Stereospecific Cyclic Poly(methyl methacrylate) and Its Topology-Guided Hierarchically Controlled Supramolecular Assemblies

In this study, the stereocomplexation between a novel stereospecific cyclic vinyl polymer, that is, cyclic syndiotactic poly(methyl methacrylate) (st‐PMMA), with the complementary linear isotactic (it‐) PMMA was investigated. Surprising new insight into the effects of the topology (i.e., end groups), size, and tacticity of the assembling components on stereocomplex formation was obtained. Characterization of the stereocomplexes revealed that the self‐assembly of cyclic st‐PMMAs and linear it‐PMMAs resulted in the formation of an unprecedented “polypseudorotaxane‐type” supramolecular assembly. This stereocomplex exhibited remarkably different physical properties as compared to the conventional PMMA triple‐helix stereocomplex as a result of the restricted topology imposed by the cyclic st‐PMMA assembling component. Hierarchy of controls: A cyclic syndiotactic poly(methyl methacrylate) (c‐st‐PMMA, blue in the picture) was synthesized with simultaneous control over molecular weight, tacticity, and topology. This meticulous microstructural control made the c‐st‐PMMA able to undergo stereocomplexation with complementary linear isotactic (l‐it‐) PMMA (red) to form an unprecedented supramolecular assembly with a distinct crystallization mode.