Boron-rich cluster templates for the facile synthesis of 3-dimensional polymer materials

• Joseph Mild, Biochemistry, University of Delaware

• Marco Messina, Chemistry & Biochemistry, University of Delaware

Fundamental studies detailing the effects of minor chemical modifications on 1-dimensional (1D) linear polymers are abundant and have paved the way for significant technological advancements leading to their ubiquitous use in materials such as plastics, rubber products, and in formulations for biologic stabilization. However, similar fundamental studies exploring 3D polymer materials, such as star polymers, lag far behind. Star polymers consist of three or more polymers emanating from a central core and asymmetric derivatives, in which at least one of the polymer chains is of a different molecular composition, are known as miktoarm star polymers. Studies to date have unearthed many distinct properties of star polymers over linear derivatives such as altered solution viscosity, enhanced stimuli responsiveness, and modified thermal properties. However, it remains challenging to synthesize well-defined star polymer architectures in a way that would enable rapid diversification to generate large libraries of unique 3D materials with distinct properties. Our group aims to tackle this challenge through the introduction of well-defined and easily tunable core scaffolds based on boron-rich clusters that would enable the rapid synthesis and diversification of both miktoarm and star polymers. Boron clusters are highly tunable as their vertices are easily functionalized using synthetic methods that parallel those of classical organic molecules and synthetic methods enabling vertex differentiation are well-known. Herein, we report ongoing work developing miktoarm core template scaffolds based on carborane (C₂B₁₀H₁₂). We used reported protocols to synthesize vertex-differentiated carborane derivatives where the B(9)-position was modified with an alkyne group. Such intermediates pave way for further modification with polymer initiating sites at different vertices. This work contributes to our long-term goals of using boron-rich core scaffolds to develop libraries of star/miktoarm polymer materials to be deployed as stabilizers for antibody-based therapeutics, vaccines, and mammalian cell lines.