Efficient synthesis of block-segmented dendrimers

Abstract

Highly branched, globular and monodisperse macromolecules are promising platforms for drug delivery. Due to these properties, evaluation of dendrimers as drug delivery agents is being actively pursued. This necessitates the development of efficient methods for dendrimer synthesis. This thesis proposes two novel methodologies that allow efficient synthesis of segment block dendrimers. The first part of this study demonstrates that ‘click reactions’ such as Huisgen cycloaddition is an effective method for combining dendrons. Synthesis of ‘segment block’ dendrimers was realized in high yield and purity utilizing a [3 + 2] cycloaddition between azide and alkyne appended dendrons. Two different types of dendrons (poly (aryl ether) and polyether) were synthesized via convergent method up to third generation. These dendrons were equipped with the necessary functional groups and click reaction was utilized for the coupling of dendrons to obtain ‘nonsymmetrical segment block dendrimers’. Effect of generation and constitution of branching units of the dendrons on the cycloaddition was probed. In the second part, attachment of different kinds of dendritic structures to a 1,3,5- trichlorotriazine based core to synthesize nonsymmetrical macromolecules was evaluated. 1,3,5-trichlorotriazine is known to have a chemoselective reactivity. As a result the degree of substitution on the molecule can be controlled by the applied temperature. We propose that segment block dendrimers can be prepared using as a 1,3,5-trichlorotriazine core molecule by taking advantage of this chemical reactivity difference.