纳米球在聚合物膜间的结构可控结晶

发布时间：2018-05-16 09:21

本文选题：聚合物纳米复合材料 + 分子动力学模拟　；参考：《浙江理工大学》2017年硕士论文

【摘要】：聚合物纳米复合材料有着区别于纯聚合物的更好的机械、力学及光学等性能,这使其在聚合物物理和材料科学领域受到了广泛关注。通常材料的宏观性能由其微观相所决定。聚合物纳米复合材料的宏观性能则主要由聚合物基质中纳米颗粒的分散情况所决定。因此为了能够有效控制聚合物纳米复合物的宏观性能,必须深入研究聚合物与纳米粒子之间的相互作用机制,分析探索纳米粒子在聚合物纳米复合体系中的相变化情况。由于阐明聚合物纳米粒子复合材料的各相的相互作用机制在实验和理论中较为困难,通过计算模拟的方法更有利于我们对聚合物纳米复合材料的研究。本文使用分子动力学模拟方法研究了局限在两平行硬板间的聚合物纳米粒子复合物体系,观察到了球形纳米粒子被扁平聚合物链修饰结构可控晶体现象。当局限复合体系纳米粒子的数目足够高,能显著干扰链的构象时,为了最小化熵损失,聚合物链取代纳米粒子在基底表面聚集。使纳米粒子的浓度远高于聚合物链的浓度会导致纳米粒子被夹于两个聚合物链的薄层之间,并在体系中心区域中形成有序排列。而由紧密关联团组成的聚合物链的标度模型的提供阐明了薄聚合物层的形成和纳米粒子的结晶背后的物理机制。通过调节聚合物链和纳米粒子的体积浓度,显示结晶的纳米粒子的有序结构是可调节的。同时,我们又通过分子动力学模拟测量了绝热体系中表面分离的纳米粒子在绝热聚合物间的间接相互作用力。由于熵效应,通过变化绝热体系中的聚合物浓度、聚合物链长及纳米粒子尺寸等条件,模拟证实了分离间距超出了吸引力范围的纳米粒子之间的排斥存在,且提高聚合物浓度或增大纳米粒子尺寸能使吸引力和排斥力单调增大。作为纳米粒子间分离间距的函数的间接相互作用力对半稀释聚合物的聚合物链长度没有依赖性,作用范围也仅受聚合物浓度的影响。最后,我们通过计算围绕纳米粒子的单体的径向分布函数证实了间接力的存在。通过本文研究,我们发现了局限复合体系下纳米粒子在聚合物膜间的结构可控结晶现象,并通过对纳米粒子二体间接作用力的计算分析了解到绝热复合体系中各相的相互作用机制,初步阐明了局限体系静态相结构形成的原因。模拟研究的结果也将使我们对于聚合物纳米复合体系中各相相互作用机制及其导致的相应相行为有了更加深入的了解和掌握。
[Abstract]:Polymer nanocomposites have better mechanical, mechanical and optical properties different from pure polymers, which have attracted wide attention in the field of polymer physics and material science. The macro properties of the materials are usually determined by their microscopic phases. The macro properties of the polymer nanocomposites are mainly from the nanocomposites in the polymer matrix. The dispersion of particles is determined. So in order to effectively control the macro properties of polymer nanocomposites, the interaction mechanism between polymer and nanoparticles must be deeply studied and the phase change of nanoparticles in the polymer nanocomposite system is analyzed and explored. The interaction mechanism of phase is more difficult in experiment and theory. The method of calculating simulation is more beneficial to the study of polymer nanocomposites. In this paper, the polymer nanoparticle complex system limited to two parallel hard plates is studied by molecular dynamics simulation, and the spherical nanoparticles are observed to be flat. Polymer chain modified structure controlled crystal phenomenon. When the number of limited composite nanoparticles is high enough to interfere with the conformation of the chain, the polymer chain is replaced by the nanoparticles on the substrate surface to minimize the entropy loss. The nanoparticle concentration is much higher than the concentration of the polymer chain, which will lead to two polymerization of nanoparticles. An orderly arrangement between the thin layers of the chain, and an orderly arrangement in the central region of the system. The scale model of the polymer chain composed of tightly connected groups illustrates the formation of the thin polymer layer and the physical mechanism behind the crystallization of the nanoparticles. The crystalline nanoparticles are displayed by adjusting the volume concentration of the polymer chains and nanoparticles. The ordered structure is adjustable. At the same time, we have also measured the indirect interaction force between the particles separated by the surface in the adiabatic system by molecular dynamics simulation. The entropy effect, by changing the polymer concentration in the adiabatic system, the length of the polymer chain and the size of the nanoparticles, has proved the separation. The attraction and repulsion can be increased monotonously by increasing the concentration of the polymer or increasing the size of the nanoparticles. The indirect interaction force, as a function of the separation space between the nanoparticles, has no dependence on the length of the polymer chain of semi diluted polymers and the scope of action. In the end, we confirm the existence of the inter force by calculating the radial distribution function of the monomer around the nanoparticles. Through this study, we found the structure controlled crystallization between the nanoparticles in the polymer film under the confined composite system and the calculation of the indirect force of the two body of the nanoparticles. The interaction mechanism of each phase in the adiabatic composite system is analyzed and understood. The reasons for the formation of the static phase structure in the limited system are clarified. The results of the simulation study will also make us understand and master the interaction mechanism and the corresponding phase behavior in the polymer nanocomposite system.

【学位授予单位】：浙江理工大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TB383.1;O643.36

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