Comparison of surface properties of random, block, and graft copolymers having perfluoroalkyl and silicone-containing side chains

Fluorosilicone copolymers of random, block, and graft with both perfluoroalkyl and silicone-containing side chains were synthesized, and their surface properties and surface modification effects on PVC film were compared. It can be confirmed that the fluorosilicone copolymers of random, block, and graft exhibit very low surface free energies of 9-13 dyn/cm, depending on the perfluoroalkyl group content and their molecular structure. The inherent surface free energies of the fluorosilicone copolymers are significantly influenced by their molecular structure and perfluoroalkyl group content. It can also be found that the fluorosilicone copolymers are very effective for lowering surface free energy. The surface free energy of a copolymer/PVC blend strongly varies with perfluoroalkyl group content as well as molecular structure. The molecular structure of a fluorosilicone copolymer is as important as the perfluoroalkyl group content for their inherent surface free energies and surface modification of other polymers.     

脂肪醇的味阈值与分子结构之间的定量关系

通过拓扑方法探讨了脂肪醇的味阈值与分子结构之间的关系,发现脂肪醇的味阈值主要取决于分子的大小和羟基在分子中的位置(且羟基的位置对味阈值的影响十分显著),提出一个既能表征脂肪醇结构与味阈值之间关系、又能预测味阈值的定量关系式,发展了一种设计具有特定味阈值的脂肪醇分子结构的方法。对99种脂肪醇的计算结果表明,味阈值预测值与计算值与实验值的一致性令人满意。     

纳米自组装聚电解质超薄多层膜

相反电荷的聚电解质在溶液中通过静电相互作用自组装形成超薄多层膜，这种膜的结构可实现分子水平上的控制。就其复合、结构及其影响因素、以及应用进行了概述。     

Molecular structure calculations without clamping the nuclei

A number of recent papers have considered ways in which molecular structure may be calculated when both the electrons and the nuclei are treated from the outset as quantum particles. This is in contrast to the conventional approach in which the nuclei initially have their positions fixed and so merely provide a potential for electronic motion. The usual approach is generally assumed to be justified by the 1927 work of Born and Oppenheimer. In this paper we discuss what precisely might be anticipated in the way of molecular structure from a mathematical consideration of the spectral properties of the full Coulomb Hamiltonian, to what extent the very idea of molecular structure might be dependent upon treating the nuclei simply as providing a potential and the extent to which the work of Born and Oppenheimer can be used to support this position.     

Atomic Force Microscopy for Molecular Structure Elucidation

Using scanning probe microscopy techniques, at low temperatures and in ultrahigh vacuum, individual molecules adsorbed on surfaces can be probed with ultrahigh resolution to determine their structure and details of their conformation, configuration, charge states, aromaticity, and the contributions of resonance structures. Functionalizing the tip of an atomic force microscope with a CO molecule enabled atomic‐resolution imaging of single molecules, and measurement of their adsorption geometry and bond‐order relations. In addition, by using scanning tunneling microscopy and Kelvin probe force microscopy, the density of the molecular frontier orbitals and the electric charge distribution within molecules can be mapped. Combining these techniques yields a high‐resolution tool for the identification and characterization of individual molecules. The single‐molecule sensitivity and the possibility of atom manipulation to induce chemical reactions with the tip of the microscope open up unique applications in chemistry, and differentiate scanning probe microscopy from conventional methods for molecular structure elucidation. Besides being an aid for challenging cases in natural product identification, atomic force microscopy has been shown to be a powerful tool for the investigation of on‐surface reactions and the characterization of radicals and molecular mixtures. Herein we review the progress that high‐resolution scanning probe microscopy with functionalized tips has made for molecular structure identification and characterization, and discuss the challenges it will face in the years to come.     

Field-free molecular alignment control by phase-shaped femtosecond laser pulse

In this paper, we theoretically show that the field-free molecular alignment can be controlled by shaping the femtosecond laser pulse with a periodic phase step modulation, involving the maximum degree and temporal structure of the molecular alignment. We show that the molecular alignment can be completely suppressed or reconstructed as that by the transform-limited laser pulse, the temporal structure of the alignment transient can be controlled with a desired shape, and the molecular alignment and antialignment for any temporal structure can be switched. Furthermore, we also show that both the degree and direction of the molecular alignment at a fix time delay can be continuously modulated.     

不同分子环境中甲基的电负性研究

建立了不同分子环境中甲基中心碳原子电负性的计算模型, 计算了一些常见的CH~3-Z分子模型中甲基中心碳原子的电负性。结果表明:不同分子环境中的甲基具有不同的诱导效应参数, 该参数表现出规律性, 并可用于结构-性能的相关分析。     

Nanofabrication with metal containing dendrimers

Dendrimers are versatile building blocks for "bottom-up" nanofabrication because they combine molecular structure and nanoscale dimensions. Moreover, dendrimers can be functionalized at their numerous peripheral end groups, in their core, along their branches, and in the voids of their interior. This Frontier highlights the potential of metal containing dendrimers for nanofabrication.     

高效液相色谱质谱质谱法分析人参皂甙

 以反相高效液相色谱法分离了 9种人参皂甙。操作条件为乙腈 水梯度洗脱 ,二极管阵列检测器检测并在2 0 2nm下提取色谱图。利用三级四极杆质谱研究了 9种人参皂甙的一级质谱 (主要给出相对分子质量信息 )和二级质谱 (提供碎片结构信息 )。通过它们质谱图的差异对其进行了鉴别 ,并将方法用于实际样品中的 9种人参皂甙的定性。     

Incorporation and manipulation of coronene in an organic template structure

A two-dimensional molecular template structure of 1,3,5-benzenetricarboxylic acid (trimesic acid, TMA) was formed on a highly oriented pyrolytic graphite surface (HOPG) by self-assembly at the liquid-solid interface. Scanning tunneling microscopy (STM) investigations show high-resolution images of the porous structure on the surface. After the host structure was created, coronene molecules were inserted as guest molecules into the pores. STM results indicate that some of the guest molecules rotate inside their molecular bearing. Further investigations show that single coronene molecules can be directly kicked out of their pores by means of STM.     

茂金属聚乙烯分子链流变学模型研究进展

茂金属聚乙烯的分子链长支化结构对其流变特性有重要影响，长支链可以使熔体弹性和剪切变稀效应明显增强。本文介绍了茂金属聚乙烯分子链模型建立的理论依据，从流变学角度综述了近年来茂金属聚乙烯分子链结构模型的研究进展，阐述了有关的长链支化结构模型及其与流变性能的关系。     

Self-assembly of 1-D organic semiconductor nanostructures

This review focuses on the molecular design and self-assembly of a new class of crowded aromatics that form 1-D nanostructures via hydrogen bonding and pi-pi interactions. These molecules have a permanent dipole moment that sums as the subunits self assemble into molecular stacks. The assembly of these molecular stacks can be directed with electric fields. Depending on the nature of the side-chains, molecules can obtain the face-on or edge-on orientation upon the deposition onto a surface via spin cast technique. Site-selective steady state fluorescence, time-resolved fluorescence, and various types of scanning probe microscopy measurements detail the intermolecular interactions that drive the aromatic molecules to self-assemble in solution to form well-ordered columnar stacks. These nanostructures, formed in solution, vary in their number, size, and structure depending on the functional groups, solvent, and concentration used. Thus, the substituents/side-groups and the proper choice of the solvent can be used to tune the intermolecular interactions. The 1-D stacks and their aggregates can be easily transferred by solution casting, thus allowing a simple preparation of molecular nanostructures on different surfaces.     

单核锰配合物对几类氧化-还原酶的功能模拟

金属锰存在于多种氧化-还原酶中。其中,锰超氧化物歧化酶(Mn Superoxide Dismutase)及锰过氧化物酶(Mn Peroxidase)活性中心的锰结合位点,根据其结构特征,可将其视为精巧的单核锰配合物,因而人们通常以小分子配合物来模拟酶活性中心的结构及功能;另外,细胞色素P450是一种能够催化烯烃环氧化等诸多反应的单加氧酶,某些单核锰配合物能够起到与其类似的催化氧化效果。本文介绍了几类氧化-还原酶的结构特征和催化机理,总结了以小分子锰配合物作为酶功能模拟物的研究进展。     

Molecular interactions in one-dimensional organic nanostructures

Intermolecular interactions involving pi-pi interaction and hydrogen bonding are used to create one-dimensional molecular nanostructures of hexasubstituted aromatics. Site-selective steady state fluorescence, time-resolved fluorescence, scanning electron microscopy, and atomic force microscopy measurements detail the intermolecular interactions that drive the aromatic molecules to self-assemble in solution to form well-ordered columnar stacks. These nanostructures, formed in solution, vary in their number, size, and structure depending on the solvent used. In addition, our results indicate that the substituents/ side groups and the proper choice of the solvent can be used to tune the intermolecular interactions. The 1D stacks and their aggregates can be easily transferred by solution casting, thus allowing a simple preparation of molecular nanostructures on different surfaces.     

红外光谱法研究LB膜中的分子取向

The structure information of orientation and packing of molecular chains can be obtained from infrared transmission and reflection-absorbance (RA) spectra. In the present paper, on the basis of Umemura et al., their FORTRAN program of minicomputer was developed and can be run on 486 personal computer. By comparison of infrared transmission and RA intensities, surface enhancement factors and molecular orientation angle were calculated using the above program, and the influence of complex refractive index, angle of incidence, and thickness of LB film were discussed. These results are consistent with that of Umemura et al.     

Creation of chiral adsorbed structures using external inputs: results from lattice Monte Carlo simulations

Patterning of solid surfaces with organic molecules has been recognized as a promising method to create functional 2D matrices with tunable structure and properties. In this work we use the lattice Monte Carlo simulations to study chiral pattern formation in adsorbed systems comprising simple molecular building blocks differing in shape. To that end we consider five-membered rigid isomers whose composite segments can occupy vertices of a triangular lattice and interact with short-range (nearest neighbors) forces. Our main focus is on those molecules which are prochiral, that is they can adopt mirror-image planar configurations when adsorbed. Moreover, the effect of orientational in-plane confinement of the molecules, which reflects their coupling with an external directional field, on the structure formation and chiral resolution in 2D is explored. The obtained results demonstrate that the confinement imposed on the surface enantiomers can induce their resolution and formation of extended homochiral domains. However, it is also shown that for certain molecular shapes the confinement can produce mixed racemic crystals instead of the homochiral assemblies. The insights from our simulation studies can be helpful in preliminary screening of molecular libraries to select optimal building blocks able to self-assembly into chiral 2D patterns with predefined architecture.     

Characterization of synthetic polyelectrolytes by capillary electrophoresis

Capillary electrophoresis in entangled polymer solutions was applied to determine the molecular mass and polydispersity of polyelectrolytes. The separation selectivities of different polyethylene glycols as buffer additive can be correlated to their average molecular mass. A universal curve correlating the selectivity and the molecular mass could be obtained by using the instrinsic viscosity of the polyethylene glycol. The separation of poly(2-vinylpyridine) standards was compared to the separation of poly(4-vinylpyridine) standards. An indirect detection system was developed to characterize the cationic polyelectrolyte polydiallyldimethyl ammonium chloride. Various polymers with oppositely charged groups (polycarboxybetaines) were investigated with respect to structure dependence, pH dependence and molecular mass dependence of interand intramolecular association.     

Issues in the synthesis of crystalline molecular sieves: towards the crystallization of low framework-density structures.

Fundamental and practical interest in crystalline, microporous, molecular sieves is largely a direct consequence of the fact that their bulk properties can be manipulated through variations in atomic structure. This correspondence between the macroscale and the atomic scale is due to the uniformity of these crystalline materials. Control of the atomic structure therefore is of extreme importance, and is the thesis of this Review. Synthesis mechanisms and the parameters that can direct the crystal assembly pathway and the ultimate product formed are discussed and rationalized.     

对无环分子编码的一个新方法：CMP法

By the use of ordering-tree and connectivity matrix, a new algorithm to code non-circle molecules, called connectivity matrix polynomial (CMP) algorithm, is developed. The algorithm can not only differentiate asymmetrical atoms. but also make the two-direction mapping between codes and non-circle molecular structures. That is, from the molecular structure, a unique code can be obtained, and from the unique code, the specific molecular structure can be derived