Synthesis and Self-Assembly of New Poly(ethylene glycol)-block-poly(ester-sulfide) Dendrimers

The design and synthesis of novel copolymers which consist of a linear methoxypoly(ethylene glycol) block and a dendrimeric poly(ester-sulfide) block with potential applications in drug delivery are described. The copolymers bear hydroxyl or alkene functional groups and were prepared via a divergent approach using readily available methoxypoly(ethylene glycol) (mPEG), 4-pentenoyl chloride and 3-mercapto-1,2-propanediol as building blocks. One copolymer (G3.5) with alkene chain ends was functionalized with N-acetyl-L-cysteine. The compounds prepared in this work were characterized by NMR spectroscopy and MALDI-TOF. In the preparation of these dendrimers no repetitive protection-deprotection cycles were necessary, and the purification steps consisted of only washing the reaction mixture with aqueous solutions and precipitation of the product in diethyl ether, allowing easy access to these polymers. Micelle formation for polymers of generations 3.0 and 3.5 was investigated by encapsulation of the fluorescent probe pyrene. Micelle size for the above generations was determined by dynamic light scattering.