Precision-Engineered Silane Distribution in Polyolefins Governs Cross-Linking Kinetics

Moisture silane cross-linking has been widely used to cross-link polyethylene. Traditionally, silane groups are introduced into polymer chains through two routes: copolymerizing ethylene with a silane comonomer such as vinyl trimethoxysilane (VTMS) via high-pressure radical polymerization, and grafting VTMS onto the polymer chain through peroxide-initiated radical reactions. However, the inability to control the silane distribution in these processes complicates studies of the dependent cross-linking behavior. In this study, we developed a controlled strategy for synthesizing silane copolymers with tunable silane distributions using ring-opening metathesis polymerization (ROMP) to copolymerize cyclooctene (COE) and silane functionalized COE. By changing the feeding sequence, 6 silane copolymers with different silane distributions were successfully synthesized and characterized. Gelation time analysis revealed that a uniform silane distribution greatly enhances cross-linking efficiency, while centralized or gradient distributions lead to delayed gelation due to silane aggregation and reduced cross-link density. Monte Carlo simulations further elucidated that a homogeneous distribution facilitates superior network connectivity and a faster percolation threshold, whereas localized distributions generate abundant isolated cross-links, thereby retarding the gelation process. This work generates new insights into the relationship between silane distribution and polymer properties, offering a robust platform for designing cross-linked polyolefins with enhanced cross-linking efficiency and tailored functionality.