高分子粗粒化分子动力学模拟进展

模拟与理论、实验相互补充,彼此验证,使我们在原子和分子尺度上理解相关实验现象中的微观物理机制。结合高性能计算机和计算技术的发展,模拟已发展成为独特的高分子科学研究手段,在高分子材料优化设计和性能与结构问的性能关系研究中起重要作用。高分子具有不同层次的结构,材料的性质和功能不仅取决于化学结构和分子性质,而且很大程度上取决...     

Phase behavior of amphiphiles at liquid crystals/water interface: A coarse-grained molecular dynamics study

We present a coarse-grained molecular dynamics simulation study of phase behavior of amphiphilic monolayers at the liquid crystal （LC）/water interface. The results revealed that LCs at interface can influence the lateral ordering of amphiphiles. Particularly, the amphiphile tails along with perpendicularly penetrated LCs between tails undergo a two-dimension phase transition from liquid-expanded into a liquid-condensed phase as their area density at interface reaches 0.93. While, the liquid-condensed phase of the monolayer never appears at oil/water interface with isotropic shape oil particles. These findings reveal the penetration of anisotropic LC can promote ordered lateral organization of amphiphiles. Moreover, we find the phase transition point is shifted to lower surface coverage of amphiphiles when the LCs have larger affinity to the amphiphile tails.     

聚合物接枝Janus纳米片形变的耗散粒子动力学研究（英文）

由于在检测、药物输运、分子马达等领域具有广阔的应用前景,二维柔性响应Janus材料受到了广泛的关注。但遗憾的是,这些二维材料的响应形变的分子机理仍不明确。基于此,我们采用介观尺度的耗散粒子动力学模拟方法系统研究了Janus纳米片两侧接枝不同长度和不同溶剂相容性的高分子链对Janus纳米片形变的影响。我们发现由于构象熵和混合焓的共同作用,通过对接枝链长度和溶剂相容性的调整,Janus纳米片可以形成如反相包覆、信封装包覆和碗状等新奇的结构。我们的理论结果首次提供了对二维柔性Janus材料可控形变的基本认识,并预报了设计合成新型Janus纳米器件在药物和生物医学领域的潜在应用。     

PE/PEO/PE-PEO 对称三元共混体系相行为的耗散粒子动力学模拟研究

建立了对应实验体系聚乙烯/聚氧化乙烯/聚乙烯-聚氧化乙烯嵌段共聚物(PE/PEO/PE-PEO)的对称三元共混模型,并采用耗散粒子动力学(DPD)模拟方法对其相行为进行了理论研究.研究结果表明,随着均聚物体积分数的增加,体系的平衡相态发生由层状相(LAM)到双连续微乳液(BME)再到相分离(PS)的转变,相态演化规律和...     

基于黏弹模型的聚合物溶液相分离的三维数值模拟

利用GPU加速技术实现黏弹模型的三维数值模拟,系统研究了中等浓度聚合物溶液的分相形貌和相分离动力学.模拟结果表明本体应力的不对称是体系出现相反转的重要原因.与实验观察的聚合物溶液相反转的演化过程一致,首先聚合物富集相形成网络结构,然后聚合物网络收缩断网,最后变为离散的液滴相.本体松弛模量的增加,一方面会抑制相分离初期的浓度涨落,导致相反转发生时间延迟;另一方面在相分离后期有助于形成大的聚合物富集液滴相,加速相区增长.剪切松弛模量的增加只有助于聚合物富集相保持网络结构,并在剪切松弛模量较大的情况下,不规则相结构的缓慢松弛导致了剪切应力在相分离后期长期存在.     

耗散粒子动力学研究片状双层——囊泡转变

片状双层是囊泡自发形成过程中的重要中间态，由片状双层向囊泡的转变机理一直未被认清．本文以磷脂分子DMPC作为模拟对象，采用普适性的粗粒化模型和耗散粒子动力学模拟方法，以体系粒子无序分布和无应力片状双层作为初态，对水溶液中片状双层——囊泡的转变过程进行了深入研究．发现尾-水粒子间憎水作用能最小化是片状双层卷曲形成囊泡的微观本质．囊泡的双分子层为二维流体．此外还得到了囊泡上粒子的位置分布和化学键排列取向等方面的结构信息．     

电导率对电流变效应的影响

通过实验和理论分析，证明电导率对直流电场下电流变效应的产生及对其大小的决定作用．电流变机制不仅包括体极化和界面极化过程，而且包括离子的双电层极化过程．低频或直流电场下，显著电流变效应的体系要求σ_p＞σ_f，且ε_p＞ε_f．适当地增大σ_f，提高离子层的静电作用，有利于提高电流变液体的流变性能，但这种做法应以不引起电流过大、焦耳热过多、电功输入过大为前提 关键词：     

ASYMPTOTIC BEHMIOR OF A CLASS OFNONLINEAR DIFFERENCE EQUATIONSOF nTH ORDER

IIntroductlonMuch work has been done on the asymptotlcbehavlor of*theotlcbehavlor second orderdl地rentlal equation．Some results oflt are based on the Integral Inequalities’of G。"wall－B＜bar＜type．Kong Qingkal[11 has studledthe behavior ofa classofnonllnear dl地rentlal equations ofnth order．Some people[2;3]h肌e studiedthe asymptotlc behavior of the second order nonlinear difference equations．Atpresent,papers about the asymptotlc behavior of nonlinear difference equatlons of nib order …     

The collapse of polyethylene rings on an attractive surface

Polymers exhibit extended structures at high temperatures or in good solvents and collapsed configurations at low temperatures or in poor solvents. This fundamental property is crucial to the design of materials, and indeed has been extensively studied in recent years. In this paper, the collapse of polyethylene rings on an attractive surface was investigated by using molecular dynamics simulations. It is found that the collapse of ring chains on the attractive surface is of distinct difference from their free counterparts, where the collapse becomes more continuous and a one-stage instead of two-stage collapse can be identified by the specific heat. Some hairpin-like crystal structures are found at low temperatures, which are induced by the adsorption interaction of polymer-surface. For a given chain length, the results were further compared with those of the adsorbed linear chains. Due to the topological constraint of ring chains, the number of hairpin structures is clearly less than that of the linear chains. These numerical simulations may provide some new insights into the folding of ring polymers under adsorption interactions.