Abstract
The self-assembly of amphiphilic bottlebrush block copolymers (BCPs), featuring backbones densely grafted with two types of side chains, is less well understood compared to linear BCPs. In particular, the solution self-assembly of tapered bottlebrush BCPs—cone-shaped BCPs with hydrophilic or hydrophobic tips—remains unexplored. This study investigates eight tapered and four cylindrical bottlebrush BCPs with varied ratios of hydrophobic polystyrene (PS) and hydrophilic poly(acrylic acid) (PAA) side chains, synthesized via sequential addition of macromonomers using ring-opening metathesis polymerization (SAM-ROMP). Self-assembled nanostructures formed in water were analyzed using cryogenic transmission electron microscopy, small-angle neutron scattering, and dynamic light scattering. Most BCPs generated multiple nanostructures with surface protrusions, including spherical micelles, cylindrical micelles, and vesicles, alongside transitional forms like ellipsoids and semi-vesicles. Coarse-grained molecular dynamics simulations supported the experimental findings, which revealed two distinct self-assembly pathways. The first involved micelle fusion, producing elliptical and cylindrical aggregates, sometimes forming Y-junctions. The second pathway featured micelle maturation into semivesicles, which developed into vesicles or large compound vesicles. This work provides the first experimental evidence of vesicle formation via semivesicles in bottlebrush BCPs and demonstrates the significant influence of cone directionality on self-assembly behavior in these cone-shaped polymeric amphiphiles.
| Original language | English |
|---|---|
| Article number | e202500771 |
| Journal | Angewandte Chemie - International Edition |
| Volume | 64 |
| Issue number | 23 |
| DOIs | |
| State | Published - Jun 2 2025 |
Funding
This work was supported by a joint grant from the US National Science Foundation (DMR‐2104602) and the US‐Israel Binational Science Foundation (NSF‐BSF 2020715). The authors thank Prof Rana Ashkar for helpful discussions and Daniela Samaniego Gonzalez for assistance with running SANS experiments, as well as the team at the BIO‐SANS beamline. The authors thank the Virginia Tech Mass Spectrometry Research Incubator for high‐resolution mass spectrometry analysis and the Virginia Tech Department of Chemistry Analytical Facilities for NMR usage. A portion of this research used resources at the High Flux Isotope Reactor and the Spallation Neutron Source, a DOE Office of Science User Facility operated by the Oak Ridge National Laboratory. The beam time was allocated to BioSANS on proposal number IPTS‐31356.1 and EQ‐SANS on 25165.1. Modeling and simulations were conducted as part of a user project at the Center for Nanophase Materials Sciences (CNMS), which is a US Department of Energy, Office of Science User Facility at Oak Ridge National Laboratory. This research used resources of the Oak Ridge Leadership Computing Facility at the Oak Ridge National Laboratory, which is supported by the Office of Science of the U.S. Department of Energy under Contract No. DE‐AC05‐00OR22725. The authors are grateful for the generous support from the Guzik Foundation to BGU's cryo‐electron microscopy unit. This work was supported by a joint grant from the US National Science Foundation (DMR-2104602) and the US-Israel Binational Science Foundation (NSF-BSF 2020715). The authors thank Prof Rana Ashkar for helpful discussions and Daniela Samaniego Gonzalez for assistance with running SANS experiments, as well as the team at the BIO-SANS beamline. The authors thank the Virginia Tech Mass Spectrometry Research Incubator for high-resolution mass spectrometry analysis and the Virginia Tech Department of Chemistry Analytical Facilities for NMR usage. A portion of this research used resources at the High Flux Isotope Reactor and the Spallation Neutron Source, a DOE Office of Science User Facility operated by the Oak Ridge National Laboratory. The beam time was allocated to BioSANS on proposal number IPTS-31356.1 and EQ-SANS on 25165.1. Modeling and simulations were conducted as part of a user project at the Center for Nanophase Materials Sciences (CNMS), which is a US Department of Energy, Office of Science User Facility at Oak Ridge National Laboratory. This research used resources of the Oak Ridge Leadership Computing Facility at the Oak Ridge National Laboratory, which is supported by the Office of Science of the U.S. Department of Energy under Contract No. DE-AC05-00OR22725. The authors are grateful for the generous support from the Guzik Foundation to BGU's cryo-electron microscopy unit.
Keywords
- Atom-transfer radical polymerization
- Cryo-electron tomography
- Grubbs third generation catalyst
- Semi-vesicles
- Size exclusion chromatography with multi-angle light scattering