Abstract
The construction of well-defined polyurethane dendrimers is challenging due to the high reactivity of externally added or in situ formed isocyanates leading to the formation of side products. With a primary focus of dendrimer research being the interaction of the periphery and the core, we report the synthesis of a common polyurethane dendron, which allows for the 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, a protecting group-free, one-pot multicomponent Curtius reaction was utilized to afford a robust and versatile AB2 type polyurethane dendron employing commercially available simple molecules: 5-hydroxyisophthalic acid, 11-bromoundecanol, and 4-penten-1-ol. Subsequent late-stage modifications of either dendrons or dendrimers via a thiol-ene click reaction gave surface-functionalized alternating aromatic-aliphatic polyurethane homodendrimers to generation-three (G3). The dendrons and the dendrimers were characterized by NMR, mass spectrometry, and FT-IR analysis. A bifunctional AB2 type dendritic monomer demonstrated this approach’s versatility that can either undergo a thiol-ene click or attachment to the core. This approach enables the incorporation of functionalities at the periphery and the core that may not withstand the dendrimer growth for the synthesis of polyurethane dendrimers and other dendritic macromolecules.
Highlights
Academic Editors: Lelia CosimbescuDendrimers are highly branched, multivalent, star-shaped polymeric macromolecules [1–4].These monodispersed dendritic polymers exhibit wide applications in the field of catalysis, sensing, molecular electronics, photonics, fluorescence, and therapeutics [5–20]
Tomalia’s first report on poly(amidoamine) (PAMAM) dendrimers in 1985, ref [21] many research groups have reported the synthesis of dendritic macromolecules using ether, ester, carbosilane, amide, and alkyne linkages [21–33]
Available 5-hydroxyisophtalic acid 1 was used as a building block to synthesize the generation one dendritic wedge
Summary
Dendrimers are highly branched, multivalent, star-shaped polymeric macromolecules [1–4]. It is inOur group reported the convergent synthesis of polyurethane sensitive to moisture and yields a single stereoselective product [76,77] For this reason, dodecyl end groups, using a exploited protection–deprotection strategy two de thiol-ene click reactions have been widely for the synthesis, functionalization, and postmodification/surface the formation of cross-linkages in app we reportmodification on a fast,of dendrimers efficient,forand protecting-group-free hyperbranched macromolecules [50,77–107]. Dodecyl end groups, using a exploited protection–deprotection strategy two de thiol-ene click reactions have been widely for the synthesis, functionalization, and postmodification/surface the formation of cross-linkages in app we reportmodification on a fast,of dendrimers efficient,forand protecting-group-free hyperbranched macromolecules [50,77–107] This powerful tool has seen little application polyurethane dendrimers to There the third usingclick the conv in the field of polyurethane chemistry.
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