Synthesis of Macro-rotaxanes via Direct Trapping of Multicyclic Poly(n-butyl acrylate) in a Cross-linked Network

Abstract

Macro-rotaxanes, in which both the linear and cyclic components are polymers, remain largely unexplored in terms of their formation and potential material applications due to the synthetic challenges associated with cyclic polymers. In this study, macro-rotaxane formation was investigated by means of the photoradical polymerization of n-butyl acrylate (BA) and a cross-linker in the presence of multicyclic poly(n-butyl acrylate) (mc-PBA). For this purpose, mc-PBA with different average numbers of cyclic units (N_ring) and cyclic unit molecular weights (M_n,ring) were synthesized via the cyclopolymerization of an α,ω-dinorbornenyl-functionalized PBA macromonomer. Subsequently, polymer networks incorporating mc-PBA were prepared and the trapping efficiency of mc-PBA within these networks was evaluated. The fraction of mc-PBA trapped within the macro-rotaxane increased with increasing N_ring and M_n,ring. Additionally, dynamic viscoelastic measurements revealed that the incorporation of mc-PBA enhanced the damping properties of the resulting PBA networks. Notably, these properties were retained even after the removal of untrapped mc-PBA by solvent washing, demonstrating that mc-PBA functioned effectively as a non-leaching additive.