Well-Defined Star Polymers with Mixed-Arms by Sequential Polymerization of Atom Transfer Radical Polymerization and Reverse Addition−Fragmentation Chain Transfer on a Hyperbranched Polyglycerol Core

Abstract

Mixed-arm star polymers were synthesized by atom transfer radical polymerization (ATRP) and reverse addition−fragmentation chain transfer (RAFT) sequential polymerization using the “core first” method. The synthesis consisted of three steps: (i) synthesis of a hyperbranched polyglycerol (HPG) core, (ii) ATRP with the first monomer (St, styrene), and (iii) then the polymerization with the second monomer (tert-butyl acrylate, tBA) from the core by the RAFT technique. After the hydrolysis of poly(tBA), poly(acrylic acid) (PAA) arms were obtained. In the whole process, the final products and intermediates were characterized by gel permeation chromatography (GPC), nuclear magnetic resonance spectroscopy (NMR), ultraviolet spectroscopy (UV), Fourier transform-infrared (FT-IR), and matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF MS) in detail. The arm number and arm length of polystyrene (PS) and poly(tBA) (PAA) in the star polymers were derived from GPC and MALDI-TOF MS ...