To enable the surface functionalization through functional surfactants, two different surfactant molecules were synthesized as amphiphilic block copolymers containing reactive end-groups. An alkyne group was introduced for alkyne-azide “click” functionalization of the particle surface. Functionalization of the second surfactant with an orthogonally reactive succinimide group was started but then delayed due to shut down research facilities in course of the COVID-19 pandemic. Overall, this strategy successfully demonstrated the formation of striped ellipsoidal BCP particles by using tailormade surfactants, thus implementing the crucially needed expertise to further develop this approach in follow-up projects.
To enable surface functionalization through modified internal domains, reactive monomers were used for a seeded polymerization with striped ellipsoidal particles. Key to this approach is a two-step process: First, monomers selectively swell one BCP domain. Second, polymerization covalently fixates the morphology. It was found that selective swelling leads to polymer chain stretching which causes restructuring of the particles. This can be used to control the thickness of one specific domain, which creates a previously unknown internal anisotropy and translates into highly elongated particles. Based on these fundamental insights, a reactive monomer was selectively incorporated into one domain to enable spatially controlled modification via click reactions. As proof of concept, coupling of dyes was shown by UV spectroscopy and the local functionalization with ferrocene was demonstrated by energy-dispersive X-ray spectroscopy (EDX).
The simplicity and the robustness of this approach represents a unique new tool to control the lamellae thickness and aspect ratio of striped ellipsoidal particles. As a post-particle formation approach, this functionalization allows obtaining a variety of morphologies from one batch of particles. The addition of reactive functional groups through monomers lays the foundation for further functionalization that can ultimately be used to mimic cellular compartmentalization.
The results of both projects were presented at the 16th ZSIGMONDY COLLOQUIUM 2020 "Soft Colloids" in Dusseldorf, Germany and highlighted with the Best Poster Award.
Navarro, L., Klinger, D. From Striped Ellipsoids to Janus Nanoparticles: Controlling Colloid Shape, Morphology and Function via Phase Separation of Functional Polymers. 16th ZSIGMONDY COLLOQUIUM 2020 "Soft Colloids". Dusseldorf, Germany. 2020
Unfortunately, other disseminations on international congresses organized for the year 2020 were fully postponed because of the COVID-19 pandemic. This includes the American Chemical Society (ACS) meeting and the Makromolekulares Colloquium in Freiburg, Germany.
The results from the project will be published open access in two main articles regarding the swelling-induced restructuring and the seeded-polymerization (manuscripts are in preparation). In addition, a review article was published to highlight the potential of such particle-functionalization approaches:
Gruber, A., Navarro, L., Klinger, D., Reactive Precursor Particles as Synthetic Platform for the Generation of Functional Nanoparticles, Nanogels, and Microgels. Adv. Mater. Interfaces 2020, 7, 1901676.
