Manipulating Crystallization and Packing Structure in Linear Low‐Density Polyethylene and Its Cast Film Through Ethylene‐Octene Copolymers: Role of Chain Architecture

ABSTRACT Blending is a key strategy for modulating the structure of polyolefins. This study systematically investigates how the distinct chain architectures of ethylene‐octene random copolymers (ORC) and ethylene‐octene block copolymers (OBC) influence the crystallization, microstructure, and macroscopic properties of linear low‐density polyethylene (LLDPE) blends and their cast films. Through a comprehensive analysis using DSC, SAXS, SEM, and mechanical and optical testing, it was demonstrated that the block architecture of OBC was found to act as an effective nucleating agent, promoting the formation of larger, well‐ordered lamellar structures. This resulted in a synergistic enhancement of mechanical performance in the cast films, significantly increasing both tensile strength and elongation at break. Conversely, the random architecture of ORC refined the crystalline morphology by disrupting spherulitic growth. This markedly improved the films' optical properties, leading to substantially reduced haze and enhanced transparency. These findings reveal a clear structure–property relationship, establishing that OBC is an ideal modifier for mechanical reinforcement, whereas ORC is superior for enhancing optical clarity. This work provides a strategic guide for tailoring LLDPE film performance by selecting modifiers with specific chain architectures.