参数对橡胶力学性能的影响,也不能很好地描述大变形条件下橡胶的弹性.为了解决上述科学问题,崔树勋等提出了一个新的模型(TCQMG模型),在该模型中橡胶交联网络同时包含顺-1,4-聚异戊二烯和聚硫,并且高分子链的弹性同时包含了熵弹性和焓弹性.研究表明,新的模型不仅可以很好地描述硫化橡胶的弹性,还可以解释硫含量等参数对橡胶性能的影响.考虑到天然橡胶与其他橡胶甚至超分子水凝胶在网络结构上的相似性,新模型也可能用于描述这些材料的力学性能.     

由脂肪族二酰胺二醇合成聚酯酰胺及表征

利用脂肪族二元酸酯与乙醇胺反应容易获得的对称二酰胺二醇,经缩聚合成聚酯酰胺预聚体,并针对端羧基和端羟基同时扩链来提高分子量,获得可生物降解的聚酯酰胺.首先将N,N′-二(2-羟乙基)草酰胺(HEOA)或N,N′-二(2-羟乙基)己二酰胺(HEHA)与己二酸和丁二醇缩聚,制备同时带有端羧基及端羟基的脂肪族聚酯酰胺预聚体,通过1,4-双(2-噁唑啉)苯及己二酰双己内酰胺混合扩链剂扩链,获得高分子量脂肪族聚酯酰胺,并通过红外、1H-NMR、DSC及TGA对其结构和热性能进行了表征.结果表明,预聚体在制备过程发生了一定的酯-酰胺交换反应;扩链后聚合物的熔点、熔融焓和热稳定性有所下降;但热稳定性仍接近或略高于聚己二酸丁二酯.     

反相高效液相色谱中溶质保留过程的热力学研究4: 焓熵补偿

依据液相色谱中溶质计量置换保留模型, 对溶质在反相液相色谱(RPLC)保留过程及其吸附、解吸附过程中的焓熵补偿进行了研究, 证实了在RPLC中焓熵补偿确实存在。从焓熵补偿的定义出发, 从理论上证明了溶质在保留过程中的焓熵补偿温度本质上为溶质保留值的收敛温度, 其数值为Z对1/T线性作图的斜率与截距之比。与惯常计算焓熵补偿温度的方法相比, 本文的方法所得补偿温度更为合理且不受流动相中强溶剂浓度变化的影响。     

反相高效液相色谱中溶质保留过程的热力学研究4: 焓熵补偿

依据液相色谱中溶质计量置换保留模型, 对溶质在反相液相色谱(RPLC)保留过程及其吸附、解吸附过程中的焓熵补偿进行了研究, 证实了在RPLC中焓熵补偿确实存在。从焓熵补偿的定义出发, 从理论上证明了溶质在保留过程中的焓熵补偿温度本质上为溶质保留值的收敛温度, 其数值为Z对1/T线性作图的斜率与截距之比。与惯常计算焓熵补偿温度的方法相比, 本文的方法所得补偿温度更为合理且不受流动相中强溶剂浓度变化的影响。     

多溴代芴热力学性质的理论预测研究

为了预测环境污染物多溴代芴的热力学性质,计算了60种多溴代芴的分子连接性指数、电性距离矢量指数、电性拓扑状态指数以及分子形状指数.采用多元线性回归的方法建立了多溴代芴化合物的标准生成焓(Δ_fH~0)、标准熵(S~0)、标准生成吉布斯自由能(Δ_fG~0)及等容热容等热力学性质的QSPR相关性模型,方程的相关系数值均在0.99以上.与相关文献的相关系数R和标准误差S进行比较,该模型具有良好的预测能力和稳定性.     

一种新的自相关拓扑指数及其互补指数应用于不饱和链烃物理性质的QSPR研究

依据系统命名法的编号原则及不饱和链烃的结构特证,建立了原子的染色序数(ti),并在邻矩阵基础上由ti构建原子染色序数自相关指数(mR)及互补指数mR′,其中0R1、R、互补指数0R′1、R′,C原子个数(N)与炔烃的沸点、烯烃的热力学性质(标准生成焓、标准熵、标准熵和标准生成自由能)有良好的相关性,相关系数分别为0.999 2,0.999 4,0.999 4和0.994 1.该模型用于预测不饱和链烃的物理性质,计算简便,结果准确.     

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.     

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.     

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.     

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.