We study the possibility of the spinodal decomposition in the induction period of the polymer crystallization. This phenomenon was first reported in an X-ray scattering experiment, and has still been controversial due to various experiments and theories that support or deny the phenomenon. In this article, we explain the condition for the spinodal decomposition to occur in polymer melts by deriving a Ginzburg-Landau model of the free energy as a functional of the density and the orientation of the segments, where we introduce the excluded volume and the nematic interactions through a combination of the random phase approximation and the transfer matrix for the polymer conformation. We show that, upon elimination of the degrees of freedom of the orientation, the nematic interaction reduces to an effective attraction whose strength increases with the stiffness of the polymer chain. Such an attraction induces spinodal decomposition especially for stiff polymer chain case.

我们研究了在聚合物结晶诱导期间旋节线分解的可能性。这种现象最早是在X射线散射实验中报道的，但由于各种支持和否认该现象的实验和理论，仍然引起争议。在本文中，我们通过推导自由能的金兹堡-兰道模型作为节段的密度和方向的函数，解释了聚合物熔体中发生旋节线分解的条件，在此我们介绍了排除体积和向列型通过无规相逼近法和聚合物构象的传递矩阵的组合进行相互作用。我们表明，消除取向的自由度后，向列相互作用减少到有效的吸引力，其强度随着聚合物链的刚度而增加。这种吸引引起旋节线分解，特别是对于刚性聚合物链的情况。