Raquel Lopez Rio De Castro: Topology-controlled self-assembly of amphiphilic block copolymers

The topology of a polymer strongly influences its self-assembly into complex nanostructures however a clear mechanistic understanding of the relationship between polymer topology and self-assembly has not yet been developed. In this work, we use atomistic molecular dynamics simulations to provide a nanoscale picture of the self-assembly of three poly(ethylene oxide)-poly(methyl acrylate) block copolymers with different topologies into micelles. We find that the topology affects the ability of the micelle to form a compact hydrophobic core, which directly affects its stability. Also, we apply unsupervised machine learning techniques to show that the topology of a polymer affects its ability to take a conformation in response to the local environment within the micelles. This work provides foundations for the rational design of polymer nanostructures based on their underlying topology

The ability of amphiphilic polymers to self-assemble into specific morphologies in solution has driven interest in their deployment for a diverse range of applications.1–4 The topology of block copolymers exerts great influence over their properties and therefore their potential applications. Ring polymers are one synthetically accessible topology that have drawn considerable attention as a result of the unique properties that they exhibit in comparison to their linear counterparts.5–13 Functional polymer nanostructures have been typically fabricated using linear polymers but significant synthetic advances in the past two decades have made ring copolymer synthesis possible. Ring polymers demonstrate distinct self-assembly behavior,9,12,13 which leads to their resultant micelles possessing markedly different properties,9 including the size and shape,14 morphology,15,16 temperature, salt tolerance,17,18 and degradation14 with respect to micelles formed from analogous linear polymers.

In drug delivery applications, the ability to control the size and stability of micellar aggregates is particularly important. The size of such micelles is one of the most critical features in determining biodistribution and the stability can be tuned to prevent premature release or to enable a controlled release of therapeutics. Ring polymers have shown great promise as potential drug and gene delivery vehicles because they often show improved drug loading and releasing capacity,19,20 greater efficacy,21–24 longer in vivo circulation times,25,26 and high cancer cell uptake25–28 as the same polymers with a linear topology.

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