Macromolecules, Vol.42, No.1, 104-113, 2009
Dendron-like Polypeptide/Linear Poly(ethylene oxide) Biohybrids with Both Asymmetrical and Symmetrical Topologies Synthesized via the Combination of Click Chemistry and Ring-Opening Polymerization
Dendron-like poly(gamma-benzyl-L-glutamate)/linear poly(ethylene oxide) block copolymers with both asymmetrical and symmetrical topologies (i.e., ABn type Dm-PBLG-b-PEO and BnABn type Dm-PBLG-b-PEO-b-Dm-PBLG; it = 2(m), m = 0, 1, 2, and 3; Dm are the propargyl focal point poly(amido amine) type dendrons having 2m terminal primary amine groups) were synthesized via the combination of ring-opening polymerization. (ROP) of gamma-benzyl-L-glutamate N-carboxyanhydride (BLG-NCA) and click chemistry according to the "arm-first" and "core-first" strategies. In the arm-first method, the propargyl focal point dendrons Dm having 2(m), terminal primary amine groups were first used for initiating the ROP of BLG-NCA, generating "clickable" dendron-like Dm-PBLG homopolymers having 2(m) branches, which were then click conjugated with azide-terminated PEO (PEO-N-3) to produce asymmetrical Dm-PBLG-b-PEO. In the core-first strategy, the propargyl focal point Din was first click conjugated with PEO-N-3 to generate primary amine-terminated PEO dendrons, which were further used as the macroinitiators for the ROP of BLG-NCA to produce the targeted copolymers with both asymmetrical and symmetrical topologies. Their molecular structures and physical properties were characterized in detail by FT-IR, NMR, gel permeation chromatography, differential scanning calorimetry, and wide-angle X-ray diffraction. Both spherical and wormlike micelles self-assembled from these Dm-PBLG-b-PEO copolymers in aqueous solution, and mainly the PBLG composition controlled the morphology of nanostructures.