Synthesis and self-assembly of amphiphilic brush-dendritic-linear poly[poly(ethylene glycol) methyl ether methacrylate]-b-polyamidoamine-b- poly(ε-caprolactone) copolymers

A series of novel amphiphilic brush-dendritic-linear poly[poly(ethylene glycol) methyl ether methacrylate]-b-polyamidoamine-b-poly(ε-caprolactone) copolymers (PPEGMEMA-b-D _m-b-PCL) (m = 1, 2, and 3: the generation number of dendron) were synthesized by the combination techniques of click chemistry, atom transfer radical polymerization (ATRP), and ring-opening polymerization (ROP). The brush-dendritic copolymers bearing hydrophilic brush PPEGMEMA and hydrophobic dendron polyamidoamine protected by the tert-butoxycarbonyl (Boc) groups [D _m-(Boc) 2m (m = 1, 2, and 3)] were for the first time prepared by ATRP of poly(ethylene glycol) methyl ether methacrylate monomer (PEGMEMA) initiated with the dendron initiator, which was prepared from 2'-azidoethyl-2-bromoisobutyrate (AEBIB) and D _m-(Boc) 2m terminated with a clickable alkyne by click chemistry. Then, the brush-dendritic copolymers with primary amine groups (PPEGMEMA-b-D _m) were obtained from the removal of the protected Boc groups of the brush-dendritic copolymers in the presence of trifluoroacetic acid. The brush-dendritic-linear PPEGMEMA-b-D _m-b-PCL copolymers were synthesized from ROP of ε-caprolactone monomer using PPEGMEMA-b-D _m as the macroinitiators and stannous octoate as catalyst in toluene at 130 °C. To the best of our knowledge, this is the first report that integrates hydrophilic brush polymer PPEGMEMA with hydrophobic polyamidoamine (PAMAM) dendron and PCL to form amphiphilic brush-dendritic-linear copolymers. The amphiphilic brush-dendritic-linear copolymers can self-assemble into spherical micellar structures in aqueous solution.