# The Preparation of Cyclic Binary Block Polymer Using Bimolecular Homodifunctional Coupling Reaction and Characterization of Its Performance as a Drug Carrier

## TL;DR

This paper explores the synthesis of cyclic block polymers and their potential as drug carriers, highlighting how their unique structure affects drug delivery performance.

## Contribution

The study introduces a method to synthesize cyclic amphiphilic block polymers and evaluates their drug delivery properties.

## Key findings

- Cyclization of linear polymer precursors is successful despite trace linear by-products.
- Cyclic polymers show no significant improvement in micelle stability or drug loading compared to linear polymers.
- Cyclic polymers still exhibit better cellular uptake ability than linear polymers.

## Abstract

There is relatively little research on cyclic amphiphilic block polymers, having both hydrophilic and hydrophobic segments placed in the ring and thus resulting in a higher degree of topological restriction, as drug vehicles. Cyclic amphiphilic binary block polymer is synthesized by the click coupling reaction of bimolecular homodifunctional precursors. The results indicate that cyclization between linear polymer precursors is successful if the trace linear by-products generated are ignored, which also suggests that the small molecule bifunctional terminating agent applied in traditional bimolecular homodifunctional ring-closure process can be extended to large molecule. Moreover, the study on the self-assembly behavior of polymers shows that, compared with linear counterparts, the stability and drug loading capacity of micelles based on the resultant cyclic polymer are not significantly improved due to the influence of topological structure and linear impurities. Nevertheless, drug loaded micelles formed by the obtained cyclic polymers still exhibit superior cellular uptake ability. It can be seen that topological effects do play an irreplaceable role in the application performance of polymers. Therefore, the construction and synthesis of cyclic and its derivative polymers with moderate topological confinement and high purity may be a key direction for future exploration of polymer drug delivery carriers.