Controlling the Shape of Molecular Weight Distributions in Coordination Polymerization and Its Impact on Physical Properties

Abstract

High-density polyethylene (HDPE) is utilized in a multitude of commercial products worldwide due to its broad spectrum of physical properties and low production costs. Molecular weight and dispersity (Đ) are known to affect the tensile and rheological properties of HDPE, but little is known about the influence of the molecular weight distribution (MWD) shape on these properties. In this work, we investigate this matter through the temporal regulation of initiation in a living coordination-insertion polymerization of ethylene. This method provides precise control over the MWD shape which, in turn, offers a systematic study on the influence of MWD shape on the physical properties of HDPE. Through rheological testing, we observe a difference in complex viscosity and shear thinning with opposite MWD skew. However, tensile testing reveals that the MWD skew does not impact the strain at break, signifying the ability to influence HDPE processing without compromising material strength.