Compared to the synthesis of polyurethane (PU) polymers, construction of well-defined polyurethane dendrimers (PUDs) is challenging owing to high reactivity of externally added or in-situ formed isocyanates leading to formation of side products. For this reason, synthesis of dendritic PUs is limited to very few reports. With a major focus of dendrimer research on the interaction of the periphery and the core, herein, we report the synthesis of a common PU dendron, which allows for late-stage variation of both the periphery and the core. The periphery can be varied simply by installing a clickable unit in the dendron and then attaching to the core and vice-versa. Thus, a common dendron allows for varying periphery and core in the final two steps. To accomplish this, protecting group free one-pot multicomponent Curtius reaction was employed to afford a robust and versatile AB2 type polyurethane dendron using commercially available simple molecules, 5-hydroxyisophthalic acid, 11-bromoundecanol, and 4-penten-1-ol. Subsequent late-stage modification of either dendrons or dendrimers via thiol-ene click reaction gave surface functionalized alternating aromatic-aliphatic PU homodendrimers to generation-three (G3). The versatility of this approach was demonstrated by bifunctional AB2 type dendritic monomer that can either undergo a thiol-ene click or attachment to the trifunctional core. Furthermore, we demonstrated the utility of this synthetic strategy by allowing two different AB2 type wedges to attach to a difunctional core, which gave three different dendrimers including a heterodendrimer or Janus dendrimer. This approach enables incorporation of functionalities at the periphery and the core that may not withstand the dendrimer growth and is applicable not only for the synthesis of PUDs but also for other dendritic macromolecules.

Thiol-ene click engineered late-stage modification: Synthesis of long chain polyurethane dendrimers

ACS Spring Meeting 2021

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.