Self‐Consistent Integral Equation Theory for Semiflexible Polyelectrolytes in Poor Solvent

Self‐consistent hybrid MC/PRISM method is presented for calculating properties of polyelectrolytes in semidilute and more concentrated regimes in a poor solvent. The static structure and conformational behavior of salt‐free polyelectrolyte solutions composed of semiflexible polyions and monovalent counterions are studied using the approach which combines the traditional Monte‐Carlo (MC) simulation with the numerical solution of the polymer integral PRISM equation. The MC technique is applied to generate the configurations of a single chain molecule and obtain the averaged intrapolymer correlation function. The PRISM equation is then numerically solved for a given monomer density to obtain the various correlation functions and the medium‐induced intrapolymer potential. This is used in a single chain MC simulation, where the polymer sites interact via the bare Coulomb potential together with the short range attractive potential and a self‐consistently determined medium‐induced potential. The monomer‐monomer pair correlation functions and static structure factors are calculated for a large variety of parameters. Conformational properties such as the radius of gyration and visual images are obtained as a function of attractive short‐range interaction, monomer density, Bjerrum length, and chain stiffness. The MC/PRISM study predicts that there is a range of hydrophobicity and monomer density for which polyion chains can form the toroidal structure in a poor solvent. Nonmonotonic dependence of the chain size on monomer density is predicted over the entire range of parameters. Polyion structure factor peak position as a function of density is described. Two concentration regimes in which the polyion structure factors exhibit physically different peaks were found. Over the entire concentration regime considered polyelectrolyte chains undergo strong compression with R_g ∝ lequation/tex2gif-stack-1.gif.

Conformation of a polyion chain for l_B = 2, ε = 0.18 at ρ* = 0.2 and α = 10°.     

Studies on the Condensed Structure of Vacuum Cast Atactic Polystyrene Films

IntroductionIn de Gennes' scaling theoryL'], polymer solutions are divided into dilute, semidilute andconcentrated regimes corresponding respectively to separated chains, overlapping and interpenetrating chains, and fully entangled chains -- a dynamic network structure[2]. Particularly, the critical overlap concentration c' is introduced as a boundary concentration to separate the semidilute solution from the dilute one, where the polymer coils in the solution beginto be in contact with each o…     

桥函数在统计力学积分方程理论3d-RISM-HNC的应用和溶剂化自由能计算的改进

把氢-桥函数和氧-桥函数应用于统计力学积分方程理论的三维的参考作用点-超链模型(3d-RISM-HNC)中,用以改进极性和非极性溶质的水溶液的热力学性质的计算.用三维和二维图形考察了溶剂水分子的氢原子和氧原子的桥函数在改进溶剂作用点的平均密度分布函数〈ρ_H(r)〉和〈ρ_O(r)〉,和平均超额化学势〈Δμ(r)〉的计算的效果.计算结果表明,氢桥函数和氧桥函数极大地改进了3d-RISM-HNC 方法的精度,把这一方法提高到定量和半定量的水平.研究表明,溶质分子的作用点的超额化学势的径向分布函数〈Δμ(r)〉比平均密度分布函数〈ρ_s(r)〉能够更灵敏地反映桥函数的改进效果.研究表明,为提高3d-RISM-HNC 方法的精度,需要进一步改进桥函数的函数形式和优化其中的参数.     

等规聚苯乙烯结构与性能研究进展

本文综述了等规聚苯乙烯的结构与性能的研究。着重讨论等规聚苯乙烯的差向立体异构化、结晶行为、凝胶特性及其机械力学性能与结构的关系，同时还讨论了等规聚苯乙烯的加工与应用前景。     

Liquid structure of vanadium tetrachloride from neutron diffraction study

Assuming the separation of the intermolecular scattering function into the radial and angular parts and using Egelstaffet al’s orientational model for tetrachlorides, the structure of liquid vanadium tetrachloride has been studied. It has been observed that such a separation is approximate for this liquid and the introduction of a third correction term is required to account for the molecular structure function. The chlorine-chlorine partial structure and effective angleaveraged intermolecular chlorine-chlorine potential in the liquid has been evaluated. Without taking the third correction term, introduced to generate theoretically the molecular structure function, the centre structure function has been obtained in an approximate way from the experimentally observed molecular structure function and from it the centre radial distribution function, centre direct correlation function and the angle-averaged vanadium-vanadium effective potential has been evaluated.     

合成高分子量无规聚丙烯—在烷烃溶剂中聚合及性能初步表征

丙烯聚合;茂金属催化剂;立体结构;合成高分子量无规聚丙烯—在烷烃溶剂中聚合及性能初步表征     

交联聚苯乙烯氨基树脂的结构与脱色性能研究

通过改变交联度、致孔剂以及胺化试剂合成了一系列大孔氨基吸附树脂。详细研究了树脂孔结构、功能基结构与树脂脱色性能的关系。     

On the Stability of Cyclophane Derivates Using a Molecular Fragmentation Method

A molecular fragmentation method is used to study the stability of cyclophane derivates by decomposing the molecular energy into the molecular strain and intramolecular interaction energies. The molecular strain energies obtained by utilising the fragmentation method are in good agreement with existing experimental data. The intramolecular interaction energies calculated as the difference between the supermolecular energy and the bonded fragment energies are repulsive in the cyclophanes studied. The nature of this interaction is studied for groups of systematically extended doubled layered paracyclophane systems using the random‐phase approximation (RPA), two recently developed extensions to the RPA and standard density functional theory (DFT) methods including dispersion corrections. Upon a systematic increase in conjugation the strongly repulsive intramolecular interaction energy reduces and thus leads to an increase in the stability. Finally, existing experimental and theoretical estimates of the molecular strain are compared with the results of this work.     

Path Integral Liouville Dynamics Simulations of Vibrational Spectra of Formaldehyde and Hydrogen Peroxide

Formaldehyde and hydrogen peroxide are two important realistic molecules in atmospheric chemistry. We implement path integral Liouville dynamics (PILD) to calculate the dipole-derivative autocorrelation function for obtaining the infrared spectrum. In comparison to exact vibrational frequencies, PILD faithfully captures most nuclear quantum effects in vibrational dynamics as temperature changes and as the isotopic substitution occurs.     

用积分方程方法决定胶粒之间的空耗势

Binary components Ornstein-Zernike integral equation with the concentration of large particle component being set to zero was employed to study the depletion potential behavior between two large neutral colloid particles （modeled as hard spheres）immersed in a sea of small neutral solvent particles. The prediction for the depletion potential behavior compared well with simulation data and experimental data available in the literature. It is found that the Hansen-Verlet one phase criterion,based on the effective one component system with the present depletion potential,for the freezing transition is completely not suitable for the real binary components system. It is disclosed that the unsuitability is due to the volume term of the solid phase and liquid phase which can not be treated selfconsistently in the Hansen-Verlet one phase criterion.     

胞嘧啶…NO复合物结构与性质的理论研究

用密度泛函理论在BL3YP/6-311＋G*基组水平上对胞嘧啶…NO复合物体系进行了理论计算, 发现了6个能量极小的复合物. 其结合方式是NO的N或O原子与胞嘧啶的N—H键形成氢键, 最稳定的复合物的结合能为－9.65 kJ/mol. NO的N原子与胞嘧啶的结合具有更强的优势, N结合的复合物中NO的键长缩短, 而O结合的复合物中NO键长伸长. 同时, 对复合物的振动分析发现, 在胞嘧啶中所有的与NO结合的N—H键的伸缩频率下降, 而所有氨基的面内弯曲振动频率是增加的.     

Transport Properties from the Equation of State by Means of Enskog Theory for d-Dimensional Hard Spheres

Abstract

In this work we have used Enskog theory to evaluate transport properties in d-dimensional hard spheres. In order to carry out this study we have made use of the relation between the compressibility factor Z and the ratio X_E/X ₀, where X_E is the Enskog value for a transport property and X ₀ is that corresponding to a dilute gas. From the available numerical data for Z in simulation experiences, we have calculated the aforementioned ratio for the diffusion coefficient D, the shear viscosity coefficient η, the bulk viscosity coefficient η and the thermal conductivity coefficient λ. This calculation has been extended to hard disks (d = 2), hard spheres (d = 3) and hard hyperspheres (d = 4,5) in the maximum allowable range of densities. We have also tested the suitability of some algebraic equations of state proposed for such bodies by comparing their respective values for X_E/X ₀. Finally, we have obtained numerical values for the ratio D/D_E in the cases d = 4,5. The behavior is similar to that of hard spheres.     

Influence of polyelectrolyte and salt on the structure of dispersions containing charged colloidal particles

An integral equation theory has been used as the basis for studying the structure of dispersions containing charged colloidal particles: globular protein molecules with a nonzero dipole moment, a polyelectrolyte and a low-molecular salt. It is demonstrated that there is an effective attraction between charged colloidal particles, which increases in the presence of charged polymer chains. The influence of the length of polyelectrolyte chains and of salt concentration on the partial structure factor of colloidal particles was studied.     

ChemInform Abstract: Structure and Properties of the Sulfur Dinitride Dianion.

The properties of the N₂S^2- dianion are calculated using Hartree-Fock-Slater and MNDO methods.     

利用统计缔合流体理论状态方程预测混合气体水合物的平衡形成条件

利用统计缔合流体理论(SAFT)状态方程结合van der Waals-Platteeuw统计力学模型用于预测含有甲烷、乙烷、丙烷、乙烯、丙烯、H₂S, CO₂, N₂和H₂二元气体水合物的平衡形成条件. 对于气相和液相, 应用SAFT方程来描述. 在气相和液相相平衡的模拟过程中, SAFT方程考虑了硬球斥力、成链力、色散力以及缔合相互作用. 对于水合物相, 采用van der Waals-Platteuw模型来计算. 该方法的预测结果与实验数据吻合.     

SBA-15分子筛羟基结构性质及其催化活性的理论研究

采用密度泛函方法对SBA-15分子筛簇模型化合物进行了计算模拟,重点研究了簇模型化合物羟基的几何构型和电子结构性质。从键级、前线分子轨道、静电势和质子化能等方面探讨了表面羟基的酸碱及氧化还原性质。分子筛模型化合物的静电势图显示SBA-15分子筛表面孤立羟基的H原子为分子筛表面的L酸性位,而氢键羟基的O原子则为分子筛表面的B碱性位。分子筛的前线分子轨道研究发现,表面羟基是分子筛表面的氧化还原活性位。计算得到的羟基SiO-H键级及形成的氢键键级分别在0.677 5～0.710 5和0.055 7～0.092 6范围,计算羟基OH的质子化能在1 471～1 589 kJ.mol-1范围。考察分子筛表面的质子化能显示未参与形成氢键的羟基H质子具有较强的B酸性。     

The Influence of Pore Structures and Degree of Crosslinking on Catalytic Properties of Aminomethyl Polystyrene Resins Supported Dendritic Sn Complexes

Seven different aminomethyl polystyrene resins supported dendritic Sn complexes were prepared by solid phase synthesis methodology. All the synthesized complexes show promising catalytic activities for the Baeyer‐Villiger oxidation of ketones with hydrogen peroxide and affording the corresponding lactones or esters. The influence of different pore structures and the degree of crosslinking of the aminomethyl polystyrene resins on catalytic properties of the supported dendritic Sn complexes were well discussed.