超分子和高分子自组装的动力学模拟研究

超分子和高分子的自组装是发展新型高性能材料的有力手段.通过自组装构筑多级有序结构,从而显著提高材料的力学、光学或电学性能,是化学和材料科学研究的前沿.然而精确调控自组装需要深入理解范德华、氢键、静电、主客体复合和π-π等相互作用以及动力学机理所扮演的角色.计算机模拟,尤其是分子动力学模拟,为研究自组装结构和演化过程提供了独一无二的手段.本文主要阐述超分子和高分子的多尺度模型和动力学模拟方法,讨论不同模拟方法的特点、适用范围和优势;进一步简述我们发展的定制模型和方法,以及同时提高模型精度和计算效率方面采取的策略.通过总结应用这些方法对超分子和高分子自组装开展的研究工作所取得的进展,为进一步发展自组装动力学模拟方法提供参考.     

分子纳米技术与金属有机分子纳米体系

基于超分子自组装的分子纳米技术是一种新兴的高新技术。本文从金属矢量操纵的自组装分子纳米体系、自组装的纳米微反应器与超分子催化和自组装金属超分子高分子纳米材料等三个方面评述了分子纳米技术及其在构筑金属有机分子纳米体系中的发展现状 ,进一步阐述了“金属矢量”的概念 ,并首次提出建立“自组装子工具箱” ,探讨了分子纳米技术的发展方向。     

非等活性加核自缩合乙烯基聚合体系回转半径的Monte Carlo模拟

利用Monte Carlo模拟方法研究了加核自缩合乙烯基聚合反应体系中超支化高分子的二次回转半径随双键转化率的变化情况. 在模拟中, 重点考察了两类活性基团的反应活性差异、 引发核的配比及基团数等因素对超支化高分子均方回转半径的影响. 结果表明, 上述因素对于超支化高分子的尺度有着显著影响, 从而可为调控体系中高分子的空间尺度提供有效途径.     

金纳米粒子和聚合物复合体系分子设计与组装过程的计算机模拟

金纳米粒子除了拥有纳米粒子的体积效应、表面效应、量子尺寸效应、宏观量子隧道效应等优异性能之外,还有一些特殊性能,如良好的稳定性、抗菌抑菌功能、表面吸收带效应、荧光效应等。量子化学计算方法提供了从分子水平上探究金团簇的催化和反应活性的影响因素,如金团簇的尺寸、形状、电子状态、活性位点的类型和结构等。分子动力学可以更好地模拟纳米粒子与配体和溶剂的相互作用方式,同时给出热力学和动力学行为。耗散粒子动力学等介观模拟方法则被应用到金纳米粒子和聚合物复合体系自组装过程的研究,并可以给出调控自组装结构的有效方案。以高分子与纳米粒子复合物为研究对象,明晰影响复合物结构和性质的主导因素,探索复合物调控机制,提出决定复合物功能的主控因素,进一步理解高分子与纳米粒子复合物的本质,可以为实验上制备、优化新型高分子与纳米粒子复合物材料提供可靠的理论帮助。     

甲壳型液晶高分子研究进展与展望

简要介绍了甲壳型液晶高分子的模型理论, 概述了当前国内外对甲壳型液晶高分子设计、 液晶相态、 性质及基于甲壳型液晶高分子的嵌段共聚物体系的设计和自组装性质等研究进展, 展望了今后的研究方向.     

耗散粒子动力学与可极化ABEEM力场结合模拟嵌段共聚物自组装形态调控

本文采用介观尺度上的耗散粒子动力学与基于ABEEM可极化力场的全原子分子动力学相结合的方式,从理论上探究了嵌段共聚物结构、对称性、分子组成及温度等对嵌段共聚物最终自组装结构形态的影响.模拟结果表明,这些因素均会对嵌段共聚物在选择性溶剂中的最终自组装结构产生一定影响.这一理论研究为实现可控操纵自组装结构,提供了有意义的参考.     

分子组装理论基础的探究——现状与机遇

分子组装是在分子以上层次创造新物质、产生新功能的重要手段.提升分子组装过程的可控性和组装体功能性是该领域的核心目标,但由于研究复杂分子组装体系的手段和理论的匮乏,迄今绝大部分研究只能限于了解组装过程始末的“黑箱”模式,这成为该领域的发展瓶颈之一.本文围绕分子到亚细胞层次的分子组装体系及其理论方法与模型,尝试将物质、能量与信息作为度量分子组装研究复杂性的三个维度,从简单到复杂地逐级剖析探讨分子组装的理论研究现状、机遇和突破口.首先,在物质维度上揭示分子组装过程呈现多路径、多阶段和多尺度等复杂性;进而在物质基础上引入能量维度,阐明熵驱动或熵焓互补现象普遍存在于分子组装体系中,并探讨远离平衡态的分子组装体系如何产生时空有序的功能耗散结构;继而在物质与能量基础上引入信息维度,探讨分子组装信息网络中的正、负反馈协同,以及如何促使系统涌现出复杂的生理功能.为了突破分子组装理论研究的瓶颈,似乎亟需建立更大的框架.从物质、能量和信息的三个维度协同研究,有望系统深入认知组装规律,进而建立新理论,发展高效精准的调控手段,提升分子组装体系的复杂性和功能性,并可能为生命科学和软物质科学提供新视角和新方法.     

氮杂环高分子化合物的电催化性能进展

介绍了氮杂环高分子配合物及其电催化性能,归纳了含氮杂环高分子配合物的结构类型及其在界面上的自组装过程,分析了氮杂环高分子自组装膜表面化学反应的特性。对自组装技术制备超薄层材料及表面改性技术在分子电子器件等方面的应用作了评述。     

表面活性剂溶液行为的粗粒化模拟

分子动力学模拟技术目前已经成为了研究表面活性剂有序聚集体的不可或缺的工具之一。近几年来,粗粒化模拟方法克服了传统的介观模拟和精细力场模拟的缺点,既能够重现自组装体系的热力学或者结构方面的信息,又极大地拓展了模拟体系所能达到的空间和时间尺度,逐渐成为了计算领域的一个热点。本文综述了近几年来表面活性剂粗粒化分子动力学模拟的最新发展状况,分别就不同粗粒化模型的建模策略、作用势能表达、参数拟合和模型评价等问题作了详细的介绍,并通过实例说明了粗粒化力场对表面活性剂体系的适用性。在此基础上,指出了发展粗粒化力场过程中所面临的一些关键性问题,这对于表面活性剂溶液行为的粗粒化模拟具有重要的意义。     

聚二烯丙基二甲基氯化铵在质子交换膜表面静电自组装过程的热力学研究

本文通过热化学方法设计了PDDA滴定质子交换膜,并研究了高分子的静电自组装过程。通过非线性拟合数据分析,求出了自组装过程的焓变（ ）和结合常数（K）。根据该反应过程中的热力学参数,可知自组装过程是“焓驱动”反应。热量的放出代表着能量的降低,有利于反应的发生;而自由度的减小不利于反应的发生。对于每个离子键的形成,单分子DDA的焓变超过了PDDA,这是因为小分子能够更加自由地结合到膜上,而高分子PDDA有一定的位阻效应。     

SnO2 meso-scale tubes: One-step,room temperature electrodeposition synthesis and kinetic investigation for lithium storage

SnO₂ meso-scale tubes were synthesized by anodic electrochemical deposition under ambient conditions. Controlled self-bubbling O₂ acted as both the template and the oxidizing agent for obtaining SnO₂ tube structures at the interface of the gas (O₂) and the liquid (electrolyte). Electrochemical testing showed that the meso-scale tubes have higher discharge capacity and better rate capability than the “microbowls” produced by varying the deposition conditions. From the Arrhenius plot, the apparent activation energies were calculated to be 58.4 and 90.1 kJ mol^?1 for the meso-scale tubes and the microbowls, respectively, indicating that the meso-scale structure allows shorter diffusion routes for the lithium ions or for easier interaction with lithium.     

Theoretical study on self-assembly in organic materials

Theoretical work related to the self-assembly of organic materials was dealt with, and the various mechanisms leading to self-assembly, such as transition metal mediated self-assembly, constraint induced self-assembly, covalent bond based self-assembly and van der Waals interaction driven self-assembly, etc., were discussed. The formation of ordered structures could be attributed to the competition between short range attractive forces and long-range repulsion, which was arising from dipole interaction or may result from a different mechanism based on a purely repulsive isotropic short-range pair potential with two characteristic length scales. Such mechanism could be exploited in the study of self-assembly process. First principles SAPT(DFT) interaction energy calculations, combined with the Williams-Stone-Misquitta method, offer the ability to improve the molecular dynamics (MD) accuracy which could in turn be used in the prediction of crystal structures and self-assembly tendency. The combination of experimental and theoretical studies could open new breakthroughs over the design, synthesis, and characterization of self-assembled materials.     

多肽自组装技术及其在生物医学上的应用

多肽分子自组装广泛存在于自然界中。多肽具有良好的生物相容性和可调控的降解性能,并且利用多肽自组装技术,可以在分子水平上设计并调控聚集态的形状和结构,这在生物医学材料方面具有巨大的应用潜力。近年来关于多肽自组装的研究成为材料学、医学等领域中研究热点之一,并且在药物缓释载体、组织工程支架研究方面取得进展。本文介绍多肽分子自组装技术的概念,综述了多肽自组装技术在药物缓释载体材料、组织工程支架材料方面的应用。     

Amplification of Electronic Circular Dichroism—A Tool to Follow Self-Assembly of Chiral Molecular Capsules

Electronic circular dichroism (ECD) can be used to study various aspects of self-assembly (definition of stoichiometric ratios, chirality amplification during self-assembly, host-guest complexation). In this work, we show that ECD is a valuable tool for monitoring the self-assembly of chiral peptide-based capsules. By analyzing the signs, intensities, and temperature dependences of ECD bands, the effects of the non-specific processes can be separated from the restriction of intramolecular motion (RIM) caused by discrete self-assembly. Analysis of experimental and theoretical ECD spectra show that the differences between assembled and non-assembled species originate from induction of inherently chiral conformation and restriction of conformational freedom that leads to amplification of ECD signals during self-assembly of discrete species.     

Lyotropic liquid crystal engineering-ordered nanostructured small molecule amphiphile self-assembly materials by design

Future nanoscale soft matter design will be guided to a large extent by the teachings of amphiphile (lipid or surfactant) self-assembly. Ordered nanostructured lyotropic liquid crystalline mesophases may form in select mixtures of amphiphile and solvent. To reproducibly engineer the low energy amphiphile self-assembly of materials for the future, we must first learn the design principles. In this critical review we discuss the evolution of these design rules and in particular discuss recent key findings regarding (i) what drives amphiphile self-assembly, (ii) what governs the self-assembly structures that are formed, and (iii) how can amphiphile self-assembly materials be used to enhance product formulations, including drug delivery vehicles, medical imaging contrast agents, and integral membrane protein crystallisation media. We focus upon the generation of 'dilutable' lyotropic liquid crystal phases with two- and three-dimensional geometries from amphiphilic small molecules (225 references).     

自组装的分子动力学模拟

简要回顾了近年来国内外分子动力学模拟自组装的研究,对已报道的建模方法、可视化表现以及相关应用略作概述,并以此为基础对自组装过程的分子动力学模拟研究所面临的问题和尚需深入的内容进行了讨论。基于自组装、相变和涨落的固有联系,提出了以研究波动为手段,和以频率相关热容为研究对象的探索方向。希望能够为分子动力学模拟推动自组装研究提供有益的参考。     

Molecular dynamics studies to understand the mechanism of heat accommodation in homogeneous condensing flow of carbon dioxide

Using molecular dynamics (MD), we have studied the mechanism of heat accommodation between carbon dioxide clusters and monomers for temperatures and cluster size conditions that exist in homogeneous condensing supersonic expansion plumes. The work was motivated by our meso-scale direct simulation Monte Carlo and Bhatnagar-Gross-Krook based condensation simulations where we found that the heat accommodation model plays a key role in the near-field of the nozzle expansion particularly as the degree of condensation increases [R. Kumar, Z. Li, and D. Levin, Phys. Fluids 23, 052001 (2011)]. The heat released by nucleation and condensation and the heat removed by cluster evaporation can be transferred or removed from either the kinetic or translational modes of the carbon dioxide monomers. The molecular dynamics results show that the time required for gas-cluster interactions to establish an equilibrium from an initial state of non-equilibrium is less than the time step used in meso-scale analyses [R. Kumar, Z. Li, and D. Levin, Phys. Fluids 23, 052001 (2011)]. Therefore, the good agreement obtained between the measured cluster and gas number density and gas temperature profiles with the meso-scale modeling using the second energy exchange mechanism is not fortuitous but is physically based. Our MD simulations also showed that a dynamic equilibrium is established by the gas-cluster interactions in which condensation and evaporation processes take place constantly to and from a cluster.     

The gas–liquid tunable self-assembly properties of rod–coil diblock copolymer: donor–acceptor alternating structure served as rod segment

The rod–coil diblock copolymers in which the donor–acceptor alternating structures served as the rod segment were synthesized. The supramolecular self-assembly property of the copolymers was investigated in the methanol atmosphere. By changing the assembly condition, well-defined vesicles and porous films were produced, respectively. Pores with different size dispersions were obtained by tuning the methanol atmosphere. Moreover, porous films were also decorated on diverse substrates with nonplanar structures. The investigation on self-assembly properties of this rod–coil copolymer is the complementarity to the self-assembly of rod–coil copolymers. This is a very useful self-assembly method that can be used to prepare the self-assembly nanostructures with donor–acceptor alternating copolymers.     

纳米材料的自组装研究进展

本文主要评述了近年来纳米材料自组装的研究进展，即对以纳米材料(包括零维的纳米粒子和一维的纳米管/线)为单元而开展的自组装方面的工作进行了介绍。将纳米材料自组装为各种尺度的有序结构会产生更优异的整体的协同性质，这对于以纳米材料为基础而构筑的微纳米器件有着重要的意义。由于目前纳米材料的研究主要集中在零维和一维体系，因此，本文分别就此两种体系的自组装行为进行了评述。具体内容包括：单分子层薄膜修饰的无机纳米粒子的自组装、大分子修饰的无机纳米粒子的自组装、未被修饰的无机纳米粒子的自组装；表面张力及毛细管力诱导的一维纳米材料的自组装、模板诱导的一维纳米材料的自组装、静电力诱导的一维纳米材料的自组装。     

Study of Organic Self-Assembled Nanosystems by Means of High-Frequency ESR/ENDOR: The Case of Oil Asphaltenes

An approach to investigate self-assembly of oil disperse systems based on high-field electron nuclear double resonance has been suggested. As exemplified by asphaltenes, the oil components most prone to self-assembly, the formation of planar rather than multilayer structures has been directly evidenced experimentally. The suggested method can be applied to elucidate the self-assembly mechanism in wide range of organic objects.