Materials Physics Center, Paseo Manuel de Lardizabel 5 20018 San Sebastian, Spain.
J Phys Condens Matter. 2014 Apr 16;26(15):153101. doi: 10.1088/0953-8984/26/15/153101. Epub 2014 Mar 27.
The fate of matter when decreasing the temperature at constant pressure is that of passing from gas to liquid and, subsequently, from liquid to crystal. However, a class of materials can exist in an amorphous phase below the melting temperature. On cooling such materials, a glass is formed; that is, a material with the rigidity of a solid but exhibiting no long-range order. The study of the thermodynamics and dynamics of glass-forming systems is the subject of continuous research. Within the wide variety of glass formers, an important sub-class is represented by glass forming polymers. The presence of chain connectivity and, in some cases, conformational disorder are unfavourable factors from the point of view of crystallization. Furthermore, many of them, such as amorphous thermoplastics, thermosets and rubbers, are widely employed in many applications. In this review, the peculiarities of the thermodynamics and dynamics of glass-forming polymers are discussed, with particular emphasis on those topics currently the subject of debate. In particular, the following aspects will be reviewed in the present work: (i) the connection between the pronounced slowing down of glassy dynamics on cooling towards the glass transition temperature (Tg) and the thermodynamics; and, (ii) the fate of the dynamics and thermodynamics below Tg. Both aspects are reviewed in light of the possible presence of a singularity at a finite temperature with diverging relaxation time and zero configurational entropy. In this context, the specificity of glass-forming polymers is emphasized.
当在恒定压力下降低温度时，物质的命运是从气体到液体，然后从液体到晶体。然而，有一类材料可以在低于熔点的非晶相中存在。在冷却这些材料时，会形成玻璃；也就是说，形成一种具有固体刚性但没有长程有序的材料。玻璃形成系统的热力学和动力学的研究是一个持续研究的课题。在各种各样的玻璃形成体中，玻璃形成聚合物是一个重要的亚类。从结晶的角度来看，链连接的存在以及在某些情况下构象无序是不利的因素。此外，其中许多物质，如无定形热塑性塑料、热固性塑料和橡胶，在许多应用中得到了广泛的应用。在这篇综述中，讨论了玻璃形成聚合物的热力学和动力学的特性，特别强调了目前正在讨论的那些主题。特别是，在目前的工作中，将回顾以下方面：（i）在冷却到玻璃化转变温度（Tg）时，玻璃态动力学明显减慢与热力学之间的关系；以及，（ii）Tg 以下动力学和热力学的命运。这两个方面都根据在有限温度下存在具有发散弛豫时间和零构象熵的奇点的可能性进行了回顾。在这方面，强调了玻璃形成聚合物的特异性。
