Synthesis of Deuterated Multicyclic Polystyrenes for a SANS Study to Explore the Structural Characteristics of Multicyclic Architectures in the Bulk

Cyclic polymers exhibit unique properties owing to their closed-ring topology. In contrast to monocyclic species, multicyclic polymers contain multiple covalently linked rings, which introduce additional topological constraints that markedly affect their structures. This paper reports the synthesis and structural characterization of multicyclic polystyrenes (mc-PS) and their deuterated analogues (mc-dPS) via cyclopolymerization. Using small-angle neutron scattering, mc-PS was investigated both in its neat bulk state and in blends with linear PS. Neat mc-PS showed reduced radii of gyration and strong inter-ring correlations compared to the linear and monocyclic analogs. In particular, the intramolecular excluded-volume effects were not fully screened even in the bulk phase, owing to pronounced junction-localized swelling. In linear polymer blends, ring swelling was observed when the ring size exceeded the entangled molecular weight, which increased with the number of cyclic units. This study provides an experimental platform for elucidating topology-governed structures in both neat and blended multicyclic polymer systems.