树状大分子的手性构建

综述了手性基团的树状大分子中的构建,并对此类化合物的性质及研究和应用前景作了简要介绍。     

新型端胺基聚酰胺-胺树枝状大分子合成研究

研究了以丙烯酸甲酯、己二胺、对苯二酚为原料,采用发散法合成新型端胺基聚酰胺-胺树枝状大分子时,反应条件——温度、反应时间、催化剂对合成产物的结构的影响。利用该树枝状大分子的活性点分布均匀的特点,通过设计和控制树枝状大分子模板剂来控制纳米粒子材料的形状。     

PAMAM树状大分子负载和释放阿霉素的耗散粒子动力学模拟

采用耗散粒子动力学模拟方法研究了药物输送载体聚酰胺-胺（PAMAM）树状大分子对抗癌药物阿霉素（DOX）的负载和释放行为。构建了PAMAM树状大分子的粗粒化模型,该模型能准确地重现树状大分子的构象性质。考察了PAMAM树状大分子代数（G）对DOX负载以及pH环境对DOX释放的影响。模拟结果表明,PAMAM树状大分子主要通过疏水作用将DOX包封于内部空腔,G6和G7 PAMAM树状大分子的负载能力较强,因为其孔隙率较高,内部有更多的疏水空腔。在低pH环境下,PAMAM树状大分子结构发生变化,DOX分子能快速地从其中释放,主要原因是PAMAM的伯胺、叔胺和DOX伯胺发生质子化,质子化基团间的静电排斥作用使得PAMAM树状大分子发生溶胀,导致其内部空腔暴露,促进了DOX的释放。本工作可以为基于树状大分子的药物输送体系的设计和优化提供参考。     

简化空穴理论状态方程在链状分子及有机溶剂液体中的应用

基于不完全晶体的热缺陷统计理论,将液体晶格中被占座席分率表示为对比温度的指数函数,推出了一个适用于聚合物,链状大分子及有机溶剂的液体状态方程。将此简化了的状态方程用于17种大分子链烃及10种常见的有机溶剂P-V-T计算,结果与实验值十分相符。与Simha和Somcynsky的空穴理论状态方程式相比较,计算大为简化且精度相当,易于应用至混合物体系。     

认识“环境敏感型”生物大分子

生物技术在现代生活中扮演着越来越重要的角色。本文着重分析了＂环境敏感型＂大分子及大分子体系在特定环境条件下发生的一些特定的物理和化学性质的变化机理以及利用控制大分子构象得到对特定外界因素敏感的大分子或大分子体系。目的是认识＂环境敏感型＂大分子或大分子体系在生物技术产品的分离纯化上的具体应用。     

浅析分子印迹技术的发展及在化工制药筛选的应用

本文概括的介绍了近年来关于分子印迹技术在生物大分子方面的发展、应用和检测情况,为生物材料领域研究工作提供了相关研究热点。     

分子印迹模板分子类型研究进展

综述了模板分子的选择概况,包括有机小分子、生物大分子、细胞和病毒、无机离子和虚拟模板分子,并对模板分子的局限性做了详细介绍,以期对分子印迹技术的发展提供一些参考。     

纯振动场作用下聚合物粘弹性能的微观研究

通过对聚合物大分子与其他低分子的比较．指出了聚合物大分子具有独特分子结构、大的相对分子质量和长的分子链．以及由此引起的一系列特有的物理化学性能。从微观的角度解释了振动场作用下、聚合物大分子的运动情况．提出了聚合物大分子在振动状态下的橡皮筋模型．比较了直接加热与纯振动场作用下两种不同换能方式对聚合物同体材料塑化性能的影响，得出了纯振动场作用比直接加热更能促进聚合物材料塑化的结论。按照橡皮筋模型的原理．建立了广相应的力学模型。运用偏微分方法对该力学模型讲行求解，找出了振动场对高聚物的作用机理。     

琼脂糖凝胶大分子在陶瓷原位凝固成型中的应用

研究了一种新的陶瓷原位凝固成型方法,其原理是依据琼脂糖凝胶大分子在水溶液中加热时溶解,冷却时凝固这一物理变化。对于固相体积分数大于50％陶瓷悬浮体中引入约1％（质量分数）琼脂糖大分子,即可凝胶注模进行各种形状复杂的陶瓷部件成型,获得表面光洁、内部孔隙尺寸和密度分布均匀的陶瓷坯体,并烧结出均匀致密内部无明显缺陷的涡轮转子等异型部件。     

生物大分子介导仿生矿化制备磁性纳米粒子的研究进展

相比其他纳米材料,磁铁矿（Fe₃O₄）纳米粒子由于具有磁响应性而被广泛应用于酶固定化、定向给药及核酸提取等方面。不同大小和形状的磁铁矿纳米颗粒可用于不同的领域,如晶体尺寸越小的Fe₃O₄对人体副作用越小,有望用于疾病高效、靶向治疗。近年来,控制Fe₃O₄纳米粒子大小和形貌的新方法研究逐步成为热点。因此,本文回顾了传统的共沉淀制备磁性纳米颗粒的方法,这些方法需要使用有机溶剂或高温等条件控制,介绍了这些方法存在的环境污染和安全性问题。在此基础上,本文深入介绍了近年来出现的一种受自然界生物矿化启发的生物大分子介导的仿生矿化制备磁性纳米粒子的新趋势,综述了生物大分子蛋白质（或多肽）介导的仿生矿化的最新研究进展,阐释了该方法在磁铁矿（Fe₃O₄）纳米粒子的大小和形貌控制方面的优缺点,并对其应用前景及面临的挑战进行了展望。     

分子蒸馏装置中刮膜器对液膜流动状况的影响研究

分子蒸馏是一种高效的液体分离技术,在工业生产领域具有广泛的应用前景。为了探究设备中液膜的流动状况,今使用计算流体力学软件FLUENT 6.3对刮膜式分子蒸馏过程进行模拟,分别考察了刮膜器的形状、转子转速、转子半径、转子与壁面间的缝隙等因素对不同黏度流体的液膜均匀程度和湍流程度的影响。结果表明圆形转子和倾斜刮板有助于液体在蒸发壁面上形成均匀分布的薄膜,因此更适用于分子蒸馏过程;转子的结构参数对高黏度物料的流动状况的影响更为显著,在一定范围内高黏度物料的均匀度和湍流度都随转子半径和缝隙的增大而增大。研究的模拟结果对分子蒸馏过程具有深刻的理论意义和实际指导意义,为刮膜式分子蒸馏装置的设计提供了参考。     

Effect of fluorinated substituents on hydrodynamic and conformational properties of hyperbranched polycarbosilane in solutions

Fractions of hyperbranched polycarbosilane modified with fluorine-containing end groups are studied by the methods of molecular hydrodynamics and optics in dilute solutions in hexafluorobenzene, methyl tert-butyl ether, chloroform, tetrahydrofurane, and toluene. The results are compared with the data available for the original polymethylallylcarbosilane. The incorporation of fluorinated groups leads to a change in the hydrodynamic parameters of the hyperbranched polymer. In this case, in thermodynamically better solvents, the patterns of the molecular-mass dependence of intrinsic viscosity for fluorinated and original hyperbranched polycarbosilanes coincide since the macromolecules of the polymers under comparison are characterized by similar shapes and almost the same hydrodynamic sizes. In a thermodynamically worse solvent (toluene), the above-mentioned changes in hydrodynamic parameters and the character of the molecular-mass dependences are related to compaction of macromolecules and a decrease in their shape asymmetry. This tendency is probably associated with the selectivity of this solvent with respect to the fluorine atom.     

Friction Coefficient and Mobility Radius of Fractal-Like Aggregates in the Transition Regime

The influence of geometric properties and particle size on mobility properties of fractal-like aggregates was studied in the mass and momentum-transfer transition regimes. Two methodologies were investigated. The Collision Rate Method (CRM) that determines the slip correction factor through the ratio of two fictitious Brownian particle-aggregate effective collision rates, and the Adjusted Sphere Method (ASM) that assumes the existence of a virtual, flow-independent adjusted sphere with the same slip correction factor as the aggregate over the entire transition regime. The simulated fractal-like aggregates were synthetic as they were generated via a cluster–cluster agglomeration algorithm. The CRM was used to calculate the adjusted-sphere radius of various aggregates: we found it to be weakly dependent on the monomer Knudsen number for Kn greater than 0.5. Numerical expressions for the aggregate orientationally-averaged projected area and the adjusted-sphere radius are proposed. Both expressions depend on geometric, non-ensemble averaged quantities: the radius of gyration and the number of monomers. The slip correction factor and the mobility radius of DLCA and RLCA aggregates were calculated using the ASM: for a given number of monomers, fractal dimension and prefactor, and Knudsen number their values were approximately constant (averaged over aggregate realizations). A fractal-like scaling law based on the mobility radius was found to hold. The mobility fractal dimension and prefactor were determined for different aggregates. The hydrodynamic radius, proportional to the friction coefficient, and the dynamic shape factor of DLCA and RLCA aggregates were also calculated.     

Behavior of hyperbranched polymers in solutions

Hyperbranched polycarbosilanes are investigated by the methods of molecular hydrodynamics and optics. Dependences of the hydrodynamic and conformational properties of these polymers on their molecular mass, the length of linear chains between branching points, and the chemical structure of end groups are analyzed. The hydrodynamic behavior of hyperbranched polycarbosilanes is explained by the fact that the dimensions of their macromolecules are compact and their shape is close to spherical. The convolution of chains between branching points becomes more pronounced with an increase in their length and a decrease in the molecular mass of the polymer. When end fluorinated groups are incorporated into the hyperbranched polycarbosilane, in thermodynamically good solvents and θ solvents, hydrodynamic characteristics change apparently owing to a change in the density of macromolecules in solution. In a poor solvent, the compaction of fluorinated macromolecules and a reduction in their shape asymmetry are observed. At a fixed branching degree, the hydrodynamic properties of hyperbranched polymers depend on the structural regularity of their macromolecules: In terms of hydrodynamic properties, the hyperbranched polycarbosilane with a degree of branching of 1 and a random distribution of branching points within the volume of a macro-molecule is appreciably different from a dendrimer of the same chemical nature and is close to polycarbosilanes with a degree of branching of 0.5.     

Chain contraction at the critical overlap concentration

The sedimentation of dissolved macromolecules is analyzed in both the regions of very dilute solution and in semidilute regime employing the fractal aggregate model of macromolecular coils and blobs. The macromolecules entering the overlapping region are represented by more compact aggregates than that modeling the individual macromolecule of the same mass and fractal dimension. This regularity is confirmed by analyzing the hydrodynamic behavior of several polymer-solvent systems in a wide interval of fractal dimension including the polymers dissolved in both the theta and real solvents. The reduced hydrodynamic volume of macromolecules is about 0.3-0.5 of that of the individual macromolecule. This well corresponds with the literature data obtained by measurement of the reduction of the static correlation length with concentration and those determined by dielectric study of the end-to-end distance.     

In situ characterization of floc morphology by image analysis in a turbulent Taylor–Couette reactor

Flocculation of bentonite was performed in a turbulent Taylor–Couette reactor under various shear rates. Image processing enabled to determine various morphological characteristics of individual flocs. Not only their mean values but also their distributions were studied under various hydrodynamic conditions. Relevant properties were selected. The temporal evolution of radius of gyration and circularity distributions was monitored during the flocculation process. Although size and shape are obviously correlated, this article points out that their dependency to hydrodynamics is different, showing that flocs of similar sizes produced under different hydrodynamic conditions exhibit different shapes. The sizes are calibrated by the turbulence as the double radius of gyration is close to Kolmogorov microscale, whereas the circularity seems correlated to the rotation speed. © 2014 American Institute of Chemical Engineers AIChE J, 60: 2389–2403, 2014     

Conformational and hydrodynamic parameters of hyperbranched pyridylphenylene polymers

Hydrodynamic and optical methods were applied to study conformational and physical properties of hyperbranched pyridylphenylene polymers in dilute solutions. The samples were synthesized using Diels–Alder polycyclocondensation. It was demonstrated that hydrodynamic properties of the studied macromolecules were typical for compact non‐percolated spheres. Optical and electro‐optical methods revealed information regarding the shape and asymmetry of the macromolecules (p ≈ 1.4). The contributions of optical shape effect to the observed flow birefringence of polypyridylphenylene solutions and intrinsic anisotropy of polarizability were evaluated and analysed. It was shown that varying the polymer composition (i.e. the degree of branching) caused considerable changes in the anisotropy of optical polarizability of the polymers. Dramatic difference of the electro‐optical properties in non‐polar (toluene) and polar (tetrachloroethane) solvents was found; this difference was related to the orientational correlation of polar solvent molecules with respect to the macromolecules. Dynamic properties were studied by non‐equilibrium electric birefringence which had a reasonable agreement with the dimensions estimated from hydrodynamic data. © 2016 Society of Chemical Industry     

SELF-DIFFUSION IN POTENTIALS OF MEAN FORCE IN WEAKLY- AND STRONGLY-INTERACTING DISPERSIONS

Studies of interactions in dispersions have traditionally focused on the stability and transport properties of such systems at extreme dilution, that is, at concentrations for which colloidal and hydrodynamic interactions are significant between at most two particles at a given time. In practice, however, dispersions of interest often do not satisfy this restriction, and, consequently, many-body colloidal interactions and hydrodynamic coupling have important roles in the observed macroscopic behavior. This paper presents an analysis of the effects of many-body interactions on the self-diffusion coefficient in interacting dispersions. Self-diffusion coefficients have been determined for dilute-gas dispersions and for Yukawa dispersions interacting through appropriate potentials of mean force. It is shown that the diffusion coefficients change negligibly with attraction for typical magnitudes of the Hamaker constant in an otherwise repulsion-dominated (i.e., stable) dispersion. The results show that, for thin electrical double layers, dilute dispersions can be approximated by hard-sphere dispersions, even for large values of surface potentials. However, for thick double layers (i.e., thickness comparable to particle radius), while the short-time diffusion coefficient is affected only negligibly, the long-time coefficient can decrease considerably because of the 'memory' effects—even for moderate or low values of the surface potentials. Corresponding results are presented for both dilute-gas dispersions and dispersions with significant local structures. The long-time diffusion coefficients in the latter are effectively linear in volume fraction (up to about 0.2)for thin double layers and are given with reasonable accuracy by the dilute-gas approximation.     

重油组分宏观尺寸表征方法的研究进展

介绍了表征重油组分宏观尺寸的流体力学性质关联法,小角散射法以及电子显微镜成像法.流体力学性质关联法主要用来计算重油组分分子尺寸,而小角散射法和电子显微镜成像法则用来表征沥青质胶粒形态尺寸.在对上述各方法的基本原理、应用条件和存在问题进行分析概括的基础上,认为沥青质胶粒尺寸、形状和分布的表征方法比较成熟;黏度.扩散系数联合法研究极稀溶液区重油组分的流体力学性质,是表征重油组分尤其是沥青质分子形态尺寸的-种有效方法.     

Mean-square radius of gyration and hydrodynamic radius for topological polymers evaluated through the quaternionic algorithm

We evaluate numerically the mean-square (MS) radius of gyration and the diffusion coefficient for topological polymers such as ring, tadpole, double-ring, and caged polymers and catenanes. We consider caged polymers with any given number of subchains, and catenanes consisting of two linked ring polymers with a fixed linking number. Through Kirkwood’s approximation we evaluate the hydrodynamic radius, which is proportional to the inverse of the diffusion coefficient, for various topological polymers. Here we take the statistical averages over configurations of topological polymers constructed through the quaternionic algorithm, which generates uniform random walks connecting given two points. It gives ideal chains with no excluded volume. We evaluate numerically the ratio of the square root of the MS radius of gyration to the hydrodynamic radius for several topological polymers, and show for them that the ratio decreases as the topology becomes more complex.