聚合物防污材料表面水化层的分子动力学模拟

采用分子动力学方法研究了吸附在聚二甲基硅氧烷(PDMS)和接枝聚磺酸基甜菜碱甲基丙烯酸甲酯(pSBMA)改性后的防污材料膜水化层内的水分子的结构及其动力学性质, 从微观角度解释了聚合物膜具有防污性能的原因. 模拟发现: (1)紧靠聚合物膜形成的水化层是聚合物具有防污性能的关键因素, 该水化层是溶液中的粒子(包括蛋白质分子)与聚合物膜相接触时所要克服的最主要的物理能障; (2)相对PDMS聚合物膜而言, 双离子特性自组装膜(pSBMA)在氢键、静电力的共同作用下, 可以形成空间笼状水分子网结构对水分子具有更强的束缚作用并有效降低水分子的可运动性, 形成的稳定水化层使得pSBMA具有更强的阻碍蛋白质吸附的能力.     

化学交联聚乙烯醇(PVA)水凝胶的合成、表征及溶胀特性

用环氧氯丙烷作交联剂,制备了一种聚乙烯醇(PVA)水凝胶.用FTIR和GPC方法对其结构作了表征.在干凝胶中逐步加水使其溶胀,通过差示扫描量热(DSC)方法测量溶胀水凝胶中不同状态水的含量变化来研究凝胶的溶胀特性.结果表明,当水进入干凝胶网络后首先与网络链上的亲水基团通过氢键的结合形成非冻结水,非冻结水与干凝胶的比值为0.20.非冻结水饱和之后,额外再加入的水渗入网络空间,同步形成冻结水与自由水两种状态直至达到平衡溶胀为止.     

生物分子水溶液的Monte Carlo模拟——丙氨酸溶液

本文对由五十六个水分子包围一个中性的丙氨酸分子所构成的分子集团做了MC模拟计算。求出了水—水和氨基酸—水的平均相互作用能。将丙氨酸分子周围的空间划分为三个区域——羧基区、氨基区和甲基区。分别以羧基碳、氨基氮和甲基碳作为中心原子,统计了各区中水—水和水—氨基酸相互作用能随着水分子中的氧原子和该区中心原子的距离而改变的函数,各区中水分子偶极矩的取向关联函数以及水分子中氧原子和氢原子的径向分布函数。此外,还计算了各区第一个水化层的水分子数和整个丙氨酸分子第一个水化层的水分子数。     

烷基芳基磺酸盐的分子动力学模拟与自由能微扰计算

为研究不同结构的表面活性剂分子在溶液中胶束化能力的差异, 采用分子动力学方法模拟三种烷基芳基磺酸盐在真空和水溶液环境下的结构与相互作用. 利用自由能微扰(FEP)方法计算了水合自由能, 发现与用传统热力学表面张力法测定自制的烷基芳基磺酸盐结果一致. 研究表明: 烷基芳基磺酸盐在水溶液中的胶束化过程是自发进行的, 随着分子结构中芳环向长烷基链中间位置移动, 胶束化能力和胶束稳定性均下降; 疏水基周围水分子的“冰山结构”会影响胶束的稳定性, 而水分子中氢键的生存周期是反映冰山结构变化的重要指标; 同时, 亲水基与水分子间形成氢键的数目会增强或减弱分子脱离胶束体的趋势, 从而影响胶束结构的稳定性.     

特殊缔合体系TFE水溶液分子动力学模拟

三氟乙醇(TFE)水溶液是一类特殊的缔合体系. 采用分子动力学模拟方法结合核磁共振化学位移研究了TFE水溶液体系全浓度范围的氢键网络, 并对动力学模拟结果和核磁共振化学位移进行了比较. 从径向分布函数(RDF)发现, TFE水溶液中存在着强氢键, 而体系中的C—H…O弱相互作用较为明显, 也不能忽略. 氢键网络分析发现TFE 水溶液体系的氢键大致分为以下三个区域: 在水富集区域, 水分子倾向于自身缔合形成稳定的簇结构, 随着TFE 浓度的增加, 水的有序结构受到破坏, 水分子和TFE分子发生交叉缔合作用形成氢键; 在TFE富集区域, 水分子较少, TFE分子自身通过氢键形成多缔体结构. 此外, 分子动力学统计的平均氢键数的变化和文献报导的核磁共振化学位移变化趋势相同, 实验和理论的结果吻合较好.     

N-异丙基丙烯酰胺-丙烯酰胺热敏凝胶的溶胀特性

制备并表征了N-异丙基丙烯酰胺-丙烯酰胺热敏凝胶(NIPAm-Am),研究了单体配比、引发剂、交联剂用量和温度对其溶胀特性的影响。结果表明：NIPAm-Am热敏凝胶是由亲水和疏水基团组成的非晶高聚物。mAm／mNIPAm越大,凝胶的平衡溶胀率越大;增加交联剂的用量,凝胶的溶胀率减小,当引发剂的质量分数为0．008时溶胀率达最大值;温度的增加会使凝胶的溶胀率减小,在相转变温度时,溶胀率的变化最大。     

温度敏感聚(N-异丙基丙烯酰胺-co-甲基丙烯酰氧乙基二甲基辛基溴化铵)水凝胶的溶胀性能研究

由于改变亲水／疏水单体比值、与离子单体共聚心、改变凝胶内部结构等均可不同程度地调整温敏水凝胶的溶胀性能,本研究选择一种既含疏水烷基又含季铵盐正离子型亲水基团的两亲性单体——甲基丙烯酰氧乙基二甲基辛基溴化铵（ADMOAB）,结构如示意图1所示．与N-异丙基丙烯酰胺（NIPAM）聚合,制备了P（NIPAM-co-ADMOAB）共聚水凝胶,以便在引入离子型结构单元的同时,改变凝胶体系中亲水／疏水单体比值,避免单纯增加疏水单体引起的水凝胶溶胀性降低问题,并考察了ADMOAB对水凝胶溶胀性能的影响,对该类水凝胶迄今鲜见相关文献报道．该研究对进一步了解水凝胶的构效关系、探索有效控制溶胀性能的途径具有积极意义．     

确定分子量的聚丙烯酸-β-羟乙酯的合成及其水溶液中水氢键缺损的拉曼光谱学研究

水溶性高分子经化学交联可得水凝胶 ,水凝胶也可由水溶性高分子经物理交联如部分结晶微区 ,疏水相互作用及缠绕交联得到 .线型水溶性高分子在水中以高浓度溶解时 ,高分子链之间相互搭迭缠绕也能形成物理“交联” .Ｋｉｔａｎｏ[1～ 4 ] 等研究了聚环氧乙烷、聚丙烯酸、聚丙烯酰胺和聚乙烯基吡咯烷酮等亲水性高分子水溶液中水分子间的氢键缺损情况 ,在重量浓度相同的情况下 ,随着分子量的增大 ,水分子间的氢键缺损加剧 .他们认为分子量大 ,高分子之间的缠绕就比较严重 ,在水溶液中就会形成许多小的微区 ,水分子在这些小微区中形成分子间氢键…     

快速响应大孔聚(N-异丙基丙烯酰胺-co-丙烯酸)水凝胶的合成及表征

以聚乙二醇6000为成孔剂,由自由基引发N-异丙基丙烯酰胺(NIPA)和丙烯酸(AAc)共聚交联得到大孔凝胶,研究了凝胶对环境温度的响应性能.在凝胶制备过程中,PEG6000分子充当成孔剂,得到的凝胶具有大孔结构.这种大孔结构有利于水分子的进出,大孔凝胶对温度变化有较快的响应速率.增加亲水单体AAc的含量,凝胶的LCST有所升高,凝胶的亲水性增强,在较低温度下凝胶的溶胀率也随之升高.振荡实验表明,所得的大孔凝胶具有反复使用的能力.     

L-丝氨酸在丙二醇-水和丁二醇-水混合溶剂中的体积性质

利用精密数字密度计测定了L-丝氨酸分别在不同组成的1,2-丙二醇-水和1,2-丁二醇-水混合溶剂中的密度, 计算了丝氨酸的表观摩尔体积、极限偏摩尔体积、迁移偏摩尔体积和理论水化数. 根据结构水合作用模型讨论了迁移偏摩尔体积和理论水化数的变化规律. 结果表明, 丝氨酸两性离子头基和亲水侧链与醇分子中—OH基团间的相互作用占主导地位, 导致丝氨酸在醇-水混合溶剂中的迁移偏摩尔体积为正值; 此外, 这种亲水相互作用削弱了丝氨酸带电中心对周围水分子的电致收缩效应, 造成了水化数的减小.     

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%.     

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.     

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.     

A general and convenient synthesis of 4-(tosylmethyl)semicarbazones and their use in amidoalkylation of hydrogen,heteroatom, and carbon nucleophiles

A general synthesis of previously unknown semicarbazone-based α-amidoalkylating reagents, 4-(tosylmethyl)semicarbazones, has been developed. The synthesis involved three-component condensation of semicarbazones of aliphatic or aromatic aldehydes with the same or other aldehydes and p-toluenesulfinic acid. The scope and limitations of this reaction were investigated. The compounds obtained were demonstrated to be an efficient α-(4-semicarbazono)alkylating agents. They were reacted with H- (sodium borohydride), O- (sodium methylate), S- (sodium phenylthiolate), N- (pyrrolidine, sodium succinimide), P- (trialkyl phosphites), and C-nucleophiles (sodium diethyl malonate) to give the corresponding products of the tosyl group substitution, 4-substituted semicarbazones, including analogues of nitrofurazone. Among the prepared compounds tested in vitro for antibacterial and antifungal activity, three nitrofuryl-containing semicarbazones exhibited high biological activities with minimum inhibitory concentration (MIC) values of 8–32 μg/mL.     

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.     

Synthesis of novel chiral bidentate hydroxyalkyl-N-heterocyclic carbene ligands and their application in palladium-catalyzed Mizoroki–Heck couplings and asymmetric addition of diethylzinc to benzaldehyde

A small library of new chiral bidentate hydroxyalkyl-imidazolium salts 1 is conveniently synthesized on multi-gram scale from inexpensive and commercially available chiral pool amino acids. The corresponding carbenes, generated by deprotonation of imidazolium salts 1, in combination with palladium(II) chloride were tested in the Mizoroki–Heck coupling reaction. The most significant results in terms of yields and reactivities were achieved with low catalyst loading. The catalytic activities of these imidazolium salts were also investigated in the asymmetric addition of diethylzinc to benzaldehyde. The use of MgO nanoparticles as an additive in conjunction with these ligands played a crucial role in increasing the efficiency of these reactions.