Polystyrene macrocycles have been prepared from ATRP precursors by modification of the terminal bromide to an azide, followed by "click" cyclization with a pendant alkyne from the initiator. This route offers exceptional control over the size and polydispersity of the macrocyclic polymers, as well as providing tolerance to a number of functional groups.

Despite decades of studies devoted to the unique physical properties and potential applications of cyclic polymer topologies, their exploration has remained limited because of synthetic inefficiencies and acyclic impurities. Many recently developed synthetic techniques offer efficient routes to well-defined cyclic macromolecules to answer this need. This tutorial review aims to provide a concise overview of the most significant synthetic contributions in this field, and highlight the relative advantages and disadvantages of each approach.

Cyclic dendronized polymers represent a new class of polymers which exhibit a donut-like "toroidal" shape. Two previous unreported methods for preparing this architecture, the divergent "graft-from" and the convergent click "graft-to" approaches, are explored and the resulting products fully characterized. This route is particularly attractive because it enables production of exact linear and cyclic dendronized analogues, enabling direct comparison of their physical properties. In this preliminary work, the divergent "graft from" approach appears to lead to materials with broad PDI at high DP, whereas the "graft to" approach yields more well-defined dendronized cyclic polymers at larger DP. On the basis of reports to date, a combination of click cyclization followed by click "grafting to" provides the most versatile route for the synthesis of cyclic dendronized polymers.

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