Dendrimer assembly via non-covalent interactions

Abstract

Dendrimers are monodisperse and highly branched macromolecules which are built around a core. The segments that combine to form a dendrimer are called dendrons. The synthesis of dendrimers can be undertaken in a manner that all dendrons are grown from the core molecule. As an alternative, dendrons can be synthesized separately and later combined with a multivalent core molecule to obtain the dendrimer. The number of multivalency of the core determines the number of segments in the dendrimer. The attachment of the dendron segments to the core unit can be via a covalent or non-covalent interaction. Non-covalent interactions based on hydrophobic effect can be exploited to yield a supramolecular dendrimer assembly. Assembly of dendrons in aqueous environment can be achieved by attachment of functional groups capable of forming host-guest complex at the focal point of the dendrons. Cyclodextrins having a hydrophobic interior cavity are capable of making supramolecular host-guest interactions with appropriate guests. A well known example is the inclusion complex of β -cyclodextrin and adamantane. Two different types of dendrons were synthesized and functionalized with β - cyclodextrin and adamantane respectively. The adamantane containing polyester dendrons were synthesized using divergent synthesis. Novel methodology involving copper catalyzed Huisgen type Click chemistry was utilized to obtain the cyclodextrin containing polyether dendrons. Self-assembly of dendrons to provide segment-block dendrimers in aqueous environment was successfully demonstrated.