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用分子模拟方法对近来关于在屈服中是否存在结构改变的问题进行了考察,结果表明,在屈服附近键长与键角没有明显的变化,而且分子间相互作用主宰着屈服过程,研究发现,屈服过程中有一个“原子跳跃”的结构转变现象,即部分原子的位移超出所有原子平均位移的10倍以上,另外,高分子键间堆砌的复杂性引起屈服点附近的多的子跳跃发生。用该结果可以较合理地解释高分子有一个宽的屈服峰。 相似文献
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本文综述了近年来国际上对晶态聚合物结构研究的几个活跃问题,内容包括高分子折叠链,结晶-非晶中间层,晶态聚合物的形变机理,聚合物附生结晶。并简要介绍了各种实验技术及方法在这方面的研究结果。 相似文献
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本文基于位置有序参数(SOP)分析了利用图形处理器(GPU)加速的分子动力学程序GMD模拟含有4.5万和36万个CH2联合原子的聚乙烯纳米球的分子动力学结晶过程中结晶度的变化,并使用Avrami方程得到了不同温度下的结晶指数.与一般实验结果相同,该指数n不为整数.我们提出了二元混合模型,认为纳米线团的结晶行为由两种机理按一定比例组成.当结晶温度升高时,两种尺寸的纳米线团的Avrami指数均升高并接近4,结晶机理趋向三维生长和均相成核.当温度低时,晶核多在接近纳米球的表面生成,Avrami指数趋近于1.我们对体系结晶成核阶段结束时晶核沿纳米球的径向分布进行了分析.结果表明Tn=0.60时晶核的生成位置接近表面,而Tn=0.68时晶核出现一个接近纳米球内部的峰.该结果与二元混合模型的Avrami指数的分析结果相吻合. 相似文献
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液态金属结构变化的分子动力学模拟研究 总被引:1,自引:0,他引:1
随着计算机技术的飞速发展,已有可能将分子动力学方法应用于液态金属微观结构组态瞬时变化的定量模拟研究,使这一极为复杂的微观过程呈现出一幅十分清晰的物理图象,并已取得了许多重要的成果[1-4].本文在作者原有工作的基础上[2-4],对液态金属Al的结构变化进行了分子动力学计算机模拟研究,得到一幅非常清晰的关于金属熔融后继续升温过程中结构组态如何逐步变化的图景:随着温度的升高,其与高有序度相关的键型数目越来越少,而与无序度相关的键型数目却不断增加,即系统的总趋势是无序度增加.但却发现,即使在达到1773K(1.9… 相似文献
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点击反应由Sharpless提出,是一类具有高效、可靠、高选择性等特点的反应,被广泛用于各种拓扑结构聚合物的制备.目前,应用较为广泛的点击反应主要有Cu(I)催化的叠氮/炔环加成反应(CuAAC)、Diels-Alder(D-A)反应、巯基-烯及巯基-炔点击反应和氮氧自由基偶合反应.近年来,将多种点击反应结合起来,为高效合成拓扑结构聚合物提供了新的思路.本文综述了近几年来采用多重点击反应策略联用制备拓扑结构聚合物的研究进展,并对其发展趋势进行展望. 相似文献
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高分子熔体结晶的两维计算机模拟胡文兵,于同隐,卜海山(复旦大学高分子科学系,复旦大学材料科学系,上海,200433)关键词计算机模拟,有序相变,高分子1956年Flory[1]从平均场近似的格子模型证明:高分子链的非柔顺性会导致长链的完全有序排列.此... 相似文献
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针对聚合物纳米复合材料,系统综述了计算机模拟技术(分子动力学模拟)在纳米颗粒的分散与聚合物-纳米颗粒界面作用取得的成果与进展,包括不同形状纳米颗粒在聚合物基体的分散机理、相行为与微观结构、纳米颗粒对分子链构象的影响(分子链均方回转半径的变化)、分子链在纳米颗粒表面结构(取向与排列)、分子链与纳米颗粒界面作用能、界面区分子链活动性与纳米颗粒形成的网络结构.为构建聚合物纳米复合材料的组成、结构与性能之间的关系,提出了3个模拟方面的挑战,包括发展长时间跨尺度计算机模拟技术、建立准确模拟材料力学性能的方法与导电导热功能性的模拟. 相似文献
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Monte Carlo Simulation of Coil-to-Globule Transition of Compact Polymer Chains: Role of Monomer Interacting 下载免费PDF全文
Coil-to-globule transitions are fundamental problems existing in polymer science for several decades; however, some features are still unclear, such as the effect of chain monomer interaction. Herein, we use Monte Carlo simulation to study the coil-to-globule transition of simple compact polymer chains. We first consider the finite-size effects for a given monomer interaction, where the short chain exhibits a one-step collapse while long chains demonstrate a two-step collapse, indicated by the specific heat. More interestingly, with the decrease of chain monomer interaction, the critical temperatures marked by the peaks of heat capacity shift to low values. A closer examination from the energy, mean-squared radius of gyration and shape factor also suggests the lower temperature of coil-to-globule transition. 相似文献
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Polymers are widely used in our daily life and industry because of their intrinsic characteristics, such as multi-functionality, low cost, light mass, ease of processability, and excellent chemical stability. Polymers have multiscale space-time properties, which are mainly reflected in the fact that the properties of polymer systems depend not only on chemical structure and molecular properties, but also to a large extent on the aggregation state of molecules, that is, phase structure and condensed state structure. Thanks to the continuous development of simulation methods and the rapid improvement of scientific computation, computer simulation has played an increasingly important role in investigating the structure and properties of polymer systems. Among them, coarse-grained dynamics simulations provide a powerful tool for studying the self-assembly structure and dynamic behavior of polymers, such as glass transition and entanglement dynamics. This review summarizes the coarse-grained models and methods in the dynamic simulations for polymers and their composite systems based on graphics processing unit(GPU) algorithms, and discusses the characteristics, applications, and advantages of different simulation methods. Based on recent studies in our group, the main progress of coarse-grained simulation methods in studying the structure, properties and physical mechanism of polymer materials is reviewed. It is anticipated to provide a reference for further development of coarse-grained simulation methods and software suitable for polymer research. 相似文献
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He-Bei Gao Hong Li Xiao-Qin Zhang Xiang-Hong Wang Chao-Yang Li Meng-Bo Luo 《高分子科学》2021,39(2):258-266
In this work, Monte Carlo simulations are used to study the critical adsorption behaviors of flexible polymer chains under the action of an external driving force F parallel to an attractive flat surface. The critical adsorption temperature T_c decreases linearly with increasing F,indicating that the driving force suppresses the adsorption of polymer. The conformation of polymer is also affected by the driving force.However, the effect of F is dependent on the competition between the driving force and temperature. Under strong force or at low temperature,the polymer is stretched along the direction of the force, while under weak force or at high temperature, the polymer is not stretched. When the force is comparable to the temperature, the polymer may be stretched perpendicular to the driving force, and below T_c, we observe conformational transitions from parallel to perpendicular and again to parallel by decreasing the temperature. We found that the perpendicular stretched conformation leads the polymer chain to synchronously move along the direction of the driving force. Moreover, the conformational transitions are attributed to the competition and cooperation between the driving force and the temperature. 相似文献
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从计算模拟及实验角度系统总结了聚合物结构、聚合物构象、聚合物扩散及聚合物多尺度动力学的研究进展,阐述了各影响因素及其变化规律,并对聚合物动力学的未来研究进行了展望. 相似文献
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Chen-guang Xu Tai-ning Liang Juan Sun Xiao-zhen Yang State Key Laboratory of Polymer Physics Chemistry Center for Molecular Science Institute of Chemistry Chinese Academy of Sciences Beijing China 《高分子科学》2001,(5):527-529
A better understanding of a recently raised argument on whether there occurs a structure change during yieldinghas been acquired by using molecular simulation. That is, when monitoring the displacements of all atoms before and afterthe yield, a structure transition does occur, which is the "atomic jump" that coordinates the amount of the atoms in thepolymer and makes a large step beyond~0.05 nm for all those atoms. Results indicate that the complex of polymer chainpacking induces the multiple atomic jumps around the yield point. This explains why polymers have a broader yielding peak. 相似文献
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高分子结构是高分子性能的重要物质基础,对其结构进行合理的划分,有助于准确把握高分子物理知识体系的内在脉络。高分子结构层次的划分不仅要思考静态时特定质点在空间的堆砌特征,而且也要考虑结构出现运动或是变化的基本单元。按照质点尺度的不同,高聚物的结构可以分为单一高分子结构(链结构)、多个高分子结构(凝聚结构)和多种高分子结构(织态结构)三个主要层次。其中,化学因素所确定的链结构层次包括相对分子质量以及构造、构型等同分异构体形式;物理因素所确定的结构层次为高分子局部质点集合在空间的堆砌和排列;链段是容易被忽视、但又是最为重要的运动(变化)单元。 相似文献