Polystyrene-Grafted Chain-Walking Polyethylene: Precision Synthesis and Multidimensional Analysis of Composition, Conformation, and Topology

Abstract Polystyrene-grafted chain-walking polyethylene graft copolymers were synthesized by grafting living polystyryl anions onto ester-functionalized chain-walking polyethylene backbones. Two complementary sample series were designed to address questions of synthetic precision and molecular heterogeneity: crude grafting products containing graft copolymer together with residual homopolymers, and purified graft copolymers with systematically varied polystyrene graft lengths of 2, 3, and 4 kg/mol. Spectroscopic analysis confirmed covalent graft formation, while quintuple-detector size-exclusion chromatography (SEC-d5) revealed increased molar mass after grafting and a transition toward compact, branched solution architectures. High-temperature solvent-gradient interaction chromatography (HT-SGIC) resolved chemical-composition heterogeneity and distinguished graft copolymer from free polystyrene and ungrafted chain-walking polyethylene; retention was governed primarily by polystyrene graft length rather than molar mass alone. Coupling interaction chromatography with SEC in a two-dimensional liquid chromatography (2D-LC) setup directly correlated composition-defined fractions with hydrodynamic size distributions. Thermal field-flow fractionation (ThFFF) provided a complementary stationary-phase-free separation and, through online light scattering, linked graft-copolymer retention to molecular compactness and topology. Together, these orthogonal methods show that controlled polystyrene grafting onto chain-walking polyethylene can be achieved, but that its precision and architectural purity can only be validated through multidimensional characterization. This work establishes a comprehensive analytical platform for correlating composition, molar mass, conformation, and topology in complex polyolefin-based graft copolymers.