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Entanglements and glass transition in polymer blends

聚合物共混物中的缠结和玻璃化转变

基本信息

批准号：
EP/H016686/1
负责人：
Alexei Likhtman
金额：
$ 34.35万
依托单位：
University of Reading
依托单位国家：
英国
项目类别：
Research Grant
财政年份：
2010
资助国家：
英国
起止时间：
2010 至无数据
项目状态：
已结题

来源：
https://gtr.ukri.org/projects?ref=EP%2FH016686%2F1
关键词：
Entanglements glass transition polymer blends

项目摘要

Everybody is surrounded by polymeric materials - modern life would not be possible without them. Typical polymer materials consists of two or more different polymers. As a blend has many degrees of freedom to play with, this, in principle, allows the material designer to tweak the material properties to his needs. Therefore a knowledge of the physics behind these materials is highly desired. Both mechanical and flow properties of typical polymeric melts are dominated by two phenomena: entanglements and glassy effects. The theory of entanglements attempts to describe the fact that long polymer chains can not pass through each other. This fact seriously reduces chain mobility in polymeric liquids and leads to extremely long relaxation times (in the order of seconds or even days as compared with picoseconds for simple liquids).The transition from a liquid to an amorphous solid is known as the glass transition. Approaching the glass transition also has a drastic effect on the relaxation times. The relaxation time of a statistical segment, the basic unit of a chain, can increase by orders of magnitude by only a small temperature change. As with entanglements this can also lead to extremely long relaxation times. The effect of the glass transition is very important even far above the transition: the monomer mobility in the melt, which is one of the most crucial parameters in all theories, depends critically on the distance from the glass transition. Thus, in order to understand the behaviour of molten polymers, it is essential to understand both entanglements and glass transition phenomena.The tube theory describing the linear rheology of linear monodisperse polymers is well-established but this system is highly idealized and therefore of limited use in industrial applications. There the processes are strongly non-linear, and include mixtures of different molecular weights and more importantly blends of different polymers. It is this situation of mixtures of two different polymers that is much less understood theoretically. Both components are susceptible in a different way to the glass transition and to entanglements effects. The aim of the project is to develop new theoretical understanding of the linear rheology of such a polymer blend. This is carried out by using massive state-of-the-art computer simulations to study the simplest model for a polymer blends covering a wide range of chain lengths, chain diameter and densities, and developing smart analysing tools relevant for supporting the development of the theory. After linear regime is understood, we then plan to investigate the effect of flow on glass transition and entanglements in polymer blends.

每个人都被聚合材料包围着——没有它们，现代生活是不可能的。典型的高分子材料由两种或两种以上不同的聚合物组成。由于混合有许多自由度，原则上，这允许材料设计师根据自己的需要调整材料属性。因此，这些材料背后的物理知识是非常需要的。典型聚合物熔体的力学性能和流动性能主要受两种现象的影响：缠结和玻璃效应。缠结理论试图描述长聚合物链不能相互穿过的事实。这一事实严重降低了聚合物液体中的链迁移率，并导致极长的弛豫时间（与简单液体的皮秒相比，在几秒钟甚至几天的顺序中）。从液体到无定形固体的转变称为玻璃化转变。接近玻璃化转变对弛豫时间也有很大的影响。链的基本单位——统计段的松弛时间，只要有一个小的温度变化，就能增加几个数量级。与纠缠一样，这也会导致极长的松弛时间。玻璃化转变的影响非常重要，甚至远高于玻璃化转变：单体在熔体中的迁移率是所有理论中最重要的参数之一，关键取决于与玻璃化转变的距离。因此，为了理解熔融聚合物的行为，必须理解纠缠和玻璃化转变现象。描述线性单分散聚合物的线性流变性的管理论是建立的，但该系统是高度理想化的，因此在工业应用中的应用有限。这些过程是强烈非线性的，包括不同分子量的混合物，更重要的是不同聚合物的共混。这种两种不同聚合物的混合物的情况在理论上还不太清楚。这两种成分都以不同的方式易受玻璃化转变和纠缠效应的影响。该项目的目的是发展这种聚合物共混物的线性流变学的新的理论认识。这是通过使用大量最先进的计算机模拟来研究聚合物共混物的最简单模型来实现的，该模型涵盖了广泛的链长、链直径和密度，并开发了与支持理论发展相关的智能分析工具。在了解了线性体系之后，我们计划研究流动对聚合物共混物中玻璃化转变和缠结的影响。