在经典概念中，亚稳态相应于一个局部的自由能极小值，它最终会通过一个活化过程弛豫到稳定的平衡态，一个整体上的自由能极小值。这一过程不同于非稳态的无位垒弛豫，后者是自发进行的。作为一个亚稳态，它的寿命应长于测量的时间尺度。这在实际上取决于实验设备和测量者的耐性。在亚稳态的经典概念中假设体系都是足够大的，因此不须考虑相尺寸或其它动力学效应对体系的影响。一般来说，与小分子相比，高分子进入亚稳态要容易得多。具有多重微结构层次的聚合物体系可因小的相尺寸、组成、外场或其它因素而呈现亚稳态。本文将着重于亚稳态的概念和具有两个有序结构时聚合物相转变过程中亚稳态观测，这些结构间的相稳定性关系是通过相尺寸，也就是片晶厚度来讨论的。有关亚稳态和亚稳性的概念不只对科学地理解高分子凝聚态物理是重要的，在材料的发展和应用中也是十分有用的 In the classical concept, metastability corresponds to a local free energy minimum, which eventually relaxes to a stable equilibrium through an activation process, a global free energy minimum. This process is different from the unsteady barrier-free relaxation, the latter spontaneously. As a metastable state, its life expectancy should be longer than the time scale of the measurement. This actually depends on the resistance of the experimental equipment and the measurer. It is assumed in the classical concept of metastable states that the system is large enough to ignore the effect of phase size or other kinetic effects on the system. In general, polymers are much easier to metastable than small molecules. Polymeric systems with multiple microstructural levels can be metastable due to small phase size, composition, outfield or other factors. This paper will focus on the concept of metastability and the metastable state during polymer phase transitions with two ordered structures. The phase stability relationships between these structures are discussed by the phase size, ie, the lamella thickness. The notion of metastability and metastability is not only important for the scientific understanding of polymeric condensed matter physics but is also useful in the development and application of materials