Cyclic polymers: Advances in their synthesis, properties, and biomedical applications

Abstract

Since the time first synthetic macrocycles were observed as academic curiosities, great advances have been made. Thanks to the development of controlled polymerization processes, new catalytic systems and characterization techniques during the last decades, well-defined cyclic polymers are now readily accessible. This further permits the determination of their unique set of properties, mainly due to their lack of chain ends, and their use for industrial applications can now be foreshadowed. This review aims to give an overview on the recent progresses in the field of ring polymers to this day. The current state of the art of the preparation of cyclic polymers, the challenges related to it such as the purification of the samples and the scalability of the synthetic processes, the properties arising from the cyclic topology and the potential use of cyclobased polymers for biomedical applications are as many topics covered in this review.

Bioactive Synthetic Polymers

“…More recent developments address these challenges, permitting access to high purity cyclic polymers. [130,131] Cyclic polymers represent a unique opportunity to directly compare against linear analogs and may be a critical first step in understanding the effect of architectures and solvated conformations on bioactivity. In this vein, it is hoped that more studies pertaining to cyclic bioactive polymers will be performed in the future.…”

Double hydrophilic copolymers – synthetic approaches, architectural variety, and current application fields

“…However, they exhibit unique properties due to their lack of end-groups or reduced hydrodynamic radii, and developments in their synthesis have led to increased interest in these architectures. 109,110 Z. Ge et al synthesised linear α,ω-heterodifunctional poly(2-(2-methoxy-ethoxy)-ethyl methacrylate)- block -poly(oligo(ethylene glycol)methyl ether methacrylate), alkenyl-PMEO 2 MA- b -POEGMA-N 3 block copolymers via successive ATRP and end-group functionalisation, which form micelles at 40 °C in water. This leads to the spatial separation of the alkenyl and azide moieties, and under suitable conditions for click chemistry only released unimers will react intramolecularly.…”

Mechanism of Spatial and Temporal Control in Precision Cyclic Vinyl Polymer Synthesis by Lewis Pair Polymerization

“…This excitement is partly due to availability of more diverse classes of cyclic polymers made possible by emerging methodologies, such as zwitterionic ring‐opening polymerization, [10–14] ring‐expansion polymerization, [15–21] Lewis pair polymerization (LPP), [22–26] and coordinative insertion/back‐biting ring closure [27–29] . Added to this development are the advances in more traditional techniques such as unimolecular and bimolecular coupling reactions used for ring closure, most notably the click reactions [2, 30–37] . Additionally, materials properties unique to cyclic polymers (with respect to linear analogues), such as lower intrinsic viscosity ( η ), [38–42] faster crystallization kinetics, [43–45] and sometimes higher resistance to chemical [46, 47] and thermal degradation, can be exploited.…”

“…[27][28][29] Added to this development are the advances in more traditional techniques such as unimolecular and bimolecular coupling reactions used for ring closure, most notably the click reactions. [2,[30][31][32][33][34][35][36][37] Additionally, materials properties unique to cyclic polymers (with respect to linear analogues), such as lower intrinsic viscosity (η), [38][39][40][41][42] faster crystallization kinetics, [43][44][45] and sometimes higher resistance to chemical [46,47] and thermal degradation, can be exploited. Perhaps most intriguing is the role of cyclic block copolymers (BCPs) in self-assembly where the dynamics of phase segregation differ from their linear counterparts in their degree of entanglement and degrees of rotational and translational freedom.…”