Synthesis and Characterization of MPEG-b-PDPA Amphiphilic Block Copolymer via Atom Transfer Radical Polymerization and Its pH-Dependent Micellar Behavior

摘要

Block copolymer micelles are generally formed via the self-assembly of amphiphilic block copolymers in an aqueous medium.The hydrophilic and hydrophobic blocks form shell and core micelles,respectively.The block copolymers of methoxy poly(ethylene glycol) (MPEG)-b-poly(2-diisopropylamino)ethyl methacrylate (PDPA) were synthesized via atom transfer radical polymerization,with the macroinitiator synthesized by the coupling of 2-bromoisobutyryl bromide with MPEG in the presence of a trietbyl amine base catalyst.The atom transfer radical polymerization of 2-diisopropylamino)ethyl methacrylate was performed in conjunction with an N,N,N',N",N"-pentam-ethyl-diethylenetriamine/copper bromide catalyst system,in DMF,at 70 °C.The pH induced micellization/demicel-lization was studied using fluorescence,with a pyrene probe.Furthermore,the pH dependent micellization was confirmed using the microviscosity method,with a dipyme fluorescence probe.The pH dependant micelle size distribution was studied using dynamic light scattering.The characterization of the synthesized polymers was established using gel permeation chromatography and from the ~1H-nuclear magnetic resonance spectroscopy.