Synthesis and self-assembly of well-defined polymer brushes with high grafting density of hydrophobic poly(ε-caprolactone) and hydrophilic poly(2-(dimethylamino)ethyl methacrylate) side chains

A novel amphiphilic polymer brush consisting of alternating poly(ε-caprolactone) (PCL) and poly(2-(dimethylamino)ethyl methacrylate) (PDMAEMA) side chains was synthesized via the combination of two controlled polymerization methods, ring-opening metathesis polymerization (ROMP) and atom transfer radical polymerization (ATRP) with good control over the polymerization processes. ROMP of macromonomer norbornene-graft-poly(ε-caprolactone)/Br (PCL-NBE-Br) was first carried out to convert into a macroinitiator poly(norbornene)-graft-poly(ε-caprolactone)/Br via "grafting through" technique, and then ATRP of DMAEMA initiated by the macroinitiator was performed to generate the densely grafted polymer brushes via "grafting from" technique. Thus, the well-defined polymer brushes with two different grafts high densely distributed on the same unit along the backbone were obtained by aforementioned strategy. The molecular weights of the polymer brushes were estimated by gel permeation chromatography and 1H NMR measurements. The self-assembly behavior and the micellar characteristics of the polymer brushes in selective solvent were investigated by DLS and TEM. The TEM image showed spherical micelles with clew or strawberry-like morphology.