Catalytic upcycling of polyethylene into higher-value products requires catalysts capable of operating on real, disperse polymer feedstocks, yet how polymer chains and their branch points engage a catalyst surface at the molecular level remains poorly understood. This dissertation uses dynamic nuclear polarization (DNP)-enhanced solid-state NMR to develop an atomic-level picture of how polyethylene interacts with fluorinated alumina, connecting these surface interactions to the kinetics of acid-catalyzed cracking.

DNP-enhanced 13C{27Al} TRAPDOR NMR was used to probe how surface fluorination affects the adsorption of 13C-labeled poly(ethylene-rand-1-dodecene) and branched alkane model compounds on γ-Al2O3. Short-chain branches did not disrupt adsorption, but fluorination shifted adsorbed chains toward a flatter, more fully surface-bound "train" conformation despite a 0.2 Å increase in effective C-Al contact distance. In branched alkanes labeled separately at the methine and methyl, the methine remained in near-continuous contact with the surface, closer than the methyl, indicating that branch points stay accessible for acid-catalyzed scission even as branch arms compete for the surface.

19F and 1H NMR were used to track fluorine site populations across a range of fluorine loadings on alumina, and terminal Al-F sites emerged as most strongly correlated with Brønsted acid site density. C-C scission activity rose more steeply with terminal and doubly bridging Al-F populations than with triply bridging sites, pointing to a specific, minority subpopulation of fluorine environments responsible for the enhanced cracking activity. Time-resolved kinetics across polyethylenes of varying methyl branch density were benchmarked against linear and branched C30 model alkanes, triacontane and squalane, whose initial turnover frequencies reflect the greater stability of tertiary over secondary carbonium ions. Polyethylene reactivity, however, did not scale with tertiary carbon content in the same way, instead following a volcano-shaped trend with branch density, pointing to melt-state segmental mobility, rather than intrinsic carbonium-ion chemistry, as the ultimate control on reactivity in a macromolecule.

Together, these results show that fluorination reshapes both how polyethylene sits on an alumina surface and which surface sites govern its scission, while branch architecture governs reactivity through chain dynamics as much as through local bond chemistry.