# Modeling induction period of polymer crystallization

## TL;DR

This paper develops a theoretical model to understand the conditions under which spinodal decomposition occurs during the induction period of polymer crystallization, emphasizing the role of chain stiffness and nematic interactions.

## Contribution

It introduces a Ginzburg-Landau model incorporating density and orientation, linking chain stiffness to effective attraction and spinodal decomposition in polymer melts.

## Key findings

- Spinodal decomposition is favored in stiff polymer chains.
- Nematic interactions effectively act as attractions.
- Model explains experimental observations of phase separation.

## Abstract

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 decomposion especially for stiff polymer chain case.