tBHBMA: a novel trifunctional acrylic monomer for the convenient synthesis of PAA-g-PCL well-defined amphiphilic graft copolymer

A series of well-defined amphiphilic graft copolymers, consisting of a hydrophilic poly(acrylic acid) (PAA) backbone and hydrophobic poly( -caprolactone) (PCL) side chains, was synthesized by the combination of reversible addition-fragmentation chain transfer (RAFT) polymerization and ring-opening polymerization (ROP). A new acrylate monomer containing a ROP initiation group, tert -butyl(2-((4-hydroxybutanoyloxy)methyl)acrylate), was first prepared using tert -butyl acrylate as the starting material, and it was homopolymerized by RAFT in a controlled way to give a well-defined homopolymer bearing ROP initiation group in every repeating unit. This homopolymer directly initiated ROP of -caprolactone to provide well-defined poly( tert -butyl acrylate)- g -poly( -caprolactone) graft copolymers via the grafting-from strategy without post-polymerization functionality transformation. Finally, the hydrophobic poly( tert -butyl acrylate) backbone was selectively hydrolyzed in an acidic environment without affecting the PCL side chains to afford poly(acrylic acid)- g -poly( -caprolactone) amphiphilic graft copolymers possessing the hydrophilic PAA backbone and equally distributed hydrophobic PCL side chains. The self-assembly behavior of the obtained amphiphilic graft copolymers and pH-sensitivity of the resultant micelles were investigated by fluorescence spectroscopy, DLS, and TEM. DSC and XRD analysis showed the crystallization behavior of poly(acrylic acid)- g -poly( -caprolactone) graft copolymers. This article reports the synthesis of novel PAA- g -PCL amphiphilic graft copolymers containing a hydrophilic PAA backbone and equally distributed hydrophobic PCL side chains using new t BHBMA trifunctional acrylic monomer as the starting material.