Adjusting the length of supramolecular polymer bottlebrushes by top-down approaches.

Tobias Klein,Ivo Nischang,Franka V Gruschwitz,Johannes C Brendel,Maren T Kuchenbrod,Stephanie Hoeppener

doi:10.3762/bjoc.17.175

Tobias Klein, Ivo Nischang + Show 4 more

Open Access

https://doi.org/10.3762/bjoc.17.175

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Abstract

Controlling the length of one-dimensional (1D) polymer nanostructures remains a key challenge on the way toward the applications of these structures. Here, we demonstrate that top-down processing facilitates a straightforward adjustment of the length of polyethylene oxide (PEO)-based supramolecular polymer bottlebrushes (SPBs) in aqueous solutions. These cylindrical structures self-assemble via directional hydrogen bonds formed by benzenetrisurea (BTU) or benzenetrispeptide (BTP) motifs located within the hydrophobic core of the fiber. A slow transition from different organic solvents to water leads first to the formation of µm-long fibers, which can subsequently be fragmented by ultrasonication or dual asymmetric centrifugation. The latter allows for a better adjustment of applied shear stresses, and thus enables access to differently sized fragments depending on time and rotation rate. Extended sonication and scission analysis further allowed an estimation of tensile strengths of around 16 MPa for both the BTU and BTP systems. In combination with the high kinetic stability of these SPBs, the applied top-down methods represent an easily implementable technique toward 1D polymer nanostructures with an adjustable length in the range of interest for perspective biomedical applications.

Highlights

Cylindrical polymer nanostructures in solution have received increasing attention during the last two decades, related to the high surface-to-volume ratio, which is attractive for targeted carrier materials in biomedical applications
We demonstrate that top-down processing facilitates a straightforward adjustment of the length of polyethylene oxide (PEO)-based supramolecular polymer bottlebrushes (SPBs) in aqueous solutions
We recently reported the self-assembly of polyethylene oxide (PEO) polymers into cylindrical nanostructures, called supramolecular polymer bottlebrushes (SPBs), based on the end group modification with hydrogen bond forming benzenetrisurea (BTU) and benzenetrispeptide (BTP) motifs [18,19,20]

Summary

Introduction

Cylindrical polymer nanostructures in solution have received increasing attention during the last two decades, related to the high surface-to-volume ratio, which is attractive for targeted carrier materials in biomedical applications. This comparably mild treatment already caused a significant fragmentation of the μm-long fibers, resulting in structures of 50–200 nm length according to the cryoTEM images after 10 min of treatment (Figure 2).

Results

Conclusion