Kinetic mechanism of chain folding in polymer crystallization

TL;DR

This paper proposes a kinetic model for polymer chain folding during crystallization, highlighting the roles of stem formation, supercooling, and repulsive interactions, and deriving expressions for lamellar thickness and growth rate.

Contribution

It introduces a new kinetic mechanism based on stem formation and Rouse time comparison, emphasizing repulsive interactions in polymer crystallization.

Findings

Lamellar thickness inversely proportional to supercooling

Repulsive interactions influence lamellar thickening

Derived expression for growth rate as a multistage process

Abstract

I develop a kinetic mechanism to explain chain folding in polymer crystallization which is based on the competition between the formation of stems, which is due to frequent occupations of trans states along the chains in the supercooled polymer melt, and the random coil structure of the polymer chains. Setting equal the average formation time of stems of length $% d_l$ with the Rouse time of a piece of polymer of the same arc length $d_l$ yields a lower bound for the thickness of stems and bundles. The estimated lamellar thickness is inversely proportional to the supercooling. The present approach emphasizes the importance of repulsive interactions in polymer crystallization, which are expected to be responsible for the logarithmic lamellar thickening and the increase of lamellar thickness with pressure. An expression for the growth rate is derived by considering the growth as a dynamic multistage process.