Sequential Click Approach to Polyhedral Oligomeric Silsesquioxane-Based Shape Amphiphiles

This paper reports a highly efficient and modular sequential click approach for the syntheses of shape amphiphiles based on polymer-tethered polyhedral oligomeric silsesquioxane (POSS). This approach combines both grafting-to and post-functionalization strategies. It involves the copper-catalyzed Huisgen [3 + 2] cycloaddition (CuAAC) for POSS-polymer ligation and subsequent thiol-ene addition reaction for POSS cage functionalization. Starting from a readily available POSS precursor bearing one alkyne and seven vinyl groups (VPOSS-alkyne), the CuAAC reaction is effective in ensuring the stoichiometric bonding between POSS and azide-functionalized polymers, with no need for fractionation in the purification process. The modularity was demonstrated in two representative polymer systems, hydrophobic polystyrene (PS) and hydrophilic poly(ethylene oxide) (PEO), by the synthesis of VPOSS-PS and VPOSS-PEO. The thiol-ene reaction was subsequently applied to convert all the vinyl groups on the POSS cage quantitatively into various functional groups, including carboxylic acids, hydroxyls, and alkyls, thereby introducing amphiphilicity to drive self-assembly. Such shape amphiphiles are novel model systems for the study of their self-assembly behaviors, hierarchal structure formation, and functional properties in both the solution and bulk states. Aiming to fulfill the click philosophy, the sequential click approach described here is robust and efficient for rapid construction of functional shape amphiphiles with complex structures and diverse molecular architectures.