Core Cross-Linked Amphiphilic Star-Block Copolymers With (Meth)Acrylic Acid Shells Prepared By Atom Transfer Radical Polymerization

Core cross-linked amphiphilic star-block copolymers were prepared by hydrolysis of the outer shell of star-block copolymers prepared using copper mediated atom transfer radical polymerization (ATRP). In an arm-first approach, linear poly(tert-butyl methacrylate) macroinitiators (PtBMA-Cl) were extended with styrene to yield PtBMA-b-PS-Cl and then cross-linked with divinylbenzene (DVB) in order to yield (PtBMA-b-PS)arms-PDVBcore star-block copolymers. Then, PMAA-b-PS block and (PMAA-PS)arms-PDVBcore star-block copolymers were obtained by hydrolysis of the PtBMA blocks in both linear and cross-linked copolymers, as confirmed by 1H NMR analyses. The amphiphilic character of these copolymers was confirmed by solubilisation in water. Several factors affecting the polymer aggregation and solubility such as the length, the composition of the arms and the catalyst used were studied. An acrylate analogue, that is, (PAA-b-PS)arms-PDVBcore, was also prepared for comparison purposes. Atomic force microscopy (AFM) and differential scanning calorimetry (DSC) were used to elucidate the morphology and the thermal behaviour of the star-block copolymers.